4,845 research outputs found
Quintessence and phantom cosmology with non-minimal derivative coupling
We investigate cosmological scenarios with a non-minimal derivative coupling
between the scalar field and the curvature, examining both the quintessence and
the phantom cases in zero and constant potentials. In general, we find that the
universe transits from one de Sitter solution to another, determined by the
coupling parameter. Furthermore, according to the parameter choices and without
the need for matter, we can obtain a Big Bang, an expanding universe with no
beginning, a cosmological turnaround, an eternally contracting universe, a Big
Crunch, a Big Rip avoidance and a cosmological bounce. This variety of
behaviors reveals the capabilities of the present scenario.Comment: 8 pages, 8 figure
Proton decay matrix elements with domain-wall fermions
Hadronic matrix elements of operators relevant to nucleon decay in grand
unified theories are calculated numerically using lattice QCD. In this context,
the domain-wall fermion formulation, combined with non-perturbative
renormalization, is used for the first time. These techniques bring reduction
of a large fraction of the systematic error from the finite lattice spacing.
Our main effort is devoted to a calculation performed in the quenched
approximation, where the direct calculation of the nucleon to pseudoscalar
matrix elements, as well as the indirect estimate of them from the nucleon to
vacuum matrix elements, are performed. First results, using two flavors of
dynamical domain-wall quarks for the nucleon to vacuum matrix elements are also
presented to address the systematic error of quenching, which appears to be
small compared to the other errors. Our results suggest that the representative
value for the low energy constants from the nucleon to vacuum matrix elements
are given as |alpha| simeq |beta| simeq 0.01 GeV^3. For a more reliable
estimate of the physical low energy matrix elements, it is better to use the
relevant form factors calculated in the direct method. The direct method tends
to give smaller value of the form factors, compared to the indirect one, thus
enhancing the proton life-time; indeed for the pi^0 final state the difference
between the two methods is quite appreciable.Comment: 56 pages, 17 figures, a comment and two references added in the
introduction, typo corrected in Eq.1
Capital Market Predictive Power on the Development of the Nigerian Economy: An Impulse Response and Variance Decomposition Approach
The study investigates the contributions of Nigeria s capital market to the development of Nigeria economy Most researchers focused on the capital market and growth nexus while we deviated by focusing on the role played by the capital market in ensuring the reduction of unemployment and poverty in Nigeria Specifically we investigated the contributions of market capitalization MCAP the value of share traded VST and all share index ASI to the unemployment rate UNPR and poverty NPI reductions in Nigeria within the period 1981 to 2017 The data series used was obtained from the annual statistical bulletin of the central bank of Nigeria CBN and Nigeria stock exchange NSE Preliminary analyses of stationarity and cointegration tests revealed that the series was non stationary at levels and cointegrated respectivel
Optical Absorption and Raman Spectroscopy Study of the Fluorinated Double-Wall Carbon Nanotubes
Double-wall carbon nanotube (DWNT) samples have been fluorinated at room temperature with varied concentration of a fluorinating agent BrF3. Content of the products estimated from X-ray photoelectron data was equal to CF0.20 and CF0.29 in the case of deficit and excess of BrF3. Raman spectroscopy showed considerable decrease of carbon nanotube amount in the fluorinated samples. Analysis of optical absorption spectra measured for pristine and fluorinated DWNT samples revealed a selectivity of carbon nanotube fluorination. Nanotubes with large chiral angle are more inert to the fluorinating agent used
Development of road infrastructure as a tool of transforming Ibiono Ibom local government area
The need for road infrastructure arises from the fact that there is a greater need for accessibility and smooth movement of abundant agricultural products especially from the rural areas to the markets in urban centres. The improvement of transportation network in the rural area in this regard becomes imperative. This study was conducted to reveal the importance of development of road infrastructure as a panacea for socio-economic advancement in the rural areas. The study area was stratified into three zones i.e Ibiono Central, Ibiono Northern and Ibiono Southern. The Gamma index was used to determine the level of connectivity of each zone in relation to the distribution of socio-economic activity or services in the area. In analysis of the road network connectivity the gamma Index was used. The results indicate a low connectivity, index of 0.26 for zone A, 0.40 for zone B and 0.31 for zone C, in each of the three zones. This implies that there is poor accessibility, poor connectivity, which result in low level of socio-economic activity in the area. The analysis of the socio-economic development variables was carried out based on quality point assigned to the variables. Finally the correlation analysis was employed to determine the relationship between road infrastructure and socio-economic development. The correlation coefficient of 0.87 indicates a strong, positive relationship between road infrastructure and socio-economic activity. From the findings it is recommended that a major road that links all the zones should be constructed while, other roads should be expanded and tarred; new roads should be developed to improve accessibility. Greater community participation in road development and rehabilitation should be encouraged and a comprehensive transportation plan should be put in place at the local government level. It is hoped that this detailed research work will serve as a basis for the improvement and development of road infrastructure in rural areas which is a catalyst to rural transformation.KEY WORDS: Road, Infrastructure, Paved, Unpaved, Socio-Economic Developmen
Screw dislocation in zirconium: An ab initio study
Plasticity in zirconium is controlled by 1/3 screw dislocations
gliding in the prism planes of the hexagonal close-packed structure. This
prismatic and not basal glide is observed for a given set of transition metals
like zirconium and is known to be related to the number of valence electrons in
the d band. We use ab initio calculations based on the density functional
theory to study the core structure of screw dislocations in zirconium.
Dislocations are found to dissociate in the prism plane in two partial
dislocations, each with a pure screw character. Ab initio calculations also
show that the dissociation in the basal plane is unstable. We calculate then
the Peierls barrier for a screw dislocation gliding in the prism plane and
obtain a small barrier. The Peierls stress deduced from this barrier is lower
than 21 MPa, which is in agreement with experimental data. The ability of an
empirical potential relying on the embedded atom method (EAM) to model
dislocations in zirconium is also tested against these ab initio calculations
Preface: International conference on data envelopment analysis—DEA40, 16–18 April 2018
info:eu-repo/semantics/publishedVersio
Adipokines in Nonalcoholic Steatohepatitis: From Pathogenesis to Implications in Diagnosis and Therapy
Nonalcoholic fatty liver disease (NAFLD) is the hepatic manifestation of the metabolic syndrome and can vary from benign steatosis to end-stage liver disease. The pathogenesis of non-alcoholic steatohepatitis (NASH) is currently thought to involve a multiple-hit process with the first hit being the accumulation of liver fat which is followed by the development of necroinflammation and fibrosis. There is mounting evidence that cytokines secreted from adipose tissue, namely, adipokines, are implicated in the pathogenesis and progression of NAFLD. In the current review, we explore the role of these adipokines, particularly leptin, adiponectin, resistin, tumor necrosis factor-a, and interleukin-6 in NASH, as elucidated in experimental models and clinical practice. We also comment on their potential use as noninvasive markers for differentiating simple fatty liver from NASH as well as on their potential future therapeutic role in patients with NASH
- …