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Najev A, Hameed S, Gautreau D, Wang Z, Joe J, Požek M, Birol T, Fernandes RM, Greven M, Pelc D. Uniaxial Strain Control of Bulk Ferromagnetism in Rare-Earth Titanates. Phys Rev Lett 2022; 128:167201. [PMID: 35522519 DOI: 10.1103/physrevlett.128.167201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Revised: 10/26/2021] [Accepted: 03/04/2022] [Indexed: 06/14/2023]
Abstract
The perovskite rare-earth titanates are model Mott insulators with magnetic ground states that are very sensitive to structural distortions. These distortions couple strongly to the orbital degrees of freedom and, in principle, it should be possible to tune the superexchange and the magnetic transition with strain. We investigate the representative system (Y,La,Ca)TiO_{3}, which exhibits low crystallographic symmetry and no structural instabilities. From magnetic susceptibility measurements of the Curie temperature, we demonstrate direct, reversible, and continuous control of ferromagnetism by influencing the TiO_{6} octahedral tilts and rotations with uniaxial strain. The relative change in T_{C} as a function of strain is well described by ab initio calculations, which provides detailed understanding of the complex interactions among structural, orbital, and magnetic properties in rare-earth titanates. The demonstrated manipulation of octahedral distortions opens up far-reaching possibilities for investigations of electron-lattice coupling, competing ground states, and magnetic quantum phase transitions in a wide range of quantum materials.
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Affiliation(s)
- A Najev
- Department of Physics, Faculty of Science, University of Zagreb, Bijenička 32, HR-10000 Zagreb, Croatia
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - S Hameed
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - D Gautreau
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Z Wang
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - J Joe
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - M Požek
- Department of Physics, Faculty of Science, University of Zagreb, Bijenička 32, HR-10000 Zagreb, Croatia
| | - T Birol
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - R M Fernandes
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - M Greven
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - D Pelc
- Department of Physics, Faculty of Science, University of Zagreb, Bijenička 32, HR-10000 Zagreb, Croatia
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
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Zhang H, Zhao Z, Gautreau D, Raczkowski M, Saha A, Garlea VO, Cao H, Hong T, Jeschke HO, Mahanti SD, Birol T, Assaad FF, Ke X. Coexistence and Interaction of Spinons and Magnons in an Antiferromagnet with Alternating Antiferromagnetic and Ferromagnetic Quantum Spin Chains. Phys Rev Lett 2020; 125:037204. [PMID: 32745383 DOI: 10.1103/physrevlett.125.037204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 06/18/2020] [Indexed: 06/11/2023]
Abstract
In conventional quasi-one-dimensional antiferromagnets with quantum spins, magnetic excitations are carried by either magnons or spinons in different energy regimes: they do not coexist independently, nor could they interact with each other. In this Letter, by combining inelastic neutron scattering, quantum Monte Carlo simulations, and random phase approximation calculations, we report the discovery and discuss the physics of the coexistence of magnons and spinons and their interactions in Botallackite-Cu_{2}(OH)_{3}Br. This is a unique quantum antiferromagnet consisting of alternating ferromagnetic and antiferromagnetic spin-1/2 chains with weak interchain couplings. Our study presents a new paradigm where one can study the interaction between two different types of magnetic quasiparticles: magnons and spinons.
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Affiliation(s)
- H Zhang
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - Z Zhao
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, People's Republic of China
| | - D Gautreau
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minnesota 55455, USA
| | - M Raczkowski
- Institut für Theoretische Physik und Astrophysik, Universität Würzburg, 97074 Würzburg, Germany
| | - A Saha
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minnesota 55455, USA
| | - V O Garlea
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - H Cao
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - T Hong
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - H O Jeschke
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| | - Subhendra D Mahanti
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - T Birol
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minnesota 55455, USA
| | - F F Assaad
- Institut für Theoretische Physik und Astrophysik, Universität Würzburg, 97074 Würzburg, Germany
- Würzburg-Dresden Cluster of Excellence ct.qmat, Am Hubland, D-97074 Würzburg, Germany
| | - X Ke
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
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Caroff N, Espaze E, Gautreau D, Richet H, Reynaud A. Analysis of the effects of -42 and -32 ampC promoter mutations in clinical isolates of Escherichia coli hyperproducing ampC. J Antimicrob Chemother 2000; 45:783-8. [PMID: 10837430 DOI: 10.1093/jac/45.6.783] [Citation(s) in RCA: 139] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Escherichia coli usually produces only very small amounts of a constitutive AmpC beta-lactamase, but clinical strains overproducing this enzyme have been isolated. Three different ampC promoters of E. coli clinical strains were cloned upstream of the chloramphenicol acetyltransferase (CAT) gene in the pKK232-8 reporter plasmid and their relative strengths were compared by two different methods. The strength of the promoters from AmpC hyperproducers was 70- to 120-fold higher than those from a low-level AmpC producer. One of the strong promoters, which differs from strain K12 at bases -88, -82, -42, -18, -1 and +58, was mutated to abolish the -42 mutation. This change resulted in a 43-fold decrease in CAT concentration. In another promoter, with eight different mutations at positions -88, -82, -32, -18, -1, +5, +24 and +58, the -32T-->A transversion, which created perfect homology with the -35 consensus sequence, was reverted; this led to a 13-fold decrease in CAT concentration. The -42 and -32 mutations play an important role in E. coli resistance to beta-lactams by increasing ampC transcription.
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Affiliation(s)
- N Caroff
- Laboratoire de Bactériologie-Virologie, Faculté de Pharmacie, 1 rue Gaston Veil, 44035 Nantes. Laboratoire de Bactériologie, Virologie, Hygiène hospitalière, CHU, Nantes, France.
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Abstract
Cytoplasmic localization of mRNA molecules is a powerful mechanism for generating cell polarity. In vertebrates, one paradigm is localization of Vg1 RNA within the Xenopus oocyte, a process directed by recognition of a localization element within the Vg1 3' UTR. We show that specific base changes within the localization element abolish both localization in vivo and binding in vitro by a single protein, VgRBP60. VgRBP60 is homologous to a human hnRNP protein, hnRNP I, and combined immunolocalization and in situ hybridization demonstrate striking colocalization of hnRNP I and Vg1 RNA within the vegetal cytoplasm of the Xenopus oocyte. These results implicate a novel role in cytoplasmic RNA transport for this family of nuclear RNA-binding proteins.
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Affiliation(s)
- C A Cote
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island 02912, USA
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Caroff N, Chamoux C, Gallou FL, Gavini F, Gautreau D, Richet H, Reynaud A. Two Epidemiologically Related Cases of Rahnella aquatilis Bacteremia. Eur J Clin Microbiol Infect Dis 1998. [DOI: 10.1007/s100960050080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Caroff N, Chamoux C, Le Gallou F, Espaze E, Gavini F, Gautreau D, Richet H, Reynaud A. Two epidemiologically related cases of Rahnella aquatilis bacteremia. Eur J Clin Microbiol Infect Dis 1998; 17:349-52. [PMID: 9721965 DOI: 10.1007/bf01709459] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Rahnella aquatilis was isolated from the blood cultures of two patients who were in different units of the same hospital. Both isolates were susceptible to aminoglycosides, fluoroquinolones, cotrimoxazole, piperacillin, third generation cephalosporins and amoxicillin-clavulanate, but resistant to amoxicillin, ticarcillin, and first generation cephalosporins. The synergistic activity of amoxicillin and clavulanic acid suggested the presence of a beta-lactamase, confirmed by a positive nitrocefin test and by analytical isoelectric focusing. Pulsed-field gel electrophoresis and ribotyping with the pKK3535 probe showed that the isolates shared the same banding pattern. The results of an epidemiological study suggested that an in-house total parenteral nutrition solution might be the source of this unusual gram-negative rod.
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Affiliation(s)
- N Caroff
- Laboratoire de Bactériologie, Virologie, Hygiène hospitalière, Institut de Biologie, Nantes, France.
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Gautreau D, Cote CA, Mowry KL. Two copies of a subelement from the Vg1 RNA localization sequence are sufficient to direct vegetal localization in Xenopus oocytes. Development 1997; 124:5013-20. [PMID: 9362462 DOI: 10.1242/dev.124.24.5013] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Localization of mRNA has emerged as a fundamental mechanism for generating polarity during development. In vertebrates, one example of this phenomenon is Vg1 RNA, which is localized to the vegetal cortex of Xenopus oocytes. Vegetal localization of Vg1 RNA is directed by a 340-nt sequence element contained within its 3′ untranslated region. To investigate how such cis-acting elements function in the localization process, we have undertaken a detailed analysis of the precise sequence requirements for vegetal localization within the 340-nt localization element. We present evidence for considerable redundancy within the localization element and demonstrate that critical sequences lie at the ends of the element. Importantly, we show that a subelement from the 5′ end of the Vg1 localization element is, when duplicated, sufficient to direct vegetal localization. We suggest that the Vg1 localization element is composed of smaller, redundant sequence motifs and identify one such 6-nt motif as essential for localization. These results allow insight into what constitutes an RNA localization signal and how RNA sequence elements may act in the localization process.
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Affiliation(s)
- D Gautreau
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
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Abstract
Gr16 (chromosome 2, 6.9 cM) is a dominant, grey egg mutation of the domestic silkmoth, Bombyx mori, which produces an opaque instead of a translucent chorion. To determine the underlying cause of this defect, we examined the effects of the mutation on chorion ultrastructure, protein accumulation, and biosynthesis patterns, and on the restriction patterns of early chorion structural genes, using the presumed wild-type progenitor strain, Old European 16 (OE16), for comparison. Cross-sections of mature chorions examined by scanning electron microscopy showed that the inner lamellae were oriented perpendicular, rather than parallel, to the egg surface, with a smaller vertical zone bordered by normally oriented lamellae in the heterozygote, suggestive of codominant expression. This defect first appeared in transmission electron micrographs early in choriogenesis, probably during framework formation and/or expansion stages. Mature chorion protein patterns resolved by isoelectric focusing or two-dimensional polyacrylamide gel electrophoresis, synthetic profiles of virtually all chorion proteins following pulse-labeling with tritiated or [14C]glycine, and restriction patterns of early chorion genes examined by Southern blot hybridization were identical between mutant, wild-type, and heterozygote. These observations ruled out a major deletion of chorion structural genes or defects in the production and accumulation of normal chorion proteins as mechanisms underlying the mutation, unlike other putative Gr mutants mapping in its vicinity. The sole difference that we detected was a set of minor, early protein doublets of related size but differing isoelectric point, which showed reciprocal labeling intensities in Gr16 vs OE16 and were codominantly expressed. Preliminary pulse-chase experiments suggested that these proteins may be post-translationally modified forms which undergo differential processing in mutant and wild-type. Based on these observations, we postulate that the Gr16 mutation affects the primary structure of a minor, previously unidentified chorion or follicular cell component which is critical for determining lamellar orientation, and discuss models of how this might function.
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Affiliation(s)
- D Gautreau
- Department of Zoology, University of Rhode Island, Kingston 02881-0816
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