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  • 1
    Electronic Resource
    Electronic Resource
    Differentiation of meso isomers from racemic mixtures with the combined use of chiral shift reagents and two-dimensional heteronuclear correlation NMR spectroscopy (1995)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. 905-908 
    Details
    ISSN: 0749-1581
    Keywords: NMR ; 1H NMR ; chiral shift reagents ; meso isomers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the presence of chiral shift reagents the enantiotopic nuclei of a pair of enantiomers become diastereotopic and have the potential to give resolved NMR signals. Similarly, the enantiotopic nuclei within a meso isomer become diastereotopic in the presence of a chiral shift reagent and may give resolved NMR signals. However, the diastereotopic nuclei of a meso isomer mixed with a chiral shift reagent, unlike those of a racemic mixture, are located in the same molecule. Their intramolecular character can be established experimentally by detection of spin-spin splitting between them or to a common third nucleus. Comparison of the correlation peaks in a two-dimensional, heteronuclear, multiple-quantum correlation (HMQC) spectrum with those of a heteronuclear multiple-bond correlation (HMBC) spectrum is an effective means of detection of coupling to a third nucleus. Two-dimensional NMR spectroscopy was used to identify the meso form of di-(trans-2-aminocyclohexyl)amine.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260331112
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    Paper (German National Licenses)
    Fulltext
  • 2
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    Suppression of interferon-mediated antiviral immunity by hepatitis B virus: an overview of research progress (2013)
    Wiley-Blackwell
    Details
    Publication Date: 2013-06-25
    Description: Interferon (IFN)-α is an indispensable drug for hepatitis B treatment in clinical settings. However, hepatitis B virus (HBV) can attenuate IFN-mediated antiviral responses to avoid being inhibited or cleared. Much progress has been made in exploring how the IFN-induced anti-HBV effect is inhibited. This review examines and summarises new advances regarding the molecular mechanism underlying the HBV-induced suppression of type I IFN-mediated antiviral immunity. This article is protected by copyright. All rights reserved.
    Print ISSN: 0300-9475
    Electronic ISSN: 1365-3083
    Topics: Medicine
    Published by Wiley-Blackwell
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  • 3
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    Virial expansion of a harmonically trapped Fermi gas across a narrow Feshbach resonance (2014)
    American Physical Society (APS)
    Details
    Publication Date: 2014-01-07
    Description: Author(s): Shi-Guo Peng, Shuo-Han Zhao, and Kaijun Jiang We theoretically investigate the high-temperature thermodynamics of a harmonically trapped Fermi gas across a narrow Feshbach resonance by using the second-order quantum virial expansion, and point out some new features compared to the broad resonance. The interatomic interaction is modeled by the p... [Phys. Rev. A 89, 013603] Published Mon Jan 06, 2014
    Keywords: Matter waves and collective properties of cold atoms and molecules
    Print ISSN: 1050-2947
    Electronic ISSN: 1094-1622
    Topics: Physics
    Published by American Physical Society (APS)
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  • 4
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    In situ lower crustal accretion by melt sill injection revealed by seismic layering (2021)
    In:  (Submitted) Research Square Preprints .
    Details
    Publication Date: 2021-11-24
    Description: Oceanic crust is formed at mid-ocean spreading centres by a combination of magmatic, tectonic and hydrothermal processes. The crust formed by magmatic process consists of an upper crust generally composed of basaltic dikes and lava flows and a lower crust presumed to mainly contain homogeneous gabbro whereas that by tectonic process can be very heterogeneous and may even contain mantle rocks. Although the formation and evolution of the upper crust are well known from geophysical and drilling results, those for the lower crust remain a matter of debate. Using a full waveform inversion method applied to wide-angle seismic data, here we report the presence of layering in the lower oceanic crust formed at the slow spreading Mid-Atlantic Ridge, ~7-12 Ma in age, revealing that the lower crust is formed mainly by in situ cooling and crystallisation of melt sills at different depths by the injection of magma from the mantle. These layers are 400-600 m thick with alternate high and low velocities, with ± 100-200 m/s velocity variation, and cover over a million-year old crust, suggesting that the crustal accretion by melt sill intrusions beneath the ridge axis is a stable process. We also find that the upper crust is ~400 m thinner than that from conventional travel-time analysis. Taken together, these discoveries suggest that the magmatism plays more important roles in the crustal accretion process at slow spreading ridges than previously realised, and that in-situ lower crustal accretion is the main process for the formation of lower oceanic crust.
    Type: Article , NonPeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: text
    DOI: 10.21203/rs.3.rs-145281/v1
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    OceanRep: Article in a Scientific Journal - without review
  • 5
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    Lower oceanic crust formed by in situ melt crystallization revealed by seismic layering (2022)
    Nature Research
    Details
    Publication Date: 2024-02-07
    Description: Oceanic crust forms at mid-ocean spreading centres through a combination of magmatic and tectonic processes, with the magmatic processes creating two distinct layers: the upper and the lower crust. While the upper crust is known to form from lava flows and basaltic dykes based on geophysical and drilling results, the formation of the gabbroic lower crust is still debated. Here we perform a full waveform inversion of wide-angle seismic data from relatively young (7–12-Myr-old) crust formed at the slow-spreading Mid-Atlantic Ridge. The seismic velocity model reveals alternating, 400–500 m thick, high- and low-velocity layers with ±200 m s−1 velocity variations, below ~2 km from the oceanic basement. The uppermost low-velocity layer is consistent with hydrothermal alteration, defining the base of extensive hydrothermal circulation near the ridge axis. The underlying layering supports that the lower crust is formed through the intrusion of melt as sills at different depths, which cool and crystallize in situ. The layering extends up to 5–15 km distance along the seismic profile, covering 300,000–800,000 years, suggesting that this form of lower crustal accretion is a stable process.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Non-linear full waveform inversion of wide-aperture OBS data for Moho structure using a trans-dimensional Bayesian method (2021)
    Oxford University Press
    Details
    Publication Date: 2024-02-07
    Description: Seismic full waveform inversion (FWI) is a powerful method for estimating quantitative subsurface physical parameters from seismic data. As the full waveform inversion is a non-linear problem, the linearized approach updates model iteratively from an initial model, which can get trapped in local minima. In the presence of a high velocity contrast, such as at Moho, the reflection coefficient and recorded waveforms from wide-aperture seismic acquisition are extremely non-linear around critical angles. The problem at the Moho is further complicated by the interference of lower crustal (Pg) and upper mantle (Pn) turning ray arrivals with the critically reflected Moho arrivals (PmP). In order to determine velocity structure near Moho, a non-linear method should be used. We propose to solve this strong non-linear FWI problem at Moho using a trans-dimensional Markov chain Monte Carlo (MCMC) method, where the earth model between lower crust and upper mantle is idealy parameterized with a 1-D assumption using a variable number of velocity interfaces. Different from common MCMC methods that require determining the number of unknown as a fixed prior before inversion, trans-dimensional MCMC allows the flexibility for an automatic estimation of both the model complexity (e.g. the number of velocity interfaces) and the velocity-depth structure from the data. We first test the algorithm on synthetic data using four representative Moho models and then apply to an ocean bottom seismometer (OBS) data from the Mid-Atlantic Ocean. A 2-D finite-difference solution of an acoustic wave equation is used for data simulation at each iteration of MCMC search, for taking into account the lateral heterogeneities in the upper crust, which is constrained from travel time tomography and is kept unchanged during inversion; the 1-D model parameterization near Moho enables an efficient search of the trans-dimensional model space. Inversion results indicate that, with very little prior and the wide-aperture seismograms, the trans-dimensional FWI method is able to infer the posterior distribution of both the number of velocity interfaces and the velocity-depth model for a strong nonlinear problem, making the inversion a complete data-driven process. The distribution of interface matches the velocity discontinuities. We find that the Moho in the study area is a transition zone of 0.7 km, or a sharp boundary with velocities from around 7 km/s in the lower crust to 8 km/s of the upper mantle; both provide nearly identical waveform match for the field data. The ambiguity comes from the resolution limit of the band-limited seismic data and limited offset range for PmP arrivals.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    The detection of Pb2+ in solution using bare magnetoelastic resonator (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-02-02
    Description: In this paper, a simple and low cost method for determination of Pb 2+ in solution, using bare Metglas alloy 2826MB as the resonator, is reported. Based on the replacement reaction mechanism of the Pb 2+ in the solution with Fe and Ni in the Metglas 2826MB ribbon surface, the Pb replaced on the resonator can increase the mass load of the resonator and decrease the resonant frequency of the resonator. Hence, the Pb 2+ concentration in solution can be determined by the resonant frequency shift of the ME resonator. The Energy Dispersive Spectrometer results of Pb, Fe, and Ni contents on the resonator's surface prove the reliability of this method. Furthermore, the experimental results show that the resonant frequency shift rate of the resonator decreases when the Pb 2+ concentration declines. The sensitivity of the resonator for Pb 2+ detection is greatly related to its dimension. The resonator with smaller size has a better sensitivity. The resonant frequency shift of the resonator with dimension of 3 mm × 6 mm × 30  μ m is linearly proportional to the Pb 2+ concentration. The sensitivity of the resonator for Pb(NO 3 ) 2 detection is about 24 Hz / mg   ml − 1 , and the resonator has a better stability and reproducibility for Pb 2+ detection with low concentration.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 8
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    Enantioselective Synthesis of Spirobarbiturate-Cyclohexenes through Phosphine-Catalyzed Asymmetric [4 + 2] Annulation of Barbiturate-Derived Alkenes with Allenoates (2016)
    American Chemical Society (ACS)
    Details
    Publication Date: 2016-03-04
    Description: Organic Letters DOI: 10.1021/acs.orglett.6b00239
    Print ISSN: 1523-7060
    Electronic ISSN: 1523-7052
    Topics: Chemistry and Pharmacology
    Published by American Chemical Society (ACS)
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  • 9
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    Demonstration of interferometric atom-pattern engineering via Rabi oscillations (2016)
    American Physical Society (APS)
    Details
    Publication Date: 2016-03-23
    Description: Author(s): Jun Rui, Yan Jiang, Guo-Peng Lu, Min-Jie Zhu, Bo Zhao, Xiao-Hui Bao, and Jian-Wei Pan We report an experimental demonstration of atom-pattern engineering via Rabi oscillations. We make use of interferometric Raman beams to drive a microwave transition for laser-cooled atoms confined within an optical dipole trap. Up to nine fringes are patterned within a half wavelength of the Raman … [Phys. Rev. A 93, 033837] Published Tue Mar 22, 2016
    Keywords: Quantum optics, physics of lasers, nonlinear optics, classical optics
    Print ISSN: 1050-2947
    Electronic ISSN: 1094-1622
    Topics: Physics
    Published by American Physical Society (APS)
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  • 10
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    pH-Directed Synthesis of Two Luminescent Zinc(II) Coordination Compounds based on 5-Aminotetrazole-1-propanoic Acid (2016)
    Wiley-Blackwell
    Details
    Publication Date: 2016-08-17
    Description: Two Zn II -tetrazole-carboxylate coordination compounds are reported, mononuclear [Zn(atzpa) 2 (H 2 O) 4 ] · 2H 2 O ( 1 ) and one-dimensional [Zn(atzpa) 2 (H 2 O) 2 ] n ( 2 ), derived from 5-aminotetrazole-1-propanoic acid (Hatzpa). The structures of both compounds are determined by the pH value of the reaction system. The luminescence properties of Hatzpa and the compounds were investigated at room temperature in the solid state. Furthermore, differential scanning calorimetry (DSC) and thermogravimetric-differential thermogravimetric (TG-DTG) analyses were applied to evaluate the thermal decomposition behavior of such compounds. The relevant thermodynamic parameters (Δ H , Δ S , and Δ G ) of the decompostion process of compound 1 were calculated, as well.
    Print ISSN: 0044-2313
    Electronic ISSN: 1521-3749
    Topics: Chemistry and Pharmacology
    Published by Wiley-Blackwell
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