The Experts below are selected from a list of 243 Experts worldwide ranked by ideXlab platform
Manuel Hohmann - One of the best experts on this subject based on the ideXlab platform.
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Post-Newtonian limit of generalized scalar-torsion theories of gravity
Physical Review D, 2020Co-Authors: Kai Flathmann, Manuel HohmannAbstract:In this article we derive the post-Newtonian limit of a class of teleparallel theories of gravity, where the action is a Free Function $L(T,X,Y,\phi)$ of the Torsion scalar $T$ and scalar quantities $X$ and $Y$ built from the dynamical scalar field $\phi$. We restrict the analysis to a massless scalar field in order to use the parameterized post-Newtonian formalism without modifications, such as introducing an effective gravitational constant which depends on the distance between the interacting masses. In particular the results show a class of fully-conservative theories of gravity, where the only non-vanishing parameters are $\gamma$ and $\beta$. For a particular choice of the Function $L(T,X,Y,\phi)$ the theory cannot be distinguished from General Relativity in its post-Newtonian approximation.
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Parametrized post-Newtonian limit of general teleparallel gravity theories
Physical Review D, 2019Co-Authors: Ulbossyn Ualikhanova, Manuel HohmannAbstract:We derive the post-Newtonian limit of a general class of teleparallel gravity theories, whose action is given by a Free Function of three scalar quantities obtained from the torsion of the teleparallel connection. This class of theories is chosen to be sufficiently generic in order to include the $f(T)$ class of theories as well as new general relativity as subclasses. To derive its post-Newtonian limit, we first impose the Weitzenb\"ock gauge, and then introduce a post-Newtonian approximation of the tetrad field around a Minkowski background solution. Our results show that the class of theories we consider is fully conservative, with only the parameters $\beta$ and $\gamma$ potentially deviating from their general relativity values. In particular, we find that the post-Newtonian limit of any $f(T)$ theory is identical to that of general relativity, so that these theories cannot be distinguished by measurements of the post-Newtonian parameters alone.
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Scalar-torsion theories of gravity. III. Analogue of scalar-tensor gravity and conformal invariants
Physical Review D, 2018Co-Authors: Manuel HohmannAbstract:We discuss a class of teleparallel scalar-torsion theories of gravity, which is parametrized by five Free Functions of the scalar field. The theories are formulated covariantly using a flat, but non-vanishing spin connection. We show how the actions of different theories within this class are related via conformal transformations of the tetrad and redefinitions of the scalar field, and derive the corresponding transformation laws for the Free Function in the action. From these we construct a number of quantities which are invariant under these transformations, and use them to write the action and field equations in different conformal frames. These results generalize a similar formalism for scalar-tensor theories of gravity, where the invariants have been used to express observables independently of the conformal frame.
Bernhard F Morrey - One of the best experts on this subject based on the ideXlab platform.
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primare totale ellenbogenprothese zur versorgung distaler humerusfrakturen primary total elbow replacement for fractures of the distal humerus
Operative Orthopadie Und Traumatologie, 2005Co-Authors: Srinath Kamineni, Pol Maria Rommens, Bernhard F MorreyAbstract:Objective Achieving stability and pain-Free Function for osteoporotic intraarticular multifragmentary fractures of the distal humerus in elderly patients by primary total elbow replacement (TER).
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Primäre totale Ellenbogenprothese zur Versorgung distaler Humerusfrakturen
Operative Orthopädie und Traumatologie, 2005Co-Authors: Lars Peter Müller, Pol Maria Rommens, Srinath Kamineni, Bernhard F MorreyAbstract:Operationsziel Erreichen einer stabilen und schmerzfreien Funktion durch primäre Implantation einer totalen Ellenbogenprothese bei komplexen intraartikulären distalen Humerusfrakturen älterer Patienten. Indikationen Fraktur mit freien Fragmenten oder schlechter Knochenqualität, die eine stabile Osteosynthese nicht zulassen. Geschlossene, komplexe intraartikuläre distale Humerusfraktur (Typ C nach der AO-Klassifikation). Typ-A- und B-Fraktur des distalen Humerus bei Patienten mit vorbestehenden degenerativen Veränderungen, rheumatoiden Erkrankungen oder Voroperationen des Gelenks. Gute Mitarbeit des Patienten, geringer Funktionsanspruch, Patientenalter > 65 Jahre. Kontraindikationen Offene Frakturen (Typ II oder III nach Gustilo-Anderson). Infizierte Wundverhältnisse, offene Weichteilverletzungen. Fehlende Mitarbeit des Patienten, hoher Funktionalitätsanspruch, Patientenalter > 65 Jahre. Paralyse des Bizepsmuskels. Operationstechnik Rückenlagerung des Patienten. Dorsaler Zugang zum Ellenbogengelenk. Darstellen der medialen Anteile des Musculus triceps an der Insertion des dorsalen Humerus und der Gelenkkapsel, Abdrängen in Kontinuität mit dem ulnaren Periost und der Unterarmfaszie. Bei Entfernung des frakturierten distalen Anteils des Humerus kann der Ansatz des Musculus triceps belassen werden. Vorbereitung des Humerusschafts: Bei mehrfach frakturierten Kondylen ist eine Rekonstruktion nicht notwendig; intramedulläres Entfernen des Knochens von der medialen und lateralen suprakondylären Kante mit einer Fräse. Entfernen der Olekranonspitze. Knochenspananlagerung hinter der anterioren Lasche der humeralen Komponente. Einzementieren der humeralen und ulnaren Komponente. Nachresektion des Radiuskopfes bzw. Processus coronoideus bei Impingement der Gelenkfacetten. Transossäre Reinsertion des Musculus triceps am Olekranon. Weiterbehandlung Selbständige Bewegungsübungen. Vermeidung des Hebens von Gewichten > 5 kg, keine wiederholten Dauerbelastungen > 1 kg Gewicht und keine forcierten Bewegungen im Ellenbogengelenk, z. B. Schlagsportarten. Ergebnisse 49 Totalendoprothesen wurden bei 48 Patienten (Durchschnittsalter 67 Jahre) aufgrund distaler Humerusfrakturen eingesetzt. 43 Frakturen konnten nach einem Zeitraum von 7 Jahren nachuntersucht werden. Nach der AO-Klassifikation wurden fünf Typ- A , fünf Typ-B und 33 Typ-C Frakturen behandelt. Der durchschnittliche Bewegungsumfang lag zwischen 24° und 131°. Der „Mayo Elbow Performance Score“ betrug durchschnittlich 93. Die Komplikationen aller 49 Patienten wurden anhand der Akten erfasst. 32-mal bestanden im Verlauf keine Komplikationen. Insgesamt mussten zehn Revisionseingriffe durchgeführt werden, fünfmal war im Verlauf eine Revisionsarthroplastie erforderlich. Retrospektiv kann die Totalendoprothese des Ellenbogens in der Versorgung distaler Humerustrümmerfrakturen unter strenger Berücksichtigung der genannten Indikationen empfohlen werden. Objective Achieving stability and pain-Free Function for osteoporotic intraarticular multifragmentary fractures of the distal humerus in elderly patients by primary total elbow replacement (TER). Indications Non-soft-tissue-attached fragments, poor-quality bone, where stable osteosynthesis is not attainable. Severely comminuted intraarticular closed type C fractures according to the AO classification with multiple small bone/cartilage fragments. In case of degenerative joint diseases and/or previous surgery in rheumatoid patients also type A and B fractures. High compliance, low demand, and old patient > 65 years. Contraindications Type II or III Gustilo-Anderson open fractures (primary irrigation and debridement). Preexisting infection, open wounds. Younger, high-demand or noncompliant patient. Paralysis of the biceps muscle. Surgical Technique Supine positioning of patient. Triceps-sparing dorsal approach. Elevation of medial aspect of the triceps from posterior aspect of the humerus and capsula, reflecting the triceps in continuity with the ulnar periosteum and the forearm fascia. If removal of distal part of the humerus, the triceps insertion can be left intact. Preparation of humerus: no reconstruction of multifractured condyles; excavate bone from medial and lateral supracondylar ridges with burr. Preparation of ulna: remove tip of olecranon. Cemented humeral and ulnar components. Bone graft interposition behind anterior flange of humeral component. Resection of radial head and coronoid process, if impingement after trial reduction. Triceps reattachment transosseous through olecranon. Postoperative Management No formal physical-therapy sessions. Avoid single-event weight lifting of > 5 kg and repetitive lifting of > 1 kg. Discourage playing racquets sports. Results 49 acute distal humeral fractures in 48 patients (average age: 67 years) were treated with TER. 43 fractures were followed at an average of 7 years. According to the AO classification, five fractures were type A, five type B, and 33 type C. The average flexion arc at follow-up was 24–131°, the Mayo Elbow Performance Score averaged 93. Data of complications were obtained from records in all 49 patients. 32 of the 49 elbows had neither a complication nor any further surgery from the time of the index arthroplasty to the most recent follow-up evaluation. Ten additional operative procedures, including five revision arthroplasties, were required. The retrospective review supports recommendation for TER for the treatment of an acute distal humeral fracture, when strict inclusion criteria are observed.
Cj Doré - One of the best experts on this subject based on the ideXlab platform.
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A randomised, multi-centre trial of total ankle replacement versus ankle arthrodesis in the treatment of patients with end stage ankle osteoarthritis (TARVA): statistical analysis plan
'Springer Science and Business Media LLC', 2019Co-Authors: Muller P, Ss Skene, Chowdhury K, Cro S, Aj Goldberg, Cj DoréAbstract:Background The total ankle replacement versus ankle arthrodesis (TARVA) trial aims to determine which surgical procedure confers the greatest improvement in pain-Free Function for patients with end-stage ankle osteoarthritis. Both procedures are effective but there has not yet been a direct comparison to establish which is superior. This article describes the statistical analysis plan for this trial as an update to the published protocol. It is written prior to the end of patient follow-up, while the outcome of the trial is still unknown. Design and methods TARVA is a randomised, un-blinded, parallel group trial of total ankle replacement versus ankle arthrodesis. The primary outcome is the Manchester-Oxford Foot Questionnaire walking/standing domain score at 52 weeks post-surgery. Secondary outcomes include measures of pain, social interaction, physical Function, quality of life, and range of motion. We describe in detail the statistical aspects of TARVA: the outcome measures, the sample size calculation, general analysis principles including treatment of missing data, the planned descriptive statistics and statistical models, and planned subgroup and sensitivity analyses. Discussion The TARVA statistical analysis will provide comprehensive and precise information on the relative effectiveness of the two treatments. The plan will be implemented in January 2020 when follow-up for the trial is completed
Tarva Study Group - One of the best experts on this subject based on the ideXlab platform.
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A randomised, multi-centre trial of total ankle replacement versus ankle arthrodesis in the treatment of patients with end stage ankle osteoarthritis (TARVA): statistical analysis plan.
'Springer Science and Business Media LLC', 2020Co-Authors: Muller Patrick, Skene, Simon S, Chowdhury Kashfia, Cro Suzie, Goldberg, Andrew J, Doré, Caroline J, Tarva Study GroupAbstract:BACKGROUND: The total ankle replacement versus ankle arthrodesis (TARVA) trial aims to determine which surgical procedure confers the greatest improvement in pain-Free Function for patients with end-stage ankle osteoarthritis. Both procedures are effective but there has not yet been a direct comparison to establish which is superior. This article describes the statistical analysis plan for this trial as an update to the published protocol. It is written prior to the end of patient follow-up, while the outcome of the trial is still unknown. DESIGN AND METHODS: TARVA is a randomised, un-blinded, parallel group trial of total ankle replacement versus ankle arthrodesis. The primary outcome is the Manchester-Oxford Foot Questionnaire walking/standing domain score at 52 weeks post-surgery. Secondary outcomes include measures of pain, social interaction, physical Function, quality of life, and range of motion. We describe in detail the statistical aspects of TARVA: the outcome measures, the sample size calculation, general analysis principles including treatment of missing data, the planned descriptive statistics and statistical models, and planned subgroup and sensitivity analyses. DISCUSSION: The TARVA statistical analysis will provide comprehensive and precise information on the relative effectiveness of the two treatments. The plan will be implemented in January 2020 when follow-up for the trial is completed. TRIAL REGISTRATION: ISRCTN registry number 60672307, ClinicalTrials.gov registration number NCT02128555. Registered 1 May 2014. Recruitment started in January 2015 and ended in January 2019
Nour El Houda Seloula - One of the best experts on this subject based on the ideXlab platform.
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Lp-theory for vector potentials and sobolev's inequalities for vector fields: Application to the stokes equations with pressure boundary conditions
Mathematical Models and Methods in Applied Sciences, 2013Co-Authors: Chérif Amrouche, Nour El Houda SeloulaAbstract:In a three-dimensional bounded possibly multiply connected domain, we give gradient and higher-order estimates of vector fields via div and curl in L p-theory. Then, we prove the existence and uniqueness of vector potentials, associated with a divergence-Free Function and satisfying some boundary conditions. We also present some results concerning scalar potentials and weak vector potentials. Furthermore, we consider the stationary Stokes equations with non-standard boundary conditions of the form u × n = g × n and π = π0 on the boundary Γ. We prove the existence and uniqueness of weak, strong and very weak solutions. Our proofs are based on obtaining Inf-Sup conditions that play a fundamental role. We give a variant of the Stokes system with these boundary conditions, in the case where the compatibility condition is not verified. Finally, we give two Helmholtz decompositions that consist of two kinds of boundary conditions such as uṡn and u × n on Γ. © 2013 World Scientific Publishing Company.
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LP -THEORY FOR VECTOR POTENTIALS AND SOBOLEV'S INEQUALITIES FOR VECTOR FIELDS. APPLICATION TO THE STOKES EQUATIONS WITH PRESSURE BOUNDARY CONDITIONS
2011Co-Authors: Chérif Amrouche, Nour El Houda SeloulaAbstract:In a three dimensional bounded possibly multiply-connected domain, we give gradient and higher order estimates of vector fields via div and curl in Lp theory. Then, we prove the existence and uniqueness of vector potentials, associated with a divergence-Free Function and satisfying some boundary conditions. We also present some results concerning scalar potentials and weak vector potentials. Furthermore, we consider the stationary Stokes equations with nonstandard boundary conditions of the form u × n = g × n and π = π0 on the boundary Γ. We prove the existence and uniqueness of weak, strong and very weak solutions. Our proofs are based on obtaining Inf − Sup conditions that play a fundamental role. We give a variant of the Stokes system with these boundary conditions, in the case where the compatibility condition is not verified. Finally, we give two Helmholtz decompositions that consist of two kinds of boundary conditions such as u * n and u × n on Γ.
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Lp-theory for vector potentials and Sobolev's inequalities for vector fields [Théorie Lp pour les potentiels vecteurs et inégalités de Sobolev pour des champs de vecteurs.]
Comptes Rendus Mathématique, 2011Co-Authors: Chérif Amrouche, Nour El Houda SeloulaAbstract:In a three-dimensional bounded possibly multiply-connected domain, we prove the existence and uniqueness of vector potentials in Lp-theory, associated with a divergence-Free Function and satisfying some boundary conditions. We also present some results concerning scalar potentials and weak vector potentials. Furthermore, various Sobolev-type inequalities are given. © 2011 Académie des sciences. Published by Elsevier Masson SAS.
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Lp-Theory for Vector Potentials and Sobolev's Inequalities for Vector Fields
Discrete and Continuous Dynamical Systems - Series S, 2010Co-Authors: Chérif Amrouche, Nour El Houda SeloulaAbstract:In a three dimensional bounded possibly multiply-connected domain, we prove the existence and uniqueness of vector potentials in Lp theory, associated with a divergence-Free Function and satisfying some boundary conditions. We also present some results concerning scalar potentials and weak vector potentials. Furthermore, variousSobolev-type inequalities are given.
