Nickel and Tungsten Bimetallic Nanoparticles Modified Pencil Graphite Electrode: A High-performance Electrochemical Sensor for Detection of Endocrine Disruptor Bisphenol A

In this work, an economically viable, very low cost, indigenous, ubiquitously available electrochemical sensor based on bimetallic nickel and tungsten nanoparticles modified pencil graphite electrode (NiNP-WNP@PGE) was fabricated for the sensitive and selective detection of bisphenol A (BPA). The NiNP-WNP@PGE sensor was prepared by a facile electrochemical one step co-deposition method. The prepared nanocomposite was morphologically characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), electrochemically by cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The proposed sensor displayed high electrocatalytic activity towards electro-oxidation of BPA with one irreversible peak. The fabricated sensor displayed a wide detection window between 0.025 μM and 250 μM with a limit of detection of 0.012 μM. PGE sensor was successfully engaged for the detection of BPA in bottled water, biological, and baby glass samples.     

Development of Pen-type Portable Electrochemical Sensor Based on Au-W Bimetallic Nanoparticles Decorated Graphene-chitosan Nanocomposite Film for the Detection of Nitrite in Water,Milk and Fruit Juices

The development and fabrication of a simple, portable, and sensitive detection tool to precisely monitor nitrite level is of growing importance in electrochemistry research, given the strong interest in the protection of drinking water quality, treatment of wastewater, food production, and control of remediation processes. This work describes the fabrication of a simple, cost-effective, pen-type electrochemical sensor based on bimetallic gold and tungsten nanoparticles electrochemically decorated on graphene-chitosan modified pencil graphite electrode (PGE) for the trace detection of nitrite in real samples. The prepared nanocomposite was characterized using XRD, SEM, and EDS. The electrochemical behavior of the sensor was evaluated by cyclic voltammetry (CV) and impedance electrochemical spectroscopy (EIS). Results revealed that the proposed sensor displayed excellent electrocatalytic activity towards electro-oxidation of nitrite with an irreversible redox reaction. The AuNPs-WNPs@Gr-Chi/PGE sensor exhibited excellent analytical performance with a wide linear range from 10 to 250 μM towards nitrite. The LOD and LOQ were calculated to be 0.12 μM and 0.44 μM, respectively. The designed electrochemical sensor was successfully applied for the detection of nitrite in water, milk, and natural fruit juice samples.     

Two-echelon location routing synchronized with production schedules and time windows

Central European Journal of Operations Research - In this paper we study a problem that arose while planning the delivery of perishable goods, such as newspapers or foodstuff, in urban areas. The...     

A Projection Method for the Integer Quadratic Knapsack Problem

In this paper we present a new branch and bound algorithm for solving a class of integer quadratic knapsack problems. A previously published algorithm solves the continuous variable subproblems in the branch and bound tree by performing a binary search over the breakpoints of a piecewise linear equation resulting from the Kuhn-Tucker conditions. Here, we first present modifications to a projection method for solving the continuous subproblems. Then we implement the modified projection method in a branch and bound framework and report computational results indicating that the new branch and bound algorithm is superior to the earlier method.     

The semiclassical regime of the chaotic quantum-classical transition

An analysis of the semiclassical regime of the quantum-classical transition is given for open, bounded, one-dimensional chaotic dynamical systems. Environmental fluctuations-characteristic of all realistic dynamical systems-suppress the development of a fine structure in classical phase space and damp nonlocal contributions to the semiclassical Wigner function, which would otherwise invalidate the approximation. This dual regularization of the singular nature of the semiclassical limit is demonstrated by a numerical investigation of the chaotic Duffing oscillator.     

Fermion to boson mapping

The enveloping algebra, D_n, of fermions is extended on the lattice to include the discrete space invariance. This extended algebra, denoted X, has the space symmetry as a factor: X/D_n = space group.     

Analysis of current-voltage characteristics of inhomogeneous Schottky diodes at low temperatures

Two approaches of Gaussian distribution of barrier heights in inhomogeneous Schottky diodes have been analyzed by comparing the results for consistency between the two. For this the current-voltage characteristics of inhomogeneous Schottky diodes have been generated by using analytically solved thermionic-emission diffusion equation incorporating Gaussian distribution of barrier heights and by direct numerical integration over a barrier height range. The differences in the results obtained in two approaches are discussed and it is shown that the two approaches yield current-voltage characteristics with slightly different features. The discrepancies in the results obtained in two approaches are attributed to the same series resistance assumed for all elementary barriers of the distribution. It is shown that assigning same series resistance to all barrier of the distribution in numerical integration approach causes current saturation at low bias and inhibits intersection of current-voltage curves from being observable which otherwise occurs in the curves obtained using analytical equation. The paper deals with these aspects in details.     

Effect of POSS on crystalline transitions and physical properties of polyamide 12

Polyamide 12/Trisilanolphenyl‐POSS (PA 12/POSS) composites were prepared via melt‐compounding. The effect of polyhedral oligomeric silsesquioxane (POSS) on crystalline structure and crystalline transition of PA 12 was investigated by wide‐angle X‐ray diffraction (WAXD) and real time fourier transform infrared spectroscopy (FTIR). WAXD results indicated that PA 12 crystallized into γ‐form as slowly cooling from melt and the presence of POSS did not influence the crystalline structure of PA 12. Both PA 12 and PA 12/POSS composites underwent Brill transitions when they were heated from room temperature to melt point. Real time FTIR patterns showed that an absorption band at 697 cm^?1 ascribed to Amide V (α) mode was emerged along with the disappearance of Amide VI (γ) band at 628 cm^?1 with the increase of the temperature for PA 12 and PA 12/POSS composites, which suggested that the γ‐form crystalline has transformed into α form. The Brill bands were identified and the transformed mechanism was discussed based on the real FTIR results. The addition of POSS enhanced the tensile strength and thermal stability of PA 12. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 121–129, 2009