scholarly journals Surgical reconstruction of semilunar valves in the growing child: Should we mimic the venous valve? A simulation study

2017 ◽  
Vol 153 (2) ◽  
pp. 389-396 ◽  
Author(s):  
Peter E. Hammer ◽  
Erin G. Roberts ◽  
Sitaram M. Emani ◽  
Pedro J. del Nido
Keyword(s):  
Simulation Study ◽  
Surgical Reconstruction ◽  
Venous Valve ◽  
Semilunar Valves

Effects of compression during formation on the microstructure of composite hydroxylapatite/plaster implants for bone reconstruction

1988 ◽  
Vol 46 ◽  
pp. 750-751
Author(s):  
J. Hanker ◽  
K. Cowden ◽  
R. Noecker ◽  
P. Yates ◽  
N. Georgiade ◽  
...  
Keyword(s):  
Cosmetic Surgery ◽  
Glass Plate ◽  
Surgical Reconstruction ◽  
Equal Weight ◽  
Sintered Ceramic ◽  
Setting Times ◽  
Excess Water ◽  
Mixture Prior ◽  
Mechanical Strengths ◽  
Calcium Sulfate Hemihydrate

Composites of plaster of Paris (PP) and hydroxylapatite (HA) particles are being applied for the surgical reconstruction of craniofacial bone defects and for cosmetic surgery. Two types of HA particles are being employed, the dense sintered ceramic (DHA) and the porous, coralline hydroxylapatite (PHA) particles. Excess water is expressed out of the moistened HA/PP mixture prior to implantation and setting by pressing it in a non-tapered syringe against a glass plate. This results in implants with faster setting times and greater mechanical strengths. It was therefore of interest to compare samples of the compressed versus noncompressed mixtures to see whether or not any changes in their microstructure after setting could be related to these different properties.USG Medical Grade Calcium Sulfate Hemihydrate (which has the lowest mortar consistency of any known plaster) was mixed with an equal weight of Interpore 200 particles (a commercial form of PHA). After moistening with a minimum amount of water, disc-shaped noncompressed samples were made by filling small holes (0.339 in. diameter x 0.053 in. deep) in polypropylene molds with a microspatula.

Some quantitative applications of vascular corrosion casting

1992 ◽  
Vol 50 (1) ◽  
pp. 738-739
Author(s):  
Fred E. Hossler
Keyword(s):  
Blood Vessels ◽  
Nuclear Orientation ◽  
Three Dimensional ◽  
Surrounding Tissue ◽  
Confocal Laser ◽  
Corrosion Casting ◽  
Venous Valve ◽  
Casting Technique ◽  
Low Viscosity ◽  
Quantitative Measurements

Preparation of replicas of the complex arrangement of blood vessels in various organs and tissues has been accomplished by infusing low viscosity resins into the vasculature. Subsequent removal of the surrounding tissue by maceration leaves a model of the intricate three-dimensional anatomy of the blood vessels of the tissue not obtainable by any other procedure. When applied with care, the vascular corrosion casting technique can reveal fine details of the microvasculature including endothelial nuclear orientation and distribution (Fig. 1), locations of arteriolar sphincters (Fig. 2), venous valve anatomy (Fig. 3), and vessel size, density, and branching patterns. Because casts faithfully replicate tissue vasculature, they can be used for quantitative measurements of that vasculature. The purpose of this report is to summarize and highlight some quantitative applications of vascular corrosion casting. In each example, casts were prepared by infusing Mercox, a methyl-methacrylate resin, and macerating the tissue with 20% KOH. Casts were either mounted for conventional scanning electron microscopy, or sliced for viewing with a confocal laser microscope.

589: Tissue Engineered Tubularized Urethra for Surgical Reconstruction: A Pre-Clinical Study

2007 ◽  
Vol 177 (4S) ◽  
pp. 197-197 ◽  
Author(s):  
Hazem O. Orabi ◽  
Tamer A. Aboushwareb ◽  
Yuan Yuan Zhang ◽  
James J. Yoo ◽  
Anthony Atala
Keyword(s):  
Clinical Study ◽  
Surgical Reconstruction

Surgical reconstruction for unilateral iliac artery lesions in patients younger than 50 years

VASA ◽  
2011 ◽  
Vol 40 (6) ◽  
pp. 474-481 ◽  
Author(s):  
Radak ◽  
Babic ◽  
Ilijevski ◽  
Jocic ◽  
Aleksic ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Limb Salvage ◽  
Iliac Artery ◽  
Graft Patency ◽  
Long Term Results ◽  
Surgical Reconstruction ◽  
Safe Procedure ◽  
Term Survival

Background: To evaluate safety, short and long-term graft patency, clinical success rates, and factors associated with patency, limb salvage and mortality after surgical reconstruction in patients younger than 50 years of age who had undergone unilateral iliac artery bypass surgery. Patients and methods: From January 2000 to January 2010, 65 consecutive reconstructive vascular operations were performed in 22 women and 43 men of age < 50 years with unilateral iliac atherosclerotic lesions and claudication or chronic limb ischemia. All patients were followed at 1, 3, 6, and 12 months after surgery and every 6 months thereafter. Results: There was in-hospital vascular graft thrombosis in four (6.1 %) patients. No in-hospital deaths occurred. Median follow-up was 49.6 ± 33 months. Primary patency rates at 1-, 3-, 5-, and 10-year were 92.2 %, 85.6 %, 73.6 %, and 56.5 %, respectively. Seven patients passed away during follow-up of which four patients due to coronary artery disease, two patients due to cerebrovascular disease and one patient due to malignancy. Limb salvage rate after 1-, 3-, 5-, and 10-year follow-up was 100 %, 100 %, 96.3 %, and 91.2 %, respectively. Cox regression analysis including age, sex, risk factors for vascular disease, indication for treatment, preoperative ABI, lesion length, graft diameter and type of pre-procedural lesion (stenosis/occlusion), showed that only age (beta - 0.281, expected beta 0.755, p = 0.007) and presence of diabetes mellitus during index surgery (beta - 1.292, expected beta 0.275, p = 0.026) were found to be significant predictors of diminishing graft patency during the follow-up. Presence of diabetes mellitus during index surgery (beta - 1.246, expected beta 0.291, p = 0.034) was the only variable predicting mortality. Conclusions: Surgical treatment for unilateral iliac lesions in patients with premature atherosclerosis is a safe procedure with a low operative risk and acceptable long-term results. Diabetes mellitus and age at index surgery are predictive for low graft patency. Presence of diabetes is associated with decreased long-term survival.

An Alternative to Cohen's κ

2006 ◽  
Vol 11 (1) ◽  
pp. 12-24 ◽  
Author(s):  
Alexander von Eye
Keyword(s):  
Simulation Study ◽  
Null Hypothesis ◽  
Categorical Variables ◽  
Alternative Measure ◽  
Rater Agreement ◽  
Verbal Processing ◽  
Heavy Tailed ◽  
Applicant Selection

At the level of manifest categorical variables, a large number of coefficients and models for the examination of rater agreement has been proposed and used. The most popular of these is Cohen's κ. In this article, a new coefficient, κ s , is proposed as an alternative measure of rater agreement. Both κ and κ s allow researchers to determine whether agreement in groups of two or more raters is significantly beyond chance. Stouffer's z is used to test the null hypothesis that κ s = 0. The coefficient κ s allows one, in addition to evaluating rater agreement in a fashion parallel to κ, to (1) examine subsets of cells in agreement tables, (2) examine cells that indicate disagreement, (3) consider alternative chance models, (4) take covariates into account, and (5) compare independent samples. Results from a simulation study are reported, which suggest that (a) the four measures of rater agreement, Cohen's κ, Brennan and Prediger's κ n , raw agreement, and κ s are sensitive to the same data characteristics when evaluating rater agreement and (b) both the z-statistic for Cohen's κ and Stouffer's z for κ s are unimodally and symmetrically distributed, but slightly heavy-tailed. Examples use data from verbal processing and applicant selection.

Comparison of Principal Component Solutions in Two Populations

Methodology ◽  
2016 ◽  
Vol 12 (1) ◽  
pp. 11-20 ◽  
Author(s):  
Gregor Sočan
Keyword(s):  
Simulation Study ◽  
Principal Components ◽  
Common Factor ◽  
Principal Component ◽  
Component Model ◽  
Bootstrap Procedure ◽  
Factor Loadings ◽  
Component Loadings ◽  
Principal Component Model ◽  
Two Populations

Abstract. When principal component solutions are compared across two groups, a question arises whether the extracted components have the same interpretation in both populations. The problem can be approached by testing null hypotheses stating that the congruence coefficients between pairs of vectors of component loadings are equal to 1. Chan, Leung, Chan, Ho, and Yung (1999) proposed a bootstrap procedure for testing the hypothesis of perfect congruence between vectors of common factor loadings. We demonstrate that the procedure by Chan et al. is both theoretically and empirically inadequate for the application on principal components. We propose a modification of their procedure, which constructs the resampling space according to the characteristics of the principal component model. The results of a simulation study show satisfactory empirical properties of the modified procedure.

Assessing Person Fit With the Information Matrix Test

Methodology ◽  
2015 ◽  
Vol 11 (1) ◽  
pp. 3-12 ◽  
Author(s):  
Jochen Ranger ◽  
Jörg-Tobias Kuhn
Keyword(s):  
Simulation Study ◽  
Type I Error ◽  
Information Matrix ◽  
Small Samples ◽  
Type I ◽  
Person Fit ◽  
Power Of The Test ◽  
Order Expansion ◽  
Trait Stability ◽  
Information Matrix Test

In this manuscript, a new approach to the analysis of person fit is presented that is based on the information matrix test of White (1982) . This test can be interpreted as a test of trait stability during the measurement situation. The test follows approximately a χ2-distribution. In small samples, the approximation can be improved by a higher-order expansion. The performance of the test is explored in a simulation study. This simulation study suggests that the test adheres to the nominal Type-I error rate well, although it tends to be conservative in very short scales. The power of the test is compared to the power of four alternative tests of person fit. This comparison corroborates that the power of the information matrix test is similar to the power of the alternative tests. Advantages and areas of application of the information matrix test are discussed.

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