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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)
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  • 2
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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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  • 3
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    Manipulation of p-Wave Scattering of Cold Atoms in Low Dimensions Using the Magnetic Field Vector (2014)
    American Physical Society (APS)
    Details
    Publication Date: 2014-06-24
    Description: Author(s): Shi-Guo Peng, Shina Tan, and Kaijun Jiang It is well known that the magnetic Feshbach resonances of cold atoms are sensitive to the magnitude of the external magnetic field. Much less attention has been paid to the direction of such a field. In this work we calculate the scattering properties of spin polarized fermionic atoms in reduced dim... [Phys. Rev. Lett. 112, 250401] Published Mon Jun 23, 2014
    Keywords: General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society (APS)
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  • 4
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    Enantioselective Acute Toxicity Effects and Bioaccumulation of Furalaxyl in the Earthworm (Eisenia foetida) (2014)
    Wiley-Blackwell
    In: Chirality
    Details
    Publication Date: 2014-04-29
    Description: ABSTRACT The enantioselectivities of individual enantiomers of furalaxyl in acute toxicity and bioaccumulation in the earthworm ( Eisenia foetida ) were studied. The acute toxicity was tested by filter paper contact test. After 48 h of exposure, the calculated LC 50 values of the R -form, rac -form, and S -form were 2.27, 2.08, and 1.22 µg cm -2 , respectively. After 72 h of exposure, the calculated LC 50 values were 1.90, 1.54, and 1.00 µg cm -2 , respectively. Therefore, the acute toxicity of furalaxyl enantiomers was enantioselective . During the bioaccumulation experiment, the enantiomer fraction of furalaxyl in earthworm tissue was observed to deviate from 0.50 and maintained a range of 0.55–0.60; in other words, the bioaccumulation of furalaxyl was enantioselective in earthworm tissue with a preferential accumulation of S -furalaxyl. The uptake kinetic of furalaxyl enantiomers fitted the first-order kinetics well and the calculated kinetic parameters were consistent with the low accumulation efficiency. Chirality 00:000–000, 2014 . © 2014 Wiley Periodicals, Inc.
    Print ISSN: 0899-0042
    Electronic ISSN: 1520-636X
    Topics: Chemistry and Pharmacology
    Published by Wiley-Blackwell
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  • 5
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    Discharge characteristics of the DUHOCAMIS with a high magnetic bottle-shaped field (2014)
    Institute of Physics (IOP)
    Details
    Publication Date: 2014-10-22
    Description: For the purpose of producing high intensity, multiply charged metal ion beams, the dual hollow cathode ion source for metal ions (DUHOCAMIS) was derived from the hot cathode Penning ion source combined with the hollow cathode sputtering experiments in 2007. To investigate the behavior of this discharge geometry in a stronger magnetic bottle-shaped field, a new test bench for DUHOCAMIS with a high magnetic bottle-shaped field up to 0.6 T has been set up at the Peking University. The experiments with magnetic fields from 0.13 T to 0.52 T have indicated that the discharge behavior is very sensitive to the magnetic flux densities. The slope of discharge curves in a very wide range can be controlled by changing the magnetic field as well as regulated by adjusting the cathode heating power; the production of metallic ions would be much greater than gas ions with the increased magnetic flux density; and the magnetic field has a much higher influence on the DHCD mode than on the PIG mod...
    Print ISSN: 1674-1137
    Topics: Physics
    Published by Institute of Physics (IOP)
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  • 6
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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
  • 7
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    Uncertainty study of D − S (D − )→γlν̄(l = e, μ) decays determined by wave function (2011)
    Institute of Physics (IOP)
    Details
    Publication Date: 2011-07-27
    Description: Wave function is important for determining decay constants f D − S and f D − . Using the 5 types of D meson wave functions in the heavy quark limit, we studied the uncertainties of radiative pure-leptonic decays of D − S (D − ) mesons. The branching ratios are (1.025390−1.706812)×10 −5 and (0.953498−1.576725)×10 −6 for D − S and D − decays, respectively, which are sensitive to the type of wave function.
    Print ISSN: 1674-1137
    Topics: Physics
    Published by Institute of Physics (IOP)
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  • 8
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    Two Lanthanide-Organic Frameworks Derived from 1H-Benzimidazole-5-Carboxylic Acid and Oxalate Mixed Ligands: Synthesis, Structure and Luminescence Property (2011)
    Wiley-Blackwell
    Details
    Publication Date: 2011-08-17
    Description: Two novel lanthanide metal coordination frameworks were synthesized by reaction of 1 H -benzimidazole-5-carboxylic acid (H 2 bic) in the presence of the coligand oxalate with lanthanide ions under hydrothermal conditions, namely, [Eu(H 2 bic)(C 2 O 4 ) 1.5 ] · H 2 O ( 1 ) and [La(H 2 bic)(C 2 O 4 ) 1.5 ] · H 2 O ( 2 ). The two compounds 1 and 2 are isomorphous and have a 2D layer architecture built up by oxalate ligands interconnecting Eu 2 O 2 clusters, which are further linked by hydrogen bonding to form a 3D supramolecular framework. The luminescence emission spectrum of compound 1 is also discussed. Both compounds were further investigated by infrared spectroscopy (IR), thermogravimetric analysis (TGA), elemental analyses (EA), and powder X-ray diffraction (PXRD).
    Print ISSN: 0044-2313
    Electronic ISSN: 1521-3749
    Topics: Chemistry and Pharmacology
    Published by Wiley-Blackwell
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  • 9
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    Isospin effect in peripheral heavy-ion collisions at Fermi energies (2018)
    Institute of Physics (IOP)
    Details
    Publication Date: 2018-11-28
    Description: The isospin effect in peripheral heavy-ion collisions was thoroughly investigated within the framework of the Lanzhou quantum molecular dynamics (LQMD) transport model. A coalescence approach was used to recognize the primary fragments formed in nucleus-nucleus collisions. The secondary decay process of these fragments was described using the statistical code GEMINI. The production mechanism and isospin effect of the projectile-like and target-like fragments were analyzed using the combined approach. It was found that the isospin migration from the high-isospin density to the low-density matter occurred in the neutron-rich nuclear reactions, i.e., 48 Ca+ 208 Pb, 86 Kr+ 48 Ca/ 208 Pb/ 124 Sn, 136 Xe+ 208 Pb, 124 Sn+ 124 Sn, and 136 Xe+ 136 Xe. A hard symmetry energy was available for creating the neutron-rich fragments, particularly in the medium-mass region. The isosp...
    Print ISSN: 1674-1137
    Topics: Physics
    Published by Institute of Physics (IOP)
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  • 10
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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
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