Efficiency of successive compression of radio pulses in a chain of coupled resonators

Calculations are made of the efficiency and gain for the series compression of radio pulses in a chain of coupled resonators. Zh. Tekh. Fiz. 69, 118–119 (July 1999)     

Adsorption of Oligomers from Dilute Solutions on the Surface of Ferromagnetic Fillers

The adsorption of oligomers from their dilute solutions on the surfaces of dispersed barium and strontium oxide ferrites and of neodymium-iron-boron alloy was studied. The main thermodynamic functions of the system components were evaluated. The features of their variation were established.     

Electronic transport through a contact of a correlated quantum wire with leads of higher dimension

We study theoretically electronic transport through a contact of a quantum wire with 2D or 3D leads and find that if the contact is not smooth and adiabatic then the conduction is strongly suppressed below a threshold voltage V _T , while above V _T the dc current $ \bar I $ \bar I is accompanied by coherent oscillations of frequency f = $ \bar I $ \bar I /e. The effect is related to interelectronic repulsion and interaction of dc current with the Friedel oscillations near a sharp contact. In short conducting channels of length L < L ₀ ≅ ℏV _F /eV _T and at high temperatures T > T ₀ ≅ eV _T /k _B the effect is destroyed by fluctuations.     

ESR and fluorescence studies of Mn-doped Na2ZnP2O7 single crystal and glasses

X-band electron spin resonance (ESR) spectra and fluorescence measurements were performed on Mn-doped Na₂ZnP₂O₇ (NZPO) single crystal synthesized by the Czochralski pulling method and glasses synthesized by the quenching process. For the single crystal, ESR angular dependences were measured in both the zx and xy plans of the NZPO lattice. The fine and hyperfine structure parameters and g-factor values were determined by modelling the experimental spectra. Using the Newman superposition model, the resonating centres in the single crystal and powder (crushed from crystals) samples are assigned to Mn²⁺ ions substituting for both zinc and sodium. For the glass sample the analysis of the ESR data shows that Mn²⁺ ions substitute for the Na⁺ ions. These interpretations are confirmed by the fluorescence measurements with a unique broad red band for the glassy compound and the presence of two emission bands (green and red) in the case of the crystal sample.     

Waveguide bridge as an element for energy extraction from a resonant microwave compressor

We present the results of theoretical analysis of the operation of a waveguide bridge as a device for microwave-energy extraction and the data of experimental studies of 3-cm compressors with energy extraction through the bridge. We determine conditions under which the bridge can be used as an efficient output device capable of doubling the output pulsed power of the compressor. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 3, pp. 216–222, March 2008.     

Efficiency of sequential resonance compression of radio pulses

A study is made of the efficiency of forming high-power wide-band and ultrawide-band radio pulses by a sequence of resonance compression steps. An analysis is made of the compression of radio pulses with a rectangular envelope in a chain consisting of two or three compressors, and also in a chain where the output signal from the first stage has an exponential trailing edge and the other stages have rectangular envelopes. The maximum energy storage efficiency is determined for a cavity excited by a signal with an exponential trailing edge. Zh. Tekh. Fiz. 69, 131–133 (April 1999)     

Investigation of anticancer activity of macrocyclic Schiff bases by means of 4D-QSAR based on simplex representation of molecular structure

Influence of the molecular structure of macrocyclic pyridinophanes, their analogues and some other compounds on anticancer activity (Leukemia, central nervous system (CNS) cancer, prostate cancer, breast cancer, melanoma, non-small cell lung cancer, colon cancer, ovarian cancer, renal cancer) was investigated by means of a new 4D-QSAR approach based on the simplex representation of molecular structures (SiRMS). For all the investigated molecules, the 3D structural models were first created and the set of conformers (fourth dimension) was used. Each conformer was represented as a system of different simplexes (tetratomic fragments of fixed structure, chirality and symmetry). Statistic characteristics of the QSAR partial least squares (PLS) models were satisfactory (correlation coefficient r=0.990-0.861; cross-validation coefficient CVR=0.914-0.633). The molecular fragments increasing and decreasing anticancer activity were defined. This information may be useful for the design and direct synthesis of novel anticancer agents.     

On the excess current in microbridges S-c-S and S-c-N

By means of a microscopic theory we calculate the I-V curves of a superconductor-constriction-superconductor (S-c-S) bridge for V > and of a superconductor-constriction-normal metal (S-c-N) bridge for arbitrary voltages V. The analysis is carried out for arbitrary temperatures. An excess current on the I-V curves of both systems is shown to exist. Effect of microwave irradiation on the I-V curve of the S-c-N bridge is also investigated.     

Investigation of skin secretory peptidome of <Emphasis Type="Italic">Rana lessonae</Emphasis> frog by mass spectrometry

Amphibian skin secretion represents a cerain scientific interest as a source of biologically active natural peptides. In the present research skin peptidome of wide-spread European frog Rana lessonae (Camerano, 1882) was studied for the first time ever. Peptide sequencing was accomplished with Fourier transform ion cyclotron resonance mass spectrometer in collision-induced and electron capture dissociation modes. A portion of amphibian peptides contains intramolecular C-terminal disulfide cycle which obstructs mass spectrometric sequencing. Two methods were utilized to overcome this difficulty: reduction with dithiotreithol followed by thiol group alkylation and oxidation into sulfonic acid groups with performic acid. Integrated approach employed in the present study allowed the identification of 49 peptides (of 6 to 37 amino acid residues), including 19 novel species.