304 research outputs found

    A family of Nikishin systems with periodic recurrence coefficients

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    Suppose we have a Nikishin system of pp measures with the kkth generating measure of the Nikishin system supported on an interval \Delta_k\subset\er with Ξ”kβˆ©Ξ”k+1=βˆ…\Delta_k\cap\Delta_{k+1}=\emptyset for all kk. It is well known that the corresponding staircase sequence of multiple orthogonal polynomials satisfies a (p+2)(p+2)-term recurrence relation whose recurrence coefficients, under appropriate assumptions on the generating measures, have periodic limits of period pp. (The limit values depend only on the positions of the intervals Ξ”k\Delta_k.) Taking these periodic limit values as the coefficients of a new (p+2)(p+2)-term recurrence relation, we construct a canonical sequence of monic polynomials {Pn}n=0∞\{P_{n}\}_{n=0}^{\infty}, the so-called \emph{Chebyshev-Nikishin polynomials}. We show that the polynomials PnP_{n} themselves form a sequence of multiple orthogonal polynomials with respect to some Nikishin system of measures, with the kkth generating measure being absolutely continuous on Ξ”k\Delta_{k}. In this way we generalize a result of the third author and Rocha \cite{LopRoc} for the case p=2p=2. The proof uses the connection with block Toeplitz matrices, and with a certain Riemann surface of genus zero. We also obtain strong asymptotics and an exact Widom-type formula for the second kind functions of the Nikishin system for {Pn}n=0∞\{P_{n}\}_{n=0}^{\infty}.Comment: 30 pages, minor change

    Evolution of the Greater Caucasus Basement and Formation of the Main Caucasus Thrust, Georgia

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    Along the northern margin of the Arabia‐Eurasia collision zone in the western Greater Caucasus, the Main Caucasus Thrust (MCT) juxtaposes Paleozoic crystalline basement to the north against Mesozoic metasedimentary and volcaniclastic rocks to the south. The MCT is commonly assumed to be the trace of an active plate‐boundary scale structure that accommodates Arabia‐Eurasia convergence, but field data supporting this interpretation are equivocal. Here we investigate the deformation history of the rocks juxtaposed across the MCT in Georgia using field observations, microstructural analysis, U‐Pb and 40Ar/39Ar geochronology, and 40Ar/39Ar and (U‐Th)/He thermochronology. Zircon U‐Pb analyses show that Greater Caucasus crystalline rocks formed in the Early Paleozoic on the margin of Gondwana. Low‐pressure/temperature amphibolite‐facies metamorphism of these metasedimentary rocks and associated plutonism likely took place during Carboniferous accretion onto the Laurussian margin, as indicated by igneous and metamorphic zircon U‐Pb ages of ~330–310Β Ma. 40Ar/39Ar ages of ~190–135Β Ma from muscovite in a greenschist‐facies shear zone indicate that the MCT likely developed during Mesozoic inversion and/or rifting of the Caucasus Basin. A Mesozoic 40Ar/39Ar biotite age with release spectra indicating partial resetting and Cenozoic (<40Β Ma) apatite and zircon (U‐Th)/He ages imply at least ~5–8Β km of Greater Caucasus basement exhumation since ~10Β Ma in response to Arabia‐Eurasia collision. Cenozoic reactivation of the MCT may have accommodated a fraction of this exhumation. However, Cenozoic zircon (U‐Th)/He ages in both the hanging wall and footwall of the MCT require partitioning a substantial component of this deformation onto structures to the south.Plain Language SummaryCollisions between continents cause deformation of the Earth’s crust and the uplift of large mountain ranges like the Himalayas. Large faults often form to accommodate this deformation and may help bring rocks once buried at great depths up to the surface of the Earth. The Greater Caucasus Mountains form the northernmost part of a zone of deformation due to the ongoing collision between the Arabian and Eurasian continents. The Main Caucasus Thrust (MCT) is a fault juxtaposing old igneous and metamorphic (crystalline) rocks against younger rocks that has often been assumed to be a major means of accommodating Arabia‐Eurasia collision. This study examines the history of rocks along the MCT with a combination of field work, study of microscopic deformation in rocks, and dating of rock formation and cooling. The crystalline rocks were added to the margins of present‐day Eurasia about 330–310 million years ago, and the MCT first formed about 190–135 million years ago. The MCT is likely at most one of many structures accommodating present‐day Arabia‐Eurasia collision.Key PointsAmphibolite‐facies metamorphism and plutonism in the Greater Caucasus basement took place ~330–310Β MaThe Main Caucasus Thrust formed as a greenschist‐facies shear zone during Caucasus Basin inversion and/or rifting (~190–135Β Ma)The Main Caucasus Thrust may have helped facilitate a portion of at least 5–8Β km of basement exhumation during Arabia‐Eurasia collisionPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154626/1/tect21292-sup-0002-2019TC005828-ts01.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154626/2/tect21292-sup-0006-2019TC005828-ts05.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154626/3/tect21292_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154626/4/tect21292-sup-0003-2019TC005828-ts02.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154626/5/tect21292-sup-0005-2019TC005828-ts04.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154626/6/tect21292.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154626/7/tect21292-sup-0004-2019TC005828-ts03.pd

    Ladder operators and differential equations for multiple orthogonal polynomials

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    In this paper, we obtain the ladder operators and associated compatibility conditions for the type I and the type II multiple orthogonal polynomials. These ladder equations extend known results for orthogonal polynomials and can be used to derive the differential equations satisfied by multiple orthogonal polynomials. Our approach is based on Riemann-Hilbert problems and the Christoffel-Darboux formula for multiple orthogonal polynomials, and the nearest-neighbor recurrence relations. As an illustration, we give several explicit examples involving multiple Hermite and Laguerre polynomials, and multiple orthogonal polynomials with exponential weights and cubic potentials.Comment: 28 page

    Multipoint Schur algorithm and orthogonal rational functions: convergence properties, I

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    Classical Schur analysis is intimately connected to the theory of orthogonal polynomials on the circle [Simon, 2005]. We investigate here the connection between multipoint Schur analysis and orthogonal rational functions. Specifically, we study the convergence of the Wall rational functions via the development of a rational analogue to the Szeg\H o theory, in the case where the interpolation points may accumulate on the unit circle. This leads us to generalize results from [Khrushchev,2001], [Bultheel et al., 1999], and yields asymptotics of a novel type.Comment: a preliminary version, 39 pages; some changes in the Introduction, Section 5 (Szeg\H o type asymptotics) is extende

    ВлияниС Π½ΠΎΠΊΠ΄Π°ΡƒΠ½Π° ΠΊΠ°Π²Π΅ΠΎΠ»ΠΈΠ½Π°-1 Π½Π° Π±Π΅Π»ΠΊΠΎΠ²Ρ‹ΠΉ состав экстраклСточных Π²Π΅Π·ΠΈΠΊΡƒΠ», сСкрСтируСмых ΠΊΠ»Π΅Ρ‚ΠΊΠ°ΠΌΠΈ Π½Π΅ΠΌΠ΅Π»ΠΊΠΎΠΊΠ»Π΅Ρ‚ΠΎΡ‡Π½ΠΎΠ³ΠΎ Ρ€Π°ΠΊΠ° Π»Π΅Π³ΠΊΠΈΡ…

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    Background. Recent data show evidence that lipid rafts (LR) proteins could be involved in the formation of exosomes and the sorting of proteins that make up the exosomal cargo. Such data are available for flotillins, structural and functional components of flatted rafts. The presence of the main component of caveolar rafts, caveolin-1 (Cav-1), has been shown in exosomes produced by some cancer cells; however, its possible participation in the regulation of the protein composition of exosomes has not been studied previously.Materials and methods. Knockdown of Cav-1 by transduction of a lentiviral vector expressing precursors of short hairpin ribonucleic acid to Cav-1; isolation (by ultracentrifugation) and analysis (transmission electron microscopy, nanoparticle tracking analysis) of extracellular vesicles (EVs) from non-small cell lung cancer cells (NSCLC) H1299; analysis of proteins in cells and in EVs by immunoblotting.Results. Analysis of the effect of Cav-1 expression on the composition of EV proteins associated with exosome biogenesis revealed a decrease in the level of Alix and TSG101, an increase in the level of LR proteins and the absence of changes in the level of tetraspanin CD9.Β Conclusion. The obtained data demonstrate a Cav-1-dependent changes in the composition of EVs, indicating aΒ change in the ratio of vesicles formed by the various molecular mechanisms.Π’Π²Π΅Π΄Π΅Π½ΠΈΠ΅. Π”Π°Π½Π½Ρ‹Π΅ исслСдований послСдних Π»Π΅Ρ‚ ΡΠ²ΠΈΠ΄Π΅Ρ‚Π΅Π»ΡŒΡΡ‚Π²ΡƒΡŽΡ‚ ΠΎΒ Ρ‚ΠΎΠΌ, Ρ‡Ρ‚ΠΎΒ Π±Π΅Π»ΠΊΠΈ, входящиС в состав Π»ΠΈΠΏΠΈΠ΄Π½Ρ‹Ρ… Ρ€Π°Ρ„Ρ‚ΠΎΠ², ΠΌΠΎΠ³ΡƒΡ‚ Π±Ρ‹Ρ‚ΡŒ задСйствованы Π²Β Ρ„ΠΎΡ€ΠΌΠΈΡ€ΠΎΠ²Π°Π½ΠΈΠΈ экзосом ΠΈΒ ΠΎΡ‚Π±ΠΎΡ€Π΅ Π±Π΅Π»ΠΊΠΎΠ², входящих в состав экзосомального ΠΊΠ°Ρ€Π³ΠΎ. Π’Π°ΠΊΠΈΠ΅ Π΄Π°Π½Π½Ρ‹Π΅ ΠΏΠΎΠ»ΡƒΡ‡Π΅Π½Ρ‹ для флотиллинов, структурно-Ρ„ΡƒΠ½ΠΊΡ†ΠΈΠΎΠ½Π°Π»ΡŒΠ½Ρ‹Ρ… ΠΊΠΎΠΌΠΏΠΎΠ½Π΅Π½Ρ‚ΠΎΠ² плоских Ρ€Π°Ρ„Ρ‚ΠΎΠ². Для кавСолина-1 (Cav-1), основного ΠΊΠΎΠΌΠΏΠΎΠ½Π΅Π½Ρ‚Π° кавСолярных Ρ€Π°Ρ„Ρ‚ΠΎΠ², ΠΏΠΎΠΊΠ°Π·Π°Π½ΠΎ присутствиС в экзосомах Π½Π΅ΠΊΠΎΡ‚ΠΎΡ€Ρ‹Ρ… ΠΎΠΏΡƒΡ…ΠΎΠ»Π΅Π²Ρ‹Ρ… ΠΊΠ»Π΅Ρ‚ΠΎΠΊ, ΠΎΠ΄Π½Π°ΠΊΠΎ Π΅Π³ΠΎ Π²ΠΎΠ·ΠΌΠΎΠΆΠ½ΠΎΠ΅ участиС в рСгуляции Π±Π΅Π»ΠΊΠΎΠ²ΠΎΠ³ΠΎ состава экзосом Ρ€Π°Π½Π΅Π΅ нС исслСдовалось.ΠœΠ°Ρ‚Π΅Ρ€ΠΈΠ°Π»Ρ‹ ΠΈΒ ΠΌΠ΅Ρ‚ΠΎΠ΄Ρ‹. Нокдаун Cav-1 ΠΏΡ€ΠΎΠ²ΠΎΠ΄ΠΈΠ»ΠΈ ΠΌΠ΅Ρ‚ΠΎΠ΄ΠΎΠΌ трансдукции лСнтивирусного Π²Π΅ΠΊΡ‚ΠΎΡ€Π°, ΡΠΊΡΠΏΡ€Π΅ΡΡΠΈΡ€ΡƒΡŽΡ‰Π΅Π³ΠΎ ΠΏΡ€Π΅Π΄ΡˆΠ΅ΡΡ‚Π²Π΅Π½Π½ΠΈΠΊΠΎΠ² ΠΌΠ°Π»Ρ‹Ρ… ΡˆΠΏΠΈΠ»Π΅Ρ‡Π½Ρ‹Ρ… Ρ€ΠΈΠ±ΠΎΠ½ΡƒΠΊΠ»Π΅ΠΈΠ½ΠΎΠ²Ρ‹Ρ… кислот ΠΊΒ Cav-1. ЭкстраклСточныС Π²Π΅Π·ΠΈΠΊΡƒΠ»Ρ‹ (Π­ΠšΠ’) выдСляли ΠΈΠ·Β ΠΊΠ»Π΅Ρ‚ΠΎΠΊ Π»ΠΈΠ½ΠΈΠΈ Н1299 Π½Π΅ΠΌΠ΅Π»ΠΊΠΎΠΊΠ»Π΅Ρ‚ΠΎΡ‡Π½ΠΎΠ³ΠΎ Ρ€Π°ΠΊΠ° Π»Π΅Π³ΠΊΠΈΡ… ΠΌΠ΅Ρ‚ΠΎΠ΄ΠΎΠΌ Π΄ΠΈΡ„Ρ„Π΅Ρ€Π΅Π½Ρ†ΠΈΠ°Π»ΡŒΠ½ΠΎΠ³ΠΎ ΡƒΠ»ΡŒΡ‚Ρ€Π°Ρ†Π΅Π½Ρ‚Ρ€ΠΈΡ„ΡƒΠ³ΠΈΡ€ΠΎΠ²Π°Π½ΠΈΡ. ΠŸΡ€Π΅ΠΏΠ°Ρ€Π°Ρ‚Ρ‹ Π­ΠšΠ’ Π²Π΅Ρ€ΠΈΡ„ΠΈΡ†ΠΈΡ€ΠΎΠ²Π°Π»ΠΈ ΡΒ ΠΏΠΎΠΌΠΎΡ‰ΡŒΡŽ трансмиссионной элСктронной микроскопии (Π°Π½Π°Π»ΠΈΠ· Ρ€Π°Π·ΠΌΠ΅Ρ€Π° ΠΈΒ ΠΌΠΎΡ€Ρ„ΠΎΠ»ΠΎΠ³ΠΈΠΈ) ΠΈΒ ΠΌΠ΅Ρ‚ΠΎΠ΄ΠΎΠΌ Π°Π½Π°Π»ΠΈΠ·Π° Ρ‚Ρ€Π°Π΅ΠΊΡ‚ΠΎΡ€ΠΈΠΉ двиТСния наночастиц (срСднСразмСрноС распрСдСлСниС и концСнтрация). Для анализа ΡΠΊΠ·ΠΎΡΠΎΠΌΠ°Π»ΡŒΠ½Ρ‹Ρ… ΠΌΠ°Ρ€ΠΊΠ΅Ρ€ΠΎΠ² ΠΈΒ Cav-1 Π²Β ΠΊΠ»Π΅Ρ‚ΠΊΠ°Ρ… ΠΈΒ Π­ΠšΠ’ примСняли ΠΌΠ΅Ρ‚ΠΎΠ΄ ΠΈΠΌΠΌΡƒΠ½ΠΎΠ±Π»ΠΎΡ‚Ρ‚ΠΈΠ½Π³Π°.Π Π΅Π·ΡƒΠ»ΡŒΡ‚Π°Ρ‚Ρ‹. Анализ влияния экспрСссии Cav-1 на состав Π±Π΅Π»ΠΊΠΎΠ² Π­ΠšΠ’, ассоциированных с биогСнСзом экзосом, выявил сниТСниС уровня Alix ΠΈΒ TSG101, ΠΏΠΎΠ²Ρ‹ΡˆΠ΅Π½ΠΈΠ΅ уровня Π±Π΅Π»ΠΊΠΎΠ² Π»ΠΈΠΏΠΈΠ΄Π½Ρ‹Ρ… Ρ€Π°Ρ„Ρ‚ΠΎΠ² и отсутствиС ΠΈΠ·ΠΌΠ΅Π½Π΅Π½ΠΈΠΉ уровня тСтраспанина CD9.Π—Π°ΠΊΠ»ΡŽΡ‡Π΅Π½ΠΈΠ΅. ΠŸΠΎΠ»ΡƒΡ‡Π΅Π½Π½Ρ‹Π΅ Π΄Π°Π½Π½Ρ‹Π΅ Π΄Π΅ΠΌΠΎΠ½ΡΡ‚Ρ€ΠΈΡ€ΡƒΡŽΡ‚ Cav-1-зависимоС ΠΈΠ·ΠΌΠ΅Π½Π΅Π½ΠΈΠ΅ состава Π­ΠšΠ’, ΡΠ²ΠΈΠ΄Π΅Ρ‚Π΅Π»ΡŒΡΡ‚Π²ΡƒΡŽΡ‰Π΅Π΅ ΠΎΠ± ΠΈΠ·ΠΌΠ΅Π½Π΅Π½ΠΈΠΈ ΡΠΎΠΎΡ‚Π½ΠΎΡˆΠ΅Π½ΠΈΡ Π²Π΅Π·ΠΈΠΊΡƒΠ», ΠΎΠ±Ρ€Π°Π·ΠΎΠ²Π°Π½Π½Ρ‹Ρ… с ΠΏΠΎΠΌΠΎΡ‰ΡŒΡŽ Ρ€Π°Π·Π»ΠΈΡ‡Π½Ρ‹Ρ… молСкулярных ΠΌΠ΅Ρ…Π°Π½ΠΈΠ·ΠΌΠΎΠ².
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