RESUMEN
Guiding and manipulating GHz frequency acoustic waves in [Formula: see text]-scale waveguides and resonators open up new degrees of freedom to manipulate radio frequency (RF) signals in chip-scale platforms. A critical requirement for enabling high-performance devices is the demonstration of low acoustic dissipation in these highly confined geometries. In this work, we show that gallium nitride (GaN) on silicon carbide (SiC) supports low-loss acoustics by demonstrating acoustic microring resonators with frequency-quality factor ( fQ ) products approaching 1013 Hz at 3.4 GHz. The low dissipation measured exceeds the fQ bound set by the simplified isotropic Akhiezer material damping limit of GaN. We use this low-loss acoustics platform to demonstrate spiral delay lines with on-chip RF delays exceeding [Formula: see text], corresponding to an equivalent electromagnetic delay of ≈ 750 m. Given GaN is a well-established semiconductor with high electron mobility, this work opens up the prospect of engineering traveling wave acoustoelectric interactions in [Formula: see text]-scale waveguide geometries, with associated implications for chip-scale RF signal processing.
RESUMEN
The patterning of silk allows for manufacturing various structures with advanced functionalities for optical and tissue engineering and drug delivery applications. Here, we propose a high-resolution nanoscale patterning method based on field-emission scanning probe lithography (FE-SPL) that crosslinks the biomaterial silk on conductive indium tin oxide (ITO) promoting the use of a biodegradable material as resist and water as a developer. During the lithographic process, Fowler-Nordheim electron emission from a sharp tip was used to manipulate the structure of silk fibroin from random coil to beta sheet and the emission formed nanoscale latent patterns with a critical dimension (CD) of â¼50 nm. To demonstrate the versatility of the method, we patterned standard and complex shapes. This method is particularly attractive due to its ease of operation without relying on a vacuum or a special gaseous environment and without any need for complex electronics or optics. Therefore, this study paves a practical and cost-effective way toward patterning biopolymers at ultra-high level resolution.
Asunto(s)
Bioimpresión/métodos , Nanotecnología/métodos , Seda/química , Animales , Materiales Biocompatibles/química , Bombyx/química , Conductividad Eléctrica , Compuestos de Estaño/químicaRESUMEN
BACKGROUND: Endothermal treatment of the great saphenous vein has become the first line of treatment for superficial venous reflux. A new technique for venous insufficiency is non-thermal ablation with vein sealing system which comprises the endovenous delivery of cyanoacrylate tissue adhesive to the vein causing fibrosis. METHODS: This is a single-center prospective study of treatment of great saphenous vein incompetence in 62 patients with vein sealing system (Biolas VariClose® FG Group, Turkey). All cases were implemented under local anesthesia. Tumescent anesthesia was not required. Patients were not given any nonsteroidal anti-inflammatory drug postoperatively; advised to wear elastic bandages for 1 day; and compression stockings were not offered. RESULTS: Treatment success was defined as complete occlusion of treated vein or recanalized segment shorter than 5 cm. Subtotal recanalization was defined as great saphenous vein flow containing 5-10 cm segment of treated vein. A recanalized great saphenous vein or treatment failure was defined as an open part of the treated vein segment more than 10 cm in length. At 1 week and 1 month control, duplex scans showed total occlusion for all patients (100%), total occlusion for 58 patients (93.5%), and subtotal occlusion for 4 patients (6.5%) at third month. At the end of 6 months, total occlusion 56 patients (90.3%) and subtotal occlusion for 2 patients (3.2%). For 4 (6.5%) patients, no occlusion was observed, and the diameter was >11 mm. Embolization of great saphenous vein with cyanoacrylate has been performed since the beginning of this decade. Combined chemical and physical mechanism of action results in permanent vein closure. In a recently published study, a 24-month occlusion rate of 92% was demonstrated. The most commonly reported complications of cyanoacrylate use for the treatment of varicose vein disease, so far, include ecchymosis and phlebitis. Almeida et al. reported that phlebitis is the most frequent side effect at a rate of 16%. In our study, phlebitis rate was not as high as reported. It may be caused due to shorter time of follow-up in the hospital. CONCLUSION: Endovenous ablation of incompetent great saphenous vein with cyanoacrylate-based glue is feasible. Operation time is short, and tumescent anesthesia is unnecessary as postprocedure compression stockings. Lack of significant side effects and an yearly success rate of 100% are benefits of the system.