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The use of the Silicon-on-Insulator (SOI) platform has been prominent for realizing CMOS-compatible, high-performance photonic integrated circuits (PICs). But in recent years, the silicon-nitride-on-silicon-dioxide (SiN-on-SiO$_2$) platform has garnered increasing interest as an alternative, because of its several beneficial properties over the SOI platform, such as low optical losses, high thermo-optic stability, broader wavelength transparency range, and high tolerance to fabrication-process variations. However, SiN-on-SiO$_2$ based active devices, such as modulators, are scarce and lack in desired performance due to the absence of free-carrier-based activity in the SiN material and the complexity of integrating other active materials with SiN-on-SiO$_2$ platform. This shortcoming hinders the SiN-on-SiO$_2$ platform for realizing active PICs. To address this shortcoming, in this article, we demonstrate a SiN-on-SiO$_2$ microring resonator (MRR) based active modulator. Our designed MRR modulator employs an Indium-Tin-Oxide (ITO)-SiO$_2$-ITO thin-film stack as the active upper cladding and leverages the free-carrier assisted, high-amplitude refractive index change in the ITO films to affect a large electro-refractive optical modulation in the device. Based on the electrostatic, transient, and finite difference time domain (FDTD) simulations, conducted using photonics foundry-validated tools, we show that our modulator achieves 450 pm/V resonance modulation efficiency, $\sim$46.2 GHz 3-dB modulation bandwidth, 18 nm free-spectral range (FSR), 0.24 dB insertion loss, and 8.2 dB extinction ratio for optical on-off-keying (OOK) modulation at 30 Gb/s., Comment: arXiv admin note: substantial text overlap with arXiv:2212.06326

The use of the Silicon-on-Insulator (SOI) platform has been prominent for realizing CMOS-compatible, high-performance photonic integrated circuits (PICs). But in recent years, the silicon-nitride-on-silicon-dioxide (SiN-on-SiO$_2$) platform has garnered increasing interest as an alternative to the SOI platform for realizing high-performance PICs. This is because of its several beneficial properties over the SOI platform, such as low optical losses, high thermo-optic stability, broader wavelength transparency range, and high tolerance to fabrication-process variations. However, SiN-on-SiO$_2$ based active devices such as modulators are scarce and lack in desired performance, due to the absence of free-carrier based activity in the SiN material and the complexity of integrating other active materials with SiN-on-SiO$_2$ platform. This shortcoming hinders the SiN-on-SiO$_2$ platform for realizing active PICs. To address this shortcoming, we demonstrate a SiN-on-SiO$_2$ microring resonator (MRR) based active modulator in this article. Our designed MRR modulator employs an Indium-Tin-Oxide (ITO)-SiN-ITO thin-film stack, in which the ITO thin films act as the upper and lower claddings of the SiN MRR. The ITO-SiN-ITO thin-film stack leverages the free-carrier assisted, high-amplitude refractive index change in the ITO films to effect a large electro-refractive optical modulation in the device. Based on the electrostatic, transient, and finite difference time domain (FDTD) simulations, conducted using photonics foundry-validated tools, we show that our modulator achieves 280 pm/V resonance modulation efficiency, 67.8 GHz 3-dB modulation bandwidth, $\sim$19 nm free-spectral range (FSR), $\sim$0.23 dB insertion loss, and 10.31 dB extinction ratio for optical on-off-keying (OOK) modulation at 30 Gb/s.

We sought to determine the contemporary prevalence and management of coronary chronic total occlusions (CTO) in a veteran population.The prevalence and management of CTOs in various populations has received limited study.We collected clinical and angiographic data in consecutive patients that underwent coronary angiography at our institution between January 2011 and December 2012. Coronary artery disease (CAD) was defined as ≥50% diameter stenosis in ≥1 coronary artery. CTO was defined as total coronary artery occlusion of ≥3 month duration.Among 1,699 patients who underwent angiography during the study period, 20% did not have CAD, 20% had CAD and prior coronary artery bypass graft surgery (CABG), and 60% had CAD but no prior CABG. The prevalence of CTO among CAD patients with and without prior CABG was 89 and 31%, respectively. Compared to patients without CTO, CTO patients had more co-morbidities, more extensive CAD and were more frequently referred for CABG. Percutaneous coronary intervention (PCI) to any vessel was performed with similar frequency in patients with and without CTO (50% vs. 53%). CTO PCI was performed in 30% of patients without and 15% of patients with prior CABG with high technical (82 and 75%, respectively) and procedural success rates (80 and 73%, respectively).In a contemporary veteran population, coronary CTOs are highly prevalent and are associated with more extensive co-morbidities and higher likelihood for CABG referral. PCI was equally likely to be performed in patients with and without CTO.

KEY POINTS: The beneficial effects of sustained or lifelong (>25 years) endurance exercise on cardiovascular structure and exercise function have been largely established in men. The current findings indicate that committed (≥4 weekly exercise sessions) lifelong exercise results in substantial benefits in exercise capacity ( V O 2 max ), cardiovascular function at submaximal and maximal exercise, left ventricular mass and compliance, and blood volume compared to similarly aged or even younger (middle-age) untrained women. Endurance exercise training should be considered a key strategy to prevent cardiovascular disease with ageing in women as well as men. ABSTRACT: This study was a retrospective, cross-sectional analysis of exercise performance and left ventricular (LV) morphology in 70 women to examine whether women who have performed regular, lifelong endurance exercise acquire the same beneficial adaptations in cardiovascular structure and function and exercise performance that have been reported previously in men. Three groups of women were examined: (1) 35 older (>60 years) untrained women (older untrained, OU), (2) 13 older women who had consistently performed four or more endurance exercise sessions weekly for at least 25 years (older trained, OT), and (3) 22 middle-aged (range 35-59 years) untrained women (middle-aged untrained, MU) as a reference control for the appropriate age-related changes. Oxygen uptake ( V O 2 ) and cardiovascular function (cardiac output ( Q ); stroke volume (SV) acetylene rebreathing) were examined at rest, steady-state submaximal exercise and maximal exercise (maximal oxygen uptake, V O 2 max ). Blood volume (CO rebreathing) and LV mass (cardiac magnetic resonance imaging), plus invasive measures of static and dynamic chamber compliance were also examined. V O 2 max (p

BACKGROUND: Sedentary aging has deleterious effects on the cardiovascular system, including decreased left ventricular compliance and distensibility (LVCD). Conversely, Masters level athletes, who train intensively throughout adulthood, retain youthful LVCD.OBJECTIVES: The purpose of this study was to test the hypothesis that preservation of LVCD may be possible with moderate lifelong exercise training.METHODS: Healthy seniors (n = 102) were recruited from predefined populations, screened for lifelong patterns of exercise training, and stratified into 4 groups: "sedentary" (

Background— Recent reports have suggested that long-term, intensive physical training may be associated with adverse cardiovascular effects, including the development of myocardial fibrosis. However, the dose–response association of different levels of lifelong physical activity on myocardial fibrosis has not been evaluated. Methods and Results— Seniors free of major chronic illnesses were recruited from predefined populations based on the consistent documentation of stable physical activity over >25 years and were classified into 4 groups by the number of sessions/week of aerobic activities ≥30 minutes: sedentary (group 1), Conclusions— A lifelong history of consistent physical activity, regardless of dose ranging from sedentary to competitive marathon running, was not associated with the development of focal myocardial fibrosis.

MAXIMAL exercise capacity declines with healthy aging as evident by a reduction in maximal oxygen uptake (VO2max) (1–6). Cross-sectional studies (3,7) have shown that a reduction in maximal cardiac output (QCmax) significantly contributes to the age-related decline in VO2max in healthy individuals. Although it is clearly established that maximal heart rate declines with age (3,7,8), previous findings regarding the effect of healthy aging on maximal stroke volume (SVmax) are conflicting (3,7,9–12). Stroke volume during exercise is significantly influenced by total blood volume (TBV) via left ventricular end-diastolic volume and thus the Frank–Starling mechanism (13,14). Small sample studies have reported that TBV is reduced in both sexes with healthy aging as a result of a smaller plasma and erythrocyte volume (15–17). Consequently, it has been hypothesized that a reduction in TBV may contribute to a smaller SVmax with advancing age (15,17,18). However, VO2max, TBV, and SVmax have rarely been collected simultaneously in healthy aging individuals to support or refute this hypothesis. Confounding the interpretation of these data is the fact that cardiovascular anatomic and physiologic variables increase with body size (19,20). Accordingly, SVmax and TBV are frequently scaled to total body mass or body surface area (BSA) to compare populations of different body sizes (7,15–17,20,21). However, given that oxygen uptake during exercise is driven by metabolically active tissue (22), scaling cardiovascular determinants of oxygen transport to metabolically active tissue (fat-free mass, FFM) may provide a more precise assessment of cardiovascular capacity in populations of different body sizes and composition. Therefore, the purpose of this study was twofold: (a) to determine whether the age-related decline in VO2max is associated with a reduction in SVmax and TBV and (b) to examine to what extent scaling size-related cardiovascular determinants of VO2max affects the interpretation of age-related differences. Given the age-associated increase in total body mass and adiposity, we hypothesized that SVmax and TBV would be reduced with age when scaled to total body mass and BSA but preserved when scaled to FFM.

Doppler ultrasound measures of left ventricular (LV) active relaxation and diastolic suction are slowed with healthy aging. It is unclear to what extent these changes are related to alterations in intrinsic LV properties and/or cardiovascular loading conditions. Seventy carefully screened individuals (38 female, 32 male) aged 21–77 were recruited into four age groups (young