8,982 research outputs found
Density-metric unimodular gravity:vacuum spherical symmetry
We analyze an alternative theory of gravity characterized by metrics that are
tensor density of rank(0,2)and weight-1/2.The metric compatibility condition is
supposed to hold. The simplest expression for the action of gravitational field
is used.Taking the metric and trace of connections as dynamical variables,the
field equations in the absence of matter and other kinds of sources are
derived.The solutions of these equations are obtained for the case of vacuum
static spherical symmetric spacetime.The null geodesics and advance of
perihelion of ellipes are discussed.We confirm a subclass of solutions is
regular for r>0 and there is no event horizon while it is singular at r=0.Comment: 15 pages,no,figures,typos corrected,new section added,published
versio
The lowest singlet-triplet excitation energy of BN: a converged coupled cluster perspective
The notoriously small excitation energy of the BN
diatomic has been calculated using high-order coupled cluster methods.
Convergence has been established in both the 1-particle basis set and the
coupled cluster expansion. Explicit inclusion of connected quadruple
excitations is required for even semiquantitative agreement with
the limit value, while connected quintuple excitations still have
an effect of about 60 cm. Still higher excitations only account for
about 10 cm. Inclusion of inner-shell correlation further reduces
by about 60 cm at the CCSDT, and 85 cm at the CCSDTQ level. Our
best estimate, =18340 cm, is in excellent agreement with
earlier calculations and experiment, albeit with a smaller (and conservative)
uncertainty. The dissociation energy of BN() is =105.740.16
kcal/mol and =103.570.16 kcal/mol.Comment: J. Chem. Phys., in pres
FINITE H-DIMENSION DOES NOT IMPLY EXPRESSIVE COMPLETENESS
Accepted versio
Order preserving pattern matching on trees and DAGs
The order preserving pattern matching (OPPM) problem is, given a pattern
string and a text string , find all substrings of which have the
same relative orders as . In this paper, we consider two variants of the
OPPM problem where a set of text strings is given as a tree or a DAG. We show
that the OPPM problem for a single pattern of length and a text tree
of size can be solved in time if the characters of are
drawn from an integer alphabet of polynomial size. The time complexity becomes
if the pattern is over a general ordered alphabet. We
then show that the OPPM problem for a single pattern and a text DAG is
NP-complete
Beberapa Metode Pengambilan Ektoparasit Pada Burung Merpati Pos (Columba Livia Gmelen)
JANITA AZIZ & M. AMIR. 1988.Some ectoparasites collecting methods of racing pigeon (Columba livia Gmelin). Berita Biologi 3(8):382 - 385.Extraction of ectoparasites of living racing pigeons was done using modified "Fait Isle".The insectisides used for the extraction were pyrethrum,caumaphos and chloroform.The number of acarines extracted during the night was higher than that during the day.In addition insecticides spraying treatment extracted more acarines than fumigation.From the 3 kinds of insecticides used,chloroform proved to kill more acarines than the other two insecticides
W4 theory for computational thermochemistry: in pursuit of confident sub-kJ/mol predictions
In an attempt to improve on our earlier W3 theory [J. Chem. Phys. {\bf 120},
4129 (2004)] we consider such refinements as more accurate estimates for the
contribution of connected quadruple excitations (), inclusion of
connected quintuple excitations (), diagonal Born-Oppenheimer
corrections (DBOC), and improved basis set extrapolation procedures. Revised
experimental data for validation purposes were obtained from the latest version
of the ATcT (Active Thermochemical Tables) Thermochemical Network. We found
that the CCSDTQCCSDT(Q) difference converges quite rapidly with the basis
set, and that the formula
1.10[CCSDT(Q)/cc-pVTZ+CCSDTQ/cc-pVDZCCSDT(Q)/cc-pVDZ] offers a very reliable
as well as fairly cost-effective estimate of the basis set limit
contribution. The largest contribution found in the present work is
on the order of 0.5 kcal/mol (for ozone). DBOC corrections are significant at
the 0.1 kcal/mol level in hydride systems. . Based on the accumulated
experience, a new computational thermochemistry protocol for first-and
second-row main-group systems, to be known as W4 theory, is proposed. Our W4
atomization energies for a number of key species are in excellent agreement
(better than 0.1 kcal/mol on average, 95% confidence intervals narrower than 1
kJ/mol) with the latest experimental data obtained from Active Thermochemical
Tables. A simple {\em a priori} estimate for the importance of post-CCSD(T)
correlation contributions (and hence a pessimistic estimate for the error in a
W2-type calculation) is proposed.Comment: J. Chem. Phys., in press; electronic supporting information available
at http://theochem.weizmann.ac.il/web/papers/w4.htm
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