Quantum fluctuations stabilize skyrmion textures

We study the quantum spin waves associated to skyrmion textures. We show that the zero-point energy associated to the quantum spin fluctuations of a noncollinear spin texture produce Casimir-like magnetic fields. We study the effect of these Casimir fields on the topologically protected noncollinear spin textures known as skyrmions. In a Heisenberg model with Dzyalonshinkii-Moriya interactions, chosen so the classical ground state displays skyrmion textures, we calculate the spin-wave spectrum, using the Holstein-Primakoff approximation, and the associated zero-point energy, to the lowest order in the spin-wave expansion. Our calculations are done both for the single-skyrmion case, for which we obtain a discrete set of skyrmion bound states, as well as for the skyrmion crystal, for which the resulting spectrum gives the spin-wave bands. In both cases, our calculations show that the Casimir magnetic field contributes up to 10% of the total Zeeman energy necessary to delete the skyrmion texture with an applied field.The authors acknowledge funding from Fondecyt Grant No. 1150072, Grant No. ICM P10-061-F by Fondo de Innovación para la Competitividad-MINECON, and Anillo Grant No. ACT 1117. A.S.N. also acknowledges support from Financiamiento Basal para Centros Científicos y Tecnológicos de Excelencia, under Project No. FB 0807(Chile)

Quantum theory of spin waves in finite chiral spin chains

We calculate the effect of spin waves on the properties of finite-size spin chains with a chiral spin ground state observed on biatomic Fe chains deposited on iridium(001). The system is described with a Heisenberg model supplemented with a Dzyaloshinskii-Moriya coupling and a uniaxial single ion anisotropy that presents a chiral spin ground state. Spin waves are studied using the Holstein-Primakoff boson representation of spin operators. Both the renormalized ground state and the elementary excitations are found by means of Bogoliubov transformation, as a function of the two variables that can be controlled experimentally, the applied magnetic field and the chain length. Three main results are found. First, because of the noncollinear nature of the classical ground state, there is a significant zero-point reduction of the ground-state magnetization of the spin spiral. Second, there is a critical external field from which the ground state changes from chiral spin ground state to collinear ferromagnetic order. The character of the two lowest-energy spin waves changes from edge modes to confined bulk modes over this critical field. Third, in the spin-spiral state, the spin-wave spectrum exhibits oscillatory behavior as function of the chain length with the same period of the spin helix.The authors thank funding from grants from Fondecyt (Grant No. 1110271), Fondo de Innovación para la Competitividad-MINECON (Grant No. ICM P10-061-F), and Anillo ACT (Grant No. 1117). A.S.N. also acknowledges support from Financiamiento Basal para Centros Científicos y Tecnológicos de Excelencia under Project No. FB 0807 (Chile)

Berry phase in homogeneous K\"ahler manifolds with linear Hamiltonians

We study the total (dynamical plus geometrical (Berry)) phase of cyclic quantum motion for coherent states over homogeneous K\"ahler manifolds X=G/H, which can be considered as the phase spaces of classical systems and which are, in particular cases, coadjoint orbits of some Lie groups G. When the Hamiltonian is linear in the generators of a Lie group, both phases can be calculated exactly in terms of {\em classical} objects. In particular, the geometric phase is given by the symplectic area enclosed by the (purely classical) motion in the space of coherent states.Comment: LaTeX fil

Pharmacogenetics of ugt genes in North African populations

Cytochrome P450 (CYP450), sulfotransferase (SULT), and glucuronidase (UGT) enzymes play roles in the phase I and phase II metabolism of most clinically prescribed drugs. As polymorphisms in these genes may alter enzyme activities, most prescribed drugs will differ in their efficacy and side effects. In prior work, we showed that besides polymorphisms in CYP450, those in SULT and UGT also give rise to different serum levels of some drug metabolites than detected in wild-type carriers of the genes [1]. [...

Natación artística en niñas: antropometría, genotipo y rendimiento deportivo.

En cada deporte es importante optimizar peso y composición corporal y la genética y los datos antropométricos pueden influir en rendimiento deportivo y salud, sobre todo en deportistas menores. Este estudio analiza 60 nadadoras artísticas entre 9 y 17 años, divididas en tres grupos de edad: ≤12, 13-15 y 16-17 años. Se realizó un análisis de medidas antropométricas, edad de menarquia, genotipo relacionado con rendimiento (gen ACTN3) y resultados deportivos, con objetivo de relacionar estos parámetros entre sí en los grupos de edad. Las nadadoras de mayor edad mostraron tendencia a portar el genotipo heterocigoto RX de ACTN3. En este estudio, la práctica de este deporte podría tener impacto en índice de masa corporal, pliegue tricipital, peso y edad de menarquia. La mayor prevalencia del genotipo heterocigoto ACTN3 R577X podría ofrecer una ventaja, pero el rendimiento en competición de las nadadoras artísticas tuvo poca relación con sus medidas antropométricas.post-print680 K

The Maser-emitting Structure and Time Variability of the SiS Lines J =14-13 and 15-14 in IRC+10216

2 pags., 1 tab. -- Why Galaxies Care About AGB Stars: A Continuing Challenge through Cosmic Time Proceedings IAU Symposium No. 343, 2019 F. Kerschbaum, M. Groenewegen & H. Olofsson, eds.AGB stars are important contributors of processed matter to the ISM. However, the physical and chemical mechanisms involved in its ejection are still poorly known. This process is expected to have remarkable effects in the innermost envelope, where the dust grains are formed, the gas is accelerated, the chemistry is active, and the radiative excitation becomes important. A good tracer of this region in C-rich stars is SiS, an abundant refractory molecule that can display maser lines, very sensitive to changes in the physical conditions. We present high angular resolution interferometer observations (HPBW â‰30.″.25) of the v = 0 J = 14-13 and 15-14 SiS maser lines towards the archetypal AGB star IRC+10216, carried out with CARMA and ALMA to explore the inner 1> region around the central star. We also present an ambitious monitoring of these lines along one single pulsation period carried out with the IRAM 30 m telescope.The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013)/ ERC grant agreement n◦ 610256: NANOCOSMO

Rational design of polyarginine nanocapsules intended to help peptides overcoming intestinal barriers

The aim of this work was to rationally design and characterize nanocapsules (NCs) composed of an oily core and a polyarginine (PARG) shell, intended for oral peptide delivery. The cationic polyaminoacid, PARG, and the oily core components were selected based on their penetration enhancing properties. Insulin was adopted as a model peptide to assess the performance of the NCs. After screening numerous formulation variables, including different oils and surfactants, we defined a composition consisting of oleic acid, sodium deoxycholate (SDC) and Span 80. This selected NCs composition, produced by the solvent displacement technique, exhibited the following key features: (i) an average size of 180 nm and a low polydispersity (0.1), (ii) a high insulin association efficacy (80–90% AE), (iii) a good colloidal stability upon incubation in simulated intestinal fluids (SIF, FaSSIF-V2, FeSSIF-V2), and (iv) the capacity to control the release of the associated insulin for > 4 h. Furthermore, using the Caco-2 model cell line, PARG nanocapsules were able to interact with the enterocytes, and reversibly modify the TEER of the monolayer. Both cell adhesion and membrane permeabilization could account for the pronounced transport of the NCs-associated insulin (3.54%). This improved interaction was also visualized by confocal fluorescent microscopy following oral administration of PARG nanocapsulesto mice. Finally, in vivo efficacy studies performed in normoglycemic rats showed a significant decrease in their plasma glucose levels after treatment. In conclusion, here we disclose key formulation elements for making possible the oral administration of peptidesThis work was supported by the European TRANS-INT Consortium, which received funding from the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement No. 281035. Z. Niu also would like to thank the Chinese Scholarship Council for his scholarshipS

Presentation of a case with Wellens syndrome

This case report is about a 56-year-old male, farm worker with a history of being a smoker and suffering from high blood pressure, who was admitted at the Cardiology Care Department with the diagnosis of coronary artery disease –unstable angina–, because of chest pain related to physical effort and changes in the appearance threshold. Rest-electrocardiogram, painless, shows deep, symmetric negative T waves in anterior wall, without enzyme elevation; but during admission the patient evolves quickly, clinically and electrically, to an extensive anterior wall acute myocardial infarction, without responding to the fibrinolytic reperfusion therapy, and showing a ventricular tachycardia degenerating into ventricular fibrillation. There was no response to the maneuvers of cardiovascular resuscitation, thus, he dies. It is diagnosed postmortem as a Wellens syndrome, because necropsy showed severe atherosclerotic disease of the proximal segment of the left anterior descending coronary artery with extensive anterior transmural infarction

A holographic map of action onto entropy

We propose a holographic correspondence between the action integral I describing the mechanics of a finite number of degrees of freedom in the bulk, and the entropy S of the boundary (a holographic screen) enclosing that same volume. The action integral must be measured in units of (i times) Planck's constant, while the entropy must be measured in units of Boltzmann's constant. In this way we are led to an intriguing relation between the second law of thermodynamics and the uncertainty principle of quantum mechanics.Comment: 12 pages. arXiv admin note: substantial text overlap with arXiv:1107.189