Calibration of different plastic track detectors using accelerated heavy ions

Measurements of the dependence of track etch rate on the energy-loss of different ions have been presented. In this method, ₁₈ ⁴⁰ Ar, ₁₀ ²² Ne, ₈ ¹⁶ O and ₆ ¹² C-ions of different energies are used as energetic heavy ions for track formation in the detectors. The bulk etch rate and track etch rate are measured for different temperatures and hence the activation energies are determined. The variation ofV =V _t /V _b along the trajectory of the track has been shown for different temperatures. The maximum etched track length is compared with the theoretical range as well as with the range reported earlier. The experimental results indicate the absence of a well-defined threshold in the plastics studied.     

The phases of two-dimensional matter,their transitions,and solid-state stability: A perspective via computer simulation of simple atomic systems

An extensive computer simulation investigation of the structure, thermodynamics and phase stability of the two-dimensional Lennard-Jones system is presented, with special emphasis on the low-pressure melting regime of the phase diagram. This investigation includes isobaric-isothermal Monte Carlo simulations of the various phases of the two-dimensional Lennard-Jones system and of the melting and vaporization processes in configuration space, the isodensity-isothermal Monte Carlo simulations of two-phase coexistence between crystal and liquid and between liquid and vapor, the determination of the phase diagram, the establishment of the thermodynamic melting temperature, and the determination of the physical significance of the Kosterlitz-Thouless-Feynman dislocation model for melting in relation to the stability of the crystalline phase. I conclude that th phase diagram of the Lennard-Jones system in two dimensions is qualitatively similar to that in three dimensions. Finally, I present a new simulation method for doing molecular dynamics at constant pressure and/or constant temperature, and employ this method to study the temporal-spatial evolution of two-dimensional melting and vaporization.     

Estimating arrival rate of nonhomogeneous Poisson processes with semidefinite programming

We present a summary of methods based on semidefinite programming for estimating arrival rate of nonhomogeneous Poisson processes from a finite set of observed data. Both one-dimensional time dependent, and multi-dimensional time and location dependent rates are considered. The arrival rate is a nonnegative function of time (or time and location). We also assume that it is a smooth function with continuous derivatives of up to certain order k. We estimate the rate function by one or multi-dimensional splines, with the additional condition that the underlying rate function is nonnegative. This approach results in an optimization problem over nonnegative polynomials, which can be modeled and solved using semidefinite programming. We also describe a method which requires only linear constraints. Numerical results based on e-mail arrival and highway accidents are presented.     

On the Numerical Range of Operator Polynomials

An upper bound for the number of components of the numerical range of matrix polynomials is established. We also establish a necessary condition and a sufficient condition for the connectedness of the numerical range of a quadratic selfadjoint matrix polynomial. The boundary of the numerical range of linear matrix polynomials is also considered.     

Numerical Simulation of Electrochemical Systems by Coupling Analytical Calculation of the Diffuse Double Layer and Finite Element Description of Solution Bulk

Numerical modelling of electrochemical systems covers length scales from the nanometers up to the macroscopic scale. With finite element methods, the mesh must be extremely fine to describe the diffuse double layer, thus increasing the needed computational resources. We propose a method to describe the diffuse double layer by analytical equations, expressed as boundary conditions for the partial differential equations describing the solution bulk. We apply the method to a one-dimensional system, i. e. to a cell with plane parallel electrodes, in the presence of a redox couple and a supporting electrolyte. We provide evidence of the precision of the method.     

US FDA–validated TLC method with four greenness assessment evaluations for simultaneous determination of prednisolone and esomeprazole in spiked human plasma

Recently, prednisolone has been used in treating many medical conditions, such as autoimmune diseases and cancer. It is also prescribed to mitigate the respiratory complications caused by COVID-19 infection. It can cause some health complications, such as GIT ulcers, so it should be co-administered with proton-pump inhibitors, such as esomeprazole, to prevent the risk of ulcers. This work aims to develop an ecofriendly and sensitive TLC method for simultaneous determination of esomeprazole and prednisolone in their binary mixtures and spiked human plasma. Separation was performed using a mixture of ethyl acetate, methanol, and ammonia (9.5:0.5:0.1, v/v/v) as an eluting system with UV scanning at 245 nm. Dapoxetine was used as an internal standard to correct the variation during sampling. The resulting R_f values for plasma, esomeprazole, prednisolone, and dapoxetine were 0.03, 0.51, 0.72 and 0.85, respectively. Four greenness assessment tools—national environmental method index, eco-scale assessments, analytical greenness metric approach (AGREE), and green analytical procedure index (GAPI)—were used to evaluate the greenness characteristics of the proposed method to the environment, and the results were acceptable and satisfactory. Validation parameters were checked according to the US FDA guidelines to achieve the international requirements for bioanalytical method validation, and the results were within the accepted ranges.     

Le problème de Yamabe avec singularités

Let (Mn,g) be a compact riemannian manifold of dimension n?3. Under some assumptions, we prove that there exists a positive function φ solution of the Yamabe equation

     

Uniqueness for an overdetermined boundary value problem for the p-Laplacian

For set , and let be a measure with compact support. Suppose, for , there are functions and (bounded) domains , both containing the support of with the property that in (weakly) and in the complement of . If in addition is convex, then and .

     

Optimal crop planting schedules and financial hedging strategies under ENSO-based climate forecasts

This paper investigates the impact of ENSO-based climate forecasts on optimal planting schedules and financial yield-hedging strategies in a framework focused on downside risk. In our context, insurance and futures contracts are available to hedge against yield and price risks, respectively. Furthermore, we adopt the Conditional-Value-at-Risk (CVaR) measure to assess downside risk, and Gaussian copula to simulate scenarios of correlated non-normal random yields and prices. The resulting optimization problem is a mixed 0?C1 integer programming formulation that is solved efficiently through a two-step procedure, first through an equivalent linear form by disjunctive constraints, followed by decomposition into sub-problems identified by hedging strategies. With data for a representative cotton producer in the Southeastern United States, we conduct a study that considers a wide variety of optimal planting schedules and hedging strategies under alternative risk profiles for each of the three ENSO phases (Niña, Niño, and Neutral.) We find that the Neutral phase generates the highest expected profit with the lowest downside risk. In contrast, the Niña phase is associated with the lowest expected profit and the highest downside risk. Additionally, yield-hedging insurance strategies are found to vary significantly, depending critically on the ENSO phase and on the price bias of futures contracts.