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Artificial molecular motors and machines constitute a critical element in the transition from individual molecular motion to the creation of collective dynamic molecular systems and responsive materials. The design of artificial light-driven molecular motors operating with high efficiency and selectivity constitutes an ongoing fundamental challenge. Here we present a highly versatile synthetic approach based on Rieche formylation that boosts the quantum yield of the forward photoisomerization reaction while reaching near-perfect selectivity in the steps involved in the unidirectional rotary cycle and drastically reducing competing photoreactions. This motor is readily accessible in its enantiopure form and operates with nearly quantitative photoconversions. It can easily be functionalized further and outperforms its direct predecessor as a reconfigurable chiral dopant in cholesteric liquid crystal materials.

The impact of tropical cyclones (TCs) on the CO2partial pressure at the sea surface (pCO2sea) and air‐sea CO2flux (FCO2) in the Bay of Bengal (BoB) was quantified based on satellite data and in situ observations between November 2013 and January 2017. The in situ observations were made at the BoB Ocean Acidification mooring buoy. A weak time‐mean net source of 55.78 ± 11.16 mmol CO2m−2year−1at the BoB Ocean Acidification site was estimated during this period. A wide range in increases of pCO2sea(1.0–14.8 μatm) induced by TCs occurred in postmonsoon (October–December), and large decreases of pCO2sea(−14.0 μatm) occurred in premonsoon (March–May). Large vertical differences in the ratio of dissolved inorganic carbon (DIC) to total alkalinity (TA) in the upper layer (ΔDIC/TA) were responsible for increasing pCO2seain postmonsoon. Relatively small values of ΔDIC/TA were responsible for decreasing pCO2seain premonsoon. Five TCs (Hudhud, Five, Kyant, Vardah, and Roanu) were considered. Hudhud significantly enhanced CO2efflux (18.49 ± 3.70 mmol CO2/m2) in oversaturated areas due to the wind effect during the storm and wind‐pumpeffects after the storm. Vardah insignificantly changed FCO2(1.22 ± 0.24 mmol CO2/m2) in undersaturated areas because of the counteraction of these two effects. Roanu significantly enhanced CO2efflux (19.08 ± 3.82 mmol CO2/m2) in highly oversaturated conditions (ΔpCO2> 20 μatm) since the wind effect greatly exceeded the wind‐pump effects. These five TCs were estimated to account for 55 ± 23% of the annual‐mean CO2annual efflux, suggesting that TCs have significant impacts on the carbon cycle in the BoB. We examined the impact by five tropical cyclones on the sea surface pCO2and air‐sea CO2exchange using Bay of Bengal Ocean Acidification moored buoy measurements over the Bay of Bengal. To our knowledge, this is the first study on the different effects of tropical cyclones and vertical differences in the ratio of dissolved inorganic carbon to total alkalinity in the upper layer on the sea surface pCO2and local air‐sea CO2flux. TCs tended to increase the pCO2seain the postmonsoon and to decrease the pCO2seain the premonsoon in the Bay of BengalLarge vertical differences in the ratio of DIC to TA in the upper layer were responsible for increasing pCO2seainduced by TCsTCs were estimated to account for 55 ± 23% of the annual‐mean CO2annual efflux

The Cu-catalyzed regioselective synthesis of phenazine N-oxides was realized from benzoxadiazoles and diaryliodonium salts. The process was initiated by the electrophilic arylation of benzoxadiazoles with diaryliodonium salts and followed by benzocyclization reactions. The further reduction of N-oxides in situ to phenazine scaffolds and deviation to organic fluorescent materials were readily accomplished.

In situ oceanographic measurements were made before and after the passage of Typhoon Wutip in September 2013 over the northern South China Sea. The surface geostrophic circulation over this region inferred from satellite altimetry data features a large‐size anticyclonic eddy, a small‐size cyclonic eddy, and smaller‐size eddies during this period. Significant typhoon‐induced changes occurred in the partial pressure of CO2at the sea surface (pCO2sea) during Wutip. Before the passage of Wutip, pCO2seawas about 392.92 ± 1.83, 390.31 ± 0.50, and 393.04 ± 4.31 μatm over the cyclonic eddy water, the anticyclonic eddy water, and areas outside two eddies, respectively. The entire study region showed a carbon source (1.31 ± 0.46 mmol CO2m−2d−1) before Wutip. In the cyclonic eddy water after Wutip, high sea surface salinity (SSS), low sea surface temperature (SST), and high pCO2sea(413.05 ± 7.56 μatm) made this area to be a carbon source (3.30 ± 0.75 mmol CO2m−2d−1). In the anticyclonic eddy water after Wutip, both the SSS and SST were lower, pCO2seawas also lower (383.03 ± 3.72 μatm), and this area became a carbon sink (–0.11 ± 0.55 mmol CO2m−2d−1), in comparison with the pretyphoon conditions. The typhoon‐induced air‐sea CO2flux reached about 0.03 mmol CO2m−2d−1. Noticeable spatial variations in pCO2seawere affected mainly by the typhoon‐induced mixing/upwelling and vertical stratifications. This study suggests that the local air‐sea CO2flux in the study region was affected significantly by oceanographic conditions during the typhoon. Typhoon Wutip generated significant changes in oceanographic conditions in the surface mixed layer over the northern South China SeaWutip enhanced the pCO2seain the cyclonic eddy and surrounding water and decreased the pCO2seain the anticyclonic eddy waterThe noticeable spatial variation in pCO2seawas affected mainly by the storm‐induced mixing and associated changes in stratifications

A coupled wave‐circulation model is used to examine interactions between surface gravity waves and ocean currents over the eastern Canadian shelf and adjacent deep waters during three severe weather events. The simulated significant wave heights (SWHs) and peak wave periods reveal the importance of wave‐current interactions (WCI) during and after the storm. In two fast‐moving hurricane cases, the maximum SWHs are reduced by more than 11% on the right‐hand side of the storm track and increased by about 5% on the left‐hand side due to different WCI mechanisms on waves on two sides of the track. The dominate mechanisms of the WCI on waves include the current‐induced modification of wind energy input to the wave generation, and current‐induced wave advection and refraction. In the slow‐moving winter storm case, the effect of WCI decreases the maximum SWHs on both sides of the storm track due to different results of the current‐induced wave advection, which is affected greatly by the storm translation speed. The simulated sea surface temperature (SST) cooling induced by hurricanes and SST warming induced by the winter storm are also enhanced (up to 1.2°C) by the WCI mechanisms on circulation and hydrography. The 3D wave forces can affect water columns up to 200 m in all three storm cases. By comparison, the effect of breaking wave‐induced mixing in the ocean upper layer is more important under strong stratification conditions in two hurricane cases than under weak stratification conditions in the winter storm case. A comparative study of wave‐current interactions during three stormsApplication of a coupled model based on a 3D circulation model and a third‐generation wave modelExamining the role of the storm translation speed in wave‐current interactions

Reverse osmosis (RO) is currently the most important desalination technology and it is experiencing significant growth. However, the developments of membrane permselectivity in the past decade have been relatively slow, and membrane fouling remains a severe problem. The excellent water transport properties of biological membranes with specialized transmembrane proteins aquaporins as water-selective channels exceed those commercial membranes for water desalination. Supported phospholipid bilayers (SPBs) can maintain the biological activity of molecules and inhibit other non-specific adsorption of biological molecules. In this study, the main work is mostly focused on conditions ensuring most efficient coverage of the supporting nanofiltration (NF) membranes with phospholipid bilayers. Four different NF membranes as supports are explored to form phospholipid bilayers. The presence of SPBs on the four different NF membranes surface is verified and quantified by atomic force microscope (AFM), attenuated total reflection Fourier transform infrared (ATR-FTIR) and contact angle measurements techniques. The NTR-7450 surface is noticeably smoother, more homogeneous and hydrophobicity. Meanwhile, the top layer of NTR-7450 membrane surface is dense and virtually impermeable to lipids and proteins. Therefore, it is shown that a defect-free SPBs is successfully formed on a NTR-7450.

AbstractReverse osmosis (RO) is currently the most important desalination technology and it is experiencing significant growth. However, the developments of membrane permselectivity in the past decade have been relatively slow, and membrane fouling remains a severe problem. The excellent water transport properties of biological membranes with specialized transmembrane proteins aquaporins as water-selective channels exceed those commercial membranes for water desalination. Supported phospholipid bilayers (SPBs) can maintain the biological activity of molecules and inhibit other non-specific adsorption of biological molecules. In this study, the main work is mostly focused on conditions ensuring most efficient coverage of the supporting nanofiltration (NF) membranes with phospholipid bilayers. Four different NF membranes as supports are explored to form phospholipid bilayers. The presence of SPBs on the four different NF membranes surface is verified and quantified by atomic force microscope (AFM), attenuated total reflection Fourier transform infrared (ATR-FTIR) and contact angle measurements techniques. The NTR-7450 surface is noticeably smoother, more homogeneous and hydrophobicity. Meanwhile, the top layer of NTR-7450 membrane surface is dense and virtually impermeable to lipids and proteins. Therefore, it is shown that a defect-free SPBs is successfully formed on a NTR-7450.

Interactions between surface waves and ocean currents over the northwest Atlantic during Hurricanes Earl and Igor (2010) are investigated using a coupled wave‐circulation model and observational data. Our results show that the coupled model improves the model performance in simulating the surface waves, sea level, water temperature, and salinity. By including the wave‐current interactions (WCIs), the maximum significant wave heights (SWHs) are reduced by more than 10% along the storm tracks and more than 20% over eddies. In the Gulf of Maine (GoM), the simulated SWHs and peak wave periods are also modulated by strong tidal currents. Surface waves, in turn, reduce the semidiurnal tidal amplitudes (up to ∼9%) and currents (up to ∼40%) in the GoM due mainly to the wave‐enhanced bottom stress. Surface waves also increase the peak storm surge (up to ∼19%) during these hurricanes, which is mostly attributed to the wave‐induced forces through Stokes drift and wave dissipation but slightly compensated by the wave‐enhanced bottom stress. The hurricane‐driven surface currents are modulated by waves toward the clockwise direction with a decrease in current speeds of more than ∼60%. This is attributed to the reduced current shear and density gradient resulting from mixing enhanced by wave breaking, but compensated by wave‐induced forces. Salinity and temperature are also modulated by surface waves, mostly through the wave‐induced forces and enhanced mixing by wave breaking. Overall, the coupled model produces higher surface salinity and stronger surface cooling due to the inclusion of the WCIs. Large surface waves generated by storms can have intense interactions with ocean currents. In this study, a coupled wave‐circulation model for the northwest Atlantic is used to investigate wave‐current interactions during Hurricanes Earl and Igor in September 2010. Our results demonstrate that the inclusion of wave‐current interactions in the numerical model improves the model performance over both deep waters and coastal regions. The maximum significant wave heights can be reduced by strong hurricane‐driven currents. Surface waves are also modulated by strong tidal currents in the Gulf of Maine (GoM) and by the Gulf Stream and Labrador Current. Surface waves, in turn, reduce the tidal amplitudes and tidal currents in the GoM and increase the peak storm surge during the two hurricanes. Surface waves also affect ocean currents and cause higher surface salinity and stronger surface cooling. Modulations of waves by hurricane‐driven currents, near‐inertial currents, tides and large‐scale circulationsDecrease of tidal amplitudes and currents due to wave‐enhanced bottom stress and increase of peak storm surges due to wave‐induced forcesHurricane‐driven currents are weakened by enhanced mixing due to wave breaking but strengthened by wave‐induced forces Modulations of waves by hurricane‐driven currents, near‐inertial currents, tides and large‐scale circulations Decrease of tidal amplitudes and currents due to wave‐enhanced bottom stress and increase of peak storm surges due to wave‐induced forces Hurricane‐driven currents are weakened by enhanced mixing due to wave breaking but strengthened by wave‐induced forces

Ocean surface gravity waves can modulate the upper ocean circulation and vertical mixing through air‐sea interactions, wave breaking, Coriolis‐Stokes forcing, Langmuir turbulence and the grid resolved vortex force. However, the roles of these wave induced processes remain uncertain under hurricane conditions. This study examines the impact of these surface wave associated dynamics on the turbulent kinetic energy (TKE), thermal structure and currents in the upper ocean under idealized hurricane forcing using a coupled wave‐circulation model. Eight experiments were conducted with hurricanes moving at three translational speeds. The simulations include two fully coupled experiments and five additional coupled experiments in which wave effects are selectively disabled. All coupled experiments are compared with a baseline circulation simulation. Consistent with previous studies, our results indicate that Langmuir turbulence has the biggest impact on upper ocean currents, temperature and TKE during hurricanes. However, all considered wave effects contribute to vertical mixing and the two‐way fully coupled experiment differs the most from the baseline experiment. The combined wave effects reduce the surface currents by over 0.8 m/s in the front two quadrants of the slow hurricane and enhance the cold wake and near‐surface cooling by as much as 0.6°C, predominantly to the right of the storm track. The wave contributions to the cooling are inversely related to the hurricane translational speed, although their contributions to currents and TKE are correlated with hurricane translational speed. SST differences can alter the latent heat flux driving hurricanes, suggesting that wave dynamics should be included in hurricane forecast models. Waves interact with currents to change the circulation in the upper wind mixed layer of the ocean. This study seeks to quantify wave effects through numerical simulations of idealized hurricanes. Eight different numerical experiments were run to test the wave driven changes to the upper ocean circulation and thermal distribution. Consistent with previous studies, our results indicate that Langmuir turbulence is the largest individual wave‐driven process. The combined effect of surface waves can reduce the currents by over 0.8 m/s and increase the surface cooling by up to 0.6°C. Wave induced changes to the currents and temperature are inversely related to how quickly the hurricane moves. Wave‐current interactions alter the ocean responses to idealized hurricanesWave breaking and Langmuir turbulence enhance vertical mixing and surface coolingConservative Stokes drift terms increase upwelling Wave‐current interactions alter the ocean responses to idealized hurricanes Wave breaking and Langmuir turbulence enhance vertical mixing and surface cooling Conservative Stokes drift terms increase upwelling

Analytical results are obtained for the amplitude of a spherical wave backscattered from a solid cylinder immersed in water. The effects of transducer directivity and transmitted pulse duration are included. Backscatter measurements for comparison with theory are made using straight stainless steel wires ranging from 0.13 to 0.26 mm diameter, and acoustic transceivers operating at 1, 2.25, and 5 MHz. The results are used to evaluate the use of thin wires as standard targets.

A method using a linear shallow water model is presented for decomposing the temporal variability of the barotropic stream function in a high‐resolution ocean model. The method is based on the vertically averaged momentum equations and is applied to the time series of annual mean stream function from the model configuration VIKING20 for the northern North Atlantic. An important result is the role played by the nonlinear advection terms in VIKING20 for driving transport. The method is illustrated by examining how the Gulf Stream transport in the recirculation region responds to the winter North Atlantic Oscillation (NAO). While no statistically significant response is found in the year overlapping with the winter NAO index, there is a tendency for the Gulf Stream transport to increase as the NAO becomes more positive. This becomes significant in lead years 1 and 2 when the mean flow advection and eddy momentum flux contributions, associated with nonlinear momentum advection, dominate. Only after 2 years, does the potential energy term, associated with the density field, start to play a role and it is only after 5 years that the transport dependence on the NAO ceases to be significant. It is also shown that the potential energy contribution to the transport stream function has significant memory of up to 5 years in the Labrador and Irminger Seas. However, it is only around the northern rim of these seas that VIKING20 and the transport reconstruction exhibit similar memory. This is due to masking by the mean flow advection and eddy momentum flux contributions. The Gulf Stream plays an important role in the climate system, redistributing heat and other tracers, including carbon, between the tropics and higher latitudes. How the transport of the Gulf Stream varies, in particular in response to forcing from the atmosphere, is still not fully understood. Here we use a novel decomposition technique to identify the different contributions to the transport variability in a high‐resolution model configuration for the northern North Atlantic. We find an important role for the nonlinear terms in the momentum balance. Transport variations associated with these terms are often not taken account of but can sometimes obscure signals that are present in the density field. A linear shallow water model is shown to be an effective means of decomposing the barotropic transport variability in a high‐resolution, eddying model of the North Atlantic based on the vertically averaged horizontal momentum equationsIn the model, the mean flow advection and eddy momentum flux terms play an important role in the dynamics of the variability of the barotropic transport of the Gulf Stream and its recirculation gyresThe mean flow advection and eddy momentum flux contributions sometimes obscure the transport variability associated with the density field

We show how a barotropic shallow water model can be used to decompose the mean barotropic transport from a high‐resolution ocean model based on the vertically averaged momentum equations. We apply the method to a high‐resolution model of the North Atlantic for which the local vorticity budget is both noisy and dominated by small spatial scales. The shallow water model acts as an effective filter and clearly reveals the transport driven by each term. The potential energy (joint effect of baroclinicity and bottom relief) term is the most important for driving transport, including in the northwest corner, while mean flow advection is important for driving transport along f/Hcontours around the Labrador Sea continental slope. Both the eddy momentum flux and the mean flow advection terms drive significant transport along the pathway of the Gulf Stream and the North Atlantic Current. A linear shallow water model is shown to be an effective means of decomposing the mean barotropic transport from a high‐resolution, eddying model of the North Atlantic based on the vertically averaged horizontal momentum equationsThe potential energy, mean flow advection, and eddy momentum flux terms all contribute to the mean barotropic transport of the Gulf Stream and its extension, including the northwest corner and the Mann EddyMean flow advection is found to play an important role in the interaction between the circulation and the continental slope