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Why are muscles strong, and why do they require little energy in eccentric action?

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Journal of Sport and Health Science 2018年第3期7卷 255-264页

作者： walter Herzog Human Performance Laboratory Faculty of Kinesiology University of Calgary

It is well acknowledged that muscles that are elongated while activated(i.e.,eccentric muscle action)are stronger and require less energy(per unit of force)than muscles that are shortening(i.e.,concentric contraction)or that remain at a constant length(i.e.,isometric contraction).Although the cross-bridge theory of muscle contraction provides a good explanation for the increase in force in active muscle lengthening,it does not explain the residual increase in force following active lengthening(residual force enhancement),or except with additional assumptions,the reduced metabolic requirement of muscle during and following active *** from the cross-bridge theory,2 other primary explanations for the mechanical properties of actively stretched muscles have emerged:(1)the so-called sarcomere length nonuniformity theory and(2)the engagement of a passive structural element *** this article,these theories are discussed,and it is shown that the last of these—the engagement of a passive structural element in eccentric muscle action—offers a simple and complete explanation for many hitherto unexplained observations in actively lengthening *** by no means fully proven,the theory has great appeal for its simplicity and beauty,and even if over time it is shown to be wrong,it nevertheless forms a useful framework for direct hypothesis testing.

关键词： Cross-bridge theory Eccentric Force-length relationship Residual force enhancement Titin

Chemically derived graphene quantum dots for high-strain sensing

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Journal of Materials Science & Technology 2023年第10期141卷 110-115页

作者： Shujun Wang Francesco Lenzini Dechao Chen Philip Tanner Jisheng Han David thiel Mirko Lobino Qin Li Queensland Miro-and Nanotechnology Centre Griffith UniversityNathan CampusBrisbane QLD 4111Australia School of Engineering and Built Environment Griffith UniversityNathan CampusBrisbane QLD 4111Australia Centre for Quantum Dynamics Griffith UniversityNathan CampusBrisbane QLD 4111Australia Department of Industrial Engineering University of Trento38122Italy

Graphene quantum dots(GQDs)refer to graphene fragments with a lateral dimension typically less than 100 nm,which possess unique electrical and optical properties due to the quantum confinement *** this study,we demonstrate that chemically derived graphene quantum dots show great potential for making highly stretchable and cost-effective strain sensors via an electron tunneling ***-able strain sensors are critical devices for the field of flexible or wearable electronics which are expected to maintain function up to high strain values(>30%).However,strain sensors based on conventional materials(*** or semiconductors)or metal nanoparticles(*** or silver nanoparticles)only work within a small range of strain(*** former have a working range<1%and the latter<3%).In this study,by simply dropcasting solution-processed GQDs between the interdigitated electrodes on polydimethylsiloxane,we obtained devices that can function in the range from 0.06%to over 50%ten-sile strain with both the sensitivity and working range conveniently adjustable by the concentration of GQDs *** study provides a new concept for practical applications of GQDs,revealing the poten-tial of this material for smart applications such as artificial skin,human-machine interfaces,and health monitoring.

关键词： Graphene quantum dots Graphene Strain Sensor Electron tunneling

Mobile GIS occupancy audit of Ulana informal settlement in Ekurhuleni municipality, South Africa

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Geo-Spatial Information Science 2018年第4期21卷 322-330页

作者： Baleseng Tlholohelo Mokoena walter Musakwa Department of Town and Regional Planning University of JohannesburgDoornfonteinSouth Africa

Relocating people in informal settlements and upgrading the lives of those people requireconsistent commitment, good strategies, and supporting systems. In South Africa, in order toallocate subsidized housing to beneficiaries of an informal settlement, beneficiary administration needs to determine the number of people who qualify for subsidized houses. Withoutgeo-spatial data-based technical verification, conventional methods of occupancy audits areoften cumbersome, are unreliable, and do not promote smart and evidence-based decisionmaking. Accordingly, the aim of this study is to propose and develop an Oracle-based mobileGIS tool to conduct an occupancy audit for Ulana, an informal settlement in EkurhuleniMunicipality in South Africa. Android-based tablets were used to collect the geographicand socio-economic attributes of the informal dwelling units (DU). Spatial analysis (inArcGIS software and geo-spatial modeling environment) and statistical analysis were conducted to produce the occupancy audit. The results indicated that the use of mobile GISprovides up-to-date, accurate, comprehensive, and real-time data so as to facilitate thedevelopment of smart and integrated human settlements. The results of this audit alsoindicated that only 57% of the households residing in Ulana could potentially benefit fromreceiving a subsidized house. Accordingly, the occupancy audit enables planners to planappropriate upgrading and housing development strategies for informal settlement. Thisstudy demonstrates that successful planning of housing delivery for post independentintegrated neighborhoods is not a mere political rhetoric but is viable when it is based onreasonable geo-spatial techniques and information. The use of mobile GIS therefore needs tobe extended to other informal settlement upgrading projects in South Africa as well as othercities in the global south. However, proper professional training is required to ensure thesuccessful usage of smart mobile GIS tools.

关键词： Mobile GIS geo-spatial occupancy audit informal settlements integration smart cities

Cirrhotic ascites review: Pathophysiology, diagnosis and management

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World Journal of Hepatology 2013年第5期5卷 251-263页

作者： Christopher M Moore David H Van thiel Section of Hepatology Department of MedicineRush University Medical CenterChicagoIL 60612United States

Ascites is a pathologic accumulation of peritoneal fluidcommonly observed in decompensated cirrhotic states. Its causes are multi-factorial, but principally involve significant volume and hormonal dysregulation in the setting of portal hypertension. The diagnosis of ascites is considered in cirrhotic patients given a constellation of clinical and laboratory findings, and ultimately confirmed, with insight into etiology, by imaging and paracentesis procedures. Treatment for ascites is multimodal including dietary sodium restriction, pharmacologic therapies, diagnostic and therapeutic paracentesis, and in certain cases transjugular intra-hepatic portosystemic shunt. Ascites is associated with numerous complications including spontaneous bacterial peritonitis, hepato-hydrothorax and hepatorenal syndrome. Given the complex nature of ascites and associatedcomplications, it is not surprising that it heralds increased morbidity and mortality in cirrhotic patients and increased cost-utilization upon the health-care system. This review will detail the pathophysiology of cirrhotic ascites, common complications derived from it, and pertinent treatment modalities.

关键词： Ascites Cirrhosis Hepato-hydrothorax Hepatorenal syndrome Spontaneous bacterial peritonitis

Clinical features and epidemiology of spondyloarthritides associated with inflammatory bowel disease

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World Journal of Gastroenterology 2009年第20期15卷 2449-2455页

作者： Carlo Salvarani walter Fries Rheumatology Unit Department of Interna Medicine Department of Internal Medicine and MedicaTherapy University of Messina

Inflammation of axial and/or peripheral joints is one of the most frequent extra-intestinal manifestations complicating the clinical course and therapeutic approach in inflammatory bowel diseases(IBD).The frequency of these complications seems to be similar for both diseases, Crohn's disease and ulcerative *** associated with IBD belongs to the category of *** involvement ranges from isolated inflammatory back pain to ankylosing spondylitis, whereas peripheral arthritis is noted in pauciarticular and in polyarticular *** radiological involvement of the sacroiliac joints is reported to occur in up to 50% of *** musculoskeletal manifestations such as buttock pain, dactylitis, calcaneal enthesitis, and thoracic pain are frequently underdiagnosed and, consequently, are not treated *** diagnostic approaches and criteria have been proposed over the past 40 years in an attempt to correctly classify and diagnose such *** correct recognition of spondylarthropathies needs an integrated multidisciplinary approach in order to identify common therapeutic strategies, especially in the era of the new biologic therapies.

关键词： Crohn disease Ankylosing spondylitis Ulcerative colitis Spondylarthropathies Arthritis Enthesopathy

Improved State-Based Peridynamic Lattice Model Including Elasticity, Plasticity and Damage

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Computer Modeling in Engineering & Sciences 2018年第9期116卷 323-347页

作者： Siavash Nikravesh walter Gerstle Department of Civil Construction and Environmental EngineeringUniversity of New MexicoAlbuquerqueNMUSA

In this study,a recently developed peridynamic lattice model called the“Statebased Peridynamic Lattice Model”(SPLM)is improved and *** the SPLM,rather than as a continuum,solids are simulated using a close-packed lattice of peridynamically interacting *** new SPLM approach advances the SPLM model by improving the damage and plasticity ***,plasticity and damage are coupled in this approach.A robust method for damage initiation is developed.A new damage model called the“two-spring damage model”allows damage to localize to a single lattice particle,thus allowing highly localized damage(cracks)to emerge in a realistic manner.A plasticity model that includes hardening,softening,and damage due to plasticity is proposed and *** boundary effects are modeled efficiently and *** improved SPLM method is then employed to simulate three common concrete laboratory tests:uniaxial tension,uniaxial compression,and the Brazilian split cylinder *** SPLM results are then compared with results from the earlier SPLM model,with simplified classical predictions,and with laboratory *** solving the same benchmark problems using various lattice rotations and lattice spacings,the approach is demonstrated to be sufficiently objective to be a useful engineering tool to predict the essentially random behavior of concrete laboratory *** improved SPLM demonstrates significant improvements over the previously published version and is found to simulate concrete structures accurately and efficiently using far less computational effort than comparable computational simulation methods.

关键词： Peridynamics SPLM lattice damage plasticity fracture concrete

Indentation Size Effect inβCuAlBe and Cu-2Be Alloys

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Acta Metallurgica Sinica(English Letters) 2021年第12期34卷 1669-1678页

作者： Susana Montecinos Sebastian Tognana walter Salgueiro IFIMAT Facultad de Ciencias ExactasUniversidad Nacional del Centro de La Provincia de Buenos AiresPinto 3997000 TandilArgentina Consejo Nacional de Investigaciones Científicas y Técnicas CONICET Av.Rivadavia 1917C1033AAJ Buenos AiresArgentina CIFICEN(UNCPBA-CICPBA-CONICET) Pinto 3997000 TandilArgentina Comisión de Investigaciones Científicas de la Provincia de Bs.As Calle 526 entre 10 y 111900 La PlataArgentina

The indentation size effect(ISE)was studied by instrumented nanoindentation and Vickers hardness measurements on polycrystalline copper,βCuAlBe pseudoelastic and age-hardenable CuBe *** in the load-depth curves at different loads would suggest a change in the behavior of the materials as the load *** was estimated at different loads taking into account the pile-up in each case,which was estimated from the images of the topography obtained by atomic force microscopy(AFM).The effect of the microstructure of Cu-2Be(wt%)samples on the ISE was also *** each copper alloy,the Nix and Gao model was applied to the hardness-depth curves,and significant differences were found for the parameters *** is in the constant nanohardness regime for depths below 500 nm,while microhardness exhibits the ISE *** behavior of the nanohardness and the plastic strain with the depth is almost *** presents the lowest values of plastic strains due to the pseudoelastic effect,while Cu presents an almost constant value around 8%,which corresponds to the highest plastic strain obtained.

关键词： Hardness Pseudoelasticity Copper alloys Plasticity Indentation size effect

Normal families and fixed points of iterates

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Science China Mathematics 2010年第3期53卷 593-596页

作者： BERGWEILER walter Mathematisches Seminar der Christian–Albrechts–Universitt zu Kiel

Let F be a family of holomorphic functions and suppose that there exists ε > 0 such that if f ∈ F, then |(f 2 ) (ξ)|≤4-ε for all fixed points ξ of the second iterate f 2 . We show that then F is normal. This is deduced from a result which says that if p is a polynomial of degree at least 2, then p 2 has a fixed point ξ such that |(p 2 ) (ξ)|≥4. The results are motivated by a problem posed by Yang Lo.

关键词： fixed point multiplier normality iteration periodic point

Inflammatory bowel disease-associated spondyloarthropathies

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World Journal of Gastroenterology 2009年第20期15卷 2441-2442页

作者： walter Fries Department of Internal Medicine and MedicaTherapy University of Messina

This issue presents a symposium held in Messina talking about inflammatory bowel disease(IBD) and associated *** topic covers epidemiology and clinical manifestations of IBD-related arthropathies, common genetic and immunologic features, combined therapies for gut and joint inflammation, and future biologic therapies etc.I believe this series of articles will deeply facilitate understanding of and the approach to IBD and associated arthropathies.

关键词： Inflammatory bowel disease Spondylo-arthropathies Anti-tumor necrosis factor α