2,195 research outputs found
A hidden symmetry of a branching law
We consider branching laws for the restriction of some irreducible unitary
representations of to its subgroup . In Kobayashi
(arXiv:1907.07994), the irreducible subrepresentations of in the
restriction of the unitary are determined. By considering
the restriction of packets of irreducible representations we obtain another
very simple branching law, which was conjectured in Orsted-Speh
(arXiv:1907.07544).Comment: 16 page
A new fundamental type of conformational isomerism
© 2018 The Author(s). Isomerism is a fundamental chemical concept, reflecting the fact that the arrangement of atoms in a molecular entity has a profound influence on its chemical and physical properties. Here we describe a previously unclassified fundamental form of conformational isomerism through four resolved stereoisomers of a transoid (BF)O(BF)-quinoxalinoporphyrin. These comprise two pairs of enantiomers that manifest structural relationships not describable within existing IUPAC nomenclature and terminology. They undergo thermal diastereomeric interconversion over a barrier of 104 ± 2 kJ mol-1, which we term 'akamptisomerization'. Feasible interconversion processes between conceivable synthesis products and reaction intermediates were mapped out by density functional theory calculations, identifying bond-angle inversion (BAI) at a singly bonded atom as the reaction mechanism. We also introduce the necessary BAI stereodescriptors parvo and amplo. Based on an extended polytope formalism of molecular structure and stereoisomerization, BAI-driven akamptisomerization is shown to be the final fundamental type of conformational isomerization
Probing the spin polarization of current by soft X-ray imaging of current-induced magnetic vortex dynamics
Time-resolved soft X-ray transmission microscopy is applied to image the
current-induced resonant dynamics of the magnetic vortex core realized in a
micronsized Permalloy disk. The high spatial resolution better than 25 nm
enables us to observe the resonant motion of the vortex core. The result also
provides the spin polarization of the current to be 0.67 +/-0.16 for Permalloy
by fitting the experimental results with an analytical model in the framework
of the spin-transfer torque.Comment: 13 pages, 3 figure
Resist, comply or workaround? An examination of different facets of user engagement with information systems
This paper provides a summary of studies of user resistance to Information Technology (IT) and identifies workaround activity as an understudied and distinct, but related, phenomenon. Previous categorizations of resistance have largely failed to address the relationships between the motivations for divergences from procedure and the associated workaround activity. This paper develops a composite model of resistance/workaround derived from two case study sites. We find four key antecedent conditions derived from both positive and negative resistance rationales and identify associations and links to various resultant workaround behaviours and provide supporting Chains of Evidence from two case studies
Effect of Multiphase Radiation on Coal Combustion in a Pulverized Coal jet Flame
The accurate modeling of coal combustion requires detailed radiative heat transfer models for both gaseous combustion products and solid coal particles. A multiphase Monte Carlo ray tracing (MCRT) radiation solver is developed in this work to simulate a laboratory-scale pulverized coal flame. The MCRT solver considers radiative interactions between coal particles and three major combustion products (CO2, H2O, and CO). A line-by-line spectral database for the gas phase and a size-dependent nongray correlation for the solid phase are employed to account for the nongray effects. The flame structure is significantly altered by considering nongray radiation and the lift-off height of the flame increases by approximately 35%, compared to the simulation without radiation. Radiation is also found to affect the evolution of coal particles considerably as it takes over as the dominant mode of heat transfer for medium-to-large coal particles downstream of the flame. To investigate the respective effects of spectral models for the gas and solid phases, a Planck-mean-based gray gas model and a size-independent gray particle model are applied in a frozen-field analysis of a steady-state snapshot of the flame. The gray gas approximation considerably underestimates the radiative source terms for both the gas phase and the solid phase. The gray coal approximation also leads to under-prediction of the particle emission and absorption. However, the level of under-prediction is not as significant as that resulting from the employment of the gray gas model. Finally, the effect of the spectral property of ash on radiation is also investigated and found to be insignificant for the present target flame
Complex spectral evolution in a BCS superconductor, ZrB12
We investigate the electronic structure of a complex conventional superconductor, ZrB12 employing high resolution photoemission spectroscopy and ab initio band structure calculations. The experimental valence band spectra could be described reasonably well within the local density approximation. Energy bands close to the Fermi level possess t2g symmetry and the Fermi level is found to be in the proximity of quantum fluctuation regime. The spectral lineshape in the high resolution spectra is complex exhibiting signature of a deviation from Fermi liquid behavior. A dip at the Fermi level emerges above the superconducting transition temperature that gradually grows with the decrease in temperature. The spectral simulation of the dip and spectral lineshape based on a phenomenological self energy suggests finite electron pair lifetime and a pseudogap above the superconducting transition temperature
Phase-field approach to heterogeneous nucleation
We consider the problem of heterogeneous nucleation and growth. The system is
described by a phase field model in which the temperature is included through
thermal noise. We show that this phase field approach is suitable to describe
homogeneous as well as heterogeneous nucleation starting from several general
hypotheses. Thus we can investigate the influence of grain boundaries,
localized impurities, or any general kind of imperfections in a systematic way.
We also put forward the applicability of our model to study other physical
situations such as island formation, amorphous crystallization, or
recrystallization.Comment: 8 pages including 7 figures. Accepted for publication in Physical
Review
Multiplicity-free theorems of the restrictions of unitary highest weight modules with respect to reductive symmetric pairs
The complex analytic methods have found a wide range of applications in the
study of multiplicity-free representations. This article discusses, in
particular, its applications to the question of restricting highest weight
modules with respect to reductive symmetric pairs. We present a number of
multiplicity-free branching theorems that include the multiplicity-free
property of some of known results such as the Clebsh--Gordan--Pieri formula for
tensor products, the Plancherel theorem for Hermitian symmetric spaces (also
for line bundle cases), the Hua--Kostant--Schmid -type formula, and the
canonical representations in the sense of Vershik--Gelfand--Graev. Our method
works in a uniform manner for both finite and infinite dimensional cases, for
both discrete and continuous spectra, and for both classical and exceptional
cases
Formation and Evolution of Early-Type Galaxies: Spectro-Photometry from Cosmo-Chemo-Dynamical Simulations
One of the major challenges in modern astrophysics is to understand the
origin and the evolution of galaxies, the bright, massive early type galaxies
(ETGs) in particular. Therefore, these galaxies are likely to be good probes of
galaxy evolution, star formation and, metal enrichment in the early Universe.
In this context it is very important to set up a diagnostic tool able to
combine results from chemo-dynamical N-Body-TSPH (NB-TSPH) simulations of ETGs
with those of spectro-photometric population synthesis and evolution so that
all key properties of galaxies can be investigated. The main goal of this paper
is to provide a preliminary validation of the software package before applying
it to the analysis of observational data. The galaxy models in use where
calculated by the Padova group in two different cosmological scenarios: the
SCDM, and the Lambda CDM. For these models, we recover their
spectro-photometric evolution through the entire history of the Universe. We
computed magnitudes and colors and their evolution with the redshift along with
the evolutionary and cosmological corrections for the model galaxies at our
disposal, and compared them with data for ETGs taken from the COSMOS and the
GOODS databases. Starting from the dynamical simulations and photometric models
at our disposal, we created synthetic images from which we derived the
structural and morphological parameters. The theoretical results are compared
with observational data of ETGs selected form the SDSS database. The simulated
colors for the different cosmological scenarios follow the general trend shown
by galaxies of the COSMOS and GOODS. Within the redshift range considered, all
the simulated colors reproduce the observational data quite well.Comment: 28 pages, 28 figures, accepted for pubblication by A&
The Hydration Structure at Yttria-Stabilized Cubic Zirconia (110)-Water Interface with Sub-Angstrom Resolution
The interfacial hydration structure of yttria-stabilized cubic zirconia (110) surface in contact with water was determined with ~0.5 Å resolution by high-resolution X-ray reflectivity measurement. The terminal layer shows a reduced electron density compared to the following substrate lattice layers, which indicates there are additional defects generated by metal depletion as well as intrinsic oxygen vacancies, both of which are apparently filled by water species. Above this top surface layer, two additional adsorbed layers are observed forming a characteristic interfacial hydration structure. The first adsorbed layer shows abnormally high density as pure water and likely includes metal species, whereas the second layer consists of pure water. The observed interfacial hydration structure seems responsible for local equilibration of the defective surface in water and eventually regulating the long-term degradation processes. The multitude of water interactions with the zirconia surface results in the complex but highly ordered interfacial structure constituting the reaction front.ope
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