29,166 research outputs found
International Stock Market Efficiency: A Non-Bayesian Time-Varying Model Approach
This paper develops a non-Bayesian methodology to analyze the time-varying
structure of international linkages and market efficiency in G7 countries. We
consider a non-Bayesian time-varying vector autoregressive (TV-VAR) model, and
apply it to estimate the joint degree of market efficiency in the sense of Fama
(1970, 1991). Our empirical results provide a new perspective that the
international linkages and market efficiency change over time and that their
behaviors correspond well to historical events of the international financial
system.Comment: 21 pages, 2 tables, 6 figure
Gauss-Bonnet Chameleon Mechanism of Dark Energy
As a model of the current accelerated expansion of the universe, we consider
a model of the scalar-Einstein-Gauss-Bonnet gravity. This model includes the
propagating scalar modes, which might give a large correction to the Newton
law. In order to avoid this problem, we propose an extension of the Chameleon
mechanism where the scalar mode becomes massive due to the coupling with the
Gauss-Bonnet term. Since the Gauss-Bonnet invariant does not vanish near the
earth or in the Solar System, even in the vacuum, the scalar mode is massive
even in the vacuum and the correction to the Newton law could be small. We also
discuss about the possibility that the model could describe simultaneously the
inflation in the early universe, in addition to the current accelerated
expansion.Comment: LaTeX 11 pages, no figur
Optimization of the Ballistic Guide Design for the SNS FNPB 8.9 A Neutron Line
The optimization of the ballistic guide design for the SNS Fundamental
Neutron Physics Beamline 8.9 A line is described. With a careful tuning of the
shape of the curve for the tapered section and the width of the straight
section, this optimization resulted in more than 75% increase in the neutron
flux exiting the 33 m long guide over a straight m=3.5 guide with the same
length.Comment: 21 pages, 13 figures; added a paragraph on existing ballistic guides
to respond to referee comments; accepted for publication in Nuclear Inst. and
Methods in Physics Research,
Continuous vacua in bilinear soliton equations
We discuss the freedom in the background field (vacuum) on top of which the
solitons are built. If the Hirota bilinear form of a soliton equation is given
by A(D_{\vec x})\bd GF=0,\, B(D_{\vec x})(\bd FF - \bd GG)=0 where both
and are even polynomials in their variables, then there can be a continuum
of vacua, parametrized by a vacuum angle . The ramifications of this
freedom on the construction of one- and two-soliton solutions are discussed. We
find, e.g., that once the angle is fixed and we choose
as the physical quantity, then there are four different solitons (or kinks)
connecting the vacuum angles , (defined modulo
). The most interesting result is the existence of a ``ghost'' soliton; it
goes over to the vacuum in isolation, but interacts with ``normal'' solitons by
giving them a finite phase shift.Comment: 9 pages in Latex + 3 figures (not included
Oscillator strengths and line widths of dipole-allowed transitions in ÂčâŽNâ between 89.7 and 93.5ânm
Line oscillator strengths in the 20 electric dipole-allowed bands of ÂčâŽNâ in the 89.7â93.5nm (111480â106950cmâ»Âč) region are reported from photoabsorptionmeasurements at an instrumental resolution of âŒ6mĂ
(0.7cmâ»Âč) full width at half maximum. The absorptionspectrum comprises transitions to vibrational levels of the 3pÏᔀcâČâÂčΣᔀâș, 3pÏᔀc³Πᔀ, and 3sÏgoâÂčΠᔀRydberg states and of the bâČÂčΣᔀâș and bÂčΠᔀ valence states. The J dependences of band f values derived from the experimental line f values are reported as polynomials in JâČ(JâČ+1) and are extrapolated to JâČ=0 in order to facilitate comparisons with results of coupled Schrödinger-equation calculations. Most bands in this study are characterized by a strong J dependence of the band f values and display anomalous P-, Q-, and R-branch intensity patterns. Predissociation line widths, which are reported for 11 bands, also exhibit strong J dependences. The f value and line width patterns can inform current efforts to develop comprehensive spectroscopic models that incorporate rotational effects and predissociation mechanisms, and they are critical for the construction of realistic atmospheric radiative-transfer models.This work was supported in part by NASA Grant No.
NNG05GA03G to Wellesley College and Australian Research
Council Discovery Program Grant No. DP0558962
Variable coordination of amine functionalised N-heterocyclic carbene ligands to Ru, Rh and Rr: C-H and N-H activation and catalytic transfer hydrogenation
Chelating amine and amido complexes of late transition metals are highly valuable bifunctional catalysts in organic synthesis, but complexes of bidentate amineâNHC and amidoâNHC ligands are scarce. Hence, we report the reactions of a secondary-amine functionalised imidazolium salt 2a and a primary-amine functionalised imidazolium salt 2b with [( p -cymene)RuCl 2 ] 2 and [Cp*MCl 2 ] 2 (M = Rh, Ir). Treating 2a with [Cp*MCl 2 ] 2 and NaOAc gave the cyclometallated compounds Cp*M(C,C)I (M = Rh, 3 ;M = Ir, 4 ), resulting from aromatic CâH activation. In contrast, treating 2b with [( p -cymene)RuCl 2 ] 2 ,Ag 2 O and KI gave the amineâNHC complex [( p -cymene)Ru(C,NH 2 )I]I ( 5 ). The reaction of 2b with [Cp*MCl 2 ] 2 (M = Rh, Ir), NaO t Bu and KI gave the amineâNHC complex [Cp*Rh(NH 2 )I]I ( 6 ) or the amidoâNHC complex Cp*Ir(C,NH)I ( 7 ); both protonation states of the Ir complex could be accessed: treating 7 with trifluoroacetic acid gave the amineâNHC complex [Cp*Ir(C,NH 2 )I][CF 3 CO 2 ]( 8 ). These are the first primary amineâ or amidoâNHC complexes of Rh and Ir. Solid-state structures of the complexes 3â8 have been determined by single crystal X-ray diffraction. Complexes 5 , 6 and 7 are pre-catalysts for the catalytic transfer hydrogenation of acetophenone to 1-phenylethanol, with ruthenium complex 5 demonstrating especially high reactivity
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