9,928 research outputs found
The atomic orbitals of the topological atom
The effective atomic orbitals have been realized in the framework of Bader’s atoms in molecules theory for a general wavefunction. This formalism can be used to retrieve from any type of calculation a
proper set of orthonormalized numerical atomic orbitals, with occupation numbers that sum up to the
respective Quantum Theory of Atoms in Molecules (QTAIM) atomic populations. Experience shows
that only a limited number of effective atomic orbitals exhibit significant occupation numbers. These
correspond to atomic hybrids that closely resemble the core and valence shells of the atom. The
occupation numbers of the remaining effective orbitals are almost negligible, except for atoms with
hypervalent character. In addition, the molecular orbitals of a calculation can be exactly expressed
as a linear combination of this orthonormalized set of numerical atomic orbitals, and the Mulliken
population analysis carried out on this basis set exactly reproduces the original QTAIM atomic populations of the atoms. Approximate expansion of the molecular orbitals over a much reduced set of
orthogonal atomic basis functions can also be accomplished to a very good accuracy with a singular
value decomposition procedure
Dynamical mechanism of anticipating synchronization in excitable systems
We analyze the phenomenon of anticipating synchronization of two excitable
systems with unidirectional delayed coupling which are subject to the same
external forcing. We demonstrate for different paradigms of excitable system
that, due to the coupling, the excitability threshold for the slave system is
always lower than that for the master. As a consequence the two systems respond
to a common external forcing with different response times. This allows to
explain in a simple way the mechanism behind the phenomenon of anticipating
synchronization.Comment: 4 pages including 7 figures. Submitted for publicatio
Saturn IB Stage Launch Operations
The prelaunch and launch activities are described as they pertain to the S-IB (booster) stage of the 1.6 mi11ion-pound thrust Uprated Saturn Launch Vehicle. The typical over-all schedule for an Uprated Saturn Launch is presented, culminating in the launch, and concluding with analysis of the data returned. The launch vehicle is described, with a precis of the stages and the role each has in the performance of the mission. The paper is concerned with the testing performed to bring the composite parts of the launch vehicle to flight readiness status, with emphasis on the booster stage
What Should the Business Know About Information Systems?
This paper presents an exploratory study of Information Systems (IS) competencies of business managers in Europe. Following resource-based theory and a knowledge-based view of IS competencies, an extensive review of the literature is conducted to identify a comprehensive list of IS competencies of business managers. In order to validate the business IS competence model, a Delphi study is conducted using two panels consisting of general managers and IS managers. The results indicate that IS competencies of business managers involve a fluid mix of both explicit and tacit knowledge components, and suggest that ‘core’ IS competencies of business managers involve knowledge and experience in the strategic management of IS. Core business IS competencies involve having knowledge about IS strategy, IS investment management, IS resource allocation, IS sourcing options, IS relationship management and IS change management, and professional experience in IS projects and managing IS. This paper concludes by discussing the implications of these findings and provides several directions for future research
BiFeO3/La0.7Sr0.3MnO3 heterostructures deposited on Spark Plasma Sintered LaAlO3 Substrates
Multiferroic BiFeO3 (BFO) / La0.7Sr0.3MnO3 heterostructured thin films were
grown by pulsed laser deposition on polished spark plasma sintered LaAlO3 (LAO)
polycrystalline substrates. Both polycrystalline LAO substrates and BFO films
were locally characterized using electron backscattering diffraction (EBSD),
which confirmed the high-quality local epitaxial growth on each substrate
grain. Piezoforce microscopy was used to image and switch the piezo-domains,
and the results are consistent with the relative orientation of the
ferroelectric variants with the surface normal. This high-throughput synthesis
process opens the routes towards wide survey of electronic properties as a
function of crystalline orientation in complex oxide thin film synthesis.Comment: 10 pages, 4 figures, Submitted to Applied Physics Letter
The electron-phonon coupling strength at metal surfaces directly determined from the Helium atom scattering Debye-Waller factor
A new quantum-theoretical derivation of the elastic and inelastic scattering
probability of He atoms from a metal surface, where the energy and momentum
exchange with the phonon gas can only occur through the mediation of the
surface free-electron density, shows that the Debye-Waller exponent is directly
proportional to the electron-phonon mass coupling constant . The
comparison between the values of extracted from existing data on the
Debye-Waller factor for various metal surfaces and the values known
from literature indicates a substantial agreement, which opens the possibility
of directly extracting the electron-phonon coupling strength in quasi-2D
conducting systems from the temperature or incident energy dependence of the
elastic Helium atom scattering intensities.Comment: 14 pages, 2 figures, 1 tabl
Non-Markovian Stochastic Resonance: three state model of ion channel gating
Stochastic Resonance in single voltage-dependent ion channels is investigated
within a three state non-Markovian modeling of the ion channel conformational
dynamics. In contrast to a two-state description one assumes the presence of an
additional closed state for the ion channel which mimics the manifold of
voltage-independent closed subconformations (inactivated ``state''). The
conformational transition into the open state occurs through a domain of
voltage-dependent closed subconformations (closed ``state''). At distinct
variance with a standard two-state or also three-state Markovian approach, the
inactivated state is characterized by a broad, non-exponential probability
distribution of corresponding residence times. The linear response to a
periodic voltage signal is determined for arbitrary distributions of the
channel's recovery times. Analytical results are obtained for the spectral
amplification of the applied signal and the corresponding signal-to-noise
ratio. Alternatively, these results are also derived by use of a corresponding
two-state non-Markovian theory which is based on driven integral renewal
equations [I. Goychuk and P. Hanggi, Phys. Rev. E 69, 021104 (2004)]. The
non-Markovian features of stochastic resonance are studied for a power law
distribution of the residence time-intervals in the inactivated state which
exhibits a large variance. A comparison with the case of bi-exponentially
distributed residence times possessing the same mean value, i.e. a simplest
non-Markovian two-state description, is also presented
16α,17α-Epoxy-5α-hydroxy-6β-nitrooxy-20-oxopregnan-3β-yl acetate
The title steroid, C23H33NO8, is a pregnane derivative obtained regio-, stereo- and chemoselectively from the ring opening of the corresponding 5α,6α;16α,17α-diepoxide with bismuth(III) nitrate. There are two symmetry-independent molecules in the asymmetric unit that show no significant differences concerning bond lengths and angles. All rings are trans-fused. The conformations of the six-membered rings are close to chair forms, while the five-membered ring adopts an envelope conformation. The molecules are held together by an extensive O—H⋯O hydrogen-bonding network of chains runnning along the a axis
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