1,721 research outputs found
Fast label-free multilayered histology-like imaging of human breast cancer by photoacoustic microscopy
The goal of breast-conserving surgery is to completely remove all of the cancer. Currently, no intraoperative tools can microscopically analyze the entire lumpectomy specimen, which results in 20 to 60% of patients undergoing second surgeries to achieve clear margins. To address this critical need, we have laid the foundation for the development of a device that could allow accurate intraoperative margin assessment. We demonstrate that by taking advantage of the intrinsic optical contrast of breast tissue, photoacoustic microscopy (PAM) can achieve multilayered histology-like imaging of the tissue surface. The high correlation of the PAM images to the conventional histologic images allows rapid computations of diagnostic features such as nuclear size and packing density, potentially identifying small clusters of cancer cells. Because PAM does not require tissue processing or staining, it can be performed promptly and intraoperatively, enabling immediate directed re-excision and reducing the number of second surgeries
Single measurement to predict potential mineralizable nitrogen
Non-Peer ReviewedAlthough soil nitrate nitrogen (N) has been used as a basis for N fertilizer recommendation in western Canada, potential mineralizable N should be (or is) a more accurate indicator of the N supplying power of the soil. Potential mineralizable N, analyzed by extraction with hot KCl, and organic matter content were determined on the AESA Soil Quality Benchmark Sites in Alberta. Using these results, we developed an approach to estimate Nt from soil organic matter, based on the equation Nt=No(1-e-kt)y, and validated the calculated Nt with the hot KCl extracted N. Results indicated that the potential mineralizable N released from soil differed among ecoregions and slope positions. Potential mineralizable N is lower in southern Alberta than central Alberta. The lower slopes released more N than higher slope positions. Nt released in soil over the growing season correlated well with hot KCl extracted N in three different slope positions.
However, variability of Nt in the upper slope position was greater than middle and lower slopes due to a shallow A horizon and variable soil moisture during the growing season. After removal of outliers (9% of the total data set), the values of R2 (regression of hot KCl with calculated Nt) are 0.529, 0.576 and 0.627 for upper, middle and lower slope position, respectively. Using calculated Nt results, a potential mineralizable map in Alberta has been developed. This map will guide producers to manage soil as well as fertilizer N
Genome-wide scan using DArT markers for selection footprints in six-rowed naked barley from the Tibetan Plateau
As one of the worldâs earliest domesticated crops, barley is a model species for the study of evolution and domestication. Domestication is an evolutionary process whereby a population adapts, through selection; to new environments created by human cultivation. We describe the genome-scanning of molecular diversity to assess the evolution of barley in the Tibetan Plateau. We used 667 Diversity Arrays Technology (DArT) markers to genotype 185 barley landraces and wild barley accessions from the Tibetan Plateau. Genetic diversity in wild barley was greater than in landraces at both genome and chromosome levels, except for chromosome 3H. Landraces and wild barley accessions were clearly differentiated genetically, but a limited degree of introgression was still evident. Significant differences in diversity between barley subspecies at the chromosome level were observed for genes known to be related to physiological and phenotypical traits, disease resistance, abiotic stress tolerance, malting quality and agronomic traits. Selection on the genome of six-rowed naked barley has shown clear multiple targets related to both its specific end-use and the extreme environment in Tibet. Our data provide a platform to identify the genes and genetic mechanisms that underlie phenotypic changes, and provide lists of candidate domestication genes for modified breeding strategies
Overcoming the compensation of acceptors in GaN:Mg by defect complex formation
In GaN:Mg, the MgGa acceptor is compensated extensively by the formation of nitrogen vacancies (VN) and Mg interstitials (Mgi). However, we show that such compensation can be overcome by forming two kinds of Mg-rich complexes: one that contains VN and the other that contains only MgGa and Mgi. Such complexing not only neutralizes VN and Mgi but also forms better complex acceptors that have lower formation energies and smaller hole localization energies than isolated MgGa. Our results help explain the different doping behaviors in samples grown by different methods
Vortex Rings in two Component Bose-Einstein Condensates
We study the structure of the vortex core in two-component Bose-Einstein
condensates. We demonstrate that the order parameter may not vanish and the
symmetry may not be restored in the core of the vortex. In this case such
vortices can form vortex rings known as vortons in particle physics literature.
In contrast with well-studied superfluid , where similar vortex rings can
be stable due to Magnus force only if they move, the vortex rings in
two-component BECs can be stable even if they are at rest. This beautiful
effect was first discussed by Witten in the cosmic string context, where it was
shown that the stabilization occurs due to condensation of the second component
of the field in the vortex core. This second condensate trapped in the core may
carry a current along the vortex ring counteracting the effect of string
tension that causes the loop to shrink. We speculate that such vortons may have
been already observed in the laboratory. We also speculate that the
experimental study of topological structures in BECs can provide a unique
opportunity to study cosmology and astrophysics by doing laboratory
experiments.Comment: 21 pages, 2 figure
Phase diagram and optical conductivity of the one-dimensional spinless Holstein model
The effects of quantum lattice fluctuations on the Peierls transition and the
optical conductivity in the one-dimensional Holstein model of spinless fermions
have been studied by developing an analytical approach, based on the unitary
transformation method. We show that when the electron-phonon coupling constant
decreases to a finite critical value the Peierls dimerization is destroyed by
the quantum lattice fluctuations. The dimerization gap is much more reduced by
the quantum lattice fluctuations than the phonon order parameter. The
calculated optical conductivity does not have the inverse-square-root
singularity but have a peak above the gap edge and there exists a significant
tail below the peak. The peak of optical-conductivity spectrum is not directly
corresponding to the dimerized gap. Our results of the phase diagram and the
spectral-weight function agree with those of the density matrix renormalization
group and the exact diagonalization methods.Comment: 9 pages, 4 figures include
Financial correlations at ultra-high frequency: theoretical models and empirical estimation
A detailed analysis of correlation between stock returns at high frequency is
compared with simple models of random walks. We focus in particular on the
dependence of correlations on time scales - the so-called Epps effect. This
provides a characterization of stochastic models of stock price returns which
is appropriate at very high frequency.Comment: 22 pages, 8 figures, 1 table, version to appear in EPJ
Linear Contraction Behavior of Low-Carbon, Low-Alloy Steels During and After Solidification Using Real-Time Measurements
A technique for measuring the linear contraction during and after solidification of low-alloy steel was developed and used for examination of two commercial low-carbon and low-alloy steel grades. The effects of several experimental parameters on the contraction were studied. The solidification contraction behavior was described using the concept of rigidity in a solidifying alloy, evolution of the solid fraction, and the microstructure development during solidification. A correlation between the linear contraction properties in the solidification range and the hot crack susceptibility was proposed and used for the estimation of hot cracking susceptibility for two studied alloys and verified with the real casting practice. The technique allows estimation of the contraction coefficient of commercial steels in a wide range of temperatures and could be helpful for computer simulation and process optimization during continuous casting. © 2013 The Minerals, Metals & Materials Society and ASM International
Chiral Logs in Quenched QCD
The quenched chiral logs are examined on a lattice with
Iwasaki gauge action and overlap fermions. The pion decay constant is
used to set the lattice spacing, . With pion mass as low
as , we see the quenched chiral logs clearly in
and , the pseudoscalar decay constant. We analyze the data
to determine how low the pion mass needs to be in order for the quenched
one-loop chiral perturbation theory (PT) to apply. With the constrained
curve-fitting method, we are able to extract the quenched chiral log parameter
together with other low-energy parameters. Only for do we obtain a consistent and stable fit with a constant
which we determine to be 0.24(3)(4) (at the chiral scale ). By comparing to the lattice, we estimate the
finite volume effect to be about 2.7% for the smallest pion mass. We also
fitted the pion mass to the form for the re-summed cactus diagrams and found
that its applicable region is extended farther than the range for the one-loop
formula, perhaps up to MeV. The scale independent
is determined to be 0.20(3) in this case. We study the quenched
non-analytic terms in the nucleon mass and find that the coefficient
in the nucleon mass is consistent with the prediction of one-loop PT\@.
We also obtain the low energy constant from . We conclude from
this study that it is imperative to cover only the range of data with the pion
mass less than in order to examine the chiral behavior of
the hadron masses and decay constants in quenched QCD and match them with
quenched one-loop PT\@.Comment: 37 pages and 24 figures, pion masses are fitted to the form for the
re-summed cactus diagrams, figures added, to appear in PR
Measurement of Pion Enhancement at Low Transverse Momentum and of the Delta-Resonance Abundance in Si-Nucleus Collisions at AGS Energy
We present measurements of the pion transverse momentum (p_t) spectra in
central Si-nucleus collisions in the rapidity range 2.0<y<5.0 for p_t down to
and including p_t=0. The data exhibit an enhanced pion yield at low p_t
compared to what is expected for a purely thermal spectral shape. This
enhancement is used to determine the Delta-resonance abundance at freeze-out.
The results are consistent with a direct measurement of the Delta-resonance
yield by reconstruction of proton-pion pairs and imply a temperature of the
system at freeze-out close to 140 MeV.Comment: 12 pages + 4 figures (uuencoded at end-of-file
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