5,788 research outputs found
Recommended from our members
Early tumor response to intraarterial or intravenous administration of carboplatin to treat naturally occurring lower urinary tract carcinoma in dogs.
BackgroundSurvival times and tumor responses associated with malignant neoplasia of the lower urinary tract are poor despite the vast array of current treatments. Therefore, the evaluation of alternative treatments, such as intraarterial administration of chemotherapy (IAC) should be considered.ObjectiveTo describe a technique for superselective catheterization for IAC and to evaluate initial tumor response by ultrasonography after both IAC and intravenous administration of chemotherapy (IVC).AnimalsClient-owned dogs with lower urinary tract neoplasia treated with either IVC (n = 15) or IAC (n = 11).MethodsRetrospective study. An arterial approach via the carotid or femoral artery was utilized to obtain superselective access and administer chemotherapy in the IAC cases. Medical record review was performed, data were recorded, and recorded variables were evaluated statistically.ResultsIntraarterial chemotherapy was successfully administered in all cases. There was a significantly greater decrease in longest unidimensional measurement in the IAC group as compared to the IVC group (P = .013). The IAC group was also significantly more likely to have a tumor response as assessed by modified RECIST guidelines (P = .049). Dogs in the IAC group were significantly less likely to develop anemia (P = .001), lethargy (P = .010) and anorexia (P = .024).Conclusion and clinical importanceThis study demonstrated the feasibility and efficacy of performing IAC for lower urinary tract neoplasia. Further investigation is necessary as the follow-up time was short and the impact on long-term outcome and survival was not determined
On the anomalous thermal conductivity of one-dimensional lattices
The divergence of the thermal conductivity in the thermodynamic limit is
thoroughly investigated. The divergence law is consistently determined with two
different numerical approaches based on equilibrium and non-equilibrium
simulations. A possible explanation in the framework of linear-response theory
is also presented, which traces back the physical origin of this anomaly to the
slow diffusion of the energy of long-wavelength Fourier modes. Finally, the
results of dynamical simulations are compared with the predictions of
mode-coupling theory.Comment: 5 pages, 3 figures, to appear in Europhysics Letter
Cusps on cosmic superstrings with junctions
The existence of cusps on non-periodic strings ending on D-branes is
demonstrated and the conditions, for which such cusps are generic, are derived.
The dynamics of F-, D-string and FD-string junctions are investigated. It is
shown that pairs of FD-string junctions, such as would form after
intercommutations of F- and D-strings, generically contain cusps. This new
feature of cosmic superstrings opens up the possibility of extra channels of
energy loss from a string network. The phenomenology of cusps on such cosmic
superstring networks is compared to that of cusps formed on networks of their
field theory analogues, the standard cosmic strings.Comment: 22 pages, 5 figure
Screening of classical Casimir forces by electrolytes in semi-infinite geometries
We study the electrostatic Casimir effect and related phenomena in
equilibrium statistical mechanics of classical (non-quantum) charged fluids.
The prototype model consists of two identical dielectric slabs in empty space
(the pure Casimir effect) or in the presence of an electrolyte between the
slabs. In the latter case, it is generally believed that the long-ranged
Casimir force due to thermal fluctuations in the slabs is screened by the
electrolyte into some residual short-ranged force. The screening mechanism is
based on a "separation hypothesis": thermal fluctuations of the electrostatic
field in the slabs can be treated separately from the pure image effects of the
"inert" slabs on the electrolyte particles. In this paper, by using a
phenomenological approach under certain conditions, the separation hypothesis
is shown to be valid. The phenomenology is tested on a microscopic model in
which the conducting slabs and the electrolyte are modelled by the symmetric
Coulomb gases of point-like charges with different particle fugacities. The
model is solved in the high-temperature Debye-H\"uckel limit (in two and three
dimensions) and at the free fermion point of the Thirring representation of the
two-dimensional Coulomb gas. The Debye-H\"uckel theory of a Coulomb gas between
dielectric walls is also solved.Comment: 25 pages, 2 figure
van der Waals coupling in atomically doped carbon nanotubes
We have investigated atom-nanotube van der Waals (vdW) coupling in atomically
doped carbon nanotubes (CNs). Our approach is based on the perturbation theory
for degenerated atomic levels, thus accounting for both weak and strong
atom-vacuum-field coupling. The vdW energy is described by an integral equation
represented in terms of the local photonic density of states (DOS). By solving
it numerically, we demonstrate the inapplicability of standard
weak-coupling-based vdW interaction models in a close vicinity of the CN
surface where the local photonic DOS effectively increases, giving rise to an
atom-field coupling enhancement. An inside encapsulation of atoms into the CN
has been shown to be energetically more favorable than their outside adsorption
by the CN surface. If the atom is fixed outside the CN, the modulus of the vdW
energy increases with the CN radius provided that the weak atom-field coupling
regime is realized (i.e., far enough from the CN). For inside atomic position,
the modulus of the vdW energy decreases with the CN radius, representing a
general effect of the effective interaction area reduction with lowering the CN
curvature.Comment: 15 pages, 5 figure
Nanoscale Smoothing and the Analysis of Interfacial Charge and Dipolar Densities
The interface properties of interest in multilayers include interfacial
charge densities, dipole densities, band offsets, and screening-lengths, among
others. Most such properties are inaccesible to direct measurements, but are
key to understanding the physics of the multilayers. They are contained within
first-principles electronic structure computations but are buried within the
vast amount of quantitative information those computations generate. Thus far,
they have been extracted from the numerical data by heuristic nanosmoothing
procedures which do not necessarily provide results independent of the
smoothing process. In the present paper we develop the theory of nanosmoothing,
establishing procedures for both unpolarized and polarized systems which yield
interfacial charge and dipole densities and band offsets invariant to the
details of the smoothing procedures when the criteria we have established are
met. We show also that dipolar charge densities, i. e. the densities of charge
transferred across the interface, and screening lengths are not invariant. We
illustrate our procedure with a toy model in which real, transversely averaged
charge densities are replaced by sums of Gaussians.Comment: 30 pages, 15 figures, 4 table
Spontaneous decay dynamics in atomically doped carbon nanotubes
We report a strictly non-exponential spontaneous decay dynamics of an excited
two-level atom placed inside or at different distances outside a carbon
nanotube (CN). This is the result of strong non-Markovian memory effects
arising from the rapid variation of the photonic density of states with
frequency near the CN. The system exhibits vacuum-field Rabi oscillations, a
principal signature of strong atom-vacuum-field coupling, when the atom is
close enough to the nanotube surface and the atomic transition frequency is in
the vicinity of the resonance of the photonic density of states. Caused by
decreasing the atom-field coupling strength, the non-exponential decay dynamics
gives place to the exponential one if the atom moves away from the CN surface.
Thus, atom-field coupling and the character of the spontaneous decay dynamics,
respectively, may be controlled by changing the distance between the atom and
CN surface by means of a proper preparation of atomically doped CNs. This opens
routes for new challenging nanophotonics applications of atomically doped CN
systems as various sources of coherent light emitted by dopant atoms.Comment: 10 pages, 4 figure
The environment of the fast rotating star Achernar - Thermal infrared interferometry with VLTI/MIDI and SIMECA modeling
Context: As is the case of several other Be stars, Achernar is surrounded by
an envelope, recently detected by near-IR interferometry.
Aims: We search for the signature of circumstellar emission at distances of a
few stellar radii from Achernar, in the thermal IR domain.
Methods: We obtained interferometric observations on three VLTI baselines in
the N band (8-13 mic), using the MIDI instrument.
Results: From the measured visibilities, we derive the angular extension and
flux contribution of the N band circumstellar emission in the polar direction
of Achernar. The interferometrically resolved polar envelope contributes 13.4
+/- 2.5 % of the photospheric flux in the N band, with a full width at half
maximum of 9.9 +/- 2.3 mas (~ 6 Rstar). This flux contribution is in good
agreement with the photometric IR excess of 10-20% measured by fitting the
spectral energy distribution. Due to our limited azimuth coverage, we can only
establish an upper limit of 5-10% for the equatorial envelope. We compare the
observed properties of the envelope with an existing model of this star
computed with the SIMECA code.
Conclusions: The observed extended emission in the thermal IR along the polar
direction of Achernar is well reproduced by the existing SIMECA model. Already
detected at 2.2mic, this polar envelope is most probably an observational
signature of the fast wind ejected by the hot polar caps of the star.Comment: A&A Letter, in pres
Cosmic D-Strings and Vortons in Supergravity
Recent developments in string inspired models of inflation suggest that
D-strings are formed at the end of inflation. Within the supergravity model of
D-strings there are 2(n-1) chiral fermion zero modes for a D-string of winding
n. Using the bounds on the relic vorton density, we show that D-strings with
winding number n>1 are more strongly constrained than cosmic strings arising in
cosmological phase transitions. The D-string tension of such vortons, if they
survive until the present, has to satisfy 8\pi G_N \mu \lesssim p 10^{-26}
where p is the intercommutation probability. Similarly, D-strings coupled with
spectator fermions carry currents and also need to respect the above bound.
D-strings with n=1 do not carry currents and evade the bound. We discuss the
coupling of D-strings to supersymmetry breaking. When a single U(1) gauge group
is present, we show that there is an incompatibility between spontaneous
supersymmetry breaking and cosmic D-strings. We propose an alternative
mechanism for supersymmetry breaking, which includes an additional U(1), and
might alleviate the problem. We conjecture what effect this would have on the
fermion zero modes.Comment: 11 page
-dimensions Dirac fermions BEC-BCS cross-over thermodynamics
An effective Proca Lagrangian action is used to address the vector
condensation Lorentz violation effects on the equation of state of the strongly
interacting fermions system. The interior quantum fluctuation effects are
incorporated as an external field approximation indirectly through a fictive
generalized Thomson Problem counterterm background. The general analytical
formulas for the -dimensions thermodynamics are given near the unitary limit
region. In the non-relativistic limit for , the universal dimensionless
coefficient and energy gap are
reasonably consistent with the existed theoretical and experimental results. In
the unitary limit for and T=0, the universal coefficient can even
approach the extreme occasion corresponding to the infinite effective
fermion mass which can be mapped to the strongly coupled
two-dimensions electrons and is quite similar to the three-dimensions
Bose-Einstein Condensation of ideal boson gas. Instead, for , the
universal coefficient is negative, implying the non-existence of phase
transition from superfluidity to normal state. The solutions manifest the
quantum Ising universal class characteristic of the strongly coupled unitary
fermions gas.Comment: Improved versio
- …