检索结果-南通市图书馆

Lumbar interspinous pressure pain threshold values for healthy young men and women and the effect of prolonged fully flexed lumbar sitting posture:An observational study

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

World Journal of Orthopedics 2020年第3期11卷 158-166页

作者： Martin petersson Allan Abbott Department of physiotherapy Gripen Värmland Country CouncilKarlstad SE-65224Sweden Department of Medical and Health Sciences Division of PhysiotherapyFaculty of Health SciencesLinköping UniversityLinköping SE-58183Sweden

BACKGROUND Low back pain(LBp)is a common condition with large burden worldwide.Exposure to prolonged sitting with a flexed lumbar posture has been suggested in the literature to be a potential risk factor for self-reported LBp.No study has previously investigated whether exposure to prolonged flexed sitting posture provokes discomfort/pain and decreased interspinous pressure pain thresholds for healthy young men and women without back pain,despite this being a suggested risk factor for LBp.AIM To investigate whether sitting in a prolonged flexed lumbar posture provokes discomfort and lowers interspinous pressure pain thresholds in the lumbar spine for healthy young men and women without previous LBp.METHODS This is a an observational before and after study of 26 participants(13 men,13 women)between 20-35 years old.Algometry was used to examine the pain threshold for pressure applied between spinous processes of the lumbar spine L1-L5.pressure algometer measures were performed in prone before and after participants were instructed to sit in a fully flexed posture for a maximum of 15 min or until discomfort was experienced in the low back(Borg CR10=7/10).Wilcoxon signed-rank test was used for analyze values from the before and after test conditions.Mann-Whitney U test was used to investigate potential gender difference.RESULTS Fully flexed lumbar spine sitting posture up to 15 min provoked temporary discomfort but the proportion of participants experiencing discomfort 7/10 in the low back was 62%.For all pain pressure threshold locations tested,there was a significant difference for the study population with moderate-large decreased(r=-0.56)pressure pain threshold after exposure to prolonged flexed sitting posture(pparisons between gender did not show any significant difference.CONCLUSION The result showed that exposure to fully flexed lumbar sitting posture for up to 15 min produced temporary discomfort in the low back in young healthy adults with no previous history of LBp and significantly reduced lumb

关键词： Low back pain pain pressure threshold Algometer posture Spine pain mechanism

α-Synuclein arginylation in the human brain

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Translational Neurodegeneration 2022年第1期11卷 654-666页

作者： Jun Zhao Buyan pan Marie Fina Yun Huang Marie Shimogawa Kelvin C.Luk Elizabeth Rhoades EJames petersson Dawei W.Dong Anna Kashina Department of Biomedical Sciences University of Pennsylvania School of Veterinary MedicinePhiladelphiaPennsylvania 19104USA Department of Chemistry University of Pennsylvania School of Arts and SciencesPhiladelphiaPennsylvania 19104USA Center for Neurodegenerative Disease Research Department of Pathology and Laboratory MedicineUniversity of Pennsylvania Perelman School of MedicinePhiladelphiaPennsylvania 19104USA.

Background: Alpha-synuclein (α-syn) exhibits pathological misfolding in many human neurodegenerative disorders. We previously showed that α-syn is arginylated in the mouse brain and that lack of arginylation leads to neurodegen-eration in mice. Methods: Here, we tested α-syn arginylation in human brain pathology using newly derived antibodies in combina-tion with Western blotting, biochemical assays, and experiments in live neurons. Results: We found that α-syn was arginylated in the human brain on E46 and E83, two sites previously implicated in α-syn pathology and familial cases of parkinson’s disease. The levels of arginylation in different brain samples ranged between ~ 3% and ~ 50% of the total α-syn pool, and this arginylation nearly exclusively concentrated in the subcellu-lar α-syn fraction that sedimented at low centrifugation speeds and appeared to be simultaneously targeted by multi-ple posttranslational modifications. Arginylated α-syn was less susceptible to S129 phosphorylation and pathological aggregation in neurons. The arginylation level inversely correlated with the overall α-syn levels and with patient age, suggesting a possible causal relationship between arginylation decline and α-syn-dependent neuropathology. Conclusion: We propose that α-syn arginylation constitutes a potential neuroprotective mechanism that prevents its abnormal accumulation during neurodegeneration and aging in the human brain.

关键词： Arginylation Neurodegeneration Aging α-Synuclein

Extensive reworking of Archaean crust within the Birimian terrane in Ghana as revealed by combined zircon U-pb and Lu-Hf isotopes

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Geoscience Frontiers 2018年第1期9卷 173-189页

作者： Andreas petersson Anders Scherstén Axel Gerdes Department of Geology Lund UniversitySolvegatan 12SE-223 62 LundSweden Centre for Exploration Targeting School of Earth and EnvironmentUniversity of Western AustraliaCrawleyAustralia Department of Geosciences Swedish Museum of Natural History104 05 StockholmSweden Institut für Geowissenschaften Senckenberganlage 28D-60054 Frankfurt am MainGermany

Located in the southeastern parts of the BaouléMossi domain of the West African Craton,the Birimian terrane in Ghana is known to consist of predominantly juvenile crust emplaced during the Eburnean orogeny.Here we present novel coupled zircon U-pb and Lu-Hf isotope data from nine Birimian granitoids intruding different domains from northwestern,western and southeastern Ghana.Sub-chondriticε_(Hf)-values indicating reworking of Archaean crust are recorded in zircon from both northwestern and southeastern Ghana.As a conservative estimate 71%of all analysed zircon grains spanning in age from2220 Ma to 2130 Ma require contribution from a reworked Archaean source,contradicting the common belief that the Birimian terrane consist of predominantly juvenile crust.A minimumε_(Hf)-value of-10.5 at2139 Ma suggests a palaeoarchaean to late Mseoarchaean component as the contributing ancient source.Combined with previously reported heavy zirconδ^(18)O signatures from Birimian river zircon in Ghana,our new data suggests reworking of Archaean aged sediments during subduction initiated crustal growth in the vicinity of one,or possibly in between two Archaean aged cratons.

关键词： Birimian Baoulé Mossi Archaean Crustal growth Zircon

Stable and Efficient Modeling of Anelastic Attenuation in Seismic Wave propagation

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Communications in Computational physics 2012年第6期12卷 193-225页

作者： N.Anders petersson Bjorn Sjogreen Center for Applied Scientific Computing L-422Lawrence Livermore National LaboratoryP.O.Box 808LivermoreCA 94551USA

We develop a stable finite difference approximation of the three-dimensional viscoelastic wave equation.The material model is a super-imposition of N standard linear solid mechanisms,which commonly is used in seismology to model a material with constant quality factor Q.The proposed scheme discretizes the governing equations in second order displacement formulation using 3N memory variables,making it significantly more memory efficient than the commonly used first order velocitystress formulation.The new scheme is a generalization of our energy conserving finite difference scheme for the elastic wave equation in second order formulation[SIAM J.Numer.Anal.,45(2007),pp.1902–1936].Our main result is a proof that the proposed discretization is energy stable,even in the case of variable material properties.The proof relies on the summation-by-parts property of the discretization.The newscheme is implemented with grid refinement with hanging nodes on the interface.Numerical experiments verify the accuracy and stability of the new scheme.Semi-analytical solutions for a half-space problem and the LOH.3 layer over half-space problem are used to demonstrate how the number of viscoelastic mechanisms and the grid resolution influence the accuracy.We find that three standard linear solid mechanisms usually are sufficient to make the modeling error smaller than the discretization error.

关键词： Viscoelastic standard linear solid finite difference summation by parts

A Stable Finite Difference Method for the Elastic Wave Equation on Complex Geometries with Free Surfaces

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Communications in Computational physics 2009年第1期5卷 84-107页

作者： Daniel Appelo N.Anders petersson Department of Mechanical Engineering California Institute of TechnologyPasadenaCA 91125USA Center for Applied and Scientific Computing Lawrence Livermore National LaboratoryLivermoreCA 94551USA

A stable and explicit second order accurate finite difference method for the elastic wave equation in curvilinear coordinates is presented.The discretization of the spatial operators in the method is shown to be self-adjoint for free-surface,Dirichlet and periodic boundary conditions.The fully discrete version of the method conserves a discrete energy to machine precision.

关键词： Elastic wave equation curvilinear grids finite differences stability energy estimate seismic wave propagation

A Cartesian Embedded Boundary Method for Hyperbolic Conservation Laws

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Communications in Computational physics 2007年第6期2卷 1199-1219页

作者： Bjorn Sjogreen N.Anders petersson Center for Applied Scientific Computing Lawrence Livermore National LaboratoryLivermoreCA 94551USA.

We develop an embedded boundary finite difference technique for solving the compressible two-or three-dimensional Euler equations in complex geometries on a Cartesian grid.The method is second order accurate with an explicit time step determined by the grid size away from the boundary.Slope limiters are used on the embedded boundary to avoid non-physical oscillations near shock waves.We show computed examples of supersonic flow past a cylinder and compare with results computed on a body fitted grid.Furthermore,we discuss the implementation of the method for thin geometries,and show computed examples of transonic flow past an airfoil.

关键词： Embedded boundary hyperbolic conservation law finite difference scheme shock wave.

Stable Grid Refinement and Singular Source Discretization for Seismic Wave Simulations

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Communications in Computational physics 2010年第10期8卷 1074-1110页

作者： N.Anders petersson Bjorn Sjogreen Center for Applied Scientific Computing L-422Lawrence Livermore National LaboratoryPO Box 808LivermoreCA 94551.

An energy conserving discretization of the elastic wave equation in second order formulation is developed for a composite grid,consisting of a set of structured rectangular component grids with hanging nodes on the grid refinement interface.previously developed summation-by-parts properties are generalized to devise a stable second order accurate coupling of the solution across mesh refinement interfaces.The discretization of singular source terms of point force and point moment tensor type are also studied.Based on enforcing discrete moment conditions that mimic properties of the Dirac distribution and its gradient,previous single grid formulas are generalized to work in the vicinity of grid refinement interfaces.These source discretization formulas are shown to give second order accuracy in the solution,with the error being essentially independent of the distance between the source and the grid refinement boundary.Several numerical examples are given to illustrate the properties of the proposed method.

关键词： Elastic wave equation mesh refinement stability summation by parts singular source term

An Energy Absorbing Far-Field Boundary Condition for the Elastic Wave Equation

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Communications in Computational physics 2009年第8期6卷 483-508页

作者： N.Anders petersson Bjorn Sjogreen Center for Applied and Scientific Computing L-550 Lawrence Livermore National LaboratoryLivermoreCA 94551USA

We present an energy absorbing non-reflecting boundary condition of Clayton-Engquist type for the elastic wave equation together with a discretization which is stable for any ratio of compressional to shear wave speed.We prove stability for a second-order accurate finite-difference discretization of the elastic wave equation in three space dimensions together with a discretization of the proposed non-reflecting boundary condition.The stability proof is based on a discrete energy estimate and is valid for heterogeneous materials.The proof includes all six boundaries of the computational domain where special discretizations are needed at the edges and corners.The stability proof holds also when a free surface boundary condition is imposed on some sides of the computational domain.

关键词： Elastic wave equation far-field boundary condition finite differences stability energy estimate

Muco-submucosal elongated polyps of the gastrointestinal tract:A case series and a review of the literature

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2013年第11期19卷 1845-1849页

作者： Char Loo Tan Sze Hwa Tan Jimmy BY So Fredrik petersson Department of pathology National University Hospital SystemSingapore 119074Singapore Department of Surgery National University Hospital SystemSingapore 119074Singapore

We present three cases of gastrointestinal muco-submucosal elongated polyps,two located in the duodenum and one in the descending colon.All three cases had a characteristic,"worm-like" endoscopic appearance and were lined by unremarkable mucosa.The vascular component was located in the submucosa and was composed of a mixture of variably dilated blood vessels(capillaries and veins) and lymphatics.The duodenal polyps displayed lipomatous metaplasia of the submucosal stroma.The dual vascular phenotype of the vascular component was confirmed by immunohistochemistry with D2-40 and CD31.

关键词： Muco-submucosal elongated polyp Vascular malformation Endoscopic ultrasonography Angioma Endoscopy