Mechanics of unsaturated granular media

The objective of this study was to investigate the effect of particle size distribution on the mechanics of remolded, unsaturated, granular materials. Vibratory compaction, moisture retention, and unconfined compression tests were conducted on five power function gradations of sand and silt. Analytical studies of the equivalent pore pressure and pore size distribution were conducted to explain the mechanical behavior of the materials in terms of the effective stress Law;The exponent term in the power function used to describe the particle size distributions is shown to be a characterizing parameter of the compaction and shear strength behavior. This parameter provides a way to relate changes in dry density, moisture potential, and shear strength with moisture content for different materials;High gradation exponents (more uniform gradations) are shown to produce lower bulking in vibratory compaction, lower air entry pressures in moisture retention, and lower apparent cohesion in shear strength. Very low gradation exponents (high fines content) produce the highest air entry pressures and apparent cohesion, but low dry density under standard vibratory compaction. This is explained in terms of the high equivalent pore pressures found in fine particulate materials with fine pore structures;The results of the experimental and analytical studies conducted on the five sand-silt mixtures are used to develop a model of the expected handling behavior of crushed, bulk solid materials in gravity flow systems. This model is further developed into a classification system for prediction of handling problems in coal-fired power plants

A Preliminary Stratigraphic Study of the Galena Group of Winneshiek County, Iowa

The rocks of the Galena Group have proved to be problematic in correlation. This problem is due to a variable lithofacies development. A preliminary investigation, although based upon exposures studied just within Winneshiek County, provides a method for field identification in Iowa of stratigraphic units currently used by the Illinois State Geological Survey within Illinois. Units under consideration at this time are restricted to the Dunleith, Wise Lake, and Dubuque Formations. Methods of identification and correlation employ in part such physical features as sequences of nodular chart bands, discontinuity surfaces, and sparry calcarenite bands. Investigation has disclosed a close relationship of these three features. A composite graphic column is provided, with key identification factors, for each of the subdivisions together with reference localities where the strata under investigation may be observed in sequence

Unusual Beach Deposits in Oolite Carbonate Environments Mississippian and Recent

Thousands of small fossils were collected from unusual lenses within the Cyathophyllum Zone, Gilmore City Limestone (Mississippian) in a large quarry near Humboldt, Iowa. These rare lenses occur in an interval 1-2.5m thick that shows an extreme variability of facies. An intensive search of other Gilmore City outcrops revealed no similar lenses. The rest of the interval, outside the lenses, contained larger fossils and fossil fragments. The small fossils in the lenses are remarkably well preserved, the gastropods particularly so. Comparison of the Gilmore City Limestone with Recent oolitic deposits at Paradise Island in the Bahamas leads to the conclusion that these unusual lenses probably were a backshore deposit. The Bahamian deposits provide evidence for interpretation of these fossils as size-sorted rather than dwarfed. Early carbonate coating is hypothesized to explain the exceptional preservation of the Mississippian fossils

New Flexible Crinoids from The Upper Devonian of North Central Iowa

Complete crinoid dorsal cups and crowns are virtually unknown from the Lime Creek Formation and Amana beds except for one partial crown of Dactylocrinus stellatimbasalis (Thomas) 1924. A partial and a complete crown and one dorsal cup belonging to Apodactylocrinus Strimple and Levorson, new genus, are described as A. keithi Strimple and Levorson, n. sp. and A. amanaensis Strimple and Levorson, n. sp

Devonian Ammonoid Manticoceras From Iowa

Recovery of rare, well-preserved representatives of Manticoceras from Upper Devonian (Frasnian) strata of north and east-central Iowa allows clarification of the poorly understood species Manticoceras regulare Fenton & Fenton, and marks the first recorded North American occurrence of Manticoceras lindneri Glenister. The faunal horizons correlate with the upper Manticoceas cordatum (1-y) ammonoid zone and the Palmatolepis gigas conodont zone. M. regulare can be recognized by its narrowly discoidal conch, relatively broad sutural elements, and mature conch diameter of approximately 11 cm. Occurrences of M. regulare have been restricted to the Amana Beds of the Independence Shale and Cerro Gordo Member of the Lime Creek Formation. The larger M. lindneri (mature diameter of approximately 19 cm) possesses a moderately wide conch and narrow sutural elements. All known Iowa representatives are from the Owen Member of the Lime Creek Formation in the north-central portion of the state. The only other known occurrence of M. lindneri is from the lower Virgin Hills Formation, Fitzroy Basin, Western Australia. Recently proposed Devonian paleogeographic reconstructions suggest that such a wide distribution may be attributed to the dispersal effects of warm, equatorial currents

Direct and indirect co-culture of chondrocytes and mesenchymal stem cells for the generation of polymer/extracellular matrix hybrid constructs

In this work, the influence of direct cell–cell contact in co-cultures of mesenchymal stem cells (MSCs) and chondrocytes for the improved deposition of cartilage-like extracellular matrix (ECM) within nonwoven fibrous poly(∊-caprolactone) (PCL) scaffolds was examined. To this end, chondrocytes and MSCs were either co-cultured in direct contact by mixing on a single PCL scaffold or produced via indirect co-culture, whereby the two cell types were seeded on separate scaffolds which were then cultured together in the same system either statically or under media perfusion in a bioreactor. In static cultures, the chondrocyte scaffold of an indirectly co-cultured group generated significantly greater amounts of glycosaminoglycan and collagen than the direct co-culture group initially seeded with the same number of chondrocytes. Furthermore, improved ECM production was linked to greater cellular proliferation and distribution throughout the scaffold in static culture. In perfusion cultures, flow had a significant effect on the proliferation of the chondrocytes. The ECM contents within the chondrocyte-containing scaffolds of the indirect co-culture groups either approximated or surpassed the amounts generated within the direct co-culture group. Additionally, within bioreactor culture there were indications that chondrocytes had an influence on the chondrogenesis of MSCs as evidenced by increases in cartilaginous ECM synthetic capacity. This work demonstrates that it is possible to generate PCL/ECM hybrid scaffolds for cartilage regeneration by utilizing the factors secreted by two different cell types, chondrocytes and MSCs, even in the absence of juxtacrine signaling

Additional Crinoid Specimens from the Shellrock Formation (Upper Devonian) of Iowa

Well preserved crinoids from the Shellrock Formation (Upper Devonian) of Iowa are extremely rare. Several well preserved specimens collected by one of us (Levorson) have led to new generic assignments of the species originally described as Nassoviocrinus goldringae Belanski, 1928, to Glossocrinus goldringae, n. comb., and of Hexacrinus springeri Thomas to Cerasmocrinus springeri, n. comb. The latter is the type species of Cerasmocrinus, new genus

Fossil crinoid studies

26 p., 9 fig.http://paleo.ku.edu/contributions.htm

Edrioasteroids (Echinodermata) of the Maquoketa Formation of Iowa

Two specimens of edrioasteroids have been found in the Maquoketa Formation, Richmond Group, Upper Ordovician of Iowa. This occurrence extends the geographic range of both genera, lsorophus Foerste (1917) and Edriophus Bell (1975) into Iowa which is the westernmost occurrence of these genera formerly recorded only east of Illinois. Isorophus was found in a horizon essentially barren of fossils but Edriophus is coexistent with more common echinoderms of the Maquoketa, including the crinoid genera Carabocrinus and Porocrinus

A New Species of Bothriocidaris (Echinoidea) from the Cincinnatian Maquoketa Group of Iowa

A new species of echinoid , Bothriocidaris maquoketensis, has been discovered in the Cincinnatian (Upper Ordovician) Fort Atkinson Formation, Maquoketa Group, of northeastern Iowa. The new species is characterized by two widely spaced primary perforate tubercles on opposite sides of the peripodia and by numerous paired interambulacral plates. This occurrence extends the geographic and stratigraphic range of Bothriocidaris in North America