Search results for "geometry."
showing 10 items of 4386 documents
On the minimal number of singular fibers with non-compact Jacobians for families of curves over P1
2016
Abstract Let f : X → P 1 be a non-isotrivial family of semi-stable curves of genus g ≥ 1 defined over an algebraically closed field k. Denote by s nc the number of the singular fibers whose Jacobians are non-compact. We prove that s nc ≥ 5 if k = C and g ≥ 5 ; we also prove that s nc ≥ 4 if char ( k ) > 0 and the relative Jacobian of f is non-smooth.
Analysis of normal human retinal vascular network architecture using multifractal geometry
2017
AIM To apply the multifractal analysis method as a quantitative approach to a comprehensive description of the microvascular network architecture of the normal human retina. METHODS Fifty volunteers were enrolled in this study in the Ophthalmological Clinic of Cluj-Napoca, Romania, between January 2012 and January 2014. A set of 100 segmented and skeletonised human retinal images, corresponding to normal states of the retina were studied. An automatic unsupervised method for retinal vessel segmentation was applied before multifractal analysis. The multifractal analysis of digital retinal images was made with computer algorithms, applying the standard box-counting method. Statistical analyse…
Generalized Thru-Reflect-Line Calibration Technique for the Measurement of Multimodal Radiating Waveguides
2017
The objective of this letter is to extend the use of the generalized thru-reflect-line measurement technique to the case of a radiating multimodal rectangular waveguide aperture. Although this radiating aperture has been carefully studied from a theoretical point of view, the relevant experimental characterization has been limited to the case where the feeding waveguide is monomodal. In addition to theory, we also present experimental results that agree quite well with full-wave simulations, thereby fully validating the measurement technique.
Credibility to attract, trust to stay: the mediating role of trust in improving brand congruence in sports services
2021
This research aims to demonstrate the mediating role of brand trust in the relationship between credibility and users' congruence with a sports services brand. The analysis was carried out using EQS 6.3 to perform the four required steps of the analysis (and the Sobel test was conducted for a public sports service and a private sports service. The results confirm the full mediation effect of brand trust in the case of the private service and a partial mediation for the public service. Therefore, this study confirms that credibility, in the presence of trust, ceases to have an influence on the congruence of users with the brand, which suggests that credibility is important at an initial stag…
Structural commonalities and deviations in the hierarchical organization of crossed-lamellar shells: A case study on the shell of the bivalve Glycyme…
2016
11 pages; International audience; The structural organization of the palliostracum—the dominant part of the shell which is formed by the mantle cells—of Glycymeris glycymeris (Linné 1758) is comprised of five hierarchical levels with pronounced structural commonalities and deviations from other crossed-lamellar shells. The hierarchical level known as second order lamellae, present within other crossed-lamellar shells, is absent highlighting a short-coming of the currently used nomenclature. On the mesoscale, secondary microtubules penetrate the palliostracum and serve as crack arrestors. Moreover, the growth lamellae follow bent trajectories possibly impacting crack propagation, crack defle…
Induced post-traumatic apexification: 20 year follow-up and morphological study after new fracture.
2018
Apexification is an endodontic technique used in immature necrotic teeth, the primary goal of which is to induce a calcified barrier in roots with open apices and to promote the continuation of apical root development. A 7-year-old patient with a coronal fracture in a maxillary central incisor was treated with an apexification technique using calcium hydroxide. The apical closure was obtained after one year, then a permanent root canal filling was performed. The tooth was monitored for a period of 20 years, up to when a trauma caused its extraction. The newly formed root was analyzed macroscopically, histologically and through scanning electron microscopy. A morphologically normal root was …
Crack formation and cleaving of sapphire with ultrafast bessel beams
2017
Sapphire is a transparent crystalline dielectric of high hardness with many important applications, specifically to the next-generation touchscreens and to the LED growth, as substrates. However, sapphire cutting by ablative techniques is rather slow therefore fast material separation techniques are needed. Material separation by “stealth dicing” has been recently developed, it is based on material cleaving along a plane weakened by multiple ultrafast laser illuminations. This allows usually generating taper-free cutting and avoids material loss. However, the illuminated plane needs small spacing between the shot to shot (typically a few μm) and long damages inside the bulk. This requires l…
Three-dimensional analysis of the physiological foramen geometry of maxillary and mandibular molars by means of micro-CT.
2017
The aim of this study was to investigate the physiological foramen diameter, shape and distance between physiological and anatomical apex of maxillary and mandibular first and second molars. Accurate knowledge of the physiological foramina morphology; thus, inherent mechanical shaping technical hindrances, is decisive when taking the corresponding root canal final preparation decision. The morphological dimensions of a total of 1727 physiological foramina were investigated by means of micro-computed tomography. Mean narrow and wide (to a high number, oval) diameters of the physiological foramen were 0.24, 0.22 and 0.33 mm and 0.33, 0.31 and 0.42 mm in mesiobuccal (MB), distobuccal (DB) and …
On the growth and form of cortical convolutions
2016
International audience; The rapid growth of the human cortex during development is accompanied by the folding of the brain into a highly convoluted structure1-3. Recent studies have focused on the genetic and cellular regulation of cortical growth4-8, but understanding the formation of the gyral and sulcal convolutions also requires consideration of the geometry and physical shaping of the growing brain9-15. To study this, we use magnetic resonance images to build a 3D-printed layered gel mimic of the developing smooth fetal brain; when immersed in a solvent, the outer layer swells relative to the core, mimicking cortical growth. This relative growth puts the outer layer into mechanical com…
Retrieving infinite numbers of patterns in a spin-glass model of immune networks
2013
The similarity between neural and immune networks has been known for decades, but so far we did not understand the mechanism that allows the immune system, unlike associative neural networks, to recall and execute a large number of memorized defense strategies {\em in parallel}. The explanation turns out to lie in the network topology. Neurons interact typically with a large number of other neurons, whereas interactions among lymphocytes in immune networks are very specific, and described by graphs with finite connectivity. In this paper we use replica techniques to solve a statistical mechanical immune network model with `coordinator branches' (T-cells) and `effector branches' (B-cells), a…