Effect of 1.0 MeV electron irradiation on shunt resistance in Si-MINP solar cells

Shunt resistance from 100 K to 400 K is compared for diffused and ion implanted cells before and after irradiation. R sub sh decreases from greater than 10 to the 7th power omega-square cm for T less than 250 K to 10 to the 4th power omega-square cm at 400 K for non-irradiated diffused cells. Electron irradiation causes a more rapid decrease in R sub sh for T greater than 250 K. Ion implanted cells exhibit a similar trend except that R sub sh is significantly less for T less than 250 K and is more sensitive to irradiation at these low temperatures. The mechanism of R sub sh appears to be a combination of multistep tunneling and trapping - detrapping in the defect states of the semiconductor. Radiation serves to increase the density of these states to decrease R sub sh

Leadership for the Twenty-First Century (text and audio)

The recording begins with Board of Trustees President E. Hugh Henning introducing Anderson. After Anderson concludes his remarks, at approx 32mins, there is a transition to speakers at the luncheon on the same day

Iowa Geology and the Tri-State Geological Field Conference

The Tri-State Geological Field Conference, initiated in 1933, has met in Iowa on 14 occasions. Guidebooks for these field conferences are important resources for planning geology field trips in Iowa. A summary is provided of each of the Tri-State conferences hosted in Iowa. A.C. Trowbridge, the Iowa representative on the original Tri-State planning committee, was a major contributor to Tri-State conferences

Iowa Geology: The Early Years

In 1975 on the occasion of the first one hundred years of the Iowa Academy of Science, Robert W. Hanson summarized the history of the organization. Additional historical accounts covering many of the science disciplines were published during the centennial year. Although geology was not treated separately in these special articles, the contributions of early geologists were important to the development of science in our state. Consequently, it is appropriate to consider the contributions of early geologists in Iowa in celebration of the one hundredth annual meeting of the Iowa Academy of Science. Included in the present report are the contributions of R. Ellsworth Call, Samuel Calvin, James Hall, Charles Keyes, W.J. McGee, David D. Owen, Frank Springer, Orestes Sc. John, James Todd, Charles Wachsmuth, Charles White, and A.H. Worthen. Correspondence in 1892 between Charles Keyes and Samuel Calvin provides historical background on the political climate in Iowa at the time of the establishment of the Iowa Geological Survey. Highlights of this correspondence are reported

lntraspecific Variation Within the Conodont Polygnathus brevilamina

Intraspecific variation was observed in a study of 177 well preserved specimens of the conodont Polygnathus brevilamina. Variations in the size of platform and in the degree of ornamentation of the platform are illustrated. These variations are present in juvenile specimens. The study indicates that the original definition of Polygnathus brevilamina is too narrow and that a broader concept of speciation is needed if conodont species are to be useable

Iowa\u27s Self-trained Paleontologists

Charles Wachsmuth (1829- 1896), merchant, Frank Springer (1848-1927), attorney, and Burnice Beane (1879- 1966), farmer, all made significant contributions in their studies of Iowa crinoids, although none of the three completed formal courses in geology or paleontology. Herbert Belanski was a young man, just starting to make major contributions to Iowa geology and paleontology, when he died in 1919. Belanski possessed only a high school degree, but he was recognized as an expert on Devonian paleontology. His collections from the Lime Creek and Shell Rock formations are noteworthy. At the time of his death, Belanski served as a curator in the Geology Department at the University of Iowa. A later curator at Iowa, Carlyle Campbell, was an enthusiastic amateur, self-taught as far as paleontology was concerned. Prominent among current workers is Harrell Strimple. Recently retired as research associate and curator at the University of Iowa, Strimple is author of some 300 papers on crinoids and contributor to the authoritative Treatise on Invertebrate Paleontology. Although Strimple never completed formal college course work in geology or paleontology, he has achieved international recognition for his research and publications on fossil echinoderms. Strimple developed an interest in geology and paleontology as a youth. This interest was stimulated by contacts with L. R. Laudon in 1935. From 1933 to 1959, Strimple was employed as an accountant and pursued paleontological work on a part-time basis, publishing his first paper in 1938. Since 1959, he has devoted full-time to paleontological work. The contributions of other self-trained workers to Iowa geology are reviewed, including the work of Calvin Levorson, Arthur Gerk, and Amel Priest

Characterization of Poly-Si Thin Films Deposited by Magnetron Sputtering onto Ni Prelayers

A method of producing a polycrystalline silicon thin film on a foreign substrate without subsequent annealing has been developed. Thermally evaporated 5–100 nm thick Nifilms served as prelayers for magnetron sputtered Si thin films. A continuous film was obtained as a result of metal induced growth of polysilicon during low temperature (below 600 °C) deposition. The film uniformity is promising for large area device applications. The influence of the Ni prelayer thickness on the grain size of thus obtained films was investigated. Atomic force microscopy and cross-sectional scanning electron microscopy studies revealed features in the 150–600 nm size range while x-ray diffraction and Raman spectra analysis predicted 50–100 nm diam randomly oriented grains and a complete absence of an amorphous phase. The carrier lifetime was evaluated to be 11 μs