12,730 research outputs found
Broadband dielectric spectroscopy on benzophenone: alpha relaxation, beta relaxation, and mode coupling theory
We have performed a detailed dielectric investigation of the relaxational
dynamics of glass-forming benzophenone. Our measurements cover a broad
frequency range of 0.1 Hz to 120 GHz and temperatures from far below the glass
temperature well up into the region of the small-viscosity liquid. With respect
to the alpha relaxation this material can be characterized as a typical
molecular glass former with rather high fragility. A good agreement of the
alpha relaxation behavior with the predictions of the mode coupling theory of
the glass transition is stated. In addition, at temperatures below and in the
vicinity of Tg we detect a well-pronounced beta relaxation of Johari-Goldstein
type, which with increasing temperature develops into an excess wing. We
compare our results to literature data from optical Kerr effect and depolarized
light scattering experiments, where an excess-wing like feature was observed in
the 1 - 100 GHz region. We address the question if the Cole-Cole peak, which
was invoked to describe the optical Kerr effect data within the framework of
the mode coupling theory, has any relation to the canonical beta relaxation
detected by dielectric spectroscopy.Comment: 11 pages, 7 figures; revised version with new Fig. 5 and some smaller
changes according to referees' demand
Cosmic Shear Results from the Deep Lens Survey - II: Full Cosmological Parameter Constraints from Tomography
We present a tomographic cosmic shear study from the Deep Lens Survey (DLS),
which, providing a limiting magnitude r_{lim}~27 (5 sigma), is designed as a
pre-cursor Large Synoptic Survey Telescope (LSST) survey with an emphasis on
depth. Using five tomographic redshift bins, we study their auto- and
cross-correlations to constrain cosmological parameters. We use a
luminosity-dependent nonlinear model to account for the astrophysical
systematics originating from intrinsic alignments of galaxy shapes. We find
that the cosmological leverage of the DLS is among the highest among existing
>10 sq. deg cosmic shear surveys. Combining the DLS tomography with the 9-year
results of the Wilkinson Microwave Anisotropy Probe (WMAP9) gives
Omega_m=0.293_{-0.014}^{+0.012}, sigma_8=0.833_{-0.018}^{+0.011},
H_0=68.6_{-1.2}^{+1.4} km/s/Mpc, and Omega_b=0.0475+-0.0012 for LCDM, reducing
the uncertainties of the WMAP9-only constraints by ~50%. When we do not assume
flatness for LCDM, we obtain the curvature constraint
Omega_k=-0.010_{-0.015}^{+0.013} from the DLS+WMAP9 combination, which however
is not well constrained when WMAP9 is used alone. The dark energy equation of
state parameter w is tightly constrained when Baryonic Acoustic Oscillation
(BAO) data are added, yielding w=-1.02_{-0.09}^{+0.10} with the DLS+WMAP9+BAO
joint probe. The addition of supernova constraints further tightens the
parameter to w=-1.03+-0.03. Our joint constraints are fully consistent with the
final Planck results and also the predictions of a LCDM universe.Comment: Accepted for publication in Ap
Triggered Star Formation in Galaxy Pairs at z=0.08-0.38
We measure the strength, frequency, and timescale of tidally triggered star
formation at redshift z=0.08-0.38 in a spectroscopically complete sample of
galaxy pairs drawn from the magnitude-limited redshift survey of 9,825
Smithsonian Hectospec Lensing Survey (SHELS) galaxies with R<20.3. To examine
the evidence for tidal triggering, we identify a volume-limited sample of major
(|\Delta M_R|1/5) pair galaxies with $M_R <
-20.8 in the redshift range z=0.08-0.31. The size and completeness of the
spectroscopic survey allows us to focus on regions of low local density. The
spectrophotometric calibration enables the use of the 4000 Ang break (D_n4000),
the H\alpha specific star formation rate (SSFR_{H\alpha}), and population
models to characterize the galaxies. We show that D_n4000 is a useful
population classification tool; it closely tracks the identification of
emission line galaxies. The sample of major pair galaxies in regions of low
local density with low D_n4000 demonstrates the expected anti-correlation
between pair-wise projected separation and a set of star formation indicators
explored in previous studies. We measure the frequency of triggered star
formation by comparing the SSFR_{H\alpha} in the volume-limited sample in
regions of low local density: 32 +/-7% of the major pair galaxies have
SSFR_{H\alpha} at least double the median rate of the unpaired field galaxies.
Comparison of stellar population models for pair and for unpaired field
galaxies implies a timescale for triggered star formation of ~300-400 Myr.Comment: 25 pages, 15 figures. Accepted to A
From knowledge dependence to knowledge creation: Industrial growth and the technological advance of the Japanese electronics industry
The thrust of the argument put forward in this paper is that the postwar technological advance of the Japanese electronics industry was in essence a product not a primary cause of industrial growth. We demonstrate that the industry's surge forward resulted from the interaction of a unique combination of political, economic and cultural forces. Business leaders took full advantage by investing on a massive scale in physical, organizational, human and technological resources. It was success in the marketplace and strong cash flows that allowed Japanese firms to import technology on a large scale, invest in scientists and engineers, and progressively develop world class technological capabilities. In establishing themselves as global players, Japanese electronics firms moved over the years from a position of knowledge dependence to one of knowledge creation. We explore how this transformation was achieved and how they learned to control and exploit knowledge creating systems and processes. In particular, we establish the multi-faceted context and complex set of relationships that have conditioned strategic decision making and the creation of technological capabilities
Study of the Depolarized Light Scattering Spectra of Supercooled Liquids by a Simple Mode-Coupling Model
By using simple mode coupling equations, we investigate the depolarized light
scattering spectra of two so-called "fragile" glassforming liquids, salol
(phenylsalicylate) and CKN (Ca_{0.4}K_{0.6}(NO_3)_{1.4}), measured by Cummins
and coworkers. Nonlinear integrodifferential equations for the time evolution
of the density-fluctuations autocorrelation functions are the basic input of
the mode coupling theory. Restricting ourselves to a small set of such
equations, we fit the numerical solution to the experimental spectra. It leads
to a good agreement between model and experiment, which allows us to determine
how a real system explores the parameter space of the model, but it also leads
to unrealistic effective vertices in a temperature range where the theory makes
critical asymptotic predictions. We finally discuss the relevance and the range
of validity of these universal asymptotic predictions when applied to
experimental data on supercooled liquids.Comment: 31 LaTeX pages using overcite.sty, 10 postscript figures, accepted in
J. Chem. Phy
HE 0435-1223: a wide separation quadruple QSO and gravitational lens
We report the discovery of a new gravitationally lensed QSO, at a redshift z
= 1.689, with four QSO components in a cross-shaped arrangement around a bright
galaxy. The maximum separation between images is 2.6 arcsec, enabling a
reliable decomposition of the system. Three of the QSO components have g =
19.6, while component A is about 0.6 mag brighter. The four components have
nearly identical colours, suggesting little if any dust extinction in the
foreground galaxy. The lensing galaxy is prominent in the i band, weaker in r
and not detected in g. Its spatial profile is that of an elliptical galaxy with
a scale length of 12 kpc. Combining the measured colours and a mass
model for the lens, we estimate a most likely redshift range of 0.3 < z < 0.4.
Predicted time delays between the components are \la 10 days. The QSO shows
evidence for variability, with total g band magnitudes of 17.89 and 17.71 for
two epochs separated by months. However, the relative fluxes of the
components did not change, indicating that the variations are intrinsic to the
QSO rather than induced by microlensing.Comment: 7 pages, submitted to Astronomy and Astrophysic
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