1,725,848 research outputs found
Entrevista para Quintú Quimün con Andrey Nikulin
No full textAndrey Nikulin es coordinador del Núcleo Takinahaky de Formación Superior Indígena (Universidad Federal de Goiás, Brasil). Obtuvo su doctorado en lingüística en la Universidad de Brasilia en 2020 con una tesis dedicada al desarrollo diacrónico de las lenguas macro-ye, reconocida con una mención honrosa en el marco del premio Mary R. Haas. Sus líneas de investigación incluyen descripción y documentación del idioma chiquitano (Bolivia), lingüística histórica, fonética y fonología de las lenguas indígenas sudamericanas, sobre todo de las familias macro-ye, tupí, mataguaya, arahuaca, bororo y cahuapana.
Entrevista y edición a cargo de Cintia Carrió
Entrevista para Quintú Quimün con Andrey Nikulin
No full textAndrey Nikulin es coordinador del Núcleo Takinahakу̃ de Formación Superior Indígena (Universidad Federal de Goiás, Brasil). Obtuvo su doctorado en lingüística en la Universidad de Brasilia en 2020 con una tesis dedicada al desarrollo diacrónico de las lenguas macro-ye, reconocida con una mención honrosa en el marco del premio Mary R. Haas. Sus líneas de investigación incluyen descripción y documentación del idioma chiquitano (Bolivia), lingüística histórica, fonética y fonología de las lenguas indígenas sudamericanas, sobre todo de las familias macro-ye, tupí, mataguaya, arahuaca, bororo y cahuapana.
Entrevista y edición a cargo de Cintia Carrió
Nikulin involutions on K3 surfaces
No full textWe study the maps induced on cohomology by a Nikulin (i.e. a symplectic) involution on a K3 surface. We parametrize the 11-dimensional irreducible components of the moduli space of algebraic K3 surfaces with a Nikulin involution and we give examples of the general K3 surface in various components. We conclude with some remarks on Morrison-Nikulin involutions, these are Nikulin involutions which interchange two copies of E 8(-1) in the Néron Severi group
Aliterella vladivostokensis Sh. R. Abdullin, A. Yu. Nikulin, V. B. Bagmet et V. Yu. Nikulin 2021, sp. nov.
No full textAliterella vladivostokensis Sh.R. Abdullin, A.Yu. Nikulin, V.B. Bagmet et V.Yu. Nikulin sp. nov. (Fig. 1) Description: —Cells solitary, more commonly irregular or in rounded colonies with many cells (up to 32–64 or more), usually aggregated irregularly, extended (Fig. 1 A–C). Mucilage unstratified, colorless and firm, surrounding cells and colonies. Cells cylindrical 1.6–6.87 μm long, 1.17–5.85 μm wide, 1 to 1.75 × longer than wide (mean, 1.28 ×) (Fig. 1 C–D). Cells easily squeezing from colonies with pressure (Fig. 1 C). The chromatoplasm and centroplasm usually recognizable with light microscopy (Fig. 1 C–D). Cell contents blue-green, slightly granulated, or sometimes homogeneous. Reproduction by simple binary cell division in three or more planes. Holotype: —The dried biomass of authentic strain was deposited to the Herbarium of the Federal Scientific Center of East Asia Terrestrial Biodiversity, Russia (exsiccatum number VLA-CA-1212) as a holotype. Type locality: — RUSSIA. Primorsky Territory, Vladivostok, 43°10’21.4” N, 131°56’10.9” E, collected by Shamil R. Abdullin on August 7, 2018. The authentic strain VCA-43 (Vl15-3) is available in the culture collection of the Laboratory of Botany, Federal Scientific Center of East Asia Terrestrial Biodiversity, Russia. Habitat: —This cyanobacteria occurred in aerophytic habitat (on the concrete fence). Etymology: —The species epithet ‘ vladivostokensis ’ is derived from the type locality Vladivostok City. Molecular phylogeny and sequence analyses: —Results of the BLAST searches showed that the sequence of the 16S rRNA gene and internal transcribed spacer (ITS) region (1800 bp) in our strain was highly similar to those in other species of Aliterella, several uncultured bacterial clones, and Synechocystis sp. PCC 7509 (> 94.5%). When only the ITS region was compared, the similarity to Aliterella spp. was just above 85%. Such relatively low similarity percentages suggested that we were likely dealing with a new species. Phylogenetic analyses (ML and BI) clearly indicated that A. vladivostokensis was a member of the strongly supported (99/1.00; BP/PP; Fig. 2) Aliterella generic clade. Branching pattern between the clade members remained largely unresolved (Fig. 2). We observed the highest 16S rRNA sequence similarities based on p -distance analysis between our isolate and an uncultured bacterial clone (DQ532167) isolated from clean spacecraft assembly rooms where spacecrafts are assembled (99.5%; Table 1). A. antarctica (KU291459) and A. shaanxiensis (MH023997) were the most similar to each other among described Aliterella species, (99.1%). Since no ITS sequences were available for the uncultured bacterial clones resolved as members of the Aliterella clade (5 accessions), we only compared the percentage of sequence dissimilarity between aligned 16S–23S ITS regions for the described taxa and Synechocystis sp. PCC 7509 (6 accessions). The dissimilarity varied from 6.4% to 17.5% (11.6%–17.5% between A. vladivostokensis and the other species; Table 2). Comparison of ITS secondary structures of the D1–D1′ and Box-B helices showed that they have similar patterns of bulges and terminal loops (Fig. 3, 4). The D1–D1′ helix was almost invariant in length (65–67 bp) and structure with 42 conserved sites among Aliterella species (Fig. 3). In Synechocystis sp. PCC 7509 the helix was shorter (57 bp) due to the deletion in the terminal loop (Fig. 3). The basal part of the D1–D1′ helix consisted of a conservative 4-bp double-stranded region followed by the internal (bilateral) loop (positions 5–6 and from 55–57 to 61–63 in different Aliterella species; 5–6 and 47–53 in Synechocystis sp. PCC 7509) and side loop with a single unpaired base (position 51–52, position 43 for Synechocystis sp. PCC 7509). Substitutions in the bilateral loop (base change U → C at position 57) and in the side loop (A → C at position 51) differentiated A. vladivostokensis. The terminal loop of the helix consisted of five bp and also harbored a unique marker mutation for the new species (A → C at position 29). Most species had two internal loops in the central part of D1–D1′ helix with the exception of A. shaanxiensis, which had three loops and Synechocystis sp. PCC 7509 with the one loop. We found one compensatory base change (CBC) and five hemi-compensatory base changes (hCBCs) in our secondary structure models. While CBC (A-U → G-C) was shared between A. vladivostokensis and A. antarctica (at positions 19–42 in both cases), the hCBCs were attributed to A. atlantica (C-G → U-G, at position 22), A. antarctica (two substitutions C-G → U-G at positions 20 and 27), A. chasmolithica (G-C → G-U, at position 33; Fig. 3), and Synechocystis sp. PCC 7509 (C-G → U-G at position 13). The Box-B helix was more variable in both primary and secondary structure (53–62 bp, 29 conservative sites); therefore, homologous nucleotides were difficult to identify in some cases (Fig. 4). The middle part of the Box-B helix had two (A. atlantica) to four (A. vladivostokensis) mostly bilateral internal loops. Point mutations, mostly found in single stranded domains, and indels frequent in the basal part of the Box-B altered the bulges location between species. A base substitution G → U at position 11 in the Box-B disrupted nucleotides pairing that led to an additional internal loop formation in A. vladivostokensis sequence (Fig. 4). The Box-B helix in Synechocystis sp. PCC 7509 differed from those in other species in lacking conservative motive at the base of the helix and shorter terminal loop (5 vs. 7–9 bases; Fig. 4). We found one CBC in Synechocystis sp. PCC 7509 (A-U → U-G, at positions 3 and 29) and one hCBC in A. chasmolithica (A-U → G-U, at position 3).Published as part of Abdullin, Shamil R., Nikulin, Arthur Yu., Bagmet, Veronika B., Nikulin, Vyacheslav Yu. & Gontcharov, Andrey A., 2021, New cyanobacterium Aliterella vladivostokensis sp. nov. (Aliterellaceae, Chroococcidiopsidales), isolated from temperate monsoon climate zone (Vladivostok, Russia), pp. 221-233 in Phytotaxa 527 (3) on pages 223-227, DOI: 10.11646/phytotaxa.527.3.7, http://zenodo.org/record/575142
Projective orbifolds of Nikulin type
No full textWe study projective irreducible symplectic orbifolds of dimension four
that are deformations of partial resolutions of quotients of hyperk ̈ahler manifolds of
K3[2]-type by symplectic involutions; we call them orbifolds of Nikulin type. We first
classify those projective orbifolds that are really quotients, by describing all families
of projective fourfolds of K3[2]-type with a symplectic involution and the relation
with their quotients, and then study their deformations. We compute the Riemann–
Roch formula for Weil divisors on orbifolds of Nikulin type and using this we describe
the first known locally complete family of singular irreducible symplectic varieties as
double covers of special complete intersections (3, 4) in P
A reconstruction of Proto-Je fonology and lexicon
No full textNikulin Andrey. A reconstruction of Proto-Je fonology and lexicon / Andrey Nikulin// Вопросы языкового родства. - 2019. - № 2 (17). - С. 93-127
A phonologycal reconstruction of Proto-Cerrado (Je family)
No full textNikulin Andrey. A phonologycal reconstruction of Proto-Cerrado (Je family) [Электронный ресурс] / Andrey Nikulin// Вестник РГГУ. Серия "Филология. Вопросы языкового родства". - 2017. - № 3 (15). - С. 147-180
Explicit Nikulin configurations on Kummer surfaces
No full text16 pages, comments welcomeInternational audienceA Nikulin configuration is the data of disjoint smooth rational curves on a K3 surface. According to results of Nikulin, the existence of a Nikulin configuration means that the K3 surface is a Kummer surface, moreover the abelian surface from the Kummer structure is determined by the curves. A classical question of Shioda is about the existence of non isomorphic Kummer structures on the same Kummer K3 surface. The question was studied by several authors, and it was shown that the number of non-isomorphic Kummer structures is finite, but no explicit geometric construction of such structures was given. In a previous paper, we constructed explicitly non isomorphic Kummer structures on some Kummer surfaces. In this paper we generalise the construction to Kummer surfaces with a weaker restriction on the degree of the polarization and we describe some cases where the previous construction does not work
A phonologycal reconstruction of Proto-Cerrado (Je family)
No full textNikulin Andrey. A phonologycal reconstruction of Proto-Cerrado (Je family) [Электронный ресурс] / Andrey Nikulin// Вестник РГГУ. Серия "Филология. Вопросы языкового родства". - 2017. - № 3 (15). - С. 147-180
Construction of Nikulin configurations on some Kummer surfaces and applications
No full textInternational audienceA Nikulin configuration is the data of 16 disjoint smooth rational curves on a K3 surface. According to a well known result of Nikulin, if a K3 surface contains a Nikulin configuration C, then X is a Kummer surface X = Km(B) where B is an Abelian surface determined by C. Let B be a generic Abelian surface having a polarization M with M 2 = k(k + 1) (for k > 0 an integer) and let X = Km(B) be the associated Kummer surface. To the natural Nikulin configuration C on X = Km(B), we associate another Nikulin configuration C ; we denote by B the Abelian surface associated to C , so that we have also X = Km(B). For k ≥ 2 we prove that B and B are not isomorphic. We then construct an infinite order automorphism of the Kummer surface X that occurs naturally from our situation. Associated to the two Nikulin configurations C, C , there exists a natural bi-double cover S → X, which is a surface of general type. We study this surface which is a Lagrangian surface in the sense of Bogomolov-Tschinkel, and for k = 2 is a Schoen surface
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