Phase diagram of a quantum Coulomb wire

We report the quantum phase diagram of a one-dimensional Coulomb wire obtained using the path integral Monte Carlo (PIMC) method. The exact knowledge of the nodal points of this system permits us to find the energy in an exact way, solving the sign problem which spoils fermionic calculations in higher dimensions. The results obtained allow for the determination of the stability domain, in terms of density and temperature, of the one-dimensional Wigner crystal. At low temperatures, the quantum wire reaches the quantum-degenerate regime, which is also described by the diffusion Monte Carlo method. Increasing the temperature the system transforms to a classical Boltzmann gas which we simulate using classical Monte Carlo. At large enough density, we identify a one-dimensional ideal Fermi gas which remains quantum up to higher temperatures than in two- and three-dimensional electron gases. The obtained phase diagram as well as the energetic and structural properties of this system are relevant to experiments with electrons in quantum wires and to Coulomb ions in one-dimensional confinement.Comment: 5 pages, 4 figure

Magnetic domain structure and dynamics in interacting ferromagnetic stacks with perpendicular anisotropy

The time and field dependence of the magnetic domain structure at magnetization reversal were investigated by Kerr microscopy in interacting ferromagnetic Co/Pt multilayers with perpendicular anisotropy. Large local inhomogeneous magnetostatic fields favor mirroring domain structures and domain decoration by rings of opposite magnetization. The long range nature of these magnetostatic interactions gives rise to ultra-slow dynamics even in zero applied field, i.e. it affects the long time domain stability. Due to this additionnal interaction field, the magnetization reversal under short magnetic field pulses differs markedly from the well-known slow dynamic behavior. Namely, in high field, the magnetization of the coupled harder layer has been observed to reverse more rapidly by domain wall motion than the softer layer alone.Comment: 42 pages including 17 figures. submitted to JA

Thermoelectrics, Photovoltaics and Thermal Photovoltaics for Powering ICT Devices and Systems

The conversion of heat into electricity through the thermoelectric effect and light into electricity through photovoltaic solar cells both allow useful amounts of power for a range of ICT systems from a few milli‐Watts (mW) for autonomous sensors up to kilo‐Watts (kW) for complete ICT computing or entertainment systems. Photovoltaics at the large scale can also be used to produce MW power stations suitable for the sustainable powering of high‐performance computing (HPC) and dataservers for cloud computing. This chapter provides a background to the physics of operation of both types of sustainable energy sources along with the fundamental limits of both technologies. The present performance is presented along with promising research directions to allow for a comparison of the useful power along with the limits for deployment of each approach to power ICT devices and systems. Finally, the developing field of thermal photovoltaics is reviewed, where the overall thermodynamic conversion efficiency of turning light into electricity and useful heat can be increased through the addition of thermoelectrics or heat transfer modules to a photovoltaic cell

Queilitis granulomatosa de Miescher

La queilitis granulomatosa es un raro proceso de etiología desconocida que se considera una forma oligosintomática del síndrome de Melkersson-Rosenthal. En este artículo presentamos un caso y hacemos una revisión de los procesos granulomatosos en la región oral, los procesos que cursan con hinchazón labial y del tratamiento de la queilitis granulomatosa

Second phalanx shortening osteotomy. An innovative technique for long second toe syndrome

AbstractLong second-toe syndrome, although frequent and disabling, has been little described. Current surgical techniques often lead to loss of function. Based on anatomical and biomechanical observations, the present study reports a second phalanx shortening osteotomy technique. The procedure is relatively non-invasive, involving self-stabilizing segment resection osteotomy of the second phalanx. Results for the first 23 feet undergoing the procedure were analyzed retrospectively. Assessment comprised clinical examination, radiography and AOFAS and FAAM scores. Mean follow-up was 19±9.9months. Second phalanx shortening osteotomy proved reliable, respecting the biomechanics of the toe

The assembly history of the nearest S0 galaxy NGC 3115 from its kinematics out to six half-light radii

Using new and archival data, we study the kinematic properties of the nearest field S0 galaxy, NGC 3115, out to $\sim6.5$ half-light radii ($R_\mathrm{e}$) from its stars (integrated starlight), globular clusters (GCs) and planetary nebulae (PNe). We find evidence of three kinematic regions with an inner transition at $\sim0.2\ R_\mathrm{e}$ from a dispersion-dominated bulge ($V_\mathrm{rot}/\sigma <1$) to a fast-rotating disk ($V_\mathrm{rot}/\sigma >1$), and then an additional transition from the disk to a slowly rotating spheroid at $\sim2-2.5\, R_\mathrm{e}$, as traced by the red GCs and PNe (and possibly by the blue GCs beyond $\sim5\, R_\mathrm{e}$). From comparison with simulations, we propose an assembly history in which the original progenitor spiral galaxy undergoes a gas-rich minor merger that results in the embedded kinematically cold disk that we see today in NGC 3115. At a later stage, dwarf galaxies, in mini mergers (mass-ratio $<$ 1:10), were accreted building-up the outer slowly rotating spheroid, with the central disk kinematics largely unaltered. Additionally, we report new spectroscopic observations of a sample of ultra-compact dwarfs (UCDs) around NGC 3115 with the Keck/KCWI instrument. We find that five UCDs are inconsistent with the general rotation field of the GCs, suggesting an \textit{ex-situ} origin for these objects, i.e. perhaps the remnants of tidally stripped dwarfs. A further seven UCDs follow the GC rotation pattern, suggesting an \textit{in-situ} origin and, possibly a GC-like nature.Comment: 22 pages (including 3 pages of Appendix material), 14 figures, published in MNRA

Thermoelectric cross-plane properties on p- and n-Ge/SixGe1-x superlattices

Silicon and germanium materials have demonstrated an increasing attraction for energy harvesting, due to their sustainability and integrability with complementary metal oxide semiconductor and micro-electro-mechanical-system technology. The thermoelectric efficiencies for these materials, however, are very poor at room temperature and so it is necessary to engineer them in order to compete with telluride based materials, which have demonstrated at room temperature the highest performances in literature [1]. Micro-fabricated devices consisting of mesa structures with integrated heaters, thermometers and Ohmic contacts were used to extract the cross-plane values of the Seebeck coefficient and the thermal conductivity from p- and n-Ge/SixGe1-x superlattices. A second device consisting in a modified circular transfer line method structure was used to extract the electrical conductivity of the materials. A range of p-Ge/Si0.5Ge0.5 superlattices with different doping levels was investigated in detail to determine the role of the doping density in dictating the thermoelectric properties. A second set of n-Ge/Si0.3Ge0.7 superlattices was fabricated to study the impact that quantum well thickness might have on the two thermoelectric figures of merit, and also to demonstrate a further reduction of the thermal conductivity by scattering phonons at different wavelengths. This technique has demonstrated to lower the thermal conductivity by a 25% by adding different barrier thicknesses per period

Highly asymmetric magnetic domain wall propagation due to coupling to a periodic pinning potential

Magneto-optical microscopy and magnetometry have been used to study 19 magnetization reversal in an ultrathin magnetically soft [Pt/Co]2 ferromagnetic film 20 coupled to an array of magnetically harder [Co/Pt]4 nanodots via a predominantly 21 dipolar interaction across a 3 nm Pt spacer. This interaction generates a spatially 22 periodic pinning potential for domain walls propagating through the continuous 23 magnetic film. When reversing the applied field with respect to the static nanodot 24 array magnetization orientation, strong asymmetries in the wall velocity and switching 25 fields are observed. Asymmetric switching fields mean that the hysteresis of the film is 26 characterized by a large bias field of dipolar origin which is linked to the wall velocity 27 asymmetry. This latter asymmetry, though large at low fields, vanishes at high fields 28 where the domains become round and compact. A field-polarity-controlled transition 29 from dendritic to compact faceted domain structures is also seen at low field and a 30 model is proposed to interpret the transition

Surface States in Template Synthesized Tin Oxide Nanoparticles

Tin–oxide nanoparticles with controlled narrow size distributions are synthesized while physically encapsulated inside silica mesoporous templates. By means of ultraviolet-visible spectroscopy, a redshift of the optical absorbance edge is observed. Photoluminescence measurements corroborate the existence of an optical transition at 3.2 eV. The associated band of states in the semiconductor gap is present even on template-synthesized nanopowders calcined at 800 °C, which contrasts with the evolution of the gap states measured on materials obtained by other methods. The gap states are thus considered to be surface localized, disappearing with surface faceting or being hidden by the surface-to-bulk ratio decrease