1,268 research outputs found
Containment versus impingement: finding a compromise for cup placement in total hip arthroplasty
Recommendations for cup containment and impingement may provide conflicting directions for component orientation in total hip arthroplasty. For optimal containment, the cup is positioned with respect to the acetabular bone, resulting in coincidence of the rim of the cup and the acetabulum. This results in good coverage and symmetric load transfer, leading to good long-term stability, but occasionally necessitates more abduction of the cup than that recommended by the safe zone. On the other hand, placement of the cup for an optimal range of motion would lead to only partial containment, with a higher risk of component loosening and revision. The most effective compromise is to use a prosthesis that has a large safe zone, realised by a high head-to-neck ratio, and orienting the cup such that a good containment is achieved and the safe zone is respected. Computer navigation or smart aiming devices may help to find the best relative orientatio
Monitoring of Carboxypeptidase Digestion by Matrix-Assisted Laser Desorption and Ionization Mass Spectrometry
The potential of matrix-assisted laser desorption and ionization mass spectrometry (LDI-MS) is demonstrated by monitoring and analyzing the digestion of (human) pTH (1â34), a synthetic peptide with carboxypeptidases Y and B. All occurring ion signals in the mass spectra could
be identified as degraded peptides. By calculating the mass differences between successive degraded peptides, it was possible to identify the released amino acids and to determine 8 amino acids of the C-terminus of the original peptide. For a single MS measurement, only 2 pmol of substrate
was needed. Time-course analysis of the cleavage of the first amino acid residue gave insight into the kinetics involved. These measurements strongly support the hope that quantitative information about concentrations can be extracted from LDI-MS
Shuntchirurgie in Europa und den USA: Ein kritischer Vergleich
Zusammenfassung: Nach einem anfĂ€nglich gemeinsamen Weg in der Fistelchirurgie begann in den USA ab etwa 1975 der bevorzugte Einsatz von Prothesenshunts. In bis zu 80% wurden bei Erstoperationen GefĂ€Ăprothesen implantiert, mit entsprechend hoher Komplikationsrate und hohen Folgekosten. Europa pflegte, mit lokalen Unterschieden, das Konzept der vorzugsweisen Verwendung von arteriovenösen Fisteln weiter (AVF). Der Prothesenanteil war nie höher als 40%. UnterstĂŒtzt von Richtlinien, versuchen die USA seit 1997 einen deutlichen Umschwung herbeizufĂŒhren. Der Anteil primĂ€rer AVF ist seither angestiegen, bei allerdings wohl erhöhter initialer Versagerquote im internationalen Vergleich. Ăber Richtlinien hinaus sollte fĂŒr beide Kontinente als vordringliche Aufgaben die interdisziplinĂ€re Zusammenarbeit aller beteiligten Fachgebiete gelten: DurchfĂŒhrung zertifizierter, interdisziplinĂ€rer Kurse mit konsensfĂ€higen Inhalten, Einrichtung von Referenzzentren mit einheitlicher, umfassender Dokumentation, Aufbau von Datenbanken zur QualitĂ€tskontrolle mit abrufbaren Komplikations- und Funktionsraten, Standardisierung der Ăberwachung von GefĂ€ĂzugĂ€ngen im Dialysezentru
Evaluation of range of motion restriction within the hip joint
In Total Hip Arthroplasty, determining the impingement free range of motion requirement is a complex task. This is because in the native hip, motion is restricted by both impingement as well as soft tissue restraint. The aim of this study is to determine a range of motion benchmark which can identify motions which are at risk from impingement and those which are constrained due to soft tissue. Two experimental methodologies were used to determine motions which were limited by impingement and those motions which were limited by both impingement and soft tissue restraint. By comparing these two experimental results, motions which were limited by impingement were able to be separated from those motions which were limited by soft tissue restraint. The results show motions in extension as well as flexion combined with adduction are limited by soft tissue restraint. Motions in flexion, flexion combined with abduction and adduction are at risk from osseous impingement. Consequently, these motions represent where the maximum likely damage will occur in femoroacetabular impingement or at most risk of prosthetic impingement in Total Hip Arthroplasty
The surface science of quasicrystals
The surfaces of quasicrystals have been extensively studied since about 1990. In this paper we review work on the structure and morphology of clean surfaces, and their electronic and phonon structure. We also describe progress in adsorption and epitaxy studies. The paper is illustrated throughout with examples from the literature. We offer some reflections on the wider impact of this body of work and anticipate areas for future development.
(Some figures in this article are in colour only in the electronic version
Detecting change via competence model
In real world applications, interested concepts are more likely to change rather than remain stable, which is known as concept drift. This situation causes problems on predictions for many learning algorithms including case-base reasoning (CBR). When learning under concept drift, a critical issue is to identify and determine "when" and "how" the concept changes. In this paper, we developed a competence-based empirical distance between case chunks and then proposed a change detection method based on it. As a main contribution of our work, the change detection method provides an approach to measure the distribution change of cases of an infinite domain through finite samples and requires no prior knowledge about the case distribution, which makes it more practical in real world applications. Also, different from many other change detection methods, we not only detect the change of concepts but also quantify and describe this change. © 2010 Springer-Verlag
Efficient Resolution of Anisotropic Structures
We highlight some recent new delevelopments concerning the sparse
representation of possibly high-dimensional functions exhibiting strong
anisotropic features and low regularity in isotropic Sobolev or Besov scales.
Specifically, we focus on the solution of transport equations which exhibit
propagation of singularities where, additionally, high-dimensionality enters
when the convection field, and hence the solutions, depend on parameters
varying over some compact set. Important constituents of our approach are
directionally adaptive discretization concepts motivated by compactly supported
shearlet systems, and well-conditioned stable variational formulations that
support trial spaces with anisotropic refinements with arbitrary
directionalities. We prove that they provide tight error-residual relations
which are used to contrive rigorously founded adaptive refinement schemes which
converge in . Moreover, in the context of parameter dependent problems we
discuss two approaches serving different purposes and working under different
regularity assumptions. For frequent query problems, making essential use of
the novel well-conditioned variational formulations, a new Reduced Basis Method
is outlined which exhibits a certain rate-optimal performance for indefinite,
unsymmetric or singularly perturbed problems. For the radiative transfer
problem with scattering a sparse tensor method is presented which mitigates or
even overcomes the curse of dimensionality under suitable (so far still
isotropic) regularity assumptions. Numerical examples for both methods
illustrate the theoretical findings
Dolphins at the British Museum: Zoomorphic Calusa Sinkers
The subject of everyday or âmundaneâ artistic expression in Native American material culture does not always take into account the idea that aesthetic design can have explicit practical as well as decorative function. This article explores this idea through objects from the Floridian archaeological collections at the British Museum
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