Electrical Engineering and Computer Science

Trapped-ion quantum computing requires precise optical control for individual qubit manipulation. However, conventional free-space optics face challenges in alignment stability and scalability as the number of qubits increases. Integrated photonics offers a promising alternative, providing miniaturized optical systems on a chip. Here, we propose a design for a multimode photonic circuit integrated with a surface-electrode ion trap capable of targeted and reconfigurable light delivery. Three closely positioned ions can be addressed using a focusing grating coupler that emits multimode light through electrode openings to ions trapped 68 μm above the chip. Simulations show that the couplers achieve a diffraction-limited spot with a 4.3 μm beam waist along the trap axis and 2.2 μm perpendicular to the trap axis. Controlled interference of the TE00 and TE10 modes results in crosstalk of –20 dB to –30 dB at ion separations of 5–8 μm when addressing ions individually, and down to –60 dB when two of the three ions are addressed simultaneously. Additionally, the higher-order TE modes can offer a novel mechanism for driving spin-motion coupling transitions, potentially enabling alternative approaches to quantum gates and simulations. The proposed integrated platform offers a viable path for constructing large-scale trapped-ion systems, leveraging the benefits of nanophotonic design for precise and reliable ion manipulation.

PurposePolymeric heart valves (PHVs) offer the potential to combine the durability of mechanical valves with the favorable hemodynamics of bioprosthetic valves; however, establishing clear relationships between polymer properties and valve-level function remains a key challenge. This study evaluates polycarbonate-based polyurethanes as candidate scaffold materials for polymeric mitral valves through a multiscale structure–function approach.MethodsTwo aromatic polycarbonate-based thermoplastic polyurethanes, Carbothane AC-4095A (CB95-AC) and QuadraSil ARCS 90A (Qsil), were characterized using rheological, mechanical, and spectroscopic analyses. Trileaflet valve scaffolds were fabricated and evaluated using particle image velocimetry (PIV), pressure–flow measurements, and accelerated wear testing (AWT) up to 50 million cycles. Preliminary in vivo performance was assessed following implantation of a CB95-AC valve in an ovine model.ResultsQsil exhibited higher solution viscosity, lower storage modulus, and improved elastic recovery, indicating a more compliant response, whereas CB95-AC demonstrated greater stiffness and tear resistance. Both materials maintained stable valve function, with preserved projected orifice area and repeatable pressure waveforms after AWT. PIV analysis showed physiologic pulsatile inflow and intraventricular vortex formation for both valves, with Qsil producing slightly broader vorticity patterns and CB95-AC exhibiting more localized flow structures. Evaluation of the CB95-AC valve in vivo demonstrated preserved transmitral inflow with low pressure gradients and no evidence of obstruction.ConclusionPolycarbonate-based polyurethanes provide promising performance as polymeric mitral valve scaffolds, with material-dependent differences influencing leaflet mechanics and flow organization while maintaining structural integrity during comparative accelerated wear testing. These findings provide a multiscale framework for evaluating associations between polymer properties, mechanical behavior, and valve-level performance in next-generation polymeric and hybrid tissue-engineered heart valves.

A coupled-oscillator system displays enhanced sensitivity of its saturated steady-state (SS) oscillation frequency to small parameter perturbations near an exceptional-point degeneracy (EPD), a property that can be used to realize EPD-based sensors. Linear PT-symmetric systems, consisting of two coupled resonators, exhibit EPDs around which square-root sensitivity is observed. However, linear models are insufficient for realistic systems that rely on nonlinear, saturable-gain elements, particularly when PT-symmetry is broken. Thus, we study the SS of a general system of two coupled oscillators featuring EPDs and saturable nonlinear gain, using coupled-mode theory. We do this by synthesizing and extending prior SS analyses of the system’s stability and its square-root and cubic-root oscillation frequency sensitivity at a unique third-order SS-EPD. We add an SS analysis of saturated gain, energy, and oscillation-frequency sensitivity in the vicinity of the third-order SS-EPD, enabling characterization of the various SS regimes. We determine that the stable and bistable regions in parameter space directly depend on the saturated-gain values; that the dynamic range of high sensitivity around degenerate conditions is extended by increasing losses, consequently reducing the system’s stored energy; and that, to exploit the cubic-root-like sensitivity associated with the third-order SS-EPD, the suggested working regime is best confined to operation within the weakly coupled regime and not exactly at the third-order SS-EPD. Finally, we apply the model to two electronic circuits that exhibit cubic-root sensitivity, demonstrating the application and limitations of this analysis.

PurposeEarly detection of right ventricular (RV) dysfunction is essential in pulmonary arterial hypertension (PAH) but remains challenging using conventional echocardiography. This study investigates the feasibility of a noninvasive, physics-based framework using three-dimensional (3D) echocardiography that integrates myocardial strain and volumetric flow analysis to characterize RV mechanical performance across stages of PAH.MethodsA prospective pilot study (N = 15) enrolled healthy controls, PAH patients with preserved RV size, and PAH patients with RV dysfunction. Deformation was evaluated by principal strain analysis and by conventional (longitudinal, circumferential) components. Hemodynamic metrics included hemodynamic forces and energetic properties that were derived using a physics-informed volumetric echocardiographic particle image velocimetry (V-Echo-PIV) method applied to contrast-enhanced acquisitions.ResultsDeformation analysis revealed that longitudinal strain was significantly reduced even in PAH patients with preserved RV dimensions, while second principal (secondary) strain showed a distinctive sign reversal, indicating a paradoxical systolic lengthening, early in the disease. The analysis of hemodynamic forces showed a marked reduction in systolic propulsion across all PAH stages. In contrast, energetic abnormalities were predominantly observed at later stage of the disease.ConclusionsThe integration of 3D myocardial strain with fluid dynamics provides a comprehensive physiological assessment of RV remodeling. While strain and systolic propulsion appear as sensitive markers for early dysfunction, diastolic energetics may support disease staging. This noninvasive framework shows promise for early detection and longitudinal monitoring of PAH patients.

Subglottic stenosis continues to be a diagnostic challenge for clinicians, especially in neonates, whose airways can be as small as 2 mm in diameter. Optical coherence tomography has been investigated as a less invasive and thus potentially safer method of imaging the neonatal airway. However, imaging quality and ultimately, diagnostic accuracy, can be impacted by probe positioning and rotation.

BACKGROUND: Mitral annular calcification (MAC) is common and associated with increased cardiovascular risk and, when severe, mitral stenosis (MS). MAC-related MS differs anatomically and hemodynamically from rheumatic MS (RMS), challenging standard diagnostic methods. This study compares structural and flow characteristics, including  kinetic energy losses, across MAC-related MS, RMS, and normal mitral valves, and evaluates the applicability of conventional diagnostic metrics in MAC. METHODS: Three-dimensional transesophageal echocardiographic data sets from 70 patients (22 normal mitral valves, 26 RMS valves, 22 MAC valves) were used to obtain linear, area, and volumetric measurements for valve comparison. Representative valves from each group were converted into 3-dimensional silicone models for in vitro testing in a heart flow simulator. Transmitral flow was assessed with particle image velocimetry, flow energetics were quantified, and coefficients of contraction were derived from geometric and effective orifice areas. RESULTS: Compared with RMS, MAC-related MS had smaller anteroposterior dimensions, reduced valve volume, and lower coefficients of contraction. MAC demonstrated the highest transmitral velocities and energy dissipation in vitro. Unlike the normal model, neither MAC nor RMS produced a consistent transmitral vortex ring. Despite having a larger geometric orifice, MAC MS produced a greater pressure drop than RMS, likely due to increased flow disruption and lower coefficients of contraction. CONCLUSIONS: MAC-related MS represents a unique pathophysiological entity, characterized by distinct structural and hemodynamic features. These findings underscore the necessity for disease-specific diagnostic frameworks and multimodality imaging strategies to inform clinical decision making and guide emerging therapeutic approaches.

Mitochondrial transplantation has emerged as a promising cardioprotective strategy for ischemia-reperfusion injury, aiming to restore bioenergetic function by delivering healthy mitochondria to damaged tissue. However, conflicting reports exist regarding whether mitochondria can survive exposure to the calcium-rich extracellular environment, such as the bloodstream, prior to cellular uptake. Resolving this question is essential for advancing the therapeutic use of mitochondria in clinical settings. Isolated mitochondria from L6 rat skeletal muscle cells were incubated with physiologic (1.3  mM), sub-physiologic (0.65  mM), and supraphysiologic (2.6  mM) concentrations of calcium. Mitochondrial membrane potential was assessed using MitoTracker™ Red FM fluorescence, and structural integrity was evaluated using impedance-based Coulter counter analysis over a 12-hour time course. Mitochondria exposed to 1.3  mM calcium retained 90-95 % membrane potential by 12 h, while 2.6  mM calcium caused progressive loss of function and integrity, approaching levels seen in freeze-thawed controls. Coulter counter measurements revealed more extensive mitochondrial loss across all calcium-treated groups than fluorescence assays alone, suggesting that dye-based methods may underestimate structural damage. Nonetheless, a substantial proportion of mitochondria remained both structurally and functionally intact at physiologically relevant calcium levels. These findings demonstrate that a substantial number of mitochondria can retain membrane potential and structural integrity after exposure to extracellular calcium concentrations approximating those found in blood. This supports the feasibility of intracoronary mitochondrial transplantation and underscores the need for further in vivo studies to optimize survival and efficacy of mitochondria delivered in calcium-rich environments.

PURPOSE: To evaluate changes in myocardial blood flow (MBF) and coronary flow reserve (CFR) over time in a swine model fed a Western diet (WD) using a novel low-dose myocardial CT perfusion technique. MATERIALS AND METHODS: Ten swine with low-density lipoprotein receptor mutations were fed a WD starting at week 0 and imaged after 12, 16, 17, 18, 19, or 23 weeks of WD exposure (mean ± SD: 17.1 ± 3.25 weeks; range 12-23 weeks) using a 320-slice CT scanner under rest and adenosine-induced stress (240 μg/kg/min). Peripheral contrast injection (370 mgI/mL, 0.5 mL/kg, 5 mL/s) with a diluted chaser (30:70 contrast/saline) was followed by bolus tracking and a single-volume scan acquired at peak aortic enhancement (100 kVp, 200 mA). A first-pass analysis model derived MBF (mL/min/g) from bolus-tracking and scan data. Rest and stress MBF were used to compute CFR. Correlations between WD duration and both stress MBF and CFR were assessed. Reproducibility was evaluated through paired repeated scans. The CT dose index was recorded. RESULTS: Starting at 12 weeks post-WD, stress-induced MBF and CFR were strongly correlated with WD duration: MBFstress = -0.05 T + 2.56 (r = -0.93) and CFR = -0.13 T + 4.30 (r = -0.76). Reproducibility between repeated MBF measurements was high (MBF2 = 0.97MBF1 + 0.05; r = 0.99; RMSE = 0.06 mL/min/g). The average CT dose index was 7.4 mGy. CONCLUSION: Prolonged Western diet consumption in this swine model was associated with a progressive decline in stress-induced MBF and CFR, indicating the development of diet-related myocardial microvascular dysfunction. These results suggest that the low-dose single-volume CT perfusion technique can detect early perfusion impairments before overt disease, offering a promising tool for early risk stratification in coronary artery disease. SUMMARY STATEMENT: A novel low-dose, single-volume CT perfusion technique enables early detection of coronary microvascular dysfunction associated with Western diet exposure, providing a non-invasive and radiation-efficient method for assessing myocardial blood flow and coronary flow reserve before the development of significant epicardial stenosis.