7 research outputs found
Measuring Nonequilibrium Temperature of Forced Oscillators
The meaning of temperature in nonequilibrium thermodynamics is considered by
using a forced harmonic oscillator in a heat bath, where we have two effective
temperatures for the position and the momentum, respectively. We invent a
concrete model of a thermometer to testify the validity of these different
temperatures from the operational point of view. It is found that the measured
temperature depends on a specific form of interaction between the system and a
thermometer, which means the zeroth law of thermodynamics cannot be immediately
extended to nonequilibrium cases.Comment: 8 page
Evaluation of skin absorption of drugs from topical and transdermal formulations
ABSTRACT The skin barrier function has been attributed to the stratum corneum and represents a major challenge in clinical practice pertaining to cutaneous administration of drugs. Despite this, a large number of bioactive compounds have been successfully administered via cutaneous administration because of advances in the design of topical and transdermal formulations. In vitro and in vivo evaluations of these novel drug delivery systems are necessary to characterize their quality and efficacy. This review covers the most well-known methods for assessing the cutaneous absorption of drugs as an auxiliary tool for pharmaceutical formulation scientists in the design of drug delivery systems. In vitro methods as skin permeation assays using Franz-type diffusion cells, cutaneous retention and tape-stripping methods to study the cutaneous penetration of drugs, and in vivo evaluations as pre-clinical pharmacokinetic studies in animal models are discussed. Alternative approaches to cutaneous microdialysis are also covered. Recent advances in research on skin absorption of drugs and the effect of skin absorption enhancers, as investigated using confocal laser scanning microscopy, Raman confocal microscopy, and attenuated total reflectance Fourier-transform infrared spectroscopy, are reviewed
Mimic therapeutic actions against keloid by thermostatted kinetic theory methods
International audienceThis paper deals with the modeling of a wound-healing disease under a therapeutic action by employing the methods of the thermostatted kinetic theory for active particles. In particular, in order to test therapeutic actions against keloid formation and the possible development of a cancer, an external force field coupled to a Gaussian thermostat is introduced into a mathematical model recently proposed. Specifically the model depicts the competition of the immune system cells with a virus, the mutated fibroblast cells, and the cancer cells. Employing a computational analysis, the effects of three different external forces mimic therapeutic actions are analyzed: A vaccine for the virus, the PUVA therapy for the keloid and a vaccine for the cancer. The results are in agreement with the evidence that the sole action of the immune system is not sufficient to obtain a total depletion of keloid thus requiring the definition of a therapy. Further refinements and developments of the model are also discussed in the paper
Diffusion in the Lorentz Gas
The Lorentz gas, a point particle making mirror-like reflections from an
extended collection of scatterers, has been a useful model of deterministic
diffusion and related statistical properties for over a century. This survey
summarises recent results, including periodic and aperiodic models, finite and
infinite horizon, external fields, smooth or polygonal obstacles, and in the
Boltzmann-Grad limit. New results are given for several moving particles and
for obstacles with flat points. Finally, a variety of applications are
presented.Comment: 28 pages, 5 figure
Thermostats for "Slow" Configurational Modes
Thermostats are dynamical equations used to model thermodynamic variables
such as temperature and pressure in molecular simulations. For computationally
intensive problems such as the simulation of biomolecules, we propose to
average over fast momentum degrees of freedom and construct thermostat
equations in configuration space. The equations of motion are deterministic
analogues of the Smoluchowski dynamics in the method of stochastic differential
equations.Comment: 17 pages, 1 figure, close to publishe