Ab-initio study of structure and dynamics properties of crystalline ice

We investigated the structural and dynamical properties of a tetrahedrally coordinated crystalline ice from first principles based on density functional theory within the generalized gradient approximation with the projected augmented wave method. First, we report the structural behaviour of ice at finite temperatures based on the analysis of radial distribution functions obtained by molecular dynamics simulations. The results show how the ordering of the hydrogen bonding breaks down in the tetrahedral network of ice with entropy increase in agreement with the neutron diffraction data. We also calculated the phonon spectra of ice in a 3x1x1 supercell by using the direct method. So far, due to the direct method used in this calculation, the phonon spectra is obtained without taking into account the effect of polarization arising from dipole-dipole interactions of water molecules which is expected to yield the splitting of longitudinal and transverse optic modes at the Gamma-point. The calculated longitudinal acoustic velocities from the initial slopes of the acoustic mode is in a reasonable agreement with the neutron scatering data. The analysis of the vibrational density of states shows the existence of a boson peak at low energy of translational region a characteristic common to amorphous systems.Comment: International symposium on structure and dynamics of heterogeneous system SDHS'0

POWER SYSTEMS OPERATION IMPROVEMENT CONSIDERING LOSS MINIMIZATION AND VOLTAGE STABILITY ENHANCEMENT

The challenge of energy and power losses during electrical energy transmission from generation plants to users is a major problem that cannot be over-emphasized. These Losses are inevitable because they are inherent in the conduction of electrical energy through physical means but can be minimized. This paper presents a VSC-PSO method for optimizing the power system operation by simultaneously minimizing the loss and enhancing the voltage stability which are the objective functions. The optimal power flow (OPF) was performed on IEEE 30-bus system with Newton Raphson algorithm implemented in MATLAB simulation software. The simulation results showed that the VSC-PSO approach performed more excellently with concurrent consideration of line loss reduction and voltage stability improvement when compared with other methods in literatur

Study of the Negative Magneto-Resistance of Single Proton-Implanted Lithium-Doped ZnO Microwires

The magneto-transport properties of single proton-implanted ZnO and of Li(7\%)-doped ZnO microwires have been studied. The as-grown microwires were highly insulating and not magnetic. After proton implantation the Li(7\%) doped ZnO microwires showed a non monotonous behavior of the negative magneto-resistance (MR) at temperature above 150 K. This is in contrast to the monotonous NMR observed below 50 K for proton-implanted ZnO. The observed difference in the transport properties of the wires is related to the amount of stable Zn vacancies created at the near surface region by the proton implantation and Li doping. The magnetic field dependence of the resistance might be explained by the formation of a magnetic/non magnetic heterostructure in the wire after proton implantation.Comment: 6 pages with 5 figure

Lattice dynamics and structural stability of ordered Fe3Ni, Fe3Pd and Fe3Pt alloys

We investigate the binding surface along the Bain path and phonon dispersion relations for the cubic phase of the ferromagnetic binary alloys Fe3X (X = Ni, Pd, Pt) for L12 and DO22 ordered phases from first principles by means of density functional theory. The phonon dispersion relations exhibit a softening of the transverse acoustic mode at the M-point in the L12-phase in accordance with experiments for ordered Fe3Pt. This instability can be associated with a rotational movement of the Fe-atoms around the Ni-group element in the neighboring layers and is accompanied by an extensive reconstruction of the Fermi surface. In addition, we find an incomplete softening in [111] direction which is strongest for Fe3 Ni. We conclude that besides the valence electron density also the specific Fe-content and the masses of the alloying partners should be considered as parameters for the design of Fe-based functional magnetic materials.Comment: Revised version, accepted for publication in Physical Review

Home-based intervention to test and start (HITS) protocol : a cluster-randomized controlled trial to reduce HIV-related mortality in men and HIV incidence in women through increased coverage of HIV treatment

Abstract: To realize the full benefits of treatment as prevention in many hyperendemic African contexts, there is an urgent need to increase uptake of HIV testing and HIV treatment among men to reduce the rate of HIV transmission to (particularly young) women. This trial aims to evaluate the effect of two interventions - microincentives and a tablet-based male-targeted HIV decision support application - on increasing home-based HIV testing and linkage to HIV care among men with the ultimate aim of reducing HIV-related mortality in men and HIV incidence in young women..

Advances in methods to obtain and characterise room temperature magnetic ZnO

We report the existence of magnetic order at room temperature in Li-doped ZnO microwires after low energy H+ implantation. The microwires with diameters between 0.3 and 10 μm were prepared by a carbothermal process. We combine spectroscopy techniques to elucidate the influence of the electronic structure and local environment of Zn, O, and Li and their vacancies on the magnetic response. Ferromagnetism at room temperature is obtained only after implanting H+ in Li-doped ZnO. The overall results indicate that low-energy proton implantation is an effective method to produce the necessary amount of stable Zn vacancies near the Li ions to trigger the magnetic order.Fil: Lorite, I.. Fakultät für Physik und Geowissenschaften; AlemaniaFil: Straube, Benjamin. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Física. Laboratorio de Física del Solido; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ohldag, H.. University Of Stanford; Estados UnidosFil: Kumar, P.. Fakultät für Physik und Geowissenschaften; AlemaniaFil: Villafuerte, Manuel Jose. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Física. Laboratorio de Física del Solido; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Esquinazi, P.. Fakultät für Physik und Geowissenschaften; AlemaniaFil: Rodriguez Torres, Claudia Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Instituto de Física La Plata; ArgentinaFil: Perez de Huelani, S.. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Física. Laboratorio de Física del Solido; ArgentinaFil: Antonov, V. N.. Institute for Metal Physics; Ucrania. Max Planck Institut für Mikrostrukturphysik; AlemaniaFil: Bekenov, L. V.. Institute for Metal Physics; Ucrania. Max Planck Institut für Mikrostrukturphysik; AlemaniaFil: Ernst, A.. Max Planck Institut für Mikrostrukturphysik; Alemania. Universitat Leipzig; AlemaniaFil: Hoffmann, M.. Max Planck Institut für Mikrostrukturphysik; Alemania. Martin Luther University Halle-Wittenberg; AlemaniaFil: Nayak, S. K.. Martin Luther University Halle-Wittenberg; AlemaniaFil: Adeagbo, W. A.. Martin Luther University Halle-Wittenberg; AlemaniaFil: Fischer, G.. Max Planck Institut für Mikrostrukturphysik; AlemaniaFil: Hergert. W.. Martin Luther University Halle-Wittenberg; Alemani

Oxygen-vacancy-induced local ferromagnetism as a driving mechanism in enhancing the magnetic response of ferrites

This work probes the relevance of oxygen vacancies in the formation of local ferromagnetic coupling between Fe ions at octahedral sites in zinc ferrites. This coupling gives rise to a ferrimagnetic ordering with the Curie temperatures above room temperature in an otherwise antiferromagnetic compound. This conclusion is based on experimental results from x-raymagnetic circular dichroismmeasurements at the Fe L2,3 edges and magnetization measurements performed on zinc ferrites, nanoparticles, and films, with different cation distributions and oxygen vacancy concentrations. Our observations are confirmed by density-functional-theory calculations and indicate that the enhanced ferrimagnetic response observed in some nominally nonmagnetic or antiferromagnetic ferrites can be taken as a further example of the defect-induced magnetism phenomenon.Fil: RodrÍguez Torres, Claudia Elena. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Pasquevich, Gustavo Alberto. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Mendoza Zélis, Pedro. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Golmar, Federico. CIC Nanogune; España. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pérez, Silvia Inés. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Física. Laboratorio de Física del Sólido; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Nayak, Sanjeev K.. Martin Luther University Halle-Wittenberg; AlemaniaFil: Adeagbo, Waheed A.. Martin Luther University Halle-Wittenberg; AlemaniaFil: Hergebert, Wolfram. Martin Luther University Halle-Wittenberg; AlemaniaFil: Hoffmann, Martin. Martin Luther University Halle-Wittenberg; Alemania. Institut Max Planck of Microstructure Physics; AlemaniaFil: Ernst, Arthur. Institut Max Planck of Microstructure Physics; AlemaniaFil: Esquinazi, P.. University of Leipzig; AlemaniaFil: Stewart, Silvana Jacqueline. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; Argentin