Search results for "racket"

The exterior derivative as a Killing vector field

1996

Among all the homogeneous Riemannian graded metrics on the algebra of differential forms, those for which the exterior derivative is a Killing graded vector field are characterized. It is shown that all of them are odd, and are naturally associated to an underlying smooth Riemannian metric. It is also shown that all of them are Ricci-flat in the graded sense, and have a graded Laplacian operator that annihilates the whole algebra of differential forms.

In vitro comparison of the retention capacity of new aesthetic brackets.

1999

Tensile bond strength and bond failure location were evaluated in vitro for two types of aesthetic brackets (non-silanated ceramic, polycarbonate) and one stainless steel bracket, using bovine teeth as the substrate and diacrylate resin as the adhesive. The results show that metallic bracket had the highest bond strength (13.21 N) followed by the new plastic bracket (12.01 N), which does not require the use of a primer. The non-silanated ceramic bracket produced the lowest bond strength (8.88 N). Bond failures occurred mainly between bracket and cement, although a small percentage occurred between the enamel-cement interface with the metal and plastic brackets and within the cement for the …

Osseointegration of miniscrews: a histomorphometric evaluation.

2007

SUMMARY Mini-implants and miniscrews are commonly used in orthodontics to provide additional temporary intraoral anchorage. Partial osseointegration represents a distinct advantage in orthodontic applications, allowing effective anchorage to be combined with easy insertion and removal. This article reports the histomorphometric fi ndings of the osseointegration of bracket screw bone anchors (BSBAs). In an experimental animal study, four BSBAs were inserted in the alveolar process of the lower jaw in each of fi ve male beagle dogs, aged 6.5 months from the same mother. Eleven screws were lost during the study, nine of them due to lack of primary stability. One screw was removed at the end of…

Disinclusion of unerupted teeth by mean of self-ligating brackets: Effect of blood contamination on shear bond strength

2012

Objectives: The aim of this study was to assess the effect of blood contamination on the shear bond strength and failure site of three different orthodontic self-ligating brackets. Study Design: 240 bovine permanent mandibular incisors were randomly divided into 12 groups of 20 specimens each. Orthodontic self-ligating brackets were tested under four different enamel surface conditions: a) dry, b) blood contamination before priming, c) blood contamination after priming, d) blood contamination before and after priming. Brackets were bonded to the teeth and subsequently tested using a Instron universal testing machine. Shear bond strength values and adhesive failure rate were recorded. Statis…

Note minime in tema di rapporti fra disciplina fallimentare e normativa antiracket/antiusura.

2010

Polynomial Identities and Asymptotic Methods

2005

Polynomial identities and PI-algebras $S_n$-representations Group gradings and group actions Codimension and colength growth Matrix invariants and central polynomials The PI-exponent of an algebra Polynomial growth and low PI-exponent Classifying minimal varieties Computing the exponent of a polynomial $G$-identities and $G\wr S_n$-action Superalgebras, *-algebras and codimension growth Lie algebras and nonassociative algebras The generalized-six-square theorem Bibliography Index.

Resisting the extortion racket: an empirical analysis

2018

While the contributions on the organized crime and Mafia environments are many, there is a lack of empirical evidence on the firm’s decision to resist to extortion. Our case study is based on Addiopizzo, an NGO that, from 2004, invites firms to refuse requests from the local Mafia and to join a public list of “non-payers”. The research is based on a dataset obtained linking the current administrative archives maintained by the chambers of commerce and the list updated by the NGO. The objective of this paper is twofold: first, to gather sound data on the characteristics of the Addiopizzo joiners; second to model the probability to join Addiopizzo by a two-level logistic regression model. We …

Эмануэль Гринберг - выдающиеся достижения в прикладной математике: радио-фильтры, корпуса танкеров, графы и интегральные схемы Emanuels Grinbergs - i…

2018

The paper is dedicated to the 50th anniversary of the Grinberg theorem. The main works of Emanuel Grinberg (1911-1982) in applied mathematics are described, following the stages of his life path, namely: the design of radio receivers and the calculation of radio filters (1949-1959), hull of tanker calculations (1962-1964), the study of graph theory and the proof of the Grinberg theorem (1968), designing of integrated circuits (1968-1980). Calculations of radio filters are associated with the expansion of the use of continued fractions for the analysis of linear electric circuits (the Kauer model) and the developing of new tools – the Grinberg brackets (as an extension of the Euler brackets)…

Effect of high-fluoride dentifrice and bracket bonding composite material on enamel demineralization adjacent to orthodontic brackets in vitro

2020

Background There is a lack of information about the association of high-fluoride dentrifrice and fluoride-containing bonding material to prevent enamel white spot lesions development adjacent to brackets. The aim of this in vitro study was to evaluate the effect of high-fluoride dentifrice and fluoride-containing bonding material on enamel demineralization adjacent to orthodontic brackets. Material and methods Forty-eight enamel specimens with 7x7x2 mm were obtained from bovine incisors. Orthodontic brackets were bonded with fluoride-containing resin composite (OrthoCem®) or fluoride-free low viscosity resin. The specimens were submitted to an 8-day pH cycling that consisted in the daily im…

Existence and uniqueness of solutions to superdifferential equations

1993

Abstract We state and prove the theorem of existence and uniqueness of solutions to ordinary superdifferential equations on supermanifolds. It is shown that any supervector field, X = X0 + X1, has a unique integral flow, Г: R 1¦1 x (M, AM) → (M, AM), satisfying a given initial condition. A necessary and sufficient condition for this integral flow to yield an R 1¦1-action is obtained: the homogeneous components, X0, and, X1, of the given field must define a Lie superalgebra of dimension (1, 1). The supergroup structure on R 1¦1, however, has to be specified: there are three non-isomorphic Lie supergroup structures on R 1¦1, all of which have addition as the group operation in the underlying …