Disruption of the behavioral satiety sequence by simmondsin.

Simmondsin, a cyanoglycoside from jojoba meal, reduces food intake after oral administration. To diagnose if it acts by inducing satiation or by creating abnormal physiological effects, an observational study was undertaken to investigate the effects of simmondsin on feeding and other behaviors. Particular attention was paid to the behavioral sequence associated with satiety (BSS). At first contact, simmondsin non-significantly reduced food intake by 17% and had little effect on feeding and associated behaviors. The behavioral structure was preserved and a small shift of the onset of resting to the left was observed, suggesting a small satiative action of simmondsin at first contact. Simmondsin given for the second time caused a more pronounced food intake reduction of 52% due to a reduction in eating duration, mean bout intake and mean bout length, and to an increase in latency to eat. At second contact, simmondsin caused a strong switching in active behaviors, disrupting the BSS. The simmondsin-induced hyperactivity suggests that simmondsin produces aversiveness with second contact. Our results indicate that simmondsin exerts multiple effects. It probably facilitates a small natural process of satiation/satiety at first contact, but creates abnormal physiological effects resulting in aversive reactions from second contact on.

The history and properties of ultrasonic inhomogeneous waves.

This paper gives a historical survey of the development of the inhomogeneous wave theory, and its applications, in the field of ultrasonics. The references are listed predominantly chronologically and are as good as complete. Along the historical description, several scientific features of inhomogeneous waves are described. All topics of inhomogeneous wave research are taken into account, such as waves in viscoelastic solids and liquids, thermoviscous liquids and solids, and anisotropic viscoelastic materials. Also inhomogeneous waves having complex frequency are described. Furthermore, the formation of bounded beams by means of inhomogeneous waves is given and the diffraction of inhomogeneous waves on periodically corrugated surfaces. The experimental generation of inhomogeneous waves is considered as well.

The radiation mode theory in ultrasonics.

This paper describes the history and the state of the art in radiation mode theory (RMT) in ultrasonics. The RMT originates from electromagnetism in which it has proved to be very efficient in the field of wave guides and discontinuities. In ultrasonics, the RMT made its entrance only a decade ago and has already proved to be very efficient in describing the interaction of sound with discontinuities such as a step on a plate, a liquid wedge, the extremity of a plate and much more. It is likely that the development of the RMT for two-dimensional (2-D) isotropic media has come almost to an end. This paper lists the results obtained so far. Further extensions to more complicated media are to be expected in the coming decade.

Diffraction of homogeneous and inhomogeneous plane waves on a doubly corrugated liquid/solid interface.

This paper extends the theory of the diffraction of sound on 1D corrugated surfaces to 2D corrugated surfaces. Such surfaces, that are egg crate shaped, diffract incoming sound into all polar directions, which is fundamentally different from 1D corrugated surfaces. A theoretical justification is given for extending the classical grating equation to the case of incident inhomogeneous waves, for 1D corrugated surfaces as well as for 2D corrugated surfaces. Even though the present paper presents a theory which is valid for all angles of incidence, special attention is given to the particular case of the stimulation of surface waves by normal incident sound. The most interesting conclusion is that, depending on the frequency and the incident inhomogeneity, Scholte-Stoneley waves and leaky Rayleigh waves can be generated in different directions. This effect might be of particular interest in the development of surface acoustic wave devices and the basic idea of this steering effect can be of importance for planar actuators.

A theoretical study of special acoustic effects caused by the staircase of the El Castillo pyramid at the Maya ruins of Chichen-Itza in Mexico.

It is known that a handclap in front of the stairs of the great pyramid of Chichen Itza produces a chirp echo which sounds more or less like the sound of a Quetzal bird. The present work describes precise diffraction simulations and attempts to answer the critical question what physical effects cause the formation of the chirp echo. Comparison is made with experimental results obtained from David Lubman. Numerical simulations show that the echo shows a strong dependence on the kind of incident sound. Simulations are performed for a (delta function like) pulse and also for a real handclap. The effect of reflections on the ground in front of the pyramid is also discussed. The present work also explains why an observer seated on the lowest step of the pyramid hears the sound of raindrops falling in a water filled bucket instead of footstep sounds when people, situated higher up the pyramid, climb the stairs.

Diffraction of horizontally polarized ultrasonic plane waves on a periodically corrugated solid-liquid interface for normal incidence and Brewster angle incidence.

The theory, and the use at normal incidence, of shear-vertically polarized waves (with polarization vector in the plane containing the incident wave vector and the normal on the interface) using the mode conversion method has been tackled by others. Here we develop the theory for shear-horizontally polarized incident waves (with polarization vector perpendicular to both the normal on the interface and the incoming wave vector). We take into account normal incidence as well as oblique incidence. For normal incidence, we discover the generation of Love waves. If oblique incidence is considered, we discover the existence of a Brewster angle of incidence, comparable with the Brewster angle in optics, in which a diffraction grating can be used as a polarization filter.

The use of polarized bounded beams to determine the groove direction of a surface corrugation at normal incidence, the generation of surface waves and the insonification at Bragg-angles.

Zero order reflected sound from a singly corrugated interface between a solid and a liquid, insonified from the solid side by circular polarized shear waves, can become almost perfect linearly polarized in a direction parallel or perpendicular to the corrugations, depending on the frequency, and can therefore reveal the direction of the corrugations. When narrow bounded beams, formed by a summation of infinite plane waves, are diffracted at certain frequencies, depending on the angle of incidence, or vice versa, one can predict phenomena like backscattering at Bragg-angle incidence and also the creation of Scholte-Stoneley waves.