A mixed integer programming formulation for the 1-maximin problem

In this paper, I present a mixed integer programming (MIP) formulation for the 1-maximin problem with rectilinear distance. The problem mainly appears in facility location while trying to locate an undesirable facility. The rectilinear distance is quite commonly used in the location literature. Our numerical experiments show that one can solve reasonably large location problems using a standard MIP solver. We also provide a linear programming formulation that helps find an upper bound on the objective function value of the 1-maximin problem with any norm when extreme points of the feasible region are known. We discuss various extension alternatives for the MIP formulation.     

Über Chalkogenolate. 118. Kristall- und Molekülstruktur von Oxovanadin(V)-ethylxanthat

On Chalcogenolates. 118. Crystal and Molecular Structure of Oxovanadium(V) Ethylxanthate VO[S₂C? OC₂H₅]₃ crystallizes with Z = 8 in the monoclinic space group P2₁/n with cell dimensions a = 15.065(7) Å, b = 18.540(48) Å, c = 12.824(7) Å, = 99.31(7)°. The crystal and molecular structure has been determined from single crystal X-ray data at 20°C and refined to a conventional R of 0.045.     

A Rapid Spectrophotometric Method to Resolve Ternary Mixtures of Propyphenazone, Caffeine, and Acetaminophen in Tablets

Summary.  A simple and rapid derivative spectrophotometric assay procedure is described for the analysis of caffeine (1), acetaminophen (2), and propyphenazone (3) in tablet formulations. The concentration range of application is 5.0–25.0 μg·cm⁻³ for 2 and 3 and 1.0–5.0 μg·cm⁻³ for 1. The method involves the extraction of the drugs from tablets with 0.1 N H₂SO₄, filtration, appropriate dilution, and measurement of the fourth derivative absorbance values at zero crossing wavelengths of 230.0, 263.2, and 256.6 nm for 1, 2, and 3. As a reference method, a reversed phase HPLC procedure was developed. Commercially available tablets were analyzed; statistical comparison of the results with those obtained from the reference method showed good agreement. The derivative spectrophotometric method has the advantage of being simple, rapid, inexpensive, and easy to perform. Received April 18, 2001. Accepted (revised) June 5, 2001     

Surface characterization and H2S-sensing potential of iron molybdate particles produced by supercritical solvothermal method and subsequent oxidation

The mostly crystalline polymorph β-FeMoO₄ was prepared by solvothermal synthesis from organic precursors, followed by high temperature supercritical drying in an autoclave. Crystallization of the synthesized particles occurred during subsequent heat treatment at 350 °C, confirmed by X-ray diffraction pattern analysis. The presence of Fe³⁺ ions in the powder, both well-crystallized and amorphous after heat treatment at 500 °C, was confirmed by room temperature Mössbauer spectrum. Thick-film gas sensors were prepared by conventional hand coating of a paste, the Fe₂(MoO₄)₃ powder mixed with an α-terpineol-based solvent, over the Au electrodes. The response of the prepared sensors to H₂S gas in the low concentration range 1–10 ppm in air was investigated. Moderately fast response and recovery times were observed. The iron molybdate, produced at low temperature, may be successfully used in the preparation of a H₂S gas sensor.     

Optimization over the efficient set: Four special cases

Recently, researchers and practitioners have been increasingly interested in the problem (P) of maximizing a linear function over the efficient set of a multiple objective linear program. Problem (P) is generally a difficult global optimization problem which requires numerically intensive procedures for its solution. In this paper, simple linear programming procedures are described for detecting and solving four special cases of problem (P). When solving instances of problem (P), these procedures can be used as screening devices to detect and solve these four special cases.     

Synthesis of Flavin–Calix[4]arene Conjugate Derivatives

The synthesis of two new flavin substituted calix[4]arene derivatives, 9 and 10 , is described. The first flavin substituted calix[4]arene derivative 9 was synthesized by the reaction of 3‐methylalloxazine ( 5 ) with 25,27‐bis(3‐bromopropoxy)‐26,28‐dihydroxy‐5,11,17,23‐tetra(tert‐butyl)calix[4]arene ( 4 ) in high yield (92%). The other derivative 10 was prepared from 3‐methylalloxazine‐1‐acetic acid ( 7 ) and 25,27‐bis(3‐cyanopropoxy)calix[4]arene ( 3 ). All new compounds were characterized by a combination of FT‐IR and ¹H‐NMR spectroscopy, and elemental‐analysis techniques.     

ESR Characterization of Two Oxovanadium (IV) Schiff Base Complexes Derived from Tris(2-aminoethyl)amine

The compounds, C₂₁H₂₇N₄O₃(L¹) and C₂₁H₂₇N₇(L²), is a tripodal Schiff base that was obtained from the reaction of tris(2-aminoethyl)amine (tren) and furan-2-carbaldehyde and pyrole- 2- carbaldehyde. The tripodal Schiff bases and their oxovanadium complexes have been characterized on the basis of the results of the elemental analysis, magnetic susceptibility measurements and spectroscopic studies FT-IR, ¹H-NMR, UV–Vis, ESR, magnetic moment and thermal analysis (TGA). Job's method of continuous variation shows 3:2 metal to ligand ratio.