Background-The purpose of this study was to analyze the in vivo distribution of absolute wall shear stress (WSS abs ) and oscillatory shear index (OSI) in the carotid bifurcation and to evaluate its dependence on bifurcation geometry, the presence of internal carotid artery (ICA) stenosis, and recanalization therapy. Methods and Results-Time-resolved 3D blood flow was acquired with flow-sensitive 4D MRI in 64 normal carotid bifurcations and 17 carotid arteries with moderate ICA stenosis (48Ϯ6%) or after surgical recanalization. Among 64 normal arteries, atherogenic wall parameters were consistently concentrated in proximal bulb regions of the common (CCA) and internal (ICA) carotid arteries. The fraction of the carotid bulb exposed to atherosclerosis-prone wall parameters (low WSS abs below and high OSI above group-defined 20% and 10% thresholds) was correlated with the individual bifurcation geometry.

BACKGROUND AND PURPOSE: 4D flow MR imaging is an emerging technique that allows visualization and quantification of 3D blood flow in vivo. However, representative studies evaluating its accuracy are lacking. Therefore, we compared blood flow quantification by using 4D flow MR imaging with US within the carotid bifurcation.

For more than 50 years we have known that photosynthetic systems harvest solar energy with almost unit quantum efficiency. However, recent experimental evidence of quantum coherence during the excitonic energy transport in photosynthetic organisms challenges our understanding of this fundamental biological function. Currently, and despite numerous efforts, the causal connection between coherence and efficiency is still a matter of debate. We show, through extensive simulations of quantum coherent transport on networks, that three dimensional structures characterized by centro-symmetric Hamiltonians are statistically more efficient than random arrangements. Moreover, a strong correlation of centro-symmetry with quantum efficiency is also observed under the coherent transport dynamics induced by experimentally estimated electronic Hamiltonians of the Fenna-Mathew-Olson complex of sulfur bacteria and of the cryptophyte PC645 complex of marine algae. The application of a genetic algorithm results in a set of optimized Hamiltonians only when seeded from the experimentally estimated Hamiltonian. These results suggest that what appears to be geometrically disordered complexes may well exhibit an inherent hidden symmetry which enhances the energy transport between chromophores. We are confident that our results will motivate research to explore the properties of nearly centro-symmetric Hamiltonians in realistic environments, and to unveil Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. c fs) [13] shorter than the experimentally reported ones ( ∼ t 660 c fs) [5] at T = 77 K. More recent numerical approaches [14,15] appear to reproduce the experimental findings. Yet, since the experimental results were obtained by measurements on ensembles of individually slightly different molecules, the coherence time for a single molecule would actually be expected to be significantly longer (see, e.g., [16,17] for a discussion on this subject), so that, in the light of these diverse observations, the case appears to be open for further debate. One reason being that the complexity of the quantum New J. Phys. 16 (2014) 055002 T Zech et al New J. Phys. 16 (2014) 055002 T Zech et al 3 3Indeed, we will therefore come up here with a deliberately simple and somewhat abstract model, which restricts the Hamiltonian description of the system to a single excitation of the electronic degrees of freedom on a graph-like configuration space. The influence of the-possibly strongly coupled-vibrational degrees of freedom will be accounted for phenomenologically, by statistical sampling over the graph conformation. New J. Phys. 16 (2014) 055002 T Zech et al 4 4 While the isotropic model here employed can be extended to account for different dipolar orientations, weverified that this does not qualitatively change the results presented below (see also [30]). The same is tru...

We evaluated an MRI protocol at 3 T for the assessment of morphological and functional properties of the common carotid artery (CCA) in 32 healthy volunteers and 20 patients with high-grade internal carotid artery stenosis. Wall thickness of the CCA was measured by using multislice 2D T2 dark blood fast spin echo sequences and compared with intima-media thickness (IMT) determined by ultrasound. Carotid distensibility coefficient (DC) quantified by blood pressure and CCA diameter change during the cardiac cycle was measured by ECG gated 3D T1 CINE MRI and M-mode ultrasound. Apart from generally higher values in MRI high agreement was found for wall thickness and compliance in volunteers and patients. Remaining differences between both methods may be attributed to slightly different methods for measuring IMT and DC. Our findings indicate that MRI at 3 T is a feasible and promising tool for the comprehensive assessment of normal carotid geometry and function.

We identify regular structures in the globally chaotic spectra of an interacting bosonic quantum gas in tilted periodic potentials. The associated eigenstates exhibit strong localization properties on the lattice, and are dynamically robust against external perturbations. arXiv:1012.4167v2 [cond-mat.quant-gas]