54,468 research outputs found
A New General Method to Generate Random Modal Formulae for Testing Decision Procedures
The recent emergence of heavily-optimized modal decision procedures has
highlighted the key role of empirical testing in this domain. Unfortunately,
the introduction of extensive empirical tests for modal logics is recent, and
so far none of the proposed test generators is very satisfactory. To cope with
this fact, we present a new random generation method that provides benefits
over previous methods for generating empirical tests. It fixes and much
generalizes one of the best-known methods, the random CNF_[]m test, allowing
for generating a much wider variety of problems, covering in principle the
whole input space. Our new method produces much more suitable test sets for the
current generation of modal decision procedures. We analyze the features of the
new method by means of an extensive collection of empirical tests
Implications of the isotope effects on the magnetization, magnetic torque and susceptibility
We analyze the magnetization, magnetic torque and susceptibility data of
La2-xSrxCu(16,18)O4 and YBa2(63,65)CuO7-x near Tc in terms of the universal
3D-XY scaling relations. It is shown that the isotope effect on Tc mirrors that
on the anisotropy. Invoking the generic behavior of the anisotropy the doping
dependence of the isotope effects on the critical properties, including Tc,
correlation lengths and magnetic penetration depths are traced back to a change
of the mobile carrier concentration.Comment: 5 pages, 3 figure
Scaling of broadband dielectric data of glass-forming liquids and plastic crystals
The Nagel-scaling and the modified scaling procedure proposed recently by
Dendzik et al. have been applied to broadband dielectric data on two glass-
forming liquids (glycerol and propylene carbonate) and three plastic crystals
(ortho-carborane, meta-carborane, and 1-cyano-adamantane). Our data extend the
upper limit of the abscissa range to considerably higher values than in
previously published analyses. At the highest frequencies investigated,
deviations from a single master curve show up which are most pronounced in the
Dendzik-scaling plot. The loss curves of the plastic crystals do not scale in
the Nagel-plot, but they fall onto a separate master curve in the Dendzik-plot.
In addition, we address the question of a possible divergence of the static
susceptibility near the Vogel-Fulcher temperature. For this purpose, the
low-temperature evolution of the high-frequency wing of the dielectric loss
peaks is investigated in detail. No convincing proof for such a divergence can
be deduced from the present broadband data.Comment: 7 pages including 6 figures submitted to Eur. Phys. J.
The role of Lambda in the cosmological lens equation
The cosmological constant Lambda affects cosmological gravitational lensing.
Effects due to Lambda can be studied in the framework of the Schwarzschild-de
Sitter spacetime. Two novel contributions, which can not be accounted for by a
proper use of angular diameter distances, are derived. First, a term 2m b
Lambda/3 has to be added to the bending angle, where "m" is the lens mass and
"b" the impact parameter. Second, Lambda brings about a difference in the
redshifts of multiple images. Both effects are quite small for real
astrophysical systems (contribution to the bending < 0.1 microarcsec and
difference in redshift < 10^{-7}).Comment: 4 pages. (Univ. Zuerich); v2: presentation improved, discussion
extended, references to papers posted after the v1-version added. In press on
Phys. Rev. Let
Image Properties of Embedded Lenses
We give analytic expressions for image properties of objects seen around
point mass lenses embedded in a flat CDM universe. An embedded lens in
an otherwise homogeneous universe offers a more realistic representation of the
lens's gravity field and its associated deflection properties than does the
conventional linear superposition theory. Embedding reduces the range of the
gravitational force acting on passing light beams thus altering all quantities
such as deflection angles, amplifications, shears and Einstein ring sizes.
Embedding also exhibits the explicit effect of the cosmological constant on
these same lensing quantities. In this paper we present these new results and
demonstrate how they can be used. The effects of embedding on image properties,
although small i.e., usually less than a fraction of a percent, have a more
pronounced effect on image distortions in weak lensing where the effects can be
larger than 10%. Embedding also introduces a negative surface mass density for
both weak and strong lensing, a quantity altogether absent in conventional
Schwarzschild lensing. In strong lensing we find only one additional quantity,
the potential part of the time delay, which differs from conventional lensing
by as much as 4%, in agreement with our previous numerical estimates.Comment: 17 pages, 6 figure
The excess wing in the dielectric loss of glass-forming ethanol: A relaxation process
A detailed dielectric investigation of liquid, supercooled liquid, and glassy
ethanol reveals a third relaxation process, in addition to the two processes
already known. The relaxation time of the newly detected process exhibits
strong deviations from thermally activated behavior. Most important, this
process is the cause of the apparent excess wing, which was claimed to be
present in the dielectric loss spectra of glass-forming ethanol. In addition,
marked deviations of the spectra of ethanol from the scaling proposed by Dixon
and Nagel have been detected.Comment: 8 pages including 4 figures submitted to Phys. Rev.
BILIPROTEINS FROM THE BUTTERFLY Pieris brassicae STUDIED BY TIME-RESOLVED FLUORESCENCE AND COHERENT ANTI-STOKES RAMAN SPECTROSCOPY
The fluorescence decay time of the biliverdin IX7 chromophore present in biliproteins isolated from Pieris brassicae is determined to be 44 ± 3 ps. This value suggests a cyclic helical chromophore structure. The vibrational frequencies determined by CARS-spectroscopy are compared with those of model compounds. The data confirm that the chromophore in the protein-bound state adopts a cyclic-helical, flexible conformation
The Excess Wing in the Dielectric Loss of Glass-Formers: A Johari-Goldstein beta-Relaxation?
Dielectric loss spectra of glass-forming propylene carbonate and glycerol at
temperatures above and below T_g are presented. By performing aging experiments
lasting up to five weeks, equilibrium spectra below T_g have been obtained.
During aging, the excess wing, showing up as a second power law at high
frequencies, develops into a shoulder. The results strongly suggest that the
excess wing, observed in a variety of glass formers, is the high-frequency
flank of a beta-relaxation.Comment: submitted to Phys. Rev. Lett., 4 figures, revised version after
referee report
- …