Kinetic Monte Carlo method for simulating reactions in solutions

We present an off-lattice kinetic Monte Carlo method, which is useful to simulate reactions in solutions. We derive the method from first-principles. We assume that diffusion leads to a Gaussian distribution for the position of the particles. This allows us to deal with the diffusion analytically, and we only need to simulate the reactive processes. The rate constants of these reactions can be computed before a simulation is started, and need not be computed on-the-fly as in other off-lattice kinetic Monte Carlo methods. We show how solvent molecules can be removed from the simulations, which minimizes the number of particles that have to be simulated explicitly. We present the relation with the customary macroscopic rate equations, and compare the results of these equations and our method on a variation of the Lotka model

Strength Prediction Model of a Particle-Reinforced Shellproof Ceramic Composite

On the basis of the microstructure of particle-reinforced shellproof ceramic composite, and the intergranular fracture feature, a dislocation pile-up fracture model of the small-particle ceramic composite is developed, the mechanism of formation, growth and coalescence of microcracks. The complex effect of the small particle pull-out and large particle cracking is concerned, when constructing the crack extension fracture model. Thereafter, the influence of particles’ volume fraction and matrix grain diameter on fracture strength is studied. The experimental data shows that the proposed strength prediction model is successful and can be generally applied.На основе микроструктуры пуленепробиваемого керамического композиционного материала, упрочненного мелкими частицами, и характера его внутрикристаллического разрушения разработана модель разрушения при скоплении дислокаций, т.е. исследован механизм образования, роста и слияния трещин. При разработке модели разрушения при распространении трещины учитывали совместное влияние процессов выкрашивания мелких частиц и растрескивания крупных частиц. Изучено влияние относительного объема частиц и диаметра матричного зерна на сопротивление разрушению. Экспериментальные результаты показали, что данная модель прогнозирования прочности является эффективной и общеприменимой.На основі мікроструктури куленепробивного керамічного композиційного матеріалу, зміцненого дрібними частинками, і характеру внутрішньокристалічного руйнування розроблено модель руйнування при скупченні дислокацій, тобто досліджено механізм виникнення, росту і злиття тріщин. При розробці моделі руйнування при розповсюдженні тріщини враховували спільний вплив процесів викришування дрібних частинок і розтріскування великих. Вивчено вплив відносного об’єму частинок і діаметра матричного зерна на опір руйнуванню. Експериментальні дані показали, що запропонована модель прогнозування міцності є ефективною і загальновживаною

Some effects of different constitutive laws on simulating mitral valve dynamics with FSI

In this paper, three different constitutive laws for mitral leaflets and two laws for chordae tendineae are selected to study their effects on mitral valve dynamics with fluid-structure interaction. We first fit these three mitral leaflet constitutive laws and two chordae tendineae laws with experimental data. The fluid-structure interaction is implemented in an immersed boundary framework with finite element extension for solid, that is the hybrid immersed boundary/finite element(IB/FE) method. We specifically compare the fluid-structure results of different constitutive laws since fluid-structure interaction is the physiological loading environment. This allows us to look at the peak jet velocity, the closure regurgitation volume, and the orifice area. Our numerical results show that different constitutive laws can affect mitral valve dynamics, such as the transvalvular flow rate, closure regurgitation and the orifice area, while the differences in fiber strain and stress are insignificant because all leaflet constitutive laws are fitted to the same set of experimental data. In addition, when an exponential constitutive law of chordae tendineae is used, a lower closure regurgitation flow is observed compared to that of a linear material model. In conclusion, combining numerical dynamic simulations and static experimental tests, we are able to identify suitable constitutive laws for dynamic behaviour of mitral leaflets and chordae under physiological conditions

Chemical Synthesis of Nanostructured Cobalt at Elevated Temperatures

Chemical synthesis is a versatile technique for fabricating novel nanostructured materials. In the Rieke process, a metal salt is reduced by an alkali in a hydrocarbon solvent to form small, highly reactive particles. Synthesis at an elevated temperature (200°C) increases the as-synthesized particle size and produces higher coercivities and remanence ratios than observed in similar syntheses at room temperature. The ratio of synthesis temperature to solvent boiling point appears to be an important parameter in both coercivity and oxidation resistance

Chemical Synthesis of Nanostructured Cobalt at Elevated Temperatures

Chemical synthesis is a versatile technique for fabricating novel nanostructured materials. In the Rieke process, a metal salt is reduced by an alkali in a hydrocarbon solvent to form small, highly reactive particles. Synthesis at an elevated temperature (200°C) increases the as-synthesized particle size and produces higher coercivities and remanence ratios than observed in similar syntheses at room temperature. The ratio of synthesis temperature to solvent boiling point appears to be an important parameter in both coercivity and oxidation resistance

Guiding and confining fast electrons by transient electric and magnetic fields with a plasma inverse cone

Copyright 2009 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Physics of Plasmas, 16(2), 020702, 2009 and may be found at http://dx.doi.org/10.1063/1.307592

Morphological measurements in computed tomography correlate with airflow obstruction in chronic obstructive pulmonary disease:systematic review and meta-analysis

To determine the correlation between CT measurements of emphysema or peripheral airways and airflow obstruction in chronic obstructive pulmonary disease (COPD).PubMed, Embase and Web of Knowledge were searched from 1976 to 2011. Two reviewers independently screened 1,763 citations to identify articles that correlated CT measurements to airflow obstruction parameters of the pulmonary function test in COPD patients, rated study quality and extracted information. Three CT measurements were accessed: lung attenuation area percentage &lt;-950 Hounsfield units, mean lung density and airway wall area percentage. Two airflow obstruction parameters were accessed: forced expiratory volume in the first second as percentage from predicted (FEV1 %pred) and FEV1 divided by the forced volume vital capacity.Seventy-nine articles (9,559 participants) were included in the systematic review, demonstrating different methodologies, measurements and CT airflow obstruction correlations. There were 15 high-quality articles (2,095 participants) in the meta-analysis. The absolute pooled correlation coefficients ranged from 0.48 (95 % CI, 0.40 to 0.54) to 0.65 (0.58 to 0.71) for inspiratory CT and 0.64 (0.53 to 0.72) to 0.73 (0.63 to 0.80) for expiratory CT.CT measurements of emphysema or peripheral airways are significantly related to airflow obstruction in COPD patients. CT provides a morphological method to investigate airway obstruction in COPD.aEuro cent Computed tomography is widely performed in patients with chronic obstructive pulmonary disease (COPD)aEuro cent CT provides quantitative morphological methods to investigate airflow obstruction in COPDaEuro cent CT measurements correlate significantly with the degree of airflow obstruction in COPDaEuro cent Expiratory CT measurements correlate more strongly with airflow obstruction than inspiratory CTaEuro cent Low-dose CT decreases the radiation dose for diagnosis and quantitative emphysema evaluation.</p

Possible Dibaryons with Strangeness s=-5

In the framework of $RGM$, the binding energy of the six quark system with strangeness s=-5 is systematically investigated under the SU(3) chiral constituent quark model. The single $\Xi^*\Omega$ channel calculation with spins S=0 and 3 and the coupled $\Xi\Omega$ and $\Xi^*\Omega$ channel calculation with spins S=1 and 2 are considered, respectively. The results show following observations: In the spin=0 case, $\Xi^* \Omega$ is a bound dibaryon with the binding energy being $80.0 \sim 92.4 MeV$. In the S=1 case, $\Xi\Omega$ is also a bound dibaryon. Its binding energy is ranged from $26.2 MeV$ to $32.9 MeV$. In the S=2 and S=3 cases, no evidence of bound dibaryons are found. The phase shifts and scattering lengths in the S=0 and S=1 cases are also given.Comment: 10 pages, late