Kinematics of Brittle and Ductile Deformation in the Catoctin Formation near Rockfish Gap, Virginia

Beneath Rockfish Gap, one of the lowest elevations along the crest of the Blue Ridge Mountains in Virginia, sits the historic 1858 Blue Ridge Tunnel (BRT). The BRT cuts directly through foliated metabasalts and metasedimentary rocks of the Ediacaran Catoctin Formation and provides a rare 3-dimensional exposure of the Blue Ridge cover sequence on the western limb of the Blue Ridge Anticlinorium. The purpose of this study is to characterize brittle and ductile deformation features in the Catoctin Formation in the BRT to determine their kinematic history. The Catoctin Formation includes a thick sequence of metabasaltic greenstone with thin layers of meta-arkose, sandstone, phyllite and conglomerates that formed between 570-550 Ma. In the arkoses and conglomerates, quartz and perthitic feldspars are the dominant clasts and are typically surrounded by a sericite matrix. Foliation strikes to the NE and dips moderately to the SE with down dip chlorite elongation lineations. Large (1 - 10 m) epidote-rich sandstone boudins typically display top-to-the NW asymmetry. Small, localized folds also occur in the sedimentary units and are tight, overturned NW-verging folds, consistent with NW-directed Neoacadian ductile deformation. Foliation in the greenstone is cut by low-angle top-to-the west shear zones that likely represent the later stages of deformation. Petrographic analysis reveals microstructures formed from dissolution, mass transfer, and volume loss processes under lower greenschist facies conditions. Mineral assemblages indicate that the Catoctin Formation at Rockfish Gap experienced temperatures between 300ºC - 400ºC. The Catoctin Formation is cut by two dominant fracture sets, a WNW-ESE set and NE-SW set that formed from two separate brittle deformation events; the former from the late Alleghanian Orogeny, and the latter from Atlantic rifting in the early Mesozoic

"Flags and Slots": Special Interest Groups and Selective Admissions

This paper combines the results of two studies, one from the perspective of institutions and one from the perspective of students, to determine and define the role played by special interest groups in selecting students for admission to college and university. Although there have been allusions to the existence of selection processes that categorize applicants in terms of various special talents and skills, and of racial, ethnic, or geographic origin, relatively little is known about how wide- spread those processes are and how they actually operate at highly selective colleges and universities. Also, little is known about how special interest group selection is perceived by applicants and their schools. The studies indicate how and why special interest group selection works, and shows that the process is widely used. The studies also indicate that, although applicants are aware of the process, their perception of it does not coincide with either the motives or the expectations of the colleges and universities that deploy it.Cet article, qui regroupe les résultats de deux études, l'une axée sur l'optique des établissements et l'autre sur celle des étudiants, vise à déterminer et à définir le rôle que jouent les groupes d'intérêt spéciaux dans le processus de sélection des étudiants ayant fait une demande d'admission au collège et à l'université. Bien qu'il ait été fait allusion à l'existence de processus de sélection classant par catégorie les candidats, selon leurs compétences et talents particuliers, ainsi que leur origine raciale, ethnique et géographique, on détient en fait assez peu de données sur la mesure dans laquelle ces processus sont généralisés et sur la manière dont ils sont appliqués dans les universités et collèges hautement sélectifs. En outre, on sait peu de chose sur la manière dont les candidats et leur école perçoivent la sélection des groupes d'intérêt spéciaux. Les études expliquent la manière dont fonctionne la sélection des groupes d'intérêt spéciaux et les raisons pour lesquelles celle-ci marche bien et montrent que le processus est appliqué à grande échelle. Les études indiquent aussi que, si les candidats sont au courant de l'existence du processus, la façon dont ils le perçoivent ne correspond ni aux motifs ni aux attentes des collèges et universités qui y ont recours

Cognition, agency theory, and organizational failure : a Saskatchewan Wheat Pool case study

The Saskatchewan Wheat Pool went from being the largest grain handler in western Canada in the mid 1990s to undertaking a $405 million debt restructuring in January 2003. Provincial grain handling market share had been over 60 percent for two decades prior to the Pool becoming publicly traded in 1996. With the share conversion, the Pool began a capital expenditure program in an effort to adapt to industry deregulation and to compete with the multinationals that were entering western Canada. This program was not successful. SWP’s long-term debt increased five fold over the period 1996–1999 and consecutive multi-million dollar net losses were incurred followed by the debt restructuring.This thesis uses dominant logic theory and the principal-agent problem to analyze what went wrong at SWP. Theory suggests organizations faced with major industry change may have difficulty revising their dominant logic, which leads to organizational failure. Not only is there a tendency to hold on to established beliefs, but the creation of new beliefs is prone to error because of bounded rationality. The existence of a principal-agent problem can worsen an organization’s ability to revise its dominant logic. Information asymmetry and the principal’s trust of the agent can lead to inaccurate beliefs and ineffective strategies being approved. The results of personal interviews with twenty-one past management and elected Saskatchewan Wheat Pool personnel and grain industry affiliates are presented and analyzed in a case study format. The results suggest that deregulation of the grain handling industry and the anticipated arrival of multinational competitors pressured the Pool to respond quickly to major industry change. The Pool had difficulty revising its dominant logic; it retained outdated beliefs and accepted inaccurate new beliefs. Interviewees described how some investments were built on erroneous beliefs and lacked complete due diligence. Evidence suggests the principal-agent problem was also at play. The need for confidentiality after the share conversion increased information asymmetry, and management took advantage of the board’s lack of experience as investments extended beyond the farm gate. The principal-agent problem in conjunction with an inaccurate revised dominant logic is a reasonable explanation for the Pool’s failure

U-Pb Zircon Geochronology and Structure of regional blueschist units in the Easton metamorphic suite, Northwest Cascades, WA

The Easton metamorphic suite of the Northwest Cascades Thrust System (NWCS) is a well-preserved subduction accretion complex in Washington State. The regional blueschist units of the Easton metamorphic suite include the Mt. Josephine semi-schist, Darrington Phyllite, and Shuksan greenschist/blueschist and all are interpreted to have accreted after the onset of Jurassic subduction beneath North America. This study uses zircon U-Pb geochronology, structure, and field observations to test the regional correlations between units in the Easton metamorphic suite and address models for the timing of subduction accretion along the North American margin in the Late Jurassic – Early Cretaceous. The results suggest that previously correlative units in the Easton metamorphic suite are instead structurally distinct litho-tectonic units. The Mt. Josephine semi-schist has at least two distinct groups of maximum depositional ages at ~144 Ma and ~122 Ma and suggests different sources within the same unit or that the Mt Josephine semi-schist consists of units accreted at separate times. The Lummi Formation in the NWCS yields similar maximum depositional ages as the older portions of the Mt Josephine semi-schist and may be correlative. The oldest portions of the Mt. Josephine appear to be ~8 m.y. younger than the Darrington phyllite and the youngest Mt. Josephine maximum depositional ages are younger than previously published white mica 40Ar/39Ar ages of the Darrington. The Shuksan greenschist has a protolith age of ~166 Ma but the structural and metamorphic history is different from the Darrington phyllite and the two units should be considered separately. The geochronology presented in this study documents an almost complete continuum of zircon ages from the Mid-Jurassic up to ~120 Ma. Deposition and subsequent quick subduction accretion in the Easton metamorphic suite occurred ~30 m.y. earlier than the main accretionary phase in the Franciscan of California and suggests that proposed changes in relative Pacific - North American plate motion did not solely drive changes from subduction erosion to subduction accretion

Integral points on elliptic curves and explicit valuations of division polynomials

Assuming Lang's conjectured lower bound on the heights of non-torsion points on an elliptic curve, we show that there exists an absolute constant C such that for any elliptic curve E/Q and non-torsion point P in E(Q), there is at most one integral multiple [n]P such that n > C. The proof is a modification of a proof of Ingram giving an unconditional but not uniform bound. The new ingredient is a collection of explicit formulae for the sequence of valuations of the division polynomials. For P of non-singular reduction, such sequences are already well described in most cases, but for P of singular reduction, we are led to define a new class of sequences called elliptic troublemaker sequences, which measure the failure of the Neron local height to be quadratic. As a corollary in the spirit of a conjecture of Lang and Hall, we obtain a uniform upper bound on h(P)/h(E) for integer points having two large integral multiples.Comment: 41 pages; minor corrections and improvements to expositio

A Tale of Two Sylamores: Understanding Relationships Among Land Use, Nutrients, and Aquatic Communities Across a Subsidy-Stress Gradient

Agricultural land use is known to degrade aquatic systems with high inputs of nutrients, sediments, and pesticides. Increased nutrients can lead to increased algal growth and thus possible hypoxic conditions in slow moving water, while increased sediment loads have been shown to obstruct light and reduce substrate stability. These conditions negatively impact primary producers, macroinvertebrates, and fish. However, small-scale changes in land use can subsidize an aquatic ecosystem instead, where an increase in nutrients allows nutrient-limited biota to flourish, and minor increases in sedimentation may help support populations of collector-filterers. The stimulation in performance caused by small disturbances is part of the subsidy-stress gradient, where increasing perturbation subsidizes an ecosystem until a certain threshold is reached, at which a decline in performance and increased variability starts to occur. The North and South Sylamore watersheds in north Arkansas provide a useful template to investigate the subsidy-stress gradient in relation to land use. North Sylamore flows through the Ozark National Forest and has a heavily forested catchment, while South Sylamore flows through mostly private land, some of which is pasture (23%). Physicochemical, macroinvertebrate, and fish data were collected from multiple sites within each watershed to determine if South Sylamore is exhibiting a response to pasture/agriculture characteristic of a subsidy-stress gradient. Sites within South Sylamore had significantly higher nitrate levels, larger macroinvertebrate populations dominated by collector-filterers, and greater abundance of algivorous fish, suggesting South Sylamore may be subsidized by the surrounding pastoral lands. However, South Sylamore also had a significantly lower proportional abundance of sensitive macroinvertebrate taxa and more unique tolerant fish taxa, suggesting South Sylamore is experiencing stress as well. Habitat quality of South Sylamore could be improved by restoration of trees within the riparian zone. Monitoring aquatic systems for subsidy-stress responses can inform restoration/management decisions and guide intervention prior to watersheds and aquatic communities becoming overly stressed

Characteristics and Outcomes of Patients Discharged Directly Home From the Pediatric Intensive Care Unit

Introduction: Patients admitted to the pediatric intensive care unit (PICU) typically transfer to an acute care floor prior to discharge (ACD). Various circumstances, including rapid clinical improvement, technology dependence, or capacity constraints, may lead to discharge directly to home from a PICU (DDH). This practice has been studied in adult intensive care units, but research is lacking for PICU patients. Methods: We aimed to describe characteristics and outcomes of patients requiring PICU admission who experienced DDH versus ACD. We conducted a retrospective cohort study of patients ≤18 years old admitted to our academic, tertiary care PICU between 1/1/15 and 12/31/20. Patients who died or were transferred to another facility were excluded. Baseline characteristics (including home ventilator dependence) and markers of illness severity, specifically the need for vasoactive infusion or new mechanical ventilation, were compared between groups. Admission diagnoses were categorized using the Pediatric Clinical Classification System (PECCS). Our primary outcome was hospital readmission within 30 days. Results: Of 4042 PICU admissions during the study period, 768 (19%) were DDH. Baseline demographic characteristics were similar, although DDH patients were more likely to have a tracheostomy (30% vs 5%, P < .01) and require a home ventilator at discharge (24% vs 1%, P < .01). DDH was associated with being less likely to have required a vasoactive infusion (7% vs 11%, P < .01), shorter median length of stay (LOS) (2.1 days vs 5.9 days, P < .01) and increased rate of readmission within 30 days of discharge (17% vs 14%, P < .05). However, repeat analysis after removing ventilator-dependent patients at discharge (n = 202) showed no difference in rates of readmission (14% vs 14%, P = .88). Conclusions: Direct discharge home from the PICU is a common practice. DDH and ACD groups had similar 30-day readmission rate when patient admissions with home ventilator dependence were excluded

Sources of variation in Affymetrix microarray experiments

BACKGROUND: A typical microarray experiment has many sources of variation which can be attributed to biological and technical causes. Identifying sources of variation and assessing their magnitude, among other factors, are important for optimal experimental design. The objectives of this study were: (1) to estimate relative magnitudes of different sources of variation and (2) to evaluate agreement between biological and technical replicates. RESULTS: We performed a microarray experiment using a total of 24 Affymetrix GeneChip(® )arrays. The study included 4(th )mammary gland samples from eight 21-day-old Sprague Dawley CD female rats exposed to genistein (soy isoflavone). RNA samples from each rat were split to assess variation arising at labeling and hybridization steps. A general linear model was used to estimate variance components. Pearson correlations were computed to evaluate agreement between technical and biological replicates. CONCLUSION: The greatest source of variation was biological variation, followed by residual error, and finally variation due to labeling when *.cel files were processed with dChip and RMA image processing algorithms. When MAS 5.0 or GCRMA-EB were used, the greatest source of variation was residual error, followed by biology and labeling. Correlations between technical replicates were consistently higher than between biological replicates