Showing papers by "Moscow State University published in 2001"

Prussian Blue and Its Analogues: Electrochemistry and Analytical Applications

Abstract: This article reviews fundamental aspects of deposition, structure and electrochemistry of Prussian Blue and its analogues. Special attention is given to the metal hexacyanoferrates with potential analytical applications. Prussian Blue and its analogues as advanced sensing materials for nonelectroactive ions are discussed. In contrast to common ‘smart materials’, the sensitivity and selectivity of metal hexacyanoferrates to such ions is provided by thermodynamic background. Prussian Blue itself is recognized as the most advantageous low-potential transducer for hydrogen peroxide over all known systems. Both high sensitivity (ca. 1 A M−1 cm−2) and selectivity in relation to oxygen reduction are more than three orders of magnitude higher, than for platinum electrodes. Biosensors based on different transducing principles containing enzymes oxidases are compared, and the devices operated due to hydrogen peroxide detection with the Prussian Blue based transducer are shown to be the most advantageous ones. The future prospects of chemical and biological sensors based on metal hexacyanoferrates are outlined.

Optical properties and nondestructive estimation of anthocyanin content in plant leaves.

Abstract: Absorption and reflectance spectra of maple (Acer platanoides), cotoneaster (Cotoneaster alaunica), dogwood (Cornus alba) and pelargonium (Pelargonium zonale) leaves with a wide range of pigment content and composition were studied in visible and near-infrared spectra in order to reveal specific anthocyanin (Anth) spectral features in leaves. Comparing absorption spectra of Anth-containing and Anth-free leaves with the same chlorophyll (Chl) content, absorption spectra of Anth in leaves were derived. The main spectral feature of Anth absorption in vivo was a peak around 550 nm; the peak magnitude was closely related to Anth content. A quantitative nondestructive technique was developed to subtract Chl contribution to reflectance in this spectral region and retrieve Anth content from reflectance over a wide range of pigment content and composition. Anth reflectance index in the form ARI = (R550)-1 - (R700)-1, where (R550)-1 and (R700)-1 are inverse reflectances at 550 and 700 nm, respectively, allowed an accurate estimation of Anth accumulation, even in minute amounts, in intact senescing and stressed leaves.

Conversion of conventional gravitational-wave interferometers into quantum nondemolition interferometers by modifying their input and/or output optics

Abstract: The LIGO-II gravitational-wave interferometers (ca. 2006–2008) are designed to have sensitivities near the standard quantum limit (SQL) in the vicinity of 100 Hz. This paper describes and analyzes possible designs for subsequent LIGO-III interferometers that can beat the SQL. These designs are identical to a conventional broad band interferometer (without signal recycling), except for new input and/or output optics. Three designs are analyzed: (i) a squeezed-input interferometer (conceived by Unruh based on earlier work of Caves) in which squeezed vacuum with frequency-dependent (FD) squeeze angle is injected into the interferometer’s dark port; (ii) a variational-output interferometer (conceived in a different form by Vyatchanin, Matsko and Zubova), in which homodyne detection with FD homodyne phase is performed on the output light; and (iii) a squeezed-variational interferometer with squeezed input and FD-homodyne output. It is shown that the FD squeezed-input light can be produced by sending ordinary squeezed light through two successive Fabry-Perot filter cavities before injection into the interferometer, and FD-homodyne detection can be achieved by sending the output light through two filter cavities before ordinary homodyne detection. With anticipated technology (power squeeze factor e-2R=0.1 for input squeezed vacuum and net fractional loss of signal power in arm cavities and output optical train e*=0.01) and using an input laser power Io in units of that required to reach the SQL (the planned LIGO-II power, ISQL), the three types of interferometer could beat the amplitude SQL at 100 Hz by the following amounts μ≡sqrt[Sh]/sqrt[ShSQL] and with the following corresponding increase V=1/μ3 in the volume of the universe that can be searched for a given noncosmological source: Squeezed input —μ≃sqrt[e-2R]≃0.3 and V≃1/0.33≃30 using Io/ISQL=1. Variational-output—μ≃e*1/4≃0.3 and V≃30 but only if the optics can handle a ten times larger power: Io/ISQL≃1/sqrt[e*]=10. Squeezed varational —μ=1.3(e-2Re*)1/4≃0.24 and V≃80 using Io/ISQL=1; and μ≃(e-2Re*)1/4≃0.18 and V≃180 using Io/ISQL=sqrt[e-2R/e*]≃3.2.

Thermodynamics of the magnetocaloric effect

Abstract: The relationship between the behavior of the temperature-dependent heat capacity at constant pressure measured in different magnetic fields and the magnetocaloric effect in magnetic systems with and without discontinuous change of entropy is discussed. It is shown that the two are directly related to each other, and if the behavior of either property (i.e., the heat capacity or the magnetocaloric effect) is known, the general behavior of the second one can be predicted. The derived relationships are illustrated using several sets of experimental data and model examples.

Quantum detection by current carrying superconducting film

Abstract: We describe a novel quantum detection mechanism in the superconducting film carrying supercurrent. The mechanism incorporates growing normal domain and breaking of superconductivity by the bias current. A single photon absorbed in the film creates transient normal spot that causes redistribution of the current and, consequently, increase of the current density in superconducting areas. When the current density exceeds the critical value, the film switches into resistive state and generates the voltage pulse. Analysis shows that a submicron-wide film of conventional low temperature superconductor operated in liquid helium may detect single far-infrared photon. The amplitude and duration of the voltage pulse are in the millivolt and picosecond range, respectively. The quantitative model is presented that allows simulation of the detector utilizing this detection mechanism.

Developmental Dyslexia: An Update on Genes, Brains, and Environments

Abstract: The science of reading and developmental dyslexia has experienced spectacular advances during the last few years Five aspects of this research are discussed in the article (1) The holistic phenomenon of reading is complex Many lower-level psychological processes (eg, phonemic awareness, phonological decoding, ability to process stimuli rapidly and automatize this process, memory, ability to recognize words) contribute to a single act of reading Conceptualizing the complex process of reading through its partly overlapping but partly independent components--which contribute to, but do not fully explain, the holistic process of reading--provides an excellent model for understanding complex hierarchies of higher mental functions Those who master reading skills successfully and those who have difficulties doing so differ in a wide range of reading-related processes The central deficit experienced by poor readers appears to be related to phonological processing (a complex hierarchy of functions related to processing phonemes), whereas characteristics of automatization processes seem to moderate the reading outcome for people whose phonological skills are weak (2) There are new data addressing models of dyslexia in languages other than English The most fascinating finding is that the model implicating phonological deficit as central to dyslexia, and the lack of ability to automatize as leading to troubled reading, appears to be universal, regardless of the specific language However, there is an interaction effect between the characteristics of a particular language and the developmental model of dyslexia In phonologically more difficult languages (eg, English), the most pronounced weakness appears to occur in phonological processing, whereas in phonologically easier languages (eg, German), the crucial role in the manifestation of dyslexia is played by the lack of the skills needed to achieve automatization (3) There is abundant evidence that reading (ie, any single act of reading as well as reading as a holistic process) is "cooked" by the brain Although no unified brain map of reading has been developed, some specific areas of the brain have been implicated in different reading-related cognitive processes by different laboratories and on different samples (4) Indisputable evidence has been accumulated suggesting the involvement of the genome in developmental dyslexia As of now, specific regions of the genome have been identified as being intimately involved with a number of different reading-related processes Today the field of developmental dyslexia is the only area of genetic studies of human abilities and disabilities in which linkages to the genome have been robustly replicated in independent laboratories (5) Finally, evidence suggests that developmental dyslexia might be only one of the manifestations of a deep, underlying, anatomical syndrome The comorbidity of developmental dyslexia with both internalizing and externalizing behavioral disturbances, as well as with other learning disabilities, underscores the need for wide-ranging cognitive and behavioral approaches in the remediation programs offered to dyslexic children

Spatio-temporally resolved spectroscopic diagnostics of the barrier discharge in air at atmospheric pressure

Abstract: The technique of spatially resolved cross-correlation spectroscopy (CCS) is used to carry out diagnostic measurements of the barrier discharge (BD) in air at atmospheric pressure. Quantitative estimates for electric field strength E(x,t) and for relative electron density ne(x,t)/nemax are derived from the experimentally determined spatio-temporal distributions of the luminosity for the spectral bands of the 0-0 transitions of the second positive system of N2 (λ = 337.1 nm) and the first negative system of N2+ (λ = 391.5 nm). These results are used to test the validity of some physical models of electrical breakdown in a BD. The influence of the spatio-temporal structure of the discharge on the chemical kinetics of ozone synthesis is studied by means of a semi-empirical method based on the results of spatially resolved CCS measurements.

Focal adhesion features during myofibroblastic differentiation are controlled by intracellular and extracellular factors

Abstract: Transforming growth factor beta (TGFbeta), the most established promoter of myofibroblast differentiation, induces ED-A cellular fibronectin and alpha-smooth muscle actin expression in fibroblastic cells in vivo and in vitro. ED-A fibronectin exerts a permissive action for alpha-smooth muscle actin expression. A morphological continuity (called fibronexus), a specialized form of focal adhesion, has been described between actin stress fibers that contain alpha-smooth muscle actin, and extracellular fibronectin, which contains the ED-A portion, in both cultured fibroblasts and granulation tissue myofibroblasts. We have studied the development of these focal adhesions in TGFbeta-treated fibroblasts using confocal laser scanning microscopy, three-dimensional image reconstruction and western blots using antibodies against focal adhesion proteins. The increase in ED-A fibronectin expression induced by TGFbeta was accompanied by bundling of ED-A fibronectin fibers and their association with the terminal portion of alpha-smooth muscle actin-positive stress fibers. In parallel, the focal adhesion size was importantly increased, and tensin and FAK were neoexpressed in focal adhesions; moreover, vinculin and paxillin were recruited from the cytoplasmic pool into focal adhesions. We have evaluated morphometrically the length and area of focal adhesions. In addition, we have evaluated biochemically their content of associated proteins and of alpha-smooth muscle actin after TGFbeta stimulation and on this basis suggest a new focal adhesion classification, that is, immature, mature and supermature. When TGFbeta-induced alpha-smooth muscle actin expression was blocked by soluble recombinant ED-A fibronectin, we observed that the fragment was localised into the fibronectin network at the level of focal adhesions and that focal adhesion supermaturation was inhibited. The same effect was also exerted by the ED-A fibronectin antibody IST-9. In addition, the antagonists of actin-myosin contractility BDM and ML-7 provoked the dispersion of focal adhesions and the decrease of alpha-smooth muscle actin content in stress fibers of pulmonary fibroblasts, which constitutively show large focal adhesions and numerous stress fibers that contain alpha-smooth muscle actin. These inhibitors also decreased the incorporation of recombinant ED-A into fibronectin network. Our data indicate that a three-dimensional transcellular structure containing both ED-A fibronectin and alpha-smooth muscle actin plays an important role in the establishment and modulation of the myofibroblastic phenotype. The organisation of this structure is regulated by intracellularly and extracellularly originated forces.

Investigation of the mechanism for rapid heating of nitrogen and air in gas discharges

Abstract: A rapid heating of nitrogen-oxygen mixtures excited by gas discharges is investigated numerically with allowance for the following main processes: the reactions of predissociation of highly excited electronic states of oxygen molecules (which are populated via electron impact or via the quenching of the excited states of N2 molecules), the reactions of quenching of the excited atoms O(1 D) by nitrogen molecules, the VT relaxation reactions, etc. The calculated results adequately describe available experimental data on the dynamics of air heating in gas-discharge plasmas. It is shown that, over a broad range of values of the reduced electric field E/N, gas heating is maintained by a fixed fraction of the discharge power that is expended on the excitation of the electronic degrees of freedom of molecules (for discharges in air, ηE⋍28%). The lower the oxygen content of the mixture, the smaller the quantity ηE. The question of a rapid heating of nitrogen with a small admixture of oxygen is discussed.

Holarctic phylogeography of arctic charr (salvelinus alpinus l.) inferred from mitochondrial dna sequences

Abstract: This study evaluated mitochondrial DNA (mtDNA) sequence variation in a 552-bp fragment of the control region of Arctic charr (Salvelinus alpinus) by analyzing 159 individuals from 83 populations throughout the entire range of the complex. A total of 89 (16.1%) nucleotide positions were polymorphic, and these defined 63 haplotypes. Phylogenetic analyses supported the monophyly of the complex and assigned the observed haplotypes to five geographic regions that may be associated with different glacial refugia. Most notably, a formerly defined major evolutionary lineage (S. a. erythrinus) ranging from North America across the Arctic archipelago to the Eurasian continent has now been partitioned into the Arctic group and the newly identified Siberian group. The Beringian group, formed entirely by specimens assigned to S. malma (Dolly Varden), encompassed the area formerly assigned to S. a. taranetzi. The latter, due to a unique haplotype, became the basal member of the Arctic group. Overall, the S. alpinus complex reflects divergent evolutionary groups coupled with shallow intergroup differentiation, also indicated by an analysis of molecular variance that attributed 73.7% (P < 0.001) of the total genetic variance among groups. Time estimates, based on sequence divergence, suggest a separation of the major phylogeographic groups during early to mid-Pleistocene. In contrast, colonization of most of today's range started relatively recently, most likely late Pleistocene during the last retreat of ice sheets some 10,000–20,000 years ago. This time scale obviously is too shallow for detecting significant variation on a smaller scale using mtDNA markers. However, other studies using nuclear microsatellite DNA variation strongly suggested ongoing evolution within groups by revealing strong population-genetic substructuring and restricted gene flow among populations. Thus, Arctic charr could serve as a model organism to investigate the linkage between historical and contemporary components of phylogeographic structuring in fish, and, with a global perspective of the distribution of genetic variation as a framework, meaningful comparisons of charr studies at a smaller geographic scale will now be possible.

Immune challenge affects basal metabolic activity in wintering great tits

Abstract: The costs of exploiting an organism's immune function are expected to form the basis of many life-history trade-offs. However, there has been debate about whether such costs can be paid in energetic and nutritional terms. We addressed this question in a study of wintering, free-living, male great tits by injecting them with a novel, non-pathogenic antigen (sheep red blood cells) and measuring the changes in their basal metabolic rates and various condition indices subsequent to immune challenge. The experiment showed that activation of the immune system altered the metabolic activity and profile of immune cells in birds during the week subsequent to antigen injection: individuals mounting an immune response had nearly 9% higher basal metabolic rates, 8% lower plasma albumin levels and 37% higher heterophile-to-lymphocyte ratios (leucocytic stress indices) than sham-injected control birds. They also lost nearly 3% (0.5 g) of their body mass subsequent to the immune challenge. Individuals that mounted stronger antibody responses lost more mass during the immune challenge. These results suggest that energetic expenditures to immune response may have a non-trivial impact upon an individual's condition.

On regularity of transition probabilities and invariant measures of singular diffusions under minimal conditions

Abstract: Let A = (aij ) be a matrix-valued Borel mapping on a domain Ω ⊂ R d , let b = (bi ) be a vector field on Ω, and let LA, b ϕ = a ij ∂ x i ∂ xj ϕ + bi ∂ xi ϕ. We study Borel measures μ on Ω that satisfy the elliptic equation LA, b *μ = 0 in the weak sense: ∫ LA, b ϕ dμ = 0 for all ϕ ∈ C 0 ∞ (Ω). We prove that, under mild conditions, μ has a density. If A is locally uniformly nondegenerate, A ∈ H loc p, 1 and b ∈ L loc p for some p > d, then this density belongs to H loc p, 1. Actually, we prove Sobolev regularity for solutions of certain generalized nonlinear elliptic inequalities. Analogous results are obtained in the parabolic case. These results are applied to transition probabilities and invariant measures of diffusion processes.

Critical evaluation of stability constants of phosphonic acids (IUPAC Technical Report)

Abstract: Available experimental data on stability constants of proton and metal complexes for 10 phosphonic acids [methylphosphonic acid, 1-hydroxyethane-1,1-diylbisphosphonic acid, dichloromethylenebisphosphonic acid, aminomethanephosphonic acid, N-(phosphonomethyl)glycine, imino-N,N-bis(methylenephosphonic acid), N-methylamino-N,N-bis(methylenephosphonic acid), nitrilotris(methylenephosphonic acid), 1,2-diaminoethane-N,N,N',N'-tetrakis-(methylenephosphonic acid), and diethylenetriamine-N,N,N',N",N"-pentakis-(methylenephosphonic acid)], published in 1950-1997, have been critically evaluated. For the latter phosphonate, all the data are rejected, as well as protonation constants [HL]/[H][L] for three other ligands. Higher-quality data are selected and presented as "Recommended" and "Provisional".

Idempotent functional analysis: An algebraic approach

Abstract: This paper is devoted to Idempotent Functional Analysis, which is an “abstract” version of Idempotent Analysis developed by V. P. Maslov and his collaborators. We give a brief survey of the basic ideas of Idempotent Analysis. The correspondence between concepts and theorems of traditional Functional Analysis and its idempotent version is discussed in the spirit of N. Bohr's correspondence principle in quantum theory. We present an algebraic approach to Idempotent Functional Analysis. Basic notions and results are formulated in algebraic terms; the essential point is that the operation of idempotent addition can be defined for arbitrary infinite sets of summands. We study idempotent analogs of the basic principles of linear functional analysis and results on the general form of a linear functional and scalar products in idempotent spaces.

Chronology of the Holocene transgression at the North Siberian margin

Abstract: To establish a chronology of the Holocene transgression in Arctic Siberia, a total of 14 sediment cores from the Laptev Sea continental slope and shelf were studied covering the water depth range between 983 and 21 m. The age models of the cores were derived from 119 radiocarbon datings, which were all analyzed on marine biogenic calcite (mainly bivalve shells). The oldest shell sample was found at the slope and dates back to about 15.3 cal. ka, indicating that the time interval investigated starts prior to the onset of the meltwater pulse 1A (similar to 14.2 cal. ka) when global sea-level rose dramatically. The inundation history was reconstructed mainly on the basis of major changes in average sedimentation rates (ASR), but also other sedimentological parameters were incorporated. A diachronous reduction in ASR from the outer to the inner shelf region is recognized, which was related to the southward migration of the coastline as the primary sediment source. We estimate that the flooding of the 50-, 43-, and 31-m isobaths was completed by approximately 11.1, 9.8, and 8.9 cal. ka, and that Holocene sea-level highstand was approached near 5 cal. ka. Between these time intervals, sea level in the Laptev Sea rose by 5.4, 13.3, and 7.9 mm/year, respectively.

Physical properties of RCo2 Laves phases

Abstract: The large variety of magnetic phenomena observed in the Co based Laves phases are reviewed. Following the band structure calculations it is argued that the outstanding magnetic features of the RCo2 intermetallics are intimately related to the position of the Fermi level, which is near to a local peak in N(e). This is why the Co 3d-electron system reacts sensitively either to the molecular field of the R partner element or to the changes of external parameters such as a magnetic field or pressure. Magnetic, magnetoelastic and transport measurements of RCo2 compounds and related pseudobinaries such as R(Co1-xAlx)2 with R either magnetic or nonmagnetic rare earth element are shown and discussed. The conditions for the appearance of itinerant electron metamagnetism and spin fluctuations are outlined. In particular, the influences of spin fluctuations on physical properties, e.g. the susceptibility, thermal expansion and transport phenomena, are demonstrated.

Electron field emission for ultrananocrystalline diamond films

Abstract: Ultrananocrystalline diamond (UNCD) films 0.1–2.4 μm thick were conformally deposited on sharp single Si microtip emitters, using microwave CH4–Ar plasma-enhanced chemical vapor deposition in combination with a dielectrophoretic seeding process. Field-emission studies exhibited stable, extremely high (60–100 μA/tip) emission current, with little variation in threshold fields as a function of film thickness or Si tip radius. The electron emission properties of high aspect ratio Si microtips, coated with diamond using the hot filament chemical vapor deposition (HFCVD) process were found to be very different from those of the UNCD-coated tips. For the HFCVD process, there is a strong dependence of the emission threshold on both the diamond coating thickness and Si tip radius. Quantum photoyield measurements of the UNCD films revealed that these films have an enhanced density of states within the bulk diamond band gap that is correlated with a reduction in the threshold field for electron emission. In additio...

Single Molecule Rod-Globule Phase Transition for Brush Molecules at a Flat Interface

Abstract: The coexistence of two different conformational states in one molecule has been visualized by scanning force microscopy for a rod−globule transition of brush molecules adsorbed on a water surface. The transition, which occurred upon lateral compression of monolayers, was also examined theoretically by scaling analysis that proved its first-order character. The transition becomes less distinct with decreasing length of the side chains and finally vanishes below a certain critical value.

Borsuk's problem and the chromatic numbers of some metric spaces

Abstract: A detailed survey is given of various results pertaining to two well-known problems of combinatorial geometry: Borsuk's problem on partitions of an arbitrary bounded d-dimensional set of non-zero diameter into parts of smaller diameter, and the problem of finding chromatic numbers of some metric spaces. Furthermore, a general method is described for obtaining good lower bounds for the minimum number of parts of smaller diameter into which an arbitrary non-singleton set of dimension d can be divided as well as for the chromatic numbers of various metric spaces, in particular, and . Finally, some new lower bounds are proved for chromatic numbers in low dimensions, and new natural generalizations of the notion of chromatic number are proposed.