An Application of Discrete Inequality to Second Order Nonlinear Oscillation

AbstractBy using some simple discrete inequalities oscillation criteria are provided for the second order difference equations Δ2yn+an+1ƒ(yn+1)=0 n∈N where the operator Δ is defined by Δyn=yn+1−yn, {an} is a real sequence. The function ƒ is such that uƒ(u)>0 for u≠0 and ƒ(u)−ƒ(v)=g(u, v)(u−v) for u, v≠0 for some nonnegative function g

When is star formation episodic? A delay differential equation negative feedback model

We introduce a differential equation for star formation in galaxies that incorporates negative feedback with a delay. When the feedback is instantaneous, solutions approach a self-limiting equilibrium state. When there is a delay, even though the feedback is negative, the solutions can exhibit cyclic and episodic solutions. We find that periodic or episodic star formation only occurs when two conditions are satisfied. Firstly the delay timescale must exceed a cloud consumption timescale. Secondly the feedback must be strong. This statement is quantitatively equivalent to requiring that the timescale to approach equilibrium be greater than approximately twice the cloud consumption timescale. The period of oscillations predicted is approximately 4 times the delay timescale. The amplitude of the oscillations increases with both feedback strength and delay time. We discuss applications of the delay differential equation (DDE) model to star formation in galaxies using the cloud density as a variable. The DDE model is most applicable to systems that recycle gas and only slowly remove gas from the system. We propose likely delay mechanisms based on the requirement that the delay time is related to the observationally estimated time between episodic events. The proposed delay timescale accounting for episodic star formation in galaxy centers on periods similar to P 10 Myrs, irregular galaxies with P 100 Myrs, and the Milky Way disk with P~ 2Gyr, could be that for exciting turbulence following creation of massive stars, that for gas pushed into the halo to return and interact with the disk and that for spiral density wave evolution, respectively.Comment: submitted to MNRA

Long-term cerebral thromboembolic complications of transapical endocardial resynchronization therapy

Purpose: Cardiac resynchronization therapy (CRT) is an established therapeutic option in selected heart failure patients (pts). However, the transvenous left ventricular (LV) lead implantation remains ineffectual in a considerable number of pts. Transapical LV (TALV) lead implantation is an alternative minimally invasive, surgical, endocardial implantation technique. The aim of the present prospective study is to determine the long-term outcome, including the cerebral thromboembolic complications, of pts

Long-term cerebral thromboembolic complications of transapical endocardial resynchronization therapy

Purpose: Cardiac resynchronization therapy (CRT) is an established therapeutic option in selected heart failure patients (pts). However, the transvenous left ventricular (LV) lead implantation remains ineffectual in a considerable number of pts. Transapical LV (TALV) lead implantation is an alternative minimally invasive, surgical, endocardial implantation technique. The aim of the present prospective study is to determine the long-term outcome, including the cerebral thromboembolic complications, of pts