Introduction In functional MRI, spiral trajectory has been proposed to reduce the signal dropout in the frontal orbital and lateral parietal region affected by the susceptibility-induced field gradient (SFG) [1-2]. With a spiral-in trajectory, the entire k-space except the origin is sampled before the prescribed echo time TE. This reduces T2* weighting and enhances the BOLD contrast in regions ...

Spiral waves are frequently observed in a large variety of excitable media, such as the Belousov– Zhabotinsky (BZ) reactions [Winfree, 1972; Ouyang & Flesselles, 1996], the catalytic surface processes [Jakubith et al., 1990], the cardiac tissue [Davidenko et al., 1992; Qu et al., 2000] and neural networks [Sbitnev, 1998]. One common feature of spiral waves is that with the variation of the envi...

BOLD fMRI is hampered by dropout of signal in the orbitofrontal and parietal brain regions due to magnetic field gradients near air-tissue interfaces. This work reports the use of spiral-in trajectories that begin at the edge of k-space and end at the origin, and spiral in/out trajectories in which a spiral-in readout is followed by a conventional spiral-out trajectory. The spiral-in trajectory...

We derive regions for T-cubic and arc/T-cubic spirals to two-point Hermite interpolation in terms of unit tangent vectors with help of Mathematica. The use of spirals gives the designer an excellent and speedy control over the shape of curve that is produced because there are no internal curvature maxima, curvature minima, inflection points, loops and cusps in a spiral segment.

Spiral chaos appears in the two-dimensional Aliev-Panfilov model. The generation mechanism of the spiral chaos is related to the breathing instability of pulse trains. The spiral chaos can be eliminated by applying periodic force uniformly. The elimination of the spiral chaos is most effective when the frequency of the periodic force is close to that of the breathing motion.

– The behavior of spiral turbulence in mechanically deformed excitable media is investigated. Numerical simulations show that when the forcing frequency is chosen around the characteristic frequency of the system, complicated spiral turbulence may be quenched within a shorter evolution time, compared to the case free of mechanical deformation. It is shown that the observed phenomenon occurs due...

background since tuberculosis (tb) is a major public health problem that is a leading cause of mortality and morbidity among infectious diseases worldwide, early diagnosis and treatment are important to control an effective tuberculosis (tb) and also the increasing number of patients with atypical manifestations of active tb. it suggests more evaluation for active tb in fibrotic lesion in ct sc...

conclusions our study shows in terms of figures that measurements of features of the temporal bone made from spiral ct scan images and those directly obtained during surgery are similar to an adequate extent. results twenty cases were included. in the three measurements performed in this study, only the first parameter (distance between the canal and the sigmoid sinus) was significantly differe...

BACKGROUND Functional reentry in the heart takes the form of spiral waves. Drifting spiral waves can become pinned to anatomic obstacles and thus attain stability and persistence. Lidocaine is an antiarrhythmic agent commonly used to treat ventricular tachycardia clinically. We examined the ability of small obstacles to anchor spiral waves and the effect of lidocaine on their attachment. METH...

We have previously shown in experimental cardiac cell monolayers that rapid point pacing can convert basic functional reentry (single spiral) into a stable multiwave spiral that activates the tissue at an accelerated rate. Here, our goal is to further elucidate the biophysical mechanisms of this rate acceleration without the potential confounding effects of microscopic tissue heterogeneities in...