Fabrication and characterization of multiscale electrospun scaffolds for cartilage regeneration

Recently, scaffolds for tissue regeneration purposes have been observed to utilize nanoscale features in an effort to reap the cellular benefits of scaffold features resembling extracellular matrix (ECM) components. However, one complication surrounding electrospun nanofibers is limited cellular infiltration. One method to ameliorate this negative effect is by incorporating nanofibers into microfibrous scaffolds. This study shows that it is feasible to fabricate electrospun scaffolds containing two differently scaled fibers interspersed evenly throughout the entire construct as well as scaffolds containing fibers composed of two discrete materials, specifically fibrin and poly(?-caprolactone). In order to accomplish this, multiscale fibrous scaffolds of different compositions were generated using a dual extrusion electrospinning setup with a rotating mandrel. These scaffolds were then characterized for fiber diameter, porosity and pore size and seeded with human mesenchymal stem cells to assess the influence of scaffold architecture and composition on cellular responses as determined by cellularity, histology and glycosaminoglycan (GAG) content. Analysis revealed that nanofibers within a microfiber mesh function to maintain scaffold cellularity under serum-free conditions as well as aid the deposition of GAGs. This supports the hypothesis that scaffolds with constituents more closely resembling native ECM components may be beneficial for cartilage regeneration

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

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

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

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

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

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