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  • 1
    Publication Date: 2019
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2016-05-24
    Description: Gold mineralization at the Ballarat East deposit, central Victoria, Australia, is hosted in lodes that are historically known as "leather jackets." These are quartz-dominant vein arrays related to low-displacement, W-dipping faults (≤45°) that transect the core and/or eastern limb of tight, asymmetric N-S-trending anticlines. The leather jacket lodes typically have dip extents from 5 to 65 m, widths of ≤20 m, and strike lengths up to hundreds of meters, but their along-strike continuity is disrupted by oblique, low-displacement listric faults known as "cross courses." The gold lodes are characterized by distinct phases of sulfide paragenesis with minor gold + arsenopyrite + pyrite defining the early sulfide stage. Late-stage coarse gold was precipitated with galena + sphalerite ± pyrrhotite ± chalcopyrite (late pyrite also occurs). The gold mineralization events are linked to low-strain mineralized fracture networks, which are closely related to the final deformation stages and the amplification of the major folds enclosing the lodes. This amplification produced domal fold culminations, with plunges ≤30°, and localized minor parasitic folds with shallower plunges (≤10°). A network of dilation sites, on the W-dipping faults, preferentially developed in the cores of anticlines, particularly in zones where there are changes in strike of bedding or fault bifurcation and refraction through contrasting sandstone and interbedded packages of sandstone and shale. Numerical three-dimensional simulations were undertaken to test our geologic observations and replicate conditions controlling the emplacement of the leather jacket lodes. Two different scenarios were investigated: first, to determine how changes in the local stress field orientation influences dilation and fluid infiltration; secondly, to test variations in fault geometry during the last stages of deformation—that is, within the final 2% of shortening, when most of the mineralized sites were created. Results show that strain and fluid flow localized along refracted sections of faults and around changes in dip, specifically on the shallower dipping sections within subvertical sandstone units. This is consistent with the observation that high-grade gold-bearing quartz is associated with localized changes in fault dip in thicker sandstone and sandstone-shale packages. There was also a component of strike-slip motion and near-field NW-to-SE or N-to-S stress fields, which can be attributed to the development of a component of out-of-plane motion during the development of fold culminations. The preferred model for the distribution of the high-grade auriferous vein arrays defining the leather jacket lodes is one of fold amplification and extension parallel to the fold axes, which produced an increasing out-of-plane relaxation. The main fluid conduits responsible for the leather jacket style of mineralization involve infiltration along steep bedding-parallel faults and veins that link up with the arrays of low-displacement W-dipping faults.
    Print ISSN: 0361-0128
    Topics: Geosciences
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  • 3
    Publication Date: 2013-01-09
    Description: A recent study of tigers in Chitwan, Nepal (1) stirred controversy by challenging the “source-sink” approach that underlies current global tiger conservation strategies (2). The observed lack of difference in tiger density estimates inside the protected area compared with a multiple-use area outside is offered as evidence. Based on this...
    Keywords: Letters
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 4
    Publication Date: 2017-12-09
    Description: Noninvasive light focusing deep inside living biological tissue has long been a goal in biomedical optics. However, the optical scattering of biological tissue prevents conventional optical systems from tightly focusing visible light beyond several hundred micrometers. The recently developed wavefront shaping technique time-reversed ultrasonically encoded (TRUE) focusing enables noninvasive light delivery to targeted locations beyond the optical diffusion limit. However, until now, TRUE focusing has only been demonstrated inside nonliving tissue samples. We present the first example of TRUE focusing in 2-mm-thick living brain tissue and demonstrate its application for optogenetic modulation of neural activity in 800-μm-thick acute mouse brain slices at a wavelength of 532 nm. We found that TRUE focusing enabled precise control of neuron firing and increased the spatial resolution of neuronal excitation fourfold when compared to conventional lens focusing. This work is an important step in the application of TRUE focusing for practical biomedical uses.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
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  • 5
    Publication Date: 2019
    Description: 〈p〉We explore the photo-induced kinetics of 1,3-cyclohexadiene upon excitation at 200 nm to the 3p state by ultrafast time-resolved, gas-phase x-ray scattering using the Linac Coherent Light Source. Analysis of the scattering anisotropy reveals that the excitation leads to the 3px and 3py Rydberg electronic states, which relax to the ground state with a time constant of 208 ± 11 fs. In contrast to the well-studied 266 nm excitation, at 200 nm the majority of the molecules (76 ± 3%) relax to vibrationally hot cyclohexadiene in the ground electronic state. A subsequent reaction on the ground electronic state surface leads from the hot cyclohexadiene to 1,3,5-hexatriene, with rates for the forward and backward reactions of 174 ± 13 and 355 ± 45 ps, respectively. The scattering pattern of the final hexatriene product reveals a thermal distribution of rotamers about the carbon-carbon single bonds.〈/p〉
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
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  • 6
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Tetrahedron 50 (1994), S. 12755-12772 
    ISSN: 0040-4020
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 7
    Publication Date: 2015-08-05
    Description: In the oligotrophic waters to the east of Madagascar a large phytoplankton bloom is found to occur in late austral summer. This bloom is composed of nitrogen fixers and can cover up to ∼1% of the world's ocean surface area. Satellite observations show that its spatial structure is closely tied to the underlying mesoscale eddy field in the region. The causes of the bloom and its temporal behavior (timing of its initiation and termination) and spatial variability are poorly understood, in part due to a lack of in situ observations. Here an eddy resolving 1/12˚ resolution ocean general circulation model and Lagrangian particle tracking are used to examine the hypothesis that iron from sediments around Madagascar could be advected east by the mesoscale eddy field to fertilize the bloom, and that variability in advection could explain the significant interannual variability in the spatial extent of the bloom. The model results suggest that this is indeed possible and furthermore imply that the bloom could be triggered by warming of the mixed layer, leading to optimal conditions for nitrogen fixers to grow, while its termination could be due to iron exhaustion. It is found that advection of Madagascan iron could re-supply the bloom region with this micronutrient in the period between the termination of one bloom and the initiation of the next in the following year. 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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  • 8
    Publication Date: 2016-06-21
    Description: Extraordinarily warm sea surface temperatures were present in the California Current System during 2014-2015. In several locations surface waters temperature registered new record high in the recent time series. This study focuses in the evolution of the warming in the southern part of the CCS, off the west coast of Baja California, Mexico. Analysis of monthly SST, sea level pressure and wind speed as measured by satellite from January 1988 to December 2015 show that recent warming occurred during two periods related to different processes. From May 2014 to April 2015, SST warming was related to weak coastal winds not associated to El Niño. During this period occurred the longest sustained period of 15 months of negative wind anomalies and strong negative sea level pressure in the series. A reduction of wind stress suggests a weakened coastal upwelling, and consequently cold water not transported into the surface. The second process of warming occurred from September to December 2015, during a strong El Niño condition.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 9
    Publication Date: 2013-06-08
    Description: The functions of RNAs, like proteins, are determined by their structures, which, in turn, are determined by their sequences. Comparison/alignment of RNA molecules provides an effective means to predict their functions and understand their evolutionary relationships. For RNA sequence alignment, most methods developed for protein and DNA sequence alignment can be directly applied. RNA 3-dimensional structure alignment, on the other hand, tends to be more difficult than protein structure alignment due to the lack of regular secondary structures as observed in proteins. Most of the existing RNA 3D structure alignment methods use only the backbone geometry and ignore the sequence information. Using both the sequence and backbone geometry information in RNA alignment may not only produce more accurate classification, but also deepen our understanding of the sequence–structure–function relationship of RNA molecules. In this study, we developed a new RNA alignment method based on elastic shape analysis (ESA). ESA treats RNA structures as three dimensional curves with sequence information encoded on additional dimensions so that the alignment can be performed in the joint sequence–structure space. The similarity between two RNA molecules is quantified by a formal distance, geodesic distance. Based on ESA, a rigorous mathematical framework can be built for RNA structure comparison. Means and covariances of full structures can be defined and computed, and probability distributions on spaces of such structures can be constructed for a group of RNAs. Our method was further applied to predict functions of RNA molecules and showed superior performance compared with previous methods when tested on benchmark datasets. The programs are available at http://stat.fsu.edu/ ~jinfeng/ESA.html.
    Keywords: Nucleic acid structure, RNA characterisation and manipulation, Computational Methods
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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  • 10
    Publication Date: 2013-06-08
    Description: Langmuir DOI: 10.1021/la400955c
    Print ISSN: 0743-7463
    Electronic ISSN: 1520-5827
    Topics: Chemistry and Pharmacology
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