Light echoes from ancient supernova offer a unique and powerful opportunity to study supernovae and their relationships to supernova remnants (SNRs), as well as interstellar dust and Galactic structure. The use of this relatively simple phenomenon of light echoes in such studies is just now developing into an exciting new field of study. This is one of the very rare occasions in astronomy that ...

Stimulated photon echoes (SPEs) with time duration comparable to the coherent lifetime and Rabi period have been investigated theoretically and experimentally with an angled beam configuration. The Rabi oscillation effects on both the transmitted field (optical nutation) and the SPE fields are explained by analytic solutions of Maxwell-Bloch equations. The theory also predicts that an echo can ...

Thirty patients with right ventricular (RV) and 15 with coronary sinus (CS) pacing catheters were studied by M-mode echocardiography. RV catheters, detected in 23, appeared as linear echoes in the right ventricle during mitral valve recordings in 12, adjacent or superimposed on the tricuspid valve (TV) in 14, and immediately anterior to aortic root and pulmonary valve echoes in two with a redun...

Bottlenose dolphins (Tursiops truncatus) have an acute ability to use target echoes to judge attributes such as size, shape, and material composition. Most target recognition studies have focused on features associated with individual echoes as opposed to information conveyed across echo sequences (feature envelope of the multi-echo train). One feature of aspect-dependent targets is an amplitud...

The aspect sensitivity of VHF echoes from field aligned irregularities (FAI) within meteor trails and thin ionization layers is studied using numerical models. Although the maximum power is obtained when a radar is pointed perpendicular to the field line (⊥B), substantial power can be obtained off the⊥B direction if the ionization trail/layer is thin. When the FAI length along B is 20 m, the po...

Astronomical light echoes, the time-dependent light scattered by dust in the vicinity of varying objects, have been recognized for over a century. Initially, their utility was thought to be confined to mapping out the three-dimensional distribution of interstellar dust. Recently, the discovery of spectroscopically useful light echoes around centuries-old supernovae in the Milky Way and the Larg...

Quantitative ultrasound (QUS) techniques that parameterize the backscattered signal power spectrum have demonstrated significant promise for ultrasonic tissue characterization. Some QUS parameters, including the effective scatterer diameter (ESD) and the effective acoustic concentration (EAC) that can be used for disease detection and diagnosis, require the assumption that the examined medium c...

A new echo phenomenon in proteins, a generalization of so-called temperature quench echoes, is introduced and shown to reveal, through molecular dynamics simulations, periodic motions ~normal modes! in proteins with phase coherence times of about one picosecond. The echoes are induced through reassignments of Cartesian velocities to protein atoms at times t50 and t5t ~0,t<1 ps! and appear as tw...

It has been previously demonstrated by our group that a visual stimulus made of dynamically changing luminance evokes an echo or reverberation at ~10 Hz, lasting up to a second. In this study we aimed to reveal whether similar echoes also exist in the auditory modality. A dynamically changing auditory stimulus equivalent to the visual stimulus was designed and employed in two separate series of...

In this preliminary study we report on a new neonatal cerebral ultrasound appearance consisting of high amplitude echoes that arise diffusely throughout the brain and obscure the echoes of normal structures. This scan appearance was associated with probable cerebral insult and we believe that it is caused by cerebral oedema.