Untersuchungen über den Anteil der Ofenschlacke am Gesamtgehalt an nichtmetallischen Einschlüssen in Stahl durch Markierung der Schlacke mit 90Y

Um die aus der Ofenschlacke in den Stahl gelangenden Einschlüsse zu bestimmen und auch auf Grund der thermodynamischen und kernphysikalischen Eigenschaften wurde des Radionuklid ⁹⁰Y ausgewählt. Es wird die Untersuchungsmethode beschrieben, die Art und Weise der Einführung des mit ⁹⁰Y markierten Y₂O₃ in die Ofenschlacke, die Schmelztechnologie, die Entnahme und chemische Behandlung der Proben und die Messung der Radioaktivität. Die für Kugellager-und Schienenstahl erhaltenen Versuchsergebnisse werden erörtert.     

Light transfer problem in turbid media with surface reflectivity

Light transfer problems in turbid media with surface reflectivity satisfying Fresnel's law are formulated. The intensity of light is considered as a sum of collimated and diffuse radiances. The problem with a collimated source and boundary conditions with surface reflectivity is solved in terms of the corresponding source-free problem with simple boundary conditions. In order to solve the source-free problem, two-flux models in the differential and integral forms are obtained. For the differential form, weight functions are introduced in order to force the boundary conditions to be met, while in the integral form the boundary conditions are embedded. The integral form has the advantage over the differential form that it permits one to extend the validity of the model and to consider inhomogeneous media. Numerical results are given for albedos and partial fluxes depending upon the refractive index of the medium. The calculations are performed in both semi-infinite and finite media and are compared with the published calculations.     

Electrogravitational instability of cylindrical interface acted upon by a varying electric field

The electrodynamic instability of a self-gravitating dielectric fluid penetrated by a uniform axial electric field surrounded by a self-gravitating vacuum pervaded by a varying electric field is investigated. A general eigenvalue relation valid to all possible (symmetric and asymmetric) modes of perturbation for all (short and long) wavelengths is derived and discussed in detail. The model is gravitationally stable to the pure asymmetric disturbances modes while to symmetric modes it is as if the longitudinal wavenumber normalized with respect to the jet radius is equal to or greater than 1.0668 and vice versa. The axial electric fields pervaded interior and exterior to the cylinder are stabilizing for all disturbances modes according to some restrictions. The transverse varying electric field is purely stabilizing in the symmetric disturbance for all wavelengths, while it is stabilizing in the asymmetric disturbance under some restrictions. The electrodynamic force has a strong stabilizing influence in the symmetric mode and can suppress the gravitational instability above a certain value of the basic electric field.     

Efficient synthesis of some novel furo[3,2-e]pyrazolo[3,4-b]pyrazines and related heterocycles

A series of novel 6-functionalized-5-amino-3-methyl-1-phenyl-1H-furo[3,2-e]pyrazolo[3,4-b]pyrazines (4a–c) was synthesized by the reaction of 3-methyl-6-oxo-1-phenyl-6,7-dihydro-1H-pyrazolo[3,4-b]pyrazine-5-carbonitrile (2) with α-halocarbonyl compounds such as: diethyl 2-bromomalonate, phenacyl bromide and chloroacetone. Cyclocondensation of the amino benzoyl 4b with diethyl malonate yielded the oxopyridine carboxylate derivative 5. Also, the starting intermediate amino ester compound 4a was allowed to react with ethanol amine to afford the hydroxyethyl caboxamide derivative 6. Furthermore, hydrazinolysis of the amino ester 4a afforded the corresponding amino carbohydrazide 7 which was used as a versatile precursor for synthesis of other heterocyclic compounds attached or fused to the furopyrazolopyrazine moiety. The chemical structures of the newly synthesized compounds were confirmed on the basis of elemental and spectral analyses containing FT-IR, ¹H NMR, ¹³C NMR, and mass spectrometry hoping these molecules should allow us to investigate their pharmacological activities in the future study.     

Use of charge-transfer complexation in the spectrophotometric analysis of certain cephalosporins

Three simple, rapid and sensitive spectrophotometric procedures were developed for the analysis of cephapirin sodium (1), cefazoline sodium (2), cephalexin monohydrate (3), cefadroxil monohydrate (4), cefotaxime sodium (5), cefoperazone sodium (6) and ceftazidime pentahydrate (7) in pure form as well as in their pharmaceutical formulations. The methods are based on the reaction of these drugs as n-electron donors with the σ-acceptor iodine, and the π-acceptors: 2,3-dichloro-5,6-dicyano-p-benzo-quinone (DDQ) and 7,7,8,8-tetracyanoquinodimethane (TCNQ). Depending on the solvent polarity, different coloured charge-transfer complexes and radicals were developed. Different variables and parameters affecting the reactions were studied and optimized. The obtained charge-transfer complexes were measured at 364 nm for iodine (in 1,2-dichloroethane), 460 nm for DDQ (in methanol) and 843 nm for TCNQ (in acetonitrile). Ultraviolet–visible, infrared and ¹H-nuclear magnetic resonance techniques were used to study the formed complexes. Due to the rapid development of colours at ambient temperature, the obtained results were used on thin-layer chromatograms for the detection of the investigated drugs. Beer's plots were obeyed in a general concentration range of 6–50, 40–300 and 4–24 μg ml⁻¹ with iodine, DDQ and TCNQ, respectively, with correlation coefficients not less than 0.9989. The proposed procedures could be applied successfully to the determination of the investigated drugs in vials, capsules, tablets and suspensions with good recovery; percent ranged from 96.47 (±1.14) to 98.72 (±1.02) in the iodine method, 96.35 (±1.62) to 98.51 (±1.30) in the DDQ method, and 95.98 (±0.78) to 98.40 (±0.87) in the TCNQ method. The association constants and standard free energy changes using Benesi–Hildebrand plots were studied. The binding of cephalosporins to proteins in relation to their molar absorptivities was studied.     

Periodic motions of spinning rigid spacecraft under influence of gravitational and magnetic fields

The motion of a magnetized axisymmetric spacecraft about its center of mass in a circular orbit is considered, taking the gravitational and magnetic effects of the central body into account. Equations of motion of the reduced system are transformed to equations of plane motion of a charged particle under the action of electric and magnetic fields. Stationary motions of the system are determined and periodic motions near to them are constructed using the Lyapounoff theorem of the holomorphic integral.     

Reliability evaluation of multi-state consecutive k-out-of-r-from-n: G system

This paper proposes a model that generalizes the linear consecutive k-out-of-r-from-n: G system to multi-state case. In this model the system consists of n linearly ordered multi-state components. Both the system and its components can have different states: from complete failure up to perfect functioning. The system is in state j or above if and only if at least k_j components out of r consecutive are in state j or above. An algorithm is provided for evaluating reliability of a special case of multi-state consecutive k-out-of-r-from-n: G system. The algorithm is based on the application of the total probability theorem and on the application of a special case taken from the [Jinsheng Huang, Ming J. Zuo, Member IEEE and Yanhong Wu, Generalized multi-state k-out-of-n: G system, IEEE Trans. Reliab. 49(1) (2000) 105–111.]. Also numerical results of the formerly published test examples and new examples are given.     

The influence of the d-core states on the calculation of the crystal structure of Zn with the optimized model potential

Shaw model potential has been used to calculate the structural energies of Zn using different model potential parameters. The effects of changing the model potentials, of using energy-wavenumber characteristics calculated with intervals of q/2k_F = 0.05 and 0.025, and of using different interpolation methods on the structural energies are investigated.