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  • 1
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    Coupling valley to antiferromagnetic order [Applied Physical Sciences] (2013)
    National Academy of Sciences
    Details
    Publication Date: 2013-03-06
    Description: Conventional electronics are based invariably on the intrinsic degrees of freedom of an electron, namely its charge and spin. The exploration of novel electronic degrees of freedom has important implications in both basic quantum physics and advanced information technology. Valley, as a new electronic degree of freedom, has received considerable...
    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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  • 2
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    Single transcriptional and translational preQ1 riboswitches adopt similar pre-folded ensembles that follow distinct folding pathways into the same ligand-bound structure (2013)
    Oxford University Press
    Details
    Publication Date: 2013-12-07
    Description: Riboswitches are structural elements in the 5' untranslated regions of many bacterial messenger RNAs that regulate gene expression in response to changing metabolite concentrations by inhibition of either transcription or translation initiation. The preQ 1 (7-aminomethyl-7-deazaguanine) riboswitch family comprises some of the smallest metabolite sensing RNAs found in nature. Once ligand-bound, the transcriptional Bacillus subtilis and translational Thermoanaerobacter tengcongensis preQ 1 riboswitch aptamers are structurally similar RNA pseudoknots; yet, prior structural studies have characterized their ligand-free conformations as largely unfolded and folded, respectively. In contrast, through single molecule observation, we now show that, at near-physiological Mg 2+ concentration and pH, both ligand-free aptamers adopt similar pre-folded state ensembles that differ in their ligand-mediated folding. Structure-based Go-model simulations of the two aptamers suggest that the ligand binds late ( Bacillus subtilis ) and early ( Thermoanaerobacter tengcongensis ) relative to pseudoknot folding, leading to the proposal that the principal distinction between the two riboswitches lies in their relative tendencies to fold via mechanisms of conformational selection and induced fit, respectively. These mechanistic insights are put to the test by rationally designing a single nucleotide swap distal from the ligand binding pocket that we find to predictably control the aptamers' pre-folded states and their ligand binding affinities.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
    Published by Oxford University Press
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  • 3
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    Using a two-capillary viscometer with preheating to measure the viscosity of dilute argon from 298.15 K to 653.15 K (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-18
    Description: Currently, there exists only one set of experimental results at temperatures up to 680 K with the claimed relative standard uncertainty of (0.15–0.20)%. This paper reports new experimental results using the two-capillary viscometer in the temperature range from 298.15 K to 653.15 K with the claimed relative standard uncertainty of 0.062%. The new measurements agree with the existing high accuracy measurements and ab initio calculations in the overlapping temperature range within the extraordinary low relative differences of ±0.08%. The good agreement represents a robust proof of the potential models derived from the ab initio calculations, which play the powerful means in obtaining the thermophysical properties of dilute monoatomic gases over wide temperature ranges. In the experiments, the authors observed the occurrence of insufficient preheating existing with the two-capillary viscometer at high temperature.
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
    Published by American Institute of Physics (AIP)
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  • 4
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    The Genome of the Myxosporean Thelohanellus kitauei Shows Adaptations to Nutrient Acquisition within Its Fish Host (2014)
    Oxford University Press
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    Publication Date: 2014-12-14
    Description: Members of Myxozoa, a parasitic metazoan taxon, have considerable detrimental effects on fish hosts and also have been associated with human food-borne illness. Little is known about their biology and metabolism. Analysis of the genome of Thelohanellus kitauei and comparative analysis with genomes of its two free-living cnidarian relatives revealed that T. kitauei has adapted to parasitism, as indicated by the streamlined metabolic repertoire and the tendency toward anabolism rather than catabolism. Thelohanellus kitauei mainly secretes proteases and protease inhibitors for nutrient digestion (parasite invasion), and depends on endocytosis (mainly low-density lipoprotein receptors-mediated type) and secondary carriers for nutrient absorption. Absence of both classic and complementary anaerobic pathways and gluconeogenesis, the lack of de novo synthesis and reduced activity in hydrolysis of fatty acids, amino acids, and nucleotides indicated that T. kitauei in this vertebrate host–parasite system has adapted to inhabit a physiological environment extremely rich in both oxygen and nutrients (especially glucose), which is consistent with its preferred parasitic site, that is, the host gut submucosa. Taking advantage of the genomic and transcriptomic information, 23 potential nutrition-related T. kitauei -specific chemotherapeutic targets were identified. This first genome sequence of a myxozoan will facilitate development of potential therapeutics for efficient control of myxozoan parasites and ultimately prevent myxozoan-induced fish-borne illnesses in humans.
    Electronic ISSN: 1759-6653
    Topics: Biology
    Published by Oxford University Press
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  • 5
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    A novel system for measurement of the transverse electron momentum distribution from photocathodes (2015)
    American Institute of Physics (AIP)
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    Publication Date: 2015-01-08
    Description: The transverse momentum of electrons produced by a photocathode contributes significantly to the performance of several different types of accelerator-based light sources, such as Free Electron Lasers, as well as systems designed for ultrafast electron diffraction and dynamic transmission electron microscopy. Minimization of the transverse emittance from photocathodes is the subject of intensive research, and therefore measurement of this parameter is of great importance. Here, we describe a simple system that offers real time measurements of transverse emittance and can be easily integrated into the photocathode fabrication process.
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by American Institute of Physics (AIP)
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  • 6
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    Emergent $c$-axis magnetic helix in manganite-nickelate superlattices (2018)
    American Physical Society (APS)
    Details
    Publication Date: 2018-11-03
    Description: Author(s): G. Fabbris, N. Jaouen, D. Meyers, J. Feng, J. D. Hoffman, R. Sutarto, S. G. Chiuzbăian, A. Bhattacharya, and M. P. M. Dean Interfacial effects in transition metal oxide heterostructures can drive novel magnetism that is not observed in their bulk constituents. Here, the authors use resonant soft x-ray techniques to demonstrate that a helical magnetic structure occurs in the nickelate layers of the (LaNiO 3 ) 3 /(La 2 / 3 Sr 1 / 3 MnO 3 ) 9 heterostructure. By measuring the Ni 3 d electronic configuration, they suggest that the observed helical magnetism is derived from a spin density wave instability in the nickelate layer. This work thus provides important hints into how to drive new forms of magnetism in transition metal oxide heterostructure. [Phys. Rev. B 98, 180401(R)] Published Fri Nov 02, 2018
    Keywords: Magnetism
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
    Topics: Physics
    Published by American Physical Society (APS)
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  • 7
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    Gradual reduction in ionospheric F2 region before 2013 Lushan earthquake: contributed to the forthcoming earthquake or solar activity? (2017)
    Wiley
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    Publication Date: 2017-01-26
    Description: Ionospheric anomalies before earthquakes during geomagnetic quiet conditions have been extensively discussed due to the importance of earthquake prediction. However, because of the high variability of ionosphere, a real caution should be adopted before attributing the observations to seismo-ionospheric precursors (SIPs). In an investigation of contradictory results in ionospheric variation before 2013 Lushan earthquake, we examine the ionospheric variation versus solar activity. In order to assess the influence of solar activity of 27-day periodicity on ionospheric variation, a quadratic regression model is developed by using the data of F2-layer critical frequency (foF2) in April of 2008-2014. Using the model, ionospheric variation before the 2013 Lushan earthquake is analyzed. The results show that foF2 was strongly correlated with solar activity index, F10.7, and had a low correlation with the remaining by eliminating the contribution of solar radiation, which indicates that the gradual reduction in foF2 before the earthquake was contributed to the variation of solar radiation rather than the forthcoming earthquake.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
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    Triploid Production from Interspecific Crosses of Two Diploid Perennial Helianthus with Diploid Cultivated Sunflower (Helianthus annuus L.) (2017)
    Genetics Society of America (GSA)
    Details
    Publication Date: 2017-04-14
    Description: Wild Helianthus species are a valuable genetic resource for the improvement of cultivated sunflower. We report the discovery and characterization of a unique high frequency production of triploids when cultivated sunflower was pollinated by specific accessions of diploid Helianthus nuttallii T. & G. and H. maximiliani Schr. Genomic in situ hybridization (GISH) analyses indicated that the triploid F 1 s had two genomes from the wild pollen sources and one from the cultivated line. Mitotic chromosome analyses indicated that the frequency of triploid progenies from the crosses of cultivated lines x H. nuttallii accession 102 (N102) was significantly higher than those of unexpected polyploid progenies from the crosses of wild perennial species x N102, and no unexpected polyploids were obtained from the reverse crosses. Pollen stainability analysis suggested the existence of a low percentage of unreduced (2 n ) male gametes in some accessions, especially N102 and H. maximiliani accession 1113 (M1113), which were generated at the telophase II and tetrad stages of meiosis. The triploid F 1 s could be the results of preferred fertilization of the low frequency of 2 n male gametes with the female gametes of the cultivated sunflower, due to the dosage factors related to recognition and rejection of foreign pollen during fertilization. The triploids have been used to produce amphiploids and aneuploids. Future studies of the male gametes’ fate from pollination through fertilization will further uncover the mechanism of this whole genome transmission. Studies of the genetic control of this trait will facilitate research on sunflower polyploidy speciation and evolution, and the utilization of this trait in sunflower breeding.
    Electronic ISSN: 2160-1836
    Topics: Biology
    Published by Genetics Society of America (GSA)
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  • 9
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    The recent progress in proteochemometric modelling: focusing on target descriptors, cross-term descriptors and application scope (2017)
    Oxford University Press
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    Publication Date: 2017-01-10
    Description: As an extension of the conventional quantitative structure activity relationship models, proteochemometric (PCM) modelling is a computational method that can predict the bioactivity relations between multiple ligands and multiple targets. Traditional PCM modelling includes three essential elements: descriptors (including target descriptors, ligand descriptors and cross-term descriptors), bioactivity data and appropriate learning functions that link the descriptors to the bioactivity data. Since its appearance, PCM modelling has developed rapidly over the past decade by taking advantage of the progress of different descriptors and machine learning techniques, along with the increasing amounts of available bioactivity data. Specifically, the new emerging target descriptors and cross-term descriptors not only significantly increased the performance of PCM modelling but also expanded its application scope from traditional protein–ligand interaction to more abundant interactions, including protein–peptide, protein–DNA and even protein–protein interactions. In this review, target descriptors and cross-term descriptors, as well as the corresponding application scope, are intensively summarized. Additionally, we look forward to seeing PCM modelling extend into new application scopes, such as Target-Catalyst-Ligand systems, with the further development of descriptors, machine learning techniques and increasing amounts of available bioactivity data.
    Print ISSN: 1467-5463
    Electronic ISSN: 1477-4054
    Topics: Biology , Computer Science
    Published by Oxford University Press
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  • 10
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    A three-dimensional computation of the force and torque on an ellipsoid settling slowly through a viscoelastic fluid (1995)
    Cambridge University Press
    Details
    Publication Date: 1995-01-25
    Description: The orientation of an ellipsoid falling in a viscoelastic fluid is studied by methods of perturbation theory. For small fall velocity, the fluid’s rheology is described by a second-order fluid model. The solution of the problem can be expressed by a dual expansion in two small parameters: the Reynolds number representing the inertial effect and the Weissenberg number representing the effect of the non-Newtonian stress. Then the original problem is split into three canonical problems: the zeroth-order Stokes problem for a translating ellipsoid and two first-order problems, one for inertia and one for second-order rheology. A Stokes operator is inverted in each of the three cases. The problems are solved numerically on a three-dimensional domain by a finite element method with fictitious domains, and the force and torque on the body are evaluated. The results show that the signs of the perturbation pressure and velocity around the particle for inertia are reversed by viscoelasticity. The torques are also of opposite sign: inertia turns the major axis of the ellipsoid perpendicular to the fall direction; normal stresses turn the major axis parallel to the fall. The competition of these two effects gives rise to an equilibrium tilt angle between 0° and 90° which the settling ellipsoid would eventually assume. The equilibrium tilt angle is a function of the elasticity number, which is the ratio of the Weissenberg number and the Reynolds number. Since this ratio is independent of the fall velocity, the perturbation results do not explain the sudden turning of a long body which occurs when a critical fall velocity is exceeded. This is not surprising because the theory is valid only for slow sedimentation. However, the results do seem to agree qualitatively with ‘shape tilting’ observed at low fall velocities. © 1995, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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