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  • 1
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    Redefining the metamorphic history of the oldest rocks in the southern Rocky Mountains (2016)
    Geological Society of America (GSA)
    Details
    Publication Date: 2016-06-24
    Description: Proterozoic rocks exposed in the Rocky Mountains of New Mexico record the history of the assembly of North America, providing insight into crustal growth, accretion, and recycling. Here, we present six well-constrained Lu-Hf garnet ages showing that regional amphibolite-facies metamorphism and deformation occurred between 1.46 and 1.40 Ga. The samples come from the kyanite, sillimanite, and andalusite zones of the "Al 2 SiO 5 triple-point terrane" of northern New Mexico. Porphyroblast-matrix textures in dated samples provide definitive evidence for garnet growth during three phases of deformation associated with crustal thickening during the development of a regional-scale north-vergent contractional orogenic belt. The development of first-generation deformation fabrics is constrained to a period between 1.46 and ca. 1.45 Ga; second-generation deformation fabrics are constrained to the period 1.42–1.40 Ga; and third-generation fabrics were formed after ca. 1.40 Ga. Our results demonstrate that crustal-scale structures and regional metamorphism in northern New Mexico are both the result of a Mesoproterozoic orogenic event, the Picuris orogeny. We found no evidence for amphibolite-facies metamorphism during the Paleoproterozoic Mazatzal or Yavapai orogenies in northern New Mexico.
    Print ISSN: 0016-7606
    Electronic ISSN: 1943-2674
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 2
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    Modeling Site Amplification in Eastern Canada on a Regional Scale (2016)
    Seismological Society of America (SSA)
    Details
    Publication Date: 2016-06-25
    Description: A critical component in the interpretation of earthquake ground motions is the role that site effects play. In eastern Canada, the sediment layers which overlie glaciated bedrock produce strong and highly variable site responses. We use horizontal-to-vertical (H/V) response spectral ratios as the indicator variable by which to characterize the salient characteristics of site response. We show that site response can be modeled using two key descriptive variables that are readily obtainable: (1) peak frequency ( f peak ), as determined from H/V or sediment depth; and (2) overall sediment type (or stiffness). We use these variables to create a preliminary model of site amplification that can be used in the development of ground-motion prediction equations (GMPEs) and in regional-scale ShakeMap-type applications. The key to the site characterization is the relationship between f peak and sediment thickness (depth-to-bedrock), which we derive using H/V data from earthquakes in the region, combined with compiled geophysical logs and a digital sediment thickness map from the Ontario Geological Survey (OGS). The OGS map also provides information on surficial sediment type, which is correlated with peak amplitudes ( A peak ) of response. H/V spectral shapes may be associated with four main site categories, which in decreasing order of stiffness are: bedrock, till, sand/clay, and organic sediment/fill. The peak amplitudes of response are generally shown to increase as stiffness decreases, at least for the weak motions that are the focus of this study. We model site response by defining a generic site amplification curve, which is dependent only on f peak and site category. These site amplification curves can be applied in the development of regional GMPEs, and in the construction of near-real-time ShakeMaps.
    Print ISSN: 0895-0695
    Electronic ISSN: 1938-2057
    Topics: Geosciences
    Published by Seismological Society of America (SSA)
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  • 3
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    Remote Sensing, Vol. 11, Pages 1613: Optimal Cyanobacterial Pigment Retrieval from Ocean Colour Sensors in a Highly Turbid, Optically Complex Lake (2019)
    MDPI
    Details
    Publication Date: 2019
    Description: To date, several algorithms for the retrieval of cyanobacterial phycocyanin (PC) from ocean colour sensors have been presented for inland waters, all of which claim to be robust models. To address this, we conducted a comprehensive comparison to identify the optimal algorithm for retrieval of PC concentrations in the highly optically complex waters of Lake Balaton (Hungary). MEdium Resolution Imaging Spectrometer (MERIS) top-of-atmosphere radiances were first atmospherically corrected using the Self-Contained Atmospheric Parameters Estimation for MERIS data v.B2 (SCAPE-M_B2). Overall, the Simis05 semi-analytical algorithm outperformed more complex inversion algorithms, providing accurate estimates of PC up to ±7 days from the time of satellite overpass during summer cyanobacteria blooms (RMSElog 〈 0.33). Same-day retrieval of PC also showed good agreement with cyanobacteria biomass (R2 〉 0.66, p 〈 0.001). In-depth analysis of the Simis05 algorithm using in situ measurements of inherent optical properties (IOPs) revealed that the Simis05 model overestimated the phytoplankton absorption coefficient [aph(λ)] by a factor of ~2. However, these errors were compensated for by underestimation of the mass-specific chlorophyll absorption coefficient [a*chla(λ)]. This study reinforces the need for further validation of algorithms over a range of optical water types in the context of the recently launched Ocean Land Colour Instrument (OLCI) onboard Sentinel-3.
    Electronic ISSN: 2072-4292
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by MDPI
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  • 4
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    3D Nonlinear Ground‐Motion Simulation Using a Physics‐Based Method for the Kinburn Basin (2019)
    Seismological Society of America (SSA)
    Details
    Publication Date: 2019
    Description: 〈span〉〈div〉Abstract〈/div〉We used a finite‐difference modeling method, developed by Olsen–Day–Cui, to simulate nonlinear‐viscoelastic basin effects in a spectral frequency range of 0.1–1 Hz in the Kinburn bedrock topographic basin, Ottawa, Canada, for large earthquakes. The geotechnical and geological features of the study area are unique: loose, postglacial sediments with very low shear‐wave velocities (〈200  m/s) overlying very firm bedrock with high shear‐wave velocities (〉2000  m/s). Comparing records and simulated velocity time series showed regular viscoelastic simulations could model the ground motions at the rock and soil sites in the Kinburn basin for the Ladysmith earthquake, a local earthquake occurred on 17 May 2013 with Mw 4.7 (MN 5.2). The Ladysmith earthquake was scaled to provide a strong level of shaking for investigating the nonlinear behavior of soil; therefore, a new nonlinear‐viscoelastic subroutine was introduced to the program. A modeled stress–strain relationship associated with ground‐motion modeling in the Kinburn basin using a scaled Ladysmith earthquake event of Mw 7.5 followed Masing’s rules. Using nonlinear‐viscoelastic ground‐motion simulations significantly reduced the amplitude of the horizontal component of the Fourier spectrum at low frequencies and the predicted peak ground acceleration and peak ground velocity values compared with regular linear viscoelastic simulations; hence, the lower soil amplification of seismic waves and the frequency and amplitude spectral content were altered by the nonlinear soil behavior. In addition, using a finite‐fault model to simulate an earthquake with Mw 7.5 was necessary to predict the higher levels of stresses and strains, which were generated in the basin. Using a finite‐fault source for the nonlinear‐viscoelastic simulation caused decreases in the horizontal components because of the shear modulus reduction and increase of damping.〈/span〉
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
    Published by Seismological Society of America (SSA)
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  • 5
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    Does anthropogenic nitrogen deposition induce phosphorus limitation in herbivorous insects? (2012)
    Wiley
    Details
    Publication Date: 2012-04-15
    Description: Anthropogenic nitrogen deposition has shifted many ecosystems from nitrogen ( N ) limitation to phosphorus ( P ) limitation. Although well documented in plants, no study to date has explored whether N deposition exacerbates P limitation at higher trophic levels, or focused on the effects of induced plant P limitation on trophic interactions. Insect herbivores exhibit strict N  :  P homeostasis, and should therefore be very sensitive to variations in plant N  :  P stoichiometry and prone to experiencing deposition-induced P limitation. In the current study, we investigated the effects of N deposition and P availability on a plant-herbivorous insect system. Using common milkweed ( Asclepias syriaca ) and two of its specialist herbivores, the monarch caterpillar ( Danaus plexippus ) and milkweed aphid ( Aphis asclepiadis ) as our study system, we found that experimental N deposition caused P limitation in milkweed plants, but not in either insect species. However, the mechanisms for the lack of P limitation were different for each insect species. The body tissues of A. asclepiadis always exhibited higher N  :  P ratios than that of the host plant, suggesting that the N demand of this species exceeds P demand, even under high N deposition levels. For D. plexippus , P addition increased the production of latex, which is an important defense negatively affecting D. plexippus growth rate. As a result, we illustrate that P limitation of herbivores is not an inevitable consequence of anthropogenic N deposition in terrestrial systems. Rather, species-specific demands for nutrients and the defensive responses of plants combine to determine the responses of herbivores to P availability under N deposition.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Published by Wiley
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  • 6
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    Spatial variability of absorption coefficients over a biogeochemical gradient in a large and optically complex shallow lake (2015)
    Wiley
    Details
    Publication Date: 2015-10-09
    Description: In order to improve robustness of remote sensing algorithms for lakes, it is vital to understand the variability of inherent optical properties (IOPs) and their mass-specific representations (SIOPs). In this study, absorption coefficients for particulate and dissolved constituents were measured at 38 stations distributed over a biogeochemical gradient in Lake Balaton, Hungary. There was a large range of phytoplankton absorption ( a ph (λ)) over blue and red wavelengths ( a ph (440)=0.11-4.39 m −1 , a ph (675)=0.048-2.52 m −1 ), while there was less variability in chlorophyll-specific phytoplankton absorption ( a* ph (λ)) in the lake ( a* ph (440)=0.022±0.0046 m 2 mg −1 , a* ph (675)=0.010±0.0020 m 2 mg −1 ) and adjoining wetland system, Kis-Balaton ( a* ph (440)=0.017±0.0015 m 2 mg −1 , a* ph (675)=0.0088±0.0017 m 2 mg −1 ). However, in the UV, a* ph (350) significantly increased with increasing distance from the main inflow (River Zala). This was likely due to variable production of photoprotective pigments (e.g. MAAs) in response to the decreasing gradient of colored dissolved organic matter (CDOM). The slope of CDOM absorption ( S CDOM ) also increased from west to east due to larger terrestrial CDOM input in the western basins. Absorption by non-algal particles ( a NAP (λ)) was highly influenced by inorganic particulates, as a result of the largely mineral sediments in Balaton. The relative contributions to the absorption budget varied more widely than oceans with a greater contribution from NAP (up to 30%), and wind speed affected the proportion attributed to NAP, phytoplankton or CDOM. Ultimately, these data provide knowledge of the heterogeneity of (S)IOPs in Lake Balaton, suggesting the full range of variability must be considered for future improvement of analytical algorithms for constituent retrieval in inland waters. This article is protected by copyright. All rights reserved.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
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    Hydrogeological insights from groundwater level hydrographs in SE Ireland (2012)
    Geological Society of London
    Details
    Publication Date: 2012-02-01
    Description: Analysis of groundwater level records from Ireland’s South Eastern River Basin District (SERBD) allowed fundamental information about the nature of bedrock and gravel aquifers to be investigated. The hydrogeological setting of a monitoring point (with respect to, for example, recharge area, discharge area or proximity to a river) is the dominant factor influencing hydrograph character in bedrock aquifers, with aquifer type and subsoil properties producing secondary effects. Analysis of seasonal groundwater levels showed that the fractured bedrock aquifers recharge more quickly and typically have a longer recession period than gravel aquifers. The calculated recession periods for bedrock aquifers are longer than previous estimates for similar aquifers. Hydrograph analysis identified a number of notable phenomena including a gravel aquifer’s interaction with surface water and evidence of rejected recharge. Short-term groundwater level fluctuations caused by global seismic events, recorded via chart recorders, are discussed. Specific yield values were calculated, for a number of settings, from annual average groundwater level variations. The values supported estimates from previous research on similar aquifers. An analysis to investigate if any impacts of climate change were evident showed no consistent change in the timing of groundwater level minima or maxima.
    Print ISSN: 1470-9236
    Topics: Geosciences
    Published by Geological Society of London
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  • 8
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    MicroRNA-155 as a proinflammatory regulator in clinical and experimental arthritis [Medical Sciences] (2011)
    National Academy of Sciences
    Details
    Publication Date: 2011-07-06
    Description: MicroRNA (miRNA) species (miR) regulate mRNA translation and are implicated as mediators of disease pathology via coordinated regulation of molecular effector pathways. Unraveling miR disease-related activities will facilitate future therapeutic interventions. miR-155 recently has been identified with critical immune regulatory functions. Although detected in articular tissues, the functional role of miR-155 in inflammatory arthritis has not been defined. We report here that miR-155 is up-regulated in synovial membrane and synovial fluid (SF) macrophages from patients with rheumatoid arthritis (RA). The increased expression of miR-155 in SF CD14+ cells was associated with lower expression of the miR-155 target, Src homology 2-containing inositol phosphatase-1 (SHIP-1), an inhibitor of inflammation. Similarly, SHIP-1 expression was decreased in CD68+ cells in the synovial lining layer in RA patients as compared with osteoarthritis patients. Overexpression of miR-155 in PB CD14+ cells led to down-regulation of SHIP-1 and an increase in the production of proinflammatory cytokines. Conversely, inhibition of miR-155 in RA synovial CD14+ cells reduced TNF-α production. Finally, miR-155–deficient mice are resistant to collagen-induced arthritis, with profound suppression of antigen-specific Th17 cell and autoantibody responses and markedly reduced articular inflammation. Our data therefore identify a role of miR-155 in clinical and experimental arthritis and suggest that miR-155 may be an intriguing therapeutic target.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 9
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    3D Nonlinear Ground‐Motion Simulation Using a Physics‐Based Method for the Kinburn Basin (2019)
    Seismological Society of America (SSA)
    Details
    Publication Date: 2019
    Description: 〈span〉〈div〉Abstract〈/div〉We used a finite‐difference modeling method, developed by Olsen–Day–Cui, to simulate nonlinear‐viscoelastic basin effects in a spectral frequency range of 0.1–1 Hz in the Kinburn bedrock topographic basin, Ottawa, Canada, for large earthquakes. The geotechnical and geological features of the study area are unique: loose, postglacial sediments with very low shear‐wave velocities (〈200  m/s) overlying very firm bedrock with high shear‐wave velocities (〉2000  m/s). Comparing records and simulated velocity time series showed regular viscoelastic simulations could model the ground motions at the rock and soil sites in the Kinburn basin for the Ladysmith earthquake, a local earthquake occurred on 17 May 2013 with Mw 4.7 (MN 5.2). The Ladysmith earthquake was scaled to provide a strong level of shaking for investigating the nonlinear behavior of soil; therefore, a new nonlinear‐viscoelastic subroutine was introduced to the program. A modeled stress–strain relationship associated with ground‐motion modeling in the Kinburn basin using a scaled Ladysmith earthquake event of Mw 7.5 followed Masing’s rules. Using nonlinear‐viscoelastic ground‐motion simulations significantly reduced the amplitude of the horizontal component of the Fourier spectrum at low frequencies and the predicted peak ground acceleration and peak ground velocity values compared with regular linear viscoelastic simulations; hence, the lower soil amplification of seismic waves and the frequency and amplitude spectral content were altered by the nonlinear soil behavior. In addition, using a finite‐fault model to simulate an earthquake with Mw 7.5 was necessary to predict the higher levels of stresses and strains, which were generated in the basin. Using a finite‐fault source for the nonlinear‐viscoelastic simulation caused decreases in the horizontal components because of the shear modulus reduction and increase of damping.〈/span〉
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
    Published by Seismological Society of America (SSA)
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  • 10
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    Does anthropogenic nitrogen deposition induce phosphorus limitation in herbivorous insects? (2012)
    Wiley
    Details
    Publication Date: 2012-01-24
    Description: Anthropogenic nitrogen deposition has shifted many ecosystems from nitrogen (N) limitation to phosphorus (P) limitation. Although well documented in plants, no study to date has explored whether N deposition exacerbates P limitation at higher trophic levels, nor focused on the effects of induced plant P limitation on trophic interactions. Insect herbivores exhibit strict N: P homeostasis, and should therefore be very sensitive to variations in plant N: P stoichiometry and prone to experiencing deposition-induced P limitation. In the current study, we investigated the effects of N deposition and P availability on a plant-herbivorous insect system. Using common milkweed ( Asclepias syriaca ) and two of its specialist herbivores, the monarch caterpillar ( Danaus plexippus ) and milkweed aphid ( Aphis asclepiadis ) as our study system, we found that experimental N deposition caused P limitation in milkweed plants but not in either insect species. However, the mechanisms for the lack of P limitation were different for each insect species. The body tissues of A. asclepiadis always exhibited higher N: P ratios than that of the host plant, suggesting that the N demand of this species exceeds P demand, even under high N deposition levels. For D. plexippus, P addition increased the production of latex, which is an important defense negatively affecting D. plexippus growth rate. As a result, we illustrate that P limitation of herbivores is not an inevitable consequence of anthropogenic N deposition in terrestrial systems. Rather, species specific demands for nutrients and the defensive responses of plants combine to determine the responses of herbivores to P availability under N deposition.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Published by Wiley
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