Attached and separated boundary layers on highly cooled, ablating and nonablating models at M equals 13.8

Attached and separated boundary layers on highly cooled, ablating and nonablating models at Mach 13.

Freezing line of the Lennard-Jones fluid: a Phase Switch Monte Carlo study

We report a Phase Switch Monte Carlo (PSMC) method study of the freezing line of the Lennard-Jones (LJ) fluid. Our work generalizes to soft potentials the original application of the method to hard sphere freezing, and builds on a previous PSMC study of the LJ system by Errington (J. Chem. Phys. {\bf 120}, 3130 (2004)). The latter work is extended by tracing a large section of the Lennard-Jones freezing curve, the results for which we compare to a previous Gibbs-Duhem integration study. Additionally we provide new background regarding the statistical mechanical basis of the PSMC method and extensive implementation details.Comment: 18 pages, 6 figure

Modeling spontaneous formation of precursor nanoparticles in clear-solution zeolite synthesis

We present a lattice model describing the formation of silica nanoparticles in the early stages of the clear-solution templated synthesis of silicalite-1 zeolite. Silica condensation/hydrolysis is modeled by a nearest-neighbor attraction, while the electrostatics are represented by an orientation-dependent, short-range interaction. Using this simplified model, we show excellent qualitative agreement with published experimental observations. The nanoparticles are identified as a metastable state, stabilized by electrostatic interactions between the negatively charged silica surface and a layer of organic cations. Nanoparticle size is controlled mainly by the solution pH, through nanoparticle surface charge. The size and concentration of the charge-balancing cation are found to have a negligible effect on nanoparticle size. Increasing the temperature allows for further particle growth by Ostwald ripening. We suggest that this mechanism may play a role in the growth of zeolite crystals

Recent Distribution Records of the Little Brown Bat, Myotis lucifugus, in Manitoba and Northwestern Ontario

Until recently, the distribution of the Little Brown Bat (Myotis lucifugus) in Manitoba and northwestern Ontario was poorly documented. Since 1988, we have been banding and recapturing little browns throughout Manitoba and adjacent Lake of the Woods region in Ontario. All known hibernacula in the study area are recorded here for the first time, along with time of emergence. Connections between some hibernacula and summer nurseries are verified by band returns, ranging from 37 to 540 km

Patient satisfaction with lower gastrointestinal endoscopy: doctors, nurse and nonmedical endoscopists

Aim Assessment of patient satisfaction with lower gastrointestinal endoscopy (LGE) comprising colonoscopy and flexible sigmoidoscopy is gaining increasing importance. We have now trained non healthcare professionals such as nonmedical endoscopists (NMEs) to perform LGE to overcome shortage of trained endoscopists. The aim of this study was to prospectively determine patient satisfaction, factors affecting satisfaction with LGE and to compare with nurses, NME and medical endoscopists, in terms of patient satisfaction. Method Consecutive patients undergoing LGE answered specially developed patient satisfaction questionnaire at discharge and 24 h thereafter. This questionnaire was a modification of m-Group Health Association of America questionnaire. Construct and face validity of questionnaire were tested by an expert group. Demographic and clinical data was prospectively collected. Multivariate regression analysis was performed to determine factors influencing patient satisfaction. Results Some 503 patients were surveyed after LGE. Examinations were performed by nurse (n = 105), doctor (n = 191), or NMEs (n = 155). There were no differences between three groups in terms of completion rates/complications. No differences were detected between endoscopists in patient rating for overall satisfaction (P = 0.6), technical skills (P = 0.58), communication skills (P = 0.61) or interpersonal skills (0.59). Multivariate regression analysis showed that higher preprocedure anxiety, history of pelvic operations/hysterectomy and higher pain scores were associated with adverse patient satisfaction and preprocedure anxiety, history of hysterectomy and female gender were associated with higher pain scores. Conclusion This study has shown that there are no differences in patient satisfaction with LGE performed by nurse, doctor or NME. The most important factor affecting patient satisfaction is degree of discomfort/pain experienced by patient

Modelling the thermal stability of precursor nanoparticles in zeolite synthesis

We have modelled the thermal stability of silica nanoparticles commonly observed as precursors in the synthesis of zeolites. We performed canonical Monte Carlo and parallel tempering simulations on a lattice model that describes the self-assembly of nanoparticles under conditions at which they are observed experimentally. The effect of heating on the relative stability of the phases of the model was analysed by running simulations at various temperatures. At low temperature, the model yields a metastable multi-particle phase with a characteristic size distribution, which is separated by an energy barrier from the true equilibrium phase, a dense silica solid. As temperature increases, the system enters a transition region and eventually reaches the bulk phase. This transition is reminiscent of the experimentally observed transition from nanoparticles to zeolite. The transition temperature scales with the inverse of the system volume, approaching an asymptotic value for large system sizes. This indicates the transition temperature is a reproducible macroscopic property of the system. The transition temperature in the model is within the range of temperatures at which nanoparticles form zeolite crystals in experiments

Phase coexistence of cluster crystals: beyond the Gibbs phase rule

We report a study of the phase behavior of multiple-occupancy crystals through simulation. We argue that in order to reproduce the equilibrium behavior of such crystals it is essential to treat the number of lattice sites as a constraining thermodynamic variable. The resulting free-energy calculations thus differ considerably from schemes used for single-occupancy lattices. Using our approach, we obtain the phase diagram and the bulk modulus for a generalized exponential model that forms cluster crystals at high densities. We compare the simulation results with existing theoretical predictions. We also identify two types of density fluctuations that can lead to two sound modes and evaluate the corresponding elastic constants.Comment: 4 pages, 3 figure