132 research outputs found
SYSTEMS AND METHODS OF DERIVATIVE STRATEGY SELECTION AND COMPOSITION
A method and apparatus of selecting derivative strategies, where candidate derivative strategies are selected from a set of essentially all possible derivative strategies available for an underlying, based upon a user\u27s market sentiment for an underlying, to perform favorably under the foreseen conditions being most appropriate to the user\u27s strategic intent and the choices afforded by the relevant markets
Moving I`iwi (Vestiaria coccinea) as a Surrogate for Future Translocations of Endangered `Akohekohe (Palmeria dolei)
Translocations often play an important role in the recovery of endangered species. To
assess feasibility for translocation of endangered `Akohekohe (Palmeria dolei), we
conducted an experimental translocation of I`iwi (Vestiaria coccinea) from east to west
Maui. Mist-netting, veterinary screening of candidate birds, and helicopter transport of
healthy I`iwi were successful, resulting in no injuries or mortalities. Translocated birds
were assigned to two types of release. Hard release birds were radio tagged and released
on the day of translocation. In contrast, soft release birds were held in large cages for 7
days and fed artificial nectar. During holding soft release I`iwi feeding rates, fecal
production, and mass were monitored. Soft release birds suffered 33% mortality during
the holding period. At the end of the holding period, soft release survivors were outfitted
with a radio transmitter and released. All translocated I`iwi were followed by radio
telemetry for an average of 21 days. Once released, soft release birds showed higher
rates of movement, possibly reflecting conflict with established hard released I`iwi. Our
results suggest that translocation efforts for wild `Akohekohe will be successful if hard
release protocols are followed
Characterisation of the porcine corneal epithelial stem/progenitor cell niche
It is widely accepted that the surface epithelium of the cornea is maintained by a population of stem cells that resides in the corneoscleral limbus. However, the extracellular matrix and surrounding cells that maintain this stem cell population and constitute the niche of these cells are not fully understood.
The aim of this thesis was to further characterise the extracellular matrix, specifically the chondroitin sulphate/dermatan sulphate distribution, and cellular components of the limbal epithelial stem cell niche using a porcine model. This was done using immunohistochemistry, transmission electron microscopy, scanning electron microscopy and creating 3D tissue reconstructions via serial block-face scanning electron microscopy (SBFSEM) and X-ray micro-computed tomography (microCT).
This thesis was the first to investigate using microCT to image the limbal/corneal epithelium and found the porcine cornea has one or more continuous limbal troughs that span across all limbal quadrants, as opposed to small, discrete limbal crypts as found in humans. These elongated projections of the limbal epithelium into the stroma contain basal epithelial cells positive for the putative limbal stem cell markers cytokeratin 19 and ABCB5.
The stroma immediately subjacent to the limbal trough is rich in the chondroitin sulphate sulphation motifs recognised by antibodies 6C3 and 3B3(+), as well as hyaluronic acid. The distribution of sulphated proteoglycans varies between the stroma and epithelial basement membranes of the porcine central cornea versus the limbus.
SBFSEM reconstructions demonstrate direct cell-cell contact between stromal niche cells and limbal basal epithelial cells in the porcine cornea, the third mammalian species to show this.
This thesis has shown marked differences in the limbal stem cell niche of the porcine eye from the human, but also confirming some shared characteristics. The newly identified limbal trough forms part of this niche, playing host to putative stem cells, where forms of chondroitin sulphate are in close proximity to these cells and stromal-epithelial cell interaction exists. These factors may play a role in stem cell maintenance in vivo in the porcine cornea and also could have uses in the culturing of limbal stem cells and future niche reconstruction
The Value of Instructor Interactivity in the Online Classroom
As the number of faculty teaching online continues to grow, so has the interest in and understanding of the role of instructor interaction in the online classroom. Online education provides a unique platform in which course design and teaching are independent factors. Understanding faculty and student perceptions about the shifting role of instructor interaction in the online classroom can provide insight on policies and procedures that can support student learning through student-instructor interaction. Participants included faculty and students responding to an anonymous online survey who indicated âonlineâ as their primary mode of teaching. Three key âvalueâ themes emerged as significantly valuable: instructor interactivity, instructor feedback on participation, and asynchronous interaction in discussion forums. These findings illuminate opportunities and areas of consideration for three stakeholders in the student-teacher interaction equation: faculty, faculty developers, and administrators that can be used to inform quality online teaching through instructor interactivity
Spatial and Temporal Variation of Epigaeic Beetle Assemblages (Coleoptera, Carabidae, Staphylinidae) in Aspen-Dominated Mixedwood Forests Across North-Central Alberta
Epigaeic beetle assemblages were surveyed using continuous pitfall trapping during the summers of 1992 and 1993 in six widely geographically distributed locations in Albertaâs aspen-mixedwood forests prior to initial forest harvest. Species composition and turnover (ÎČ-diversity) were evaluated on several spatial scales ranging from Natural Regions (distance between samples 120â420 km) to pitfall traps (40â60 m). A total of 19,885 ground beetles (Carabidae) representing 40 species and 12,669 rove beetles (non-Aleocharinae Staphylinidae) representing 78 species was collected. Beetle catch, species richness, and diversity differed significantly among the six locations, as did the identity of dominant species. Beetle species composition differed significantly between the Boreal Forest and Foothills Natural Regions for both taxa. Staphylinidae ÎČ-diversity differed significantly between Natural Regions, whereas Carabidae ÎČ-diversity differed among locations. Climate variables such as number of frost-free days, dry periods, and mean summer temperatures were identified as significant factors influencing beetle assemblages at coarse spatial scales, whereas over- and understory vegetation cover, litter depth, shade, slope, and stand age influenced beetle assemblages at finer spatial scales. Significant interannual variation in assemblage structure was noted for both taxa. Because composition of epigaeic beetle assemblages differed across spatial scales, forest management strategies based only on generalized understanding of a single location will be ineffective as conservation measures. In addition, site history and geographic variation significantly affect species distributions of these two beetle families across the landscape. Thus, we underscore Terry Erwinâs suggestion that biodiversity assessments focused on species assemblages at different spatial scales provide a sound approach for understanding biodiversity change and enhancing conservation of arthropod biodiversity
The microanatomy of Bowmanâs layer in the cornea of the pig: changes in collagen fibril architecture at the corneoscleral limbus
In most animals, Bowmanâs layer is a feature of the cornea of the eye, and lies between the sur-face epithelium and the stromal extracellular matrix that makes up the bulk of the cornea. It is com-prised of a condensation of disorganised collagen fibrils. However, it has been conjectured that not all species possess Bowmanâs layer, and pigs are a species that has classically been stated to lack this anatomical structure, although there is disa-greement in the published literature. Here, we studied the porcine cornea using transmission and scanning electron microscopy (TEM and SEM) to ascertain whether Bowmanâs layer existed. TEM identified a thin band of disorganised collagen fi-brils between the epithelial basement membrane and corneal stroma. SEM images of the central and peripheral corneal surfaces, following removal of the corneal epithelium by cell maceration, re-vealed a disorganised meshwork of collagen fibrils, with a highly aligned annulus of collagen at the limbus. In between the peripheral cornea and lim-bus, a âtransition zoneâ is observed where collagenfibrils start to align. Quantification of fibril alignment demonstrates a significant increase in collagen alignment from 0.08 ± 0.04 to 0.33 ± 0.07 (p < 0.001; n = 60; 0 = no alignment, 1 = full alignment) with increasing distance from the corneal centre. These data together lead us to conclude that the porcine cornea does include Bowmanâs layer, though it is thin (contributing roughly 0.2% of cor-neal thickness), and thus, reaffirms the porcine corneaâs similarity to its human counterpart and usefulness as a model system
Recovering vision in corneal epithelial stem cell deficient eyes
A healthy corneal epithelium, which is essential for proper vision and protection from external pathogens, is continuously replenished throughout life by stem cells located at the limbus. In diseased or injured eyes, however, in which stem cells are deficient, severe ocular problems manifest themselves. These are notoriously difficult to manage and as a result the last 20 or so years has seen a number of therapeutic strategies emerge that aim to recover the ocular surface and restore vision in limbal stem cell deficient eyes. The dominant concept involves the generation of laboratory cultivated epithelial cell sheets expanded from small biopsies of the epithelial limbus (for patient or donors) or another non-corneal epithelial tissue such as the oral mucosa. Typically, cells are grown on sterilised human amniotic membrane as a substrate, which then forms part of the graft, or specially formulated plastic culture dishes from which cells sheets can be released by lowering the temperature, and thus the adherence of the plastic to the cells. Overall, clinical results are promising, as is discussed, with new cultivation methodologies and different cell lineages currently being investigated to augment the treatment options for visual disturbance caused by a corneal epithelial limbal stem cell deficiency
Compositional controls on oceanic plates : geophysical evidence from the MELT area
Author Posting. © The Authors, 2005. This is the author's version of the work. It is
posted here by permission of Nature Publishing Group for personal use, not for redistribution. The
definitive version was published in Nature 437 (2005): 249-252, doi:10.1038/nature04014.Magnetotelluric (MT) and seismic data, collected during the MELT
experiment at the Southern East Pacific Rise (SEPR) constrain the distribution
of melt beneath this mid-ocean-ridge spreading center and also the evolution of the
oceanic lithosphere during its early cooling history. In this paper, we focus on
structure imaged at distances ~100 to 350 km east of the ridge crest, corresponding
to seafloor ages of ~1.3 to 4.5 Ma, where the seismic and electrical conductivity
structure is nearly constant, independent of age. Beginning at a depth of about 60
km, there is a large increase in electrical conductivity and a change from isotropic
to transversely anisotropic electrical structure with higher conductivity in the
direction of fast propagation for seismic waves. Because conductive cooling
models predict structure that increases in depth with age, extending to about 30
km at 4.5 Ma, we infer that the structure of young oceanic plates is instead
controlled by a decrease in water content above 60 km induced by the melting
process beneath the spreading center.US participation in the MELT experiment and subsequent analysis was funded by NSF grants through the Marine Geology and Geophysics Program, Ocean Sciences Division
Identification and Replication of Three Novel Myopia Common Susceptibility Gene Loci on Chromosome 3q26 using Linkage and Linkage Disequilibrium Mapping
Refractive error is a highly heritable quantitative trait responsible for considerable morbidity. Following an initial genome-wide linkage study using microsatellite markers, we confirmed evidence for linkage to chromosome 3q26 and then conducted fine-scale association mapping using high-resolution linkage disequilibrium unit (LDU) maps. We used a preliminary discovery marker set across the 30-Mb region with an average SNP density of 1 SNP/15 kb (Map 1). Map 1 was divided into 51 LDU windows and additional SNPs were genotyped for six regions (Map 2) that showed preliminary evidence of multi-marker association using composite likelihood. A total of 575 cases and controls selected from the tails of the trait distribution were genotyped for the discovery sample. Malecot model estimates indicate three loci with putative common functional variants centred on MFN1 (180,566 kb; 95% confidence interval 180,505â180, 655 kb), approximately 156 kb upstream from alternate-splicing SOX2OT (182,595 kb; 95% CI 182,533â182,688 kb) and PSARL (184,386 kb; 95% CI 184,356â184,411 kb), with the loci showing modest to strong evidence of association for the Map 2 discovery samples (p<10â7, p<10â10, and pâ=â0.01, respectively). Using an unselected independent sample of 1,430 individuals, results replicated for the MFN1 (pâ=â0.006), SOX2OT (pâ=â0.0002), and PSARL (pâ=â0.0005) gene regions. MFN1 and PSARL both interact with OPA1 to regulate mitochondrial fusion and the inhibition of mitochondrial-led apoptosis, respectively. That two mitochondrial regulatory processes in the retina are implicated in the aetiology of myopia is surprising and is likely to provide novel insight into the molecular genetic basis of common myopia
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