Plankton lattices and the role of chaos in plankton patchiness

Spatiotemporal and interspecies irregularities in planktonic populations have been widely observed. Much research into the drivers of such plankton patches has been initiated over the past few decades but only recently have the dynamics of the interacting patches themselves been considered. We take a coupled lattice approach to model continuous-in-time plankton patch dynamics, as opposed to the more common continuum type reaction-diffusion-advection model, because it potentially offers a broader scope of application and numerical study with relative ease. We show that nonsynchronous plankton patch dynamics (the discrete analog of spatiotemporal irregularity) arise quite naturally for patches whose underlying dynamics are chaotic. However, we also observe that for parameters in a neighborhood of the chaotic regime, smooth generalized synchronization of nonidentical patches is more readily supported which reduces the incidence of distinct patchiness. We demonstrate that simply associating the coupling strength with measurements of (effective) turbulent diffusivity results in a realistic critical length of the order of 100 km, above which one would expect to observe unsynchronized behavior. It is likely that this estimate of critical length may be reduced by a more exact interpretation of coupling in turbulent flows

Is Carotid Atherosclerosis More Important in Patients with Mitral Annular Calcification than in Those without?

It has been suggested that mitral annular calcification (MAC) may be a manifestation of generalized atherosclerosis. However, how the incidence and extent of coronary artery disease (CAD) are affected by the coexistence of carotid atherosclerosis (CAS) in patients with versus without MAC have not yet been studied. We studied 101 patients with echocardiographic MAC and 52 controls without MAC to investigate the clinical impact of CAS on the frequency and severity (defined as the number of obstructed vessels) of CAD in patients with MAC. Carotid Doppler ultrasonographic examination was performed on all patients before coronary angiography. In patients with both MAC and CAS, the incidences of CAD and multivessel disease (greater than or equal to 2 vessel or left main coronary artery disease) were significantly higher than in the control group with CAS alone (91% versus 68%, P = 0.008 and 76% versus 44%, P = 0.004, respectively). On the other hand, among study and control patients without CAS, although the frequencies of CAD and multivessel disease were higher in patients with MAC, interestingly, the differences were not statistically significant (37% versus 58% and 15% versus 26%, respectively, P>0.05 for both). Stepwise multiple logistic regression analysis revealed that CAS (P<0.001), MAC (P<0.01) and, to a limited extent hypertension (P = 0.054), were independent predictors for the presence of CAD. In conclusion, the coexistence of CAS is more important in patients with MAC than in those without as it provides valuable information about the incidence and severity of underlying CAD. In cases with MAC but without CAS, MAC could be caused by factors other than atherosclerosis.WoSScopu