1,045 research outputs found
Poynting Vector Flow in a Circular Circuit
A circuit is considered in the shape of a ring, with a battery of negligible
size and a wire of uniform resistance. A linear charge distribution along the
wire maintains an electrostatic field and a steady current, which produces a
constant magnetic field. Earlier studies of the Poynting vector and the rate of
flow of energy considered only idealized geometries in which the Poynting
vector was confined to the space within the circuit. But in more realistic
cases the Poynting vector is nonzero outside as well as inside the circuit. An
expression is obtained for the Poynting vector in terms of products of
integrals, which are evaluated numerically to show the energy flow. Limiting
expressions are obtained analytically. It is shown that the total power
generated by the battery equals the energy flowing into the wire per unit time.Comment: 19 pages, 8 figure
Bulk viscosity of strange quark matter: Urca versus non-leptonic processes
A general formalism for calculating the bulk viscosity of strange quark
matter is developed. Contrary to the common belief that the non-leptonic
processes alone give the dominant contribution to the bulk viscosity, the
inclusion of the Urca processes is shown to play an important role at
intermediate densities when the characteristic r-mode oscillation frequencies
are not too high. The interplay of non-leptonic and Urca processes is analyzed
in detailComment: 9 pages, 4 figures, v2: revised figures, no change in result
Transcatheter closure of muscular ventricular septal defects with the amplatzer ventricular septal defect occluder: initial clinical applications in children11The Amplatzer VSD occluders were provided by AGA, Medical Corporation, Golden Valley, Minnesota. There were no sources of financial support.
AbstractOBJECTIVESThe aim of this study was to close muscular ventricular septal defects (MVSDs) in children, with a new device, the Amplatzer ventricular septal defect occluder (AVSDO).BACKGROUNDThe design of previously used devices for transcatheter closure of MVSDs is not ideal for this purpose and their use has been limited by several drawbacks.METHODSSix patients, aged 3 to 10 years, with MVSDs underwent transcatheter closure using the AVSDO. The device is a modified self-centering and repositionable Amplatzer device that consists of two low profile disks made of Nitinol wire mesh with a 7-mm connecting waist. The prosthesis size (connecting waist diameter) was chosen according to the measured balloon stretched VSD diameters. A 6-F or 7-F sheath was used for the delivery of the AVSDO. Fluoroscopy and transesophageal echocardiography were utilized for optimal guidance.RESULTSThe location of the defect was midmuscular in five patients and beneath the pulmonary valve in one. The balloon stretched MVSD diameter ranged from 6 to 11 mm. Device placement was successful in all patients, and complete occlusion occurred in all six patients (95% confidence interval 54.06% to 100%). Two patients developed transient complete left bundle branch block. No other complications were observed.CONCLUSIONSThis encouraging initial clinical success indicates that the AVSDO is a promising device for transcatheter closure of MVSDs in children. Further clinical trials and longer follow-up are needed before the widespread use of this technique can be recommended
Bulk viscosity of spin-one color superconductors with two quark falvors
We consider the contribution of the Urca-type processes to the bulk viscosity
of several spin-one color-superconducting phases of dense two-flavor quark
matter. In the so-called transverse phases which are suggested to be
energetically favorable at asymptotic densities, the presence of ungapped
quasiparticle modes prevents that spin-one color superconductivity has a large
effect on the bulk viscosity. When all modes are gapped, as for one particular
color-spin-locked phase, the effect on the viscosity can be quite large, which
may have important phenomenological implications.Comment: 10 pages, 6 figures, Discussion is extended and several references
added. Version accepted for publication in Phys. Rev.
Ferroelectricity and ferromagnetism in EuTiO3 nanowires
We predicted the ferroelectric-ferromagnetic multiferroic properties of
EuTiO3 nanowires and generated the phase diagrams in coordinates of temperature
and wire radii. The calculations were performed within the
Landau-Ginzburg-Devonshire theory with phenomenological parameters extracted
from tabulated experimental data and first principles calculations. Since bulk
EuTiO3 is antiferromagnetic at temperatures lower than 5.5 K and paraelectric
at all temperatures, our goal was to investigate the possibility of inducing
the ferroelectric and ferromagnetic properties of EuTiO3 by reducing the bulk
to nanosystems. Our results indicate that ferroelectric spontaneous
polarization of ~0.1-0.5C/m2 is induced in EuTiO3 nanowires due to the
intrinsic surface stress, which is inversely proportional to the nanowire
radius. The spontaneous polarization exists at temperatures lower than 300 K,
for the wire radius less than 1 nm and typical surface stress coefficients ~ 15
N/m. Due to the strong biquadratic magnetoelectric coupling, the spontaneous
polarization in turn induces the ferromagnetic phase at temperatures lower than
30 K for 2 nm nanowire, and at temperatures lower than 10 K for 4 nm nanowire
in EuTiO3. Thus we predicted that the EuTiO3 nanowires can be the new
ferroelectric-ferromagnetic multiferroic.Comment: 22 pages, 5 figures, 1 tabl
Modeling tumor cell migration: from microscopic to macroscopic
It has been shown experimentally that contact interactions may influence the
migration of cancer cells. Previous works have modelized this thanks to
stochastic, discrete models (cellular automata) at the cell level. However, for
the study of the growth of real-size tumors with several millions of cells, it
is best to use a macroscopic model having the form of a partial differential
equation (PDE) for the density of cells. The difficulty is to predict the
effect, at the macroscopic scale, of contact interactions that take place at
the microscopic scale. To address this we use a multiscale approach: starting
from a very simple, yet experimentally validated, microscopic model of
migration with contact interactions, we derive a macroscopic model. We show
that a diffusion equation arises, as is often postulated in the field of glioma
modeling, but it is nonlinear because of the interactions. We give the explicit
dependence of diffusivity on the cell density and on a parameter governing
cell-cell interactions. We discuss in details the conditions of validity of the
approximations used in the derivation and we compare analytic results from our
PDE to numerical simulations and to some in vitro experiments. We notice that
the family of microscopic models we started from includes as special cases some
kinetically constrained models that were introduced for the study of the
physics of glasses, supercooled liquids and jamming systems.Comment: Final published version; 14 pages, 7 figure
Explorations in anatomy: the remains from Royal London Hospital
This paper considers the faunal remains from recent excavations at the Royal London Hospital. The remains date to the beginning of the 19th century and offer an insight into the life of the hospital's patients and practices of the attached medical school. Many of the animal remains consist of partially dissected skeletons, including the unique finds of Hermann's tortoise (Testudo hermanni) and Cercopithecus monkey. The hospital diet and developments in comparative anatomy are discussed by integrating the results with documentary research. They show that zooarchaeological study of later post-medieval material can significantly enhance our understanding of the exploitation of animals in this perio
Characterization of multiple insecticide resistance in Anopheles gambiae (Diptera: Culicidae) from Pointe Noire, Republic of the Congo
Limited Value of Bladder Wash Cytology During Follow-Up of Patients With Non-muscle Invasive Bladder Cancer
Aims We aimed to assess the performance of bladder wash cytology (BWC) in daily clinical practice in a pure follow-up cohort of patients previously diagnosed with non-muscle invasive bladder cancer (NMIBC). Materials and methods We analyzed 2064 BWCs derived from 314 patients followed for NMIBC (2003-2016). Follow-up investigations were performed using cystoscopy (CS) in combination with BWC. Patients with suspicious CS and/or positive BWC underwent bladder biopsy or transurethral resection. BWC was considered positive if malignant or suspicious cells were reported. Sensitivity (Sn) and specificity (Sp) were calculated for the entire cohort and separately for low-grade (LG) and high-grade (HG) tumors, and carcinoma in situ (CIS) subgroups. Results A total of 95 recurrences were detected, of which only three were detected by BWC alone. Overall, Sn and Sp of BWC were 17.9% and 99.5%, respectively. For LG disease, these numbers were 14.0% and 100%, and for HG disease, these were 22.2% and 99.1%, respectively. For patients with CIS at initial diagnosis, Sn and Sp were 11.0% and 71.4%, respectively. For isolated primary CIS, Sn was 50.0%, and Sp was 98.2%. Conclusion Routine use of BWC in the follow-up for NMIBC is of limited value even in HG tumors. In the presence of isolated primary CIS, adjunct BWC might be justified
Thinking outside the ocean-climate nexus : Towards systems-informed decision making in a rapidly changing world
Despite repeated calls for more inclusive practices, approaches used to address current challenges within the ocean-climate nexus do not sufficiently account for the complexity of the human-social-ecological system. So far, this has prevented efficient and just decision-making and policies. We propose to shift towards systems-informed decision making, which values transdisciplinary system-thinking and cumulative impact assessments, and encourages multi-system collaboration among decision-makers in order to address the recurring technicality of policies and to foster just solutions that account for the needs of varied actors across the sustainable development spectrum
- …