447 research outputs found
Low-energy electronic properties of clean CaRuO: elusive Landau quasiparticles
We have prepared high-quality epitaxial thin films of CaRuO with residual
resistivity ratios up to 55. Shubnikov-de Haas oscillations in the
magnetoresistance and a temperature dependence in the electrical
resistivity only below 1.5 K, whose coefficient is substantially suppressed in
large magnetic fields, establish CaRuO as a Fermi liquid (FL) with
anomalously low coherence scale. Non-Fermi liquid (NFL) dependence is
found between 2 and 25 K. The high sample quality allows access to the
intrinsic electronic properties via THz spectroscopy. For frequencies below 0.6
THz, the conductivity is Drude-like and can be modeled by FL concepts, while
for higher frequencies non-Drude behavior, inconsistent with FL predictions, is
found. This establishes CaRuO as a prime example of optical NFL behavior in
the THz range.Comment: 12 pages, 21 figures including supplemental materia
Do biometric parameters improve the quality of optic nerve head measurements with spectral domain optical coherence tomography?
Funding Information: A part of the study data have been presented as a free paper oral presentation ‘ Clinical quality assessment of optic nerve head measurements with spectral domain optical coherence tomography—preliminary results’ in 118. Congress of the DOG (German Society of Ophthalmology) 2020. Publisher Copyright: © 2022, The Author(s).Background: Spectral domain optical coherence tomography (SD-OCT) is a widely applied non-invasive technique for evaluating optic nerve head parameters. The aim of this study was to evaluate the impact of biometric parameters such as the spherical equivalent (SE) and the anterior corneal curvature (ACC) on the peripapillary retinal nerve fiber layer (pRNFL), Bruch’s membrane opening (BMO), and the minimum rim width (MRW) measurements performed by spectral domain optical coherence tomography (SD-OCT) in glaucomatous and healthy eyes. Methods: In this cross-sectional, case–control prospective pilot study, the glaucoma group consisted of 50 patients with previously diagnosed and treated glaucoma and one healthy group of 50 subjects. Two consecutive examinations of pRNFL, BMO, and MRW with SD-OCT for every patient were performed without ACC and objective refraction (imaging 1) and with them (imaging 2). Results: The interclass correlation coefficient (ICC) reflected high agreement between imaging 1 and imaging 2 in both groups. The ICC in the glaucoma and healthy groups for pRNFL (0.99 vs. 0.98), BMO (0.95 vs. 0.97), and MRW (1.0 vs. 1.0) was comparable. Conclusions: Our preliminary data from a small number of eyes showed that the measurements of pRNFL, MRW, and BMO reflected high agreement between both imaging techniques with ACC and objective refraction and without these parameters in subjects with a refractive error up to ± 6.0 diopters. Further studies with participants with higher refractive error are necessary to evaluate the impact of biometric parameters such as SE and ACC on measurements with SD-OCT.publishersversionPeer reviewe
Exact field ionization rates in the barrier suppression-regime from numerical TDSE calculations
Numerically determined ionization rates for the field ionization of atomic
hydrogen in strong and short laser pulses are presented. The laser pulse
intensity reaches the so-called "barrier suppression ionization" regime where
field ionization occurs within a few half laser cycles. Comparison of our
numerical results with analytical theories frequently used shows poor
agreement. An empirical formula for the "barrier suppression ionization"-rate
is presented. This rate reproduces very well the course of the numerically
determined ground state populations for laser pulses with different length,
shape, amplitude, and frequency.
Number(s): 32.80.RmComment: Enlarged and newly revised version, 22 pages (REVTeX) + 8 figures in
ps-format, submitted for publication to Physical Review A, WWW:
http://www.physik.tu-darmstadt.de/tqe
Human Milk Protein Production in Xenografts of Genetically Engineered Bovine Mammary Epithelial Stem Cells
BACKGROUND: In the bovine species milk production is well known to correlate with mammary tissue mass. However, most advances in optimizing milk production relied on improvements of breeding and husbandry practices. A better understanding of the cells that generate bovine mammary tissue could facilitate important advances in milk production and have global economic impact. With this possibility in mind, we show that a mammary stem cell population can be functionally identified and isolated from the bovine mammary gland. We also demonstrate that this stem cell population may be a promising target for manipulating the composition of cow's milk using gene transfer. METHODS AND FINDINGS: We show that the in vitro colony-forming cell assay for detecting normal primitive bipotent and lineage-restricted human mammary clonogenic progenitors are applicable to bovine mammary cells. Similarly, the ability of normal human mammary stem cells to regenerate functional bilayered structures in collagen gels placed under the kidney capsule of immunodeficient mice is shared by a subset of bovine mammary cells that lack aldehyde dehydrogenase activity. We also find that this activity is a distinguishing feature of luminal-restricted bovine progenitors. The regenerated structures recapitulate the organization of bovine mammary tissue, and milk could be readily detected in these structures when they were assessed by immunohistochemical analysis. Transplantation of the bovine cells transduced with a lentivirus encoding human β-CASEIN led to expression of the transgene and secretion of the product by their progeny regenerated in vivo. CONCLUSIONS: These findings point to a common developmental hierarchy shared by human and bovine mammary glands, providing strong evidence of common mechanisms regulating the maintenance and differentiation of mammary stem cells from both species. These results highlight the potential of novel engineering and transplant strategies for a variety of commercial applications including the production of modified milk components for human consumption
Clinical Pharmacogenetics Implementation Consortium Guideline for CYP2D6 and CYP2C19 Genotypes and Dosing of Tricyclic Antidepressants
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109971/1/cptclpt20132.pd
The Gluon Propagator without lattice Gribov copies
We study the gluon propagator in quenched lattice QCD using the Laplacian
gauge which is free of lattice Gribov copies. We compare our results with those
obtained in the Landau gauge on the lattice, as well as with various
approximate solutions of the Dyson Schwinger equations. We find a finite value
for the renormalized zero-momentum propagator
(taking our renormalization point at 1.943 GeV), and a pole mass MeV.Comment: Discussion of the renormalized gluon propagator and of the Laplacian
gauge fixing procedure extended. Version to appear in Phys. Rev. D. 15 pages,
8 figure
Spatial Symmetry of Superconducting Gap in YBa2Cu3O7-\delta Obtained from Femtosecond Spectroscopy
The polarized femtosecond spectroscopies obtained from well characterized
(100) and (110) YBa2Cu3O7-\delta thin films are reported. This bulk-sensitive
spectroscopy, combining with the well-textured samples, serves as an effective
probe to quasiparticle relaxation dynamics in different crystalline
orientations. The significant anisotropy in both the magnitude of the
photoinduced transient reflectivity change and the characteristic relaxation
time indicates that the nature of the relaxation channel is intrinsically
different in various axes and planes. By the orientation-dependent analysis,
d-wave symmetry of the bulk-superconducting gap in cuprate superconductors
emerges naturally.Comment: 8 pages, 4 figures. To be published in Physical Review B, Rapid
Communication
Sigma Terms of Light-Quark Hadrons
A calculation of the current-quark mass dependence of hadron masses can help
in using observational data to place constraints on the variation of nature's
fundamental parameters. A hadron's sigma-term is a measure of this dependence.
The connection between a hadron's sigma-term and the Feynman-Hellmann theorem
is illustrated with an explicit calculation for the pion using a rainbow-ladder
truncation of the Dyson-Schwinger equations: in the vicinity of the chiral
limit sigma_pi = m_pi/2. This truncation also provides a decent estimate of
sigma_rho because the two dominant self-energy corrections to the rho-meson's
mass largely cancel in their contribution to sigma_rho. The truncation is less
accurate for the omega, however, because there is little to compete with an
omega->rho+pi self-energy contribution that magnifies the value of sigma_omega
by ~25%. A Poincare' covariant Faddeev equation, which describes baryons as
composites of confined-quarks and -nonpointlike-diquarks, is solved to obtain
the current-quark mass dependence of the masses of the nucleon and Delta, and
thereby sigma_N and sigma_Delta. This "quark-core" piece is augmented by the
"pion cloud" contribution, which is positive. The analysis yields sigma_N~60MeV
and sigma_Delta~50MeV.Comment: 22 pages, reference list expande
Asymptotic Scaling and Infrared Behavior of the Gluon Propagator
The Landau gauge gluon propagator for the pure gauge theory is evaluated on a
32^3x64 lattice with a physical volume of (3.35^3x6.7)fm^4. Comparison with two
smaller lattices at different lattice spacings allows an assessment of finite
volume and finite lattice spacing errors. Cuts on the data are imposed to
minimize these errors. Scaling of the gluon propagator is verified between
beta=6.0 and beta=6.2. The tensor structure is evaluated and found to be in
good agreement with the Landau gauge form, except at very small momentum
values, where some small finite volume errors persist. A number of functional
forms for the momentum dependence of the propagator are investigated. The form
D(q^2)=D_ir+D_uv, where D_ir(q^2) ~ (q^2+M^2)^-\eta and D_uv is an infrared
regulated one-loop asymptotic form, is found to provide an adequate description
of the data over the entire momentum region studied - thereby bridging the gap
between the infrared confinement region and the ultraviolet asymptotic region.
The best estimate for the exponent \eta is 3.2(+0.1/-0.2)(+0.2/-0.3), where the
first set of errors represents the uncertainty associated with varying the
fitting range, while the second set of errors reflects the variation arising
from different choices of infrared regulator in D_uv. Fixing the form of D_uv,
we find that the mass parameter M is (1020+/-100)MeV.Comment: 37 pages, RevTeX, 16 postscript figures, 7 gif figures. Revised
version accepted for publication in Phys. Rev. D. Model functions and
discussion of asymptotic behaviour modified; all model fits have been redone.
This paper, including postscript version of all figures, can be found at
http://www.physics.adelaide.edu.au/~jskuller/papers
Infrared behavior of the gluon propagator in lattice Landau gauge: the three-dimensional case
We evaluate numerically the three-momentum-space gluon propagator in the
lattice Landau gauge, for three-dimensional pure-SU(2) lattice gauge theory
with periodic boundary conditions. Simulations are done for nine different
values of the coupling , from (strong coupling) to (in the scaling region), and for lattice sizes up to . In the
limit of large lattice volume we observe, in all cases, a gluon propagator
decreasing for momenta smaller than a constant value . From our data
we estimate MeV. The result of a gluon propagator
decreasing in the infrared limit has a straightforward interpretation as
resulting from the proximity of the so-called first Gribov horizon in the
infrared directions.Comment: 14 pages, BI-TP 99/03 preprint, correction in the Acknowledgments
section. To appear in Phys.Rev.
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