A bioeconomic model of a ratio-dependent predator-prey system and optimal harvesting

This paper deals with the problem of a ratio-dependent prey-predator model with combined harvesting. The existence of steady states and their stability are studied using eigenvalue analysis. Boundedness of the exploited system is examined. We derive conditions for persistence and global stability of the system. The possibility of existence of bionomic equilibria has been considered. The problem of optimal harvest policy is then solved by using Pontryagin’s maximal principle.     

Luminescence Properties of Eu3+ Complexes of Tripode and Tetrapode Ligands Containing 2,2′-Bipyridine Units

The Eu³⁺ complexes of the tripode and tetrapode ligands 1 and 2 , respectively, containing 2,2′-bipyridine coordinating units have been prepared. The UV absorption and luminescence spectra, lifetimes, and quantum yields have been measured under a variety of experimental conditions. The contributions of different paths to the decay of the luminescent excited state are evaluated, and the structures of the complexes are discussed on the basis of spectroscopic and photophysical data.     

Inventory of differential items selling at two shops under single management

Inventory of differential (both good and defective) items purchased in a lot for two shops under a single management is considered here. In the primary shop, the lot is received and separated, only good units are sold and shortages are allowed which are backlogged from the good units specially purchased at the beginning of the next cycle. The separated defective units are continuously trasnsferred and sold at a reduced price from the secondary shop. This inventory model is formulated and illustrated numerically for three scenarios depending upon the time periods of the shops.     

Dissolution of Ca3(AsO4)2 · 2H2O in the system CaOAs2O5H2O at 35, 40, 45 and 50°C and the related thermodynamic data

Calcium arsenate dihydrate is precipitated at pH 7.0 and its dissolution in aqueous solutions at temperatures of 35, 40, 45 and 50°C and a pH of between 3.0 and 8.0 is investigated. The thermodynamic parameters ΔG⁰, ΔS⁰ and ΔH⁰ for the process are evaluated. Temperature dependence of solubility is obtained by the equations ?log K_TCA = $\text{9078.138}\text{T}$ ? 34.0468 + 0.0821421 T     

Kinetics of base hydrolysis ofO-bonded pentaammineglycinatocobalt(III) and pentaammine-β-alaninatocobalt(III) ions

Transition Metal Chemistry - The kinetics and mechanism of the base hydrolysis ofO-bonded pentaammineglycinatocobalt(III) and pentaammine-β-alaninatocobalt(III) ions have been studied...     

Local-field effect near the surface of dipolar lattices

The local-field correction near the surface of a dipolar crystal has been studied by explicitly computing the non-retarded electric field produced by a finite array of classical point dipoles induced by a time-varying electric field. Crystals of simple cubic, f.c.c. and b.c.c. structures are considered, and results presented for the self-consitent dipole moment and the local electric field at a lattice point. The utility of the method and its possible applications are discussed.     

Unrestricted Hartree-Fock spin density distributions in nitro aromatic radical anions

The spin density distributions in the radical anions of nitrobenzene and some para substituted nitrobenzenes are calculated using the unrestricted Hatree-Fock formalism of Amos and Snyder. A parameter scheme which gives satisfactory account of the electronic transitions and molecular ionisation potentials of substituted benzenes (nitrobenzene, toluene, aniline, benzaldehyde and benzonitrile) is used for spin density calculations of the nitro radical anions. The importance of spin densities on neighbouring atoms on the hyperfine splitting of nitrogen atom is discussed. It is seen that although Karplus-Fraenkel theory gives a better estimate of¹⁴N splitting constant, the simple McConnell-type of relation is approximately valid for the nitro group-nitrogen. The--parameters for use with unrestricted Hartree-Fock spin densities for the prediction of nitrogen hyperfine couplings in nitro, amino and cyano groups are summarised.

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Zusammenfassung Die Spindichteverteilungen in den Radikalanionen des Nitrobenzols und einiger parasubstituierter Nitrobenzole werden mit Hilfe des UHF-Formalismus von Amos und Snyder berechnet. Zur Ermittlung der Spindichte der nitroaromatischen Radikalanionen wird ein Parameterschema benutzt, das zufriedenstellende Darstellung der Elektronenübergänge und der molekularen Ionisationspotentiale von substituierten Benzolen (Nitrobenzol, Toluol, Anilin, Benzaldehyd, Benzonitril) gestattet. Der Einfluß der Spins von benachbarten Atomen auf die Hyperfeinaufspaltung des Stickstoffatoms wird diskutiert. Es zeigt sich, daß zur näherungsweisen Beschreibung des Stickstoffs der Nitrogruppe eine einfache Gleichung des McCornell-Typs ausreicht, wenn auch die Karplus-Fraenkel-Theorie eine bessere Abschätzung der¹⁴N-Aufspaltungskonstanten ermöglicht. Die --Parameter, die zur Voraussage der Stickstoff-Hyperfeinkopplung in Nitro-, Amino- und Cyanogruppen mit Hilfe der UHF-Spindichten erforderlich sind, werden zusammengestellt.