The numerical and analytical study of bifurcation and multicellular flow instability due to natural convection between narrow horizontal isothermal cylindrical annuli at high Rayleigh numbers

This research effort deals with a numerical and analytical study of multicellular flow instability due to natural convection between narrow horizontal isothermal cylindrical annuli;Buoyancy-induced steady or unsteady flow fields between the annuli are determined using the Boussinesq approximated two-dimensional (2-D) Navier-Stokes (N-S) equations and the viscous-dissipation neglected thermal-energy equation. The vorticity-stream function formulation of the N-S equations is adopted;Both thermal and hydrodynamic instabilities are explored. An asymptotic expansion theory is applied to the N-S equations in the double-limit of Rayleigh number approaching infinity and gap width approaching zero. This double-limiting condition reduces the governing equations to a set of Cartesian-like boundary-layer equations. These equations are further simplified by considering the extreme limits of Pr →[infinity] and Pr → 0. The former limit yields an energy equation which retains the nonlinear convective terms, while the vorticity equation reduces to a Stokes-flow equation, signifying the potential for thermal instability. In the latter limit, the nonlinear terms in the vorticity equation remain, while the energy equation collapses to a one-dimensional conduction equation, signifying the potential for hydrodynamic instability;Thermal instability of air near the top portions of narrow annuli is considered for various size small gap widths. For these narrow gaps, the Rayleigh numbers corresponding to the onset of steady multicellular flow are predicted. Numerical solutions of the 2-D N-S equations also yield hysteresis behavior for the two-to-six and two-to-four cellular states, with respect to diameter ratios of 1.100 and 1.200. In contrast, an unsteady hydrodynamic multicellular instability is experienced near the vertical sections of narrow annuli when the Pr → 0 boundary-layer equations are solved numerically;In addition, analytical steady-state perturbative solutions to the boundary-layer equations are obtained. These results compare favorably to related numerical solutions of both N-S and Pr → 0 simplified equations;In all cases, finite-differenced solutions to the governing equations are obtained using a stable second-order, fully-implicit time-accurate Gauss-Seidel iterative procedure

What Do We Mean by Law and Social Transformation?

In Canada the entrenchment of the Charter of Rights and Freedoms generated a good deal of debate about the possibility of using law in the struggle for social transformation. Although couched in general terms, the current debate is ultimately about the possibility of asserting liberal democratic legal rights in courts in order to transform existing relations of subordination and domination. Somewhat remarkably, the positive claim that litigating entrenched legal rights encourages social transformation tends to be made almost exclusively at the theoretical level. Theoretical possibilities, rather than concrete victories, are invoked to support the claim for the transformative capacity of liberal legal rights. Instead of approaching the question of litigating social change from an exclusively theoretical perspective, this paper examines contemporary examples in order to illustrate some of the possibilities of and limits to this strategy. Specifically, the paper examines how both the labour and women\u27s movements have used the Canadian Charter of Rights and Freedoms to further their social, political and economic goals. Not only did these two groups adopt widely different strategies during the entrenchment process, what is entailed by the assertion of bourgeois legal rights has a different meaning for each. Thus, by contrasting the experience of the labour and women\u27s movements in invoking the Charter it is possible to begin to suggest the limits of liberal rights in the struggle for social transformation

1862-04-11 G.H. Bartholemew requests pay for Chaplain John F. Mines

https://digitalmaine.com/cw_me_2nd_regiment_corr/1271/thumbnail.jp

Experimental taxonomy, 1930-1950 : the impact of cytology, ecology, and genetics on ideas of biological classification

During the years between 1930 and 1950 a number of attempts were made to introduce techniques and ideas from cytology, ecology, and genetics into the field of taxonomy. Advocates of this "experimental taxonomy" believed that cytological, ecological, and genetic techniques would provide a rigorous, objective methodology to replace the traditional descriptive methods of taxonomy. Between 1930 and 1950 a number of impressive experimental taxonomic research programs were instituted. Despite the enthusiastic activity in experimental taxonomy, the introduction of cytological, ecological, and genetic methods into taxonomy was problematic. Taxonomists who borrowed from other biological fields were not taking methods and ideas from fully "mature" sciences. Cytology, ecology, and genetics were themselves going through major theoretical and methodological changes. The integration of methods and ideas from a number of complex, semi-autonomous biological disciplines was difficult. Experimental taxonomists, themselves, disagreed on the form this integration should take. Finally, although experimental taxonomy proved to be a viable and fruitful line of research, it did not constitute a complete reform of general taxonomic theory and practice. By 1950 most taxonomists realized that experimental taxonomy was a valuable, but limited, area of research within the more comprehensive discipline of general systematics

Materials evaluation using ultrasonic surface waves

The investigation reported in this thesis was prompted by the desire to develop an easy and reliable nondestructive method of testing to monitor changes in elastic properties of metals when they are subjected to creep, fatigue, and case hardening. The possibilities of the useful application of such a test will be invaluable to the aircraft industry. It was 'therefore suggested that the specimens used should be made from the type of materials Used in the aircraft industry. These were made of high strength alloys. The method of nondestructive testing was to excite ultrasonic surface waves on the surface of the specimens, and measuring the changes in surface wave velocity, when the material (specimens) are subjected to creep, fatigue, and case hardening. An ultrasonic goniometer was designed and constructed and, using the goniometer; critical angle reflectometry was used to excite the surface waves on the surface of the specimens. For the measurements during fatigue ,specimens were fatigued at high stress levels and low cycles. Constant amplitude alternating stresses with the specimen remaining in tension during the whole program type of loading was used. Most of the specimens were made of titanium (Ti230) but some work was also done on mild steel. The specimens used for creep were made from C263 Nickel alloy and Titanium 230. Each specimen was subjected to creep to a certain degree. The case hardened specimens were made of steel with carburized case. It was found that using ultrasonic surface waves it was possible to determine the depth of case hardening. Using a calibration curve drawn from the results obtained of the change in surface wave velocity for specimens with known case depths, it was possible to predict the case depths of specimens of unknown case depths; by measuring their surface wave velocities. Also, a frequency effect was observed whereby lower frequencies were found to better for detecting larger. case depths When specimens which were subjected to creep were considered, it was found that ultrasonic surface waves can detect early stages of creep. This was the case for both materials studied. A difference was observed in' the response to the surface waves for the two materials studied. In both cases a frequency effect was observed in that higher frequencies were better for detecting early creep. For both materials studied during fatigue, most of the change in surface wave velocity occurred during the very early stages of fatigue life. During the latter stages of fatigue life the rate of change was very much lower. No pattern was observed for the change in surface wave velocity with the number of fatigue cycles for either material. Lastly, measurements were done on brass, copper, aluminium, stainless steel and mild steel bar specimens, at the critical angle of incidence. For all the specimens it was found that the surface wave velocity changed with frequency

Sexual development and reproductive success of young female voles Microtus canicaudus

Exposure to a strange male increased the sexual development of 18-day-old females to a greater extent than did exposure to either young or adult females. Reproductive tract weights, mean diameters of Graafian follicles, and incidence of vaginal estrus were all greater in the male-exposed group during either the first or second week of treatment. No consistent differences in these parameters were apparent between the female-exposed groups. By the end of three weeks large numbers of females in all experimental groups appeared to have reached first estrus. Exposure to males did not appear to have a stimulatory effect on overall growth in 18-day-old females. Females were shown to be capable of becoming pregnant as early as 18 days of age. Young females produced healthy appearing litters of comparable weight to those of adult mothers. However, offspring survival to 18 days and mean weight of surviving young were much greater for litters born to adult females. Adult females also showed a much greater incidence of successful post-partum mating than did young females. Corpora lutea in both young and adult females increased in size throughout pregnancy. There was no increase in number of corpora lutea in either group. However, adult females tended to have a greater number of corpora lutea than embryos. The mean diameter of Graafian follicles was greater in adult females throughout pregnancy. By the end of pregnancy though, both young and adult females had large, well-developed Graafian follicles. Pseudopregnancy lasts for between one and two weeks in young females mated to vasectomized males. Corpora lutea in these females were indistinguishable from those of pregnancy at the end of one week. By the end of the second week these corpora lutea had degenerated. In some cases new sets of corpora lutea were present after two weeks

Quantitatively ranking incorrect responses to multiple-choice questions using item response theory

Research-based assessment instruments (RBAIs) are ubiquitous throughout both physics instruction and physics education research. The vast majority of analyses involving student responses to RBAI questions have focused on whether or not a student selects correct answers and using correctness to measure growth. This approach often undervalues the rich information that may be obtained by examining students’ particular choices of incorrect answers. In the present study, we aim to reveal some of this valuable information by quantitatively determining the relative correctness of various incorrect responses. To accomplish this, we propose an assumption that allows us to define relative correctness: students who have a high understanding of Newtonian physics are likely to answer more questions correctly and also more likely to choose better incorrect responses than students who have a low understanding. Analyses using item response theory align with this assumption, and Bock’s nominal response model allows us to uniquely rank each incorrect response. We present results from over 7000 students’ responses to the Force and Motion Conceptual Evaluation

Trace Fossils from the Shawangunk Formation in the Hudson Valley Indicate an Estuarine Depositional Environment

The Middle Silurian Shawangunk Formation crops out in the lower Hudson Valley and extends toward the southwest into New Jersey and Pennsylvania. It reaches a maximum thickness around Guymard (1,400 ft.; 400m) and gradually thins toward the northeast, pinching out near Binnewater, New York. The formation consists of gray conglomerate, quartz arenite, and minor shale. Worm burrows, Arthrophycus, Skolithos, Planolites?, and a bilobed resting trace have been found at different stratigraphic horizons in the Shawangunk Formation. All traces are associated with a finer, sandy matrix and/or hematite-rich interval rather than a coarse, pebbly quartz sandstone lithology dominant in the bulk of the unit, indicating a marine influence as well an environment with less energy than the braided stream environment inferred for most of the formation. Rivers and streams moving away from the eastern Taconic Mountains flowed into a westerly situated shallow marine basin. Eurypterids have previously been found on approximately the same stratigraphic levels as the traces and may be useful for constraining the depositional environment of these beds. Silurian eurypterids, now largely considered euryhaline, suggest that the environment of deposition was a marine-influenced estuary based on recent work documenting autochthonous assemblages of similar taxa in marginal marine settings. Association of eurypterids with Arthrophycus-dominated ichnofacies has been noted elsewhere in the Lower Silurian Tuscarora Formation in central Pennsylvania, suggesting a recurrent nearshore benthic assemblage

SU(N) Quantum Antiferromagnets and the Phase Structure of QED in the Strong Coupling Limit

We examine the strong coupling limit of both compact and non compact QED on a lattice with staggered fermions. We show that every SU(N) antiferromagnet with spins in a particular fundamental representation of the SU(N) Lie Algebra and with nearest neighbor couplings on a bipartite lattice is exactly equivalent to the infinite coupling limit of lattice QED with the numbers of flavors of electrons related to N and the dimension of spacetime D+1. We find that,for both compact and noncompact QED,when N is odd the ground state of the strong coupling limit breaks chiral symmetry in any dimensions and for any N and the condensate is an isoscalar mass operator. When N is even,chiral symmetry is broken if D is bigger or equal to 2 and N is small enough and the order parameter is an isovector mass operator. We also find the exact ground state of the lattice Coulomb gas as well as a variety of related lattice statistical systems with long ranged interactions.Comment: latex, 45 pages, DFUPG 69/9

Ostwald ripening in a Pt/SiO2 model catalyst studied by in situ TEM

Sintering of Pt nanoparticles dispersed on a planar SiO(2) support was studied by in situ transmission electron microscopy (TEM). A time-lapsed TEM image series of the Pt nanoparticles, acquired during the exposure to 10 mbar synthetic air at 650 degrees C, reveal that the sintering was governed by the Ostwald ripening mechanism. The in situ TEM images also provide information about the temporal evolution of the Pt particle size distribution and of the growth or decay of the individual nanoparticles. The observed Pt nanoparticle changes compare well with predictions made by mean-field kinetic models for ripening, but deviations are revealed for the time-evolution for the individual nanoparticles. A better description of the individual nanoparticle ripening is obtained by kinetic models that include local correlations between neighboring nanoparticles in the atom-exchange process