Attojoule Hexagonal Boron Nitride-Based Memristor for High-Performance Neuromorphic Computing.

In next-generation neuromorphic computing applications, the primary challenge lies in achieving energy-efficient and reliable memristors while minimizing their energy consumption to a level comparable to that of biological synapses. In this work, hexagonal boron nitride (h-BN)-based metal-insulator-semiconductor (MIS) memristors operating is presented at the attojoule-level tailored for high-performance artificial neural networks. The memristors benefit from a wafer-scale uniform h-BN resistive switching medium grown directly on a highly doped Si wafer using metal-organic chemical vapor deposition (MOCVD), resulting in outstanding reliability and low variability. Notably, the h-BN-based memristors exhibit exceptionally low energy consumption of attojoule levels, coupled with fast switching speed. The switching mechanisms are systematically substantiated by electrical and nano-structural analysis, confirming that the h-BN layer facilitates the resistive switching with extremely low high resistance states (HRS) and the native SiOx on Si contributes to suppressing excessive current, enabling attojoule-level energy consumption. Furthermore, the formation of atomic-scale conductive filaments leads to remarkably fast response times within the nanosecond range, and allows for the attainment of multi-resistance states, making these memristors well-suited for next-generation neuromorphic applications. The h-BN-based MIS memristors hold the potential to revolutionize energy consumption limitations in neuromorphic devices, bridging the gap between artificial and biological synapses.

Electrical Phase Modulation Based on Mid-Infrared Intersubband Polaritonic Metasurfaces.

Electrically reconfigurable metasurfaces that overcome the static limitations in controlling the fundamental properties of scattered light are opening new avenues for functional flat optics. This work proposes and experimentally demonstrates electrically phase-tunable mid-infrared metasurfaces based on the polaritonic coupling of Stark-tunable intersubband transitions in semiconductor heterostructures and electromagnetic modes in plasmonic nanoresonators. In the applied voltage range of -3 to +3 V, the local phase tuning of the light reflects from the metasurface, which enables the electrical control of the polarization state and wavefront of the reflected wave. Electrical beam polarization control, electrical beam diffraction control, and electrical beam steering are experimentally demonstrated as applications for local phase tunability. The proposed electrically tunable metasurfaces can easily tune the operating wavelength and function at relatively low voltages, which will enable various applications in the mid-infrared region.

Hexagonal Boron Nitride for Next-Generation Photonics and Electronics.

Hexagonal boron nitride (h-BN), an insulating 2D layered material, has recently attracted tremendous interest motivated by the extraordinary properties it shows across the fields of optoelectronics, quantum optics, and electronics, being exotic material platforms for various applications. At an early stage of h-BN research, it is explored as an ideal substrate and insulating layers for other 2D materials due to its atomically flat surface that is free of dangling bonds and charged impurities, and its high thermal conductivity. Recent discoveries of structural and optical properties of h-BN have expanded potential applications into emerging electronics and photonics fields. h-BN shows a very efficient deep-ultraviolet band-edge emission despite its indirect-bandgap nature, as well as stable room-temperature single-photon emission over a wide wavelength range, showing a great potential for next-generation photonics. In addition, h-BN is extensively being adopted as active media for low-energy electronics, including nonvolatile resistive switching memory, radio-frequency devices, and low-dielectric-constant materials for next-generation electronics.

Ultrasensitive Molecule Detection Based on Infrared Metamaterial Absorber with Vertical Nanogap.

Surface-enhanced infrared absorption (SEIRA) spectroscopy is a powerful methodology for sensing and identifying small quantities of analyte molecules via coupling between molecular vibrations and an enhanced near-field induced in engineered structures. A metamaterial absorber (MA) is proposed as an efficient SEIRA platform; however, its efficiency is limited because it requires the appropriate insulator thickness and has a limited accessible area for sensing. SEIRA spectroscopy is proposed using an MA with a 10 nm thick vertical nanogap, and a record-high reflection difference SEIRA signal of 36% is experimentally achieved using a 1-octadecanethiol monolayer target molecule. Theoretical and experimental comparative studies are conducted using MAs with three different vertical nanogaps. The MAs with a vertical nanogap are processed using nanoimprint lithography and isotropic dry etching, which allow cost-effective large-area patterning and mass production. The proposed structure may provide promising routes for ultrasensitive sensing and detection applications.

Giant Nonlinear Circular Dichroism from Intersubband Polaritonic Metasurfaces.

Nonlinear metasurfaces are advancing into a new paradigm of "flat nonlinear optics" owing to the ability to engineer local nonlinear responses in subwavelength-thin films. Recently, attempts have been made to expand the design space of nonlinear metasurfaces through nonlinear chiral responses. However, the development of metasurfaces that display both giant nonlinear circular dichroism and significantly large nonlinear optical response is still an unresolved challenge. Herein, we propose a method that induces giant nonlinear responses with near-unity circular dichroism using polaritonic metasurfaces with optical modes in chiral plasmonic nanocavities coupled with intersubband transitions in semiconductor heterostructures designed to have giant second and third order nonlinear responses. A stark contrast between effective nonlinear susceptibility elements for the two spin states of circularly polarized pump beams was seen in the hybrid structure. Experimentally, near-unity nonlinear circular dichroism and conversion efficiencies beyond 10-4% for second- and third-harmonic generation were achieved simultaneously in a single chip.

Fano Metamaterials on Nanopedestals for Plasmon-Enhanced Infrared Spectroscopy.

We report a sensing platform for surface-enhanced infrared absorption (SEIRA) spectroscopy, based on Fano metamaterials (FMMs) on dielectric nanopedestals. FMMs consist of two parallel gold (Au) nanorod antennas, with a small horizontal coupler attached to one of the nanorod antenna. When placed on SiO2 dielectric nanopedestals, which exhibit strong field enhancements caused by the interference between subradiant and superradiant plasmonic resonances, they provide the highly enhanced E-field intensities formed near the Au nanoantenna, which can provide more enhanced molecular detection signals. Here, the sensing characteristics of FMMs on nanopedestals structure was confirmed by comparison with FMMs on an unetched SiO2 substrate as a control sample. The control FMMs and the FMMs on nanopedestals were carefully designed to excite Fano resonance near the target 1-octadecanethiol (ODT) fingerprint vibrations. The FMMs were fabricated by using nanoimprint lithography and the nanopedestal structures were formed by isotropic dry-etching. The experimental reflection spectra containing the enhanced absorption signals of the ODT monolayer molecules was analyzed using temporal coupled-mode theory. The FMMs on nanopedestals achieved over 7% of reflection difference signal, which was 1.7 times higher signal than the one from the control FMMs. Based on the FMMs on nanopedestal structures proposed in this study, it may be widely applied to future spectroscopy and sensor applications requiring ultrasensitive detection capability.

A comprehensive meta-analysis of stem cell therapy for chronic angina.

BACKGROUND: A substantial proportion of patients with coronary artery disease do not achieve complete revascularization and continue to experience refractory angina despite optimal medical therapy. Recently, stem cell therapy has emerged as a potential therapeutic option for these patients. However, findings of individual trials have been scrutinized because of their small sample sizes and lack of statistical power. Therefore, we conducted an updated comprehensive meta-analysis of available randomized controlled trials (RCTs) with the largest sample size ever reported on this subject. HYPOTHESIS: In patients with chronic angina stem cell therapy improves clinical outcomes. METHODS: Scientific databases and websites were searched for RCTs. Data were independently collected by 2 investigators, and disagreements were resolved by consensus. Data from 10 trials including 658 patients were analyzed. RESULTS: Stem cell therapy improved Canadian Cardiovascular Society angina class (risk ratio: 1.53, 95% CI: 1.09 to 2.15, P = 0.013), exercise capacity (standardized mean difference [SMD]: 0.56, 95% CI: 0.23 to 0.88, P = 0.001), and left ventricular ejection fraction (SMD: 0.63, 95% CI: 0.27 to 1.00, P = 0.001) compared with placebo. It also decreased anginal episodes (SMD: -1.21, 95% CI: -2.40 to -0.02, P = 0.045) and myocardial perfusion defects (SMD: -0.70, 95% CI: -1.11 to -0.29, P = 0.001). However, no improvements in all-cause mortality were observed after a relatively short follow-up. CONCLUSIONS: In patients with chronic angina on optimal medical therapy, stem cell therapy improves symptoms, exercise capacity, and left ventricular ejection fraction. These findings warrant confirmation using larger trials.

Quadricuspid aortic valve infective endocarditis.

Infective endocarditis complicating a quadricuspid aortic valve (QAV) is rare. Previous reports highlight the increased risk for complications, including progressive aortic regurgitation, decompensated heart failure, and valve perforation. Thus, cardiologists must be able to quickly identify QAVs to guide rapid evaluation and treatment. We report a case of infective endocarditis in a QAV identified on echocardiography and effectively managed with medical therapy alone without complications over an 8-year follow-up period. © 2017 Wiley Periodicals, Inc. J Clin Ultrasound 46:145-148, 2018.

A web-based tool to predict acute kidney injury in patients with ST-elevation myocardial infarction: Development, internal validation and comparison.

BACKGROUND: In ST-elevation myocardial infarction (STEMI), acute kidney injury (AKI) may increase subsequent morbidity and mortality. Still, it remains difficult to predict AKI risk in these patients. We sought to 1) determine the frequency and clinical outcomes of AKI and, 2) develop, validate and compare a web-based tool for predicting AKI. METHODS & FINDINGS: In a racially diverse series of 1144 consecutive STEMI patients, Stage 1 or greater AKI occurred in 12.9% and was severe (Stage 2-3) in 2.9%. AKI was associated with increased mortality (5.7-fold, unadjusted) and hospital stay (2.5-fold). AKI was associated with systolic dysfunction, increased left ventricular end-diastolic pressures, hypotension and intra-aortic balloon counterpulsation. A computational algorithm (UT-AKI) was derived and internally validated. It showed higher sensitivity and improved overall prediction for AKI (area under the curve 0.76) vs. other published indices. Higher UT-AKI scores were associated with more severe AKI, longer hospital stay and greater hospital mortality. CONCLUSIONS: In a large, racially diverse cohort of STEMI patients, Stage 1 or greater AKI was relatively common and was associated with significant morbidity and mortality. A web-accessible, internally validated tool was developed with improved overall value for predicting AKI. By identifying patients at increased risk, this tool may help physicians tailor post-procedural diagnostic and therapeutic strategies after STEMI to reduce AKI and its associated morbidity and mortality.

Penetrating aortic ulcer leading to aortic dissection.

Rarely, penetrating atherosclerotic ulcers can rupture into the wall of the aorta, resulting in acute aortic dissection. This article describes a woman with an incidental diagnosis of type A aortic dissection secondary to a penetrating atherosclerotic ulcer of the ascending aorta. Although surgical repair of the aortic root was recommended, the patient refused treatment and left against medical advice.

Meta-Analysis of the Relative Efficacy and Safety of Oral P2Y12 Inhibitors in Patients With Acute Coronary Syndrome.

A cornerstone of medical therapy for patients with acute coronary syndrome (ACS) is dual antiplatelet therapy, which includes aspirin and a P2Y12 inhibitor. Randomized controlled trials (RCTs) have shown that prasugrel and ticagrelor are superior to clopidogrel, but none directly compared these 3 commonly used oral P2Y12 inhibitors for safety and efficacy. Therefore, we performed a Bayesian network meta-analysis of RCTs to compare the efficacies and safeties of 3 commonly used oral P2Y12 inhibitors in patients with ACS. Scientific databases and websites were searched for relevant RCTs. We included data from 9 RCTs that enrolled 106,288 patients. Clopidogrel decreased the rates of major adverse cardiac event, recurrent myocardial infarction, and all-cause mortality compared with placebo. Both ticagrelor and prasugrel decreased the rates for major adverse cardiac event and recurrent myocardial infarction compared with clopidogrel, but there was no difference between the 2. Both also decreased the stent thrombosis rate compared with clopidogrel, but prasugrel was more effective than ticagrelor. Ticagrelor use was also associated with improved all-cause and CV mortalities compared with clopidogrel. There was no difference in CV mortality or all-cause mortality between clopidogrel and prasugrel. Prasugrel use was also associated with significantly increased risk of major bleeding compared with clopidogrel but showed a nonsignificant trend toward increasing the risk of bleeding compared with ticagrelor. In treatment ranking, ticagrelor was the most efficacious, and prasugrel was the least safe. In conclusion, this meta-analysis shows that in patients with ACS, adding P2Y12 inhibitors to aspirin and other standard treatments reduces ischemic events and all-cause mortality. Among the commonly used oral P2Y12 inhibitors, ticagrelor has the best net efficacy and safety profile.

When life-threatening conditions appear clinically silent: an atypical presentation of spontaneous coronary artery dissection in a 60-year-old female.

Spontaneous coronary artery dissection is a poorly understood phenomenon that usually affects women during pregnancy or the immediate post-partum period. We present the case of a 60-year-old female with chronic obstructive pulmonary disease who presented with vague complaints of shortness of breath, dizziness, and weakness with a mildly elevated troponin. She denied any anginal symptoms. As part of her initial workup, a nuclear stress test revealed inferior wall reversible changes. Coronary angiography revealed spontaneous right coronary artery dissection which was treated with a drug-eluting stent.

Multiple coronary-cameral fistulas to the left ventricle arising from both coronary arteries.

Coronary-cameral fistula (CCF) is an anomalous connection between a coronary artery and a cardiac chamber or major vessel, seen in about 0.8% of the cases undergoing coronary angiography. Most patients are asymptomatic and diagnosis is made incidentally during coronary angiography. We present an image case of CCF which was found incidentally during pre-liver transplantation work up.

An incidental diagnosis of multiple pacemaker lead fractures.

Lead fractures are uncommon complications of pacemaker implantation. This article describes a patient with an incidental diagnosis of multiple atrial lead fractures many years after pacemaker implantation.

Impella-assisted transcatheter closure of an acute postinfarction ventricular septal defect.

This case report describes a 72-year-old woman who developed an acute postmyocardial infarction ventricular septal defect (VSD) with consequent cardiogenic shock. Intra-aortic balloon pump (IABP) counter-pulsation was urgently initiated in the cardiac catheterisation laboratory, with neither clinical nor haemodynamic improvement, prompting immediate removal of the IABP and the insertion of an Impella 2.5 heart pump (AbioMed Inc; Danvers, Massachusetts, USA), a temporary ventricular assist device. Thereafter, the patient improved clinically and was admitted to the cardiovascular intensive care unit (ICU). While in the cardiovascular ICU, the patient developed worsening mechanical haemolysis of blood cells, stable but persistent cardiogenic shock and a transient ischaemic attack. A consensus decision was made to proceed with percutaneous repair of the VSD as she was deemed at high risk for surgical repair. She underwent successful percutaneous VSD repair on day 4 of hospitalisation, using a single 18 mm Amplatzer muscular VSD occluder (AGA Medical, Plymouth, Minnesota, USA) with trace residual flow across the occluder. Adequate systolic blood pressure and cardiac output was maintained postprocedure with the Impella 2.5 device. The patient, however, succumbed to multiorgan dysfunction occasioned by sepsis.

A case of saddle pulmonary embolus visualized on a transthoracic echocardiography in a 69-year-old female.

A 69-year-old female with history of immobilization presented with shortness of breath and generalized weakness and was found to have large saddle pulmonary embolus on CT scan. Further evaluation with a transthoracic echocardiography revealed a moderately enlarged and hypokinetic right ventricle with a pulmonary artery clot of about 1.5 cm seen at the bifurcation while the ultrasound of the legs was negative for deep vein thrombosis.

A rare presentation of bilateral spontaneous superficial femoral arteriovenous fistulas.

Spontaneous arteriovenous fistulas are a rare clinical entity with very few cases reported in the literature. Prompt diagnosis and treatment is crucial and can prevent further complications in such patients. We report a case of a patient who presented with progressive bilateral claudication, discolouration of feet, hypaesthesia and non-healing ulcers. The patient had no history of trauma, aneurysm or surgery. After abnormal non-invasive studies, a peripheral angiogram revealed significant disease and obstruction of bilateral superficial femoral arteries. Spontaneous bilateral femoral arteriovenous fistulas were also found incidentally. After discussing the risks and benefits of multiple treatment options with the patient, percutaneous intervention with orbital atherectomy, balloon angioplasty and covered stent placements were performed. This treatment improved the patient's symptoms significantly.

Giant right atrial mass obliterating the right atrium.

A73-year-old man with past medical history of mechanical aortic valve replacement, metastatic melanoma of unknown primaries with liver metastasis, presented with progressive shortness of breath and dyspnea on exertion. Transthoracic echocardiography (TTE) showed a large homogenous mass completely occupying the right atrial cavity and extending to and nearly obstructing the inflow area of the tricuspid valve. He was treated with chemotherapy.