5,141 research outputs found

    On moments of the integrated exponential Brownian motion

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    We present new exact expressions for a class of moments for the geometric Brownian motion, in terms of determinants, obtained using a recurrence relation and combinatorial arguments for the case of a Ito's Wiener process. We then apply the obtained exact formulas to computing averages of the solution of the logistic stochastic differential equation via a series expansion, and compare the results to the solution obtained via Monte Carlo

    Seasonal variation in yield and chemical composition of Moroccan Thymbra capitata (L.) Cav. essential oil and its corresponding hydrolat extracted essential oil

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    The aim of the present work was to study the variation in yield and chemical composition of the pure essential oil (EO) and essential oil dissolved in its corresponding hydrolat (HEO) of Thymbra capitata (L.) Cav. of Morocco according to its stage of growth. The results obtained revealed that the yield of essential oil increases with the growth of the plant to reach its maximum at post-flowering stage (2.90%). On the other hand, the yield of dissolved essential oil in the corresponding hydrolats peaked at the flowering stage (0.53%) and then dropped. The analysis of these oils was performed by the GC-MS and showed that carvacrol was the major compound of this plant during its growth stage. The highest carvacrol content was noted at the flowering stage for EO (84.26%) and at the pre-flowering stage for HEO (98.54%). However, the evolution of concentration of p-cymene (3.84-6.01%) and g-terpinene (3.45-5.68%) in EO seems to be the opposite of carvacrol. Moreover, these two monoterpene hydrocarbons are absent or almost absent in HEO

    Indicators of Apoptosis in Duchenne Muscular Dystrophy Patients

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    Background: Tissue sections of dystrophic muscle demonstrate apoptotic myonuclei in degenerating muscle fibers of Duchene muscle dystrophy (DMD) patients. The apoptosis cascade can be triggered by 2 main pathways, via an intrinsic, endogenous system such as the mitochondrial Bax/Bcl-2 or via an extrinsic system involving transmembrane receptors of the death receptor family Fas and Fas Ligand (FasL). Aim of the Work: The present study is an attempt to demonstrate the levels of Fas and FasL and Bax/Bcl-2 in DMD pathogenesis. Patient and Methods: Subjects were 16 boys with DMD diagnosed clinically and at the molecular level versus 20 age and socioeconomic matching healthy boys. Results: Plasma DNA fragmentation (0.38%±0.12 vs. 0.2%±.0.1.5) and Fas (9.9±2.8 vs. 2±0.1,

    Determination and Distribution Map for Radionuclides in Soil Samples from Different Location by Gamma Spectrometry Using Software Analysis

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    The fundamental goal of the current study is to determine the mean activity concentrations of natural and artificial radionuclides of 226Ra, 232Th, 40K, and 137Cs using gamma spectrometry for three locations, in Egypt, Saudi Arabia, and Iraq, which are significant and vital countries in the Middle East. The mean absorbed dose rate equals 22.35, 28.96, and 43.34 nGy h-1 for Egypt, Saudi Arabia, and Iraq. The results are consistent with international reports. The dose contribution percentages for investigated locations are 24 %, 30 %, and 46 % for Egypt, Saudi Arabia, and Iraq, respectively. The obtained results were clarified by statistical measurements using one-way ANOVA test to determine the distribution and differences between the averages of the three groups under study, as they may be influenced by geological variations and human intervention. It was found that the Iraq samples followed a symmetrical, standard normal distribution, while samples from Egypt and Saudi Arabia did not. Statistically significant differences were found between the data from the three countries

    Prevalence of plasmid-mediated quinolone resistance determinants in Enterobacteriaceae from Tunisia

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    AbstractThe spread of plasmid-mediated quinolone resistance determinants (qnr-like determinants, aac(6′)-Ib-cr and qepA genes) was evaluated in a collection of 281 nalidixic acid-resistant enterobacterial isolates recovered between September 2005 and December 2007 at the Sahloul Hospital, Sousse, Tunisia. Sixteen percent of those isolates carried qnr genes encoding the QnrB1, QnrB2, QnrA6 or QnrS1 determinants. Most qnr-positive isolates were extended-spectrum ß-lactamase (ESBL) producers, being predominantly of the CTX-M-15 type, but also of the SHV-28 and SHV-12 types. The qnr genes were located on plasmids with a size in the range 55–150 kb. The qnrB2 gene was associated with sul1-type integron structures and the qnrB1 gene was associated with orf1005, whereas the genetic environment of qnrA6 was unknown. In two isolates, the qnrS1 gene was located downstream of an ISEcl2 element on plasmids that often carried the narrow-spectrum ß-lactamase gene blaLAP-2; qepA and aac(6′)-Ib-cr were not detected. The present study highlights the wide spread of Qnr-like determinants in Tunisia, with an association with the ESBL CTX-M-15 in human clinical isolates

    Comprehensive Review on the Dynamic and Seismic Behavior of Flat-Bottom Cylindrical Silos Filled With Granular Material

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    The seismic design of industrial flat-bottom ground-supported silos filled with granular material still presents several challenges to be addressed. They are related to the main aspects which differentiate silo structures containing granular material from other civil structural typologies: 1) the relatively low silo structure mass as compared to the ensiled content mass; 2) the granular nature of the ensiled material. Indeed, the internal actions in the structural members are governed by the complex dynamic interactions along the interfaces between granular content and silo wall or base, or even the internal interaction between particles. More in detail, even though the scientific interest in such complex interactions dates back to the middle of the 19th century, several issues are still unclear such as the dependency of the fundamental dynamic properties (period of vibration and damping ratio) on the characteristics of the dynamic excitation (intensity, frequency content, duration) or the amount of ensiled material mass activated during a seismic excitation and provoking extra pressures on the wall (effective mass). Therefore, most of current seismic code provisions for silos are grounded on rather approximate and simplified assumptions leading to often over-conservative evaluations. The present paper intends to provide a comprehensive summary of the mainly acknowledged experimental and theoretical advances in the dynamic and seismic behavior of silos, supporting the potential researcher in the field to understand the real differences between the code assumptions and recommendations and the actual conditions, as well as illustrating the open issues to be still further investigated

    Multi-Zone Shell Model for Turbulent Wall Bounded Flows

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    We suggested a \emph{Multi-Zone Shell} (MZS) model for wall-bounded flows accounting for the space inhomogeneity in a "piecewise approximation", in which cross-section area of the flow, SS, is subdivided into "jj-zones". The area of the first zone, responsible for the core of the flow, S1S/2S_1\simeq S/2, and areas of the next jj-zones, SjS_j, decrease towards the wall like Sj2jS_j\propto 2^{-j}. In each jj-zone the statistics of turbulence is assumed to be space homogeneous and is described by the set of "shell velocities" unj(t)u_{nj}(t) for turbulent fluctuations of the scale 2n\propto 2^{-n}. The MZS-model includes a new set of complex variables, Vj(t)V_j(t), j=1,2,...j=1,2,... \infty, describing the amplitudes of the near wall coherent structures of the scale sj2js_j\sim 2^{-j} and responsible for the mean velocity profile. Suggested MZS-equations of motion for unj(t)u_{nj}(t) and Vj(t)V_j(t) preserve the actual conservations laws (energy, mechanical and angular momenta), respect the existing symmetries (including Galilean and scale invariance) and account for the type of the non-linearity in the Navier-Stokes equation, dimensional reasoning, etc. The MZS-model qualitatively describes important characteristics of the wall bounded turbulence, e.g., evolution of the mean velocity profile with increasing Reynolds number, \RE, from the laminar profile towards the universal logarithmic profile near the flat-plane boundary layer as \RE\to \infty.Comment: 27 pages, 17 figs, included, PRE, submitte

    Hydrodynamic fluctuations in the Kolmogorov flow: Linear regime

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    The Landau-Lifshitz fluctuating hydrodynamics is used to study the statistical properties of the linearized Kolmogorov flow. The relative simplicity of this flow allows a detailed analysis of the fluctuation spectrum from near equilibrium regime up to the vicinity of the first convective instability threshold. It is shown that in the long time limit the flow behaves as an incompressible fluid, regardless of the value of the Reynolds number. This is not the case for the short time behavior where the incompressibility assumption leads in general to a wrong form of the static correlation functions, except near the instability threshold. The theoretical predictions are confirmed by numerical simulations of the full nonlinear fluctuating hydrodynamic equations.Comment: 20 pages, 4 figure
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