87 research outputs found
Maximum Angle of Stability of a Wet Granular Pile
Anyone who has built a sandcastle recognizes that the addition of liquid to
granular materials increases their stability. However, measurements of this
increased stability often conflict with theory and with each other [1-7]. A
friction-based Mohr-Coulomb model has been developed [3,8]. However, it
distinguishes between granular friction and inter-particle friction, and uses
the former without providing a physical mechanism. Albert, {\em et al.} [2]
analyzed the geometric stability of grains on a pile's surface. The
frictionless model for dry particles is in excellent agreement with experiment.
But, their model for wet grains overestimates stability and predicts no
dependence on system size. Using the frictionless model and performing
stability analysis within the pile, we reproduce the dependence of the
stability angle on system size, particle size, and surface tension observed in
our experiments. Additionally, we account for past discrepancies in
experimental reports by showing that sidewalls can significantly increase the
stability of granular material.Comment: 4 pages, 4 figure
Wet Granular Materials
Most studies on granular physics have focused on dry granular media, with no
liquids between the grains. However, in geology and many real world
applications (e.g., food processing, pharmaceuticals, ceramics, civil
engineering, constructions, and many industrial applications), liquid is
present between the grains. This produces inter-grain cohesion and drastically
modifies the mechanical properties of the granular media (e.g., the surface
angle can be larger than 90 degrees). Here we present a review of the
mechanical properties of wet granular media, with particular emphasis on the
effect of cohesion. We also list several open problems that might motivate
future studies in this exciting but mostly unexplored field.Comment: review article, accepted for publication in Advances in Physics;
tex-style change
Insights into the pathogenesis of vein graft disease: lessons from intravascular ultrasound
The success of coronary artery bypass grafting (CABG) is limited by poor long-term graft patency. Saphenous vein is used in the vast majority of CABG operations, although 15% are occluded at one year with as many as 50% occluded at 10 years due to progressive graft atherosclerosis. Intravascular ultrasound (IVUS) has greatly increased our understanding of this process. IVUS studies have shown that early wall thickening and adaptive remodeling of vein grafts occurs within the first few weeks post implantation, with these changes stabilising in angiographically normal vein grafts after six months. Early changes predispose to later atherosclerosis with occlusive plaque detectable in vein grafts within the first year. Both expansive and constrictive remodelling is present in diseased vein grafts, where the latter contributes significantly to occlusive disease. These findings correlate closely with experimental and clinicopathological studies and help define the windows for prevention, intervention or plaque stabilisation strategies. IVUS is also the natural tool for evaluating the effectiveness of pharmacological and other treatments that may prevent or slow the progression of vein graft disease in clinical trials
Prospects for the development of probiotics and prebiotics for oral applications
There has been a paradigm shift towards an ecological and microbial community-based approach to understanding oral diseases. This has significant implications for approaches to therapy and has raised the possibility of developing novel strategies through manipulation of the resident oral microbiota and modulation of host immune responses. The increased popularity of using probiotic bacteria and/or prebiotic supplements to improve gastrointestinal health has prompted interest in the utility of this approach for oral applications. Evidence now suggests that probiotics may function not only by direct inhibition of, or enhanced competition with, pathogenic micro-organisms, but also by more subtle mechanisms including modulation of the mucosal immune system. Similarly, prebiotics could promote the growth of beneficial micro-organisms that comprise part of the resident microbiota. The evidence for the use of pro or prebiotics for the prevention of caries or periodontal diseases is reviewed, and issues that could arise from their use, as well as questions that still need to be answered, are raised. A complete understanding of the broad ecological changes induced in the mouth by probiotics or prebiotics will be essential to assess their long-term consequences for oral health and disease
Endothelium-derived nitric oxide limits sympathetic neurogenic constriction in intestinal microcirculation
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