Search results for "racket"
showing 10 items of 132 documents
Quasi-Lie Brackets and the Breaking of Time-Translation Symmetry for Quantum Systems Embedded in Classical Baths
2018
Many open quantum systems encountered in both natural and synthetic situations are embedded in classical-like baths. Often, the bath degrees of freedom may be represented in terms of canonically conjugate coordinates, but in some cases they may require a non-canonical or non-Hamiltonian representation. Herein, we review an approach to the dynamics and statistical mechanics of quantum subsystems embedded in either non-canonical or non-Hamiltonian classical-like baths which is based on operator-valued quasi-probability functions. These functions typically evolve through the action of quasi-Lie brackets and their associated Quantum-Classical Liouville Equations, or through quasi-Lie brackets a…
Hydrophilic primer has double the risk of bracket bond failure
2002
Question: In patients who need orthodontic bracketing is a hydrophilic primer or a conventional primer more effective for bonding? Objective To compare clinical failure rates of brackets bonded with a prototype hydrophilic primer and conventional primer. Design Randomised controlled trial (RCT) in a hospital setting. Intervention A split mouth design was used. Sides were randomly allocated to either hydrophilic (supplied by 3M Unitek (Monrovia, California, USA) or conventional primer (conventional TransbondTM 3M Unitek) adhesive), with the other side having alternative primer. Brackets were applied to 33 patients using a standard procedure. A total of 266 bonds were completed with each prim…
Nambu-Poisson manifolds and associated n-ary Lie algebroids
2001
We introduce an n-ary Lie algebroid canonically associated with a Nambu-Poisson manifold. We also prove that every Nambu-Poisson bracket defined on functions is induced by some differential operator on the exterior algebra, and characterize such operators. Some physical examples are presented.
How Mafia Works: An Analysis of the Extortion Racket System
2014
In this document, we present an analysis of quali-quantitative data on Extortion Rackets in Sicily. The second section provides an introduction to the interpretative framework on Extortion Racket Systems (ERSs). Therefore, the third section takes into account the methodological issues in the collection and analysis of data on extortions. The fourth and five sections offer an analysis on the types of extortion and the correspondent behaviour of the victims, followed by a focus on the process of extortion. An overview of the case-studies analysis on mafia-type organizations ends the document.
Plaque levels of patients with fixed orthodontic appliances measured by digital plaque image analysis
2011
Introduction A digital plaque image analysis system was developed to objectively assess dental plaque formation and coverage in patients treated with fixed orthodontic appliances. Methods The technique was used to assess plaque levels of 52 patients undergoing treatment with fixed appliances in the Department of Orthodontics at Johannes Gutenberg University in Mainz, Germany. Results Plaque levels ranged from 5.1% to 85.3% of the analyzed tooth areas. About 37% of the patients had plaque levels over 50% of the dentition, but only 10% exhibited plaque levels below 15% of tooth coverage. The mean plaque coverage was 41.9% ± 18.8%. Plaque was mostly present along the gum line and around the or…
Key Physical Factors in the Serve Velocity of Male Professional Wheelchair Tennis Players
2021
The aim of this study was to identify the physical factors related to serve speed in male professional wheelchair tennis players (WT). Nine best nationally-ranked Spanish male wheelchair tennis players (38.35 ± 11.28 years, 63.77 ± 7.01 kg.) completed a neuromuscular test battery consisting of: isometric handgrip strength
Ball Impact Position in Recreational Male Padel Players: Implications for Training and Injury Management
2021
Racket sports such as padel are characterized by the repetition of unilateral gestures, which can lead to negative adaptations like asymmetries or overuse musculoskeletal injuries. The purpose of this study was to determine the differences in ball impact positions (i.e., forward or backward of the center of gravity) in nine stroke types in a sample of forty-eight recreational male padel players. The sample included 14,478 shots corresponding to 18 matches from six tournaments. Forty-eight male padel players were classified into two groups according to their level: trained (n = 24) and novice (n = 24). Type of stroke and ball impact position were registered using a computerized motion tracki…
The effect of surface treatment with Er: YAG laser on shear bond strength of orthodontic brackets to fiber-reinforced composite
2014
Objectives: This study aimed to investigate the effect of surface treatment with Er:YAG laser on shear bond strength (SBS) of orthodontic brackets to fiber-reinforced composite (FRC). Study Design: Ninety human premolars were randomly divided into six groups of 15. FRC bars were bonded to the teeth with a flowable composite (FC) and then underwent following treatments. In group 1 no further treatment was performed. In group 2 the FRC surfaces were covered by FC. An Er:YAG laser was employed to treat FRCs in groups 3 ( 200 mJ/10 Hz) and 4 (300 mJ/15 Hz). The FRC strips in groups 5 and 6 were first covered by FC and then irradiated with Er:YAG laser at 200 mJ/10 Hz (group 5) or 300 mJ/15 Hz (…
Casein phosphopeptide-amorphous calcium phosphate effects on brackets shear bond strength and enamel damage
2017
Background The aim of study was to evaluate the application of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and fluoride regarding their effect on the shear bond strength (SBS), bond failure pattern of brackets using the adhesive remnant index (ARI) and assessing the quality of enamel surface using the enamel damage index (EDI). Material and methods Sixty extracted premolar teeth were randomly divided into four groups regarding pretreatment application of CPP-ACP and fluoride. Brackets were bonded using the conventional method. Specimens were thermocycled for 1000 cycles and were subsequently tested for the SBS in a universal testing machine. After debonding, the teeth were e…
Resistance of bonded premolars to four artificial ageing models post enamel conditioning with a novel calcium-phosphate paste
2020
Background This in vitro study compares a novel calcium-phosphate etchant paste to conventional 37% phosphoric acid gel for bonding metal and ceramic brackets by evaluating the shear bond strength, remnant adhesive and enamel damage following water storage, acid challenge and fatigue loading. Material and Methods Metal and ceramic brackets were bonded to 240 extracted human premolars using two enamel conditioning protocols: conventional 37% phosphoric acid (PA) gel (control), and an acidic calcium-phosphate (CaP) paste. The CaP paste was prepared from β-tricalcium phosphate and monocalcium phosphate monohydrate powders mixed with 37% phosphoric acid solution, and the resulting phase was con…