Showing papers by "Russian Academy of Sciences published in 1994"
TL;DR: The model exhibits a number of phenomena that are seen in vivo, including immunostimulation of tumor growth, "sneaking through" of the tumor, and formation of a tumor "dormant state".
789 citations
TL;DR: In this paper, the authors extended the ultrasound speckle tracking method to allow measurement of internal displacement and strain fields over a wide dynamic range of tissue motion, which should lead to enhanced contrast resolution in strain and elasticity images.
Abstract: Previous ultrasound speckle tracking methods have been extended, permitting measurement of internal displacement and strain fields over a wide dynamic range of tissue motion. The markedly increased dynamic range of this approach should lead to enhanced contrast resolution in strain and elasticity images. Results of experiments on gelatin-based, tissue equivalent phantoms show the capabilities of the method. >
739 citations
TL;DR: In this article, a low threshold, large T/sub o/ injection laser emission via zero-dimensional states in (InGa)As quantum dots is demonstrated, which are formed due to a morphological transformation of a pseudomorphic In/sub 0.5/Ga/sub0.5 /As layer.
Abstract: Low threshold, large T/sub o/ injection laser emission via zero-dimensional states in (InGa)As quantum dots is demonstrated. The dots are formed due to a morphological transformation of a pseudomorphic In/sub 0.5/Ga/sub 0.5/As layer. Laser diodes are fabricated with a shallow mesa stripe geometry.<
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734 citations
TL;DR: The stability of a new type of DNA mimic, peptide nucleic acid (PNA) in human blood serum, Eschericia coli and Micrococcus luteus extracts and nuclear and cytoplasmic extracts from mouse Ehrlich ascites tumor cells was investigated using HPLC analysis and is expected to have sufficient biostability to be used as a drug.
716 citations
TL;DR: Human hepatitis B virus core protein expressed in E. coli assembles into two sizes of particle, each containing 240 and 180 protein subunits, and their three-dimensional structures are determined by electron cryomicroscopy and image processing.
504 citations
TL;DR: The assignment of a family of tightly related proteins from lower and higher eukaryotes which are structurally and functionally similar to rabbit eRF are reported, concluding that the eRFl proteins are directly implicated in the termination of translation in eukARYotes.
Abstract: THE termination of protein synthesis in ribosomes is governed by termination (stop) codons in messenger RNAs and by polypeptide chain release factors (RFs). Although the primary structure of prokaryotic RFs and yeast mitochrondrial RF is established1–4, that of the only known eukaryotic RF (eRF)5 remains obscure. Here we report the assignment of a family of tightly related proteins (designated eRFl) from lower and higher eukaryotes which are structurally and functionally similar to rabbit eRF. Two of these proteins, one from human6 and the other from Xenopus laevis7 , have been expressed in yeast and Escherichia coli, respectively, purified and shown to be active in the in vitro RF assay. The other protein of this family, sup45 (supl) of Saccharomyces cerevisiae, is involved in omnipotent suppression during translation8–12. The amino-acid sequence of the eRFl family is highly conserved. We conclude that the eRFl proteins are directly implicated in the termination of translation in eukaryotes.
406 citations
TL;DR: In this article, the modification of the mean and fluctuating characteristics of a flat-plate boundary layer subjected to nearly isotropic free stream turbulence (FST) is studied experimentally using hot-wire anemometry.
Abstract: The modification of the mean and fluctuating characteristics of a flat-plate boundary layer subjected to nearly isotropic free stream turbulence (FST) is studied experimentally using hot-wire anemometry. The study is focussed on the region upstream of the transition onset, where the fluctuations inside the boundary layer are dominated by elongated flow structures which grow downstream both in amplitude and length. Their downstream development and scaling are investigated and the results are compared with those obtained by previous authors. This allows some conclusions about the parameters which are relevant for the modelling of the transition process. The mechanisms underlying the transition process and the relative importance of the Tollmien–Schlichting wave instability in this flow are treated in an accompanying paper (part 2 of the present report).
354 citations
TL;DR: In this article, it was shown that despite the van der Waals' forces being capable of increasing the elastic contact area between the ball and the plane, the force that is required to overcome the molecular forces arising when the contact is broken does not increase thereby.
335 citations
TL;DR: In this paper, a detailed spectroscopic characterization of GdVO4, a new laser crystal with high effective absorption and emission cross sections, has been carried out and the temperature dependences of lifetime, linewidths, and cross sections have been determined.
Abstract: We have carried out a detailed spectroscopic characterization of Nd: GdVO4, a new laser crystal with high effective absorption and emission cross sections. The accidental degeneracy of the upper4
F
3/2 laser level decreases the number of emission lines and creates -together with the anisotropic crystal field - high emission cross sections (7.6 × 10−19 cm2 at 1.06 µm and 300 K). In addition, the lines are strongly homogeneously broadened (1.6 nm for the 808.4 nm diode-laser pump transition). The temperature dependences of lifetime, linewidths, and cross sections have been determined. Slope efficiencies up to 57% with respect to the absorbed diode-laser pump power and output powers up to 0.8 W have been achieved at 1.06 µm from a 2 mm long crystal. Intracavity second-harmonic generation, using a KTP crystal, is demonstrated.
304 citations
276 citations
TL;DR: In this paper, 15 measurements of the solar neutrino flux have been made in a radiochemical 71Ga-71Ge experiment employing initially 30 t and later 57 t of liquid metallic gallium at the Baksan Neutrino Observatory between January 1990 and May 1992.
TL;DR: A new experimental approach to protein structure determination is suggested in which selection of functional mutants after random mutagenesis and analysis of correlated mutations provide sufficient proximity constraints for calculation of the protein fold.
Abstract: A method has been developed to detect pairs of positions with correlated mutations in protein multiple sequence alignments. The method is based on reconstruction of the phylogenetic tree for a set of sequences and statistical analysis of the distribution of mutations in the branches of the tree. The database of homology-derived protein structures (HSSP) is used as the source of multiple sequence alignments for proteins of known three-dimensional structure. We analyse pairs of positions with correlated mutations in 67 protein families and show quantitatively that the presence of such positions is a typical feature of protein families. A significant but weak tendency is observed for correlated residue pairs to be close in the three-dimensional structure. With further improvements, methods of this type may be useful for the prediction of residue--residue contacts and subsequent prediction of protein structure using distance geometry algorithms. In conclusion, we suggest a new experimental approach to protein structure determination in which selection of functional mutants after random mutagenesis and analysis of correlated mutations provide sufficient proximity constraints for calculation of the protein fold.
TL;DR: FDH is perhaps the most suitable model for investigating the general mechanism of catalysis involving hydride ion transfer, and is one of the most promising candidates for the development of so-called coenzyme regeneration systems.
Abstract: NAD(P)+-dependent dehydrogenases comprise a substantial and diverse group of proteins differing in structure and function. They catalyse a number of key metabolic steps and belong to one of the most extensively studied protein families. Nevertheless, the majority of mechanistic studies on NAD+-dependent dehydrogenases are still performed using only a few selected enzymes acting on carbonyl compounds: alcohol dehydrogenase (ADH), lactate dehydrogenase (LDH), malate dehydrogenase (MDH) and glyceraldehyde-3-phosphate dehydrogenase (GPDH). The biochemistry and structure of these NAD+-linked dehydrogenases have been extensively studied and reviewed over the past decades [1-8], leading to a number of important structural and mechanistic generalizations. One of the simplest examples of NAD+-dependent dehydrogenation of carbonyl compounds is the oxidation of formate anion to CO2, catalysed by NAD+-dependent formate dehydrogenase (FDH; EC 1.2.1.2). This reaction is devoid of proton release or abstraction steps, and entails cleavage of a single carbon-hydrogen bond in the substrate and formation of a single new one in the product. Thus FDH is perhaps the most suitable model for investigating the general mechanism of catalysis involving hydride ion transfer. In addition, FDH is one of the most promising candidates for the development of so-called coenzyme regeneration systems [9-11], and is at present applied on the laboratory and pilot scale in fine organic and asymmetrical synthesis for production of high-value-added products [12,13].
TL;DR: The sequence specificity of DnaK substrate binding has been studied using a peptide display library and results show that peptides enriched in internal hydrophobic residues are preferential DNAK substrates, and negatively charged peptides have poor affinity.
TL;DR: The importance of compressibility data for characterizing the hydration properties of solutes (particularly, proteins, nucleic acids, and their constituents), while describing how such data can be interpreted to gain insight into role that hydration can play in modulating the stability of and recognition between biologically important compounds is emphasized.
TL;DR: In this paper, the authors analyzed the properties of damage-resistant LiNbO3 crystals doped with Mg, Zn, or In. Damage resistance is due to an essential increase in the photoconductivity σp.
Abstract: We analyzed the properties of damage-resistant LiNbO3 crystals doped with Mg, Zn, or In. Damage resistance is due to an essential increase in the photoconductivity σp. In the first two compounds the increase in σp is most pronounced at concentrations exceeding certain thresholds (5.5 mol. % MgO or 7 mol. % ZnO in the congruent melt), whereas in In-doped crystals it occurs at any In concentration. The increase in σp is directly related to the reduction of the intrinsic defects NbLi because of their substitution by damage-resistant impurities. If an iron impurity is present, then an abrupt decrease in the capture cross section of Fe3+ acceptors at Mg or Zn concentrations higher than the threshold is responsible for the observed increase in σp.
TL;DR: Using dye-labelled primers, it was possible to quantitate, by automated fluorescence detection, the relative yields of X and Y -specific PCR products generated from mixtures of male and female DNA.
Abstract: Gender identification of forensic samples was determined by amplifying a segment of the X-Y homologous gene amelogenin. Using a single pair of primers spanning part of the first intron, 106 by and 112 by PCR products were generated from the X and Y homologues respectively, which were then resolved by agarose gel electrophoresis. This test enabled as little as 20 pg of DNA from severely degraded bones to be amplified and typed in a single tube reaction. Furthermore, using dye-labelled primers, it was possible to quantitate, by automated fluorescence detection, the relative yields of X and Y -specific PCR products generated from mixtures of male and female DNA. The versatility of this sex test was further demonstrated by co-amplifying with the HLA-DQA1 Amplitype kit in a combined gender/identity DNA test.
TL;DR: In this paper, the response of a metal/electroactive polymer film/solution system to a low-amplitude variation of electrode polarization is analyzed, taking account of both the electrodiffusion transport of electronic and ionic species in the bulk film and non-equilibrium heterogeneous charge transfer, namely electrons at the metal-film boundary and ions at the film-solution boundary.
TL;DR: Data clearly show a correlation between photoreceptor complement, visual pigment lambda max and depth, but question the hypothesis that there is a correlation of pigmentlambda max with water colour since, in contrast to oceanic waters, the maximum transmission of Baikal water is between 550 and 600 nm.
TL;DR: Methods of age determination of amphibians by counting annual layers in the bone tissue and data on longevity of amphibian (both anurans and urodeles) in nature are presented.
Abstract: Methods of age determination of amphibians by counting annual layers in the bone tissue and data on longevity of amphibians (both anurans and urodeles) in nature are presented. Age compositions of amphibian populations are discussed and their variations analysed.
TL;DR: In this paper, a review of the theory of electronic topological transitions from the very first paper until the recent achievements is made, where the authors describe possible topological siguularities in the electronic spectra of metals and the singularities of thermodynamic and transport properties of a metal in the vicinity of ETT, their fluctuations are discussed in details.
TL;DR: It is suggested that this new "partly folded" state of a protein molecule can be the equilibrium counterpart of the first kinetic intermediate of protein folding, formed within a few milliseconds, i.e., after the "burst" stage of folding.
Abstract: Guanidinium chloride- (GdmCl-) induced unfolding of beta-lactamase has been investigated by a combination of size-exclusion chromatography (SEC-FPLC) and usual optical methods. It has been shown that at low temperatures this protein unfolds through two equilibrium intermediates. The first of these intermediates is the molten globule state, while the other (which we have called a "partly folded" state) is less compact than the molten globule but much more compact than the unfolded state. It also preserves a substantial part of secondary structure of the native or molten globule state. We suggest that this new "partly folded" state of a protein molecule can be the equilibrium counterpart of the first kinetic intermediate of protein folding, formed within a few milliseconds, i.e., after the "burst" stage of folding.
TL;DR: A method for the fast measurement of the diffusion coefficients of both small and large molecules in thin capillaries is reported, which relies on Taylor-Aris dispersion theory and uses standard instrumentation for capillary zone electrophoresis.
Abstract: A method for the fast measurement of the diffusion coefficients of both small and large molecules in thin capillaries is reported. The method relies on Taylor-Aris dispersion theory and uses standard instrumentation for capillary zone electrophoresis. With this equipment, which consists of thin capillaries (50 to 100 micrometers in inner diameter), an injection system, detector ports, and computer data acquisition, a sample plug is pumped through the capillary at known velocity and the peak dispersion coefficient (D*) is measured. With the experimentally measured values of D* and flow velocity, and knowledge of the inner diameter of the capillary, the molecular diffusion coefficient (D) can be rapidly derived. For example, for ovalbumin a D value of 0.759 x 10-6 square centimeter per second is found versus a tabulated value of 0.776 x 10-6 square centimeter per second (error, 2 percent). For hemoglobin a D value of 0.676 x 10-6 square centimeter per second is obtained versus a literature value of 0.690 x 10-6 square centimeter per second (error, 1.5 percent).
TL;DR: In this paper, the results of measured internal strain and displacement fields from gel-based phantoms are compared with theoretical predictions of a linear elastic model, and some aspects of elasticity reconstruction based on measured displacement and strain fields are discussed.
Abstract: Evaluation of internal displacement and strain distributions in tissue under externally applied forces is a necessary step in elasticity imaging To obtain a quantitative image of the elastic modulus, strain and displacement fields must be measured with reasonable accuracy and inverted based on an accurate theoretical model of soft tissue mechanics In this paper, results of measured internal strain and displacement fields from gel-based phantoms are compared with theoretical predictions of a linear elastic model In addition, some aspects of elasticity reconstruction based on measured displacement and strain fields are discussed >
TL;DR: In this article, the experimental results, band structure calculations, and theoretical investigations carried out within the framework of the many-electron models of half-metallic ferromagnets (HMFs) are reviewed.
Abstract: The experimental results, band structure calculations, and theoretical investigations carried out within the framework of the many-electron models of half-metallic ferromagnets (HMFs) are reviewed. These materials have an energy gap for one of the spin projections at the Fermi level and represent a separate class of strong itinerant magnetic substances, which includes some of the Heusler alloys (for example, PtMnSb), CrO2, etc. Some HMFs and related systems are promising magnetic materials which have, in particular, unique magneto-optic properties. The theoretical interest in HMFs arises from a striking manifestation of nonquasiparticle (spin-polaron) effects; for example, in the spin polarisation of charge carriers and in the nuclear magnetic relaxation rate. Concepts developed in the theory of HMFs are shown to be applicable also to 'conventional' strong itinerant (band) magnetic materials, including the iron-group metals.
TL;DR: In this article, a review of the state-of-the-art models of fast ionisation waves (FIWs) and their properties and properties is presented. But the focus of the review was not on the acceleration, but on the properties of the wave front.
Abstract: An analysis of experimental and theoretical investigations is the basis of this state-of-art review of models of fast ionisation waves (FIWs) and of characteristics and properties of these waves. The attention is concentrated on waves with the maximum possible velocities of 109–2×1010 cm s–1 when the amplitudes of voltage pulses are 20–300 kV. At low and moderate pressures the reduced intensity of the electric field in the front of a wave is so high that the front becomes a moving source of a beam of high-energy electrons in which the current can reach several kiloamperes. At moderate pressures the high-energy electrons in the wave front overtake the front and cause preliminary ionisation of the gas ahead of the front. At low pressures these electrons determine mainly the mechanism of the motion of the front. At high pressures (in excess of 200 torr) the main source of such preionisation is the radiation emitted by the front. The high rate of filling of the discharge volume with a plasma, high electric fields and high energies of the electrons in the front, and the slight heating of the gas make fast ionisation waves attractive for applications.
TL;DR: In this article, a simple kinematical model for spiral waves in weakly excitable media is proposed, where the model is formulated in terms of the motion of curves with free ends.
TL;DR: It follows that N → U, N → MG and MG → U transitions in proteins are all of the ‘all‐or‐none’ type and the molten globule state of protein molecules is separated from the native and the unfolded state.
TL;DR: It is shown how the parametric portrait of the SEIR model tends to that of the SIR model when the latent period tends to zero.
Abstract: The bifurcations of the periodic solutions of SEIR and SIR epidemic models with sinusoidally varying contact rate are investigated. The analysis is carried out with respect to two parameters: the mean value and the degree of seasonality of the contact rate. The corresponding portraits in the two-parameter space are obtained by means of a numerical continuation method. Codimension two bifurcations (degenerate flips and cusps) are detected, and multiple stable modes of behavior are identified in various regions of the parameter space. Finally, it is shown how the parametric portrait of the SEIR model tends to that of the SIR model when the latent period tends to zero.