Vapor-phase synthesis, growth mechanism and thickness-independent elastic modulus of single-crystal tungsten nanobelts

Single-crystal tungsten nanobelts with thicknesses from tens to hundreds of nanometers, widths of several micrometers and lengths of tens of micrometers were synthesized using chemical vapor deposition. Surface energy minimization was believed to have played a crucial role in the growth of the synthesized nanobelts enclosed by the low-energy {110} crystal planes of body-centered-cubic structure. The anisotropic growth of the crystallographically equivalent {110} crystal planes could be attributable to the asymmetric concentration distribution of the tungsten atom vapor around the nanobelts during the growth process. The elastic moduli of the synthesized tungsten nanobelts with thicknesses ranging from 65 to 306 nm were accurately measured using a newly developed thermal vibration method. The measured modulus values of the tungsten nanobelts were thickness-dependent. After eliminating the effect of surface oxidization using a core-shell model, the elastic modulus of tungsten nanobelts became constant, which is close to that of the bulk tungsten value of 410 GPa

Resonance Lifetimes from Complex Densities

The ab-initio calculation of resonance lifetimes of metastable anions challenges modern quantum-chemical methods. The exact lifetime of the lowest-energy resonance is encoded into a complex "density" that can be obtained via complex-coordinate scaling. We illustrate this with one-electron examples and show how the lifetime can be extracted from the complex density in much the same way as the ground-state energy of bound systems is extracted from its ground-state density

Case study of repopulating, re-urbanizing Cincinnati and Pittsburgh

Thesis: M.C.P., Massachusetts Institute of Technology, Department of Urban Studies and Planning, 2017.Cataloged from PDF version of thesis.Includes bibliographical references (pages 85-87).America's secondary cities are enjoying a well-documented urban renaissance. New residents and their dollars are reversing decades of disinvestment in the urban cores of conventionally less attractive, mid-sized US metro areas. Rising urban populations are largely due to new residents flocking from the suburbs; flat or declining metro populations suggest the cities themselves aren't becoming more competitive, but their urban areas are. Whether they seek a lower cost of living versus larger or coastal cities, or merely reflect the shifting preferences of millennials and empty nesters, many of these new urbanites say they seek vibrant and diverse living environments - value drivers that are sometimes undermined by unchecked private development in larger cities. As public and private forces in these places grapple with how best to meet this emerging demand, second-tier cities present a tremendous opportunity for holistic, community-minded economic growth that isn't possible in more competitive, established urban markets. This thesis explores the ways in which market-driven real estate development can be uniquely holistic and long-term focused in re-urbanizing centers, while also being financially advantageous for the private firms that can lead the way. The paper analyzes the extent to which, unlike for-profit developers in cities with more established urban preferences, firms in these secondary cities engage in long-view, community-minded projects as a means of creating or maintaining social diversity, as well as the factors that seem to encourage or hinder such efforts. I also analyze the extent to which these civic-minded approaches are regarded as drivers of long-term financial stability by the firms considered. I find that most for-profit firms in these cities have not, to date, made significant investments in holistic neighborhood-building. That said, a number of conditions have allowed for progressive, long-view projects to take place: public-backed development corporations, creative financing tools, and proactive local institutions, foundations, and corporations all lay the groundwork for private developers to do projects that create or maintain urban diversity. Conversely, I find that still-low rents, political favoritism, and other challenges often make it difficult for projects in second-tier cities to justify investing in the public realm. I conclude by presenting ideas for new programs that may unlock holistic-minded, profitable development. These include crowdsourced funding for creative subsidies, programs that tie support for local entrepreneurs to public loans and grants, and responsible development consortia, among others.by Ryan Kiracofe.M.C.P

Effect of energy intake on semen characteristics, sex drive, and scrotal circumference of yearling beef bulls

Simmental and Hereford bulls were fed individually three levels of energy per breed for 200 days beginning shortly after weaning. Then all bulls were adjusted to a roughage ration for 10 days, before grazing brome pasture for 38 days as one group. High energy did not decrease semen quality or sex drive. Energy level affected scrotal circumference of the Simmentals but not Herefords. Weight loss on pasture did not decrease semen quality or sex drive