1,098 research outputs found
Applying a biodeposition layer to increase the bond of a repair mortar on a mortar substrate
One of the major concerns in infrastructure repair is a sufficient bond between the substrate and the repair material, especially for the long-term performance and durability of the repaired structure. In this study, the bond of the repair material on the mortar substrate is promoted via the biodeposition of a calcium carbonate layer by a ureolytic bacterium. X-ray diffraction and scanning electron microscopy were used to examine the interfaces between the repair material and the substrate, as well as the polymorph of the deposited calcium carbonate. The approximately 50 mu m thick biodeposition film on the mortar surface mostly consisted of calcite and vaterite. Both the repair material and the substrate tended to show a good adherence to that layer. The bond, as assessed by slant shear specimen testing, was improved by the presence of the biodeposition layer. A further increase was found when engineering the substrate surface using a structured pattern layer of biodeposition. (C) 2017 Elsevier Ltd. All rights reserved
Liquid-gas phase transition in nuclear matter including strangeness
We apply the chiral SU(3) quark mean field model to study the properties of
strange hadronic matter at finite temperature. The liquid-gas phase transition
is studied as a function of the strangeness fraction. The pressure of the
system cannot remain constant during the phase transition, since there are two
independent conserved charges (baryon and strangeness number). In a range of
temperatures around 15 MeV (precise values depending on the model used) the
equation of state exhibits multiple bifurcates. The difference in the
strangeness fraction between the liquid and gas phases is small when they
coexist. The critical temperature of strange matter turns out to be a
non-trivial function of the strangeness fraction.Comment: 15 pages, 7 figure
Rotational states in deformed nuclei: An analytic approach
The consequences of the spontaneous breaking of rotational symmetry are
investigated in a field theory model for deformed nuclei, based on simple
separable interactions. The crucial role of the Ward-Takahashi identities to
describe the rotational states is emphasized. We show explicitly how the rotor
picture emerges from the isoscalar Goldstone modes, and how the two-rotor model
emerges from the isovector scissors modes. As an application of the formalism,
we discuss the M1 sum rules in deformed nuclei, and make connection to
empirical information.Comment: 19 pages, 9 figure
Zero Modes in Electromagnetic Form Factors of the Nucleon in a Light-Cone Diquark Model
We use a diquark model of the nucleon to calculate the electromagnetic form
factors of the nucleon described as a scalar and axialvector diquark bound
state. We provide an analysis of the zero-mode contribution in the diquark
model. We find there are zero-mode contributions to the form factors arising
from the instantaneous part of the quark propagator, which cannot be neglected
compared with the valence contribution but can be removed by the choice of wave
function. We also find that the charge and magnetic radii and magnetic moment
of the proton can be reproduced, while the magnetic moment of the neutron is
too small. The dipole shape of the form factors, and
can be reproduced. The ratio decreases
with but too fast.Comment: 22 pages, 6 pages, accepted by J.Phys.
A Revised Broad-Line Region Radius and Black Hole Mass for the Narrow-Line Seyfert 1 NGC 4051
We present the first results from a high sampling rate, multi-month
reverberation mapping campaign undertaken primarily at MDM Observatory with
supporting observations from telescopes around the world. The primary goal of
this campaign was to obtain either new or improved Hbeta reverberation lag
measurements for several relatively low luminosity AGNs. We feature results for
NGC 4051 here because, until now, this object has been a significant outlier
from AGN scaling relationships, e.g., it was previously a ~2-3sigma outlier on
the relationship between the broad-line region (BLR) radius and the optical
continuum luminosity - the R_BLR-L relationship. Our new measurements of the
lag time between variations in the continuum and Hbeta emission line made from
spectroscopic monitoring of NGC 4051 lead to a measured BLR radius of R_BLR =
1.87 (+0.54 -0.50) light days and black hole mass of M_BH = 1.73 (+0.55 -0.52)
x 10^6 M_sun. This radius is consistent with that expected from the R_BLR-L
relationship, based on the present luminosity of NGC 4051 and the most current
calibration of the relation by Bentz et al. (2009a). We also present a
preliminary look at velocity-resolved Hbeta light curves and time delay
measurements, although we are unable to reconstruct an unambiguous
velocity-resolved reverberation signal.Comment: 38 pages, 7 figures, accepted for publication in ApJ, changes from v1
reflect suggestions from anonymous refere
Diquarks: condensation without bound states
We employ a bispinor gap equation to study superfluidity at nonzero chemical
potential: mu .neq. 0, in two- and three-colour QCD. The two-colour theory,
QC2D, is an excellent exemplar: the order of truncation of the quark-quark
scattering kernel: K, has no qualitative impact, which allows a straightforward
elucidation of the effects of mu when the coupling is strong. In rainbow-ladder
truncation, diquark bound states appear in the spectrum of the three-colour
theory, a defect that is eliminated by an improvement of K. The corrected gap
equation describes a superfluid phase that is semi-quantitatively similar to
that obtained using the rainbow truncation. A model study suggests that the
width of the superfluid gap and the transition point in QC2D provide reliable
quantitative estimates of those quantities in QCD.Comment: 7 pages, 3 figures, REVTEX, epsfi
Percolative properties of hard oblate ellipsoids of revolution with a soft shell
We present an in-depth analysis of the geometrical percolation behavior in
the continuum of random assemblies of hard oblate ellipsoids of revolution.
Simulations where carried out by considering a broad range of aspect-ratios,
from spheres up to aspect-ratio 100 plate-like objects, and with various
limiting two particle interaction distances, from 0.05 times the major axis up
to 4.0 times the major axis. We confirm the widely reported trend of a
consistent lowering of the hard particle critical volume fraction with the
increase of the aspect-ratio. Moreover, assimilating the limiting interaction
distance to a shell of constant thickness surrounding the ellipsoids, we
propose a simple relation based on the total excluded volume of these objects
which allows to estimate the critical concentration from a quantity which is
quasi-invariant over a large spectrum of limiting interaction distances.
Excluded volume and volume quantities are derived explicitly.Comment: 11 pages, 8 figure
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