Showing papers by "Moscow State University published in 2003"

The Magnetocaloric Effect and its Applications

Abstract: Introduction Theory Magnetocaloric effect in the phase transition region Methods of investigation of magnetocaloric properties Magnetocaloric effect in 3d metals and their alloys Magnetocaloric effect in amorphous materials Magnetocaloric effect in rare earth metals and their alloys Magnetocaloric effect in intermetallic compounds with rare earth elements Magnetocaloric effect in oxide compounds Magnetocaloric effect in silicides and germanides Magnetocaloric effect in nanosized materials Magnetic refrigeration Conclusions

A Survey on Pixel-Based Skin Color Detection Techniques

Abstract: Skin color has proven to be a useful and robust cue for face detection, localization and tracking. Image content filtering, content-aware video compression and image color balancing applications can also benefit from automatic detection of skin in images. Numerous techniques for skin color modelling and recognition have been proposed during several past years. A few papers comparing different approaches have been published [Zarit et al. 1999], [Terrillon et al. 2000], [Brand and Mason 2000]. However, a comprehensive survey on the topic is still missing. We try to fill this vacuum by reviewing most widely used methods and techniques and collecting their numerical evaluation results.

A nomenclature for restriction enzymes, DNA methyltransferases, homing endonucleases and their genes

Abstract: A nomenclature is described for restriction endonucleases, DNA methyltransferases, homing endonucleases and related genes and gene products. It provides explicit categories for the many different Type II enzymes now identified and provides a system for naming the putative genes found by sequence analysis of microbial genomes.

Fabrication and characterization of n-ZnO/p-AlGaN heterojunction light-emitting diodes on 6H-SiC substrates

Abstract: We report on the fabrication of n-ZnO/p-AlGaN heterojunction light-emitting diodes on 6H-SiC substrates. Hydride vapor phase epitaxy was used to grow p-type AlGaN, while chemical vapor deposition was used to produce the n-type ZnO layers. Diode-like, rectifying I-V characteristics, with threshold voltage ~3.2V and low reverse leakage current ~10(-7)A, are observed at room temperature. Intense ultraviolet emission with a peak wavelength near 389 mn is observed when the diode is forward biased; this emission is found to be stable at temperatures up to 500K and shown to originate from recombination within the ZnO.

Physical mechanisms of the therapeutic effect of ultrasound (a review)

Abstract: Therapeutic ultrasound is an emerging field with many medical applications. High intensity focused ultrasound (HIFU) provides the ability to localize the deposition of acoustic energy within the body, which can cause tissue necrosis and hemostasis. Similarly, shock waves from a lithotripter penetrate the body to comminute kidney stones, and transcutaneous ultrasound enhances the transport of chemotherapy agents. New medical applications have required advances in transducer design and advances in numerical and experimental studies of the interaction of sound with biological tissues and fluids. The primary physical mechanism in HIFU is the conversion of acoustic energy into heat, which is often enhanced by nonlinear acoustic propagation and nonlinear scattering from bubbles. Other mechanical effects from ultrasound appear to stimulate an immune response, and bubble dynamics play an important role in lithotripsy and ultrasound-enhanced drug delivery. A dramatic shift to understand and exploit these nonlinear and mechanical mechanisms has occurred over the last few years. Specific challenges remain, such as treatment protocol planning and real-time treatment monitoring. An improved understanding of the physical mechanisms is essential to meet these challenges and to further advance therapeutic ultrasound.

mreps: efficient and flexible detection of tandem repeats in DNA

Abstract: The presence of repeated sequences is a fundamental feature of genomes. Tandemly repeated DNA appears in both eukaryotic and prokaryotic genomes, it is associated with various regulatory mechanisms and plays an important role in genomic fingerprinting. In this paper, we describe mreps, a powerful software tool for a fast identification of tandemly repeated structures in DNA sequences. mreps is able to identify all types of tandem repeats within a single run on a whole genomic sequence. It has a resolution parameter that allows the program to identify 'fuzzy' repeats. We introduce main algorithmic solutions behind mreps, describe its usage, give some execution time benchmarks and present several case studies to illustrate its capabilities. The mreps web interface is accessible through http://www.loria.fr/mreps/.

Triple gene block: modular design of a multifunctional machine for plant virus movement.

Abstract: Many plant virus genera encode a ‘triple gene block’ (TGB), a specialized evolutionarily conserved gene module involved in the cell-to-cell and long-distance movement of viruses. The TGB-based transport system exploits the co-ordinated action of three polypeptides to deliver viral genomes to plasmodesmata and to accomplish virus entry into neighbouring cells. Although data obtained on both the TGB and well-studied single protein transport systems clearly demonstrate that plant viruses employ host cell pathways for intra- and intercellular trafficking of genomic nucleic acids and proteins, there is no integral picture of the details of molecular events during TGB-mediated virus movement. Undoubtedly, understanding the molecular basis of the concerted action of TGB-encoded proteins in transporting viral genomes from cell to cell should provide new insights into the general principles of movement protein function. This review describes the structure, phylogeny and expression of TGB proteins, their roles in virus cell-to-cell movement and potential influence on host antiviral defences.

Observation of an Exotic S = +1 Baryon in Exclusive Photoproduction from the Deuteron

Abstract: In an exclusive measurement of the reaction {gamma}d {yields} K{sup +} K{sup -} p n, a narrow peak that can be attributed to an exotic baryon with strangeness S = +1 is seen in the K{sup +}n invariant mass spectrum. The peak is at 1542 {+-} 5 MeV/c{sup 2} with a measured width of 21 MeV/c{sup 2} FWHM, equivalent to the experimental invariant mass resolution. The statistical significance of the peak is 5.3 {+-} 0.5 {sigma} for a Gaussian peak shape on top of a smooth background.

Taste preferences in fishes

Abstract: The fish gustatory system provides the final sensory evaluation in the feeding process. Unlike other vertebrates, the gustatory system in fish may be divided into two distinct subsystems, oral and extraoral, both of them mediating behavioural responses to food items brought in contact with the fish. The abundance of taste buds is another peculiarity of the fish gustatory system. For many years, morphological and electrophysiological techniques dominated the studies of the fish gustatory system, and systematic investigations of fish taste preferences have only been performed during the last 10 years. In the present review, basic principles in the taste preferences of fish are formulated. Categories or types of taste substances are defined in accordance with their effects on fish feeding behaviour and further mediation by the oral or extraoral taste systems (incitants, suppressants, stimulants, deterrents, enhancers and indifferent substances). Information on taste preferences to different types of substances including classical taste substances, free amino acids, betaine, nucleotides, nucleosides, amines, sugars and other hydrocarbons, organic acids, alcohols and aldehydes, and their mixtures, is summarised. The threshold concentrations for taste substances are discussed, and the relationship between fish taste preferences with fish systematic position and fish ecology is evaluated. Fish taste preferences are highly species-specific, and the differences among fish species are apparent when comparing the width and composition of spectra for both the stimulants and the deterrents. What is evident is that there is a strong similarity in the taste preferences between geographically isolated fish populations of the same species, and that taste preferences are similar in males and females, although at the individual level, it may vary dramatically among conspecifics. What is noteworthy is that taste responses are more stable and invariable for highly palatable substances than for substances with a low level of palatability. Taste preferences as a function of pH is analysed. There is a good correspondence between development of the gustatory system in fish ontogeny and its ability to discriminate taste properties of food items. There is also a correspondence between oral and extraoral taste preferences for a given species; however, there is no correlation between smell and taste preferences. Taste preferences in fish show low plasticity (in relation to the diet), appear to be determined genetically and seem to be patroclinous. Fish feeding motivation and various environmental factors like water temperature and pollutants such as heavy metals and low pH water may shift fish taste preferences. Comparisons between bioassay and electrophysiological data show that palatability is not synonymous with excitability in the gustatory system. The chemical nature of stimulants and deterrents in various hydrobionts is outlined. The significance of basic knowledge in fish taste preferences for aquaculture and fisheries is emphasised.

Variable responses to large-scale climate change in European Parus populations

Abstract: Spring temperatures in temperate regions have increased over the past 20 years and many organisms have responded to this increase by advancing the timing of their growth and reproduction. However, not all populations show an advancement of phenology. Understanding why some populations advance and others do not will give us insight into the possible constraints and selection pressures on the advancement of phenology. By combining two decades of data on 24 populations of tits (Parus sp.) from six European countries, we show that the phenological response to large-scale changes in spring temperature varies across a species' range, even between populations situated close to each other. We show that this variation cannot be fully explained by variation in the temperature change during the pre- and post-laying periods, as recently suggested. Instead, we find evidence for a link between rising temperatures and the frequency of second broods, which results in complex shifts in the laying dates of first clutches. Our results emphasize the need to consider links between different life-history parameters in order to predict the ecological consequences of large-scale climate changes.

Alpha-smooth muscle actin is crucial for focal adhesion maturation in myofibroblasts.

Abstract: Cultured myofibroblasts are characterized by stress fibers, containing alpha-smooth muscle actin (alpha-SMA) and by supermature focal adhesions (FAs), which are larger than FAs of alpha-SMA-negative fibroblasts. We have investigated the role of alpha-SMA for myofibroblast adhesion and FA maturation. Inverted centrifugation reveals two phases of initial myofibroblast attachment: during the first 2 h of plating microfilament bundles contain essentially cytoplasmic actin and myofibroblast adhesion is similar to that of alpha-SMA-negative fibroblasts. Then, myofibroblasts incorporate alpha-SMA in stress fibers, develop mature FAs and their adhesion capacity is significantly increased. When alpha-SMA expression is induced in 5 d culture by TGFbeta or low serum levels, fibroblast adhesion is further increased correlating with a "supermaturation" of FAs. Treatment of myofibroblasts with alpha-SMA fusion peptide (SMA-FP), which inhibits alpha-SMA-mediated contractile activity, reduces their adhesion to the level of alpha-SMA negative fibroblasts. With the use of flexible micropatterned substrates and EGFP-constructs we show that SMA-FP application leads to a decrease of myofibroblast contraction, shortly followed by disassembly of paxillin- and beta3 integrin-containing FAs; alpha5 integrin distribution is not affected. FRAP of beta3 integrin-EGFP demonstrates an increase of FA protein turnover following SMA-FP treatment. We conclude that the formation and stability of supermature FAs depends on a high alpha-SMA-mediated contractile activity of myofibroblast stress fibers.

Kindling fluorescent proteins for precise in vivo photolabeling

Abstract: Photobleaching of green fluorescent protein (GFP) is a widely used approach for tracking the movement of subcellular structures and intracellular proteins1,2,3. Although photobleaching is a powerful technique, it does not allow direct tracking of an object's movement and velocity within a living cell. Direct tracking becomes possible only with the introduction of a photoactivated fluorescent marker. A number of previous studies have reported optically induced changes in the emission spectra of fluorescent proteins4,5,6,7. However, the ideal photoactivated fluorescent marker should be a nonfluorescent tag capable of “switching on” (i.e., becoming fluorescent) in response to irradiation by light of a particular wavelength, intensity, and duration. In this report, we generated a mutant of Anemonia sulcata chromoprotein asCP8. The mutant protein is capable of unique irreversible photoconversion from the nonfluorescent to a stable bright-red fluorescent form (“kindling”). This “kindling fluorescent protein” (KFP1) can be used for precise in vivo photolabeling to track the movements of cells, organelles, and proteins. We used KFP1 for in vivo cell labeling in mRNA microinjection assays to monitor Xenopus laevis embryo development and to track mitochondrial movement in mammalian cells.

Shape memory ferromagnets

Abstract: In ferromagnetic alloys with shape memory large reversible strains can be obtained by rearranging the martensitic domain structure by a magnetic field. Magnetization through displacement of domain walls is possible in the presence of high magnetocrystalline anisotropy, when martensitic structure rearrangement is energetically favorable compared to the reorientation of magnetic moments. In ferromagnetic Heusler alloys Ni2+xMn1–xGa the Curie temperature exceeds the martensitic transformation temperature. The fact that these two temperatures are close to room temperature offers the possibility of magnetically controlling the shape and size of ferromagnets in the martensitic state. In Ni2+xMn1–xGa single crystals, a reversible strain of ~6% is obtained in fields of ~1 T.

Self-transformation of a powerful femtosecond laser pulse into a white-light laser pulse in bulk optical media (or supercontinuum generation)

Abstract: We present experimental and theoretical results on white-light generation in the filamentation of a high-power femtosecond laser pulse in water and atmospheric air. We have shown that the high spatio-temporal localization of the light field in the filament, which enables the supercontinuum generation, is sustained due to the dynamic transformation of the light field on the whole transverse scale of the beam, including its edges. We found that the sources of the supercontinuum blue wing are in the rings, surrounding the filament, as well as at the back of the pulse, where shock-wave formation enhanced by self-steepening takes place. We report on the first observation and demonstration of the interference of the supercontinuum spectral components arising in the course of multiple filamentation in a terawatt laser pulse. We demonstrate that the conversion efficiency of an initially narrow laser pulse spectrum into the supercontinuum depends on the length of the filament with high intensity gradients and can be increased by introducing an initial chirp.

Significance of skin flavonoids for UV‐B‐protection in apple fruits

Abstract: An attempt has been made to assess the UV-B-protective capacity of phenolic compounds accumulated In superficial structures of plants using apple fruit as a model. Two apple (Malus domestica Borkh.) cultivars (Braeburn and Granny Smith) differing in response to high fluxes of solar radiation were selected and exposed to increasing doses of UV-B radiation. The extent of UV-B-induced damage to photosystem II of apple skin correlated with its quercetin glycoside (but not anthocyanin) content. Granny Smith apples did not demonstrate a pronounced response to high sunlight In terms of the accumulation of phenolic substances in the skin and exhibited similar patterns of F o , F m , and F v /F m changes in the course of UV-B irradiation both on sun-exposed and shaded surfaces of a fruit. Unlike Granny Smith, Braeburn fruits were characterized by a significant accumulation of quercetin glycosides in sun-exposed skin, however, shaded skin contained these compounds In similar amounts to those in Granny Smith. Accordingly, photosystem II in sun-exposed skin of Braeburn apples was resistant to high doses of UV-B radiation (up to 97 kJ m -2 ), whereas the susceptibility of the photosynthetic apparatus in shaded skin of Braeburn to UV-B-induced damage was much higher and similar to that of both sun-exposed and shaded skin of Granny Smith fruits. Anthocyanins, at least in the amounts found in Braeburn, did not show an additional effect in UV-B protection.

RhoD regulates endosome dynamics through Diaphanous-related Formin and Src tyrosine kinase.

Abstract: Early endosomes move bidirectionally between the cell periphery and the interior through a mechanism regulated by the low molecular weight GTPase RhoD. Here, we identify a novel splice variant of human Diaphanous, hDia2C, which specifically binds to RhoD and is recruited onto early endosomes. Expression of RhoD and hDia2C induces a striking alignment of early endosomes along actin filaments and reduces their motility. This activity depends on the membrane recruitment and activation of c-Src kinase, thus uncovering a new role in endosome function. Our results define a novel signal transduction pathway, in which hDia2C and c-Src are sequentially activated by RhoD to regulate the motility of early endosomes through interactions with the actin cytoskeleton.

A function for novel uncoupling proteins: antioxidant defense of mitochondrial matrix by translocating fatty acid peroxides from the inner to the outer membrane leaflet

Abstract: It is hypothesized that mitochondrial uncoupling proteins operate as carriers of fatty acid peroxide anions. This is assumed to result in electrophoretic extrusion of such anions from the inner to the outer leaflet of the inner mitochondrial membrane, being driven by membrane potential (mitochondrial interior negative). In this way, the inner leaflet is ridded of fatty acid peroxides that otherwise can form very aggressive oxidants damaging mitochondrial DNA, aconitase, and other mitochondrial matrix-localized components of vital importance. The steady-state concentration the fatty acid peroxides is known to be low. This explains why UCP2, 3, 4, and 5 are present in small amounts usually insufficient to make a large contribution to the H+ conductance of the mitochondrial membrane.—Goglia, F., Skulachev, V. P. A function for novel uncoupling proteins: antioxidant defense of mitochondrial matrix by translocating fatty acid peroxides from the inner to the outer membrane leaflet.

Docosahexaenoic acid and arachidonic acid release in rat brain astrocytes is mediated by two separate isoforms of phospholipase A2 and is differently regulated by cyclic AMP and Ca2

Abstract: 1. Docosahexaenoic acid (DHA) and arachidonic acid (AA), polyunsaturated fatty acids (PUFAs), are important for central nervous system function during development and in various pathological states. Astrocytes are involved in the biosynthesis of PUFAs in neuronal tissue. Here, we investigated the mechanism of DHA and AA release in cultured rat brain astrocytes. 2. Primary astrocytes were cultured under standard conditions and prelabeled with [(14)C]DHA or with [(3)H]AA. Adenosine 5'-triphosphate (ATP) (20 micro M applied for 15 min), the P2Y receptor agonist, stimulates release of both DHA (289% of control) and AA (266% of control) from astrocytes. DHA release stimulated by ATP is mediated by Ca(2+)-independent phospholipase A(2) (iPLA(2)), since it is blocked by the selective iPLA(2) inhibitor 4-bromoenol lactone (BEL, 5 micro M) and is not affected either by removal of Ca(2+) from extracellular medium or by suppression of intracellular Ca(2+) release through PLC inhibitor (U73122, 5 micro M). 3. AA release, on the other hand, which is stimulated by ATP, is attributed to Ca(2+)-dependent cytosolic PLA(2) (cPLA(2)). AA release is abolished by U73122 and, by removal of extracellular Ca(2+), is insensitive to BEL and can be selectively suppressed by methyl arachidonyl fluorophosphonate (3 micro M), a general inhibitor of intracellular PLA(2) s. 4. Western blot analysis confirms the presence in rat brain astrocytes of 85 kDa cPLA(2) and 40 kDa protein reactive to iPLA(2) antibodies. 5. The influence of cAMP on regulation of PUFA release was investigated. Release of DHA is strongly amplified by the adenylyl cyclase activator forskolin (10 micro M), and by the protein kinase A (PKA) activator dibutyryl-cAMP (1 mM). In contrast, release of AA is not affected by forskolin or dibutyryl-cAMP, but is almost completely blocked by 2,3-dideoxyadenosine (20 micro M) and inhibited by 34% by H89 (10 micro M), inhibitors of adenylyl cyclase and PKA, respectively. 6. Other neuromediators, such as bradykinin, glutamate and thrombin, stimulate release of DHA and AA, which is comparable to the release stimulated by ATP. 7. Different sensitivities of iPLA(2) and cPLA(2) to Ca(2+) and cAMP reveal new pathways for the regulation of fatty acid release and reflect the significance of astrocytes in control of DHA and AA metabolism under normal and pathological conditions in brain.

Cavitation Bubble Cluster Activity in the Breakage of Kidney Stones by Lithotripter Shockwaves

Abstract: High-speed photography was used to analyze cavitation bubble activity at the surface of artificial and natural kidney stones during exposure to lithotripter shock waves in vitro. Numerous individual bubbles formed at the surface of stones, but these bubbles did not remain independent and combined with one another to form bubble clusters. Bubble clusters formed at the proximal end, the distal end, and at the sides of stones. Each cluster collapsed to a narrow point of impact. Collapse of the proximal cluster caused erosion at the leading face of the stone and the collapse of clusters at the sides of stones appeared to contribute to the growth of cracks. Collapse of the distal cluster caused minimal damage. We conclude that cavitation-mediated damage to stones was due not to the action of solitary bubbles, but to the growth and collapse of bubble clusters.

Centrosome positioning in interphase cells.

Abstract: The position of the centrosome is actively maintained at the cell center, but the mechanisms of the centering force remain largely unknown. It is known that centrosome positioning requires a radial array of cytoplasmic microtubules (MTs) that can exert pushing or pulling forces involving MT dynamics and the activity of cortical MT motors. It has also been suggested that actomyosin can play a direct or indirect role in this process. To examine the centering mechanisms, we introduced an imbalance of forces acting on the centrosome by local application of an inhibitor of MT assembly (nocodazole), and studied the resulting centrosome displacement. Using this approach in combination with microinjection of function-blocking probes, we found that a MT-dependent dynein pulling force plays a key role in the positioning of the centrosome at the cell center, and that other forces applied to the centrosomal MTs, including actomyosin contractility, can contribute to this process.

Molecular Weight Characteristics of Humic Substances from Different Environments As Determined by Size Exclusion Chromatography and Their Statistical Evaluation

Abstract: Recorded molecular weights (MWs) for humic substances (HS) range from a few hundred to millions of daltons. For purposes of defining HS as a specific class of chemical compounds, it is of particular importance to ascertain if this broad range of MWs can be attributed to actual variability in molecular properties or is simply an artifact of the analytical techniques used to characterize HS. The main objectives of this study were (1)to establish if a preferential range of MWs exists for HS and (2) to determine any consistent MW properties of HS. To reach the goal, we have undertaken an approach to measure under standardized conditions the MW characteristics of a large set of HS from different natural environments. Seventy-seven humic materials were isolated from freshwater, soil, peat, and coal, such that each possessed a different fractional composition: humic acid (HA), fulvic acid (FA), and a nonfractionated mixture of HA and FA (HF). Size exclusion chromatography (SEC) was used as the analytical technique to determine molecular weight characteristics. The MW distributions were characterized by number (Mn) and weight (Mw) average MW, and by polydispersity. The complete range of Mw values varied within 4.7-30.4 kDa. The maximum Mw values were observed for peat HF and soil HA, whereas the smallest weights were measured for river water HF. Maximum values of polydispersity (3.5-4.4) were seen for peat HF and soil HA, while much lower values (1.6-3.1) were found for all preparations isolated with XAD-resins. Statistical evaluation showed consistent Mw and Mn variations with the HS source, while polydispersity was mostly a function of the isolation procedure used. A conclusion was made that HS have a preferential range of MW values that could characterize them as a specific class of chemical compounds.

The Liouville–Arnold–Nekhoroshev theorem for non-compact invariant manifolds

Abstract: Under certain conditions, generalized action–angle coordinates can be introduced near non-compact invariant manifolds of completely and partially integrable Hamiltonian systems.