Belaid F.,University Paris Est Creteil |
Abderrahmani F.,University of Abderrahmane Mira de Bejaia
Energy Policy | Year: 2013
This article addresses the issue of electricity consumption, petroleum price and economic growth in Algeria. The primary objective is to investigate and analyze the causal relationship between electricity consumption (EC), Brent oil price (BOP) and economic growth (GDP) for Algeria over the period of 1971-2010. To examine short-run, long-run and joint causality relationships we used a multivariate cointegration approach based on the recent advances in time series econometrics (e.g., Zivot-Andrews test; Gregory-Hansen cointegration test; Vector Error Correction Models (VECM)). The empirical results show that there is evidence of short-run and a strong long-run bi-directional causal relationship between EC and real GDP in Algeria. Findings indicate also the absence of causal relationship between BOP and EC. Our empirical findings support the idea that there a link between electricity consumption and economic growth and disproves the neo-classical assumption referred to as the "neutrality hypothesis". © 2012 Elsevier Ltd.
Ait-Amokhtar H.,University of Abderrahmane Mira de Bejaia |
Fressengeas C.,French National Center for Scientific Research
Acta Materialia | Year: 2010
The Portevin-Le Chatelier (PLC) effect in an Al-3.2%Mg alloy is investigated using velocity-driven tensile tests at room temperature, in a strain rate range where the crossover from continuous (type A bands) to discontinuous propagation (type B bands) occurs. Digital image correlation and infrared thermography techniques are used to render the strain, strain rate and temperature fields. Particular interest is paid to the critical tests where type A and type B bands are met sequentially. Attention is focused on the unsteadiness and anisotropy of the field variables and their consequences on the instability. It is shown that the decrease of strain rate at large strain and the elevation in temperature occurring at large driving velocity favor dynamic strain aging, reduce strain rate sensitivity and enhance strain localization. Interpretation for the crossover from type A to type B in a single test is provided accordingly. The effects of strain rate and temperature unsteadiness on the extent of the range of PLC effect, the type of instability and the critical plastic strain for the onset of serrations are discussed. © 2009 Acta Materialia Inc.
Hammad F.,University of Abderrahmane Mira de Bejaia
International Journal of Theoretical Physics | Year: 2012
By viewing space-time as a continuum elastic medium and introducing an entropy functional for its elastic deformations, T. Padmanabhan has shown that general relativity emerges from varying the functional and that the latter suggests holography for gravity and yields the Bekenstein-Hawking entropy formula. In this paper we extend this idea to Riemann-Cartan space-times by constructing an entropy functional for the elastic deformations of space-times with torsion. We show that varying this generalized entropy functional permits to recover the full set of field equations of the Cartan-Sciama-Kibble theory. Our generalized functional shows that the contributions to the on-shell entropy of a bulk region in Riemann-Cartan space-times come from the boundary as well as the bulk and hence does not suggest that holography would also apply for gravity with spin in space-times with torsion. It is nevertheless shown that for the specific cases of Dirac fields and spin fluids the system does become holographic. The entropy of a black hole with spin is evaluated and found to be in agreement with Bekenstein-Hawking formula. © 2011 Springer Science+Business Media, LLC.
Bellik Y.,University of Abderrahmane Mira de Bejaia
Asian Pacific Journal of Tropical Disease | Year: 2014
Objective: To compare in vitro antioxidant and antimicrobial activities of the essential oil and oleoresin of Zingiber officinale Roscoe. Methods: The antioxidant activity was evaluated based on the ability of the ginger extracts to scavenge ABTS°+ free radical. The antimicrobial activity was studied by the disc diffusion method and minimal inhibitory concentration was determined by using the agar incorporation method. Results: Ginger extracts exerted significant antioxidant activity and dose-depend effect. In general, oleoresin showed higher antioxidant activity [IC50=(1.820±0.034) mg/mL] when compared to the essential oil [IC50=(110.14±8.44) mg/mL]. In terms of antimicrobial activity, ginger compounds were more effective against Escherichia coli, Bacillus subtilis and Staphylococcus aureus, and less effective against Bacillus cereus. Aspergillus niger was least, whereas, Penicillium spp. was higher sensitive to the ginger extracts; minimal inhibitory concentrations of the oleoresin and essential oil were 2 mg/mL and 869.2 mg/mL, respectively. Moreover, the studied extracts showed an important antifungal activity against Candida albicans. Conclusions: The study confirms the wide application of ginger oleoresin and essential oil in the treatment of many bacterial and fungal diseases. © 2014 Asian Pacific Tropical Medicine Press.
Hammad F.,University of Abderrahmane Mira de Bejaia
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014
In the present paper, we analyze a toy model for f(,R) gravity which has the form of a power-law modified gravity in which the exponent is space-time dependent. Namely, we investigate the effects of adding to the Hilbert-Einstein action an R term. We present possible equivalences of the model with known models of modified gravity theories and examine the problem of matter stability in this model. Like f(R)-gravity toy models, the present one offers the possibility of unifying the early- and the late-time evolution of the Universe. We show that the behavior of the scalar field depends globally on the size of the Universe and locally on the surrounding environment. For the early Universe a huge cosmological constant appears that might drive inflation. For the late times a tiny cosmological constant appears globally. © 2014 American Physical Society.