Periodontitis and diabetes are common, complex, chronic diseases with an established bidirectional relationship. That is, diabetes (particularly if glycaemic control is poor) is associated with an ...increased prevalence and severity of periodontitis, and, severe periodontitis is associated with compromised glycaemic control. Periodontal treatment (conventional non-surgical periodontal therapy) has been associated with improvements in glycaemic control in diabetic patients, with reductions in HbA1c of approximately 0.4% following periodontal therapy. For these reasons, management of periodontitis in people with diabetes is particularly important. The dental team therefore has an important role to play in the management of people with diabetes. An emerging role for dental professionals is envisaged, in which diabetes screening tools could be used to identify patients at high risk of diabetes, to enable them to seek further investigation and assessment from medical healthcare providers.
This paper uses a divergence-conforming B-spline fluid discretization to address the long-standing issue of poor mass conservation in immersed methods for computational fluid–structure interaction ...(FSI) that represent the influence of the structure as a forcing term in the fluid subproblem. We focus, in particular, on the immersogeometric method developed in our earlier work, analyze its convergence for linear model problems, then apply it to FSI analysis of heart valves, using divergence-conforming B-splines to discretize the fluid subproblem. Poor mass conservation can manifest as effective leakage of fluid through thin solid barriers. This leakage disrupts the qualitative behavior of FSI systems such as heart valves, which exist specifically to block flow. Divergence-conforming discretizations can enforce mass conservation exactly, avoiding this problem. To demonstrate the practical utility of immersogeometric FSI analysis with divergence-conforming B-splines, we use the methods described in this paper to construct and evaluate a computational model of an in vitro experiment that pumps water through an artificial valve.
•Div-conforming B-splines improve immersed fluid–structure interaction (FSI) analysis.•Strong mass conservation prevents spurious non-physical leakage through barriers.•Semi-implicit time integration is shown to converge a priori for a model problem.•Div-conforming immersogeometric FSI analysis is practical for heart valve analysis.•FSI simulations reproduce qualitative features of in vitro experiments.
Abstract
Medical advances of great importance in improving diagnosis, treatment or prevention of disease are often called ‘breakthroughs’. The processes by which breakthroughs are achieved are ...multiple, but may include necessity (a problem which must be solved), opportunity (the time must be right), chance (the unexpected), curiosity (a desire to understand mechanisms) and ingenuity (ability to find a solution). Discovery can be the start of a chain reaction, so that the breakthrough at the end of the chain becomes “inevitable”. Two examples are given in which these attributes played a part (i) the development of a vaccine against the poliomyelitis virus and (ii) the harnessing of penicillin as a therapeutic agent to treat serious bacterial infections.
In the 60 years since the invention of the laser, the scientific community has developed numerous fields of research based on these bright, coherent light sources, including the areas of imaging, ...spectroscopy, materials processing and communications. Ultrafast spectroscopy and imaging techniques are at the forefront of research into the light-matter interaction at the shortest times accessible to experiments, ranging from a few attoseconds to nanoseconds. Light pulses provide a crucial probe of the dynamical motion of charges, spins, and atoms on picosecond, femtosecond, and down to attosecond timescales, none of which are accessible even with the fastest electronic devices. Furthermore, strong light pulses can drive materials into unusual phases, with exotic properties. In this roadmap we describe the current state-of-the-art in experimental and theoretical studies of condensed matter using ultrafast probes. In each contribution, the authors also use their extensive knowledge to highlight challenges and predict future trends.
Isogeometric analysis of structural vibrations Cottrell, J.A.; Reali, A.; Bazilevs, Y. ...
Computer methods in applied mechanics and engineering,
08/2006, Letnik:
195, Številka:
41
Journal Article
Recenzirano
Odprti dostop
This paper begins with personal recollections of John H. Argyris. The geometrical spirit embodied in Argyris’s work is revived in the sequel in applying the newly developed concept of isogeometric ...analysis to structural vibration problems. After reviewing some fundamentals of isogeometric analysis, application is made to several structural models, including rods, thin beams, membranes, and thin plates. Rotationless beam and plate models are utilized as well as three-dimensional solid models. The concept of
k-refinement is explored and shown to produce more accurate and robust results than corresponding finite elements. Through the use of nonlinear parameterization, “optical” branches of frequency spectra are eliminated for
k-refined meshes. Optical branches have been identified as contributors to Gibbs phenomena in wave propagation problems and the cause of rapid degradation of higher modes in
p-method finite elements. A geometrically exact model of the NASA Aluminum Testbed Cylinder is constructed and frequencies and mode shapes are computed and shown to compare favorably with experimental results.
A long-standing enigma in plasma transport has been resolved by modeling of cold-pulse experiments conducted on the Alcator C-Mod tokamak. Controlled edge cooling of fusion plasmas triggers core ...electron heating on time scales faster than an energy confinement time, which has long been interpreted as strong evidence of nonlocal transport. This Letter shows that the steady-state profiles, the cold-pulse rise time, and disappearance at higher density as measured in these experiments are successfully captured by a recent local quasilinear turbulent transport model, demonstrating that the existence of nonlocal transport phenomena is not necessary for explaining the behavior and time scales of cold-pulse experiments in tokamak plasmas.
The decline in mesenchymal stem cell (MSC) self‐renewal and function with aging contributes to diseases associated with impaired osteogenesis. MSC donor age in prolonged culture also limits the ...therapeutic potential of these cells for tissue engineering and regenerative medicine. Here, we demonstrate an intervention to preserve the immature state MSC and consequently maintain self‐renewal and differentiation capacity during in vitro aging. We showed that blocking of phosphatidylinositol 3‐kinase/Akt/mammalian target of rapamycin (mTOR) prevents the development of an age‐related phenotype and maintains MSC morphology of early passage cells with high clonogenic frequency and enhanced proliferative capacity. MSC cultured in the presence of inhibitors of Akt or mTOR also robustly maintain their osteogenic potential, that is otherwise lost during in vitro aging. We further report that these effects may be mediated by induction of expression of pluripotency genes Nanog and Oct‐4 and by the reduction in the production of cytoplasmic reactive oxygen species (ROS). Additionally, loss of Akt/mTOR and ROS was accompanied with lower levels of DNA damage. These results provide an insight into mechanisms involved in MSC aging and suggest possible interventions to maintain quiescence and function of MSC prior to in vivo transplantation or as pharmacological agents in diseases associated with loss of MSC function. Stem Cells 2014;32:2256–2266
Historic Mortars Válek, Jan; Groot, Caspar J. W. P; Hughes, John J
2012, 20120519, 2015-03-18, Letnik:
7
eBook
This volume focuses on research and practical issues connected with mortars on historic structures. The book is divided into four sections: Characterisation of Historic Mortars, Repair Mortars and ...Design Issues, Experimental Research into Properties of Repair Mortars, and Assessment and Testing. The papers present the latest work of researchers in their field. The individual contributions were selected from the contributions to the 2nd Historic Mortars Conference, which took place in Prague, September, 22-24, 2010. All papers were reviewed and improved as necessary before publication. This peer review process by the editors resulted in the 34 individual contributions included in here. One extra paper reviewing and summarising State-of-the-Art knowledge covered by this publication was added as a starting and navigational point for the reader. The editors believe that having these papers in print is important and they hope that it will stimulate further research into historic mortars and related subjects.
Conventional finite shell element formulations use rotational degrees of freedom to describe the motion of the fiber in the Reissner–Mindlin shear deformable shell theory, resulting in an element ...with five or six degrees of freedom per node. These additional degrees of freedom are frequently the source of convergence difficulties in implicit structural analyses, and, unless the rotational inertias are scaled, control the time step size in explicit analyses. Structural formulations that are based on only the translational degrees of freedom are therefore attractive. Although rotation-free formulations using
C
0 basis functions are possible, they are complicated in comparison to their
C
1 counterparts. A
C
k
-continuous,
k
⩾
1, NURBS-based isogeometric shell for large deformations formulated without rotational degrees of freedom is presented here. The effect of different choices for defining the shell normal vector is demonstrated using a simple eigenvalue problem, and a simple lifting operator is shown to provide the most accurate solution. Higher order elements are commonly regarded as inefficient for large deformation analyses, but a traditional shell benchmark problem demonstrates the contrary for isogeometric analysis. The rapid convergence of the quadratic element is demonstrated for the NUMISHEET S-rail benchmark metal stamping problem.
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