577 research outputs found
Should we perform multiparametric magnetic resonance imaging of the bladder before transurethral resection of bladder? Time to reconsider the rules
We would like to congratulate Ueno and colleagues [1] on their paper on diagnostic accuracy and interobserver agreement for the new Vesical Imaging-Reporting and Data System (VI-RADS) [2] for muscle-invasive bladder cancer (MIBC) in this issue of European Urology. Their report on 74 patients who underwent multiparametric magnetic resonance imaging (mpMRI) before transurethral resection of bladder tumor (TURBT) raises great interest in the RADS
(Reporting and Data Systems) era. They address the questions of reproducibility and diagnostic performance of mpMRI in the setting of bladder ca (BC), in which potential applications of this imaging technique have seen constant growth in the past decades without a definitive role having been identified
Observation of a Transient Magnetization Plateau in a Quantum Antiferromagnet on the Kagome Lattice
The magnetization process of an S=1/2 antiferromagnet on the kagome lattice,
[Cu_3(titmb)_2(OCOCH_3)_6]H_2O {titmb= 1,3,5-tris(imidazol-1-ylmethyl)-2,4,6
trimethylbenzene} has been measured at very low temperatures in both pulsed and
steady fields. We have found a new dynamical behavior in the magnetization
process: a plateau at one third of the saturation magnetization appears in the
pulsed field experiments for intermediate sweep rates of the magnetic field and
disappears in the steady field experiments. A theoretical analysis using exact
diagonalization yields J_1=-19K and J_2=6K, for the nearest neighbor and second
nearest neighbor interactions, respectively. This set of exchange parameters
explains the very low saturation field and the absence of the plateau in the
thermodynamic equilibrium as well as the two-peak feature in the magnetic heat
capacity. Supported by numerical results we argue that a dynamical order by
disorder phenomenon could explain the transient appearance of the 1/3 plateau
in pulsed field experiments.Comment: 7 pages, 5 figure
Chandra detection of extended X-ray emission from the recurrent nova RS Ophiuchi
Radio, infrared, and optical observations of the 2006 eruption of the
symbiotic recurrent nova RS Ophiuchi (RS Oph) showed that the explosion
produced non-spherical ejecta. Some of this ejected material was in the form of
bipolar jets to the east and west of the central source. Here we describe Xray
observations taken with the Chandra X-ray Observatory one and a half years
after the beginning of the outburst that reveal narrow, extended structure with
a position angle of approximately 300 degrees (east of north). Although the
orientation of the extended feature in the X-ray image is consistent with the
readout direction of the CCD detector, extensive testing suggests that the
feature is not an artifact. Assuming it is not an instrumental effect, the
extended X-ray structure shows hot plasma stretching more than 1,900 AU from
the central binary (taking a distance of 1.6 kpc). The X-ray emission is
elongated in the northwest direction - in line with the extended infrared
emission and some minor features in the published radio image. It is less
consistent with the orientation of the radio jets and the main bipolar optical
structure. Most of the photons in the extended X-ray structure have energies of
less than 0.8 keV. If the extended X-ray feature was produced when the nova
explosion occurred, then its 1".2 length as of 2007 August implies that it
expanded at an average rate of more than 2 mas/d, which corresponds to a flow
speed of greater than 6,000 km/s (d/1.6 kpc) in the plane of the sky. This
expansion rate is similar to the earliest measured expansion rates for the
radio jets.Comment: accepted in Ap
Nonuniform Neutron-Rich Matter and Coherent Neutrino Scattering
Nonuniform neutron-rich matter present in both core-collapse supernovae and
neutron-star crusts is described in terms of a semiclassical model that
reproduces nuclear-matter properties and includes long-range Coulomb
interactions. The neutron-neutron correlation function and the corresponding
static structure factor are calculated from molecular dynamics simulations
involving 40,000 to 100,000 nucleons. The static structure factor describes
coherent neutrino scattering which is expected to dominate the neutrino
opacity. At low momentum transfers the static structure factor is found to be
small because of ion screening. In contrast, at intermediate momentum transfers
the static structure factor displays a large peak due to coherent scattering
from all the neutrons in a cluster. This peak moves to higher momentum
transfers and decreases in amplitude as the density increases. A large static
structure factor at zero momentum transfer, indicative of large density
fluctuations during a first-order phase transition, may increase the neutrino
opacity. However, no evidence of such an increase has been found. Therefore, it
is unlikely that the system undergoes a simple first-order phase transition. It
is found that corrections to the commonly used single heavy nucleus
approximation first appear at a density of the order of g/cm and
increase rapidly with increasing density. Thus, neutrino opacities are
overestimated in the single heavy nucleus approximation relative to the
complete molecular dynamics simulations.Comment: 17 pages, 23 included ps figure
Magnetization Process of Kagome-Lattice Heisenberg Antiferromagnet
The magnetization process of the isotropic Heisenberg antiferromagnet on the
kagome lattice is studied. Data obtained from the numerical-diagonalization
method are reexamined from the viewpoint of the derivative of the magnetization
with respect to the magnetic field. We find that the behavior of the derivative
at approximately one-third of the height of the magnetization saturation is
markedly different from that for the cases of typical magnetization plateaux.
The magnetization process of the kagome-lattice antiferromagnet reveals a new
phenomenon, which we call the "magnetization ramp".Comment: 4 pages, 5figures, accepted in J. Phys. Soc. Jpn
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Tunable Nanometer Electrode Gaps by MeV Ion Irradiation
We report the use of MeV ion-irradiation-induced plastic deformation of amorphous materials to fabricate electrodes with nanometer-sized gaps. Plastic deformation of the amorphous metal is induced by ion irradiation, allowing the complete closing of a sub-micrometer gap. We measure the evolving gap size in situ by monitoring the field emission current-voltage (I-V) characteristics between electrodes. The I-V behavior is consistent with Fowler-Nordheim tunneling. We show that using feedback control on this signal permits gap size fabrication with atomic-scale precision. We expect this approach to nanogap fabrication will enable the practical realization of single molecule controlled devices and sensors.Engineering and Applied SciencesPhysic
Universal emergence of the one-third plateau in the magnetization process of frustrated quantum spin chains
We present a numerical study of the magnetization process of frustrated
quantum spin-S chains with S=1, 3/2, 2 as well as the classical limit. Using
the exact diagonalization and density-matrix renormalization techniques, we
provide evidence that a plateau at one third of the saturation magnetization
exists in the magnetization curve of frustrated spin-S chains with S>1/2.
Similar to the case of S=1/2, this plateau state breaks the translational
symmetry of the Hamiltonian and realizes an up-up-down pattern in the spin
component parallel to the external field. Our study further shows that this
plateau exists both in the cases of an isotropic exchange and in the easy-axis
regime for spin-S=1, 3/2, and 2, but is absent in classical frustrated spin
chains with isotropic interactions. We discuss the magnetic phase diagram of
frustrated spin-1 and spin-3/2 chains as well as other emergent features of the
magnetization process such as kink singularities, jumps, and even-odd effects.
A quantitative comparison of the one-third plateau in the easy-axis regime
between spin-1 and spin-3/2 chains on the one hand and the classical frustrated
chain on the other hand indicates that the critical frustration and the phase
boundaries of this state rapidly approach the classical result as the spin S
increases.Comment: 15 pages RevTex4, 13 figure
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