Fate of the Universe, Age of the Universe, Dark Matter, and the Decaying Vacuum Energy

It is shown that in the cosmological models based on a vacuum energy decaying as a^{-2}, where a is the scale factor of the universe, the fate of the universe in regard to whether it will collapse in future or expand forever is determined not by the curvature constant k but by an effective curvature constant k_{eff}. It is argued that a closed universe with k=1 may expand forever, in other words simulate the expansion dynamics of a flat or an open universe because of the possibility that k_{eff}=0 or -1, respectively. Two such models, in one of which the vacuum does not interact with matter and in another of which it does, are studied. It is shown that the vacuum equation of state p_{vac}= -\rho_{vac} may be realized in a decaying vacuum cosmology provided the vacuum interacts wuth matter. The optical depths for gravitational lensing as a function of the matter density and other parameters in the models are calculated at a source redshift of 2. The age of the universe is discussed and shown to be compatible with the new Hipparcos lower limit of 11Gyr. The possibility that a time-varying vacuum energy may serve as dark matter is suggested.Comment: AAS LaTex, 29 pages, published in the Astrophysical Journal, 520, 45, 199

A Research of nasal methicillin resistant/sensitive Staphylococcus aureus and pharyngeal beta-haemolytic Streptococcus carriage in midwifery students in Kahramanmaras, Eastern Mediterranean Region of Turkey

Background: In the hospitals where hygienic conditions are not provided, nasal methicillin resistant/sensitive Staphylococcus aureus (MRSA/MSSA) colonization is seen in the hospital personnel and patients. Both the individuals’ themselves being MRSA/MSSA carriers and also other people around them are under risk and this bacterium leads to nasal colonization and then can propagate through contaminated hands and hospital materials.Objective: In this study, it was aimed to research MRSA/MSSA and beta-haemolytic streptococcus (BHS) carriage in the nose and throat flora of students of, School of Health.Methods: In the study, total of 160 midwifery students taking midwifery education was included in the research but 135 (84.4 %) out of 160 students were able to be reached. The nose and throat swab samples taken from students were examined through microbiological methods.Results: 14.1 % of students were nasal MSSA carrier. While there wasn't the nasal MRSA carrier among students attending the study in the 1st and 2nd class, 3.3 % (1 person) of the 3rd class students and 10.0 % (3 people) of the 4th class students were the nasal MRSA carrier. In addition, BHS carriage was determined in 1.5 % of students and there wasn't any difference between classes.Conclusions: These results indicate that midwifery students might have been contaminated with MSSA/MRSA during clinical practice. That MSSA/MRSA being an important pathogen is seen in midwifery students taking education in the birth units threatens the mother-child health. [Ethiop. J. Health Dev. 2010;24(1):57-60

Modeling and simulation of the ferroelectric based micro gyroscope: FEM analysis

Cataloged from PDF version of article.This paper presents the design and modeling of micro-electromechanical systems (MEMS) on the ternary ferroelectric compounds (PZT) based by using finite element model (FEM) simulation. The conceptual framework establishes five steps to perform the critical analysis: design a novel structure, define the failure mechanisms under the given conditions, analyze different vibrations, analyze the operation principle, and detect resonance modes. In addition, MEMS failure modes were analyzed under different scenarios and the obtained results discussed

The Fatigue Strength of AISI 430—304 Stainless Steels Welded by CO₂ Laser Beam Welding

In this study, the fatigue strength of AISI 430—304 stainless steels welded by CO₂ laser beam welding (LBW) is investigated. Laser welding experiments are carried under helium atmosphere at 2000, 2250 and 2500 W welding powers with 100 cm/min welding speed. The welding zones are examined by optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy analysis. Fatigue tests are performed using an axial fatigue test machine, and the fatigue strength is analysed drawing S−N curves and critically observing fatigue fracture surfaces of the tested samples. The experimental results indicate that mechanical properties and microstructural features are affected significantly by welding power. The fatigue strength of CO₂ laser welded samples increase due to higher deep penetration in welding zone with increasing welding power in chosen conditions. The best properties are observed with the specimens welded at 2500 W heat input and 100 cm/min welding speed.В цій роботі досліджено втомну міцність неіржавійних сталей AISI 430—304, зварених променем CO₂-лазера. Експерименти з лазерного зварювання виконувалися в атмосфері гелію за потужности зварювання у 2000, 2250 і 2500 Вт із швидкістю зварювання у 100 см/хв. Зони зварювання досліджувалися методами оптичної мікроскопії, сканівної електронної мікроскопії та енергодисперсійної спектроскопії. Дослідження на втому виконувалися з використанням машини для випробувань на вісну втому, а втомна міцність аналізувалася шляхом побудови S−N-кривих та критичного спостереження поверхонь втомного руйнування досліджених зразків. Експериментальні результати показують, що механічні властивості та мікроструктурні особливості значно залежать від потужности зварювання. Втомна міцність зразків, зварених CO₂-лазером, зростає завдяки збільшенню глибини проникнення в зоні зварювання зі збільшенням потужности зварювання за обраних умов. Найкращі властивості спостерігалися у зразків, зварених за підведеної теплоти при 2500 Вт та швидкости зварювання у 100 см/хв.В данной работе исследована усталостная прочность нержавеющих сталей AISI 430—304, сваренных лучом CO₂-лазера. Эксперименты по лазерной сварке выполнялись в атмосфере гелия при мощностях сварки 2000, 2250 и 2500 Вт и скорости сварки 100 см/мин. Зоны сварки исследовались методами оптической микроскопии, сканирующей электронной микроскопии и энергодисперсионной спектроскопии. Испытания на усталость производились с использованием машины для испытаний на осевую усталость, а усталостная прочность анализировалась путём построения S−N-кривых и критического наблюдения поверхностей усталостного разрушения исследованных образцов. Экспериментальные результаты показывают, что механические свойства и микроструктурные особенности значительно зависят от мощности сварки. Усталостная прочность образцов, сваренных CO₂-лазером, возрастает благодаря увеличению глубины проникновения в зоне сварки с увеличением мощности сварки при выбранных условиях. Наилучшие свойства наблюдались у образцов, сваренных при подводимой теплоте с 2500 Вт и скорости сварки 100 см/мин

Thermodynamics of Decaying Vacuum Cosmologies

The thermodynamic behavior of vacuum decaying cosmologies is investigated within a manifestly covariant formulation. Such a process corresponds to a continuous irreversible energy flow from the vacuum component to the created matter constituents. It is shown that if the specific entropy per particle remains constant during the process, the equilibrium relations are preserved. In particular, if the vacuum decays into photons, the energy density $\rho$ and average number density of photons $n$ scale with the temperature as $\rho \sim T^{4}$ and $n \sim T^{3}$. The temperature law is determined and a generalized Planckian type form of the spectrum, which is preserved in the course of the evolution, is also proposed. Some consequences of these results for decaying vacuum FRW type cosmologies as well as for models with ``adiabatic'' photon creation are discussed.Comment: 21 pages, uses LATE

The relationship between current account deficits and unemployment in Turkey

In this chapter, we test the nature of the variety of empirical relationships between current account deficits and unemployment in Turkey over 2000Q1-2012Q1. Our working hypothesis in this paper is that the meager job creation in Turkey over 2000s is the direct symptom of a speculative-led growth environment (Grabel, 1995) together with an excessively open and unregulated capital account in the age of relatively cheap and abundant global finance. Based on the vector error correction model (VECM), we found that there is a unidirectional causality running from current account deficits to unemployment. Both Impulse Response and Variance Decomposition analyses are quite consistent with results of VECM. We interpret these findings as evidence of the structural characteristics of unemployment, reflected in output elasticities, being embedded under the deepening external fragility of the Turkish economy over the 2000s. © 2016, IGI Global. All rights reserved

Investigating Performance of High-Rate GNSS-PPP and PPP-AR for Structural Health Monitoring: Dynamic Tests on Shake Table

© 2020 American Society of Civil Engineers. This paper investigates the usability of Global Navigation Satellite System (GNSS) Precise Point Positioning (PPP) methods, traditional PPP with a float-ambiguity solution and with ambiguity resolution (PPP-AR), in structural health monitoring applications based on experimental tests using a single-axis shake table. To evaluate the performance of the PPP methodologies, harmonic oscillations of the motion table with amplitudes ranging from 5 to 10 mm and frequency between 0.1 and 3 Hz were generated representing a wide range of possible structural motions. In addition, ground motion similar to those experienced during a real earthquake, the 1995 Kobe earthquake, and step motions were generated on the shake table. GNSS PPP-derived positioning results at 20 Hz were compared, in both of the frequency and time domains, with reference data comprising LVDT data and relative positioning data. Results show that both PPP methods' measurements can be used in the computation of harmonic oscillation frequencies compared to the LVDT and relative positioning values. The observed amplitudes of the harmonic oscillations are slightly different from the LVDT values on the order of millimeters. The results of a step motion experiment demonstrated that PPP-AR is better than traditional PPP in exhibiting quasi-static or static displacement. Moreover, the capabilities of traditional PPP and PPP-AR methods are evaluated with respect to the natural frequency of a small-scale structural model excited on the shake table. The frequency spectrum of this small-scale structural model derived from the PPP methods is consistent with finite-element model (FEM)-predicted values and relative positioning. The research presented here demonstrates the potential of the high-rate GNSS PPP and PPP-AR methods to reliably monitor structural and earthquake-induced vibration frequencies and amplitudes for both structural and seismological applications. Specifically, all results reveal that high-rate PPP-AR is more accurate than traditional PPP for both dynamic and static displacement detection

Scaling Cosmologies from Duality Twisted Compactifications

Oscillating moduli fields can support a cosmological scaling solution in the presence of a perfect fluid when the scalar field potential satisfies appropriate conditions. We examine when such conditions arise in higher-dimensional, non-linear sigma-models that are reduced to four dimensions under a generalized Scherk-Schwarz compactification. We show explicitly that scaling behaviour is possible when the higher-dimensional action exhibits a global SL(n,R) or O(2,2) symmetry. These underlying symmetries can be exploited to generate non-trivial scaling solutions when the moduli fields have non-canonical kinetic energy. We also consider the compactification of eleven-dimensional vacuum Einstein gravity on an elliptic twisted torus.Comment: 21 pages, 3 figure

Black Hole Formation with an Interacting Vacuum Energy Density

We discuss the gravitational collapse of a spherically symmetric massive core of a star in which the fluid component is interacting with a growing vacuum energy density. The influence of the variable vacuum in the collapsing core is quantified by a phenomenological \beta-parameter as predicted by dimensional arguments and the renormalization group approach. For all reasonable values of this free parameter, we find that the vacuum energy density increases the collapsing time but it cannot prevent the formation of a singular point. However, the nature of the singularity depends on the values of \beta. In the radiation case, a trapped surface is formed for \beta<1/2 whereas for \beta>1/2, a naked singularity is developed. In general, the critical value is \beta=1-2/3(1+\omega), where the \omega-parameter describes the equation of state of the fluid component.Comment: 9 pages, 8 figure

Supernovae Ia Constraints on a Time-Variable Cosmological "Constant"

The energy density of a scalar field $\phi$ with potential $V(\phi) \propto \phi^{-\alpha}$, $\alpha > 0$, behaves like a time-variable cosmological constant that could contribute significantly to the present energy density. Predictions of this spatially-flat model are compared to recent Type Ia supernovae apparent magnitude versus redshift data. A large region of model parameter space is consistent with current observations. (These constraints are based on the exact scalar field model equations of motion, not on the widely used time-independent equation of state fluid approximation equations of motion.) We examine the consequences of also incorporating constraints from recent measurements of the Hubble parameter and the age of the universe in the constant and time-variable cosmological constant models. We also study the effect of using a non-informative prior for the density parameter.Comment: Accepted for publication in Ap