Search results for "CONI"

Porous zirconia and titania as packing materials for high-performance liquid chromatography

1990

Abstract Porous amorphous zirconia (ZrO 2 ) and titania (TiO 2 ) packings were synthesized as rigid microparticulate beads by means of a sol—gel process. Sufficient rigidity and desired mesoporosity of the ZrO 2 and TiO 2 particles were achieved only by a gel hardening process, followed by heat treatment. The mean pore diameter, p d , the specific surface area, a s , and the specific pore volume, ν p , were controlled by the heat treatment. Typical values were p d = 8 nm, a s = 80 m 2 /g and ν p = 0.23 ml/g. ZrO 2 - and TiO 2 -based revesed-phase packings were prepared by subjecting the native materials to a specific activation process and reaction with octadecyltrimethoxysilane. Native ZrO…

Falcó rialler, Halcón reidor (VER0000173)

Altres noms vulgars: Laughing Falcon (Anglès), Macagua rieur (Francès), Lachfalke (Alemany) Gabinet de Vertebrats (Departament de Zoologia), Facultat de Ciències Biològiques (Campus de Burjassot), C/ Doctor Moliner, s/n, Bloque B. 5é plant, Burjassot (Valencia). Armari: 1-1 Nueva Granada Macho Adulto

A sensitive study of the peculiar jet structure HST-1 in M87

2013

To obtain a better understanding of the location and mechanisms for the production of the gamma-ray emission in jets of AGN we present a detailed study of the HST-1 structure, 0.8 arcsec downstream the jet of M87, previously identified as a possible candidate for TeV emission. HST-1 shows a very peculiar structure with superluminal as well as possible stationary sub-components, and appears to be located in the transition from a parabolic to a conical jet shape, presumably leading to the formation of a recollimation shock. This scenario is supported by our new RHD simulations in which the interaction of a moving component with a recollimation shock leads to the appearance of a new superlumin…

Lines on the Dwork pencil of quintic threefolds

2012

We present an explicit parametrization of the families of lines of the Dwork pencil of quintic threefolds. This gives rise to isomorphic curves which parametrize the lines. These curves are 125:1 covers of certain genus six curves. These genus six curves are first presented as curves in P^1*P^1 that have three nodes. It is natural to blow up P^1*P^1 in the three points corresponding to the nodes in order to produce smooth curves. The result of blowing up P^1*P^1 in three points is the quintic del Pezzo surface dP_5, whose automorphism group is the permutation group S_5, which is also a symmetry of the pair of genus six curves. The subgroup A_5, of even permutations, is an automorphism of ea…

Conifold Transitions and Mirror Symmetry for Calabi-Yau Complete Intersections in Grassmannians

1997

In this paper we show that conifold transitions between Calabi-Yau 3-folds can be used for the construction of mirror manifolds and for the computation of the instanton numbers of rational curves on complete intersection Calabi-Yau 3-folds in Grassmannians. Using a natural degeneration of Grassmannians $G(k,n)$ to some Gorenstein toric Fano varieties $P(k,n)$ with conifolds singularities which was recently described by Sturmfels, we suggest an explicit mirror construction for Calabi-Yau complete intersections $X \subset G(k,n)$ of arbitrary dimension. Our mirror construction is consistent with the formula for the Lax operator conjectured by Eguchi, Hori and Xiong for gravitational quantum c…

Brevi note ornitologiche dalla Sicilia occidentale

1998

Ornithological short notes from western Sicily (Italy)

Remarks on the Historiography of Mathematics

2021

In this paper, I examine aspects of the methodological debate that originated in 2010, when the distinguished historian of mathematics Sabetai Unguru reviewed Roshdi Rashed’s edition of the Arabic translation of Apollonius’ Conics. In his review, Unguru criticized what Rashed calls “l’usage instrumental d’une autre mathématique pour commenter une oeuvre ancienne”. I consider this debate very important and will try to place it within in the discussion of the so-called “geometric algebra” that goes back to the seventies, by tracing the contributions of the main figures who took part in it. Published Online (2021-04-30)Copyright © 2021 by Aldo Brigaglia Article PDF Link: https://jps.library.ut…

Historical Origins of the nine-point conic -- The Contribution of Eugenio Beltrami

2020

In this paper, we examine the evolution of a specific mathematical problem, i.e. the nine-point conic, a generalisation of the nine-point circle due to Steiner. We will follow this evolution from Steiner to the Neapolitan school (Trudi and Battaglini) and finally to the contribution of Beltrami that closed this journey, at least from a mathematical point of view (scholars of elementary geometry, in fact, will continue to resume the problem from the second half of the 19th to the beginning of the 20th century). We believe that such evolution may indicate the steady development of the mathematical methods from Euclidean metric to projective, and finally, with Beltrami, with the use of quadrat…

Comparison of ZrO2:Y nanocrystals and macroscopic single crystal luminescence

2007

The luminescence spectra of a tetragonally structured ZrO2:Y single crystal and nanocrystals were compared. It was found that the number of luminescence centers contributed to the spectra. The excitation of luminescence within the band gap region led to different luminescence spectra for the single crystal and nanocrystal samples, whereas recombinative luminescence spectra were the same for both samples. The origin of this difference is that in the nanocrystals, even under excitation within the band gap, charge carriers were created. Zirconium- oxygen complexes distorted by intrinsic defects were proposed to be the luminescence centres responsible for the wide luminescence band observed.

Data from: Exposing the structure of an Arctic food web

2016

How food webs are structured has major implications for their stability and dynamics. While poorly studied to date, arctic food webs are commonly assumed to be simple in structure, with few links per species. If this is the case, then different parts of the web may be weakly connected to each other, with populations and species united by only a low number of links. We provide the first highly resolved description of trophic link structure for a large part of a high-arctic food web. For this purpose, we apply a combination of recent techniques to describing the links between three predator guilds (insectivorous birds, spiders, and lepidopteran parasitoids) and their two dominant prey orders …