Ultra-high Q alumina optical microresonators in the UV and blue bands

UV and visible photonics enable applications ranging from spectroscopic sensing to communication and quantum information processing. Photonics structures in these wavelength regimes, however, tend to experience higher loss than their IR counterpart. Particularly in the near-UV band, on-chip optical microresonators have not yet achieved a quality factor beyond 1 million. Here we report ultra-low-loss photonic waveguides and resonators patterned from alumina thin films prepared by a highly scalable atomic layer deposition process. We demonstrate ultra high Q factor of 1.5$\,\times\,$10$^6$ at 390nm, a record value at UV bands, and 1.9$\,\times\,$10$^6$ at 488.5nm

Anti-inflammatory Effects of α7-nicotinic ACh Receptors are Exerted Through Interactions with Adenylyl Cyclase-6

Background and purpose Alpha 7 nicotinic acetylcholine receptors (CHRNA7) suppress inflammation through diverse pathways in immune cells, so is potentially involved in a number of inflammatory diseases. However, the detailed mechanisms underlying CHRNA7’s anti‐inflammatory effects remain elusive. Experimental approach The anti‐inflammatory effects of CHRNA7 agonists in both murine macrophages (RAW 264.7) and bone marrow‐derived macrophages (BMDM) stimulated with LPS were examined. The role of adenylyl cyclase 6 (AC6) in Toll‐like Receptor 4 (TLR4) degradation was explored via overexpression and knockdown. A mouse model of chronic obstructive pulmonary disease was used to confirm key findings. Results Anti‐inflammatory effects of CHRNA7 were largely dependent on AC6 activation, as knockdown of AC6 considerably abnegated the effects of CHRNA7 agonists while AC6 overexpression promoted them. We found that CHRNA7 and AC6 are co‐localized in lipid rafts of macrophages and directly interact. Activation of AC6 led to the promotion of TLR4 degradation. Administration of CHRNA7 agonist PNU‐282987 attenuated pathological and inflammatory end points in a mouse model of chronic obstructive pulmonary disease (COPD). Conclusion and implications CHRNA7 inhibits inflammation through activating AC6 and promoting degradation of TLR4. The use of CHRNA7 agonists may represent a novel therapeutic approach for treating COPD and likely other inflammatory diseases

Tightening of tropical ascent and high clouds key to precipitation change in a warmer climate

The change of global-mean precipitation under global warming and interannual variability is predominantly controlled by the change of atmospheric longwave radiative cooling. Here we show that tightening of the ascending branch of the Hadley Circulation coupled with a decrease in tropical high cloud fraction is key in modulating precipitation response to surface warming. The magnitude of high cloud shrinkage is a primary contributor to the intermodel spread in the changes of tropical-mean outgoing longwave radiation (OLR) and global-mean precipitation per unit surface warming (dP/dTs) for both interannual variability and global warming. Compared to observations, most Coupled Model Inter-comparison Project Phase 5 models underestimate the rates of interannual tropical-mean dOLR/dTs and global-mean dP/dTs, consistent with the muted tropical high cloud shrinkage. We find that the five models that agree with the observation-based interannual dP/dTs all predict dP/dTs under global warming higher than the ensemble mean dP/dTs from the ∼20 models analysed in this study

International Asteroid Warning Network Timing Campaign : 2019 XS

Peer reviewe

Effect of graphene nanosheets on electrochemical performance of Li4Ti5O12 in lithium-ion capacitors

Abstract In order to improve the electrochemical performance of lithium titanium oxide, Li4Ti5O12 (LTO), for the use in the lithium-ion capacitors (LICs) application, LTO/graphene composites were synthesized through a solid state reaction. The composite exhibited an interwoven structure with LTO particles dispersed into graphene nanosheets network rather than an agglomerated state pristine LTO particles. It was found that there is an optimum percentage of graphene additives for the formation of pure LTO phase during the solid state synthesis of LTO/graphene composite. The effect of graphene nanosheets addition on electrochemical performance of LTO was investigated by a systemic characterization of galvanostatic cycling in lithium and lithium-ion cell configuration. The optimized composite exhibited a decreased polarization upon cycling and delivered a specific capacity of 173mAhg−1 at 0.1C and a well maintained capacity of 65mAhg−1 even at 20C. The energy density of 14Whkg−1 at a power density of 2700Wkg−1 was exhibited by a LIC full cell with a balanced mass ratio of anode to cathode along with a superior capacitance retention of 97% after 3000 cycles at a current density of 0.4Ag−1. This boost in reversible capacity, rate capability and cycling performance was attributed to a synergistic effect of graphene nanosheets, which provided a short lithium ion diffusion path as well as facile electron conduction channels

Path Planning and Bending Behaviors of 3D Printed Continuous Carbon Fiber Reinforced Polymer Honeycomb Structures

Continuous fiber reinforced polymer composites are widely used in load-bearing components and energy absorbers owing to their high specific strength and high specific modulus. The path planning of continuous fiber is closely related to its structural defects and mechanical properties. In this work, continuous fiber reinforced polymer honeycomb structures (CFRPHSs) with different printing paths were designed and fabricated via the fused deposition modeling (FDM) technique. The investigation of fiber dislocation at path corners was utilized to analyze the structural defects of nodes caused by printing paths. The lower stiffness nodes filled with pure polymer due to fiber dislocation result in uneven stiffness distribution. The bending performance and deformation modes of CFRPHSs with different printing paths and corresponding pure polymer honeycomb structures were investigated by three-point bending tests. The results showed that the enhancement effect of continuous fibers on the bending performance of honeycomb structures was significantly affected by the printing paths. The CFRPHSs with a staggered trapezoidal path exhibited the highest specific load capacity (68.33 ± 2.25 N/g) and flexural stiffness (627.70 ± 38.78 N/mm). In addition, the fiber distributions and structural defects caused by the printing paths determine the stiffness distribution of the loading region, thereby affecting the stress distribution and failure modes of CFRPHSs

Ionic liquids-SBA-15 hybrid catalysts for highly efficient and solvent-free synthesis of diphenyl carbonate

Diphenyl carbonate (DPC) is one of the versatile carbonates, and is often used for the production of polycarbonates. In recent years, the catalytic synthesis of DPC has become an important topic but the development of a highly active metal-free catalyst is a great challenge. Herein, a series of ionic liquids-SBA-15 hybrid catalysts with different functional groups have been developed for the synthesis of DPC under solvent-free condition, which are effective and clean instead of the metal-containing catalysts. It is found that in the presence of [SBA-15-IL-OH]Br catalyst, methyl phenyl carbonate (MPC) conversion of 80.5% along with 99.6% DPC selectivity is achieved, the TOF value is thrice higher than the best value reported by using transition metal-based catalysts. Moreover, the catalyst displays remarkable stability and recyclability. This work provides a new idea to design and prepare eco-friendly catalysts in a broad range of applications for the green synthesis of carbonates