Domain wall propagation through spin wave emission

We theoretically study field-induced domain wall (DW) motion in an electrically insulating ferromagnet with hard- and easy-axis anisotropies. DWs can propagate along a dissipationless wire through spin wave emission locked into the known soliton velocity at low fields. In the presence of damping, the mode appears before the Walker breakdown field for strong out-of-plane magnetic anisotropy, and the usual Walker rigid-body propagation mode becomes unstable when the field is between the maximal-DW-speed field and Walker breakdown field.Comment: 4 pages, 4 figure

La gestion des ressources naturelles par les acteurs. Compte rendu des débats de la table ronde I

Les ressources naturelles sont sujettes à une évolution naturelle et à la gestion humaine. Dans la région des savanes d'Afrique de l'Ouest et du Centre, quelles évolutions sont constatées depuis 20 ans ? Quelles en sont les causes ? Comment sont-elles mesurées ? Quels jugements sont portés sur elles ? Quels objectifs la recherche et le développement doivent-il- s fixer et quelles sont les voies pour les atteindre ? Les manifestations de ces évolutions ont été discutées : ressources en eau, phénomènes d'érosion, désertification, richesse floristique ou faunistique, changements de paysage. L'évolution d'une ressource revêt plusieurs aspects : l'évolution réelle ou mesurée; l'évolution perçue par l'acteur selon l'usage de la ressource; l'évolution orientée par le discours. La quantification implique des mesures et des indicateurs ou prédicteurs. Des modèles de prédiction des processus de changement d'état doivent être créés. Le moteur principal de ces modifications serait l'évolution de l'activité des sociétés humaines; l'accroissement de la population n'explique pas tout; l'économie de marché a aussi changé les objectifs de production. L'adoption de systèmes de production plus durables doit être négociée entre tous les acteurs : cela passe par des politiques nationales ou régionales de développement local, par un accompagnement plurisdiciplinaire de la recherche et par une collaboration étroite entre les chercheurs et les acteurs. Quatre mots qualifient la recherche dans ce domaine : systémique, pluridisciplinaire, participative, finalisée

Acquired hemophilia as first manifestation of breast carcinoma in a man under long-term spironolactone therapy

A 69-year-old man under long-term spironolactone therapy (16 years) was hospitalized with spontaneous hematoma on the trunk and extremities. Coagulation studies disclosed an acquired hemophilia that was successfully treated with human factor VIII for a few days and immunosuppressive agents for several months. Physical examination revealed bilateral gynecomastia and an upper left quadrant breast nodule. Complete staging was unremarkable. Complete left mastectomy was performed. Histopathology showed invasive ductal carcinoma, expressing positivity for estrogen and progesterone receptors. The acquired hemophilia was considered to be a paraneoplasic syndrome. The question of a linkage between long-term spironolactone therapy and breast carcinoma is discusse

Conformal boundary loop models

We study a model of densely packed self-avoiding loops on the annulus, related to the Temperley Lieb algebra with an extra idempotent boundary generator. Four different weights are given to the loops, depending on their homotopy class and whether they touch the outer rim of the annulus. When the weight of a contractible bulk loop x = q + 1/q satisfies -2 < x <= 2, this model is conformally invariant for any real weight of the remaining three parameters. We classify the conformal boundary conditions and give exact expressions for the corresponding boundary scaling dimensions. The amplitudes with which the sectors with any prescribed number and types of non contractible loops appear in the full partition function Z are computed rigorously. Based on this, we write a number of identities involving Z which hold true for any finite size. When the weight of a contractible boundary loop y takes certain discrete values, y_r = [r+1]_q / [r]_q with r integer, other identities involving the standard characters K_{r,s} of the Virasoro algebra are established. The connection with Dirichlet and Neumann boundary conditions in the O(n) model is discussed in detail, and new scaling dimensions are derived. When q is a root of unity and y = y_r, exact connections with the A_m type RSOS model are made. These involve precise relations between the spectra of the loop and RSOS model transfer matrices, valid in finite size. Finally, the results where y=y_r are related to the theory of Temperley Lieb cabling.Comment: 28 pages, 19 figures, 2 tables. v2: added new section 3.2, amended figures 17-18, updated reference

Conformal field theory at central charge c=0: a measure of the indecomposability (b) parameters

A good understanding of conformal field theory (CFT) at c=0 is vital to the physics of disordered systems, as well as geometrical problems such as polymers and percolation. Steady progress has shown that these CFTs should be logarithmic, with indecomposable operator product expansions, and indecomposable representations of the Virasoro algebra. In one of the earliest papers on the subject, V. Gurarie introduced a single parameter b to quantify this indecomposability in terms of the logarithmic partner t of the stress energy tensor T. He and A. Ludwig conjectured further that b=-5/8 for polymers and b=5/6 for percolation. While a lot of physics may be hidden behind this parameter - which has also given rise to a lot of discussions - it had remained very elusive up to now, due to the lack of available methods to measure it experimentally or numerically, in contrast say with the central charge. We show in this paper how to overcome the many difficulties in trying to measure b. This requires control of a lattice scalar product, lattice Jordan cells, together with a precise construction of the state L_{-2}|0>. The final result is that b=5/6 for polymers. For percolation, we find that b=-5/8 within an XXZ or supersymmetric representation. In the geometrical representation, we do not find a Jordan cell for L_0 at level two (finite-size Hamiltonian and transfer matrices are fully diagonalizable), so there is no b in this case.Comment: 24 pages, 5 figure

BAM Austria: Arbeitskreis Bibliotheken, Archive, Museen Österreichs – Aktivitäten 2017

BAM Austria: Working Committee Libraries, Archives, Museums Austria came to the public in 2017 with two activities. On May 11, 2017, a seminar on "Open Access and Linked Open Data" (LOD) took place in Vienna, to which 25 representatives of libraries, archives and museums were invited. On September 13, 2017, a panel on "Digitalisation in libraries, archives and museums" was organized in the framework of the 33rd Austrian Library Day in Linz, in which about 90 people took part

Rectangular amplitudes, conformal blocks, and applications to loop models

In this paper we continue the investigation of partition functions of critical systems on a rectangle initiated in [R. Bondesan et al, Nucl.Phys.B862:553-575,2012]. Here we develop a general formalism of rectangle boundary states using conformal field theory, adapted to describe geometries supporting different boundary conditions. We discuss the computation of rectangular amplitudes and their modular properties, presenting explicit results for the case of free theories. In a second part of the paper we focus on applications to loop models, discussing in details lattice discretizations using both numerical and analytical calculations. These results allow to interpret geometrically conformal blocks, and as an application we derive new probability formulas for self-avoiding walks.Comment: 46 page

Spin-resolved fermi surface of the localized ferromagnetic Heusler compound Cu2MnAl measured with spin-polarized positron annihilation

We determined the bulk electronic structure in the prototypical Heusler compound Cu$_2$MnAl by measuring the Angular Correlation of Annihilation Radiation (2D-ACAR) using spin-polarized positrons. To this end, a new algorithm for reconstructing 3D densities from projections is introduced that allows us to corroborate the excellent agreement between our electronic structure calculations and the experimental data. The contribution of each individual Fermi surface sheet to the magnetization was identified, and summed to a total spin magnetic moment of $3.6\,\pm\,0.5\,\mu_B/\mathrm{f.u.}$

Insect haptoelectrical stimulation of Venus flytrap triggers exocytosis in gland cells

The Venus flytrap Dionaea muscipula captures insects and consumes their flesh. Prey contacting touch-sensitive hairs trigger traveling electrical waves. These action potentials (APs) cause rapid closure of the trap and activate secretory functions of glands, which cover its inner surface. Such prey-induced haptoelectric stimulation activates the touch hormone jasmonate (JA) signaling pathway, which initiates secretion of an acidic hydrolase mixture to decompose the victim and acquire the animal nutrients. Although postulated since Darwin’s pioneering studies, these secretory events have not been recorded so far. Using advanced analytical and imaging techniques, such as vibrating ion-selective electrodes, carbon fiber amperometry, and magnetic resonance imaging, we monitored stimulus-coupled glandular secretion into the flytrap. Trigger-hair bending or direct application of JA caused a quantal release of oxidizable material from gland cells monitored as distinct amperometric spikes. Spikes reminiscent of exocytotic events in secretory animal cells progressively increased in frequency, reaching steady state 1 d after stimulation. Our data indicate that trigger-hair mechanical stimulation evokes APs. Gland cells translate APs into touch-inducible JA signaling that promotes the formation of secretory vesicles. Early vesicles loaded with H⁺ and Cl⁻ fuse with the plasma membrane, hyperacidifying the “green stomach”-like digestive organ, whereas subsequent ones carry hydrolases and nutrient transporters, together with a glutathione redox moiety, which is likely to act as the major detected compound in amperometry. Hence, when glands perceive the haptoelectrical stimulation, secretory vesicles are tailored to be released in a sequence that optimizes digestion of the captured animal