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Articles de revues sur le sujet « Fibred threefold »

Auteur : Grafiati
Publié le 9 mars 2023
Mis à jour le 10 mars 2023

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1

Thompson, Alan. « Explicit Models for Threefolds Fibred by K3 Surfaces of Degree Two ». Canadian Journal of Mathematics 65, no 4 (1 août 2013) : 905–26. http://dx.doi.org/10.4153/cjm-2012-037-2.

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AbstractWe consider threefolds that admit a fibration by K3 surfaces over a nonsingular curve, equipped with a divisorial sheaf that defines a polarization of degree two on the general fibre. Under certain assumptions on the threefold we show that its relative log canonical model exists and can be explicitly reconstructed from a small set of data determined by the original fibration. Finally, we prove a converse to this statement: under certain assumptions, any such set of data determines a threefold that arises as the relative log canonical model of a threefold admitting a fibration by K3 surfaces of degree two.
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XU, JINSONG. « The third and fourth pluricanonical maps of threefolds of general type ». Mathematical Proceedings of the Cambridge Philosophical Society 157, no 2 (19 juin 2014) : 209–20. http://dx.doi.org/10.1017/s0305004114000267.

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AbstractFor a nonsingular projective threefold of general typeXover the field of complex numbers, we show that the fourth pluricanonical map ϕ4is not birational onto its image if and only ifXis birationally fibred by (1,2)-surfaces, provided that vol(X) ≥ 303. We also have similar characterization of birationality of ϕ3.
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HUNT, BRUCE. « K3-FIBERED CALABI–YAU THREEFOLDS II : SINGULAR FIBERS ». International Journal of Mathematics 10, no 07 (novembre 1999) : 871–96. http://dx.doi.org/10.1142/s0129167x99000379.

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Duneau, Michel, et Marc Audier. « Quasiperiodic packings of fibres with icosahedral symmetry ». Acta Crystallographica Section A Foundations of Crystallography 55, no 4 (1 juillet 1999) : 746–54. http://dx.doi.org/10.1107/s0108767399001142.

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Different icosahedral packings of fibres have been experimentally realized. A packing construction with straight fibres of the same circular cross section, only parallel to fivefold icosahedral axes and respecting the closest packing condition, is reported. Its characteristics of point-group symmetry and related two-dimensional tilings are analysed. But for determining unambiguously all the fibre positions it appears that a mathematical construction has to be made from the cut and projection of a five-dimensional space. Through such a method, the volume fraction of fibrous reinforcement in a composite material can be calculated. The related two-dimensional tiling can be proved to be different from a Penrose tiling. Finally, the characteristics of other icosahedral packings where fibres are parallel to threefold axes or to both threefold and fivefold axes are briefly discussed and a few further experiments on their elasticity properties and photonic band-gap structure are suggested.
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5

Colliot-Thélène, Jean-Louis, et Bruno Kahn. « Cycles de codimension 2 et H3 non ramifié pour les variétés sur les corps finis ». Journal of K-Theory 11, no 1 (février 2013) : 1–53. http://dx.doi.org/10.1017/is012009001jkt194.

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AbstractLet X be a smooth projective variety over a finite field $\mathbb{F}$. We discuss the unramified cohomology group H3nr(X, ℚ/ℤ(2)). Several conjectures put together imply that this group is finite. For certain classes of threefolds, H3nr(X, ℚ/ℤ(2)) actually vanishes. It is an open question whether this holds for arbitrary threefolds. For a threefold X equipped with a fibration onto a curve C, the generic fibre of which is a smooth projective surface V over the global field $\mathbb{F}$(C), the vanishing of H3nr(X, ℚ/ℤ(2)) together with the Tate conjecture for divisors on X implies a local-global principle of Brauer–Manin type for the Chow group of zero-cycles on V. This sheds new light on work started thirty years ago.
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6

ANDREAS, BJÖRN, GOTTFRIED CURIO et ALBRECHT KLEMM. « TOWARDS THE STANDARD MODEL SPECTRUM FROM ELLIPTIC CALABI–YAU MANIFOLDS ». International Journal of Modern Physics A 19, no 12 (10 mai 2004) : 1987–2014. http://dx.doi.org/10.1142/s0217751x04018087.

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We show that it is possible to construct supersymmetric three-generation models with the Standard Model gauge group in the framework of non-simply-connected elliptically fibered Calabi–Yau threefolds, without section but with a bi-section. The fibrations on a cover Calabi–Yau threefold, where the model has six generations of SU(5) and the bundle is given via the spectral cover description, use a different description of the elliptic fiber which leads to more than one global section. We present two examples of a possible cover Calabi–Yau threefold with a free involution: one is a fiber product of rational elliptic surfaces dP9; another example is an elliptic fibration over a Hirzebruch surface. We compute the necessary amount of chiral matter by "turning on" a further parameter which is related to singularities of the fibration and the branching of the spectral cover.
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7

BARJA, MIGUEL A. « LOWER BOUNDS OF THE SLOPE OF FIBRED THREEFOLDS ». International Journal of Mathematics 11, no 04 (juin 2000) : 461–91. http://dx.doi.org/10.1142/s0129167x00000234.

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We study from a geographical point of view fibrations of threefolds over smooth curves f:T→B such that the general fibre is of general type. We prove the non-negativity of certain relative invariants under general hypotheses and give lower bounds for [Formula: see text] depending on other relative invariants. We also study the influence of the relative irregularity q(T)-g(B) on these bounds. A more detailed study of the lowest cases of the bounds is given.
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8

Szendrői, Balázs. « Sheaves on Fibered Threefolds and Quiver Sheaves ». Communications in Mathematical Physics 278, no 3 (8 janvier 2008) : 627–41. http://dx.doi.org/10.1007/s00220-007-0408-y.

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9

Oguiso, Keiji. « On certain rigid fibered Calabi-Yau threefolds ». Mathematische Zeitschrift 221, no 1 (janvier 1996) : 437–48. http://dx.doi.org/10.1007/bf02622125.

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10

Oguiso, Keiji. « On certain rigid fibered Calabi–Yau threefolds ». Mathematische Zeitschrift 221, no 3 (15 mars 1996) : 437–48. http://dx.doi.org/10.1007/pl00004519.

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11

Doran, C. F., A. Harder, A. Y. Novoseltsev et A. Thompson. « Calabi–Yau threefolds fibred by mirror quartic K3 surfaces ». Advances in Mathematics 298 (août 2016) : 369–92. http://dx.doi.org/10.1016/j.aim.2016.03.045.

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12

Pukhlikov, A. V. « Birational automorphisms of algebraic threefolds fibred by cubic surfaces ». Russian Mathematical Surveys 52, no 1 (28 février 1997) : 230–31. http://dx.doi.org/10.1070/rm1997v052n01abeh001758.

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13

GOTO, YASUHIRO, REMKE KLOOSTERMAN et NORIKO YUI. « ZETA-FUNCTIONS OF CERTAIN K3-FIBERED CALABI–YAU THREEFOLDS ». International Journal of Mathematics 22, no 01 (janvier 2011) : 67–129. http://dx.doi.org/10.1142/s0129167x11006726.

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We consider certain K3-fibered Calabi–Yau threefolds. One class of such Calabi–Yau threefolds is constructed by Hunt and Schimmrigk using twist maps. They are realized in weighted projective spaces as orbifolds of hypersurfaces. Our main goal of this paper is to investigate arithmetic properties of these K3-fibered Calabi–Yau threefolds. In particular, we give detailed discussions on the construction of these Calabi–Yau varieties, singularities and their resolutions. We then determine the zeta-functions of these Calabi–Yau varieties. Next we consider deformations of our K3-fibered Calabi–Yau threefolds, and we study the variation of the zeta-functions using p-adic rigid cohomology theory.
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14

Quintero Vélez, Alexander, et Alex Boer. « Noncommutative Resolutions of ADE Fibered Calabi-Yau Threefolds ». Communications in Mathematical Physics 297, no 3 (17 mai 2010) : 597–619. http://dx.doi.org/10.1007/s00220-010-1052-5.

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15

Mazur, Karolina, Stanislaw Kuciel et Kamila Salasinska. « Mechanical, fire, and smoke behaviour of hybrid composites based on polyamide 6 with basalt/carbon fibres ». Journal of Composite Materials 53, no 28-30 (28 mai 2019) : 3979–91. http://dx.doi.org/10.1177/0021998319853015.

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This paper describes the hybridization of basalt and carbon fibres in polyamide 6 by injection moulding method and the analyses of the mechanical, morphological, fire, and smoke properties of the obtained materials. The content of basalt/carbon fibres in hybrid composites amounted to 5/5 wt%, 7/7 wt%, and 10/10 wt%. The addition of fibres resulted in an increase in mechanical properties of the examined materials, was reflected by the threefold increase of Young modulus for the composites containing 10/10 wt% of fibres. To investigate the aging, the samples were stored in distilled water for 1, 7, 14, 100, and 210 days. After 210 days, a significant decrease in mechanical properties was observed. Interestingly, the addition of fibres caused a 50% reduction in stiffness, whereas, in the case of neat polyamide 6, the decrease was about 78%. Additionally, the addition of fibres reduced water sorption. With the increasing fibre load, the decrease in the maximum average rate of heat emission was observed. In the case of composites containing 10 wt% of basalt fibres and 10 wt% of carbon fibres, it amounted to 207 kW/m2 and was lower by approx. 37% in comparison to the unmodified polymer.
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16

Audier, Marc, et Michel Duneau. « Icosahedral quasiperiodic packing of fibres parallel to fivefold and threefold axes ». Acta Crystallographica Section A Foundations of Crystallography 56, no 1 (1 janvier 2000) : 49–61. http://dx.doi.org/10.1107/s0108767399010533.

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17

HUNT, BRUCE, et ROLF SCHIMMRIGK. « K3-FIBERED CALABI–YAU THREEFOLDS I : THE TWIST MAP ». International Journal of Mathematics 10, no 07 (novembre 1999) : 833–69. http://dx.doi.org/10.1142/s0129167x99000367.

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18

Turchet, Amos. « Fibered threefolds and Lang-Vojta’s conjecture over function fields ». Transactions of the American Mathematical Society 369, no 12 (30 mai 2017) : 8537–58. http://dx.doi.org/10.1090/tran/6968.

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19

Braun, A. P., S. Gerigk, A. Hebecker et H. Triendl. « D7-brane moduli vs. F-theory cycles in elliptically fibred threefolds ». Nuclear Physics B 836, no 1-2 (septembre 2010) : 1–36. http://dx.doi.org/10.1016/j.nuclphysb.2010.04.008.

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20

Doran, Charles F., Andrew Harder, Andrey Y. Novoseltsev et Alan Thompson. « Calabi–Yau threefolds fibred by high rank lattice polarized K3 surfaces ». Mathematische Zeitschrift 294, no 1-2 (3 avril 2019) : 783–815. http://dx.doi.org/10.1007/s00209-019-02279-9.

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21

Ovrut, Burt A., René Reinbacher et Tony Pantev. « Torus-Fibered Calabi-Yau threefolds with non-trivial fundamental group ». Journal of High Energy Physics 2003, no 05 (16 mai 2003) : 040. http://dx.doi.org/10.1088/1126-6708/2003/05/040.

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22

Ekedahl, Torsten, Trygve Johnsen et Dag Einar Sommervoll. « Isolated rational curves on K 3-fibered Calabi-Yau threefolds ». manuscripta mathematica 99, no 1 (1 mai 1999) : 111–33. http://dx.doi.org/10.1007/s002290050165.

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23

Catanese, Fabrizio, et Frédéric Mangolte. « Real singular Del Pezzo surfaces and threefolds fibred by rational curves, I ». Michigan Mathematical Journal 56, no 2 (octobre 2008) : 357–73. http://dx.doi.org/10.1307/mmj/1224783518.

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24

CHEN, MENG, et ZHIJIE J. CHEN. « Irregularity of canonical pencils for a threefold of general type ». Mathematical Proceedings of the Cambridge Philosophical Society 125, no 1 (janvier 1999) : 83–87. http://dx.doi.org/10.1017/s0305004198002734.

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Let X be a complex nonsingular projective threefold of general type. Suppose the canonical system of X is composed of a pencil, i.e. dimΦ∼KX∼(X)=1. It is often important to understand birational invariants of X such as pg(X), q(X), h2(OX) and χ(OX) etc. In this paper, we mainly study the irregularity of X.We may suppose that ∼KX∼ is free of base points. There is a natural fibration f[ratio ]X→C onto a nonsingular curve after the Stein factorization of Φ∼KX∼. Let F be a general fibre of f, then we know that F is a nonsingular projective surface of general type. Set b[ratio ]=g(C) and pg(F), q(F) for the respective invariants of F. The main result is the following theorem.
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25

NAKASHIMA, TOHRU. « MODULI SPACES OF STABLE BUNDLES ON K3 FIBERED CALABI–YAU THREEFOLDS ». Communications in Contemporary Mathematics 05, no 01 (février 2003) : 119–26. http://dx.doi.org/10.1142/s0219199703000884.

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In this paper we study stable rank two bundles on a Calabi–Yau threefold. For hypersurfaces in a ℙ3-bundle over ℙ1, we show that their moduli spaces have irreducible components which are birational to projective spaces.
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26

Wilson, P. M. H. « The existence of elliptic fibre space structures on Calabi-Yau threefolds ». Mathematische Annalen 300, no 1 (septembre 1994) : 693–703. http://dx.doi.org/10.1007/bf01450510.

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27

Grassi, Antonella, et David R. Morrison. « Group representations and the Euler characteristic of elliptically fibered Calabi--Yau threefolds ». Journal of Algebraic Geometry 12, no 2 (1 mai 2003) : 321–56. http://dx.doi.org/10.1090/s1056-3911-02-00337-5.

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28

Schütt, Matthias. « On the Modularity of Three Calabi–Yau Threefolds With Bad Reduction at 11 ». Canadian Mathematical Bulletin 49, no 2 (1 juin 2006) : 296–312. http://dx.doi.org/10.4153/cmb-2006-031-9.

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AbstractThis paper investigates the modularity of three non-rigid Calabi–Yau threefolds with bad reduction at 11. They are constructed as fibre products of rational elliptic surfaces, involving the modular elliptic surface of level 5. Their middle ℓ-adic cohomology groups are shown to split into two-dimensional pieces, all but one of which can be interpreted in terms of elliptic curves. The remaining pieces are associated to newforms of weight 4 and level 22 or 55, respectively. For this purpose, we develop a method by Serre to compare the corresponding two-dimensional 2-adic Galois representations with uneven trace. Eventually this method is also applied to a self fibre product of the Hesse-pencil, relating it to a newform of weight 4 and level 27.
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29

WILSON, P. M. H. « The existence of elliptic fibre space structures on Calabi–Yau threefolds, II ». Mathematical Proceedings of the Cambridge Philosophical Society 123, no 2 (mars 1998) : 259–62. http://dx.doi.org/10.1017/s030500419700220x.

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Mikołajczyk, Zbigniew, Katarzyna Pieklak et Aleksandra Roszak. « Knitted Meshes for Reinforcing Building Composites ». Fibres and Textiles in Eastern Europe 27, no 4(136) (31 août 2019) : 102–11. http://dx.doi.org/10.5604/01.3001.0013.1826.

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Modern technical textiles, including knitted fabrics, are widely used in the construction industry. Regarding textiles in concrete reinforcement, methods based on shredded fibres, meshes, reinforcing mats, woven textiles and knitted DOStapes are frequently used as underlays of concrete constructions. Textiles are also used in the reinforcement of fibrous FRP composites. The research presented focused on producing composites made of MapeiMapefill concrete mass with reinforcement in the form of three variants of knitted meshes made of 228 tex polyamide threads, polypropylene threads of 6.3 tex and 203 tex glass threads, as well as identification of their mechanical properties. The mesh variant made of glass fibre is especially noteworthy, as its strength is more than three times higher than that of polyamide meshes. At the same time, a very small relative elongation of 3% is observed for this variant of knitted fabric, which is a desired property regarding the comparatively low stretching extension of concrete. In the process of making the composites, the adhesion of the concrete mass to the surface of the threads was analyzed. For this purpose, a "Sopro HE449" type agent was used. Composite beams were subjected to a three-point bending strength analysis on a testing machine. The results of strength measurements of the composites obtained prove that those with glass fibres demonstrate a threefold increase in strength compared to the original concrete beam.
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31

Johnston, I. A., N. J. Cole, M. Abercromby et V. L. A. Vierira. « Embryonic temperature modulates muscle growth characteristics in larval and juvenile herring ». Journal of Experimental Biology 201, no 5 (1 mars 1998) : 623–46. http://dx.doi.org/10.1242/jeb.201.5.623.

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The influence of embryonic and larval temperature regime on muscle growth was investigated in Atlantic herring (Clupea harengus L.). Eggs of spring-spawning Clyde herring were incubated at 5 degrees C, 8 degrees C or 12 degrees C until hatching and then reared until after metamorphosis at rising temperatures to simulate a seasonal warming. Metamorphosis to the juvenile stage was complete at 37 mm total length (TL), after an estimated 177 days as a larva at 5 degrees C, 117 days at 8 degrees C and 101 days at 12 degrees C. Growth rate and the development of median fins were retarded in relation to body length at 5 degrees C compared with 8 degrees C and 12 degrees C. Between hatching (at 8-9 mm TL) and 16 mm TL, there was a threefold increase in total muscle cross-sectional area, largely due to the hypertrophy of the embryonic red and white muscle fibres. The recruitment of additional white muscle fibres started at approximately 15 mm TL at all temperatures, and by 37 mm was estimated to be 66 fibres day-1 at 5 degrees C and 103 fibres day-1 at 8 degrees C and 12 degrees C. Peptide mapping studies revealed a change in myosin heavy chain composition in white muscle fibres between 20 and 25 mm TL. Embryonic red muscle fibres expressed fast myosin light chains until 24-28 mm TL at 5 degrees C and 22 mm TL at 12 degrees C, and new red fibres were added at the horizontal septum starting at the same body lengths. Following metamorphosis, the total cross-sectional area of muscle was similar at different temperatures, although the number of red and white fibres per myotome was significantly greater at the warmest than at the coldest regime. For example, the mean number of white muscle fibres per myotome in 50 mm TL juveniles was calculated to be 23.4 % higher at 12 degrees C (12 065) than at 5 degrees C (9775). In other experiments, spring-spawning (Clyde) and autumn-spawning (Manx) herring were reared at different temperatures until first feeding and then transferred to ambient seawater temperature and fed ad libitum for constant periods. These experiments showed that, for both stocks, the temperature of embryonic development influenced the subsequent rate of muscle fibre recruitment and hypertrophy as well as the density of muscle nuclei. Labelling experiments with 5'-bromo-2-deoxyuridine showed that both the hypertrophy and recruitment of muscle fibres involved a rapidly proliferating population of myogenic precursor cells. The cellular mechanisms underlying the environmental modulation of muscle growth phenotype are discussed.
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32

Maltin, C. A., M. I. Delday, S. M. Hay, G. M. Innes et P. E. V. Williams. « Effects of bovine pituitary growth hormone alone or in combination with the β-agonist clenbuterol on muscle growth and composition in veal calves ». British Journal of Nutrition 63, no 3 (mai 1990) : 535–45. http://dx.doi.org/10.1079/bjn19900140.

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Twenty-three British Friesian bull calves at approximately 7 d of age were allocated to one of four treatments: controls untreated (five calves), a group (Clen) given 1 mg clenbuterol/kg diet (five calves), a group (GH) given a daily subcutaneous injection of 3.5 mg bovine pituitary growth hormone (GH) (five calves) and a group (Clen + GH) given a combination of clenbuterol as in the Clen group with GH as in the GH group (seven calves). All calves were given milk-substitute at levels adjusted weekly according to metabolic live weight. The animals were slaughtered over the weight range 150–170 kg. Samples of semimembranosus and triceps muscles were excised a t slaughter. Treatment with GH produced approximately a threefold increase in mean daily serum GH concentration. Calves given Clen + GH were heaviest a t slaughter and the combined treatment produced a significantly higher (P < 0-01) feed conversion ratio. Administration of clenbuterol either alone or in combination with GH increased the cross-sectional area of both fast twitch glycolytic (FG), and fast twitch oxidative glycolytic (FOG) fibres in both muscles. In contrast GH produced little change in fibre size in semimembranosus muscle, although FOG fibres in triceps were slightly larger than in controls. Neither Clen nor GH resulted in any change in fibre percentage frequency in either muscle. Treatments involving clenbuterol produced a significant decrease in muscle glycogen concentration. Muscles from all three treatment groups tended to show small increases in protein and RNA concentration compared with the controls. Muscles from animals treated with GH alone exhibited an increase in DNA concentration not seen in muscles from the two other treatment groups. Overall, the differential response to the two agents suggested that clenbuterol does not mediate its effects via the GH axis, and that an additive response in terms of protein anabolism may be achieved from the use of a combination of clenbuterol plus GH.
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33

Braun, Volker. « Discrete Wilson Lines in F-Theory ». Advances in High Energy Physics 2011 (2011) : 1–18. http://dx.doi.org/10.1155/2011/404691.

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F-theory models are constructed where the7-brane has a nontrivial fundamental group. The base manifolds used are a toric Fano variety and a smooth toric threefold coming from a reflexive polyhedron. The discriminant locus of the elliptically fibered Calabi-Yau fourfold can be chosen such that one irreducible component is not simply connected (namely, an Enriques surface) and supports a non-Abelian gauge theory.
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34

Martin, W. H., A. R. Coggan, R. J. Spina et J. E. Saffitz. « Effects of fiber type and training on beta-adrenoceptor density in human skeletal muscle ». American Journal of Physiology-Endocrinology and Metabolism 257, no 5 (1 novembre 1989) : E736—E742. http://dx.doi.org/10.1152/ajpendo.1989.257.5.e736.

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The density and distribution of beta-adrenergic receptors in type I and II fibers of human gastrocnemius and quadriceps muscles were characterized in ten healthy sedentary subjects and in a subgroup of six subjects before and after 12 wk of endurance exercise training. Total tissue content of beta-receptors was measured in frozen sections of skeletal muscle biopsies incubated with 125I-labeled cyanopindolol in the presence and absence of 10(-5) M L-propranolol. The relative beta-receptor densities of type I and II fibers were delineated autoradiographically. Muscle fiber types were identified in adjacent serial sections by histochemical staining of myofibrillar adenosine-triphosphatase (ATPase) activity. Type I fibers had a threefold greater beta-receptor density than type II fibers of the same muscle [P less than 0.001; type I-to-type II fiber ratio of beta-receptor density was 3.06 +/- 0.43 (SD)]. Exercise training elicited a change in muscle fiber subtype composition (+34% type IIa and -42% type IIb; P less than 0.05 and P = 0.066, respectively), a 40% increase in citrate synthase activity of skeletal muscle (P = 0.01), and a 23% rise in peak oxygen uptake (P less than 0.001). However, no change in total tissue content of beta-receptors was observed after exercise training, even when receptor density was adjusted for preconditioning fiber type composition. Thus beta-receptor density of type I fibers of human skeletal muscle is threefold greater than that of type II fibers. Enhanced capacity for aerobic metabolism after endurance exercise training is not associated with upregulation of total beta-receptor density.
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35

Prince, Thomas. « Smoothing Calabi–Yau toric hypersurfaces using the Gross–Siebert algorithm ». Compositio Mathematica 157, no 7 (17 juin 2021) : 1441–91. http://dx.doi.org/10.1112/s0010437x21007132.

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We explain how to form a novel dataset of Calabi–Yau threefolds via the Gross–Siebert algorithm. We expect these to degenerate to Calabi–Yau toric hypersurfaces with certain Gorenstein (not necessarily isolated) singularities. In particular, we explain how to ‘smooth the boundary’ of a class of four-dimensional reflexive polytopes to obtain polarised tropical manifolds. We compute topological invariants of a compactified torus fibration over each such tropical manifold, expected to be homeomorphic to the general fibre of the Gross–Siebert smoothing. We consider a family of examples related to products of reflexive polygons. Among these we find $14$ topological types with $b_2=1$ that do not appear in existing lists of known rank-one Calabi–Yau threefolds.
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36

Mäkinen, Harri, Pekka Saranpää et Sune Linder. « Wood-density variation of Norway spruce in relation to nutrient optimization and fibre dimensions ». Canadian Journal of Forest Research 32, no 2 (1 février 2002) : 185–94. http://dx.doi.org/10.1139/x01-186.

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The effect of fertilization on wood density, fibre length, fibre diameter, lumen diameter, proportion of cell wall area, and cell wall thickness of Norway spruce (Picea abies (L.) Karst.) were studied in a nutrient optimization experiment in northern Sweden. On the fertilized plots, all essential macronutrients and micronutrients were supplied in irrigation water every second day during the growing season. After 12 years' treatment, data were collected from 24 trees (40 years old) on the fertilized and control plots. Fertilization increased radial growth more than threefold, especially earlywood width, and decreased wood density by over 20% at 1.3 and 4 m height. The decrease in wood density was closely related to the proportion of latewood. The absolute wood density also decreased across the whole annual ring but proportionately more in latewood than in earlywood. A close relationship was found between the wood density and fibre properties, especially with the proportion of cell wall in a cross section of each annual ring, as well as with fibre and lumen width. The absolute cell wall thickness was clearly less related to wood density. However, rather large variations were found between individual trees in the relationship between wood density and fibre properties.
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37

Lanteri, Antonio. « Vertically of (-1)-Lines in Scrolls Over Smooth Surfaces ». Canadian Mathematical Bulletin 34, no 2 (1 juin 1991) : 236–39. http://dx.doi.org/10.4153/cmb-1991-038-3.

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AbstractLet S be a smooth surface contained as an ample divisor in a smooth complex projective threefold X, which is a P1 -bundle, and assume that induces OP1 (1) on the fibres of X. The following fact is proven. The restriction to S of the bundle projection of X is exactly the reduction morphism of the pair provided that this one is not a conic bundle. The proof is very simple and does not involve any consideration on the nefness of the adjoint bundle Some applications of the proof are given.
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38

Armstrong, Elizabeth F., Martin A. Eastwood, Christine A. Edwards, W. Gordon Brydon et Cecilia C. A. MacIntyre. « The effect of weaning diet on the subsequent colonic metabolism of dietary fibre in the adult rat ». British Journal of Nutrition 68, no 3 (novembre 1992) : 741–51. http://dx.doi.org/10.1079/bjn19920130.

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The effect of the weaning diet on the subsequent colonic metabolism of bran and pectin in the adult rat has been investigated. Feeding a fibre-reduced diet on its own or supplemented with bran (WB) and pectin (P) from weaning (fibre-reduced (weaning)) was compared with introducing the same diet to age-matched rats reared on a standard laboratory diet from weaning (fibre-reduced (6 weeks)). The effects of the diets on colonic metabolism were measured by wet and dry caecal contents and stool weights, caecal sac weight, and caecal and faecal short-chain fatty acids (SCFA). Final body-weights were greater for fibre-reduced (6 weeks) and fibre-reduced (6 weeks)+P groups, but not fibre-reduced (6 weeks)+WB, than those of the fibre-reduced (weaning) rats. Rats fed on fibre-reduced (6 weeks) diet had a higher total caecal SCFA content than fibre-reduced (weaning) control rats. Fibre-reduced (weaning)+P-fed rats had a threefold higher caecal concentration of both propionate and butyrate than the matched fibre-reduced (6 weeks)+P group. Fibre-reduced (weaning)+WB animals had a significantly higher butyrate caecal concentration compared with their matched fibre-reduced (6 weeks)+WB group. Fibre-reduced (weaning)+P-fed rats had a lower faecal output than the fibre-reduced (6 weeks)+P rats. There was no difference in faecal output in rats fed on either fibre-reduced (6 weeks)+ WB or fibre-reduced (weaning)+WB. The faecal concentration of SCFA was in general higher in the rats fed on fibre-reduced (weaning) alone, +P, or +WB than in those fed on fibre-reduced (6 weeks) alone, +P or +WB. Faecal output of total and individual SCFA was increased on the fibre-reduced (weaned)+WB diet compared with fibre-reduced (6 weeks)+WB-fed animals. The diet at weaning may be important in determining the pathways of caecal bacterial metabolism in the adult rat. In studying the effect of a dietary fibre on caecal metabolism and faecal output, when the diet is changed appears to be important
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39

Ribeiro, M. C. S., L. F. P. Juvandes, J. D. Rodrigues, António J. M. Ferreira et António Torres Marques. « Behaviour of Cement and Polymer Mortar Materials to Rapid Freeze-Thaw Cycling ». Materials Science Forum 636-637 (janvier 2010) : 1329–35. http://dx.doi.org/10.4028/www.scientific.net/msf.636-637.1329.

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The aim of this investigation work is threefold: 1) To analyse and quantify freeze-thaw resistance of glass fibre reinforced epoxy polymer mortars, comparatively to both normal cement mortars and plain epoxy polymer mortars; 2) To determine glass fibre reinforcement effect on freeze-thaw behaviour; and 3) To evaluate the reliability of ASTM C666M-03 test methodology for the assessment of freeze-thaw resistance of polymer concrete materials. For this purpose several test specimens, normal cement mortars, plain and glass-fibre reinforced epoxy polymer mortars were submitted to freeze-thaw cycling between 36 up to 300 cycles, according to the above norm. Dynamic elasticity modulus, with basis on fundamental resonance frequency measurements, was calculated every 36 cycles, and the correspondent relative dynamic elasticity modulus was determined for each cycling period. In order to assess the reliability of this non-destructive test methodology, three specimens of each formulation were withdrawn at regular periods and tested in bending and compression. Relative mechanical strengths, as function of conditioning period, were compared with corresponding relative dynamic modulus of elasticity.
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40

Yu, Xiong-jie, J. David Dickman, Gregory C. DeAngelis et Dora E. Angelaki. « Neuronal thresholds and choice-related activity of otolith afferent fibers during heading perception ». Proceedings of the National Academy of Sciences 112, no 20 (4 mai 2015) : 6467–72. http://dx.doi.org/10.1073/pnas.1507402112.

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How activity of sensory neurons leads to perceptual decisions remains a challenge to understand. Correlations between choices and single neuron firing rates have been found early in vestibular processing, in the brainstem and cerebellum. To investigate the origins of choice-related activity, we have recorded from otolith afferent fibers while animals performed a fine heading discrimination task. We find that afferent fibers have similar discrimination thresholds as central cells, and the most sensitive fibers have thresholds that are only twofold or threefold greater than perceptual thresholds. Unlike brainstem and cerebellar nuclei neurons, spike counts from afferent fibers do not exhibit trial-by-trial correlations with perceptual decisions. This finding may reflect the fact that otolith afferent responses are poorly suited for driving heading perception because they fail to discriminate self-motion from changes in orientation relative to gravity. Alternatively, if choice probabilities reflect top-down inference signals, they are not relayed to the vestibular periphery.
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41

He, Yang-Hui, John McKay et James Read. « Modular subgroups, dessins d’enfants and elliptic K3 surfaces ». LMS Journal of Computation and Mathematics 16 (2013) : 271–318. http://dx.doi.org/10.1112/s1461157013000119.

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AbstractWe consider the 33 conjugacy classes of genus zero, torsion-free modular subgroups, computing ramification data and Grothendieck’s dessins d’enfants. In the particular case of the index 36 subgroups, the corresponding Calabi–Yau threefolds are identified, in analogy with the index 24 cases being associated to K3 surfaces. In a parallel vein, we study the 112 semi-stable elliptic fibrations over ${ \mathbb{P} }^{1} $ as extremal K3 surfaces with six singular fibres. In each case, a representative of the corresponding class of subgroups is identified by specifying a generating set for that representative.
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42

ANDREAS, B., D. HERNÁNDEZ RUIPÉREZ et D. SÁNCHEZ GÓMEZ. « STABLE SHEAVES OVER K3 FIBRATIONS ». International Journal of Mathematics 21, no 01 (janvier 2010) : 25–46. http://dx.doi.org/10.1142/s0129167x10005908.

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We construct stable sheaves over K3 fibrations using a relative Fourier-Mukai transform which describes the sheaves in terms of spectral data similar to the construction for elliptic fibrations. On K3 fibered Calabi–Yau threefolds we show that the Fourier-Mukai transform induces an embedding of the relative Jacobian of spectral line bundles on spectral covers into the moduli space of sheaves of given invariants. This makes the moduli space of spectral sheaves a generic torus fibration over the moduli space of curves of the given arithmetic genus on the Calabi–Yau manifold.
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43

Allen, D. L., S. R. Monke, R. J. Talmadge, R. R. Roy et V. R. Edgerton. « Plasticity of myonuclear number in hypertrophied and atrophied mammalian skeletal muscle fibers ». Journal of Applied Physiology 78, no 5 (1 mai 1995) : 1969–76. http://dx.doi.org/10.1152/jappl.1995.78.5.1969.

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Although a mammalian skeletal muscle fiber may contain thousands of myonuclei, the importance of this number or the potential to modulate it in adult muscle has not been clearly demonstrated. Using immunohistochemistry and confocal microscopy, we examined the plasticity of myonuclear number and fiber size in isolated fast and slow fiber segments from adult cat hindlimb muscles in response to chronic alterations in neuromuscular activity and loading. Compared with slow fibers in the soleus of control cats, myonuclear number in presumably transformed fast fibers was 32% lower and fiber size was decreased 73% after elimination of neuromuscular activation for 6 mo by spinal isolation. Slow fibers in the soleus of spinal-isolated cats had smaller cross-sectional areas, whereas myonuclear number was not significantly different than that in the control cats. Myonuclear number in fast plantaris fibers was more than threefold higher and fiber size was 2.8-fold higher after 3 mo of functional overload compared with the plantaris of control cats. Compared with control slow plantaris fibers, myonuclear number and fiber size also increased in overloaded slow plantaris fibers. These results demonstrate that changes in myonuclear number are associated with changes in myosin type and suggest that modulations in the amount of available DNA may be a factor in regulating cytoplasmic volume of muscle fibers in response to chronic changes in neuromuscular activity.
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Špoljarić, Branimira, Maja Popović, Josip Crnjac, Zrinka Žderić Savatović, Martina Ratko, Mateja Lozančić, Matea Jurak, Igor Špoljarić, Daniel Špoljarić et Gordan Mršić. « Gleaning a Human DNA Profile from Trace Swabs Collected from Animal Hairs ». Acta Veterinaria 66, no 2 (1 juin 2016) : 187–202. http://dx.doi.org/10.1515/acve-2016-0016.

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Abstract Animal hairs are an apt surface for retention of forensic trace epithelial samples. The aim of this study was threefold: to evaluate different methods of sample collection (moistened and dry swabs) and DNA extraction (Chelex® 100 method, Qiagen EZ1® DNA Investigator Kit), as well as to examine the morphological differences of hair fibres between two species (dog, sheep) and their ultimate impact on sample collection and processing. Our preliminary findings suggest that the use of EZ1® DNA Investigator Kit yields donor DNA profiles of higher quality. The results of different sample collection methods have shown intraspecific variations that require further investigation. The ability of retention and subsequent extraction of trace DNA appears to be similar between the two species, despite significant morphological differences between their coat hairs.
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45

Gorumlu, Serdar, et Burak Aksak. « Sticking to rough surfaces using functionally graded bio-inspired microfibres ». Royal Society Open Science 4, no 6 (juin 2017) : 161105. http://dx.doi.org/10.1098/rsos.161105.

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Synthetic fibrillar adhesives inspired by nature, most commonly by the gecko lizard, have been shown to strongly and repeatedly attach to smooth surfaces. These adhesives, mostly of monolithic construction, perform on par with their natural analogues on smooth surfaces but exhibit far inferior adhesive performance on rough surfaces. In this paper, we report on the adhesive performance of functionally graded microfibrillar adhesives based on a microfibre with a divergent end and a thin soft distal layer on rough surfaces. Monolithic and functionally graded fibre arrays were fabricated from polyurethanes and their adhesive performance on surfaces of varying roughness were quantified from force–distance data obtained using a custom adhesion measurement system. Average pull-off stress declined significantly with increasing roughness for the monolithic fibre array, dropping from 77 kPa on the smoothest (54 nm RMS roughness) to 19 kPa on the roughest (408 nm RMS roughness) testing surface. In comparison, pull-off stresses of 81 kPa and 63 kPa were obtained on the same respective smooth and rough surfaces with a functionally graded fibre array, which represents a more than threefold increase in adhesion to the roughest adhering surface. These results show that functionally graded fibrillar adhesives perform similar on all the testing surfaces unlike monolithic arrays and show potential as repeatable and reusable rough surface adhesives.
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46

Matthäus, Carla, Nadine Kofler, Thomas Kränkel, Daniel Weger et Christoph Gehlen. « Interlayer Reinforcement Combined with Fiber Reinforcement for Extruded Lightweight Mortar Elements ». Materials 13, no 21 (26 octobre 2020) : 4778. http://dx.doi.org/10.3390/ma13214778.

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Lightweight mortar extrusion enables the production of monolithic exterior wall components with improved thermal insulation by installing air chambers and reduced material demand compared to conventional construction techniques. However, without reinforcement, the systems are not capable of bearing high flexural forces and, thus, the application possibilities are limited. Furthermore, the layer bonding is a weak spot in the system. We investigate a reinforcement strategy combining fibers in the mortar matrix with vertically inserted elements to compensate the layer bonding. By implementing fibers in the extruded matrix, the flexural strength can be increased almost threefold parallel to the layers. However, there is still an anisotropy between the layers as fibers are oriented during deposition and the layer bond is still mainly depending on hydration processes. This can be compensated by the vertical insertion of reinforcement elements in the freshly deposited layers. Corrugated wire fibers as well as short steel reinforcement elements were suitable to increase the flexural strength between the layers. As shown, the potential increase in flexural strength could be of a factor six compared to the reference (12 N/mm2 instead of 1.9 N/mm2). Thus, the presented methods reduce anisotropy in flexural strength due to layered production.
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47

Edwards, Joshua N., Oliver Friedrich, Tanya R. Cully, Frederic von Wegner, Robyn M. Murphy et Bradley S. Launikonis. « Upregulation of store-operated Ca2+ entry in dystrophic mdx mouse muscle ». American Journal of Physiology-Cell Physiology 299, no 1 (juillet 2010) : C42—C50. http://dx.doi.org/10.1152/ajpcell.00524.2009.

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Store-operated Ca2+ entry (SOCE) is an important mechanism in virtually all cells. In adult skeletal muscle, this mechanism is highly specialized for the rapid delivery of Ca2+ from the transverse tubule into the junctional cleft during periods of depleting Ca2+ release. In dystrophic muscle fibers, SOCE may be a source of Ca2+ overload, leading to cell necrosis. However, this possibility is yet to be examined in an adult fiber during Ca2+ release. To examine this, Ca2+ in the tubular system and cytoplasm were simultaneously imaged during direct release of Ca2+ from sarcoplasmic reticulum (SR) in skeletal muscle fibers from healthy (wild-type, WT) and dystrophic mdx mouse. The mdx fibers were found to have normal activation and deactivation properties of SOCE. However, a depression of the cytoplasmic Ca2+ transient in mdx compared with WT fibers was observed, as was a shift in the SOCE activation and deactivation thresholds to higher SR Ca2+ concentrations ([Ca2+]SR). The shift in SOCE activation and deactivation thresholds was accompanied by an approximately threefold increase in STIM1 and Orai1 proteins in dystrophic muscle. While the mdx fibers can introduce more Ca2+ into the fiber for an equivalent depletion of [Ca2+]SR via SOCE, it remains unclear whether this is deleterious.
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48

Choi, Seung Jun, et Jeffrey J. Widrick. « Calcium-activated force of human muscle fibers following a standardized eccentric contraction ». American Journal of Physiology-Cell Physiology 299, no 6 (décembre 2010) : C1409—C1417. http://dx.doi.org/10.1152/ajpcell.00226.2010.

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Peak Ca2+-activated specific force (force/fiber cross-sectional area) of human chemically skinned vastus lateralis muscle fiber segments was determined before and after a fixed-end contraction or an eccentric contraction of standardized magnitude (+0.25 optimal fiber length) and velocity (0.50 unloaded shortening velocity). Fiber myosin heavy chain (MHC) isoform content was assayed by SDS-PAGE. Posteccentric force deficit, a marker of damage, was similar for type I and IIa fibers but threefold greater for type IIa/IIx hybrid fibers. A fixed-end contraction had no significant effect on force. Multiple linear regression revealed that posteccentric force was explained by a model consisting of a fiber type-independent and a fiber type-specific component ( r2 = 0.91). Preeccentric specific force was directly associated with a greater posteccentric force deficit. When preeccentric force was held constant, type I and IIa fibers showed identical susceptibility to damage, while type IIa/IIx fibers showed a significantly greater force loss. This heightened sensitivity to damage was directly related to the amount of type IIx MHC in the hybrid fiber. Our model reveals a fiber-type sensitivity of the myofilament lattice or cytoskeleton to mechanical strain that can be described as follows: type IIa/IIx > type IIa = type I. If these properties extend to fibers in vivo, then alterations in the number of type IIa/IIx fibers may modify a muscle's susceptibility to eccentric damage.
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Wood, Lauren K., Erdan Kayupov, Jonathan P. Gumucio, Christopher L. Mendias, Dennis R. Claflin et Susan V. Brooks. « Intrinsic stiffness of extracellular matrix increases with age in skeletal muscles of mice ». Journal of Applied Physiology 117, no 4 (15 août 2014) : 363–69. http://dx.doi.org/10.1152/japplphysiol.00256.2014.

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Advanced age is associated with increases in muscle passive stiffness, but the contributors to the changes remain unclear. Our purpose was to determine the relative contributions of muscle fibers and extracellular matrix (ECM) to muscle passive stiffness in both adult and old animals. Passive mechanical properties were determined for isolated individual muscle fibers and bundles of muscle fibers that included their associated ECM, obtained from tibialis anterior muscles of adult (8–12 mo old) and old (28–30 mo old) mice. Maximum tangent moduli of individual muscle fibers from adult and old muscles were not different at any sarcomere length tested. In contrast, the moduli of bundles of fibers from old mice was more than twofold greater than that of fiber bundles from adult muscles at sarcomere lengths >2.5 μm. Because ECM mechanical behavior is determined by the composition and arrangement of its molecular constituents, we also examined the effect of aging on ECM collagen characteristics. With aging, muscle ECM hydroxyproline content increased twofold and advanced glycation end-product protein adducts increased threefold, whereas collagen fibril orientation and total ECM area were not different between muscles from adult and old mice. Taken together, these findings indicate that the ECM of tibialis anterior muscles from old mice has a higher modulus than the ECM of adult muscles, likely driven by an accumulation of densely packed extensively crosslinked collagen.
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AHN, CHANGHYUN, KYUNGHO OH et RADU TATAR. « THE LARGE-N LIMIT OF $\mathcal{N} = 1$ FIELD THEORIES FROM F THEORY ». Modern Physics Letters A 14, no 05 (20 février 1999) : 369–78. http://dx.doi.org/10.1142/s0217732399000420.

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We study AdS/CFT correspondence in four-dimensional [Formula: see text] field theories realized on the world-volume of D3 branes near the intersections between D7 and D 7′ branes in F theory studied by Aharony et al. We consider the compactification of F theory on elliptically fibered Calabi–Yau threefolds corresponding to two sets of parallel D7 branes sharing six space–time directions. This can be viewed as orbifolds of six torus T6 by Zp × Zq(p,q = 2,3,4,6). We find the large-N spectrum of chiral primary operators by exploiting the property of AdS/CFT correspondence. Moreover, we discuss super gravity solutions for D3 branes in D7 and D 7′ branes background.
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