Structure of the poleward wall of the trough and the inclination of the geomagnetic field above the EISCAT radar

Abstract. A special high-resolution routine of the EISCAT radar has been used to investigate the structure and development of the poleward wall of a deep trough in electron density. The feature was tracked by the radar during a 7-hour period under very quiet geomagnetic conditions. The field-aligned nature of the structure enabled an estimate to be made of the inclination of the geomagnetic field above EISCAT that was in good agreement with the current model. Observations of narrow field-aligned enhancements in electron temperature demonstrated that the wall of this trough is a dynamic feature, reforming regularly as the electron density responds on a time scale of tens of minutes to energy input from soft-particle precipitation.

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Partition Coefficients of Methylated DNA Bases Obtained from Free Energy Calculations with Molecular Electron Density Derived Atomic Charges.

10.26434/chemrxiv.5793996 ◽

2018 ◽

Author(s):

Alejandro Lara ◽

Maximiliano Riquelme ◽

Esteban Vöhringer-Martinez

Keyword(s):

Electron Density ◽

Partition Coefficients ◽

Dna Bases ◽

Atomic Charges ◽

Free Energies ◽

Solvation Model ◽

Minimal Basis ◽

Methylated Dna ◽

Implicit Solvation Model ◽

Good Agreement

<div> <div> <div> <p>Partition coefficients serve in various areas as pharmacology and environmental sciences to predict the hydrophobicity of different substances. Recently, they have been also used to address the accuracy of force fields for various organic compounds and specifically the methylated DNA bases. In this study atomic charges were derived by different partitioning methods (Hirshfeld and Minimal Basis Iterative Stockholder) directly from the electron density obtained by electronic structure calculations in vac- uum, with an implicit solvation model or with explicit solvation taking the dynamics of the solute and the solvent into account. To test the ability of these charges to describe electrostatic interactions in force fields for condensed phases the original atomic charges of the AMBER99 force field were replaced with the new atomic charges and combined with different solvent models to obtain the hydration and chloroform solvation free energies by molecular dynamics simulations. Chloroform-water partition coefficients derived from the obtained free energies were compared to experimental and previously reported values obtained with the GAFF or the AMBER-99 force field. The results show that good agreement with experimental data is obtained when the polarization of the electron density by the solvent has been taken into account deriving the atomic charges of polar DNA bases and when the energy needed to polarize the electron den- sity of the solute has been considered in the transfer free energy. These results were further confirmed by hydration free energies of polar and aromatic amino acid side chain analogues. Comparison of the two partitioning methods Hirsheld-I and Minimal Basis Iterative Stockholder (MBIS) revealed some deficiencies in the Hirshfeld-I method related to nonexistent isolated anionic nitrogen pro-atoms used in the method. Hydration free energies and partitioning coefficients obtained with atomic charges from the MBIS partitioning method accounting for polarization by the implicit solvation model are in good agreement with the experimental values. </p> </div> </div> </div>

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An Analytical Drain Current Model for Dual-material Gate Graded - channel and Dual-oxide Thickness Cylindrical Gate (DMG-GC-DOT) MOSFET

Nanoscience &Nanotechnology-Asia ◽

10.2174/2210681208666180813122145 ◽

2019 ◽

Vol 9 (2) ◽

pp. 291-297

Author(s):

Hind Jaafar ◽

Abdellah Aouaj ◽

Ahmed Bouziane ◽

Benjamin Iñiguez

Keyword(s):

Current Model ◽

Drain Current ◽

Oxide Thickness ◽

Subthreshold Current ◽

The Poisson Equation ◽

Strong Inversion ◽

Cylindrical Form ◽

Silvaco Atlas ◽

Dual Material ◽

Good Agreement

Background: A novel Dual Material Gate Graded Channel and Dual Oxide Thickness Cylindrical Gate (DMG-GC-DOT) MOSFET is presented in this paper. Methods: Analytical model of drain current is developed using a quasi-two-dimensional cylindrical form of the Poisson equation and is expressed as a function of the surface potential, which is calculated using the expressions of the current density. Results: Comparison of the analytical results with 3D numerical simulations using Silvaco Atlas - TCAD software presents a good agreement from subthreshold to strong inversion regime and for different bias voltages. Conclusion: Two oxide thicknesses with different permittivity can effectively improve the subthreshold current of DMG-GC-DOT MOSFET.

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Pushing the Envelope

10.1093/oso/9780199670871.003.0014 ◽

2018 ◽

Author(s):

Eaton E. Lattman ◽

Thomas D. Grant ◽

Edward H. Snell

Keyword(s):

High Resolution ◽

Electron Density ◽

Structural Information ◽

Hydration Shell ◽

Three Dimensional ◽

Scattering Data ◽

Saxs Data ◽

Electron Density Function ◽

Angle Scattering ◽

Iterative Structure

Direct electron density determination from SAXS data opens up new opportunities. The ability to model density at high resolution and the implicit direct estimation of solvent terms such as the hydration shell may enable high-resolution wide angle scattering data to be used to calculate density when combined with additional structural information. Other diffraction methods that do not measure three-dimensional intensities, such as fiber diffraction, may also be able to take advantage of iterative structure factor retrieval. While the ability to reconstruct electron density ab initio is a major breakthrough in the field of solution scattering, the potential of the technique has yet to be fully uncovered. Additional structural information from techniques such as crystallography, NMR, and electron microscopy and density modification procedures can now be integrated to perform advanced modeling of the electron density function at high resolution, pushing the boundaries of solution scattering further than ever before.

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The frequency of Kozai–Lidov disc oscillation driven giant outbursts in Be/X-ray binaries

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2250 ◽

2019 ◽

Vol 489 (2) ◽

pp. 1797-1804 ◽

Cited By ~ 2

Author(s):

Rebecca G Martin ◽

Alessia Franchini

Keyword(s):

Orbital Period ◽

Time Scale ◽

Orbital Plane ◽

Material Flows ◽

X Ray ◽

System Parameters ◽

Be Star ◽

Chaotic Nature ◽

X Ray Binaries ◽

Good Agreement

ABSTRACT Giant outbursts of Be/X-ray binaries may occur when a Be-star disc undergoes strong eccentricity growth due to the Kozai–Lidov (KL) mechanism. The KL effect acts on a disc that is highly inclined to the binary orbital plane provided that the disc aspect ratio is sufficiently small. The eccentric disc overflows its Roche lobe and material flows from the Be star disc over to the companion neutron star causing X-ray activity. With N-body simulations and steady state decretion disc models we explore system parameters for which a disc in the Be/X-ray binary 4U 0115+634 is KL unstable and the resulting time-scale for the oscillations. We find good agreement between predictions of the model and the observed giant outburst time-scale provided that the disc is not completely destroyed by the outburst. This allows the outer disc to be replenished between outbursts and a sufficiently short KL oscillation time-scale. An initially eccentric disc has a shorter KL oscillation time-scale compared to an initially circular orbit disc. We suggest that the chaotic nature of the outbursts is caused by the sensitivity of the mechanism to the distribution of material within the disc. The outbursts continue provided that the Be star supplies material that is sufficiently misaligned to the binary orbital plane. We generalize our results to Be/X-ray binaries with varying orbital period and find that if the Be star disc is flared, it is more likely to be unstable to KL oscillations in a smaller orbital period binary, in agreement with observations.

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Investigation of Residual Strains of the Second Kind in Plastically Deformed Metallic Materials

MRS Proceedings ◽

10.1557/proc-376-409 ◽

1994 ◽

Vol 376 ◽

Cited By ~ 2

Author(s):

M. Vrána ◽

P. Klimanek ◽

T. Kschidock ◽

P. Lukáš ◽

P. Mikula

Keyword(s):

High Resolution ◽

Neutron Diffraction ◽

Stacking Faults ◽

Metallic Materials ◽

Line Broadening ◽

X Ray Diffraction ◽

X Ray ◽

Neutron Diffractometer ◽

Residual Strains ◽

Good Agreement

ABSTRACTInvestigation of strongly distorted crystal structures caused by dislocations, stacking-faults etc. in both plastically deformed f.c.c. and b.c.c. metallic materials was performed by the analysis of the neutron diffraction line broadening. Measurements were realized by means of the high resolution triple-axis neutron diffractometer equipped by bent Si perfect crystals as monochromator and analyzer at the NPI Řež. The substructure parameters obtained in this manner are in good agreement with the results of X-ray diffraction analysis.

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Polar patches observed by ESR and their possible origin in the cusp region

Annales Geophysicae ◽

10.1007/s00585-000-1043-5 ◽

2000 ◽

Vol 18 (9) ◽

pp. 1043-1053 ◽

Cited By ~ 12

Author(s):

A. M. Smith ◽

S. E. Pryse ◽

L. Kersley

Keyword(s):

Energy Distribution ◽

Electron Density ◽

Plasma Flow ◽

Plasma Temperature ◽

Soft Particle ◽

Polar Ionosphere ◽

Polar Cap ◽

Particle Precipitation ◽

Cusp Region ◽

Reconnection Site

Abstract. Observations by the EISCAT Svalbard radar in summer have revealed electron density enhancements in the magnetic noon sector under conditions of IMF Bz southward. The features were identified as possible candidates for polar-cap patches drifting anti-Sunward with the plasma flow. Supporting measurements by the EISCAT mainland radar, the CUTLASS radar and DMSP satellites, in a multi-instrument study, suggested that the origin of the structures lay upstream at lower latitudes, with the modulation in density being attributed to variability in soft-particle precipitation in the cusp region. It is proposed that the variations in precipitation may be linked to changes in the location of the reconnection site at the magnetopause, which in turn results in changes in the energy distribution of the precipitating particles.Key words: Ionosphere (ionosphere-magnetosphere interactions; plasma temperature and density; polar ionosphere)

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Refinement of proteins at subatomic resolution withMOPRO

Journal of Applied Crystallography ◽

10.1107/s0021889801001753 ◽

2001 ◽

Vol 34 (2) ◽

pp. 214-223 ◽

Cited By ~ 94

Author(s):

Benoit Guillot ◽

Laurence Viry ◽

Regis Guillot ◽

Claude Lecomte ◽

Christian Jelsch

Keyword(s):

High Resolution ◽

Supramolecular Chemistry ◽

Electron Density ◽

Structure Factor ◽

Atomic Electron ◽

Gradient Algorithm ◽

Large Structures ◽

Diagonal Approximation ◽

Atomic Electron Density ◽

Very High

Crystallography at subatomic resolution permits the observation and measurement of the non-spherical character of the atomic electron density. Charge density studies are being performed on molecules of increasing size. TheMOPROleast-squares refinement software has thus been developed, by extensive modifications of the programMOLLY, for protein and supramolecular chemistry applications. The computation times are long because of the large number of reflections and the complexity of the multipolar model of the atomic electron density; the structure factor and derivative calculations have thus been parallelized. Stereochemical and dynamical restraints as well as the conjugate gradient algorithm have been implemented. A large number of the normal matrix off-diagonal terms turn out to be very small and the block diagonal approximation is thus particularly efficient in the case of large structures at very high resolution.

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