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"Jones, Alan G"
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Captain America : promised land
The year is 2314, and the grandson of Steve Rogers lives in the utopian America Cap dreamed about. The legacy of Captain America has been realized, but sinister forces work to undo the dream! A family quest leads Jack Rogers into the bowels of the Earth, far from the idyllic surface, where a shocking discovery may shatter his utopian world! Jack is a wanted man on a desperate search for a cure to his son's fatal disease, and once it's found, a legend will be reborn!
Book
The crucial role of blue light as a driver of litter photodegradation in terrestrial ecosystems
Background and aimWherever sunlight reaches litter, there is potential for photodegradation to contribute to decomposition. Although recent studies have weighed the contribution of short wavelength visible and ultraviolet (UV) radiation as drivers of photodegradation, the relative importance of each spectral region across biomes and plant communities remains uncertain.MethodsWe performed a systematic meta-analysis of studies that assessed photodegradation through spectrally selective attenuation of solar radiation, by synthesizing 30 published studies using field incubations of leaf litter from 110 plant species under ambient sunlight.ResultsGlobally, the full spectrum of sunlight significantly increased litter mass loss by 15.3% ± 1% across all studies compared to darkness. Blue light alone was responsible for most of this increase in mass loss (13.8% ± 1%), whereas neither UV radiation nor its individual constituents UV-B and UV-A radiation had significant effects at the global scale, being only important in specific environments. These waveband-dependent effects were modulated by climate and ecosystem type. Among initial litter traits, carbon content, lignin content, lignin to nitrogen ratio and SLA positively correlated with the rate of photodegradation. Global coverage of biomes and spectral regions was uneven across the meta-analysis potentially biasing the results, but also indicating where research in lacking.ConclusionsAcross studies attenuating spectral regions of sunlight, our meta-analysis confirms that photodegradation is a significant driver of decomposition, but this effect is highly dependent on the spectral region considered. Blue light was the predominant driver of photodegradation across biomes rather than UV radiation.
Journal Article
Playing for keeps
\"A burnt-out soccer star tries to win back his family but gets distracted by his wandering eye in this romantic comedy starring Gerard Butler. His bank account drained and his libido fatigued, professional soccer player George (Butler) hangs up his cleats and heads back to Virginia. Determined to do right in the eyes of his ex-wife (Jessica Biel) and their lonely son (Noah Lomax), George takes a job coaching a local soccer team and begins working to form the young players into true athletes. But with every cougar in town eyeing him from the sidelines, George finds that staying focused on the job and keeping his prurient impulses in check are easier said than done\"--Allmovie.com, viewed September 6, 2018.
DVD
Solar UV-A radiation and blue light enhance tree leaf litter decomposition in a temperate forest
Sunlight can accelerate the decomposition process through an ensemble of direct and indirect processes known as photodegradation. Although photodegradation is widely studied in arid environments, there have been few studies in temperate regions. This experiment investigated how exposure to solar radiation, and specifically UV-B, UV-A, and blue light, affects leaf litter decomposition under a temperate forest canopy in France. For this purpose, we employed custom-made litterbags built using filters that attenuated different regions of the solar spectrum. Litter mass loss and carbon to nitrogen (C:N) ratio of three species: European ash (Fraxinus excelsior), European beech (Fagus sylvatica) and pedunculate oak (Quercus robur), differing in their leaf traits and decomposition rate, were analysed over a period of 7–10 months. Over the entire period, the effect of treatments attenuating blue light and solar UV radiation on leaf litter decomposition was similar to that of our dark treatment, where litter lost 20–30% less mass and had a lower C:N ratio than under the full-spectrum treatment. Moreover, decomposition was affected more by the filter treatment than mesh size, which controlled access by mesofauna. The effect of filter treatment differed among the three species and appeared to depend on litter quality (and especially C:N), producing the greatest effect in recalcitrant litter (F. sylvatica). Even under the reduced irradiance found in the understorey of a temperate forest, UV radiation and blue light remain important in accelerating surface litter decomposition.
Journal Article
Geophysical evidence for crustal and mantle weak zones controlling intra-plate seismicity - the 2017 Botswana earthquake sequence
Large earthquakes away from plate boundaries pose a significant threat to human lives and infrastructure, but such events typically occur on previously unknown faults. Most cases of intra-plate seismicity result from compression related to far-field plate boundary stresses. The April 2017 Mw 6.5 earthquake in central Botswana, and subsequent events, occurred in a region with no previously known large earthquakes, occurred away from major present day tectonic activity, and accommodate extension rather than compression. Here, we present results from an integrated geophysical study that suggests the recent earthquakes may be a sign of future activity, controlled by the collocation of a weak upper mantle and weak crustal structure, between otherwise strong Precambrian blocks. Magnetotelluric data highlights Proterozoic continent accretion structure within the region, and shows that recent extension and seismicity occurred along ancient thrust faults within the crust. Our seismic velocity and resistivity models suggest a weak zone in the uppermost mantle, that does not persist to greater depths, and is therefore unlikely to represent mantle upwelling. The Botswana events may therefore be indicative of top-down extension as a response to large scale extensional forces.
Paper
Electrical lithosphere beneath the Kaapvaal craton, southern Africa
A regional‐scale magnetotelluric (MT) experiment across the southern African Kaapvaal craton and surrounding terranes, called the Southern African Magnetotelluric Experiment (SAMTEX), has revealed complex structure in the lithospheric mantle. Large variations in maximum resistivity at depths to 200–250 km relate directly to age and tectonic provenance of surface structures. Within the central portions of the Kaapvaal craton are regions of resistive lithosphere about 230 km thick, in agreement with estimates from xenolith thermobarometry and seismic surface wave tomography, but thinner than inferred from seismic body wave tomography. The MT data are unable to discriminate between a completely dry or slightly “damp” (a few hundred parts per million of water) structure within the transitional region at the base of the lithosphere. However, the structure of the uppermost ∼150 km of lithosphere is consistent with enhanced, but still low, conductivities reported for hydrous olivine and orthopyroxene at levels of water reported for Kaapvaal xenoliths. The electrical lithosphere around the Kimberley and Premier diamond mines is thinner than the maximum craton thickness found between Kimberley and Johannesburg/Pretoria. The mantle beneath the Bushveld Complex is highly conducting at depths around 60 km. Possible explanations for these high conductivities include graphite or sulphide and/or iron metals associated with the Bushveld magmatic event. We suggest that one of these conductive phases (most likely melt‐related sulphides) could electrically connect iron‐rich garnets in a garnet‐rich eclogitic composition associated with a relict subduction slab. Key Points The electrical lithosphere beneath the Kaapvaal is ∼230 km thick Lithospheric structure is highly variable The Bushveld mantle is highly conductive
Journal Article
Water in cratonic lithosphere: Calibrating laboratory-determined models of electrical conductivity of mantle minerals using geophysical and petrological observations
Measurements of electrical conductivity of “slightly damp” mantle minerals from different laboratories are inconsistent, requiring geophysicists to make choices between them when interpreting their electrical observations. These choices lead to dramatically different conclusions about the amount of water in the mantle, resulting in conflicting conclusions regarding rheological conditions; this impacts on our understanding of mantle convection, among other processes. To attempt to reconcile these differences, we test the laboratory‐derived proton conduction models by choosing the simplest petrological scenario possible – cratonic lithosphere – from two locations in southern Africa where we have the most complete knowledge. We compare and contrast the models with field observations of electrical conductivity and of the amount of water in olivine and show that none of the models for proton conduction in olivine proposed by three laboratories are consistent with the field observations. We derive statistically model parameters of the general proton conduction equation that satisfy the observations. The pre‐exponent dry proton conduction term (σ0) and the activation enthalpy (ΔHwet) are derived with tight bounds, and are both within the broader 2σ errors of the different laboratory measurements. The two other terms used by the experimentalists, one to describe proton hopping (exponent ron pre‐exponent water contentCw) and the other to describe H2O concentration‐dependent activation enthalpy (termαCw1/3 added to the activation energy), are less well defined and further field geophysical and petrological observations are required, especially in regions of higher temperature and higher water content. Key Points Reconciles laboratory measurements with geophysical observations Suggests new model for water in olivine
Journal Article
Lithospheric geometry of the Wopmay orogen from a Slave craton to Bear Province magnetotelluric transect
Two‐dimensional inversions of lithospheric‐probing magnetotelluric (MT) data at a total of 20 sites acquired along an approximately east–west 300‐km‐long profile across the Wopmay orogen in the Northwest Territories, Canada, provide electrical resistivity models of the boundary between the Archean Slave craton and the adjacent Proterozoic Bear Province. An analysis of distortion effects and structural dimensionality indicates that the MT responses are primarily one‐dimensional or only weakly two‐dimensional with a depth‐independent geoelectric strike angle of N32°E, consistent with regional structural geology. The regional‐scale model, generated from the longer period responses from all of the sites along the profile, reveals significant lateral variations in the lithospheric mantle. Resistive cratonic roots are imaged to depths of ∼200 km beneath both the Slave craton and the Hottah terrane of the Bear Province. These are separated by a less resistive region beneath the Great Bear magmatic zone, which is speculatively interpreted as a consequence of a decrease in the grain size of olivine in the Wopmay mantle, caused by localized shearing, compared to its neighboring cratonic roots. Focused two‐dimensional models, from higher frequency responses at sites on specific sections of the profile, reveal the resistivity structure at crustal depths beneath the region. These suggest that the root of the Slave craton crosses beneath the Wopmay orogen, and that the Wopmay fault zone does not penetrate into the lower crust. A comparison of these results with those obtained during the Lithoprobe project farther south shows striking along strike variations in the conductivity structure associated with the Wopmay orogen.
Journal Article
Penetration of crustal melt beyond the Kunlun Fault into northern Tibet
The transition between the weak lithosphere of the Tibetan plateau and the surrounding rigid crustal blocks has a key role in the ongoing collision between India and Asia. A reanalysis of existing magnetotelluric data suggests that crustal melt penetrates north from the Tibetan plateau beyond the Kunlun Fault, and weakens the crust beneath the Kunlun Shan.
The weak lithosphere of the Tibetan plateau is surrounded by rigid crustal blocks
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and the transition between these regimes plays a key role in the ongoing collision between India and Eurasia. Geophysical data
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and magmatic evidence
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support the notion that partial melt exists within the anomalously hot
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crust of northern Tibet. The Kunlun Fault, which accommodates the plateau’s eastward extrusion, has been identified as a significant rheological boundary
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between weak, warm Tibetan crust
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and the rigid eastern Kunlun–Qaidam block. Here we present reanalyses and remodelling of existing magnetotelluric data
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, using an anisotropy code
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to obtain revised resistivity models. We find unequivocal evidence for anisotropy in conductivity at the northern edge of the Tibetan plateau. We interpret this anisotropy as the signature of intrusion of melt that penetrates north from the Tibetan plateau and weakens the crust beneath the Kunlun Shan. We suggest that our identification of a melt intrusion at the northern edge of the Tibetan plateau compromises the previous identification of the Kunlun Fault as an important rheological boundary. We conclude that the crustal melt penetration probably characterizes the growth of the plateau
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to the north, as well as accommodating the north–south crustal shortening in Tibet.
Journal Article