4,446 research outputs found
Eternally inflating cosmologies from intersecting spacelike branes
Intersecting spacelike braneworld cosmologies are investigated. The time axis
is set on the scale parameter of extra space, which may include more than one
timelike metric. Obtained are eternally inflating (i.e. undergoing late-time
inflation) Robertson-Walker spacetime and extra space with a constant scale
factor. In the case of multibrane solutions, some dimensions are static or
shrink. The fact that the largest supersymmetry algebra contains 32
supercharges in 4 dimensions imposes a restriction on the geometry of extra
space.Comment: 19 page
Microscopic Model for Photoinduced Magnetism in the Molecular Complex Perchlorate
A theoretical model for understanding photomagnetism in the heptanuclear
complex perchlorate is developed. It is a
many-body model involving the active orbitals on the transition metal ions. The
model is exactly solved using a valence bond approach. The ground state
solution of the model is highly degenerate and is spanned by five S=0 states,
nine S=1 states, five S=2 states and one S=3 state. The orbital occupancies in
all these states correspond to six ions and one diamagnetic
ion. The optically excited charge-transfer (CT) state in each spin sector occur
at nearly the same excitation energy of 2.993 eV for the physically reasonable
parameter values. The degeneracy of the CT states is largest in the S=3 sector
and so is the transition dipole moment from the ground state to these excited
states. Thus laser irradiation with light of this energy results in most
intense absorption in the S=3 sector. The life-time of the S=3 excited states
is also expected to be the largest as the number of states below that energy is
very sparse in this spin sector when compared to other spin sectors. These twin
features of our model explain the observed photomagnetism in the
complex.Comment: 8 pages, 6 figures and 1 tabl
Evidence for line nodes in the energy gap of the overdoped Ba(FeCo)As from low-temperature specific heat measurements
Low-temperature specific heat (SH) is measured on
Ba(FeCo)As single crystals in a wide doping region under
different magnetic fields. For the overdoped sample, we find the clear evidence
for the presence of term in the data, which is absent both for the
underdoped and optimal doped samples, suggesting the presence of line nodes in
the energy gap of the overdoped samples. Moreover, the field induced electron
specific heat coefficient increases more quickly with the
field for the overdoped sample than the underdoped and optimal doped ones,
giving another support to our arguments. Our results suggest that the
superconducting gap(s) in the present system may have different structures
strongly depending on the doping regions.Comment: 5 pages, 4 figure
Vitamin D Supplementation as a Potential Cause of U-shaped Associations between Vitamin D Levels and Negative Health Outcomes: A Decision Tree Analysis for Risk of Frailty
Background: A recent controversy in vitamin D research is a “U-shaped association”, with elevated disease risks at
both high and low 25-hydroxyvitamin D (25 (OH) D) levels.
Methods: This is a cross-sectional study of 238 male nursing home veterans in Hawaii. Classification and regression
tree (CART) analysis identified groups based on 25 (OH) D and vitamin D supplementation for frailty risk.
Characteristics were examined and compared across the groups using logistic regression and receiver operating
characteristic (ROC) curve analyses.
Results: CART analysis identified three distinct groups: vitamin D supplement users (n = 86), non-users with low
vitamin D (n = 55), and non-users with high vitamin D (n = 97). Supplement users were the most frail, but had high
mean 25 (OH) D of 26.6 ng/mL, which was compatible with 27.1 ng/mL in non-users with high vitamin D, while mean
25 (OH) D of non-users with low vitamin D was 11.7 ng/mL. Supplement users and non-users with low vitamin D were
significantly more likely to be frail (odds ratio (OR) = 9.90, 95% CI = 2.18–44.86, p = 0.003; OR = 4.28, 95% CI = 1.44–12.
68, p = 0.009, respectively), compared with non-users with low vitamin D. ROC curve analysis showed the three groups
significantly predicted frailty (area under the curve = 0.73), with sensitivity of 64.4% and specificity of 76.7%, while 25
(OH) D did not predict frailty.
Conclusions: In these nursing home veterans, vitamin D supplement users were the most frail but with high 25 (OH)
D. This can potentially be a cause of U-shaped associations between vitamin D levels and negative health outcomes
Resource-driven Substructural Defeasible Logic
Linear Logic and Defeasible Logic have been adopted to formalise different
features relevant to agents: consumption of resources, and reasoning with
exceptions. We propose a framework to combine sub-structural features,
corresponding to the consumption of resources, with defeasibility aspects, and
we discuss the design choices for the framework
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