154,362 research outputs found
Asteroseismology of the Scuti star HD 50844
Aims. We aim to probe the internal structure and investigate more detailed
information of the Scuti star HD 50844 with asteroseismology. Methods.
We analyse the observed frequencies of the Scuti star HD 50844
obtained by Balona (2014), and search for possible multiplets based on the
rotational splitting law of g-mode. We tried to disentangle the frequency
spectra of HD 50844 by means of the rotational splitting only. We then compare
them with theoretical pulsation modes, which correspond to stellar evolutionary
models with various sets of initial metallicity and stellar mass, to find the
best-fitting model. Results. There are three multiplets including two complete
triplets and one incomplete quintuplet, in which mode identifications for
spherical harmonic degree and azimuthal number are unique. The
corresponding rotational period of HD 50844 is found to be
2.44 days. The physical parameters of HD 50844 are well
limited in a small region by three modes identified as nonradial ones
(, , and ) and by the fundamental radial mode
(). Our results show that the three nonradial modes (, ,
and ) are all mixed modes, which mainly represent the property of the
helium core. The fundamental radial mode () mainly represents the
property of the stellar envelope. In order to fit these four pulsation modes,
both the helium core and the stellar envelope must be matched to the actual
structure of HD 50844. Finally, the mass of the helium core of HD 50844 is
estimated to be 0.173 0.004 for the first time. The physical
parameters of HD 50844 are determined to be 1.81 0.01 ,
0.008 0.001. 7508 125 K, log 3.658
0.004, 3.300 0.023 , 30.98 2.39 .Comment: 11 pages, 7 figures, 6 tables, accepted for publication in A&
Selecting between two transition states by which water oxidation intermediates on an oxide surface decay
While catalytic mechanisms on electrode surfaces have been proposed for
decades, the pathways by which the product's chemical bonds evolve from the
initial charge-trapping intermediates have not been resolved in time. Here, we
discover a reactive population of charge-trapping intermediates with states in
the middle of a semiconductor's band-gap to reveal the dynamics of two parallel
transition state pathways for their decay. Upon photo-triggering the water
oxidation reaction from the n-SrTiO3 surface with band-gap, pulsed excitation,
the intermediates' microsecond decay reflects transition state theory (TST)
through: (1) two distinct and reaction dependent (pH, T, Ionic Strength, and
H/D exchange) time constants, (2) a primary kinetic salt effect on each
activation barrier and an H/D kinetic isotope effect on one, and (3) realistic
activation barrier heights (0.4 - 0.5 eV) and TST pre-factors (10^11 - 10^12
Hz). A photoluminescence from midgap states in n-SrTiO3 reveals the reaction
dependent decay; the same spectrum was previously assigned by us to
hole-trapping at parallel Ti-O(dot)-Ti (bridge) and perpendicular Ti-O(dot)
(oxyl) O-sites using in situ ultrafast vibrational and optical spectroscopy.
Therefore, the two transition states are naturally associated with the decay of
these respective intermediates. Furthermore, we show that reaction conditions
select between the two pathways, one of which reflects a labile intermediate
facing the electrolyte (the oxyl) and the other a lattice oxygen (the bridge).
Altogether, we experimentally isolate an important activation barrier for water
oxidation, which is necessary for designing water oxidation catalysts with high
O2 turn over. Moreover, in isolating it, we identify competing mechanisms for
O2 evolution at surfaces and show how to use reaction conditions to select
between them
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Linking human-building interactions in shared offices with personality traits
Occupant behavior influences office building energy performance. The level of human-building interactions (HBIs) in shared offices strongly influences building energy use and occupant well-being. This study explored the link between occupant personality types and their behaviors of sharing energy and environment control systems and interactions with their colleagues. Inspired by the Five-Factor Model (FFM), we classified HBI behaviors into four dimensions: willingness to share control, knowledge of control, group decision behavior, and adaptive strategies. These four variables can be mapped to the four personality traits proposed by the FFM: agreeableness, openness, extraversion, and conscientiousness. Our cluster analysis identified six behavioral patterns: average (17.7%), reserved (15.3%), environmentally friendly (16.6%), role model (24.2%), self-centered (17.2%), and mechanist (9.0%). We further applied association rules, a widely utilized machine learning technique, to discover how demographics, building-related contextual factors, and perception-attitudinal factors influence HBI behaviors. Country, control feature accessibility, and group dynamics were found to be the three most influential factors that determine occupants’ HBI behaviors. The study provides insights about building design and operation, as well as policy to promote socially and environmentally desirable HBI behaviors in a shared office environment
Comment on "Superconducting gap anisotropy vs. doping level in high-T_c cuprates" by C. Kendziora et al, PRL 77, 727 (1996)
In a recent paper Kendziora et al concluded that the superconducting gap in
overdoped Bi-2212 is isotropic. From data obtained from electronic Raman
scattering measurements, their conclusion was based on the observation that
pair breaking peaks occured at approximately the same frequency in different
scattering geometries and that the normalized scattering intensity at low
energies was strongly depleted. We discuss a different interpretation of the
raw data and present new data which is consistent with a strongly anisotropic
gap with nodes. The spectra can be successfully described by a model for Raman
scattering in a d_{x^{2}-y^{2}} superconductor with spin fluctuations and
impurity scattering included.Comment: 1 page revtex plus 1 postscript figur
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