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Biomedical subjects

J M Vilar

Publications and source records attributed to J M Vilar.

8 recordsLinked to original sources

Thermodynamics "beyond" local equilibrium.

Nonequilibrium thermodynamics has shown its applicability in a wide variety of different situations pertaining to fields such as physics, chemistry, biology, and engineering. As successful as it is, however, its current formulation considers only systems close to equilibrium, those satisfying the so-called local equilibrium hypothesis. Here we show that diffusion processes that occur far away from equilibrium can be viewed as at local equilibrium in a space that includes all the relevant variables in addition to the spatial coordinate. In this way, nonequilibrium thermodynamics can be used and the difficulties and ambiguities associated with the lack of a thermodynamic description disappear. We analyze explicitly the inertial effects in diffusion and outline how the main ideas can be applied to other situations.

Biology↗

Magnetic resonance imaging of two normal equine brains and their associated structures.

Magnetic resonance images were obtained from two isolated horses' heads. Ten mm thick, T1-weighted images were taken with a 1.5 Tesla magnet and a body coil, and compared with the corresponding frozen cross-sections of the heads, relevant structures being identified and labelled at each level. The images should provide reference material for clinical magnetic imaging studies of horses' heads.

Animals↗

Noise suppression by noise.

We have analyzed the interplay between an externally added noise and the intrinsic noise of systems that relax fast towards a stationary state, and found that increasing the intensity of the external noise can reduce the total noise of the system. We have established a general criterion for the appearance of this phenomenon and discussed two examples in detail.

Models, Theoretical↗

Computed tomography of normal cranioencephalic structures in two horses.

The purpose of this investigation was to define the anatomy of the cranioencephalic structures in horses using computed tomography (CT). Transverse images of two isolated equine cadaver heads were obtained using a Toshiba 600 HQ (third-generation equipment TCT). CT images were compared to corresponding frozen cross-sections of the cadaver head. Relevant anatomical structures were identified and labelled at each level. The resulting images provided excellent anatomic detail of the structures of the central nervous system and associated formations. Annotated CT images from this study are intended as a reference for clinical CT imaging studies of the equine head.

Animals↗

Noise and periodic modulations in neural excitable media.

We have analyzed the interplay between noise and periodic modulations in a mean field model of a neural excitable medium. For this purpose, we have considered two types of modulations, namely, variations of the resistance and oscillations of the threshold. In both cases, stochastic resonance is present, irrespective of whether the system is monostable or bistable.

Biophysical Phenomena↗

Magnetic resonance imaging of the normal equine brain.

The purpose of this investigation was to define the magnetic resonance (MR) imaging appearance of the brain and associated structures of the equine head. MR images were acquired in oblique dorsal (T2-weighted), sagittal (T1-weighted), and transverse planes (T2-weighted), using a magnet of 1.5 Tesla and a human body coil. Relevant anatomic structures were identified and labeled at each level. The resulting images provided excellent anatomic detail of the cranioencephalic structures. Annotated MR images from this study are intended as a reference for clinical imaging studies of the equine head, specially in the diagnosis of brain diseases in the horse.

Animals↗