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Synergetic Phenomenon between Structural Distortion and Cobalt Valence State and its Effect on the Oxygen Evolution Reaction in Cobalt Ferrites

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ceramics International 2025年

作者： Fabiano R. Praxedes Thayse R. Silva Maria C.M. Ferreira Marcos A.L. Nobre Daniel A. Macedo Silvania Lanfredi Department of Chemistry and Biochemistry São Paulo State University (Unesp) School of Technology and Sciences R. Roberto Simonsen – 305 CEP: 19060-900 Presidente Prudente - SP Brazil São Paulo State University (Unesp) Institute of Biosciences Humanities and Exact Sciences São José do Rio Preto SP 15054-000 Brazil Materials Science and Engineering Postgraduate Program Federal University of Paraíba (UFPB) 58051-900 João Pessoa - PB Brazil Department of Physics São Paulo State University (Unesp) School of Technology and Sciences R. Roberto Simonsen – 305 CEP: 19060-900 Presidente Prudente - SP Brazil

Nanopowders of cobalt ferrite with the stoichiometry Co x Fe 3-x O 4 (0.4 ≤ x ≤ 1.2) were synthesized at 80 °C using a co-precipitation method. The resulting crystalline, single-phase powders were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Morphological analysis of the cobalt ferrite nanoparticles revealed the formation of spherical particle agglomerates at the nanoscale. Chemical bond analysis by infrared spectroscopy, based on the deconvolution of absorption bands, together with structural characterization by XRD and Rietveld refinement, confirmed the formation of a spinel-type phase with cubic symmetry and space group Fd-3m. The improved electrocatalytic performance was observed for the sample with the highest Co content (Co 1.2 Fe 1.8 O 4 , requiring 320 mV to achieve 10 mA cm -2 ). The structure-activity relationships indicate the OER mechanism in our cobalt ferrites is governed by three interconnected factors: octahedral Co 3+ dominance, bond-angle flexibility, and increased Co content, synergistically enhancing catalytic efficiency.

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Experimentally shock-induced melt veins in basalt: Improving the shock classification of eucrites

arXiv

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arXiv 2022年

作者： Ono, Haruka Kurosawa, Kosuke Niihara, Takafumi Mikouchi, Takashi Tomioka, Naotaka Isa, Junko Kagi, Hiroyuki Matsuzaki, Takuya Sakuma, Hiroshi Genda, Hidenori Sakaiya, Tatsuhiro Kondo, Tadashi Kayama, Masahiro Koike, Mizuho Sano, Yuji Murayama, Masafumi Satake, Wataru Matsui, Takafumi Planetary Exploration Research Center Chiba Institute of Technology 2-17-1 Tsudanuma Narashino Chiba275-0016 Japan Department of Applied Science Okayama University of Science 1-1 Ridaicho Kita-ku Okayama-shi700-0005 Japan The University Museum The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo113-0033 Japan 200 Monobe Otsu Kochi Nankoku783-8502 Japan Geochemical Research Center Graduate School of Science The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo113-0033 Japan Center for Advanced Marine Core Research Kochi University 200 Monobe Otsu Kochi Nankoku783-8502 Japan Research Center for Functional Materials National Institute for Materials Science 1-1 Namiki Ibaraki Tsukuba305-0044 Japan Earth–Life Science Institute Tokyo Institute of Technology 2-12-1 Ookayama Meguro-ku Tokyo152-8550 Japan Department of Earth and Space Science Graduate School of Science Osaka University 1-1 Machikaneyama Osaka Toyonaka560-0043 Japan Department of General Systems Studies Graduate School of Arts and Sciences The Univ. of Tokyo 3-8-1 Komaba Meguro-ku Tokyo153-8902 Japan Earth and Planetary Systems Science Program Graduate School of Advanced Science and Engineering Hiroshima University 1-3-1 Kagamiyama Higashi–Hiroshima Hiroshima739-8526 Japan Institute of Geo-Cosmology Chiba Institute of Technology 2-17-1 Tsudanuma Chiba Narashino275-0016 Japan

Basaltic rocks occur widely on the terrestrial planets and differentiated asteroids, including the asteroid 4 Vesta. We conducted a shock recovery experiment with decaying compressive pulses on a terrestrial basalt at Chiba Institute of Technology, Japan. The sample recorded a range of pressures, and shock physics modeling was conducted to add a pressure scale to the observed shock features. The shocked sample was examined by optical and electron microscopy, electron back-scattered diffractometry, and Raman spectroscopy. We found that localized melting occurs at a lower pressure (~10 GPa) than previously thought (>20 GPa). The shocked basalt near the epicenter represents "shock degree C" of a recently proposed classification scheme for basaltic eucrites and, as such, our results provide a pressure scale for the classification scheme. Finally, we estimated the total fraction of the basaltic eucrites classified as shock degree C to be ~15% by assuming the impact velocity distribution onto Vesta. © 2022, CC BY-NC-SA.

关键词： Basalt

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Body appreciation around the world: Measurement invariance of the Body Appreciation Scale-2 (BAS-2) across 65 nations, 40 languages, gender identities, and age

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Body image 2023年 46卷 449-466页

作者： Viren Swami Ulrich S Tran Stefan Stieger Toivo Aavik Hamed Abdollahpour Ranjbar Sulaiman Olanrewaju Adebayo Reza Afhami Oli Ahmed Annie Aimé Marwan Akel Hussam Al Halbusi George Alexias Khawla F Ali Nursel Alp-Dal Anas B Alsalhani Sara Álvares-Solas Ana Carolina Soares Amaral Sonny Andrianto Trefor Aspden Marios Argyrides John Jamir Benzon R Aruta Stephen Atkin Olusola Ayandele Migle Baceviciene Radvan Bahbouh Andrea Ballesio David Barron Ashleigh Bellard Sóley Sesselja Bender Kerime Derya Beydağ Gorana Birovljević Marie-Ève Blackburn Teresita Borja-Alvarez Joanna Borowiec Miroslava Bozogáňová Solfrid Bratland-Sanda Matthew H E M Browning Anna Brytek-Matera Marina Burakova Yeliz Çakır-Koçak Pablo Camacho Vittorio Emanuele Camilleri Valentina Cazzato Silvia Cerea Apitchaya Chaiwutikornwanich Trawin Chaleeraktrakoon Tim Chambers Qing-Wei Chen Xin Chen Chin-Lung Chien Phatthanakit Chobthamkit Bovornpot Choompunuch Emilio J Compte Jennifer Corrigan Getrude Cosmas Richard G Cowden Kamila Czepczor-Bernat Marcin Czub Wanderson Roberto da Silva Mahboubeh Dadfar Simon E Dalley Lionel Dany Jesus Alfonso D Datu Pedro Henrique Berbert de Carvalho Gabriel Lins de Holanda Coelho Avila Odia S De Jesus Sonia Harzallah Debbabi Sandesh Dhakal Francesca Di Bernardo Donka D Dimitrova Jacinthe Dion Barnaby Dixson Stacey M Donofrio Marius Drysch Hongfei Du Angel M Dzhambov Claire El-Jor Violeta Enea Mehmet Eskin Farinaz Farbod Lorleen Farrugia Leonie Fian Maryanne L Fisher Michał Folwarczny David A Frederick Matthew Fuller-Tyszkiewicz Adrian Furnham Antonio Alías García Shulamit Geller Marta Ghisi Alireza Ghorbani Maria Angeles Gomez Martinez Sarah Gradidge Sylvie Graf Caterina Grano Gyöngyvér Gyene Souheil Hallit Motasem Hamdan Jonathan E Handelzalts Paul H P Hanel Steven R Hawks Issa Hekmati Mai Helmy Tetiana Hill Farah Hina Geraldine Holenweger Martina Hřebíčková Olasupo Augustine Ijabadeniyi Asma Imam Başak İnce Natalia Irrazabal Rasa Jankauskiene Ding-Yu Jiang Micaela Jiménez-Borja Verónica Jiménez-Borja Evan M Johnson Veljko Jov School of Psychology and Sport Science Anglia Ruskin University Cambridge United Kingdom Centre for Psychological Medicine Perdana University Kuala Lumpur Malaysia. Electronic address: viren.swami@aru.ac.uk. Department of Cognition Emotion and Methods in Psychology Faculty of Psychology University of Vienna Vienna Austria. Department of Psychology and Psychodynamics Karl Landsteiner University of Health Sciences Krems an der Donau Austria. Institute of Psychology University of Tartu Tartu Estonia. Department of Psychology Koç University Istanbul Turkiye. Department of Psychology and Behavioural Studies Ekiti State University Ado-Ekiti Nigeria. Department of Art Studies Tarbiat Modares University Tehran Iran. Department of Psychology University of Chittagong Chattogram Bangladesh. Department of Psychoeducation and Psychology Université du Québec en Outaouais Saint-Jérôme Canada. INSPECT-LB: National Institute of Public Health Clinical Epidemiology and Toxicology Beirut Lebanon School of Pharmacy Lebanese International University Beirut Lebanon. Department of Management Ahmed Bin Mohammad Military College Doha Qatar. Faculty of Psychology Panteion University of Social and Political Sciences Athens Greece. Royal College of Surgeons Ireland-Bahrain Adliya Bahrain. Department of Midwifery Faculty of Health Sciences Munzur University Tunceli Turkiya. Department of Oral Medicine and Diagnostic Sciences Vision College of Dentistry and Nursing Vision Colleges Riyadh Saudi Arabia. Facultad de Ciencias de la Vida Universidad Regional Amazónica Ikiam Muyuna Ecuador. Federal Institute of Education Science and Technology of Southeast Minas Gerais Barbacena Brazil. Department of Psychology Universitas Islam Indonesia Yogyakarta Indonesia. Department of Psychology Aberystwyth University Ceredigion United Kingdom. Department of Psychology Neapolis University Pafos Paphos Cyprus. Department of Psychology De La Salle University Phillippines. Department of Gen

The Body Appreciation Scale-2 (BAS-2) is a widely used measure of a core facet of the positive body image construct. However, extant research concerning measurement invariance of the BAS-2 across a large number of nations remains limited. Here, we utilised the Body Image in Nature (BINS) dataset - with data collected between 2020 and 2022 - to assess measurement invariance of the BAS-2 across 65 nations, 40 languages, gender identities, and age groups. Multi-group confirmatory factor analysis indicated that full scalar invariance was upheld across all nations, languages, gender identities, and age groups, suggesting that the unidimensional BAS-2 model has widespread applicability. There were large differences across nations and languages in latent body appreciation, while differences across gender identities and age groups were negligible-to-small. Additionally, greater body appreciation was significantly associated with higher life satisfaction, being single (versus being married or in a committed relationship), and greater rurality (versus urbanicity). Across a subset of nations where nation-level data were available, greater body appreciation was also significantly associated with greater cultural distance from the United States and greater relative income inequality. These findings suggest that the BAS-2 likely captures a near-universal conceptualisation of the body appreciation construct, which should facilitate further cross-cultural research.

关键词： Body appreciation Body appreciation Scale-2 (BAS-2) Cross-cultural Measurement invariance Multi-group confirmatory factor analysis (MG-CFA) Psychometrics Structural analysis

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Highly conductive PDMS/carbon nanotube/graphene nanocomposites and effect of sulfuric acid treatment on conductivity

arXiv

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arXiv 2020年

作者： Yetisgin, Abuzer Alp Sakar, Hazal Bermek, Hakan Trabzon, Levent Faculty of Engineering and Natural Sciences Materials Science and Nano-Engineering Program Sabanci University Istanbul34956 Turkey Department of Nanoscience and Nanoengineering Istanbul Technical University Istanbul34469 Turkey Department of Molecular Biology and Genetics Istanbul Technical University Istanbul34469 Turkey Faculty of Mechanical Engineering Istanbul Technical University Istanbul34469 Turkey Nanotechnology Research and Application Center - ITUnano Istanbul Technical University Istanbul Turkey MEMS Research Center Istanbul Technical University Istanbul34469 Turkey

Poly(dimethylsiloxane) (PDMS) is an insulator and it is commonly used in fabrication of micro-structures but there is a need of electrical sonductive pdms. Therefore, this research is mainly focused on producing PDMS nanocomposites with high electrical conductivity. Thus, we produced highly conductive PDMS nanocomposites which were filled with multi-walled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs). Due to the synergistic effect between CNTs and GNPs inside a polymeric matrix, we expected to obtain more conductive nanocomposites than PDMS nanocomposite filled with only CNTs. Additionally, we investigated the effect of sulfuric acid treatment to surface composition and electrical conductivity of prepared PDMS/MWCNT/GNP nanocomposites. Results indicated that electrical conductivity of sulfuric acid-treated samples was significantly higher than untreated samples. The level of conductivity in the range of 270.7 - 1074.9 S/m was obtained, and the higher ones are the samples treated with acid *** Codes 74E30 (Primary) Copyright © 2020, The Authors. All rights reserved.

关键词： Nanocomposites

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Front Cover: Metal-Nitrogen-Carbon Cluster-Decorated Titanium Carbide is a Durable and Inexpensive Oxygen Reduction Reaction Electrocatalyst (ChemSusChem 21/2021)

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ChemSusChem 2021年第21期14卷

作者： Dr. Sung Beom Cho Dr. Cheng He Dr. Shrihari Sankarasubramanian Arashdeep Singh Thind Dr. Javier Parrondo Dr. Jordan A. Hachtel Dr. Albina Y. Borisevich Dr. Juan-Carlos Idrobo Jing Xie Prof. Vijay Ramani Prof. Rohan Mishra Department of Mechanical Engineering and Materials Science Washington University in St. Louis St. Louis Missouri 63130 USA Virtual Engineering Center Technology Convergence Division Korea Institute of Ceramic Engineering and Technology (KICET) Jinju 52851 South Korea Department of Energy Environment and Chemical Engineering Washington University in St. Louis St. Louis Missouri 63130 USA Institute of Materials Science and Engineering Washington University in St. Louis St. Louis Missouri 63130 USA Center for Nanophase Materials Sciences Oak Ridge National Laboratory Oak Ridge TN 37830 USA

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AAA + ATPase Thorase inhibits mTOR signaling through the disassembly of the mTOR complex 1

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Nature Communications 2022年第1期13卷 4836页

作者： Umanah, George K. E. Abalde-Atristain, Leire Khan, Mohammed Repon Mitra, Jaba Dar, Mohamad Aasif Chang, Melissa Tangella, Kavya McNamara, Amy Bennett, Samuel Chen, Rong Aggarwal, Vasudha Cortes, Marisol Worley, Paul F. Ha, Taekjip Dawson, Ted M. Dawson, Valina L. Neuroregeneration and Stem Cell Programs Institute for Cell Engineering Johns Hopkins University School of Medicine Baltimore 21205 MD United States Department of Neurology Johns Hopkins University School of Medicine Baltimore 21205 MD United States Cellular and Molecular Medicine Graduate Program Johns Hopkins University School of Medicine Baltimore 21205 MD United States Department of Materials Science and Engineering University of Illinois at Urbana-Champaign Urbana 61801 IL United States Department of Biophysics and Biophysical Chemistry Johns Hopkins University Baltimore 21205 MD United States Solomon H. Snyder Department of Neuroscience Johns Hopkins University School of Medicine Baltimore 21205 MD United States Departments of Biophysics and Biophysical Chemistry Biophysics and Biomedical Engineering JHU Howard Hughes Medical Institute Baltimore 21205 MD United States Department of Pharmacology and Molecular Sciences Johns Hopkins University School of Medicine Baltimore 21205 MD United States Department of Physiology Johns Hopkins University School of Medicine Baltimore 21205 MD United States Division of Neuroscience National Institute of Neurological Disorders and Stroke National Institutes of Health Bethesda MD United States Vollum Institute Oregon Health & Science University Portland 97239 OR United States

The mechanistic target of rapamycin (mTOR) signals through the mTOR complex 1 (mTORC1) and the mTOR complex 2 to maintain cellular and organismal homeostasis. Failure to finely tune mTOR activity results in metabolic dysregulation and disease. While there is substantial understanding of the molecular events leading mTORC1 activation at the lysosome, remarkably little is known about what terminates mTORC1 signaling. Here, we show that the AAA + ATPase Thorase directly binds mTOR, thereby orchestrating the disassembly and inactivation of mTORC1. Thorase disrupts the association of mTOR to Raptor at the mitochondria-lysosome interface and this action is sensitive to amino acids. Lack of Thorase causes accumulation of mTOR-Raptor complexes and altered mTORC1 disassembly/re-assembly dynamics upon changes in amino acid availability. The resulting excessive mTORC1 can be counteracted with rapamycin in vitro and in vivo. Collectively, we reveal Thorase as a key component of the mTOR pathway that disassembles and thus inhibits mTORC1. © 2022, The Author(s).

关键词： Cell signalling Lysosomes Mechanisms of disease

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Overcoming small-bandgap charge recombination in visible and NIR-light-driven hydrogen evolution by engineering the polymer photocatalyst structure

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Nature communications 2024年第1期15卷 707页

作者： Mohamed Hammad Elsayed Mohamed Abdellah Ahmed Zaki Alhakemy Islam M A Mekhemer Ahmed Esmail A Aboubakr Bo-Han Chen Amr Sabbah Kun-Han Lin Wen-Sheng Chiu Sheng-Jie Lin Che-Yi Chu Chih-Hsuan Lu Shang-Da Yang Mohamed Gamal Mohamed Shiao-Wei Kuo Chen-Hsiung Hung Li-Chyong Chen Kuei-Hsien Chen Ho-Hsiu Chou Department of Chemistry Faculty of Science Al-Azhar University Nasr City 11884 Cairo Egypt. Institute of Atomic and Molecular Sciences Academia Sinica Taipei 10617 Taiwan. Center for Condensed Matter Sciences National Taiwan University Taipei 10617 Taiwan. Department of Chemical Engineering National Tsing Hua University Hsinchu 300044 Taiwan. Department of Chemistry United Arab Emirates University Al Ain P.O. Box 15551 United Arab Emirates. Department of Chemistry Qena Faculty of Science South Valley University 83523 Qena Egypt. Chemical Physics and NanoLund Lund University 22100 Lund Sweden. Chemistry Department Faculty of Science Al-Azhar University Assiut 71542 Egypt. Sustainable Chemical Science and Technology Taiwan International Graduate Program Taipei Taiwan. Department of Applied Chemistry National Yang Ming Chiao Tung University Hsinchu 30010 Taiwan. Institute of Chemistry Academia Sinica 128 Sec 2 Academia Rd. Nankang Taipei 11529 Taiwan. Institute of Photonics Technologies National Tsing Hua University Hsinchu 300044 Taiwan. Center of Atomic Initiative for New Materials National Taiwan University Taipei 10617 Taiwan. Department of Chemical Engineering National Chung Hsing University Taichung 40227 Taiwan. Department of Materials and Optoelectronic Science Center for Functional Polymers and Supramolecular Materials National Sun Yat-Sen University Kaohsiung 804 Kaohsiung Taiwan. Department of Physics National Taiwan University Taipei 10617 Taiwan. Department of Chemical Engineering National Tsing Hua University Hsinchu 300044 Taiwan. hhchou@mx.nthu.edu.tw.

Designing an organic polymer photocatalyst for efficient hydrogen evolution with visible and near-infrared (NIR) light activity is still a major challenge. Unlike the common behavior of gradually increasing the charge recombination while shrinking the bandgap, we present here a series of polymer nanoparticles (Pdots) based on ITIC and BTIC units with different π-linkers between the acceptor-donor-acceptor (A-D-A) repeated moieties of the polymer. These polymers act as an efficient single polymer photocatalyst for H2 evolution under both visible and NIR light, without combining or hybridizing with other materials. Importantly, the difluorothiophene (ThF) π-linker facilitates the charge transfer between acceptors of different repeated moieties (A-D-A-(π-Linker)-A-D-A), leading to the enhancement of charge separation between D and A. As a result, the PITIC-ThF Pdots exhibit superior hydrogen evolution rates of 279 µmol/h and 20.5 µmol/h with visible (>420 nm) and NIR (>780 nm) light irradiation, respectively. Furthermore, PITIC-ThF Pdots exhibit a promising apparent quantum yield (AQY) at 700 nm (4.76%).

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Peptide Amphiphile Mediated Co-assembly for Nanoplasmonic Sensing

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Angewandte Chemie 2022年第4期135卷

作者： Dr. Zhicheng Jin Yi Li Dr. Ke Li Dr. Jiajing Zhou Justin Yeung Chuxuan Ling Wonjun Yim Tengyu He Dr. Yong Cheng Dr. Ming Xu Matthew N. Creyer Yu-Ci Chang Dr. Pavla Fajtová Dr. Maurice Retout Baiyan Qi Prof. Shuzhou Li Prof. Anthony J. O'Donoghue Prof. Jesse V. Jokerst Department of NanoEngineering University of California San Diego 9500 Gilman Drive La Jolla CA 92093 USA Institute of Materials Research and Engineering A*STAR (Agency for Science Technology and Research) Singapore 138634 Singapore School of Materials Science and Engineering Nanyang Technological University Singapore 639798 Singapore Department of Bioengineering University of California San Diego 9500 Gilman Drive La Jolla CA 92093 USA Materials Science and Engineering Program University of California San Diego 9500 Gilman Drive La Jolla CA 92093 USA Skaggs School of Pharmacy and Pharmaceutical Sciences University of California San Diego 9500 Gilman Drive La Jolla CA 92093 USA Department of Radiology University of California San Diego 9500 Gilman Drive La Jolla CA 92093 USA

Aromatic interactions are commonly involved in the assembly of naturally occurring building blocks, and these interactions can be replicated in an artificial setting to produce functional materials. Here we describe a colorimetric biosensor using co-assembly experiments with plasmonic gold and surfactant-like peptides (SLPs) spanning a wide range of aromatic residues, polar stretches, and interfacial affinities. The SLPs programmed in DDD−(ZZ) x −FFPC self-assemble into higher-order structures in response to a protease and subsequently modulate the colloidal dispersity of gold leading to a colorimetric readout. Results show the strong aggregation propensity of the FFPC tail without polar DDD head. The SLPs were specific to the target protease, i.e., M pro , a biomarker for SARS-CoV-2. This system is a simple and visual tool that senses M pro in phosphate buffer, exhaled breath condensate, and saliva with detection limits of 15.7, 20.8, and 26.1 nM, respectively. These results may have value in designing other protease testing methods.

关键词： Aromatic Interactions Colorimetric Test Main Protease Peptide Amphiphile Saliva

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Interferometric imaging, and beam-formed study of a moving Type IV Radio burst with LOFAR

arXiv

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arXiv 2022年

作者： Liu, Hongyu Zucca, Pietro Cho, Kyung-Suk Kumari, Anshu Zhang, Peijin Magdalenić, Jasmina Kim, Rok-Soon Kim, Sujin Kang, Juhyung Korea Astronomy and Space Science Institute 776 Daedeokdae-ro Yuseong-gu Daejeon34055 Korea Republic of Center for Magnetic Materials and Devices College of Physics and Electronic Engineering Qujing Normal University Qujing655011 China ASTRON The Netherlands Institute for Radio Astronomy Oude Hoogeveensedijk 4 Dwingeloo7991PD Netherlands University of Science and Technology 217 Gajeong-ro Yuseong-gu Daejeon34113 Korea Republic of Department of Physics University of Helsinki Pietari Kalmin katu 5 Helsinki00560 Finland Institute of Astronomy National Astronomical Observatory Bulgarian Academy of Sciences Sofia1784 Bulgaria Solar-Terrestrial Center of Excellence–SIDC Royal Observatory of Belgium Av. Circulaire 3 BrusselsB-1180 Belgium Center for mathematical Plasma Astrophysics Department of Mathematics KU Leuven Celestijnenlaan 200B LeuvenB-3001 Belgium Astronomy Program Department of Physics and Astronomy Seoul National University Seoul08826 Korea Republic of

Type IV radio burst has been studied for over 50 years. However, the specifics of the radio emission mechanisms is still an open question. In order to provide more information about the emission mechanisms, we studied a moving type IV radio burst with fine structures (spike group) by using the high resolution capability of Low-Frequency Array (LOFAR) on Aug 25, 2014 (SOLA-D-21-00188). We present a comparison of Nançay RadioHeliograph (NRH) and the first LOFAR imaging data of type IV radio burst. The degree of circular polarization (DCP) is calculated at frequencies in the range 20∼180 MHz using LOFAR data, and it was found that the value of DCP gradually increased during the event, with values of 10%∼20%. LOFAR interferometric data were combined with white light observations in order to track the propagation of this type IV. The kinematics shows a westward motion of the radio sources, slower than the CME leading edge. The dynamic spectrum of LOFAR shows a large number of fine structures with duration of less than 1s and high brightness temperature (TB), i.e. 1012∼1013 K. The gradual increase of DCP supports gyrosynchrotron emission as the most plausible mechanism for the type IV. However, coherent emissions such as Electron Cyclotron Maser (ECM) instability can be responsible for small scale fine structures. Countless fine structures altogether were responsible for such high TB © 2022, CC BY-NC-SA.

关键词： Interferometry

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Charge and spin degrees of freedom in A-site ordered YCu3Co4O12 and CaCu3Co4O12

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Physical Review B 2021年第11期103卷 115149-115149页

作者： Yi-Ying Chin Zhiwei Hu Yuichi Shimakawa Junye Yang Youwen Long A. Tanaka Liu Hao Tjeng Hong-Ji Lin Chien-Te Chen Department of Physics National Chung Cheng University Chiayi 62102 Taiwan Max Planck Institute for Chemical Physics of Solids Nöthnitzer Strasse 40 01187 Dresden Germany Institute for Chemical Research Kyoto University Kyoto 611-0011 Japan Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100190 China Songshan Lake Materials Laboratory Dongguan Guangdong 523808 China Quantum Matter Program Graduate School of Advanced Science and Engineering Hiroshima University Higashi-hiroshima 739-8530 Japan National Synchrotron Radiation Research Center (NSRRC) 101 Hsin-Ann Road Hsinchu 30076 Taiwan

Using soft x-ray absorption spectroscopy we were able to determine unambiguously the charge and spin states of the transition metal ions in stoichiometric YCu3Co4O12 and CaCu3Co4O12. The trivalent and low-spin nature of both the Cu and Co ions in YCu3Co4O12 makes this correlated system to be effectively a nonmagnetic band semiconductor. The substitution of Y by Ca produces formally tetravalent Co ions but the doped holes are primarily on the oxygen ligands. Concerning the spin degrees of freedom, the trivalent Co ions in YCu3Co4O12 remain low spin upon the Y-Ca substitution, very much unlike the La1−xSrxCoO3 system. The tetravalent Co ions in CaCu3Co4O12 are interestingly also in the low-spin state, which then explains the good electrical conductivity of CaCu3Co4O12 since charge exchange between neighboring Co3+ and Co4+ ions will not be hampered by the spin-blockade mechanism that otherwise would be in effect if the Co4+ and Co3+ spin quantum numbers were to differ by more than one-half. We infer that the stability of the Co low-spin state is related to the very short Co-O bond lengths.

关键词： Electrical conductivity Oxides Strongly correlated systems X-ray absorption spectroscopy

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