Rapid virological surveillance of community influenza infection in general practice

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Geologic evolution of Iron Mountain, central Mojave Desert, California

This is the published version. Copyright 2010 American Geophysical Union. All Rights Reserved.Geologic mapping, structural analysis, petrologic study, and U-Pb geochronology at Iron Mountain, 20 km southwest of Barstow, California, place important constraints on the paleogeographic affinities of metasedimentary rocks in the area and provide new data to test Mesozoic and Cenozoic tectonic models for the central Mojave Desert. Rocks present at Iron Mountain include: Precambrian(?) and/or lower Paleozoic(?) miogeoclinal rocks, Middle Jurassic tonalite, Middle Jurassic Hodge volcanic series, Late Jurassic hornblende diorite, Cretaceous(?) peraluminous granite, and Cretaceous(?) granodiorite prophyry. Two phases of ductile deformation are present at Iron Mountain. The first phase, which penetratively deforms the miogeoclinal rocks, tonalite, and Hodge volcanic series, developed under amphibolite and greenschist facies metamorphic conditions. Fabric development in the Hodge volcanic series preceded emplacement of 151 ± 11 Ma granite. The second fabric deforms peraluminous granite and Late Jurassic hornblende diorite as well, and consists of spaced mylonitic shear zones. The shear zones predate emplacement of Late Cretaceous dikes (83 ± 1 Ma). The presence of probable miogeoclinal strata indicates that the boundary between allochthonous eugeoclinal rocks and parautochthonous miogeoclinal/cratonal rocks must lie north of Iron Mountain. The older amphibolite facies metamorphism and contractile deformation at Iron Mountain are interpreted to be part of a belt of Middle to Late Jurassic age deformation that runs northeastward through the Mojave Desert and forms the southern continuation of the east Sierran contractile belt. Newly recognized subvertical mylonitic shear zones of Cretaceous age at Iron Mountain have not been documented elsewhere in the central Mojave Desert. No significant Tertiary ductile deformation fabrics are present at Iron Mountain

StraboTools: A Mobile App for Quantifying Fabric in Geology

Quantification of field observations is an essential step in making them reproducible and shareable, but field geologists have few tools for quantifying field observations of important features such as foliation intensity, crystal alignment, vesicle elongation, joint intensity, and mineral proportions. Here we describe a mobile app, StraboTools, which offers two ways to rapidly and objectively quantify these variables. The edge fabric tool examines grayscale gradients in a photograph and summarizes them with the edge fabric ellipse. For deformation of a homogeneous material with passive markers, this ellipse tracks the strain ellipse. Edge fabric ellipses can be determined on the outcrop and make quick work (5 seconds) of formerly time-consuming and subjective strain-analysis tasks (e.g., Fry and Rf /Φ analysis). They are remarkably sensitive to subtle deformations that are difficult to see by eye. The color index tool determines the proportion of any component in the photograph whose grayscale level can be isolated (e.g., dark minerals in a granitic rock, feldspar phenocrysts in a lava, or blue epoxy in a thin section). Estimating proportions by eye has poor precision and accuracy; the color index tool is both accurate and precise if a suitable rock face is available. These tools can be used with photomicrographs and aerial photographs as well as in the field

Structure and evolution of the East Sierran thrust system, east central California

This is the published version. Copyright 1984 American Geophysical Union. All Rights Reserved.A belt of arc-parallel, northeast vergent contractional deformation, the East Sierran thrust system (ESTS), crops out for ∼150 km along the east side of the Sierran continental margin arc. The ESTS is nowhere wider than ∼20 km, and it accommodated an estimated minimum of ∼9.3 km of horizontal shortening. Remarkably, it experienced repeated episodes of broadly coaxial and coaxial-planar contractional deformation beginning prior to 188 Ma and continuing past 140 Ma. We postulate that the ESTS resulted primarily from episodic underthrusting of the back arc lithosphere beneath the east edge of the Sierran arc, facilitated by a buttressing effect of the arc. As a result of this process, rocks along the east flank of the batholith, including the ESTS, were episodically shortened against the arc buttress. The ESTS experienced significant deformation during the Nevadan orogeny, indicating that contractional to transpressive deformation affiliated with this event affected the eastern wall rocks of the arc as well as its western wall rocks

Petrologic constraints on the unroofing history of the Funeral Mountain Metamorphic Core Complex, California

This is the published version. Copyright 1990 American Geophysical Union. All Rights Reserved.Get PDF (1026K) Get at KU The northern Funeral Mountains, southeastern California, comprise a metamorphic core complex that lies within a region of extreme Neogene extension but did not experience a significant late Cenozoic thermal event. This circumstance, unusual among core complexes of the North American Cordillera, permits direct examination of the preextensional thermal evolution of a portion of the Cordilleran hinterland. For pelitic schists from the highest-grade portions of the Funeral metamorphic core, thermobarometry and thermodynamic modeling of garnet zonation define a P-T trajectory showing: (1) attainment of “peak” metamorphic conditions at 800–850 K and 800–1000 MPa (30–37 km depths); followed by (2) 400 to 600 MPa of decompression (15–22 km of exhumation) with no substantial change in temperature. Available geochronologic data indicate that peak metamorphism occurred in Early Cretaceous time and that the decompression path developed over the Early to Late Cretaceous interval. The maximum pressures indicated by the petrologic data require substantial Late Jurassic(?)-Early Cretaceous tectonic burial even though most recognized thrust faults at this latitude that have large stratigraphie throws are assumed or demonstrated to have early Mesozoic ages. We postulate that post-Early Cretaceous extensional faults may have excised the necessary middle Mesozoic thrust structures. While the majority of extensional structures responsible for this excisement is likely to be of Neogene age, associated with Basin and Range extension, the Cretaceous decompression path described in this paper is similar to the theoretical P-T paths derived from numerical modeling of extensional unroofing. Given recent evidence for the development of extensional structures in compressional regimes like the Himalayan and Alpine orogens, it seems prudent to search for evidence of Mesozoic extensional structures in future studies of the hinterland of the North American Cordillera

Variability in Bioavailable 87Sr/86Sr in the North American Midcontinent

Strontium (Sr) isotope tracers are useful for understanding provenance and mobility in biological materials across multiple disciplines. However, the impact of these techniques is highly dependent on the construction of appropriate comparative baselines (i.e., an isoscape). We present the results of a systematic survey of 87Sr/86Sr values from grasses in the North American Midcontinent with a particular emphasis on sedimentary systems. Although 87Sr/86Sr values are highly variable across the region, the Sr isoscape shows multi-scalar patterns that are dependent on local-to-regional trends in surficial geology. High values are found in bedrock-dominated areas such as the Black Hills (SD) and Ozark Uplift (MO), or formerly glaciated areas where surface deposits are dominated by ice-transported Precambrian clasts. The lowest values are found in river valleys that incorporate eroded Neogene sediments into terrace formation. Intermediate values are found in upland loess and alluvial deposits which blanket much of the study area. We demonstrate trends in large-scale variability of the Midcontinent’s 87Sr/86Sr isoscape and suggest that future refinement focus on sub-regional trends in Sr isotope variability

Do optometrists see 20/20? A survey of vision care utilized by optometrists: Implications for the profession

Purpose: The American Optometric Association\u27s Optometric Clinical Practice Guidelines identify appropriate utilization strategies for eye and vision examinations. Optometrists, like all health care providers, should follow the recommended standard of care as a doctor and as a patient. The purpose of this survey was to evaluate if optometrists seek and recommend the standard of vision care. Method: A survey was mailed to 650 randomly selected optometrists in the states of Oregon and Washington. The survey provided data describing the optometrists\u27 personal demographics, medical conditions, visual conditions, and utilization of vision care. Additional data included a survey of the optometrists\u27 recommendation of preventive eye care for their patients. Results: A 41% response rate was achieved from the mailing. In evaluating the data from optometrists who reported no ocular or medical conditions, the data show that 70% of the doctors surveyed, between the age of twenty and forty, have met the AOA guidelines recommendation of having a refraction, anterior segment exam, posterior segment exam, and intraocular pressure measurement within the recommended three year interval. Sixty-four percent of the doctors surveyed, between the age of forty-one and sixty, have met the AOA guidelines recommendation of having all of the procedures listed performed within the past two years. Of the doctors surveyed over the age of sixty, 36% have met the AOA guidelines of having all the procedures listed performed within the past year. With respect to preventive vision care for their patients, 90% of doctors, of all ages, reported that they recommend the AOA guidelines recommendation for their patients between the age of twenty and forty. Eighty-one percent of doctors, of all ages, reported recommending the AOA guidelines to their patients between the age of forty-one and sixty. Of those doctors surveyed, 30% of the respondents recommend the AOA guidelines to their patients over the age of sixty. Conclusion: Most optometrists\u27 personal eye care is consistent with the AOA Optometric Clinical Practice Guidelines. Most optometrists are recommending to their patients care intervals that are consistent with these guidelines. However, optometrists over the age of sixty are not seeking the standard of vision care recommended by the AOA guidelines and optometrists off all ages are not recommending the AOA guidelines to their patients over the age of sixty. It is recommended that all optometrists be educated as to the reason for the frequency of optometric examinations for themselves as well as for their patients over the age of sixty

Structural discordance between neogene detachments and frontal sevier thrusts, central Mormon Mountains, southern Nevada

This is the published version. Copyright 1985 American Geophysical Union. All Rights Reserved.Detailed geologic mapping in the Mormon Mountains of southern Nevada provides significant insight into processes of extensional tectonics developed within older compressional orogens. A newly discovered, WSW-directed low-angle normal fault, the Mormon Peak detachment, juxtaposes the highest levels of the frontal most part of the east-vergent, Mesozoic Sevier thrust belt with autochthonous crystalline basement. Palinspastic analysis suggests that the detachment initially dipped 20–25° to the west and cut discordantly across thrust faults. Nearly complete lateral removal of the hanging wall from the area has exposed a 5 km thick longitudinal cross-section through the thrust belt in the footwall, while highly attenuated remnants of the hanging wall (nowhere more than a few hundred meters thick) structurally veneer the range. The present arched configuration of the detachment resulted in part from progressive “domino-style” rotation of a few degrees while it was active, but is largely due to rotation on younger, structurally lower, basement-penetrating normal faults that initiated at high-angle. The geometry and kinematics of normal faulting in the Mormon Mountains suggest that pre-existing thrust planes are not required for the initiation of low-angle normal faults, and even where closely overlapped by extensional tectonism, need not function as a primary control of detachment geometry. Caution must thus be exercised in interpreting low-angle normal faults of uncertain tectonic heritage such as those seen in the COCORP west-central Utah and BIRP's MOIST deep-reflection profiles. Although thrust fault reactivation has reasonably been shown to be the origin of a very few low-angle normal faults, our results indicate that it may not be as fundamental a component of orogenic architecture as it is now widely perceived to be. We conclude that while in many instances thrust fault reactivation may be both a plausible and attractive hypothesis, it may never be assumed