193 research outputs found

    High Magnetic Field Microwave Conductivity of 2D Electrons in an Array of Antidots

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    We measure the high magnetic field (BB) microwave conductivity, Reσxx\sigma_{xx}, of a high mobility 2D electron system containing an antidot array. Reσxx\sigma_{xx} vs frequency (ff) increases strongly in the regime of the fractional quantum Hall effect series, with Landau filling 1/3<ν<2/31/3<\nu<2/3. At microwave ff, Reσxx\sigma_{xx} vs BB exhibits a broad peak centered around ν=1/2\nu=1/2. On the peak, the 10 GHz Reσxx\sigma_{xx} can exceed its dc-limit value by a factor of 5. This enhanced microwave conductivity is unobservable for temperature T≳0.5T \gtrsim 0.5 K, and grows more pronounced as TT is decreased. The effect may be due to excitations supported by the antidot edges, but different from the well-known edge magnetoplasmons.Comment: 4 pages, 3 figures, revtex

    Measurements of the Composite Fermion masses from the spin polarization of 2-D electrons in the region 1<ν<21<\nu<2

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    Measurements of the reflectivity of a 2-D electron gas are used to deduce the polarization of the Composite Fermion hole system formed for Landau level occupancies in the regime 1<\nu<2. The measurements are consistent with the formation of a mixed spin CF system and allow the density of states or `polarization' effective mass of the CF holes to be determined. The mass values at \nu=3/2 are found to be ~1.9m_{e} for electron densities of 4.4 x 10^{11} cm^{-2}, which is significantly larger than those found from measurements of the energy gaps at finite values of effective magnetic field.Comment: 4 pages, 3 fig

    Vertical Confinement and Evolution of Reentrant Insulating Transition in the Fractional Quantum Hall Regime

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    We have observed an anomalous shift of the high field reentrant insulating phases in a two-dimensional electron system (2DES) tightly confined within a narrow GaAs/AlGaAs quantum well. Instead of the well-known transitions into the high field insulating states centered around ν=1/5\nu = 1/5, the 2DES confined within an 80\AA-wide quantum well exhibits the transition at ν=1/3\nu = 1/3. Comparably large quantum lifetime of the 2DES in narrow well discounts the effect of disorder and points to confinement as the primary driving force behind the evolution of the reentrant transition.Comment: 5 pages, 4 figure

    Pulsed Magnetic Field Measurements of the Composite Fermion Effective Mass

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    Magnetotransport measurements of Composite Fermions (CF) are reported in 50 T pulsed magnetic fields. The CF effective mass is found to increase approximately linearly with the effective field B∗B^*, in agreement with our earlier work at lower fields. For a B∗B^* of 14 T it reaches 1.6me1.6m_e, over 20 times the band edge electron mass. Data from all fractions are unified by the single parameter B∗B^* for all the samples studied over a wide range of electron densities. The energy gap is found to increase like B∗\sqrt{B^*} at high fields.Comment: Has final table, will LaTeX without error

    Larkin-Ovchinnikov-Fulde-Ferrell state in quasi-one-dimensional superconductors

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    The properties of a quasi-one-dimensional (quasi-1D) superconductor with {\it an open Fermi surface} are expected to be unusual in a magnetic field. On the one hand, the quasi-1D structure of the Fermi surface strongly favors the formation of a non-uniform state (Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) state) in the presence of a magnetic field acting on the electron spins. On the other hand, a magnetic field acting on an open Fermi surface induces a dimensional crossover by confining the electronic wave-functions wave-functions along the chains of highest conductivity, which results in a divergence of the orbital critical field and in a stabilization at low temperature of a cascade of superconducting phases separated by first order transistions. In this paper, we study the phase diagram as a function of the anisotropy. We discuss in details the experimental situation in the quasi-1D organic conductors of the Bechgaard salts family and argue that they appear as good candidates for the observation of the LOFF state, provided that their anisotropy is large enough. Recent experiments on the organic quasi-1D superconductor (TMTSF)2_2ClO4_4 are in agreement with the results obtained in this paper and could be interpreted as a signature of a high-field superconducting phase. We also point out the possibility to observe a LOFF state in some quasi-2D organic superconductors.Comment: 24 pages+17 figures (upon request), RevTex, ORSAY-LPS-24109

    A mitochondrial half-size ABC transporter is involved in cadmium tolerance in Chlamydomonas reinhardtii

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    Five cadmium-sensitive insertional mutants, all affected at the CDS1 ('cadmium-sensitive 1') locus, have been previously isolated in the unicellular green alga Chlamydomonas reinhardtii. We here describe the cloning of the Cds1 gene (8314 bp with 26 introns) and the corresponding cDNA. The Cds1 gene, strongly induced by cadmium, encodes a putative protein (CrCds1) of 1062 amino acid residues that belongs to the ATM/HMT subfamily of half-size ABC transporters. This subfamily includes both vacuolar HMT-type proteins transporting phytochelatin-cadmium complexes from the cytoplasm to the vacuole and mitochondrial ATM-type proteins involved in the maturation of cytosolic Fe/S proteins. Unlike the Delta sphmt1 cadmium-sensitive mutant of Schizosaccharomyces pombe that lacks a vacuolar HMT-type transporter, the cds1 mutant accumulates a high amount of phytochelatin-cadmium complexes. By epitope tagging, the CrCds1 protein was localized in the mitochondria. Even though mitochondria of cds1 do not accumulate important amounts of 'free' iron, the mutant cells are hypersensitive to high iron concentrations. Our data show for the first time that a mitochondrial ATM-like transporter plays a major role in tolerance to cadmium.Peer reviewe

    New way of healing : experienced counsellors’ perceptions of the influence of ch’i-related exercises on counselling practice in Taiwan

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    This study examines how Taiwanese senior counsellors with substantial experience of ch’i-related exercise (CRE) perceived the influence of their regular CRE on their counselling practice. I am interested in the perceived influence of CRE on both self-care and professional practice. In this studyn this studyn this study n this study n this study n this study, CRE, CRE, CRE, CRE, CRE refers to any refers to any refers to any refers to any ch'i enhancing exercise that coordinates movement with breathing and inner concentration wherein ch'i is a first order concept used by practitioners and regarded by them as an embodiment of ideas related to human life and human existence and able to be experienced and refined through any ch'i related exercise. CRE is a set of practices and an intrinsic part of local culture in Taiwan which in recent years, has become popular practice in Taiwanese society. There are growing numbers of counselling professionals involved in regular CRE in recent years. Studies examining the effects of CRE indicate the benefits of CRE on practitioners' global health and personal growth. However, no previous study has investigated the influence of the long-term regular use of CRE on counsellors‟ self-care and counselling practice. The narrative research design for this study was developed from a post-structural theoretical perspective located in the domain of social constructivism. The data were co-constructed between the researcher and 12 senior Taiwanese counsellors with substantial CRE experience using a semi-structured in-depth interview approach. Interview data were analysed using the structure-based approach developed by William Labov in the field of socio-linguistics. The study reveals an overall benefit of regular involvement in CRE for practitioners' global wellbeing and personal growth counsellor' self-care. The research findings also reveals the potential of ch’i to be used as a way of expressing health and illness and a way of understanding in therapy and CRE to be lived out in therapy as an embodiment. I argue that collectively the narratives, as a whole, give evidence of an increasing integratin of the ideas and practices of ch’i into counselling practice in contemporary Taiwan. This might even make up a new form of integrated and culturally appropriate practice, what I term "a new way of healing." These are therapeutic practices which value the potential of CRE for counsellor's self-care and personal growth; recognize the integral whole of the human person; promote conscious use of the knowledge and experience of ch’i and CRE in therapy as an important aspect of the therapeutic use of self. Implications for practice such as the potential of CRE to be introduced into counsellor training programmes for counsellors' preparation or ongoing education are provided. Recommendations for future research such as the development of a new healing modality based on the research findings are offered

    Phylogenomic analysis of a 55.1 kb 19-gene dataset resolves a monophyletic Fusarium that includes the Fusarium solani Species Complex

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    Scientific communication is facilitated by a data-driven, scientifically sound taxonomy that considers the end-user¿s needs and established successful practice. In 2013, the Fusarium community voiced near unanimous support for a concept of Fusarium that represented a clade comprising all agriculturally and clinically important Fusarium species, including the F. solani species complex (FSSC). Subsequently, this concept was challenged in 2015 by one research group who proposed dividing the genus Fusarium into seven genera, including the FSSC described as members of the genus Neocosmospora, with subsequent justification in 2018 based on claims that the 2013 concept of Fusarium is polyphyletic. Here, we test this claim and provide a phylogeny based on exonic nucleotide sequences of 19 orthologous protein-coding genes that strongly support the monophyly of Fusarium including the FSSC. We reassert the practical and scientific argument in support of a genus Fusarium that includes the FSSC and several other basal lineages, consistent with the longstanding use of this name among plant pathologists, medical mycologists, quarantine officials, regulatory agencies, students, and researchers with a stake in its taxonomy. In recognition of this monophyly, 40 species described as genus Neocosmospora were recombined in genus Fusarium, and nine others were renamed Fusarium. Here the global Fusarium community voices strong support for the inclusion of the FSSC in Fusarium, as it remains the best scientific, nomenclatural, and practical taxonomic option availabl

    Fungal diversity notes 253–366: taxonomic and phylogenetic contributions to fungal taxa

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    Notes on 113 fungal taxa are compiled in this paper, including 11 new genera, 89 new species, one new subspecies, three new combinations and seven reference specimens. A wide geographic and taxonomic range of fungal taxa are detailed. In the Ascomycota the new genera Angustospora (Testudinaceae), Camporesia (Xylariaceae), Clematidis, Crassiparies (Pleosporales genera incertae sedis), Farasanispora, Longiostiolum (Pleosporales genera incertae sedis), Multilocularia (Parabambusicolaceae), Neophaeocryptopus (Dothideaceae), Parameliola (Pleosporales genera incertae sedis), and Towyspora (Lentitheciaceae) are introduced. Newly introduced species are Angustospora nilensis, Aniptodera aquibella, Annulohypoxylon albidiscum, Astrocystis thailandica, Camporesia sambuci, Clematidis italica, Colletotrichum menispermi, C. quinquefoliae, Comoclathris pimpinellae, Crassiparies quadrisporus, Cytospora salicicola, Diatrype thailandica, Dothiorella rhamni, Durotheca macrostroma, Farasanispora avicenniae, Halorosellinia rhizophorae, Humicola koreana, Hypoxylon lilloi, Kirschsteiniothelia tectonae, Lindgomyces okinawaensis, Longiostiolum tectonae, Lophiostoma pseudoarmatisporum, Moelleriella phukhiaoensis, M. pongdueatensis, Mucoharknessia anthoxanthi, Multilocularia bambusae, Multiseptospora thysanolaenae, Neophaeocryptopus cytisi, Ocellularia arachchigei, O. ratnapurensis, Ochronectria thailandica, Ophiocordyceps karstii, Parameliola acaciae, P. dimocarpi, Parastagonospora cumpignensis, Pseudodidymosphaeria phlei, Polyplosphaeria thailandica, Pseudolachnella brevifusiformis, Psiloglonium macrosporum, Rhabdodiscus albodenticulatus, Rosellinia chiangmaiensis, Saccothecium rubi, Seimatosporium pseudocornii, S. pseudorosae, Sigarispora ononidis and Towyspora aestuari. New combinations are provided for Eutiarosporella dactylidis (sexual morph described and illustrated) and Pseudocamarosporium pini. Descriptions, illustrations and / or reference specimens are designated for Aposphaeria corallinolutea, Cryptovalsa ampelina, Dothiorella vidmadera, Ophiocordyceps formosana, Petrakia echinata, Phragmoporthe conformis and Pseudocamarosporium pini. The new species of Basidiomycota are Agaricus coccyginus, A. luteofibrillosus, Amanita atrobrunnea, A. digitosa, A. gleocystidiosa, A. pyriformis, A. strobilipes, Bondarzewia tibetica, Cortinarius albosericeus, C. badioflavidus, C. dentigratus, C. duboisensis, C. fragrantissimus, C. roseobasilis, C. vinaceobrunneus, C. vinaceogrisescens, C. wahkiacus, Cyanoboletus hymenoglutinosus, Fomitiporia atlantica, F. subtilissima, Ganoderma wuzhishanensis, Inonotus shoreicola, Lactifluus armeniacus, L. ramipilosus, Leccinum indoaurantiacum, Musumecia alpina, M. sardoa, Russula amethystina subp. tengii and R. wangii are introduced. Descriptions, illustrations, notes and / or reference specimens are designated for Clarkeinda trachodes, Dentocorticium ussuricum, Galzinia longibasidia, Lentinus stuppeus and Leptocorticium tenellum. The other new genera, species new combinations are Anaeromyces robustus, Neocallimastix californiae and Piromyces finnis from Neocallimastigomycota, Phytophthora estuarina, P. rhizophorae, Salispina, S. intermedia, S. lobata and S. spinosa from Oomycota, and Absidia stercoraria, Gongronella orasabula, Mortierella calciphila, Mucor caatinguensis, M. koreanus, M. merdicola and Rhizopus koreanus in Zygomycota
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