Search results for "Retraction"

Eigenvectors of k–ψ-contractive wedge operators

AbstractWe present new boundary conditions under which the fixed point index of a strict-ψ-contractive wedge operator is zero. Then we investigate eigenvalues and corresponding eigenvectors of k–ψ-contractive wedge operators.

Proper $k$-ball-contractive mappings in $C_b^m[0, + infty)$

2021

In this paper we deal with the Banach space C-b(m)[0,+infinity] of all m-times continuously derivable, bounded with all derivatives up to the order m, real functions defined on [0, +infinity). We prove, for any epsilon > 0, the existence of a new proper k-ball-contractive retraction with k < 1+epsilon of the closed unit ball of the space onto its boundary, so that the Wosko constant W-gamma(C-b(m)[0,+infinity]) is equal to 1.

MR2370688 (2009e:46013) Navarro-Pascual, J. C.; Mena-Jurado, J. F.; Sánchez-Lirola, M. G. A two-dimensional inequality and uniformly continuous retra…

2009

Let X be an infinite-dimensional uniformly convex Banach space and let BX and SX be its closed unit ball and unit sphere, respectively. The main result of the paper is that the identity mapping on BX can be expressed as the mean of n uniformly continuous retractions from BX onto SX for every n >= 3. Then, the authors observe that the result holds under a property weaker than uniform convexity, satisfied by any complex Banach space, so that the result generalizes that of [A. Jim´enez-Vargas et al., Studia Math. 135 (1999), no. 1, 75–81; MR1686372 (2000b:46025)]. As an application the extremal structure of spaces of vector-valued uniformly continuous mappings is studied.

On k-ball contractive retractions in F-normed ideal spaces

2010

Let X be an infinite dimensional F-normed space and r a positive number such that the closed ball B_r(X) of radius r is properly contained in X. For a bounded subset A of X, the Hausdorff measure of noncompactness gamma(A) of A is the infimum of all $\eps >0$ such that A has a finite $\eps$-net in X. A retraction R of B_r(X) onto its boundary is called k-ball contractive if $\gamma(RA) \le k \gamma(A)$ for each subset A of B_r(X). The main aim of this talk is to give examples of regular F-normed ideal spaces in which there is a 1-ball contractive retraction or, for any $\eps>0$, a $(1+ \eps)$-ball contractive retraction with positive lower Hausdorff measure of noncompactness.

Mastoidectomy in surgical procedures to treat retraction pockets: a single-center experience and review of the literature

2022

Abstract Purpose Retraction pocket (RP) is a common event affecting the middle ear when a negative pressure within it causes a retraction of a single part of the tympanic membrane (TM). Patients can be asymptomatic or can experience hearing loss, fullness feeling and/or ear discharge. RP can be stable or develop a cholesteatoma; aim of the study was to investigate if mastoidectomy may play a role in the surgical management of patients suffering from RP, both reporting our experience and discussing the existing literature. Methods Fifty-one patients affected by RP were referred for surgery and randomly divided into two groups. Patients of G1 group underwent tympanoplasty with mastoidectomy, …

Optimal retraction problem for proper $k$-ball-contractive mappings in $C^m [0,1]$

2019

In this paper for any $\varepsilon >0$ we construct a new proper $k$-ball-contractive retraction of the closed unit ball of the Banach space $C^m [0,1]$ onto its boundary with $k < 1+ \varepsilon$, so that the Wośko constant $W_\gamma (C^m [0,1])$ is equal to $1$.

Comparison of the effect of different medicaments on surface reproduction of two commercially available Polyvinyl Siloxane impression materials - An …

2013

Objective:To determine the effect of different retraction cord medicaments on surface detail reproduction of polyvinyl siloxane impression materials and compare this effect on any two brands of commercially available polyvinyl siloxane impression materials. Material and methods: Four stainless steel dies were made according to ADA specification no.19. Three dies were treated with aluminium chloride (5%), ferric sulphate (13.3%) and epinephrine (0.1%) while the fourth one was left untreated to serve as control. Two impression materials (Dentsply and 3M ESPE) were used. Results: All the three medicaments adversely affected the surface detail reproduction of both the brands of the polyvinyl si…

Preliminary study about the efficiency of diode laser compared with retraction cords used for exposing the finishing lines of dental abutments before…

2016

Gingival displacement using diode laser or retraction cords: A comparative clinical study.

2018

PURPOSE: To compare two systems used for conditioning the gingival sulcus and exposing the finish line before the final impression for a fixed denture: retraction cords and diode laser. METHODS: All subjects participating in the study had healthy gingival and periodontal status before intervention for fixed prosthesis. 74 abutments for complete crown restoration were randomly divided into two groups for displacing the gingival sulcus before the final impression: gingival retraction cords (RC) and diode laser (DL). The height of the clinical crowns was measured by a blinded examiner in three points of the buccal surface (mesial, midline and distal) at four different times: after tooth prepar…

Retracted: Targeting Mitochondria as Therapeutic Strategy for Metabolic Disorders.

2019

Mitochondria are critical regulator of cell metabolism; thus, mitochondrial dysfunction is associated with many metabolic disorders. Defects in oxidative phosphorylation, ROS production, or mtDNA mutations are the main causes of mitochondrial dysfunction in many pathological conditions such as IR/diabetes, metabolic syndrome, cardiovascular diseases, and cancer. Thus, targeting mitochondria has been proposed as therapeutic approach for these conditions, leading to the development of small molecules to be tested in the clinical scenario. Here we discuss therapeutic interventions to treat mitochondrial dysfunction associated with two major metabolic disorders, metabolic syndrome, and cancer. …