A junction of three quantum wires: restoring time-reversal symmetry by interaction

We investigate transport of correlated fermions through a junction of three one-dimensional quantum wires pierced by a magnetic flux. We determine the flow of the conductance as a function of a low-energy cutoff in the entire parameter space. For attractive interactions and generic flux the fixed point with maximal asymmetry of the conductance is the stable one, as conjectured recently. For repulsive interactions and arbitrary flux we find a line of stable fixed points with vanishing conductance as well as stable fixed points with symmetric conductance (4/9)(e^2/h).Comment: 5 pages, 3 figures, version accepted for publication in Phys. Rev. Let

Refugee migrants as agents of change: Strategies for improved livelihoods and self-reliance

Although many refugees leave their home countries with a certain level of uncertainty concerning their survival in the host country, they are hopeful of improving their livelihood and thus being self-reliant. They seize available opportunities in order to start a new life. In doing so, refugees move beyond solely depending on charity actions, having devised survival mechanisms in their new setting by means of self-reliant strategies. This article, therefore, looks at the refugee migrants as agents of change in view of the self-reliance strategies they use for survival. Furthermore, the article points to the courage of the refugees in the host country by presenting qualitative evidence on how refugees’ livelihood strategies have contributed to the improvement of their own well-being in general and, in particular, that of some locals. The data for this study were gathered using in-depth interviews with refugees living in Cape Town, South Africa. Intradisciplinary and/or interdisciplinary implications: This paper is transdisciplinary in that it presents an ecclesial response to the global challenges facing the refugee community. This is because it aims at transforming the painful experiences of the refugees into opportunities for improved livelihoods and holistic well-being. The paper further depicts how practical theology informs understandings of the phenomenological techniques in an attempt to explore the rhythms of social life from the perspective of the issue under investigation. The article is, therefore, a theological underpinning that informs development practitioners and practical theologians on how to efficiently respond to the pressing needs of refugees using hope as an available resource. In this manner, the article presents strategies that would assist policy-makers in devising sustainable policies and programmes that aim at improving refugees’ livelihoods

Heavy Superheated Droplet Detectors as a Probe of Spin-independent WIMP Dark Matter Existence

At present, application of Superheated Droplet Detectors (SDDs) in WIMP dark matter searches has been limited to the spin-dependent sector, owing to the general use of fluorinated refrigerants which have high spin sensitivity. Given their recent demonstration of a significant constraint capability with relatively small exposures and the relative economy of the technique, we consider the potential impact of heavy versions of such devices on the spin-independent sector. Limits obtainable from a $\mathrm{CF_{3}I}$-loaded SDD are estimated on the basis of the radiopurity levels and backgrounds already achieved by the SIMPLE and PICASSO experiments. With 34 kgd exposure, equivalent to the current CDMS, such a device may already probe to below 10$^{-6}$ pb in the spin-independent cross section.Comment: 9 pages, 4 figures, accepted Phys. Rev.

Commensurate-Incommensurate transition in the melting process of the orbital ordering in Pr0.5Ca0.5MnO3: neutron diffraction study

The melting process of the orbital order in Pr0.5Ca0.5MnO3 single crystal has been studied in detail as a function of temperature by neutron diffraction. It is demonstrated that a commensurate-incommensurate (C-IC) transition of the orbital ordering takes place in a bulk sample, being consistent with the electron diffraction studies. The lattice structure and the transport properties go through drastic changes in the IC orbital ordering phase below the charge/orbital ordering temperature Tco/oo, indicating that the anomalies are intimately related to the partial disordering of the orbital order, unlike the consensus that it is related to the charge disordering process. For the same T range, partial disorder of the orbital ordering turns on the ferromagnetic spin fluctuations which were observed in a previous neutron scattering study.Comment: 5 pages, 2 figures, REVTeX, to be published in Phys. Rev.

Ac conductivity and dielectric properties of CuFe1−xCrxO2 : Mg delafossite

The electrical and dielectric properties of CuFe(1−x)Cr(x)O(2) (0 ≤ x ≤ 1) powders, doped with 3% of Mg and prepared by solid-state reaction, were studied by broadband dielectric spectroscopy in the temperature range from −100 to 150 °C. The frequency-dependent electrical and dielectric data have been discussed in the framework of a power law conductivity and complex impedance and dielectric modulus. At room temperature, the ac conductivity behaviour is characteristic of the charge transport in CuFe1−xCrxO2 powders. The substitution of Fe3+ by Cr3+ results in an increase in dc conductivity and a decrease in the Cu+–Cu+ distance. Dc conductivity, characteristic onset frequency and Havriliak–Negami characteristics relaxation times are thermally activated above −40 °C for x = 0.835. The associated activation energies obtained from dc and ac conductivity and from impedance and modulus losses are similar and show that CuFe1−xCrxO2 delafossite powders satisfy the BNN relation. Dc and ac conductivities have the same transport mechanism, namely thermally activated nearest neighbour hopping and tunnelling hopping above and below −40 °C, respectively

Junctions of one-dimensional quantum wires - correlation effects in transport

We investigate transport of spinless fermions through a single site dot junction of M one-dimensional quantum wires. The semi-infinite wires are described by a tight-binding model. Each wire consists of two parts: the non-interacting leads and a region of finite extent in which the fermions interact via a nearest-neighbor interaction. The functional renormalization group method is used to determine the flow of the linear conductance as a function of a low-energy cutoff for a wide range of parameters. Several fixed points are identified and their stability is analyzed. We determine the scaling exponents governing the low-energy physics close to the fixed points. Some of our results can already be derived using the non-self-consistent Hartree-Fock approximation.Comment: version accepted for publication in Phys. Rev. B, 14 pages, 7 figures include

Preparation of delafossite CuFeO2 thin films by rf-sputtering on conventional glass substrate

CuFeO2 CuFeO2 is a delafossite-type compound and is a well known p-type semiconductor. The growth of delafossite CuFeO2 thin films on conventional glass substrate by radio-frequency sputtering is reported. The deposition, performed at room temperature leads to an amorphous phase with extremely low roughness and high density. The films consisted of a well crystallized delafossite CuFeO2 after heat treatment at 450 °C in inert atmosphere. The electrical conductivity of the film was 1 mS/cm. The direct optical band gap was estimated to be 2 eV

Preparation and characterization of the defect–conductivity relationship of Ga-doped ZnO thin films deposited by nonreactive radio-frequency–magnetron sputtering

Ga-doped ZnO (ZnO:Ga) thin films were prepared by radio-frequency–magnetron sputtering on conventional glass substrates at room temperature. The structural, electrical, and optical properties of these films as a function of argon pressure and film thicknesses were studied. All the films crystallized with the hexagonal wurtzite structure. The x-ray diffraction studies show that the ZnO:Ga films are highly oriented with their crystallographic c-axis perpendicular to the substrate. We discuss a methodology of using a “standardized platform” for comparison of samples deposited at different pressures, which provides an insight into the defect–resistivity relationship of each sample with respect to their microstructure. After the first annealing, the electrical properties of the films are dependent on the atmosphere used during postdeposition annealing treatment. A resistivity of 2.5 × 10−3 Ω · cm was obtained after vacuum annealing, and the films became an insulator after air annealing. The reproducibility of this treatment was verified. The average transmittance of all ZnO:Ga thin films is more than 85% in the visible range

La Perte des Savoirs et Pratiques Endogenes: Risques pour l’Environnement Naturel du Territoire Blouf en Basse Casamance (Senelgal)

Au Sénégal, l’environnement naturel en général subit de nombreuses agressions (sécheresse, pollution, destruction des habitats et surexploitation) qui sont autant de causes de perte de la biodiversité. Pourtant, en dépit de ces multiples agressions, il existe encore des endroits en Basse Casamance où l’on peut trouver une biodiversité remarquable. Entre autres milieux, figurent les sites naturels sacrés qui jouissent d’une protection fondée sur des règles traditionnelles, lesquelles reposent sur des savoirs locaux transmis à travers les générations. Les savoirs locaux identifiés ainsi que de nombreuses pratiques locales contribuent à la conservation des ressources naturelles, malgré les pressions multiples. Ces ressources ont des valeurs culturelles, spirituelles et matérielles remarquables. Aujourd’hui, la prise de conscience par la communauté scientifique de l’intérêt de ces savoirs endogènes pour la conservation, pose le problème de leur maintien. Le présent article fait le point sur cette question sur la base d’une recherche bibliographique et d’enquêtes essentiellement qualitatif menées à l’aide de questionnaires et des focus groupes qui ont permis de faire un état des lieux sur les savoirs et pratiques qui subsistent et qui sont bénéfiques pour la conservation. Les interviews sont réalisées auprès de 111 ménages de la contrée Blouf.   In Senegal, the natural environment in general suffers from numerous aggressions (drought, pollution, destruction of habitats and overexploitation) which are as many causes of loss of biodiversity. Yet, despite these multiple attacks on the environment, there are still places in Lower Casamance where we can find remarkable biodiversity. Among other environments are the sacred natural sites that enjoy protection based on traditional rules, which rely on local knowledge passed down through the generations. The knowledge identified in the biophysical and sociocultural environments as well as many local practices contribute to the conservation of marine and coastal natural resources, despite the multiple pressures. These resources have remarkable cultural, spiritual and material values. Today, with the scientific community's awareness of the interest of this endogenous knowledge for conservation, its maintenance is necessary for the well-being of local communities whose survival depends directly on resources. This article reviews this question on the basis of a bibliographic search and essentially qualitative surveys using questionnaires and focus groups that allowed us to take stock of the knowledge and practices remain and are beneficial for conservation. Interviews are conducted with 111 households in the Blouf region

La Perte de Savoirs et de Pratiques Endogenes: Risques pour l’Envitonnement Naturel du Territoire Blouf en Basse Casamance (Senegal)

Au Sénégal, l’environnement naturel en général subit de nombreuses agressions (sécheresse, pollution, destruction des habitats et surexploitation) qui sont autant de causes de perte de la biodiversité. Pourtant, en dépit de ces multiples agressions, il existe encore des endroits en Basse Casamance où l’on peut trouver une biodiversité remarquable. Entre autres milieux, figurent les sites naturels sacrés qui jouissent d’une protection fondée sur des règles traditionnelles, lesquelles reposent sur des savoirs locaux transmis à travers les générations. Les savoirs locaux identifiés ainsi que de nombreuses pratiques locales contribuent à la conservation des ressources naturelles, malgré les pressions multiples. Ces ressources ont des valeurs culturelles, spirituelles et matérielles remarquables. Aujourd’hui, la prise de conscience par la communauté scientifique de l’intérêt de ces savoirs endogènes pour la conservation, pose le problème de leur maintien. Le présent article fait le point sur cette question à partir d’une recherche bibliographique et d’enquêtes essentiellement qualitatif menées à l’aide d’un guide d’entretien et des focus groupes qui ont permis de faire un état des lieux sur les savoirs et pratiques qui subsistent et qui sont bénéfiques pour la conservation.   In Senegal, the natural environment, in general, suffers from numerous aggressions (drought, pollution, destruction of habitats, and overexploitation) which are as many causes of loss of biodiversity. Yet, despite these multiple attacks on the environment, there are still places in Lower Casamance where we can find remarkable biodiversity. Among other environments are the sacred natural sites that enjoy protection based on traditional rules, which rely on local knowledge passed down through the generations. The knowledge identified in the biophysical and sociocultural environments as well as many local practices contribute to the conservation of marine and coastal natural resources, despite the multiple pressures. These resources have remarkable cultural, spiritual, and material values. Today, with the scientific community's awareness of the interest of this endogenous knowledge for conservation, its maintenance is necessary for the well-being of local communities whose survival depends directly on resources. This article reviews this question on the basis of a bibliographic search and essentially qualitative surveys using interview guides and focus groups that allowed us to take stock of the knowledge and practices that remain and are beneficial for conservation