Dirac Fermions in Inhomogeneous Magnetic Field

We study a confined system of Dirac fermions in the presence of inhomogeneous magnetic field. Splitting the system into different regions, we determine their corresponding energy spectrum solutions. We underline their physical properties by considering the conservation energy where some interesting relations are obtained. These are used to discuss the reflexion and transmission coefficients for Dirac fermions and check the probability condition for different cases. We generalize the obtained results to a system with gap and make some analysis. After evaluating the current-carrying states, we analyze the Klein paradox and report interesting discussions.Comment: 28 pages, 15 figures. Version to appear in JP

Shrinkage Estimation Using Ranked Set Samples

The purpose of this article is two-fold. First, we consider the ranked set sampling (RSS) estimation and testing hypothesis for the parameter of interest (population mean). Then, we suggest some alternative estimation strategies for the mean parameter based on shrinkage and pretest principles. Generally speaking, the shrinkage and pretest methods use the non-sample information (NSI) regarding that parameter of interest. In practice, NSI is readily available in the form of a realistic conjecture based on the experimenter\u27s knowledge and experience with the problem under consideration. It is advantageous to use NSI in the estimation process to construct improved estimation for the parameter of interest. In this contribution, the large sample properties of the suggested estimators will be assessed, both analytically and numerically. More importantly, a Monte Carlo simulation is conducted to investigate the relative performance of the estimators for moderate and large samples. For illustrative purposes, the proposed methodology is applied to a published data set. © 2011 King Fahd University of Petroleum and Minerals

High-Strouhal-number pulsatile flow in a curved pipe

The high-Strouhal-number pulsatile flow in a curved pipe is studied numerically. A general force analysis is developed for the bend force, where the new contribution from flow acceleration is identified and analysed. The mechanisms of secondary flow production are studied by extending Hawthorne's (Proc. R. Soc. Lond. A, vol. 206, issue 1086, 1951, pp. 374–387) model to account for viscous effects and applied to assess the distinct contributions from an inviscid stretching and no-slip condition. A detailed comparison is made between the numerical simulations and models for a pipe flow characterised by a volume flux Q=UbA|sinΩpt| (where Ub is the maximum bulk velocity, Ωp is the angular frequency and A is the pipe cross-sectional area). For high-Reynolds-number (Reb) and high-Strouhal-number (St), the bend force predictions are in good agreement with the numerical results over a wide range of bend curvature (Rc/D; where Rc is the bend radius of curvature and D is the pipe diameter) owing to the influence of the streamwise flow acceleration on the pressure field. At high-St, the streamwise vorticity (secondary flow) distribution is steady and close to the low-St case, which is explained using a linear secondary flow model

Acoustics and vibrations in a complex piping network with pump startup–shutdown transients

Pump dynamic operational conditions result in extreme transient events that can enhance the response of piping networks. The predominant transients during rapid startup and shutdown are mainly studied for centrifugal pumps and are scarce for reciprocating pumps. Our study extends the conventional steady-state analysis to include the effect of reciprocating pump dynamic loading on pulsatile flow-induced acoustics and vibrations in a complex piping network. The forced response resulting from acoustical–structural coupling is assessed by utilising the one-dimensional multiphysics piping acoustic model and beam structural model. The network responses to pulsatile flows during dynamic pump loading (rapid start-up-shutdown events) are compared to the responses due to pulsatile flows during steady-state pump loading. With pump startup–shutdowns operations accompanied by pulsatile flows, the network response is the result of the combination of the transient and steady-state characteristics of plane acoustic waves and structural vibrations. The dynamic pump loading excites the fundamental, low-frequency acoustic eigenmode that causes transient loading of pipeline similar to reservoir–pipe–valve (RPV) systems

On differences between fractional and integer order differential equations for dynamical games

We argue that fractional order (FO) differential equations are more suitable to model complex adaptive systems (CAS). Hence they are applied in replicator equations for non-cooperative game. Rock-Scissors-Paper game is discussed. It is known that its integer order model does not have a stable equilibrium. Its fractional order model is shown to have a locally asymptotically stable internal solution. A FO asymmetric game is shown to have a locally asymptotically stable internal solution. This is not the case for its integer order counterpart.Comment: 4 page

DESIGN AND EVALUATION OF DOMPERIDONE SUBLINGUAL TABLETS

Objective: The aim of this work was to enhance the bioavailability of poorly soluble, anti-emetic drug; domperidone (DMP) having a poor oral bioavailability (13-17%) due to extensive first pass metabolism. The goal of this study was achieved through solubilization of DMP using solid dispersion technology followed by incorporation of solid dispersions into sublingual tablets to bypass pre-systemic metabolism.Methods: Solid dispersions of DMP with Pluronic F-68 were prepared in different weight ratios by fusion method and they were evaluated for their in vitro dissolution rate to select the best ratio for final formulation. Then, solid dispersions were formulated into sublingual tablets in combination with various soluble excipients. Sublingual tablets were prepared by direct compression technique and evaluated for their physical properties, in vitro dissolution rate and kinetics of drug release. The best formulae were selected for in vivo studies in rabbits in comparison with marketed oral tablets; Motinorm®.Results: Solid dispersions of DMP with Pluronic F-68 in a weight ratio of 1:7 (w/w) showed the highest dissolution rate and were selected for sublingual tablets formulation. Sublingual tablets formulae S16 (containing Fructose and 10% w/w Ac-Di-Sol) and S20 (containing Fructose and 10% w/w Explotab) showed the best results and were selected for in vivo studies in rabbits. The selected formulae showed marked enhancement of DMP bioavailability compared with the commercial oral tablets; Motinorm®, with relative bioavailability values of 432.49±10.13% and 409.32±11.59 % for S16 and S20, respectively.Conclusion: The results confirmed that sublingual tablets were an effective tool for DMP delivery with marked enhancement of bioavailability.Keywords: Domperidone, Solubility, Solid dispersions, Sublingual tablets, First-pass metabolism, Bioavailabilit