Double Layer Metasurface for Enhanced Photon Up Conversion

We present a double-layer dielectric metasurface obtained by stacking a silicon nanodisc array and a silicon photonic crystal slab with equal periodicity on top of each other. We focus on the investigation of electric near-field enhancement effects occurring at resonant excitation of the metasurface and study its optical properties numerically and experimentally. We find that the major difference in multi-layer metasurfaces when compared to conventional single-layer structures appears to be in Rayleigh-Wood anomalies: they are split into multiple different modes which are themselves spectrally broadened. As a proof of concept we cover a double-layer metasurface with a lanthanide-doped up-conversion particle layer and study its interaction with a 1550 nm photoexcitation. We observe a 2.7-fold enhancemed up-conversion photoluminescence by using the stacked metasurface instead of a planar substrate, although only around 1% of the up-conversion material is exposed to enhanced near-fields. Two mechanisms are identified explaining this behavior: First, enhanced near-fields when exciting the metasurface resonantly, and second, light trapping by total internal reflection in the particle layer when the metasurface redirects light into high-angle diffraction orders. These results pave the way for low-threshold and, in particular, broadband photon up-conversion in future solar energy and biosensing applications.Comment: 14 pages, 6 figure

Surgery for type A aortic dissection in patients with cerebral malperfusion: Results from the International Registry of Acute Aortic Dissection

Background: The strategy for intervention remains controversial for patients presenting with type A aortic dissection (TAAAD) and cerebral malperfusion with neurologic deficit. Methods: Surgically managed patients with TAAAD enrolled in the International Registry of Acute Aortic Dissection were evaluated to determine the incidence and prognosis of patients with cerebral malperfusion. Results: A total of 2402 patients underwent surgical repair of TAAAD. Of these, 362 (15.1%) presented with cerebral malperfusion (CM) and neurologic deficits, and 2040 (84.9%) patients had no neurologic deficits at presentation. Patients with CM were more less likely to present with chest pain (66% vs 86.5%; P <.001) and back pain (35.9% vs 44.4%; P =.008). Patients with CM were more likely to present with syncope (48.4% vs 10.1%; P <.001), peripheral malperfusion (52.7% vs 38.0%; P <.001), and shock (16.2% vs 4.1%; P <.001). There was no difference in the incidence of Marfan syndrome (2.8% vs 3.0%; P =.870) or history of known aortic aneurysm (11.7% vs 13.9%; P =.296). Patients with CM were more likely to have a DeBakey I (63.8% vs 47.1%; P <.001) and a pericardial effusion (53.8% vs 40.6; P <.001) on presentation. There was no difference in total arch replacement (21.3% for CM vs 19.5% for no CM; P =.473). Patients with CM had an increased incidence of postoperative cerebrovascular accident (17.5% vs 7.2%; P <.001) and acute kidney injury (28.3% vs 18.1%; P <.001). In-hospital mortality was greater in patients with CM (25.7% vs 12.0%; P <.001). Conclusions: Fifteen percent of patients with TAAAD presented with CM and neurologic deficits. Despite the fact that this subset of the population was older and more likely to present with peripheral malperfusion, cardiac tamponade, and in shock, in-hospital survival was noted in nearly 75% of the patients. Surgeons may continue to offer lifesaving surgery for TAAAD to this critically ill cohort of patients with acceptable morbidity and mortality

Design, Energy, Environmental and Cost Analysis of an Integrated Collector Storage Solar Water Heater Based on Multi-Criteria Methodology

The paper presents a design and operation analysis of an Integrated Collector Storage (ICS) solar water heater, which consists of an asymmetric Compound Parabolic Concentrating (CPC) reflector trough, while the water tank comprises two concentric cylinders. The annulus between these vessels is partially depressurized and contains a small amount of water in the bottom of the outer vessel which dominantly contributes to the heat transfer from the outer to the inner cylinder. A multi-criteria optimization algorithm is applied to re-evaluate the design specifications of the parabolic surface, thus modifying the design of the entire ICS system and predict the necessary number of units for achieving the highest possible effectiveness with minimized fabrication costs and environmental impacts. The environmental footprint of the device is assessed through Life Cycle Assessment (LCA). The produced thermal energy in conjunction with the environmental and economic results are evaluated as a function of different configuration parameters regarding the water storage conditions, the solar radiation and the total pressure inside the annulus. The ultimate aim of the evaluation process is to offer new perspectives on the design principles of environmentally friendly and cost-effective devices with improved thermal performance

Time of day does not influence outcomes in acute type A aortic dissection: Results from the IRAD.

BACKGROUND: Type A acute aortic dissection (TAAAD) represents a surgical emergency requiring intervention regardless of time of day. Whether such a evening effect exists regarding outcomes for TAAAD has not been previously studied using a large registry data. METHODS: Patients with TAAAD were identified from the International Registry of Acute Aortic Dissections (1996-2019). Outcomes were compared between patients undergoing operative repair during the daytime (D), defined as 8 am-5 pm, versus the evening (N), defined as 5 pm-8 am. RESULTS: Four thousand one-hundrd and ninety-seven surgically treated patients with TAAAD were identified, with 1824 patients undergoing daytime surgery (43.5%) and 2373 patients undergoing evening surgery (56.5%). Daytime patients were more likely to have undergone prior cardiac surgery (13.2% vs. 9.5%; p \u3c .001) and have had a prior aortic dissection (4.8% vs. 3.4%; p = .04). Evening patients were more likely to have been transferred from a referring hospital (70.8% vs. 75.0%; p = .003). Daytime patients were more likely to undergo aortic valve sparing root procedures (23.3% vs. 19.2%; p = .035); however, total arch replacement was performed with equal frequency (19.4% vs. 18.8%; p = .751). In-hospital mortality (D: 17.3% vs. N. 16.2%; p = .325) was similar between both groups. Subgroup analysis examining the effect of weekend presentation revealed no significant mortality difference. CONCLUSIONS: A majority of TAAAD patients underwent surgical repair at night. There were higher rates of postoperative tamponade in evening patients; however, mortality was similar. The expertise of cardiac-dedicated operative and critical care teams regardless of time of day as well as training paradigms may explain similar mortality outcomes in this high risk population