INVESTIGATION OF ADHESION AND COHESION OF METALS IN ULTRAHIGH VACUUM.

Adhesion and cohesion of metals in ultrahigh vacuu

A textural and chemical study of white mica in the South Mountain Batholith, Nova Scotia: primary versus secondary origin

White mica (HM) In peralumlnous granitoid rocks of the South Mountain Batholith (SMB) and East Kemptville leucogranite (EKL) of Nova Scotia have been examined to see if parameters can be used to distinguish between primary and secondary grains. Texturally very little of the UN in the SMB can unequivocally be classified as primary, whereas most of the UM In the EKL is consistent with such an origin. Although discriminant diagrams which utilize major element chemistry do not provide unambiguous divisions between primary and secondary HM, there appear to be some chemical trends which indicate that the bulk composition of the host rock is an important control. This is best exemplified by volatile (i.e. F) and trace element contents. Including the rare earth elements. For example, F, Li, Rb and Cs are systematically higher In UM from relatively more evolved units of the SMB. The importance of bulk rock composition is also indicated by the enrichment of lithophile elements In UM from the EKL. itself enriched in these same elements. The octahedral impurities in UM of the SMB are accommodated via blotltlc and pbengitic substitutions, whereas UM from the EKL is dominantly pbengitic. Comparison to experimentally determined stability fields for muscovite indicate that HM from the SMB re-equilibrated to 500-600oC In the more primitive units and 400-550oC In the more evolved units and greisens. Recent experimental data also suggest crystallization of the UM may have occurred at pressures of ca. 2 kb in melts with 2-3 wt.% H2O. RÉSUMÉ On a examiné les micas blancs (MB) dans les roches granltoldes péralumlneuses du Batholite de South Mountain (BSM) et du leucogranite d'East Kemptville (LEK) en Nouvelle-Écosse afin de déterminer si certains paramétres peuvent servlx a dlstinguer les grains primalres des grains secondaires. É l'égard de la texture, une très faible proportion des MB dans le BSM peuvent, sans l’ombre d'un doute, être classes comae primalres alors que la plupart des MB dans le LEK sont compatibles avec une telle orlglne. Bien que les diagrammes discriminant par chimle des éléments majeure ne procurent aucune Unite precise entre les MB primalres et secondaires, on semble y discemer des tendances chlmiques lndlquant une Influence préponderante de la composition totale de l'encaissant. Les contenus en éléments volatiles (i.e. F) et en traces, y comprises les terres rares, en sont la meilleure illustration. Par exemaple, la teneur en F, Li, Rb et Cs est systèmatiquement plus éleveé dans les MB provenant des unités plus évoluées, par comparaison, du BSM. L'importance de la composition totale de la roche est aussi attestée par l'enrichtssement en éléments lithophiles des MB du LEK (luimeme enrichl en ces éléments). L'accoramodation des impurités octaédriques dans les MB du BSM se fait par le biais de substitutions biotitiques et phengitiques alors que les MB du LEK sont surtout phengitiques. Une comparaison des MB du BSM aux doroaines de stabilites de la muscovite détermines experimentalement révèle que leur ré- équilibrage s'est effectue entre 500 et 600oC dans les unités les plus primitives et entre 400 et 550oC dans les unités plus évoluées et les greisens. À la lumlère de données expérimentales récentes, la cristallisation des MB aurait eu lieu àa des pressions d'environ 2 kb dans des bains ayant de 2 à 3 % en poids d'H2O. [Traduit par le journal

A comparison of the effects of fatigue on subjective and objective assessment of situation awareness in cycling

Maximal effort on a 30 km Time Trial (TT30) was examined to assess whether it would elicit changes in objective and subjective tests of the participants’ perception of the environment and their ability to anticipate future occurrences (situation awareness; SA) and to determine the effect of post-exercise recovery on SA. Nine experienced (5.22 ± 2.77 years) road cyclists had their objective and subjective levels of SA assessed prior to and at the completion of two TT30. The participants’ results were compared to measurements of maximal oxygen uptake (VO2max), peak power output (PPO), age and years of competitive cycle racing experience. Fatigue resulting from maximal effort on a TT30 produced significant changes in both the objective and subjective test of SA. Effect sizes of 0.93 and 0.99 indicated that the first and second TT30 were likely or almost certain to have a beneficial effect on the objective assessment of SA. However, the effect sizes of 0.97 and 0.95 relating to the subjective assessment of cognitive performance on the first and second TT30 showed that it was very likely the participants’ had an increased difficulty in maintaining SA. A recovery period of up to three minutes post TT30 had no effect on SA. Changes in SA had no relationship with measurements of VO2max, peak power output (PPO), age and years of competitive cycle racing experience. The findings suggest that within a laboratory environment, participants consistently underestimate their ability to make accurate assessments of their cycling environment compared to objective measures of their SA

Method of extending hyperfine coherence times in Pr^3+:Y_2SiO_5

In this letter we present a method for increasing the coherence time of praseodymium hyperfine ground state transitions in Pr^3+:Y_2SiO_5 by the application of a specific external magnetic field. The magnitude and angle of the external field is applied such that the Zeeman splitting of a hyperfine transition is at a critical point in three dimensions, making the first order Zeeman shift vanishingly small for the transition. This reduces the influence of the magnetic interactions between the praseodymium ions and the spins in the host lattice on the transition frequency. Using this method a phase memory time of 82ms was observed, a value two orders of magnitude greater than previously reported. It is shown that the residual dephasing is amenable quantum error correction

Rydberg transition frequencies from the Local Density Approximation

A method is given that extracts accurate Rydberg excitations from LDA density functional calculations, despite the short-ranged potential. For the case of He and Ne, the asymptotic quantum defects predicted by LDA are in less than 5% error, yielding transition frequency errors of less than 0.1eV.Comment: 4 pages, 6 figures, submitted to Phys. Rev. Let

Simple and scalable growth of AgCl nanorods by plasma-assisted strain relaxation on flexible polymer substrates

Implementing nanostructures on plastic film is indispensable for highly efficient flexible optoelectronic devices. However, due to the thermal and chemical fragility of plastic, nanostructuring approaches are limited to indirect transfer with low throughput. Here, we fabricate single-crystal AgCl nanorods by using a Cl 2 plasma on Ag-coated polyimide. Cl radicals react with Ag to form AgCl nanorods. The AgCl is subjected to compressive strain at its interface with the Ag film because of the larger lattice constant of AgCl compared to Ag. To minimize strain energy, the AgCl nanorods grow in the [200] direction. The epitaxial relationship between AgCl (200) and Ag (111) induces a strain, which leads to a strain gradient at the periphery of AgCl nanorods. The gradient causes a strain-induced diffusion of Ag atoms to accelerate the nanorod growth. Nanorods grown for 45 s exhibit superior haze up to 100% and luminance of optical device increased by up to 33%. ? The Author(s) 2017.114Ysciescopu

Baryogenesis in the Two-Higgs Doublet Model

We consider the generation of the baryon asymmetry in the two-Higgs doublet model. Investigating the thermal potential in the presence of CP violation, as relevant for baryogenesis, we find a strong first-order phase transition if the extra Higgs states are heavier than about 300 GeV. The mass of the lightest Higgs can be as large as about 200 GeV. We compute the bubble wall properties, including the profile of the relative complex phase between the two Higgs vevs. The baryon asymmetry is generated by top transport, which we treat in the WKB approximation. We find a baryon asymmetry consistent with observations. The neutron electric dipole moment is predicted to be larger than about 10^{-27}ecm and can reach the current experimental bound. Low values of tan\beta are favored.Comment: 25 pages, 7 figure

Applications of aerospace technology to petroleum extraction and reservoir engineering

Through contacts with the petroleum industry, the petroleum service industry, universities and government agencies, important petroleum extraction problems were identified. For each problem, areas of aerospace technology that might aid in its solution were also identified, where possible. Some of the problems were selected for further consideration. Work on these problems led to the formulation of specific concepts as candidate for development. Each concept is addressed to the solution of specific extraction problems and makes use of specific areas of aerospace technology

Bostonia. Volume 11

Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs