170,054 research outputs found
Late Neogene changes in North America and Antarctica absolute plate motions inferred from the Mid-Atlantic and Southwest Indian Ridges spreading histories
No full textHigh-resolution Neogene and Quaternary estimates of Nubia-Eurasia-North America Plate motion
No full textReconstructions of the history of convergence between the Nubia and Eurasia plates constitute an important part of a broader framework for understanding deformation in the Mediterranean region and the closing of the Mediterranean Basin. Herein, we combine high-resolution reconstructions of Eurasia-North America and Nubia-North America Plate motions to determine rotations that describe Nubia-Eurasia Plate motion at ~1 Myr intervals for the past 20 Myr. We apply trans-dimensional hierarchical Bayesian inference to the Eurasia-North America and Nubia-North America rotation sequences in order to reduce noise in the newly estimated Nubia-Eurasia rotations. The noise-reduced rotation sequences for the Eurasia-North America and Nubia-North America Plate pairs describe remarkably similar kinematic histories since 20 Ma, consisting of relatively steady seafloor spreading from 20 to 8 Ma, ~20 per cent opening-rate slowdowns at 8-6.5 Ma, and steady plate motion from ~7 Ma to the present. Our newly estimated Nubia-Eurasia rotations predict that convergence across the central Mediterranean Sea slowed by ~50 per cent and rotated anticlockwise after ~25 Ma until 13 Ma. Motion since 13 Ma has remained relatively steady. An absence of evidence for a significant change in motion immediately before or during the Messinian Salinity Crisis at 6.3-5.6 Ma argues against a change in plate motion as its causative factor. The detachment of the Arabian Peninsula from Africa at 30-24 Ma may have triggered the convergence rate slowdown before 13 Ma; however, published reconstructions of Nubia-Eurasia motion for times before 20 Ma are too widely spaced to determine with confidence whether the two are correlated. A significant discrepancy between our new estimates of Nubia-Eurasia motion during the past few Myr and geodetic estimates calls for further investigation
Indian Ocean floor deformation induced by the Reunion plume rather than the Tibetan Plateau
No full textDeformation of Mexico from continuous GPS from 1993 to 2008
No full textWe combine the velocities of 13 continuous Global Positioning System stations from Mexico and 448 North American plate stations to better understand deformation and earthquake cycle effects in Mexico. Velocities estimated at the Mexican sites from high-quality GPS data collected since 2003 show no evidence for a previously reported eastward bias at sites in and near the Yucatan peninsula. The new velocities are compared to the predictions of two models, one in which all motion in Mexico is attributed to North American plate motion and the second of which attributes site motions to a combination of plate motion and the elastic effects of frictional coupling along the Mexican subduction zone and faults in the Gulf of California. The second model fits the velocities within their estimated uncertainties. Mainland Mexico thus moves with the North American plate to within 1 mm per year and undergoes elastic interseismic deformation far into its interior. Two stations inland from the Guerrero and Oaxaca segments of the Mexican subduction zone have alternated between several-year-long periods of landward motion and several-month-long periods of trenchward motion frequently since 1993, consistent with previously described, repeating transient slip events along the subduction interface. The motions of two stations inland from the Rivera plate subduction zone are dominated by the coseismic and postseismic effects of the M = 8.0, 9 October 1995 Colima-Jalisco earthquake and M = 7.5, 22 January 2003 Tecoman earthquake offshore from western Mexico. © 2009 by the American Geophysical Union
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Decentralized discrete-time neural control for a Quanser 2-DOF helicopter
No full textWe combine the velocities of 13 continuous Global Positioning System stations from Mexico and 448 North American plate stations to better understand deformation and earthquake cycle effects in Mexico. Velocities estimated at the Mexican sites from high-quality GPS data collected since 2003 show no evidence for a previously reported eastward bias at sites in and near the Yucatan peninsula. The new velocities are compared to the predictions of two models, one in which all motion in Mexico is attributed to North American plate motion and the second of which attributes site motions to a combination of plate motion and the elastic effects of frictional coupling along the Mexican subduction zone and faults in the Gulf of California. The second model fits the velocities within their estimated uncertainties. Mainland Mexico thus moves with the North American plate to within 1 mm per year and undergoes elastic interseismic deformation far into its interior. Two stations inland from the Guerrero and Oaxaca segments of the Mexican subduction zone have alternated between several-year-long periods of landward motion and several-month-long periods of trenchward motion frequently since 1993, consistent with previously described, repeating transient slip events along the subduction interface. The motions of two stations inland from the Rivera plate subduction zone are dominated by the coseismic and postseismic effects of the M = 8.0, 9 October 1995 Colima-Jalisco earthquake and M = 7.5, 22 January 2003 Tecoman earthquake offshore from western Mexico. " 2009 by the American Geophysical Union.",,,,,,"10.1029/2008GC002278",,,"http://hdl.handle.net/20.500.12104/40507","http://www.scopus.com/inward/record.url?eid=2-s2.0-71949088269&partnerID=40&md5=a26a419c41e2174919a05ccc8d24663c",,,,,,"2",,"Geochemistry, Geophysics, Geosystems",,,,"10",,"Scopu
Mitomycin C in highly myopic eyes - Author reply
No full textOphthalmology. 2005 Feb;112(2):208-18; discussion 219.
Mitomycin C modulation of corneal wound healing after photorefractive keratectomy in highly myopic eyes.
Gambato C, Ghirlando A, Moretto E, Busato F, Midena E.
SourceRefractive Surgery Service and Antimetabolite Therapy Research Unit, Department of Ophthalmology, University of Padova, Padova, Italy.
Abstract
PURPOSE: To evaluate the role of topical mitomycin C in corneal wound healing (CWH) after photorefractive keratectomy (PRK) in highly myopic eyes.
DESIGN: Prospective, double-masked, randomized clinical trial.
PARTICIPANTS: Seventy-two eyes of 36 patients affected by high (>7 diopters) myopia.
METHODS: In each patient, one eye was randomly assigned to PRK with intraoperative topical 0.02% mitomycin C application, and the fellow eye was treated with a placebo. Postoperatively, mitomycin C-treated eyes received artificial tears (3 times daily, tapered in 3 months), whereas the fellow eye was treated with fluorometholone sodium 2% and artificial tears (3 times daily, tapered in 3 months).
MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), contrast sensitivity, manifest refraction, and biomicroscopy. Contrast sensitivity was determined using the Pelli-Robson chart. Corneal confocal microscopy documented CWH.
RESULTS: Mean follow-up was 18 months (range, 12-36). No side effects or toxic effects were documented. At 12-month follow-up examination, UCVAs (logarithm of the minimum angle of resolution) were 0.4+/-0.48 and 0.5+/-0.53 (P = .03) in mitomycin C-treated eyes and corticosteroid-treated eyes, respectively. At 1 year, corneal haze developed in 20% of corticosteroid-treated eyes, versus 0% of mitomycin C-treated eyes. At 12, 24, and 36 months, corneal confocal microscopy showed activated keratocytes and extracellular matrix significantly more evident in untreated eyes (Ps = 0.004, 0.024, and 0.046, respectively).
CONCLUSION: Topical intraoperative application of 0.02% mitomycin C can reduce haze formation in highly myopic eyes undergoing PRK.
Comment in
Ophthalmology. 2006 Feb;113(2):357; author reply 357-8
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Strong interseismic coupling, fault afterslip, and viscoelastic flow before and after the Oct. 9, 1995 Colima-Jalisco earthquake: Continuous GPS measurements from Colima, Mexico
No full textContinuous GPS measurements from Colima, Mexico during 4/93-6/01, bracketing the Oct. 9, 1995 M = 8.0 Colima-Jalisco earthquake, provide new constraints on Rivera plate subduction mechanics. Modeling of margin-normal strain accumulation before the earthquake suggests the Rivera-North America subduction interface was fully locked. Transient postseismic motion from 10/ 95-6/97 is well fit by a model that includes logarithmically-decaying fault afterslip, elastic strain from shallow fault relocking, and possibly a minor viscoelastic response, but is fit poorly by models that assume a dominant Maxwell viscoelastic response of the lower crust and upper mantle, independent of the assumed viscosities. Landward, margin-normal motion since mid-1997 is parallel to but ? 75% slower than the pre-seismic velocity. Afterslip alone fails to account for this slowdown. The viscoelastic response predicted by a FEM correctly resolves the remaining velocity difference within the uncertainties. Both processes thus offset elastic strain accumulating from the relocked subduction interface
Development of the scintillating fiber timing detector for the MU3E experiment
No full textWe present the development and discuss the performance of a compact scintillating fiber detector for the Mu3e experiment for accurate time measurements at very high particle rates. Mu3e is a new experiment under preparation at the Paul Scherrer Institut (PSI) to search for charged Lepton Flavor Violation in the neutrinoless muon decay u(+)-> e(+)e(-)e(+) with a projected sensitivity of 10(-16) using the most intense continuous surface muon beam in the world. A very thin scintillating fiber detector (thickness <0.2% of a radiation length x(0)) with a time resolution of about 250 ps, efficiency around 97%, and spatial resolution of similar to 100(um) has been developed. The SciFi detector is read out with multi-channel silicon photomultiplier arrays at both ends to achieve the best timing performance. Different scintillating fiber types have been evaluated and various assembly procedures have been tested to achieve the best performance
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