Search results for "hell"
showing 10 items of 1035 documents
Growth patterns of the topshell Phorcus lineatus (da Costa, 1778) in northern Iberia deduced from shell sclerochronology
2019
Combined shell growth pattern and oxygen isotope analysis has become a powerful approach in palaeoclimate and archaeological studies for reconstructing palaeoclimate conditions and littoral exploitation patterns, respectively. Recent investigations have shown that the gastropod Phorcus lineatus (da Costa, 1778) forms its shell in conditions of near equilibrium with the oxygen isotope signature of the seawater environment, demonstrating the utility of this species for reconstruction of sea surface temperature and determination of the season of harvest in archaeological studies. In contrast, the shell growth patterns of this species have received virtually no attention despite providing infor…
Atomistic simulation of SrTiO3 and BaTiO3 (110) surface relaxations
2000
Abstract The (110) surface relaxations were calculated for SrTiO 3 and BaTiO 3 perovskites in a cubic phase. Using a shell model, the positions of atoms in 16 near- surface layers placed atop a slab of rigid ions are calculated. The strong surface rumpling and induced surface dipole moments perpendicular to the surface are predicted for both the O-terminated and TiO-terminated surfaces.
Atomistic Simulations of the LaMnO3 (110) Polar Surface.
2003
The results of atomic structure calculations, with a focus on the surface relaxation and polarization, are presented for the LaMnO3 (110) O-terminated polar surface. We compare results of the classical shell model calculations for four possible terminations, including (1 × 2) (110) surface reconstruction, and demonstrate that the latter has the lowest surface energy. The surface energy is saturated only when six to eight near-surface atomic planes are relaxed which is accompanied by the considerable dipole moments perpendicular to the surface. Results are compared with those for iso-structural BaTiO3 (110) surfaces.
ATOMISTIC CALCULATIONS OF (110) SURFACE RELAXATION FOR PEROVSKITE TITANATES
1999
Using a shell model, for the first time the (110) surface relaxations are calculated for SrTiO 3 and BaTiO 3 perovskites. The positions of atoms in 16 near-surface layers placed atop a slab of rigid ions are calculated. Strong surface rumpling and surface-induced dipole moments perpendicular to the surface are predicted for both the O-terminated and Ti-terminated surfaces.
Structural properties of core and surface of silica nanoparticles investigated by Raman spectroscopy
2013
We studied the experimental Raman spectra of various commercial silica nanoparticles of average diameter from 7 to 40 nm and specific surface from 50 to 380 m2/g. We found that the peculiarities of the particles Raman spectra systematically depend on their specific surface. In detail, the peak position of the R band at about 440 cm−1 shifts towards high wavenumbers following an almost linear dependence on the specific surface. Similarly, the amplitudes of the D1 and D2 bands, at about 495 and 605 cm−1, respectively, increase linearly with the same quantity. Our results are interpreted in the frame of the shell model for the nanoparticles clarifying that the network of the core of the nanopa…
Semiflexible Polymers in Spherical Confinement: Bipolar Orientational Order Versus Tennis Ball States
2017
Densely packed semiflexible polymers with contour length L confined in spheres with radius R of the same order as L cannot exhibit uniform nematic order. Depending on the chain stiffness (which we vary over a wide range), highly distorted structures form with topological defects on the sphere surface. These structures are completely different from previously observed ones of very long chains winding around the inner surface of spheres and from nematic droplets. At high densities, a thin shell of polymers close to the sphere surface exhibits a tennis ball texture due to the confinement-induced gradual bending of polymer bonds. In contrast, when the contour length of the chains is significant…
Surface Relaxation in Ferroelectric Perovskites: An Atomistic Study
1996
ABSTRACTThe effect of the [001] surface relaxation on the polarization of the paraelectric BaTiO3 is simulated in the framework of the shell model. Our atomistic simulations show a large polarization of ions in the first several layers nearby the surface and confirm the possibility of co-existence of Ti-and Ba-terminated [001] BaTiO3 surfaces which have very close surface energies.
Calculations of atomic and electronic structure for (100) surfaces of SrTiO3 perovskite
2002
AbstractWe present and discuss main results of the calculations for the surface relaxation and rumpling of SrTiO3 surfaces with TiO2 and SrO terminations using a wide variety of methods of modern computational physics and chemistry, including the shell model (SM) and ab initio methods based on Hartree-Fock (HF) and Density Functional Theory (DFT). The HF and DFT formalisms with different exchange-correlation functionals are implemented into Crystal-98 computer code using a Gaussian-type basis set. We demonstrate that a hybrid B3PW formalism gives the best results for the bulk SrTiO3 properties. Results are compared with previous ab initio plane-wave LDA calculations and LEED experiments. Ou…
MetaEdit— A flexible graphical environment for methodology modelling
1991
Existing CASE tools are often rigid and do not support the users' native methodologies. To alleviate this, more flexible and customisable tools called CASE shells are emerging. However, the customisation of those tools is still cumbersome and error-prone, and demands several configuration files that follow a rigid syntax of some metamodelling language(s). In order to make the customisation easier, we propose a graphical metamodelling editor, MetaEdit, with which the conceptual structures of the user methodology can be modelled easily using an easy-to-grasp graphical notation. With MetaEdit, methodology models can be constructed with less effort and the configuration files for the CASE shell…
Komēdijas žanra tradīcija Teokrita idillēs
2015
Hellēnisma laikā veidojās jauns žanrs - literārā bukolika. Tas ir hellēnisma laiks, kad viena no galvenajām literatūras tendencēm ir tieksme pēc oriģinalitātes, no kā izriet novitāšu meklējumi, it sevišķi senu žanru un senu tēmu neierasts pasniegums. Dzejnieks Teokrits izvēlas savu ceļu, apvienojot senu folkloras žanru – folkloristisko bukoliku – ar nesen radušos literatūras žanru – jaunatisko komēdiju. Bakalaura darba mērķis ir saskatīt jaunatiskās komēdijas ietekmi Teokrita bukolikās, aizgūtos tēlus un motīvus. Darba gaitā svarīgi būs apskatīt aspektus, kā komēdijas žanrs sasaucas ar Teokrita idillēm, kas kopīgs. Bakalaura darbs ir veidots no trīs nodaļām. Pirmajā nodaļā skatīts dzejnieks…