168 research outputs found
Modeling Focused Ultrasound Exposure for the Optimal Control of Thermal Dose Distribution
Preclinical studies indicate that focused ultrasound at exposure conditions close to the threshold for thermal damage can increase drug delivery at the focal region. Although these results are promising, the optimal control of temperature still remains a challenge. To address this issue, computer-simulated ultrasound treatments have been performed. When the treatments are delivered without taking into account the cooling effect exerted by the blood flow, the resulting thermal dose is highly variable with regions of thermal damage, regions of underdosage close to the vessels, and areas in between these two extremes. When the power deposition is adjusted so that the peak thermal dose remains close to the threshold for thermal damage, the thermal dose is more uniformly distributed but under-dosage is still visible around the thermally significant vessels. The results of these simulations suggest that, for focused ultrasound, as for other delivery methods, the only way to control temperature is to adjust the average energy deposition to compensate for the presence of thermally significant vessels in the target area. By doing this, we have shown that it is possible to reduce the temperature heterogeneity observed in focused ultrasound thermal treatments
Presencia de dos especies de garrapatas (Acari: Ixodidae) con importancia médica en la ciudad de Buenos Aires
SINFil: Cicuttin, Gabriel L.. Provincia de Buenos Aires. Ministerio de Salud. Instituto de Zoonosis Luis Pasteur; Argentina;Fil: Sassaroli, Juan C.. Provincia de Buenos Aires. Ministerio de Salud. Instituto de Zoonosis Luis Pasteur; Argentina;Fil: Ardiles, MarĂa I.. Provincia de Buenos Aires. Ministerio de Salud. Instituto de Zoonosis Luis Pasteur; Argentina;Fil: Zotter, Ana C.. Provincia de Buenos Aires. Ministerio de Salud. Instituto de Zoonosis Luis Pasteur; Argentina;Fil: Guglielmone, Alberto Alejandro. Instituto Nacional de TecnologĂa Agropecuaria. Centro Reguional CĂłrdoba. EstaciĂłn Experimental Regional Agropecuaria Rafaela; Argentina; Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; Argentina;Fil: Nava, Santiago. Instituto Nacional de TecnologĂa Agropecuaria. Centro Regional Santa Fe. EstaciĂłn Experimental Agropecuaria, Rafaela; Argentina; Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; Argentina
Desire thinking as a predictor of drinking status following treatment for alcohol use disorder: A prospective study
© 2019 Elsevier Ltd Research has indicated that craving is one of the strongest predictors of treatment outcome and relapse in Alcohol Use Disorders (AUD) but there is little consensus on the factors that may influence its activation and escalation. Research has also shown that desire thinking is an important cognitive process which may exacerbate craving in problem drinkers. The aim of present study was to explore, for the first time, the role of desire thinking in prospectively predicting relapse, craving and binge drinking in patients receiving treatment for AUD. One hundred and thirty-five patients admitted to two rehabilitation centres and two outpatient services for addiction and mental health problems were administered baseline, treatment completion and three months follow-up measures of anxiety and depression, AUD severity, binge drinking frequency, craving and desire thinking. Results indicated that the verbal perseveration component of desire thinking at treatment completion was the only significant predictor of relapse at follow-up over and above baseline AUD severity and binge drinking frequency. Furthermore, the imaginal prefiguration component of desire thinking and craving levels at treatment completion were found to predict craving levels at follow-up independently of AUD severity and binge drinking frequency at baseline. Finally, both the imaginal prefiguration and verbal perseveration components of desire thinking at treatment completion were found to be the only predictors of binge drinking frequency at follow-up independently of AUD severity and binge drinking frequency at baseline. Treatments for AUD should aim to reduce desire thinking in people to enhance clinical outcomes and reduce relapse risk
Production of photons by the parametric resonance in the dynamical Casimir effect
We calculate the number of photons produced by the parametric resonance in a
cavity with vibrating walls. We consider the case that the frequency of
vibrating wall is which is a generalization of other
works considering only , where is the fundamental-mode
frequency of the electromagnetic field in the cavity. For the calculation of
time-evolution of quantum fields, we introduce a new method which is borrowed
from the time-dependent perturbation theory of the usual quantum mechanics.
This perturbation method makes it possible to calculate the photon number for
any and to observe clearly the effect of the parametric resonance.Comment: 15 pages, RevTeX, no figure
Radiative Phase Transitions and Casmir Effect Instabilities
Molecular quantum electrodynamics leads to photon frequency shifts and thus
to changes in condensed matter free energies often called the Casimir effect.
Strong quantum electrodynamic coupling between radiation and molecular motions
can lead to an instability beyond which one or more photon oscillators undergo
a displacement phase transition. The phase boundary of the transition can be
located by a Casimir free energy instability.Comment: ReVTeX4 format 1 *.eps figur
Interference phenomena in the photon production between two oscillating walls
We study the photon production in a 1D cavity whose left and right walls
oscillate with the frequency and , respectively. For
the number of generated photons by the
parametric resonance is the sum of the photon numbers produced when the left
and the right wall oscillates separately. But for ,
the interference term proportional to is found additionally, where
is the phase difference between two oscillations of the walls.Comment: 7 pages, RevTeX, no figures, a sign error correcte
Observability of the Bulk Casimir Effect: Can the Dynamical Casimir Effect be Relevant to Sonoluminescence?
The experimental observation of intense light emission by acoustically
driven, periodically collapsing bubbles of air in water (sonoluminescence) has
yet to receive an adequate explanation. One of the most intriguing ideas is
that the conversion of acoustic energy into photons occurs quantum
mechanically, through a dynamical version of the Casimir effect. We have argued
elsewhere that in the adiabatic approximation, which should be reliable here,
Casimir or zero-point energies cannot possibly be large enough to be relevant.
(About 10 MeV of energy is released per collapse.) However, there are
sufficient subtleties involved that others have come to opposite conclusions.
In particular, it has been suggested that bulk energy, that is, simply the
naive sum of , which is proportional to the volume, could
be relevant. We show that this cannot be the case, based on general principles
as well as specific calculations. In the process we further illuminate some of
the divergence difficulties that plague Casimir calculations, with an example
relevant to the bag model of hadrons.Comment: 13 pages, REVTe
Casimir Energy for a Spherical Cavity in a Dielectric: Applications to Sonoluminescence
In the final few years of his life, Julian Schwinger proposed that the
``dynamical Casimir effect'' might provide the driving force behind the
puzzling phenomenon of sonoluminescence. Motivated by that exciting suggestion,
we have computed the static Casimir energy of a spherical cavity in an
otherwise uniform material. As expected the result is divergent; yet a
plausible finite answer is extracted, in the leading uniform asymptotic
approximation. This result agrees with that found using zeta-function
regularization. Numerically, we find far too small an energy to account for the
large burst of photons seen in sonoluminescence. If the divergent result is
retained, it is of the wrong sign to drive the effect. Dispersion does not
resolve this contradiction. In the static approximation, the Fresnel drag term
is zero; on the mother hand, electrostriction could be comparable to the
Casimir term. It is argued that this adiabatic approximation to the dynamical
Casimir effect should be quite accurate.Comment: 23 pages, no figures, REVTe
Trembling cavities in the canonical approach
We present a canonical formalism facilitating investigations of the dynamical
Casimir effect by means of a response theory approach. We consider a massless
scalar field confined inside of an arbitaray domain , which undergoes
small displacements for a certain period of time. Under rather general
conditions a formula for the number of created particles per mode is derived.
The pertubative approach reveals the occurance of two generic processes
contributing to the particle production: the squeezing of the vacuum by
changing the shape and an acceleration effect due to motion af the boundaries.
The method is applied to the configuration of moving mirror(s). Some properties
as well as the relation to local Green function methods are discussed.
PACS-numbers: 12.20; 42.50; 03.70.+k; 42.65.Vh Keywords: Dynamical Casimir
effect; Moving mirrors; Cavity quantum field theory; Vibrating boundary
Theory of quantum radiation observed as sonoluminescence
Sonoluminescence is explained in terms of quantum radiation by moving
interfaces between media of different polarizability. In a stationary
dielectric the zero-point fluctuations of the electromagnetic field excite
virtual two-photon states which become real under perturbation due to motion of
the dielectric. The sonoluminescent bubble is modelled as an optically empty
cavity in a homogeneous dielectric. The problem of the photon emission by a
cavity of time-dependent radius is handled in a Hamiltonian formalism which is
dealt with perturbatively up to first order in the velocity of the bubble
surface over the speed of light. A parameter-dependence of the zero-order
Hamiltonian in addition to the first-order perturbation calls for a new
perturbative method combining standard perturbation theory with an adiabatic
approximation. In this way the transition amplitude from the vacuum into a
two-photon state is obtained, and expressions for the single-photon spectrum
and the total energy radiated during one flash are given both in full and in
the short-wavelengths approximation when the bubble is larger than the
wavelengths of the emitted light. It is shown analytically that the spectral
density has the same frequency-dependence as black-body radiation; this is
purely an effect of correlated quantum fluctuations at zero temperature. The
present theory clarifies a number of hitherto unsolved problems and suggests
explanations for several more. Possible experiments that discriminate this from
other theories of sonoluminescence are proposed.Comment: Latex file, 28 pages, postscript file with 3 figs. attache
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