Two Electrons in a Quantum Dot: A Unified Approach

Low-lying energy levels of two interacting electrons confined in a two-dimensional parabolic quantum dot in the presence of an external magnetic field have been revised within the frame of a novel model. The present formalism, which gives closed algebraic solutions for the specific values of magnetic field and spatial confinement length, enables us to see explicitly individual effects of the electron correlation.     

Comparison of two glutathione S -transferases used in capacitive biosensors for detection of heavy metals

This work describes the development of a heavy-metal biosensor based on either recombinant 6His-Tag glutathione S-transferase (GST-(His)₆) or glutathione S-transferase Theta 2-2 (GST-theta 2-2), and a capacitive transducer. The dynamic range of the pure bovine liver GST-Theta 2-2 biosensor was 1?fM to 1?mM for Zn²⁺, and 10?pM to 1?mM for Cd²⁺. The GST-(His)₆ biosensor was able to detect Zn²⁺ and Cd²⁺ in the range of 1?fM to 10?µM, and Hg²⁺ in the range of 1?fM to 10?mM. The bovine liver GST Theta 2-2 biosensor displays an increased selectivity and a wider dynamic range for Zn²⁺ compared with the GST-(His)₆ biosensor. Therefore, by using different GST isozymes, it is possible to modulate important characteristics of capacitive biosensors for the detection of heavy metals.     

Polarographic determination of herbicide thifensulfuron methyl/application to agrochemical pesticide,soil, and fruit juice

A novel, sensitive, simple, fast, and fully validated differential pulse polarographic (DPP) method for the determination of trace amounts of thifensulfuron-methyl in pesticide formulation, soil, and orange juice is reported. This procedure was based on a highly sensitive peak formed due to the reduction of thifensulfuron-methyl on a dropping mercury electrode over the pH range 1.00–10.00 in Britton–Robinson buffer. The polarographic reduction exhibits only a single peak in the pH ranges pH?≥?3.0 and pH?≤?6.0 and pH?=?10.0 located at potential values of ?1.010, ?1.350, and ?1.610?V (vs. SCE), respectively. The single peak appeared as a maximum at pH 3.0 (?1.010?V) was well resolved and suitable to be investigated for analytical use. This peak showed quantitative increments with the additions of standard thifensulfuron-methyl solution under the optimal conditions, and the cathodic peak current was linearity proportional to the thifensulfuron-methyl concentration in the range of 2?×?10^?7–5?×?10^?5?M. The limit of detection (LOD) and limit of quantification (LOQ) were obtained as 1.05?×?10^?7 and 3.50?×?10^?7?M, respectively, according to the relation k ?×?SD/b (where k?=?3 for LOD, k?=?10 for LOQ, SD is the standard deviation of the blank, and b is the slope of the calibration curve). The proposed method was applied to pesticide formulation (Harmony® Extra), and the average percentage recovery was in agreement with that obtained by the spectrophotometric comparison method, 97.82 and 102.6%, respectively. The method was extended to determination of thifensulfuron-methy in spiked soil and orange juice, showing a good reproducibility and accuracy with a relative standard deviation of 4.55 and 1.40%, and relative errors of +2.80 and +1.90%, respectively.     

Chitosan matrices modified with carbon nanotubes for use in mediated microbial biosensing

We describe a microbial sensor based on Pseudomonas fluorescens cells that was prepared by modifying graphite electrodes with chitosan and carbon nanotubes. Chronoamperometry was performed at +0.3 V in the presence of hexacyanoferrate as a mediator and revealed a good response to glucose which is linear in the 1.0 to 5.0 mM concentration range. Linearity was defined by the equation of y?=?102.120x?13.279 (R ²?=?0.998) (y shows current density as nA.cm^?2 and x shows glucose concentration in mM). The effect of the CNTs on the response was compared to that of electrodes made without CNTs.

Solvability conditions and monotone iterative scheme for boundary-value problems related to nonlinear monotone potential operators

This article deals with boundary-value problems (BVPs) for the second-order nonlinear differential equations with monotone potential operators of type Au := ??(k(|?u|²)?u(x)) + q(u ²)u(x), x ∈ Ω ? R ⁿ . An analysis of nonlinear problems shows that the potential of the operator A as well as the potential of related BVP plays an important role not only for solvability of these problems and linearization of the nonlinear operator, but also for the strong convergence of solutions of corresponding linearized problems. A monotone iterative scheme for the considered BVP is proposed.     

Indecomposable (1,3)-Groups and a matrix problem

Almost completely decomposable groups with a critical typeset of type (1, 3) and a p-primary regulator quotient are studied. It is shown that there are, depending on the exponent of the regulator quotient p ^k , either no indecomposables if k ? 2; only six near isomorphism types of indecomposables if k = 3; and indecomposables of arbitrary large rank if k ? 4.     

On the uniform motion of a relativistic charged particle in a homogeneous electromagnetic field in Minkowski space

We discuss the geometric characterization of the trajectory of a moving charged particle, for the case of a homogeneous electromagnetic field, in Minkowski space when the motion is governed by the Lorentz equation. We employ a totally relativistic approach during the discussion. It is based on a systematic use of the Faraday antisymmetric tensor properties of the electromagnetic field and of the four‐dimensional Frenet‐Serret formula, which is adapted to the Minkowski 4‐space with index two to determine the worldline geometry of the electromagnetic field acting on the particle. Finally, we present the necessary and sufficient conditions to obtain uniform motion of the relativistic charged particle in a homogeneous electromagnetic field in      

Simultaneous determination of levodopa and benserazide using poly(3-methylthiophene) and a multi-walled carbon nanotube sensor

Journal of Solid State Electrochemistry - Rapid, reliable, reproducible, and repeatable modified sensor designs have been developed to distinguish the binary mixture of levodopa and benserazide in...     

Analysis for the identification of an unknown diffusion coefficient via semigroup approach

This paper presents a semigroup approach for the mathematical analysis of the inverse coefficient problems of identifying the unknown coefficient k(u_x) in the inhomogenenous quasi‐linear parabolic equation u_t(x, t)=(k(u_x)u_x(x, t))_x +F(u), with the Dirichlet boundary conditions u(0, t)=ψ₀, u(1, t)=ψ₁ and source function F(u). The main purpose of this paper is to investigate the distinguishability of the input–output mappings Φ[·]:??→C¹[0, T], Ψ[·]:??→C¹[0, T] via semigroup theory. Copyright © 2009 John Wiley & Sons, Ltd.     

Investigation of Solvent Effects on Photophysical Properties of New Aminophthalimide Derivatives-Based on Methanesulfonate

Novel aminophthalimide derivatives were synthesized starting from (3aR,7aS)-2-(2-hydroxypropyl)-3a,4,7,7a–tetrahydro-1H-isoindole-1,3(2H)-dione (9) , and solvent effects on the photo-physical properties of these newly synthesized aminophthalimide derivatives (compounds 14 and 15) were investigated using UV-Vis absorption spectroscopy, steady-state and time-resolved fluorescence measurements. Both absorption and fluorescence spectra exhibited bathochromic shift with the increased polarity of the solvents for both molecules. Solute-solvent interactions were analyzed using the Lippert-Mataga and Bakhshiev polarity functions, and Kamlet-Taft and Catalan multiple linear regression approaches. The results revealed that these two molecules experienced specific interactions. Furthermore, photo-physical parameters were calculated for both molecules in all of the solvents, such as the fluorescence quantum yield, fluorescence lifetime, radiative (k_r) and non-radiative (k_nr) rate constant values. It was observed that the fluorescence quantum yield values decreased linearly with increasing solvent polarity. This study proved the new dyes including isopropyl methanesulfonate group displayed different behavior from previous studies of aminophthalimide derivatives in water. It was recommended that these new dyes having interesting properties by changing solvent can be used various applications such as environmentally sensitive fluorescent probes, labels in biology, laser industry.