The nonlinear dynamics of Taylor-Couette flow in a small aspect ratio annulus (where the length of the cylinders is half of the annular gap between them) is investigated by numerically solving the full three-dimensional Navier-Stokes equations. The system is invariant to arbitrary rotations about the annulus axis and to a reflection about the annulus half-height, so that the symmetry group is S...

PURPOSE The aim of this study was to evaluate a newly-designed mitral annuloplasty strip (the Mitra-Lift(®) strip) in patients undergoing mitral valve repair for mitral regurgitation (MR). METHODS A total of 30 patients who underwent posterior mitral strip annuloplasty for moderately severe to severe MR were evaluated in this study. The strip annuloplasty (SA) consisted of the use of the newl...

AIMS To study left ventricular mechanics of exercise with Doppler and tissue Doppler. METHODS AND RESULTS Twenty-one males (mean age, 26; height, 184 cm; weight, 84 kg), exercised on a bicycle, with increasing workload, with oxygen uptake, Doppler flow and tissue Doppler recordings during exercise. There was correlation between peak systolic LVOT flow and annulus velocity; R=0.72, (p<0.001) a...

Measurement of the shape and motion of the mitral valve annulus has proven useful in a number of applications, including pathology diagnosis and mitral valve modeling. Current methods to delineate the annulus from four-dimensional (4D) ultrasound, however, either require extensive overhead or user-interaction, become inaccurate as they accumulate tracking error, or they do not account for annul...

We consider the homeomorphisms of the compact annulus A = S1 × [−1, 1] isotopic to the symmetry SA which interchanges the two boundary components. We prove that if such a homeomorphism is, in some sense, conservative and twisted, then it possesses a periodic orbit of period exactly two. This can be regarded as a counterpart of the Poincaré-Birkhoff theorem in the isotopy class of SA.

To characterize when a nilpotent singular point of an analytic differential system is a center is of particular interest, first for the problem of distinguishing between a focus and a center, and after for studying the bifurcation of limit cycles from it or from its period annulus. We give an effective algorithm in the search of necessary conditions for detecting nilpotent centers based in rece...

We investigated the influence of the relative phase of a temporally modulated annulus on the perceived flicker strength of a center stimulus having the same temporal modulation. These measurements were performed in two subjects at two temporal frequencies and with different outer diameters of the annulus. The perceived flicker strength was strongly modulated by the phase difference between cent...

In this article, we study the planar cubic polynomial differential system ẋ = −yR(x, y) ẏ = xR(x, y) where R(x, y) = 0 is a conic and R(0, 0) 6= 0. We find a bound for the number of limit cycles which bifurcate from the period annulus of the center, under piecewise smooth cubic polynomial perturbations. Our results show that the piecewise smooth cubic system can have at least 1 more limit cycle...

This paper analyzed the characteristics of managed pressure drilling (MPD) technology and impact of wellhead back pressure on the wellbore annulus pressure profile, and found that the application of this technology provides room for improvement to the current casing program design. Meanwhile, the equivalent density of drilling fluid in wellbore annulus needs to consider the impact of back press...