Search results for "Geometric"
showing 10 items of 652 documents
Wedge-shaped bricks spires and domes. Construction and decorative aspects
2018
The use of maiolica bricks as artefact for surface decoration is widespread both in monumental and ordinary architectures in the Mediterranean regions, harmonizing the local construction traditions with the Islamic influences. This study presents an in-depth analysis of examples of spires and domes in Sicily featuring earthenware maiolica cladding serving both as decoration and structural element. Due to the limited knowledge of these artefacts, incautious construction operations led to an alteration of their material and technical features, putting at risk a centuries-old heritage. The systematic investigation on more than a hundred samples categorises these architectural polychrome elemen…
A Monte Carlo Study of Knots in Long Double-Stranded DNA Chains.
2016
We determine knotting probabilities and typical sizes of knots in double-stranded DNA for chains of up to half a million base pairs with computer simulations of a coarse-grained bead-stick model: Single trefoil knots and composite knots which include at least one trefoil as a prime factor are shown to be common in DNA chains exceeding 250,000 base pairs, assuming physiologically relevant salt conditions. The analysis is motivated by the emergence of DNA nanopore sequencing technology, as knots are a potential cause of erroneous nucleotide reads in nanopore sequencing devices and may severely limit read lengths in the foreseeable future. Even though our coarse-grained model is only based on …
The Plateau-Bézier Problem
2003
We study the Plateau problem restricted to polynomial surfaces using techniques coming from the theory of Computer Aided Geometric Design. The results can be used to obtain polynomial approximations to minimal surfaces. The relationship between harmonic Bezier surfaces and minimal surfaces with free boundaries is shown.
A Characterization of Quintic Helices
2005
A polynomial curve of degree 5, @a, is a helix if and only if both @[email protected]^'@? and @[email protected]^'@[email protected]^''@? are polynomial functions.
Singularity formation and separation phenomena in boundary layer theory
2009
In this paper we review some results concerning the behaviour of the incompressible Navier–Stokes solutions in the zero viscosity limit. Most of the emphasis is put on the phenomena occurring in the boundary layer created when the no-slip condition is imposed. Numerical simulations are used to explore the limits of the theory. We also consider the case of 2D vortex layers, i.e. flows with internal layers in the form of a rapid variation, across a curve, of the tangential velocity.
Commensurability in Artin groups of spherical type
2019
Let $A$ and $A'$ be two Artin groups of spherical type, and let $A_1,\dots,A_p$ (resp. $A'_1,\dots,A'_q$) be the irreducible components of $A$ (resp. $A'$). We show that $A$ and $A'$ are commensurable if and only if $p=q$ and, up to permutation of the indices, $A_i$ and $A'_i$ are commensurable for every $i$. We prove that, if two Artin groups of spherical type are commensurable, then they have the same rank. For a fixed $n$, we give a complete classification of the irreducible Artin groups of rank $n$ that are commensurable with the group of type $A_n$. Note that it will remain 6 pairs of groups to compare to get the complete classification of Artin groups of spherical type up to commensur…
Differences in inner ear asymmetry levels between slow-moving and fast-moving primates
2021
International audience; The vestibular system of the inner ear, highly involved in maintaining balance during activities and positional behaviour of animals, has been deeply studied in order to link its morphology with the specific type of locomotion. Previous studies (e.g. Perier et al. 2016, Gonzales et al. 2018) have shown that, in primates, the amount of morphological variation is higher in slow-moving species than in fast-moving ones. These results indicate a lower selective pressure and a reduced functional demand for postural adjustments in the former group, and a higher selective pressure for balance and postural capabilities in the latter. In this study, we assessed if the differen…
Edma 0-6 : educación matemática en la infancia
2018
There are numerous studies that support the interest of starting the development of algebraic thinking in Primary School. In this paper, we present a part of a research project aimed to explore the processes of solution of geometric pattern problems by students in Primary grades 4th to 6th. We analyze the behavior of students who were administered a teaching unit based on the resolution of this type of problems in the GeoPattern application, created by the authors for this purpose. A characteristic of the application is that it informs the students on the correctness of their answers and allows them to respond again to the same question when their answer was wrong. This causes the students …
A Stevedore's protein knot.
2009
Protein knots, mostly regarded as intriguing oddities, are gradually being recognized as significant structural motifs. Seven distinctly knotted folds have already been identified. It is by and large unclear how these exceptional structures actually fold, and only recently, experiments and simulations have begun to shed some light on this issue. In checking the new protein structures submitted to the Protein Data Bank, we encountered the most complex and the smallest knots to date: A recently uncovered α-haloacid dehalogenase structure contains a knot with six crossings, a so-called Stevedore knot, in a projection onto a plane. The smallest protein knot is present in an as yet unclassified …
Differences in the Response to Methacholine Between the Tidal Breathing and Dosimeter Methods
2008
Background It has been postulated that differences in provocative concentration of methacholine causing a 20% fall in FEV 1 (PC 20 ) values between the dosimeter method and tidal breathing method might be due to differences in the dose of agonist delivered to the mouth. The aim of the present study was to determine the influence of the dose of aerosol delivered to the mouth on differences in the response obtained with each challenge method. Methods This study measured airway responsiveness to methacholine by dosimeter method and tidal breathing method in 27 subjects with suspected asthma. The dosimeter was modified to deliver an identical volume to that obtained with the tidal breathing met…