Prognostic Factors Associated with Post-Stroke Dysphagia in Intracerebral Hemorrhage Patients.

Spontaneous intracerebral hemorrhage (ICH) constitutes a significant portion of acute stroke incidents worldwide, often leading to post-stroke dysphagia (PSD), affecting 50-77% of survivors and worsening patient morbidity. This study aimed to identify predictive variables for PSD among patients with spontaneous ICH. A retrospective cohort study was conducted on adult patients with acute spontaneous ICH, confirmed by brain computed tomography, from June 2019 to June 2023. We analyzed demographic, neuroimaging, and stroke-specific characteristics and rehabilitation indicators. PSD was evaluated using nasogastric (NG) tube retention and the Functional Oral Intake Scale (FOIS) levels at 4 and 12 weeks post-ICH. Statistical analyses involved univariate and multivariate logistic regression to identify PSD predictors. A total of 310 ICH patients were included in the study. At 4 weeks, significant predictors for NG tube retention included 24-hour National Institute of Health Stroke Scale (NIHSS) scores, estimated glomerular filtration rate and sitting balance. At 12 weeks, hospital stay duration and ICH score were significant predictors for NG tube retention. Regarding the FOIS, significant predictors at 4 weeks included higher 24-hour NIHSS scores, compromised sitting balance, immobility-related complications, initial hematoma volume and intraventricular hemorrhages. At 12 weeks, older age and higher 24-hour NIHSS scores significantly predicted lower FOIS levels. Our findings demonstrate that PSD in ICH patients is influenced by a complex interplay of factors, including stroke severity, renal function, and physical impairment. The study highlights the importance of early neurological assessment, physical function, and comprehensive management in improving swallowing outcomes, emphasizing a multifaceted approach to enhancing outcomes for ICH survivors.

Observation of second-harmonic generation in silicon nitride waveguides through bulk nonlinearities.

We present experimental results on the observation of a bulk second-order nonlinear susceptibility, derived from both free-space and integrated measurements, in silicon nitride. Phase-matching is achieved through dispersion engineering of the waveguide cross-section, independently revealing multiple components of the nonlinear susceptibility, namely χ(2) yyy = 0.14 ± 0.08 pm/V and χ(2) xxy = 0.30 ± 0.18 pm/V. Additionally, we show how the second-harmonic signal may be tuned through the application of bias voltages across silicon nitride. The material properties measured here are anticipated to allow for the realization of new nanophotonic devices in CMOS-compatible silicon nitride waveguides, adding to their viability for telecommunication, data communication, and optical signal processing applications.

Effect of dielectric claddings on the electro-optic behavior of silicon waveguides.

We fabricate silicon waveguides in silicon-on-insulator (SOI) wafers clad with either silicon dioxide, silicon nitride, or aluminum oxide and, by measuring their electro-optic behavior, we characterize the capacitively induced free-carrier effect. By comparing our results with simulations, we confirm that the observed voltage dependences of the transmission spectra are due to changes in the concentrations of holes and electrons within the semiconductor waveguides and show how strongly these effects depend on the cladding material that comes into contact with the waveguide. Waveguide loss is additionally found to have a high sensitivity to the applied voltage, suggesting that these effects may find use in applications that require low- or high-loss propagation. These phenomena, which are present in all semiconductor waveguides, may be incorporated into more complex waveguide designs in the future to create high-efficiency electro-optic modulators and wavemixers.

Microwave signal switching on a silicon photonic chip.

Microwave photonics uses light to carry and process microwave signals over a photonic link. However, light can instead be used as a stimulus to microwave devices that directly control microwave signals. Such optically controlled amplitude and phase-shift switches are investigated for use in reconfigurable microwave systems, but they suffer from large footprint, high optical power level required for switching, lack of scalability and complex integration requirements, restricting their implementation in practical microwave systems. Here, we report Monolithic Optically Reconfigurable Integrated Microwave Switches (MORIMSs) built on a CMOS compatible silicon photonic chip that addresses all of the stringent requirements. Our scalable micrometer-scale switches provide higher switching efficiency and require optical power orders of magnitude lower than the state-of-the-art. Also, it opens a new research direction on silicon photonic platforms integrating microwave circuitry. This work has important implications in reconfigurable microwave and millimeter wave devices for future communication networks.

Electronic Metamaterials with Tunable Second-order Optical Nonlinearities.

The ability to engineer metamaterials with tunable nonlinear optical properties is crucial for nonlinear optics. Traditionally, metals have been employed to enhance nonlinear optical interactions through field localization. Here, inspired by the electronic properties of materials, we introduce and demonstrate experimentally an asymmetric metal-semiconductor-metal (MSM) metamaterial that exhibits a large and electronically tunable effective second-order optical susceptibility (χ(2)). The induced χ(2) originates from the interaction between the third-order optical susceptibility of the semiconductor (χ(3)) with the engineered internal electric field resulting from the two metals possessing dissimilar work function at its interfaces. We demonstrate a five times larger second-harmonic intensity from the MSM metamaterial, compared to contributions from its constituents with electrically tunable nonlinear coefficient ranging from 2.8 to 15.6 pm/V. Spatial patterning of one of the metals on the semiconductor demonstrates tunable nonlinear diffraction, paving the way for all-optical spatial signal processing with space-invariant and -variant nonlinear impulse response.