We have studied the thermal conductance of tilt grain boundaries in graphene using nonequilibrium molecular dynamics simulations. When a constant heat flux is allowed to flow, we observe sharp jumps in temperature at the boundaries, characteristic of interfaces between materials of differing thermal properties. On the basis of the magnitude of these jumps, we have computed the boundary conductance of twin grain boundaries as a function of their misorientation angles. We find the boundary conductance to be in the range 1.5 × 10(10) to 4.5 × 10(10) W/(m(2) K), which is significantly higher than that of any other thermoelectric interfaces reported in the literature. Using the computed values of boundary conductances, we have identified a critical grain size of 0.1 μm below which the contribution of the tilt boundaries to the conductivity becomes comparable to that of the contribution from the grains themselves. Experiments to test the predictions of our simulations are proposed.
The addition of a single sheet of carbon atoms in the form of graphene can drastically alter friction between a nanoscale probe tip and a surface. Here, for the first time we show that friction can be altered over a wide range by fluorination. Specifically, the friction force between silicon atomic force microscopy tips and monolayer fluorinated graphene can range from 5-9 times higher than for graphene. While consistent with previous reports, the combined interpretation from our experiments and molecular dynamics simulations allows us to propose a novel mechanism: that the dramatic friction enhancement results from increased corrugation of the interfacial potential due to the strong local charge concentrated at fluorine sites, consistent with the Prandtl-Tomlinson model. The monotonic increase of friction with fluorination in experiments also demonstrates that friction force measurements provide a sensitive local probe of the degree of fluorination. Additionally, we found a transition from ordered to disordered atomic stick-slip upon fluorination, suggesting that fluorination proceeds in a spatially random manner.
Blood lactate measurement can be used as a reliable tool for monitoring adequate tissue perfusion during extracorporeal life support and was strongly predictive of mortality. Therefore, in patients without adequate decrement in lactate levels during extracorporeal life support, potential factors responsible for inadequate perfusion should be identified and corrected.
PurposeThiazolidinediones are insulin-sensitizing agents that reduce neointimal proliferation and the adverse clinical outcomes associated with percutaneous coronary intervention (PCI) in patients with diabetes mellitus (DM). There is little data on whether or not low dose pioglitazone reduces adverse clinical outcomes.Materials and MethodsThe study population included 121 DM patients with coronary artery disease and they were randomly assigned to 60 patients taking 15 mg of pioglitazone daily in addition to their diabetic medications and 61 patients with placebo after the index procedure with drug-eluting stents (DESs). The primary end points were rate of in-stent restenosis (ISR) and change in atheroma volume and in-stent neointimal volume. The secondary end points were all-cause death, myocardial infarction (MI), stent thrombosis and re-PCI.ResultsThere were no statistical differences in the clinical outcomes and the rate of ISR between the two groups [all-cause death; n=0 (0%) in the pioglitazone group vs. n=1 (1.6%) in the control group, p=0.504, MI; n=2 (3.3%) vs. n=1 (1.6%), p=0.465, re-PCI; n=6 (10.0%) vs. n=6 (9.8%), p=0.652, ISR; n=4 (9.3%) vs. n=4 (7.5%), p=1.000, respectively].
There were no differences in changes in neointimal volume, percent neointimal volume, total plaque volume and percent plaque volume between the two groups on intravascular ultrasonography (IVUS) study.ConclusionOur study demonstrated that low dose pioglitazone does not reduce rate of ISR, neointimal volume nor atheroma volume in DM patients who have undergone PCI with DESs, despite the limitations of the study.
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