High-accuracy measurer of complex reflection coefficient of SHF transmission lines

We describe a new method of constructing a device for simultaneous measurement of the relative amplitude and phase difference of microwave signals, using complex phase manipulation of input signals. It is shown that systematic errors of measurement are significantly lower in the proposed amplitude and phase meter. Root-mean-square values are obtained for a system with nonideal elements. A block diagram of the device is presented and its principal characteristics are described. Institute of Radiophysics and Electronics, Armenian Academy of Sciences, Erevan. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 9, pp. 1182–1188, September, 1997.     

Six-coordinate nitrato complexes of iron(III) porphyrins

The interaction of tetrahydrofuran (THF) with thin films of the nitrato complexes Fe(III)(Por)(eta(2)-O(2)NO) [Por = meso-tetraphenylporphyrinato (TPP) and meso-tetratolylporphyrinato (TTP) dianion] at low temperature leads to the formation of the six-coordinate nitrato complex Fe(Por)(THF)(NO(3)), which was characterized by IR and UV-visible spectroscopies. Formation of the THF adduct was accompanied by nitrate linkage isomerization from bidentate to monodentate coordination. The iron(III) center remains in a high spin state in contrast with the previously observed low-spin nitratonitrosyl complex Fe(TPP)(NO)(eta(10-ONO(2)). Upon warming, THF dissociates to restore the initial five-coordinate bidentate nitrato complex.     

Interaction of nitrogen bases with iron-porphyrin nitrito complexes Fe(Por)(ONO) in sublimed solids

The reactions of the nitrogen Lewis bases (B) 1-methylimidazole (1-MeIm), pyridine (Py), and NH3 as gases with sublimed layers containing the 5-coordinate nitrito iron(III)-porphyrinato complexes Fe(Por)(eta1-ONO) (1) are described (Por = meso-tetraphenyl-porphyrinato or meso-tetra-p-tolyl-porphyrinato dianions). In situ FTIR and optical spectra are used to characterize the formation of the 6-coordinate nitro complexes formed by the reaction of 1 with B = 1-MeIm, Py, or NH3. These represent the first examples of 6-coordinate amino-nitro complexes with sterically unprotected iron-porphyrins. The interaction of ammonia with Fe(Por)(ONO) at 140 K initially led to the nitrito species Fe(Por)(NH3)(eta1-ONO), and this species isomerized to the nitro complexes Fe(Por)(NH3)(eta1-NO2) upon warming to 180 K. When the latter were warmed to room temperature under intense pumping, the initial nitrito complexes Fe(Por)(eta1-ONO) were restored. Assignments of vibrational frequencies for the coordinated nitro group in 6-coordinate iron-porphyrin complexes are given and confirmed using 15N-labeled nitrogen dioxide to identify characteristic infrared bands. For M(Por)(B)(NO2) complexes (M = Fe or Co), an inverse correlation between the net charge transfer from the axial ligand B to the nitro group and the value of Deltanu = nua(NO2) - nus(NO2) is proposed. These observations are discussed in the context of growing interest in potential physiological roles of nitrite ion reactions with ferro- and ferri-heme proteins.     

Microwave Polarimeter with Synchronous Recording of Stokes Parameters

We describe a new method for designing a polarimeter which estimates simultaneously the four polarization parameters of the measured microwave signal, using complex phase and amplitude modulation. It is shown that, by choosing an appropriate modulation law, one can reduce significantly the dependence of the accuracy of measurement of polarization parameters on the systematic error of the meter. A block diagram of the polarimeter is presented and its main characteristics are described.     

Reactions of nitrogen oxides with heme models. Spectral and kinetic study of nitric oxide reactions with solid and solute Fe(III)(TPP)(NO3)

The reaction(s) of nitric oxide (nitrogen monoxide) gas with sublimed layers containing the nitrato iron(III) complex Fe(III)(TPP)(eta(2)-O(2)NO) (1, TPP = meso-tetraphenyl porphyrinate(2)(-)) leads to formation of several iron porphyrin species that are ligated by various nitrogen oxides. The eventual products of these low-temperature solid-state reactions are the nitrosyl complex Fe(TPP)(NO), the nitro-nitrosyl complex Fe(TPP)(NO(2))(NO), and 1 itself, and the relative final quantities of these were functions of the NO partial pressure. It is particularly notable that isotope labeling experiments show that the nitrato product is not simply unreacted 1 but is the result of a series of transformations taking place in the layered material. Thus, the nitrato complex formed from solid Fe(TPP)(eta(2)-O(2)NO) maintained under a (15)NO atmosphere was found to be the labeled analogue Fe(TPP)(eta(2)-O(2)(15)NO). The reactivities of the layered solids are compared to the behaviors of the same species in ambient temperature solutions. To interpret the reactions of the labeled nitrogen oxides, the potential exchange reactions between N(2)O(3) and (15)NO were examined, and complete isotope scrambling was observed between these species under the reaction conditions (T = 140 K). Overall it was concluded from isotope labeling experiments that the sequence of reactions is initiated by reaction of 1 with NO to give the nitrato nitrosyl complex Fe(TPP)(eta(1)-ONO(2))(NO) (2) as an intermediate. This is followed by a reaction in the presence of excess NO that is equivalent to the loss of the nitrate radical NO(3)(*)( )()to give Fe(TPP)(NO) as another transient species. A plausible pathway involving NO attack on the coordinated nitrate of 2 resulting in the release of N(2)O(4) concerted with electron transfer to the metal center is proposed.     

Diffraction of a shear plane wave in a compound elastic space with a half-infinite crack parallel to the inhomogeneity line

Problems of stress wave propagation and diffraction in elastic inhomogeneous media are undoubtedly of interest to scientists from the viewpoint of investigation of fundamental laws of dynamic processes and of the use of the results in technical and technological applications. The paper deals with the dynamic contact problem of shear plane wave diffraction at the edge of a semi-infinite crack in a compound space consisting of two elastic half-spaces. The questions related to the onset of surface waves and the wave field behavior in far-field regions are also considered.     

An ideal integrator in a radiometer

Radio Physics and Electronics Institute, Armenian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 31, No. 8, pp. 903–906, August, 1988.     

Association of Molybdenum Ionic Species with Alumina Surface

The adsorption isotherms at 25, 45, and 65 degrees C of molybdenum solutions of concentration ranges between 10(-3) and 3x10(-2) M(Mo) (pH 4-5) on different alumina samples are investigated. The analysis is conducted using a modified Frumkin isotherm which takes a more realistic account of the lateral interaction between adsorbed species and considers that the adsorption takes place on the most basic OH groups on the surface of alumina. The results are discussed in view of the difference in solutions speciation, and the changes in the pH of the remaining supernatant solutions. The solution temperature, PZC of the used aluminas, the configuration of the basic OH groups on their surface, and the pore structure have been shown to intervene effectively. Copyright 2000 Academic Press.