Showing papers by "Russian Academy of Sciences published in 1973"

The Retrieval of Harmonics from a Covariance Function

Abstract: Summary A new method for retrieving harmonics from a covariance function is introduced. The method is based on a theorem of Caratheodory about the trigonometrical moment problem. The relation between this method and the ‘maximum entropy’ spectral estimator is discussed, and the effect of a small addition of a noise component is investigated. A numerical example is discussed.

Fluorescence and the location of tryptophan residues in protein molecules

Abstract: — Fluorescence spectra of a number of native and denaturated proteins have been analysed, using spectral band width (ΔΛ), spectral maximum position (Λm), fluorescence quenching by external ionic quenchers, lifetime (b), and quantum yield (q) and its changes upon denaturation. The results enabled a model of fluorescence properties of tryptophan residues in the proteins to be substantiated by considering the existence of three discrete spectral classes, one buried in nonpolar regions of the protein (Λm 330–332 nm, ΔΛ= 48–49nm, q 0.11, τ= 2.1 ns) and two on the surface. One of the latter is completely exposed to water (Λm# 350–353 nm, ΔΛ= 59–61 nm, q# 0.2, τ= 5.4 ns); the other is in limited contact with water which is probably immobilized by bonding at the macromolecular surface (Λm# 340–342 nm, ΔΛ= 53–55 nm, q# 0.3, = 4.4 ns). Some quantitative predictions from the model, for (a) the fraction of fluorescence that is quenched by ionic quenchers, (b) the mean values of quantum yield, and (c) the mean values of fluorescence lifetime for various proteins, show good concordance with independent experimentally determined values.

Different conformations of double‐stranded nucleic acid in solution as revealed by circular dichroism

Abstract: Conformation of two-stranded DNA in H2O–methanol, H2O–ethanol, H2O–isopropanol, and H2O–dioxane solutions at different concentrations of alkaline ions has been studied with the aid of circular dichroism. The following conclusions are drawn: The conformation of DNA in H2O and H2O–methanol belongs to a family of B forms (B, C, T forms are the representatives of the family). The magnitude of the winding angle between adjacent base pairs (θ) is determined by the concentration and type of the cations. In H2O the cation action is nonspecific and leads to an increase in θ value. In 80% methanol the ions act specifically, Cs+ being to stabilize a form with a greater θ value, and Li+ being with a lesser one. The total θ change is likely within the limits of 33° ⩽ θ ⩽ 45°. At high content of ethanol, isopropanol, or dioxane (∼80%), but not with methanol, and in low ionic strength the conformation of DNA belongs to a family of A forms (A form is one of the members of the family) and is specified by the concentration and type of cation involved. The two-stranded regions of RNA in H2O are also of A type and winds with the rise of cation concentration. The range of θ variation is not narrower than 30° ⩽ θ 33°. The conformational transitions within the families (induced by ions) are of non-cooperative pattern, wheras the transitions between the families (induced by nonpolar component) are of cooperative pattern. The effect of cations, when specific, is discussed on the basis of steric correspondence between the width of DNA narrow groove and the size of a hydrated cation.

Relaxation polarization of PbMg 1/3Nb2/3O3(PMN)-A ferroelectric with a diffused phase transition

Abstract: Peculiarities of the dielectric properties of the compound PbMg 1/3 Nb2/3 O3(PMN) such as the relaxation character of the dielectric polarization, deviation of permeability from the Curie-Weiss law above the Curie temperature etc. have been discussed on the basis of the idea of a diffused phase transition. 1-6 A model has been proposed, in accordance with which the features of the dielectric properties PMN are explained by the relaxation of the polar regions surrounded with a non polar phase, with the number of relaxing regions dependent on temperature.

Chrome-rich garnets from the kimberlites of yakutia and their parageneses

Abstract: The chrome-rich magnesian garnets (6.6–18.9% Cr2O3) of kimberlitic concentrates and some peridotite xenoliths contain variable admixtures of CaO: from 0.69 to 26.0% (1.7–72% Ca-component). All the garnets both in respect of Ca and Cr-contents make up a continuous series. The variability in the Ca-content is caused by differences in paragenesis. Most of the Ca-poor pyropes are related to a paragenesis without clinopyroxene (mostly dunitic). Garnets rich in calcium are related to a paragenesis without entstatite. All the parageneses listed are of an ultramafic type, i.e. contain magnesian olivine. The solubility of knorringite—Mg3Cr2(Si3O12)—in kimberlitic garnets is possibly limited by pressure and does not exceed 50–60% mol.

Reactions of nucleic acids and nucleoproteins with formaldehyde.

Abstract: Publisher Summary This chapter discusses the three main reasons for the chemical modification of nucleic acids that are available on modifying agents. These agents are used for inactivations of various kinds, for directed functional changes of nucleic acids in vivo and for the elucidation, through resulting modification, of structural and functional characteristics peculiar to synthetic or native polynucleotides. Some of these agents are useful for one, two, or all three of these purposes. One of the few agents that serve all three of them is formaldehyde. It is widely used as an inactivator of viruses to obtain vaccines and is reported to exert a cytostatic (carcinostatic) effect. It is also one of the most promising mutagenic agents affecting multicellular organisms. Formaldehyde is used extensively in structural and functional studies of nucleic acids as an agent not so much for causing denaturation as for preventing renaturation, and as a fixator of nucleic acids and nucleoproteins in electron microscope and sedimentation investigations. Recently, some progress in the structural study of formaldehyde interaction products with nucleotides and nucleic acids has been made. The chapter emphasizes on the evidence for the formation of various structures and the molecular mechanisms of biological and other effects of formaldehyde.

On the descending control of the lumbosacral spinal cord from the "mesencephalic locomotor region".

Abstract: Continuous stimulation (60 c/s) of a region below the inferior coliculus can induce locomotion on the treadmill of precollicular, postmammilar cats. This study aims at revealing what changes occur in the spinal cord, when the “locomotor region” is stimulated. This stimulation enables the cat to walk if the treadmill is moved. After controlling the threshold for evoking good locomotion, the cats were curarized. Stimulation at a strength that evoked walking prior to curarization induced a depression of inhibitory short-latency reflex effects to α-motoneurones from cutaneous, and high threshold muscular afferents without changing the direct excitability of α-motoneurones. The threshold for evoking longlasting reciprocally organized discharges was lowered. The results suggest that the effects are induced by a slow fiber system, that releases the activity of the spinal stepping generating neurones. The results would be explained if the noradrenergic reticulospinal system was activated from the mesencephalic locomotor region.

Productivity and heat generation of fermentation under oxygen limitation

Abstract: The elemental balance equation of microbial growth on carbon substrate of generalized composition is given. Yield of dried bio-mass per oxygenYo is calculated. Yield per oxygenYo is found to be determined by two factors—carbon yieldy and the reducing power of substrate γs. The mode of dependence ofYo on these two quantities is studied. The energetic interpretation ofy and γs is given. The dependence ofYo ony and γs is shown to be equivalent to the dependence on a single factor, the energetie yield of growth η. Fermentor productivity increases with growth of η, the increase being directly proportional if η is not large (up to 25%) and becoming steeper if η is larger. The restrictions on a range of workable carbon yields during growth on various substrates are found. Metabolic heat generation of fermentor is shown to be proportional to oxygen consumption and to average 3.38 kcal per gram of O2 irrespective of substrate and microorganism used.

Intensities and other spectral parameters of infrared amide bands of polypeptides in the beta- and random forms.

Abstract: The intensities and other spectral parameters of the main components of infrared amide bands for the random and anti-parallel pleated sheet forms have been determined for poly-S-carbobenzoxymethylcysteine, poly-S-carboxymethylcysteine, polylysine and silk fibroin of Bombyx mori in heavy water solutions and in organic solvents Assuming that the optical spectra of these two types of structure are additive, the method was proposed for determining relative contents and molar absorption coefficients of amide I band Integral intensity and maximum frequency values of the main components of the amide I band for all the samples in the β-form turned out to be specific In contrast to this the integral intensity of the band of amide I in the random coil form varied within certain limits, while the main maximum frequency for all samples remained the same

On the feeding of some scleractinian corals with bacteria and dissolved organic matter

Abstract: Feeding expcrirnents were carried out with 6 species of common sclcractinian reef-building corals from reefs of the Bismarck Archipelago. Their ability to utilize planktonic bacteria and dissolved organic matter (protein hydrolyzate) as food was demonstrated by using radiocarbon, The amount of organic carbon assimilated per day by animals given labeled food at concentrations approaching those found in situ was equivalent to 10-20s of the carbon content of the polyp’s body. The rate of consumption and assimilation of some planktonic algae by corals was much lower. Corals could consume organic phosphorus bound in the cells of planktonic bacteria more actively than inorganic phosphate at the same concentration (several ,ug liter-l), The rate of consumption of phosphorus was 3 pg

Multiphoton Processes in Homopolar Diatomic Molecules

Abstract: Within the framework of time-dependent perturbation theory and the Born---Oppenheimer approximation, general expressions are derived for the cross sections of multiphoton processes induced by radiation acting on a homopolar diatomic molecule. A Morse-type model of potential-energy curves of excited electronic states is proposed which gives a good representation of true curves. The procedure used to evaluate the sums over intermediate states is described. The method is based on the use of the internuclear potential Green's functions obtained in closed form. Analytic expressions are derived for one-photon and two-photon cross sections. The results for higher-order processes are presented in a form which is convenient for numerical computation. As an illustration, the cross section for one-photon dissociation of $\mathrm{H}_{2}^{}{}_{}{}^{+}$ from the $v=0$ vibrational level is calculated as a function of wavelength. A comparison of cross sections calculated using the Morse-type model of potential curves with those using accurate wave functions of $\mathrm{H}_{2}^{}{}_{}{}^{+}$ shows a good precision of the model.

Distribution of temperature and emission measure in a steadily heated solar atmosphere

Abstract: The distribution of temperature and emission measure in the stationary heated solar atmosphere was found for the limiting cases of slow and fast heating, when either the gas pressure or the concentration are constant through the layer depth. Results are relevant to the conditions when the energy injected by waves or by non-thermal particles or in some different way quickly transforms into a thermal flux. Under these conditions the temperature distribution with depth is determined by radiation loss and thermal conductivity, and at any values of energy flux and plasma concentration it is characterized by two universal functions. One of them gives the relation between the energy flux and temperature at the region boundary: the other - the temperature run with the depth. This run is such that a considerable part of the energy is radiated by a thin transition region with a very large temperature gradient.

Effect of A‐factor on the growth of asporogenous mutants of Streptomyces griseus, not producing this factor

Abstract: A-factor C13H22O4 was shown to be not only the inductor of the biosynthesis of streptomycin in inactive mutants of Streptomyces griseus (Actinomyces streptomycini), but also the potent regulator of differentiation of the cells: it induces the formation of spores in asporogenous strains during their superficial and submerged growth. This is accompanied by morphological modifications in the course of growth of the colonies.

Electroless Deposition of Nickel‐Boron Alloys Mechanism of Process, Structure, and Some Properties of Deposits

Abstract: The conditions for electroless nickel‐boron plating, the process mechanism, and the structure of the alloys as‐plated and after annealing at 150°–700°C were investigated. A correlation of the mechanical and magnetic properties with the changes of phase structure was established.

The Typology of Morphological and Lexical Causatives

Abstract: The subject of this paper is the typology of the causative opposition V i : V i , where V i designates the constant s j (i.e., some state), and V j designates cs j (i.e., a state, but one which has already been caused). The verbs V i are non-causatives, and the verbs V j are their causatives. V i and V j are connected by a semantic derivation relation: V j is ‘formed’ from V i by adding an additional meaning c.