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  • 1
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    Temperature-induced sign change of the magnetic interlayer coupling in Ni/Ni25Mn75/Ni trilayers on Cu3Au(001) (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-05-05
    Description: We investigated the magnetic interlayer coupling between two ferromagnetic (FM) Ni layers through an antiferromagnetic (AFM) Ni 25 Mn 75 layer and the influence of this coupling on the exchange bias phenomenon. The interlayer coupling energy of an epitaxial trilayer of 14 atomic monolayers (ML) Ni/45 ML Ni 25 Mn 75 /16 ML Ni on Cu 3 Au(001) was extracted from minor-loop magnetization measurements using in-situ magneto-optical Kerr effect. The interlayer coupling changes from ferromagnetic to antiferromagnetic when the temperature is increased above 300 K. This sign change is interpreted as the result of the competition between an antiparallel Ruderman-Kittel-Kasuya-Yosida (RKKY)-type interlayer coupling, which dominates at high temperature, and a stronger direct exchange coupling across the AFM layer, which is present only below the Néel temperature of the AFM layer.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 2
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    Physical origin of Davydov splitting and resonant Raman spectroscopy of Davydov components in multilayer MoTe_{2} (2016)
    American Physical Society (APS)
    Details
    Publication Date: 2016-03-08
    Description: Author(s): Q. J. Song, Q. H. Tan, X. Zhang, J. B. Wu, B. W. Sheng, Y. Wan, X. Q. Wang, L. Dai, and P. H. Tan We systematically study the high-resolution and polarized Raman spectra of multilayer (ML) MoTe 2 . The layer-breathing (LB) and shear (C) modes are observed in the ultralow-frequency region, which are used to quantitatively evaluate the interlayer coupling in ML MoTe 2 based on the linear chain model,… [Phys. Rev. B 93, 115409] Published Tue Mar 08, 2016
    Keywords: Surface physics, nanoscale physics, low-dimensional systems
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
    Topics: Physics
    Published by American Physical Society (APS)
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  • 3
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    Facilitation of trace metal uptake in cells by inulin coating of metallic nanoparticles (2017)
    Royal Society
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    Publication Date: 2017-09-14
    Description: Trace elements such as zinc and iron are essential for the proper function of biochemical processes, and their uptake and bioavailability are dependent on their chemical form. Supplementation of trace metals through nanostructured materials is a new field, but its application raises concerns regarding their toxicity. Here, we compared the intracellular zinc uptake of different sources of zinc: zinc sulfate, and ZnO and core-shell α-Fe 2 O 3 @ZnO nanoparticles, coated or uncoated with inulin, an edible and biocompatible polysaccharide. Using mussel haemocytes, a well-known model system to assess nanomaterial toxicity, we simultaneously assessed zinc accumulation and multiple cellular response endpoints. We found that intracellular zinc uptake was strongly enhanced by inulin coating, in comparison to the uncoated nanoparticles, while no significant effects on cell death, cell viability, mitochondrial membrane integrity, production of reactive oxygen species or lysosome abundance were observed at concentrations up to 20 ppm. Since no significant increments in toxicity were observed, the coated nanomaterials may be useful to increase in vivo zinc uptake for nutritional applications.
    Keywords: nanotechnology, biochemistry, cellular biology
    Electronic ISSN: 2054-5703
    Topics: Natural Sciences in General
    Published by Royal Society
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  • 4
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    The dynamic process and microscopic mechanism of extraordinary terahertz transmission through perforated superconducting films (2015)
    Springer Nature
    Details
    Publication Date: 2015-10-27
    Description: The dynamic process and microscopic mechanism of extraordinary terahertz transmission through perforated superconducting films Scientific Reports, Published online: 26 October 2015; doi:10.1038/srep15588
    Electronic ISSN: 2045-2322
    Topics: Natural Sciences in General
    Published by Springer Nature
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  • 5
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    Low radio frequency observations and spectral modelling of the remnant of Supernova 1987A (2016)
    Oxford University Press
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    Publication Date: 2016-08-03
    Description: We present Murchison Widefield Array observations of the supernova remnant (SNR) 1987A between 72 and 230 MHz, representing the lowest frequency observations of the source to date. This large lever arm in frequency space constrains the properties of the circumstellar medium created by the progenitor of SNR 1987A when it was in its red supergiant phase. As of late 2013, the radio spectrum of SNR 1987A between 72 MHz and 8.64 GHz does not show any deviation from a non-thermal power law with a spectral index of –0.74 ± 0.02. This spectral index is consistent with that derived at higher frequencies, beneath 100 GHz, and with a shock in its adiabatic phase. A spectral turnover due to free–free absorption by the circumstellar medium has to occur below 72 MHz, which places upper limits on the optical depth of ≤0.1 at a reference frequency of 72 MHz, emission measure of 13 000 cm –6  pc, and an electron density of 110 cm –3 . This upper limit on the electron density is consistent with the detection of prompt radio emission and models of the X-ray emission from the supernova. The electron density upper limit implies that some hydrodynamic simulations derived a red supergiant mass-loss rate that is too high, or a wind velocity that is too low. The mass-loss rate of ~5 x 10 –6  M  yr –1 and wind velocity of 10 km s –1 obtained from optical observations are consistent with our upper limits, predicting a current turnover frequency due to free–free absorption between 5 and 60 MHz.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 6
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    Elimination of X-Ray Diffraction through Stimulated X-Ray Transmission (2016)
    American Physical Society (APS)
    Details
    Publication Date: 2016-07-07
    Description: Author(s): B. Wu, T. Wang, C. E. Graves, D. Zhu, W. F. Schlotter, J. J. Turner, O. Hellwig, Z. Chen, H. A. Dürr, A. Scherz, and J. Stöhr The absorption and diffraction of an x-ray pulse transmitted through a magnetic cobalt-palladium multilayer decrease with increasing x-ray intensity. [Phys. Rev. Lett. 117, 027401] Published Wed Jul 06, 2016
    Keywords: Condensed Matter: Electronic Properties, etc.
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society (APS)
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  • 7
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    Rescue of dopamine by NSCs in PD rats [Neuroscience] (2014)
    National Academy of Sciences
    Details
    Publication Date: 2014-11-05
    Description: Embryonic stem cell-based therapies exhibit great potential for the treatment of Parkinson’s disease (PD) because they can significantly rescue PD-like behaviors. However, whether the transplanted cells themselves release dopamine in vivo remains elusive. We and others have recently induced human embryonic stem cells into primitive neural stem cells (pNSCs) that...
    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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    History of Plastid DNA Insertions Reveals Weak Deletion and AT Mutation Biases in Angiosperm Mitochondrial Genomes (2014)
    Oxford University Press
    Details
    Publication Date: 2014-12-16
    Description: Angiosperm mitochondrial genomes exhibit many unusual properties, including heterogeneous nucleotide composition and exceptionally large and variable genome sizes. Determining the role of nonadaptive mechanisms such as mutation bias in shaping the molecular evolution of these unique genomes has proven challenging because their dynamic structures generally prevent identification of homologous intergenic sequences for comparative analyses. Here, we report an analysis of angiosperm mitochondrial DNA sequences that are derived from inserted plastid DNA ( mtpts ). The availability of numerous completely sequenced plastid genomes allows us to infer the evolutionary history of these insertions, including the specific nucleotide substitutions and indels that have occurred because their incorporation into the mitochondrial genome. Our analysis confirmed that many mtpts have a complex history, including frequent gene conversion and multiple examples of horizontal transfer between divergent angiosperm lineages. Nevertheless, it is clear that the majority of extant mtpt sequence in angiosperms is the product of recent transfer (or gene conversion) and is subject to rapid loss/deterioration, suggesting that most mtpts are evolving relatively free from functional constraint. The evolution of mtpt sequences reveals a pattern of biased mutational input in angiosperm mitochondrial genomes, including an excess of small deletions over insertions and a skew toward nucleotide substitutions that increase AT content. However, these mutation biases are far weaker than have been observed in many other cellular genomes, providing insight into some of the notable features of angiosperm mitochondrial architecture, including the retention of large intergenic regions and the relatively neutral GC content found in these regions.
    Electronic ISSN: 1759-6653
    Topics: Biology
    Published by Oxford University Press
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  • 9
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    Irrigation Decisions for Major West Coast Crops: Water Scarcity and Climatic Determinants (2015)
    Oxford University Press
    Details
    Publication Date: 2015-12-13
    Description: This article uses the 2007 Farm and Ranch Irrigation Survey database developed by the U.S. Department of Agriculture to assess the impact of water scarcity and climate on irrigation decisions for producers of specialty crops, wheat, and forage crops. We estimate an irrigation management model for major crops in the West Coast (California, Oregon, and Washington), which includes a farm-level equation of irrigated share and crop-specific equations of technology adoption and water application rate (orchard/vineyard, vegetable, wheat, alfalfa, hay, and pasture). We find that economic and physical water scarcity, climate, and extreme weather, such as frost, extreme heat, and drought, significantly impact producers’ irrigation decisions. Producers use sprinkler technologies or additional water applications to mitigate risk of crop damage from extreme weather. Water application rates are least responsive to surface water cost or groundwater well depth for producers of orchard/vineyard. Water supply institutions influence producers’ irrigation decisions. Producers who receive water from federal agencies use higher water application rates and are less likely to adopt water-saving irrigation technologies for some crops. Institutional arrangements, including access to distinct water sources (surface or ground) and whether surface water cost is fee based, also affect the responsiveness of water application rates to changes in surface water cost. The analysis provides valuable information about how producers in irrigated agricultural production systems would respond and adapt to water pricing policies and climate change.
    Keywords: Q12 - Micro Analysis of Farm Firms, Farm Households, and Farm Input Markets, Q15 - Land Ownership and Tenure ; Land Reform ; Land Use ; Irrigation, Q16 - R&D ; Agricultural Technology ; Agricultural Extension Services, Q18 - Agricultural Policy ; Food Policy, Q54 - Climate ; Natural Disasters ; Global Warming
    Print ISSN: 0002-9092
    Electronic ISSN: 1467-8276
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
    Published by Oxford University Press
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  • 10
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    A generalized Rytov approximation for accurate calculation of phase variation in strong perturbation media (2019)
    Oxford University Press
    Details
    Publication Date: 2019
    Description: 〈span〉〈div〉SUMMARY〈/div〉In the case of long-range propagation of forward scattering, due to the accumulation of phase changes caused by the velocity perturbations, the validity of the Born approximation will be violated. In contrast, the phase-change accumulation can be handled by the Rytov approximation, which has been widely used for long-distance propagation with only forward scattering or small-angle scattering involved. However, the weak scattering assumption (i.e. small velocity perturbation) in the Rytov approximation limits its scope of application. To address this problem, we analyse the integral kernel of the Rytov transform using the Wentzel-Kramers-Brillouin-Jeffreys (WKBJ) approximation and we demonstrate that the integral kernel is a function of velocity perturbation and scattering angle. By applying a small scattering angle approximation, we show that the phase variation has a linear relationship with the slowness perturbation, no matter how strong the magnitude of perturbation is. Therefore, the new integral equation is then referred to as the generalized Rytov approximation (GRA) because it overcomes the weak scattering assumption of the Rytov approximation. To show the limitations of the Rytov approximation and the advantages of the proposed GRA method, first we design a two-layer model and we analytically calculate the errors introduced by the small scattering angle assumption using plane wave incidence. We show that the phase (traveltime) variations predicted by the GRA are always more accurate than the Rytov approximation. Particularly, the GRA produces accurate phase variations for the normal incident plane wave regardless of the magnitude of velocity perturbation. Numerical examples using Gaussian anomaly models demonstrate that the scattering angle has a crucial impact on the accuracy of the GRA. If the small scattering angle assumption holds, the GRA can produce an accurate phase approximation even if the velocity perturbation is very strong. On the contrary, both the first-order Rytov approximation and the GRA fail to get satisfying results when the scattering angle is large enough. The proposed GRA method has the potential to be used for traveltime modelling and inversion for large-scale strong perturbation media.〈/span〉
    Print ISSN: 2051-1965
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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