What controls the large-scale magnetic fields of M dwarfs?

Observations of active M dwarfs show a broad variety of large-scale magnetic fields encompassing dipole-dominated and multipolar geometries. We detail the analogy between some anelastic dynamo simulations and spectropolarimetric observations of 23 M stars. In numerical models, the relative contribution of inertia and Coriolis force in the global force balance -estimated by the so-called local Rossby number- is known to have a strong impact on the magnetic field geometry. We discuss the relevance of this parameter in setting the large-scale magnetic field of M dwarfs.Comment: 4 pages, 3 figures, conference proceeding, IAUS 302 'Magnetic Fields Throughout the Stellar Evolution', (26-30 Aug 2013, Biarritz, France

Surfaces containing a family of plane curves not forming a fibration

We complete the classification of smooth surfaces swept out by a 1-dimensional family of plane curves that do not form a fibration. As a consequence, we characterize manifolds swept out by a 1-dimensional family of hypersurfaces that do not form a fibration.Comment: Author's post-print, final version published online in Collect. Mat

What controls the magnetic geometry of M dwarfs?

Context: observations of rapidly rotating M dwarfs show a broad variety of large-scale magnetic fields encompassing dipole-dominated and multipolar geometries. In dynamo models, the relative importance of inertia in the force balance -- quantified by the local Rossby number -- is known to have a strong impact on the magnetic field geometry. Aims: we aim to assess the relevance of the local Rossby number in controlling the large-scale magnetic field geometry of M dwarfs. Methods: we explore the similarities between anelastic dynamo models in spherical shells and observations of active M-dwarfs, focusing on field geometries derived from spectropolarimetric studies. To do so, we construct observation-based quantities aimed to reflect the diagnostic parameters employed in numerical models. Results: the transition between dipole-dominated and multipolar large-scale fields in early to mid M dwarfs is tentatively attributed to a Rossby number threshold. We interpret late M dwarfs magnetism to result from a dynamo bistability occurring at low Rossby number. By analogy with numerical models, we expect different amplitudes of differential rotation on the two dynamo branches.Comment: 4 pages, 4 figures, accepted for publication in A&

Life cycle studies of the hexose transporter of Plasmodium species and genetic validation of their essentiality

A Plasmodium falciparum hexose transporter (PfHT) has previously been shown to be a facilitative glucose and fructose transporter. Its expression in Xenopus laevis oocytes and the use of a glucose analogue inhibitor permitted chemical validation of PfHT as a novel drug target. Following recent re-annotations of the P. falciparum genome, other putative sugar transporters have been identified. To investigate further if PfHT is the key supplier of hexose to P. falciparum and to extend studies to different stages of Plasmodium spp., we functionally analysed the hexose transporters of both the human parasite P. falciparum and the rodent parasite Plasmodium berghei using gene targeting strategies. We show here the essential function of pfht for the erythrocytic parasite growth as it was not possible to knockout pfht unless the gene was complemented by an episomal construct. Also, we show that parasites are rescued from the toxic effect of a glucose analogue inhibitor when pfht is overexpressed in these transfectants. We found that the rodent malaria parasite orthologue, P. berghei hexose transporter (PbHT) gene, was similarly refractory to knockout attempts. However, using a single cross-over transfection strategy, we generated transgenic P. berghei parasites expressing a PbHT–GFP fusion protein suggesting that locus is amenable for gene targeting. Analysis of pbht-gfp transgenic parasites showed that PbHT is constitutively expressed through all the stages in the mosquito host in addition to asexual stages. These results provide genetic support for prioritizing PfHT as a target for novel antimalarials that can inhibit glucose uptake and kill parasites, as well as unveiling the expression of this hexose transporter in mosquito stages of the parasite, where it is also likely to be critical for survival

Charge order, orbital order, and electron localization in the Magneli phase Ti4O7

The metal-insulator transition of the Magneli phase Ti4O7 is studied by means of augmented spherical wave (ASW) electronic structure calculations as based on density functional theory and the local density approximation. The results show that the metal-insulator transition arises from a complex interplay of charge order, orbital order, and singlet formation of those Ti 3d states which mediate metal-metal bonding inside the four-atom chains characteristic of the material. Ti4O7 thus combines important aspects of Fe3O4 and VO2. While the charge ordering closely resembles that observed at the Verwey transition, the orbital order and singlet formation appear to be identical to the mechanisms driving the metal-insulator transition of vanadium dioxide.Comment: 11 pages, 4 figures, more information at http://www.physik.uni-augsburg.de/~eyert

Magnetic Field Effects on Neutron Diffraction in the Antiferromagnetic Phase of UPt3UPt_3

We discuss possible magnetic structures in UPt$_3$ based on our analysis of elastic neutron-scattering experiments in high magnetic fields at temperatures $T<T_N$. The existing experimental data can be explained by a single-{\bf q} antiferromagnetic structure with three independent domains. For modest in-plane spin-orbit interactions, the Zeeman coupling between the antiferromagnetic order parameter and the magnetic field induces a rotation of the magnetic moments, but not an adjustment of the propagation vector of the magnetic order. A triple-{\bf q} magnetic structure is also consistent with neutron experiments, but in general leads to a non-uniform magnetization in the crystal. New experiments could decide between these structures.Comment: 5 figures included in the tex

Análise ergonômica do trabalho agrícola familiar na produção de leite.

Este artigo trata da metodologia utilizada em uma intervenção ergonômica sobre organização do trabalho em Unidades de Produção Agrícola Familiar (UPAF) produtoras de leite de origem bovina, na região oeste da França. Apresenta-se a metodologia utilizada, uma combinação de jornadas de observação e análise do trabalho e jornadas de formação-ação. Discutem-se a Crônica de Ação e o Plano de Utilização das Instalações (PUI), bem como a utilização destes no processo de conscientização do agricultor sobre a complexidade de seu trabalho. Apresenta-se a análise da "supervisão do rebanho", devido ao seu alto grau de complexidade e importância para o desempenho da produção de leite, explorando de que forma certos arranjos espaciais podem favorecer as condições para a realização desta tarefa. Na análise do trabalho agrícola familiar privilegia-se o olhar complexo sobre a situação de trabalho, visando identificar os determinantes, as fontes de variabilidade e as estratégias adotadas

Interaction between vortices in models with two order parameters

The interaction energy and force between widely separated strings is analyzed in a field theory having applications to superconducting cosmic strings, the SO(5) model of high-temperature superconductivity, and solitons in nonlinear optics. The field theory has two order parameters, one of which is broken in the vacuum (giving rise to strings), the other of which is unbroken in the vacuum but which could nonetheless be broken in the core of the string. If this does occur, there is an effect on the energetics of widely separated strings. This effect is important if the length scale of this second order parameter is longer than that of the other fields in the problem.Comment: 11 pages, 3 figures. Minor changes in the text. Accepted for publication in Phys. Rev.

Hepatitis in Disseminated Bacillus Calmette-Guérin Infection

Local immunotherapy with an attenuated live strain of Mycobacterium bovis, bacillus Calmette-Guérin (BCG), is an effective and frequently used treatment for in situ transitional cell carcinoma (TCC) of the bladder. Success rates are high, and serious side effects are infrequent but can affect every organ system. A 79-year-old patient with recently diagnosed TCC who was treated with intravesical BCG for a recurrence after initial surgical treatment is reported. After unsuccessful attempts at bladder catheterization with the creation of a false passage for his third treatment, BCG was instilled via a suprapubic catheter the same day and again a week later. Two weeks after the third BCG instillation, the patient presented with profound lethargy and weakness to the point of not being able to get up out of a chair. He was febrile, anorexic, icteric and had hepatosplenomegaly. Disseminated BCG infection was suspected on the basis of history, clinical examination and a liver biopsy that showed noncaseating granulomatous hepatitis. Empirical treatment was started with antituberculous combination therapy. A short course of an oral corticosteroid was given. Clinical improvement was marked and sustained so that the patient could be discharged home for the full six-month course of his treatment. Disseminated BCG infection with granulomatous hepatitis can be severe and life-threatening in cases where a large intravascular inoculum of BCG may have been given inadvertently

Superconductivity in the Ferroquadrupolar State in the Quadrupolar Kondo Lattice PrTi2_2Al20_{20}

The cubic compound PrTi$_2$Al$_{20}$ is a quadrupolar Kondo lattice system that exhibits quadrupolar ordering due to the non-Kramers $\Gamma_3$ ground doublet and has strong hybridization between $4f$ and conduction electrons. Our study using high-purity single crystal reveals that PrTi$_2$Al$_{20}$ exhibits type-II superconductivity at $T_{\rm c} = 200$ mK in the nonmagnetic ferroquadrupolar state. The superconducting critical temperature and field phase diagram suggests moderately enhanced effective mass of $m^*/m_0 \sim 16$