Interaction between the Galaxies IC 2163 and NGC 2207

VLA HI observations of the interacting pair IC 2163/NGC 2207 are presented. The velocity and structural anomalies of IC 2163 agree with predictions of N-body galaxy encounter simulations if IC 2163 recently underwent a strong, prograde, in-plane encounter with NGC 2207. The velocity disturbances in NGC 2207 suggests that the main tidal force on NGC 2207 was perpendicular to the disk of NGC 2207

CO Observations of the Interacting Galaxy Pair NGC 5394/95

Peer reviewe

Spitzer Space Telescope IRAC and MIPS observations of the interacting galaxies Ic 2163 and NGC 2207: clumpy emission

Peer reviewe

Performance optimization for rotors in hover and axial flight

Performance optimization for rotors in hover and axial flight is a topic of continuing importance to rotorcraft designers. The aim of this Phase 1 effort has been to demonstrate that a linear optimization algorithm could be coupled to an existing influence coefficient hover performance code. This code, dubbed EHPIC (Evaluation of Hover Performance using Influence Coefficients), uses a quasi-linear wake relaxation to solve for the rotor performance. The coupling was accomplished by expanding of the matrix of linearized influence coefficients in EHPIC to accommodate design variables and deriving new coefficients for linearized equations governing perturbations in power and thrust. These coefficients formed the input to a linear optimization analysis, which used the flow tangency conditions on the blade and in the wake to impose equality constraints on the expanded system of equations; user-specified inequality contraints were also employed to bound the changes in the design. It was found that this locally linearized analysis could be invoked to predict a design change that would produce a reduction in the power required by the rotor at constant thrust. Thus, an efficient search for improved versions of the baseline design can be carried out while retaining the accuracy inherent in a free wake/lifting surface performance analysis

Laser Doppler dust devil measurements

A scanning laser doppler velocimeter (SLDV) system was used to detect, track, and measure the velocity flow field of naturally occurring tornado-like flows (dust devils) in the atmosphere. A general description of the dust devil phenomenon is given along with a description of the test program, measurement system, and data processing techniques used to collect information on the dust devil flow field. The general meteorological conditions occurring during the test program are also described, and the information collected on two selected dust devils are discussed in detail to show the type of information which can be obtained with a SLDV system. The results from these measurements agree well with those of other investigators and illustrate the potential for the SLDV in future endeavors

The spread of primary schooling in sub-Saharan Africa: Implications for fertility change

Caldwell has hypothesized that the onset of the fertility transition would be linked with the achievement of “mass formal schooling.” In sub-Saharan Africa, a region where some countries have begun the fertility transition but many have not, the extent of progress toward mass schooling has not yet been assessed. This paper fills a gap in the literature using newly available Demographic and Health Survey data to assess schooling patterns and trends for 17 sub-Saharan African countries. As background to that assessment, the paper includes a literature review, an overview of the recent history of African education, and an evaluation of alternative sources of data on education. These data are linked to recent markers of fertility change in order to assess the potential importance of mass schooling for the fertility transition in Africa. In most of Africa, the promise embodied in early post-independence education progress whereby the next generation of Africans would be universally exposed to basic levels of formal schooling has yet to be realized. Countries such as Botswana, Ghana, Kenya, Namibia, South Africa, Tanzania, Zambia, and Zimbabwe are the exceptions rather than the rule, and most of these had achieved some form of mass schooling by the early 1980s. Since 1980, growth rates in educational participation and attainment have slowed or halted; in some countries, they have begun to decline. Most of these same countries were in the forefront of the fertility transition in Africa; in Ghana and Tanzania, fertility declines have begun more recently. A systematic empirical analysis of cross-country patterns across all 17 countries supports Caldwell’s hypothesis. Within this group, however, we find a few countries beginning to show signs of fertility transition despite limited progress in mass schooling. Côte d’Ivoire and Senegal are notable examples of this new development. In countries where population growth rates remain high and a growing proportion of the population is of school age, the achievement of mass schooling will be increasingly difficult in the future if high fertility persists. Therefore, if fertility declines are to continue, or in some cases begin, they will have to do so in the absence of mass schooling. Instead, fertility may respond to other vehicles of communication, such as the mass media, which will be increasingly pervasive, providing alternative mechanisms for the spread of cultural change

Ultrastructural Studies On Stomata Development In Internodes Of Avena Sativa

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141606/1/ajb209789.pd

V-V Bond-Length Fluctuations in Vox

We report a significantly stronger suppression of the phonon contribution to the thermal conductivity in VOx than can be accounted for by disorder of the 16 % atomic vacancies present in VO. Since the transition from localized to itinerant electronic behavior is first-order and has been shown to be characterized by bond-length fluctuations in several transition-metal oxides with the perovskite structure, we propose that cooperative V-V bond-length fluctuations play a role in VO similar to the M-O bond-length fluctuations in the perovskites. This model is able to account for the strong suppression of the thermal conductivity, the existence of a pseudogap confirmed by thermoelectric power, an anomalously large Debye-Waller factor, the temperature dependence of the magnetic susceptibility, and the inability to order atomic vacancies in VO.Comment: 5 pages, 5 figure

The signed loop approach to the Ising model: foundations and critical point

The signed loop method is a beautiful way to rigorously study the two-dimensional Ising model with no external field. In this paper, we explore the foundations of the method, including details that have so far been neglected or overlooked in the literature. We demonstrate how the method can be applied to the Ising model on the square lattice to derive explicit formal expressions for the free energy density and two-point functions in terms of sums over loops, valid all the way up to the self-dual point. As a corollary, it follows that the self-dual point is critical both for the behaviour of the free energy density, and for the decay of the two-point functions.Comment: 38 pages, 7 figures, with an improved Introduction. The final publication is available at link.springer.co

Diffusion limited aggregation as a Markovian process: site-sticking conditions

Cylindrical lattice diffusion limited aggregation (DLA), with a narrow width N, is solved for site-sticking conditions using a Markovian matrix method (which was previously developed for the bond-sticking case). This matrix contains the probabilities that the front moves from one configuration to another at each growth step, calculated exactly by solving the Laplace equation and using the proper normalization. The method is applied for a series of approximations, which include only a finite number of rows near the front. The fractal dimensionality of the aggregate is extrapolated to a value near 1.68.Comment: 27 Revtex pages, 16 figure