Post-IPO Employment and Revenue Growth for U.S. IPOs, June 1996-2010

Analyzes employment and revenue growth, survival rate, sector, location, and venture capital involvement of U.S. companies that held initial public offerings on American markets from June 1996 through 2010, with a focus on firms younger than thirty years

The Salem Limestone in the Indiana Building-Stone District

Indiana Geological Survey Occasional Paper 38The limestone building material that has dominated the national market for more than a century is produced in the Bloomington-Bedford district of southern Indiana. Through the years the economy of this two-county area has grown and diversified, so that the stone industry no longer holds the prominent position it once held, but its influence on the economy of earlier years and on the established traditions is inescapable. More than 100 buildings on the Bloomington campus of Indiana University are of limestone from the district, as are nearly all government buildings and countless homes and commercial structures in both Bloomington and Bedford. Oolitic, a small town near the center of the building-stone district, traces its name back to the settlement of the area by immigrant stone workers from England who noticed the similarity of the Salem Limestone to the Portland Oolite, a popular building stone in England. The names of buildings, fraternal organizations, and school mascots testify to the influence of the stone industry on the people. The area has had a rich history because of uncommon properties of a common rock, limestone. The building-stone district has attracted geologists, architects, and laymen from all states and many foreign countries, and through the years we have guided hundreds of people through the quarries and mills. Always we have been warmly received by the owners and the workers. Partly on the basis of these tours and on questions that were asked during the tours, we prepared a guidebook that was first used at the meeting of the North-Central Section of the Geological Society of America in Bloomington on April 12, 1980. This paper has been modified from that coverage (Patton and Carr, 1980).Indiana Department of Natural Resource

Entrepreneurial ecosystems and industry knowledge: does the winning region take all?

Entrepreneurial ecosystems (EE) are composed not only of startups but also the organizations that support them. Theory has been ambivalent about whether an EE is spatially bounded or includes distant organizations. This exploratory study uses a time series of all Internet industry initial public offerings (IPO) to explore the locational changes not only of startups but also four key EE service providers: lawyers, investment bankers, venture capitalists, and board directors. We find that while the startups became only slightly more concentrated, the EE service providers concentrated more rapidly, as an industry center in Silicon Valley emerged. Our results suggest that over the industry life cycle, industry knowledge exhibits a tendency to spatially concentrate, and this results in a concentration of industry-specific EE service providers that is even greater than the more gradual concentration of startups. As a result, startups, wherever they are located, increasingly source EE services from the industrial knowledge concentration

The elastic moduli of a thick composite as measured by ultrasonic bulk wave pulse velocity

One thick filament-wound composite in the form of a large thick-walled cylinder with locally orthorhombic symmetry has been measured by ultrasonic velocity to calculate its elastic moduli. The basic assumption was that small sections of the composite could be treated as a homogeneous body analogous to a crystal for ultrasonic propagation. The experimental work and the results as best expressing homogeneous body theory are presented. Because of the high anisotropy with the normal to the layers (the three-direction) much different from the axial and hoop directions, it was necessary to calculate slowness surfaces with approximate values of c13 and c23 in order to find the directions of the Poynting vectors to use in making actual measurements on c12 and c13

Rare Earth Doped High Temperature Ceramic Selective Emitters

As a result of their electron structure, rare earth ions in crystals at high temperature emit radiation in several narrow bands rather than in a continuous blackbody manner. This study develops a spectral emittance model for films of rare earth containing materials. Although there are several possible rare earth doped high temperature materials, this study was confined to rare earth aluminum garnets. Good agreement between experimental and theoretical spectral emittances was found for erbium, thulium and erbium-holmium aluminum garnets. Spectral emittances of these films are sensitive to temperature differences across the film. Emitter efficiency is also a sensitive function of temperature. For thulium aluminum garnet the efficiency is 0.38 at 1700 K but only 0.19 at 1262 K

Rare Earth Doped Yttrium Aluminum Garnet (YAG) Selective Emitters

As a result of their electron structure, rare earth ions in crystals at high temperature emit radiation in several narrow bands rather than in a continuous blackbody manner. This study presents a spectral emittance model for films and cylinders of rare earth doped yttrium aluminum garnets. Good agreement between experimental and theoretical film spectral emittances was found for erbium and holmium aluminum garnets. Spectral emittances of films are sensitive to temperature differences across the film. For operating conditions of interest, the film emitter experiences a linear temperature variation whereas the cylinder emitter has a more advantageous uniform temperature. Emitter efficiency is also a sensitive function of temperature. For holminum aluminum garnet film the efficiency is 0.35 at 1446K but only 0.27 at 1270 K

Evolution of Local Microstructures (ELMS): Spatial Instabilities of Coarsening

This work examines the diffusional growth of discrete phase particles dispersed within a matrix. Engineering materials are microstructurally heterogeneous, and the details of the microstructure determine how well that material performs in a given application. Critical to the development of designing multiphase microstructures with long-term stability is the process of Ostwald ripening. Ripening, or phase coarsening, is a diffusion-limited process which arises in polydisperse multiphase materials. Growth and dissolution occur because fluxes of solute, driven by chemical potential gradients at the interfaces of the dispersed phase material, depend on particle size. The kinetics of these processes are "competitive," dictating that larger particles grow at the expense of smaller ones, overall leading to an increase of the average particle size. The classical treatment of phase coarsening was done by Todes, Lifshitz, and Slyozov, (TLS) in the limit of zero volume fraction, V(sub v), of the dispersed phase. Since the publication of TLS theory there have been numerous investigations, many of which sought to describe the kinetic scaling behavior over a range of volume fractions. Some studies in the literature report that the relative increase in coarsening rate at low (but not zero) volume fractions compared to that / 2 1/ 3 predicted by TLS is proportional to V(sub v)(exp 1/2), whereas others suggest V(sub v)(exp 1/3). This issue has been resolved recently by simulation studies at low volume fractions in three dimensions by members of the Rensselaer/MSFC team