1,556 research outputs found
A cadaveric model to evaluate the effect of unloading the medial quadriceps on patellar tracking and patellofemoral joint pressure and stability
Background Vastus Medialis Muscles (VMM) damage has been widely identified following patellar dislocation. Rehabilitation programmes have been suggested to strengthen the VMM and reduce clinical symptoms of pain and instability. This controlled laboratory study investigated the hypothesis that reduced Vastus Medialis Obliquus (VMO) and Vastus Medialis Longus (VML) muscle tension would alter patellar tracking, stability and PFJ contact pressures. Methods Nine fresh-frozen dissected cadaveric knees were mounted in a rig with the quadriceps and iliotibial band loaded to 205 N. An optical tracking system measured joint kinematics and pressure sensitive film between the patella and trochlea measured PFJ contact pressures. Measurements were repeated for three conditions: 1. With all quadriceps heads and iliotibial band (ITB) loaded; 2. as 1, but with the VMO muscle unloaded and 3. as 1, but with the VMO and VML unloaded. Measurements were also repeated for the three conditions with a 10 N lateral displacement force applied to the patella. Results Reduction of VMM tension resulted in significant increases in lateral patellar tilt (2.8°) and translation (4 mm), with elevated lateral and reduced medial joint contact pressures from 0.48 to 0.14 MPa, and reduced patellar stability (all p < 0.05). Conclusions These findings provide basic scientific rationale to support the role of quadriceps strengthening to resist patellar lateral maltracking and rebalance the articular contact pressure away from the lateral facet in patients with normal patellofemoral joint anatomy
A Linear Programming Approach to Weak Reversibility and Linear Conjugacy of Chemical Reaction Networks
15 páginas, 2 figuras.-- The final publication is
available at www.springerlink.comA numerically effective procedure for determining weakly reversible
chemical reaction networks that are linearly conjugate to a known reaction network is
proposed in this paper. The method is based on translating the structural and algebraic
characteristics of weak reversibility to logical statements and solving the obtained
set of linear (in)equalities in the framework of mixed integer linear programming.
The unknowns in the problem are the reaction rate coefficients and the parameters of
the linear conjugacy transformation. The efficacy of the approach is shown through
numerical examples.Matthew D. Johnston and David Siegel acknowledge the support of D. Siegel’s Natural
Sciences and Engineering Research Council of Canada Discovery Grant. Gà bor Szederkényi acknowledges
the support of the Hungarian National Research Fund through grant no. OTKA K-83440 as well as
the support of project CAFE (Computer Aided Process for Food Engineering) FP7-KBBE-2007-1 (Grant
no: 212754).Peer reviewe
Sparticle Spectrum Constraints
The supersymmetric standard model with supergravity-inspired soft breaking
terms predicts a rich pectrum of sparticles to be discovered at the SSC, LHC
and NLC. Because there are more supersymmetric particles than unknown
parameters, one can write down sum rules relating their masses. We discuss the
pectrum of sparticles from this point of view. Some of the sum rules do not
depend on the input parameters and can be used to test the consistency of the
model, while others are useful in determining the input parameters of the
theory. If supersymmetry is discovered but the sum rules turn out to be
violated, it will be evidence of new physics beyond the minimal supersymmetric
standard model with universal soft supersymmetry-breaking terms.Comment: 25 pages. NUB-3067-93TH, UFIFT-HEP-93-16, SSCL-Preprint-439, June
199
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NRP2 as an Emerging Angiogenic Player; Promoting Endothelial Cell Adhesion and Migration by Regulating Recycling of α5 Integrin.
Angiogenesis relies on the ability of endothelial cells (ECs) to migrate over the extracellular matrix via integrin receptors to respond to an angiogenic stimulus. Of the two neuropilin (NRP) orthologs to be identified, both have been reported to be expressed on normal blood and lymphatic ECs, and to play roles in the formation of blood and lymphatic vascular networks during angiogenesis. Whilst the role of NRP1 and its interactions with integrins during angiogenesis has been widely studied, the role of NRP2 in ECs is poorly understood. Here we demonstrate that NRP2 promotes Rac-1 mediated EC adhesion and migration over fibronectin (FN) matrices in a mechanistically distinct fashion to NRP1, showing no dependence on β3 integrin (ITGB3) expression, or VEGF stimulation. Furthermore, we highlight evidence of a regulatory crosstalk between NRP2 and α5 integrin (ITGA5) in ECs, with NRP2 depletion eliciting an upregulation of ITGA5 expression and disruptions in ITGA5 cellular organization. Finally, we propose a mechanism whereby NRP2 promotes ITGA5 recycling in ECs; NRP2 depleted ECs were found to exhibit reduced levels of total ITGA5 subunit recycling compared to wild-type (WT) ECs. Our findings expose NRP2 as a novel angiogenic player by promoting ITGA5-mediated EC adhesion and migration on FN
Hybrid MM/SVM structural sensors for stochastic sequential data
In this paper we present preliminary results stemming from a novel application of Markov Models and Support Vector Machines to splice site classification of Intron-Exon and Exon-Intron (5' and 3') splice sites. We present the use of Markov based statistical methods, in a log likelihood discriminator framework, to create a non-summed, fixed-length, feature vector for SVM-based classification. We also explore the use of Shannon-entropy based analysis for automated identification of minimal-size models (where smaller models have known information loss according to the specified Shannon entropy representation). We evaluate a variety of kernels and kernel parameters in the classification effort. We present results of the algorithms for splice-site datasets consisting of sequences from a variety of species for comparison
Approximate probabilistic verification of hybrid systems
Hybrid systems whose mode dynamics are governed by non-linear ordinary
differential equations (ODEs) are often a natural model for biological
processes. However such models are difficult to analyze. To address this, we
develop a probabilistic analysis method by approximating the mode transitions
as stochastic events. We assume that the probability of making a mode
transition is proportional to the measure of the set of pairs of time points
and value states at which the mode transition is enabled. To ensure a sound
mathematical basis, we impose a natural continuity property on the non-linear
ODEs. We also assume that the states of the system are observed at discrete
time points but that the mode transitions may take place at any time between
two successive discrete time points. This leads to a discrete time Markov chain
as a probabilistic approximation of the hybrid system. We then show that for
BLTL (bounded linear time temporal logic) specifications the hybrid system
meets a specification iff its Markov chain approximation meets the same
specification with probability . Based on this, we formulate a sequential
hypothesis testing procedure for verifying -approximately- that the Markov
chain meets a BLTL specification with high probability. Our case studies on
cardiac cell dynamics and the circadian rhythm indicate that our scheme can be
applied in a number of realistic settings
Prenatal Vitamin D Supplementation and Child Respiratory Health: A Randomised Controlled Trial
PMCID: PMC3691177This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Starobinsky-like inflation in no-scale supergravity Wess-Zumino model with Polonyi term
We propose a simple modification of the no-scale supergravity Wess-Zumino
model of Starobinsky-like inflation to include a Polonyi term in the
superpotential. The purpose of this term is to provide an explicit mechanism
for supersymmetry breaking at the end of inflation. We show how successful
inflation can be achieved for a gravitino mass satisfying the strict upper
bound TeV, with favoured values
TeV. The model suggests that SUSY may be discovered in collider physics
experiments such as the LHC or the FCC.Comment: 13 pages, 4 figure
Acute Fulminant Colitis Caused by Idiopathic Mesenteric Inflammatory Veno-Occlusive Disease
Mesenteric inflammatory veno-occlusive disease (MIVOD) is an uncommon but important cause of bowel inflammation. MIVOD is characterised by lymphocytic inflammation and non-thrombotic occlusion of the mesenteric venules and veins. We present the case of a young man who presented with acute fulminant colitis, requiring colectomy. The differential diagnosis, pathogenesis and treatment are discussed. This case illustrates the rapid progression from ‘well’ to ‘colectomy’ that can occur with MIVOD. MIVOD should be considered in the differential diagnosis of colitis that does not respond to conventional medical treatment
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