Objective: To study the effect of obesity on retinal structures in African Americans (AAs) and Caucasian Americans (CAs) with relapsing-remitting multiple sclerosis (RRMS).Methodology: About 136 patients with RRMS without history of optic neuritis were divided into two groups, based on body mass index (BMI): 67 obese (40 AA, 27 CA, mean BMI ± SD: 36.7 ± 5.8), and 69 non-obese (23 AA, 46 CA, mean BMI ± SD: 24.0 ± 3.1). The peripapillary retinal nerve fiber layer (pRNFL) thickness was quantified by optical coherence tomography (OCT) and was segmented into quadrant thickness: superior (S), inferior (I), temporal (T), and nasal (N). Papillomacular bundle (PMB) thickness, retinal nerve fiber layer (RNFL), ganglion cell + inner plexiform layer (GCIPL), inner nuclear (INL), outer plexiform (OPL), outer nuclear (ONL), and total macular (TMV) volumes were obtained.Results: Obesity was associated with lower T thickness (58.54 ± 15.2 vs. 61.9 12.4, p = 0.044), higher INL (0.98 ± 0.07 vs. 0.96 ± 0.06, p = 0.034), and lower RNFL (0.77 ± 0.14 vs. 0.82 ± 0.12, p = 0.009) volumes. Obese AA had significantly thinner T (58.54 ± 15.19 vs. 61.91 ± 12.39, p = 0.033), N (68.94 ± 2.7 vs. 77.94 ± 3.3, p = 0.044), and TMV (8.15 ± 0.07 vs. 8.52 ± 0.09, p = 0.003), RNFL (0.74 ± 0.02 vs. 0.82 ± 0.02, p = 0.013), OPL (0.76 ± 0.01 vs. 0.79 ± 0.1, p = 0.050), ONL (1.68 ± 0.031 vs. 1.79 ± 0.038, p = 0.026), and GCIPL (1.78 ± 0.04 vs. 1.9 ± 0.05, p = 0.038) compared to obese CA. Among patients with non-obesity, the ONL was significantly lower in AA (1.78 ± 0.04 vs. 1.9 ± 0.05, p < 0.001).Conclusions: Obesity is associated with retinal structure abnormalities in patients with RRMS. Its impact might be more prominent in AA than CA. Large longitudinal studies are needed to validate our findings.

A cubic-spring restoring function with high-deformation stiffening is introduced to passively improve the harnessed marine hydrokinetic power by using flow-induced oscillations/vibrations (FIO/V) of a cylinder. In these FIO/V experiments, a smooth, rigid, single-cylinder on elastic end-supports is tested at Reynolds numbers ranging from 24,000 < Re < 120,000. The parameters of the tested current energy converter (CEC) are cubic stiffness and linear damping. Using the second generation of digital virtual spring-damping (Vck) controller developed by the Marine Renewable Energy Laboratory (MRELab), the cubic modeling of the oscillator stiffness is tested. Experimental results show the influence of the parameter variation on the amplitude, frequency, energy conversion, energy efficiency, and power of the converter. All experiments are conducted in the low turbulence-free surface water (LTFSW) channel of the MRELab of the University of Michigan. The main conclusions are: (1) The nonlinearity in the cubic oscillator is an effective way to extend the vortex-induced vibration (VIV) upper branch, which results in higher harnessing power and efficiency compared to the linear stiffness cylinder converter. (2) Compared to the linear converter, the overall power increase is substantial. The nonlinear power optimum, occurring at the end of the VIV upper branch, is 63% higher than its linear counterpart. (3) The cubic stiffness converter with low harnessing damping achieves consistently good performance in all the VIV regions because of the hardening restoring force, especially at higher flow velocity.

Flow Induced Oscillations/Vibrations (FIO/V) of cylinders in tandem can be enhanced by proper in-flow spacing to increase hydrokinetic energy harnessing. In a farm of multiple cylinders in tandem, the effect of interference on harnessing efficiency arises. Three years of systematic experiments in the Marine Renewable Laboratory (MRELab) of the University of Michigan, on an isolated cylinder, and two and three cylinders in tandem have revealed that synergistic FIO can enhance oscillations of cylinders in close proximity. Two cylinders in tandem can harness 2.5-13.5 times the hydrokinetic power of one isolated cylinder. Three cylinders in tandem can harness 3.4-26.4 times the hydrokinetic power of one isolated cylinder. Negative impact on the harnessed energy by multiple cylinders, such as the shielding effect for the downstream cylinder/s, is possible. Specifically for the three-cylinder configuration, at certain flow speed, the decrease in the power of the middle cylinder can be overcome by adjusting its stiffness and/or damping.