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  • 1
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    Three-dimensional microlensing (2013)
    Oxford University Press
    Details
    Publication Date: 2013-12-18
    Description: We study three-dimensional microlensing where two lenses are located at different distances along the line of sight. We formulate the lens equation in complex notations and recover several previous results. There are in total either four or six images, with an equal number of images with positive and negative parities. We find that the sum of signed magnifications for six-image configurations is unity. Furthermore, we show that the light curves can be qualitatively different from those for binary lensing in a single plane. In particular, the magnifications between a ‘U’-shaped caustic crossing can be close to unity, rather than having a minimum magnification of 3 as in the single-plane binary lensing. There is only a small probability that three-dimensional microlensing events will be seen in microlensing towards the Galactic Centre. It is more likely that they will be first seen in cosmological microlensing.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 2
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    Synthesis and solid-state NMR structural characterization of 13C-labeled graphite oxide (2008)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2008-09-27
    Description: The detailed chemical structure of graphite oxide (GO), a layered material prepared from graphite almost 150 years ago and a precursor to chemically modified graphenes, has not been previously resolved because of the pseudo-random chemical functionalization of each layer, as well as variations in exact composition. Carbon-13 (13C) solid-state nuclear magnetic resonance (SSNMR) spectra of GO for natural abundance 13C have poor signal-to-noise ratios. Approximately 100% 13C-labeled graphite was made and converted to 13C-labeled GO, and 13C SSNMR was used to reveal details of the chemical bonding network, including the chemical groups and their connections. Carbon-13-labeled graphite can be used to prepare chemically modified graphenes for 13C SSNMR analysis with enhanced sensitivity and for fundamental studies of 13C-labeled graphite and graphene.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cai, Weiwei -- Piner, Richard D -- Stadermann, Frank J -- Park, Sungjin -- Shaibat, Medhat A -- Ishii, Yoshitaka -- Yang, Dongxing -- Velamakanni, Aruna -- An, Sung Jin -- Stoller, Meryl -- An, Jinho -- Chen, Dongmin -- Ruoff, Rodney S -- New York, N.Y. -- Science. 2008 Sep 26;321(5897):1815-7. doi: 10.1126/science.1162369.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Mechanical Engineering and the Texas Materials Institute, University of Texas at Austin, Austin, TX 78712, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18818353" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
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    A cellular automaton for the development of crustal shear zones (1996)
    In:  Tectonophys., Luxembourg, EGS-Gauthier-Villars, vol. 253, no. 2, pp. 247-270, pp. 2324
    Details
    Publication Date: 1996
    Keywords: Fault zone ; Statistical investigations ; Fracture
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    BIBLIOGRAPHY SEISMOLOGY
  • 4
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    Calcium Isotope Ratio (δ44/40Ca) Measurements of Ca‐Dominated Minerals and Rocks without Column Chemistry Using the Double‐Spike Technique and Thermal Ionisation Mass Spectrometry (2019)
    Wiley
    Details
    Publication Date: 2019
    Description: δ44/40Ca values for ten Ca‐rich minerals and rocks with chemistry and without matrix separation showed no difference within an intermediate measurement precision of ± 0.12‰. In this study, to evaluate whether bias free Ca isotope ratios can be properly achieved by thermal ionisation mass spectrometry (TIMS) using the 42Ca–43Ca double‐spike technique without chemical purification, a series of comparable experiments (with or without column chemistry) were made on Ca‐dominated minerals and rocks. Minerals, including fluorite, calcite, titanite and apatite, displayed similar Ca isotope ratios with Δ44/40Cawith‐without ranging from −0.02 to +0.07‰. For Ca‐rich rocks, we mainly focused on the carbonates since they are the main repositories of Ca at the surface of the Earth. Coral, stalagmite, carbonatite, dolomite, marble and limestone are studied here. Interestingly, δ44/40CaSRM 915a of these minerals and rocks without chemical purification displayed little drift compared with that of rocks with chemical purification, with Δ44/40Cawith‐without merely spanning from −0.04 to +0.04‰. This implies that Ca isotope ratios can be achieved without column chemistry, possibly due to a property of TIMS in which Ca ions are only ionised at a target temperature and with a specific activator without ionising other ions. Therefore, for Ca‐dominated minerals or rocks, we suggest that column chemistry is unnecessary if they are totally dissolved and mixed in proper proportion with the 42Ca–43Ca double spike for TIMS measurement.
    Print ISSN: 1639-4488
    Electronic ISSN: 1751-908X
    Topics: Geosciences
    Published by Wiley
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  • 5
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    Modulation of unidirectional anisotropy for Co-based amorphous ribbons by longitudinal pulse field (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-01-31
    Description: Field-induced unidirectional anisotropy of Co-based amorphous ribbons was discussed by magnetization measurement. The shifted hysteresis loops of Co 58 Fe 5 Ni 10 Si 11 B 16 amorphous ribbons were obtained by annealing the samples in longitudinal magnetic field. Here, the feasibility of employing the longitudinal pulse field to tailor the anisotropy characteristic is demonstrated. It is found that the shifted loops can be technically controlled by enhancing the pulse field to modulate the magnetic anisotropy from unidirectional to uniaxial, and even back to unidirectional. The surface domains scan gives strong evidence that the pulse field can be one of the skillful methods to navigate the unidirectional anisotropy in the amorphous ribbons for potential applications.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 6
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    The causality analysis of climate change and large-scale human crisis [Anthropology] (2011)
    National Academy of Sciences
    Details
    Publication Date: 2011-10-19
    Description: Recent studies have shown strong temporal correlations between past climate changes and societal crises. However, the specific causal mechanisms underlying this relation have not been addressed. We explored quantitative responses of 14 fine-grained agro-ecological, socioeconomic, and demographic variables to climate fluctuations from A.D. 1500–1800 in Europe. Results show that cooling from A.D. 1560–1660 caused successive agro-ecological, socioeconomic, and demographic catastrophes, leading to the General Crisis of the Seventeenth Century. We identified a set of causal linkages between climate change and human crisis. Using temperature data and climate-driven economic variables, we simulated the alternation of defined “golden” and “dark” ages in Europe and the Northern Hemisphere during the past millennium. Our findings indicate that climate change was the ultimate cause, and climate-driven economic downturn was the direct cause, of large-scale human crises in preindustrial Europe and the Northern Hemisphere.
    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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  • 7
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    Graded expression of zinc-responsive genes through two regulatory zinc-binding sites in Zur [Microbiology] (2011)
    National Academy of Sciences
    Details
    Publication Date: 2011-03-23
    Description: Zinc is one of the essential transition metals in cells. Excess or lack of zinc is detrimental, and cells exploit highly sensitive zinc-binding regulators to achieve homeostasis. In this article, we present a crystal structure of active Zur from Streptomyces coelicolor with three zinc-binding sites (C-, M-, and D-sites). Mutations of the three sites differentially affected sporulation and transcription of target genes, such that C- and M-site mutations inhibited sporulation and derepressed all target genes examined, whereas D-site mutations did not affect sporulation and derepressed only a sensitive gene. Biochemical and spectroscopic analyses of representative metal site mutants revealed that the C-site serves a structural role, whereas the M- and D-sites regulate DNA-binding activity as an on-off switch and a fine-tuner, respectively. Consistent with differential effect of mutations on target genes, zinc chelation by TPEN derepressed some genes (znuA, rpmF2) more sensitively than others (rpmG2, SCO7682) in vivo. Similar pattern of TPEN-sensitivity was observed for Zur-DNA complexes formed on different promoters in vitro. The sensitive promoters bound Zur with lower affinity than the less sensitive ones. EDTA-treated apo-Zur gained its DNA binding activity at different concentrations of added zinc for the two promoter groups, corresponding to free zinc concentrations of 4.5 × 10−16 M and 7.9 × 10−16 M for the less sensitive and sensitive promoters, respectively. The graded expression of target genes is a clever outcome of subtly modulating Zur-DNA binding affinities in response to zinc availability. It enables bacteria to detect metal depletion with improved sensitivity and optimize gene-expression pattern.
    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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  • 8
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    Monsoonal control on a delayed response of sedimentation to the 2008 Wenchuan earthquake (2019)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2019
    Description: 〈p〉Infrequent extreme events such as large earthquakes pose hazards and have lasting impacts on landscapes and biogeochemical cycles. Sediments provide valuable records of past events, but unambiguously identifying event deposits is challenging because of nonlinear sediment transport processes and poor age control. Here, we have been able to directly track the propagation of a tectonic signal into stratigraphy using reservoir sediments from before and after the 2008 Wenchuan earthquake. Cycles in magnetic susceptibility allow us to define a precise annual chronology and identify the timing and nature of the earthquake’s sedimentary record. The grain size and Rb/Sr ratio of the sediments responded immediately to the earthquake. However, the changes were muted until 2 years after the event, when intense monsoonal runoff drove accumulation of coarser grains and lower Rb/Sr sediments. The delayed response provides insight into how climatic and tectonic agents interact to control sediment transfer and depositional processes.〈/p〉
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 9
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    Calcium Isotope Ratio (δ44/40Ca) Measurements of Ca‐Dominated Minerals and Rocks without Column Chemistry Using the Double‐Spike Technique and Thermal Ionisation Mass Spectrometry (2019)
    Wiley
    Details
    Publication Date: 2019
    Description: δ44/40Ca values for ten Ca‐rich minerals and rocks with chemistry and without matrix separation showed no difference within an intermediate measurement precision of ± 0.12‰. In this study, to evaluate whether bias free Ca isotope ratios can be properly achieved by thermal ionisation mass spectrometry (TIMS) using the 42Ca–43Ca double‐spike technique without chemical purification, a series of comparable experiments (with or without column chemistry) were made on Ca‐dominated minerals and rocks. Minerals, including fluorite, calcite, titanite and apatite, displayed similar Ca isotope ratios with Δ44/40Cawith‐without ranging from −0.02 to +0.07‰. For Ca‐rich rocks, we mainly focused on the carbonates since they are the main repositories of Ca at the surface of the Earth. Coral, stalagmite, carbonatite, dolomite, marble and limestone are studied here. Interestingly, δ44/40CaSRM 915a of these minerals and rocks without chemical purification displayed little drift compared with that of rocks with chemical purification, with Δ44/40Cawith‐without merely spanning from −0.04 to +0.04‰. This implies that Ca isotope ratios can be achieved without column chemistry, possibly due to a property of TIMS in which Ca ions are only ionised at a target temperature and with a specific activator without ionising other ions. Therefore, for Ca‐dominated minerals or rocks, we suggest that column chemistry is unnecessary if they are totally dissolved and mixed in proper proportion with the 42Ca–43Ca double spike for TIMS measurement.
    Print ISSN: 1639-4488
    Electronic ISSN: 1751-908X
    Topics: Geosciences
    Published by Wiley
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  • 10
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    The LEF1/CYLD axis and cIAPs regulate RIP1 deubiquitination and trigger apoptosis in selenite-treated colorectal cancer cells (2014)
    Springer Nature
    Details
    Publication Date: 2014-02-28
    Description: The LEF1/CYLD axis and cIAPs regulate RIP1 deubiquitination and trigger apoptosis in selenite-treated colorectal cancer cells Cell Death and Disease 5, e1085 (February 2014). doi:10.1038/cddis.2014.13 Authors: P Wu, K J Shi, J J An, Y L Ci, F Li, K Y Hui, Y Yang & C M Xu
    Keywords: apoptosisRIP1cIAPsLEF1/CYLDselenite
    Electronic ISSN: 2041-4889
    Topics: Biology , Medicine
    Published by Springer Nature
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