1,147 research outputs found
Modeling Reactive Wetting when Inertial Effects are Dominant
Recent experimental studies of molten metal droplets wetting high temperature
reactive substrates have established that the majority of triple-line motion
occurs when inertial effects are dominant. In light of these studies, this
paper investigates wetting and spreading on reactive substrates when inertial
effects are dominant using a thermodynamically derived, diffuse interface model
of a binary, three-phase material. The liquid-vapor transition is modeled using
a van der Waals diffuse interface approach, while the solid-fluid transition is
modeled using a phase field approach. The results from the simulations
demonstrate an O \left( t^{-\nicefrac{1}{2}} \right) spreading rate during
the inertial regime and oscillations in the triple-line position when the metal
droplet transitions from inertial to diffusive spreading. It is found that the
spreading extent is reduced by enhancing dissolution by manipulating the
initial liquid composition. The results from the model exhibit good qualitative
and quantitative agreement with a number of recent experimental studies of
high-temperature droplet spreading, particularly experiments of copper droplets
spreading on silicon substrates. Analysis of the numerical data from the model
suggests that the extent and rate of spreading is regulated by the spreading
coefficient calculated from a force balance based on a plausible definition of
the instantaneous interface energies. A number of contemporary publications
have discussed the likely dissipation mechanism in spreading droplets. Thus, we
examine the dissipation mechanism using the entropy-production field and
determine that dissipation primarily occurs in the locality of the triple-line
region during the inertial stage, but extends along the solid-liquid interface
region during the diffusive stage
Polymorphisms in Calpastatin and mu-Calpain Genes Are Associated with Beef Iron Content
The objective of this study was to assess the association of markers in the calpastatin and mu-calpain loci with iron in beef cattle muscle. The population consisted of 259 cross-bred steers from Beefmaster, Brangus, Bonsmara, Romosinuano, Hereford and Angus sires. Total iron and heme iron concentrations were measured. Markers in the calpastatin (referred to as CAST) and mu-calpain (referred to asCAPN4751) genes were used to assess their association with iron levels. The mean and standard error for iron and heme iron content in the population was 35.6 ± 1.3 μg and 27.1 ± 1.4 μg respectively. Significant associations (P \u3c 0.01) of markers were observed for both iron and heme iron content. For CAST, animals with the CC genotype had higher levels of iron and heme iron in longissimus dorsi muscle. ForCAPN4751, individuals with the TT genotype had higher concentrations of iron and heme iron than did animals with the CC and CT genotypes. Genotypes known to be associated with tougher meat were associated with higher levels of iron concentration
Sire Breed Effect on Beef Longissimus Mineral Concentrations and Their Relationships with Carcass and Palatability Traits
The objective of this study was to evaluate sire breed effect on mineral concentration in beef longissimus thoracis (LT) and investigate the correlations between beef mineral concentrations and carcass and palatability traits. Steer progeny (N = 246) from the Germplasm Evaluation project—Cycle VIII were used in this study. In addition to carcass traits, LT was evaluated for mineral concentrations, Warner–Bratzler shear force, and palatability traits. A mixed linear model estimated breed effects on mineral concentrations. No significant sire breed (P ≥ 0.43) or dam breed (P ≥ 0.20) effects were identified for mineral concentrations. Pearson correlation coefficients were calculated among mineral concentrations, carcass, and sensory traits. Zinc concentration was positively correlated (P ≤ 0.05) with total iron (r = 0.14), heme iron (r = 0.13), and magnesium (r = 0.19). Significant (P \u3c 0.05) correlations were identified between non-heme or heme iron and most traits in this study. Magnesium concentration was correlated with all carcass and palatability traits
Signature of the Simplicial Supermetric
We investigate the signature of the Lund-Regge metric on spaces of simplicial
three-geometries which are important in some formulations of quantum gravity.
Tetrahedra can be joined together to make a three-dimensional piecewise linear
manifold. A metric on this manifold is specified by assigning a flat metric to
the interior of the tetrahedra and values to their squared edge-lengths. The
subset of the space of squared edge-lengths obeying triangle and analogous
inequalities is simplicial configuration space. We derive the Lund-Regge metric
on simplicial configuration space and show how it provides the shortest
distance between simplicial three-geometries among all choices of gauge inside
the simplices for defining this metric (Regge gauge freedom). We show
analytically that there is always at least one physical timelike direction in
simplicial configuration space and provide a lower bound on the number of
spacelike directions. We show that in the neighborhood of points in this space
corresponding to flat metrics there are spacelike directions corresponding to
gauge freedom in assigning the edge-lengths. We evaluate the signature
numerically for the simplicial configuration spaces based on some simple
triangulations of the three-sphere (S^3) and three-torus (T^3). For the surface
of a four-simplex triangulation of S^3 we find one timelike direction and all
the rest spacelike over all of the simplicial configuration space. For the
triangulation of T^3 around flat space we find degeneracies in the simplicial
supermetric as well as a few gauge modes corresponding to a positive
eigenvalue. Moreover, we have determined that some of the negative eigenvalues
are physical, i.e. the corresponding eigenvectors are not generators of
diffeomorphisms. We compare our results with the known properties of continuum
superspace.Comment: 24 pages, RevTeX, 4 eps Figures. Submitted to Classical Quantum
Gravit
Quantum Cosmology and Higher-Order Lagrangian Theories
In this paper the quantum cosmological consequences of introducing a term
cubic in the Ricci curvature scalar into the Einstein--Hilbert action are
investigated. It is argued that this term represents a more generic
perturbation to the action than the quadratic correction usually considered. A
qualitative argument suggests that there exists a region of parameter space in
which neither the tunneling nor the no-boundary boundary conditions predict an
epoch of inflation that can solve the horizon and flatness problems of the big
bang model. This is in contrast to the --theory.Comment: 13 pages, LaTeX, preprint FERMILAB-Pub-94/XXX-A, March 199
Supersymmetric Quantization of Anisotropic Scalar-Tensor Cosmologies
In this paper we show that the spatially homogeneous Bianchi type I and
Kantowski-Sachs cosmologies derived from the Brans-Dicke theory of gravity
admit a supersymmetric extension at the quantum level. Global symmetries in the
effective one-dimensional actions characterize both classical and quantum
solutions. A wide family of exact wavefunctions satisfying the supersymmetric
constraints are found. A connection with quantum wormholes is briefly
discussed.Comment: In Press, Class. Quantum Grav. 20 pages, Late
Velocity Selection for Propagating Fronts in Superconductors
Using the time-dependent Ginzburg-Landau equations we study the propagation
of planar fronts in superconductors, which would appear after a quench to zero
applied magnetic field. Our numerical solutions show that the fronts propagate
at a unique speed which is controlled by the amount of magnetic flux trapped in
the front. For small flux the speed can be determined from the linear marginal
stability hypothesis, while for large flux the speed may be calculated using
matched asymptotic expansions. At a special point the order parameter and
vector potential are dual, leading to an exact solution which is used as the
starting point for a perturbative analysis.Comment: 4 pages, 2 figures; submitted to Phys. Rev. Letter
Solutions to the Wheeler-Dewitt Equation Inspired by the String Effective Action
The Wheeler-DeWitt equation is derived from the bosonic sector of the
heterotic string effective action assuming a toroidal compactification. The
spatially closed, higher dimensional Friedmann-Robertson-Walker (FRW) cosmology
is investigated and a suitable change of variables rewrites the equation in a
canonical form. Real- and imaginary-phase exact solutions are found and a
method of successive approximations is employed to find more general power
series solutions. The quantum cosmology of the Bianchi IX universe is also
investigated and a class of exact solutions is found.Comment: 21 pages of plain LaTeX, Fermilab-Pub-93/100-
SGLT2 Inhibitors: Slowing of Chronic Kidney Disease Progression in Type 2 Diabetes
Diabetic kidney disease (DKD) is a topic of increasing concern among clinicians involved in the management of type 2 diabetes mellitus (T2DM). It is a progressive and costly complication associated with increased risk of adverse cardiovascular (CV) and renal outcomes and mortality. Ongoing monitoring of the estimated glomerular filtration (eGFR) rate alongside the urine albumin:creatinine ratio (ACR) is recommended during regular T2DM reviews to enable a prompt DKD diagnosis or to assess disease progression, providing an understanding of adverse risk for each individual. Many people with DKD will progress to end-stage kidney disease (ESKD), requiring renal replacement therapy (RRT), typically haemodialysis or kidney transplantation. A range of lifestyle and pharmacological interventions is recommended to help lower CV risk, slow the advancement of DKD and prevent or delay the need for RRT. Emerging evidence concerning sodium-glucose co-transporter-2 inhibitor (SGLT2i) agents suggests a role for these medicines in slowing eGFR decline, enabling regression of albuminuria and reducing progression to ESKD. Improvements in renal end points observed in SGLT2i CV outcome trials (CVOTs) highlighted the possible impact of these agents in the management of DKD. Data from the canagliflozin CREDENCE trial (Canagliflozin and Renal Events in Diabetes with Established Nephropathy Clinical Evaluation) have since demonstrated the effectiveness of this medicine in reducing the risk of kidney failure and CV events in a population comprising individuals with T2DM and renal disease. CREDENCE was the first SGLT2i study to examine renal outcomes as the primary end point. Real-world studies have reaffirmed these outcomes in routine clinical practice. This article summarises the evidence regarding the use of SGLT2i medicines in slowing the progression of DKD and examines the possible mechanisms underpinning the renoprotective effects of these agents. The relevant national and international guidance for monitoring and treatment of DKD is also highlighted to help clinicians working to support this vulnerable group
Observations of SN 2017ein Reveal Shock Breakout Emission and A Massive Progenitor Star for a Type Ic Supernova
We present optical and ultraviolet observations of nearby type Ic supernova
SN 2017ein as well as detailed analysis of its progenitor properties from both
the early-time observations and the prediscovery Hubble Space Telescope (HST)
images. The optical light curves started from within one day to 275 days
after explosion, and optical spectra range from 2 days to 90 days
after explosion. Compared to other normal SNe Ic like SN 2007gr and SN 2013ge,
\mbox{SN 2017ein} seems to have more prominent C{\footnotesize II} absorption
and higher expansion velocities in early phases, suggestive of relatively lower
ejecta mass. The earliest photometry obtained for \mbox{SN 2017ein} show
indications of shock cooling. The best-fit obtained by including a shock
cooling component gives an estimate of the envelope mass as 0.02
M and stellar radius as 84 R. Examining the
pre-explosion images taken with the HST WFPC2, we find that the SN position
coincides with a luminous and blue point-like source, with an
extinction-corrected absolute magnitude of M8.2 mag and
M7.7 mag.Comparisons of the observations to the theoretical models
indicate that the counterpart source was either a single WR star or a binary
with whose members had high initial masses, or a young compact star cluster. To
further distinguish between different scenarios requires revisiting the site of
the progenitor with HST after the SN fades away.Comment: 28 pages, 19 figures; accepted for publication in The Astrophysical
Journa
- …