Detailed analysis of radiation data from the Gemini 4 and Gemini 7 proton-electron spectrometer experiments Final report, 13 Jun. 1967 - 30 Dec. 1968

Detailed analysis of radiation data from Gemini 4 and 7 proton-electron spectrometer experiment

Magnetic ground state and magnon-phonon interaction in multiferroic h-YMnO3_3

Inelastic neutron scattering has been used to study the magneto-elastic excitations in the multiferroic manganite hexagonal YMnO$_3$. An avoided crossing is found between magnon and phonon modes close to the Brillouin zone boundary in the $(a,b)$-plane. Neutron polarization analysis reveals that this mode has mixed magnon-phonon character. An external magnetic field along the $c$-axis is observed to cause a linear field-induced splitting of one of the spin wave branches. A theoretical description is performed, using a Heisenberg model of localized spins, acoustic phonon modes and a magneto-elastic coupling via the single-ion magnetostriction. The model quantitatively reproduces the dispersion and intensities of all modes in the full Brillouin zone, describes the observed magnon-phonon hybridized modes, and quantifies the magneto-elastic coupling. The combined information, including the field-induced magnon splitting, allows us to exclude several of the earlier proposed models and point to the correct magnetic ground state symmetry, and provides an effective dynamic model relevant for the multiferroic hexagonal manganites.Comment: 12 pages, 10 figure

Relativistic Landau quantization for a neutral particle

In this contribution we study the Landau levels arising within the relativistic quantum dynamics of a neutral particle which possesses a permanent magnetic dipole moment interacting with an external electric field. We consider the Aharonov-Casher coupling of magnetic dipole to the electric field to investigate an an analog of Landau quantization in this system and solve the Dirac equation for two different field configurations. The eigenfunctions and eigenvalues of Hamiltonian in both cases are obtained.Comment: 9 pages, no figure

Proton-electron spectrometer experiments on Gemini-4 and Gemini-7 Final report, 27 May 1963 - 30 Sep. 1966

Fluxes and spectra of electrons and protons in atmosphere measured by spectrometer experiments on Gemini spacecraf

Noninertial effects on a Dirac neutral particle inducing an analogue of the Landau quantization in the cosmic string spacetime

We discuss the behaviour of external fields that interact with a Dirac neutral particle with a permanent electric dipole moment in order to achieve relativistic bound states solutions in a noninertial frame and in the presence of a topological defect spacetime. We show that the noninertial effects of the Fermi-Walker reference frame induce a radial magnetic field even in the absence of magnetic charges, which is influenced by the topology of the cosmic string spacetime. We then discuss the conditions that the induced fields must satisfy to yield the relativistic bound states corresponding to the Landau-He-McKellar-Wilkens quantization in the cosmic string spacetime. Finally we obtain the Dirac spinors for positive-energy solutions and the Gordon decomposition of the Dirac probability current.Comment: 15 pages, no figure, this paper will be published in volume 42 of the Brazilian Journal of Physic

Monte-Carlo study of scaling exponents of rough surfaces and correlated percolation

We calculate the scaling exponents of the two-dimensional correlated percolation cluster's hull and unscreened perimeter. Correlations are introduced through an underlying correlated random potential, which is used to define the state of bonds of a two-dimensional bond percolation model. Monte-Carlo simulations are run and the values of the scaling exponents are determined as functions of the Hurst exponent H in the range -0.75 <= H <= 1. The results confirm the conjectures of earlier studies

Correlations between EMG jaw muscle activity and facial morphology in complete denture wearers

In a sample of fifteen partially edentulous subjects assigned for immediate complete denture treatment, a correlation analysis was performed between pre-extraction facial morphology determined from lateral cephalograms, and EMG activity of the anterior temporal and masseter muscles in maximal clench and tapping of teeth. Marked correlations observed between vertical and sagittal jaw relations and mean voltages of the jaw-closing muscles indicated strong biting activity in subjects with a square facial type. No significant associations were observed between biting strength and the age of the subjects. Correlations between facial morphological changes and changes in EMG biting activity after denture insertion and during 1 year of denture wear indicated that the anterior temporal muscles were extremely sensitive to sagittal changes in anterior occlusion. The masseter muscles were less sensitive, but responded in some instances to changes in vertical jaw relationship.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73816/1/j.1365-2842.1983.tb00105.x.pd

Pervasive cold ice within a temperate glacier-implications for glacier thermal regimes, sediment transport and foreland geomorphology

© Author(s) 2019. Published by Copernicus Publications on behalf of the European Geosciences Union.This study suggests that cold-ice processes may be more widespread than previously assumed, even within temperate glacial systems. We present the first systematic mapping of cold ice at the snout of the temperate glacier Midtdalsbreen, an outlet of the Hardangerjøkulen icefield (Norway), from 43 line kilometres of ground-penetrating radar data. Results show a 40 m wide cold-ice zone within the majority of the glacier snout, where ice thickness is <10 m. We interpret ice to be cold-based across this zone, consistent with basal freeze-on processes involved in the deposition of moraines. We also find at least two zones of cold ice up to 15 m thick within the ablation area, occasionally extending to the glacier bed. There are two further zones of cold ice up to 30 m thick in the accumulation area, also extending to the glacier bed. Cold-ice zones in the ablation area tend to correspond to areas of the glacier that are covered by late-lying seasonal snow patches that reoccur over multiple years. Subglacial topography and the location of the freezing isotherm within the glacier and underlying subglacial strata likely influence the transport and supply of supraglacial debris and formation of controlled moraines. The wider implication of this study is the possibility that, with continued climate warming, temperate environments with primarily temperate glaciers could become polythermal in forthcoming decades with (i) persisting thinning and (ii) retreat to higher altitudes where subglacial permafrost could be and/or become more widespread. Adversely, the number and size of late-lying snow patches in ablation areas may decrease and thereby reduce the extent of cold ice, reinforcing the postulated change in the thermal regime.Peer reviewedFinal Published versio

Gravitational Geometric Phase in the Presence of Torsion

We investigate the relativistic and non-relativistic quantum dynamics of a neutral spin-1/2 particle submitted an external electromagnetic field in the presence of a cosmic dislocation. We analyze the explicit contribution of the torsion in the geometric phase acquired in the dynamic of this neutral spinorial particle. We discuss the influence of the torsion in the relativistic geometric phase. Using the Foldy-Wouthuysen approximation, the non-relativistic quantum dynamics are studied and the influence of the torsion in the Aharonov-Casher and He-McKellar-Wilkens effects are discussed.Comment: 14 pages, no figur