The road to recovery: Sensing public opinion towards reopening measures with social media data in post-lockdown cities.

The COVID-19 pandemic has resulted in cities implementing lockdown measures, causing unprecedented disruption (e.g. school/shop/office closures) to urban life often extending over months. With the spread of COVID-19 now being relatively contained, many cities have started to ease their lockdown restrictions by phases. Following the phased recovery strategy proposed by the UK government following the first national lockdown, this paper utilises Greater London as its case study, selecting three main reopening measures (i.e., schools, shops and hospitality reopening). This paper applies sentiment analysis and topic modelling to explore public opinions expressed via Twitter. Our findings reveal that public attention towards the reopening measures reached a peak before the date of policy implementation. The attitudes expressed in discussing reopening measures changed from negative to positive. Regarding the discussed topics related to reopening measures, we find that citizens are more sensitive to early-stage reopening than later ones. This study provides a time-sensitive approach for local authorities and city managers to rapidly sense public opinion using real-time social media data. Governments and policymakers can make use of the framework of sensing public opinion presented herein and utilise it in leading their post-lockdown cities into an adaptive, inclusive and smart recovery.

Effect of expanded polytetrafluoroethylene thickness on paclitaxel release and edge stenosis in stent graft.

Stent grafts have been widely used to treat lower extremity arterial stenosis or occlusion. However, there are major issues with edge stenosis and loss of patency over time. Paclitaxel-coated stent grafts have been proven to be effective in preventing edge stenosis, but the insufficient amounts of paclitaxel released may limit the effectiveness of drug-eluting stent grafts. In this study, we examined whether paclitaxel-coated expanded polytetrafluoroethylene (ePTFE) stent graft thickness influences paclitaxel release properties and inhibits edge stenosis. Low-, medium-, and high-thickness paclitaxel-coated stent grafts were prepared by varying the thickness of inner and outer ePTFE layers. Surface morphologies of the stent grafts were analyzed using a scanning electron microscope. The stent grafts were then implanted in the iliac arteries of 20 healthy swine. Twelve pigs were used to assess edge stenosis, and digital subtraction angiography was performed at day 30 (n = 4), 90 (n = 4), and 180 (n = 4). Histological evaluation of the treated arteries was also performed. Eight pigs were used for pharmacokinetic analysis, and the treated arteries were obtained at day 1 (n = 2), 30 (n = 2), 90 (n = 2) and 180 (n = 2). Scanning electron microscopy confirmed that the mean pore size of the stent grafts decreased with increasing thickness. The results of angiographic and histological evaluation demonstrated that low-thickness ePTFE-stent grafts resulted in edge stenosis and apparent intimal hyperplasia at 180 days, whereas for medium-thickness ePTFE-stent grafts, no obvious edge stenosis and intimal hyperplasia was noted in the similar time period. The results of pharmacokinetic evaluation showed that at 180 days, the paclitaxel concentration of treated arteries of the medium group was 36 ± 53 ng/g, while concentrations in the low group was not detectable. Stent grafts with increased ePTFE thickness appear to allow for more delayed release of paclitaxel compared to low-thickness ePTFEs.

Solar-Assisted, Fast, and In Situ Recovery of Crude Oil Spill by a Superhydrophobic and Photothermal Sponge.

Development of a functional sorbent for effective crude oil absorption is essential to address large-scale spilling incidents. Herein, we demonstrate a facile method for preparing a superhydrophobic and photothermal PDMS/CuS/PDA@MF sponge through sequential depositions of PDA, CuS nanoparticles, and a PDMS layer onto a melamine sponge. The optimized composite sponge exhibits a superhydrophobic surface property, high absorption capacity for oils, robust recycling, and excellent photothermal conversion performance. Under sunlight irradiation, the sponge can be rapidly heat up for effectively reducing the viscosity of the surrounding crude oil in order to enhance its fluidity. As a result, uptake of crude oil can be achieved continuously at approximately 5.3 g/min using a peristaltic pump. Overall, we believe that a simple fabrication method from low-cost reagents and excellent crude oil remediation performance render the PDMS/CuS/PDA@MF sponge as an excellent sorbent candidate for remediating crude oil spill.

Durable, magnetic-responsive melamine sponge composite for high efficiency,in situoil-water separation.

The development of durable and high-performance absorbents forin situoil-water separation is of critical importance for addressing severe water pollution in daily life as well as for solving accidental large-scale oil spillages. Herein, we demonstrate a simple and scalable approach to fabricate magnetic-responsive superhydrophobic melamine sponges byin situdeposition of PDA coatings and Fe3O4nanoparticles, followed by surface silanization with low surface energy 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PTOS) layer. The prepared melamine sponge composite (PTOS-Fe3O4@PDA/MF) not only exhibits a very high water contact angle of 165 ± 1.5° and an excellent ability to uptake a variety of oils and organic solvents (e.g. up to 141.1 g/g for chloroform), but also shows robust durability and superior recyclability. The PTOS-Fe3O4@PDA/MF sponge can also efficiently separate oils (or organic solvents) and water, as demonstrated by different model systems including immiscible oil-water solution mixture and miscible water-oil (W/O) emulsion (stabilized by surfactants). Furthermore, the PTOS-Fe3O4@PDA/MF sponge is able toin siturecover organics from water using a peristaltic pump, which gives it significant advantages over other traditional batch processes for oil-water separation. We believe that the PTOS-Fe3O4@PDA/MF sponge provides a very promising material solution to address oil-water separation, especially for the large-scale problems that have been long-time challenges with conventional sorption methods.

Molecular Stereocomplexation for Enhancing the Stability of Nanoparticles Encapsulated in Polymeric Micelles for Magnetic Resonance Imaging.

A generalizable approach for improving the stability of polylactide-based (PLA-based) micelles for encapsulating nanoparticles (NPs) is demonstrated, using stereocomplexation between a pair of poly (ethylene glycol)-b-poly(d-lactide)/poly(ethylene glycol)-b-poly(l-lactide) block copolymer blends. Three different superparamagnetic ferrite-based NPs with distinct nanostructures are first prepared by the high-temperature pyrolysis method, including spherical MnFe2O4, cubic MnFe2O4, and core-shell MnFe2O4@Fe3O4. The diameters of these NPs are approximately 7-10 nm as revealed by transmission electron microscopy. These hydrophobic NPs can be encapsulated within self-assembled, stereocomplexed PLA (sc-PLA) micelles. All sc-PLA micelle systems loaded with three different NPs exhibit enhanced stability at elevated temperatures (20-60 °C) and with extended storage time (∼96 h) compared with analogous samples without stereocomplex formation, confirmed by dynamic light scattering measurements. The magnetic NP-loaded micelles with mean diameters of approximately 150 nm show both biocompatibility and superparamagnetic property. Under a 1.5 T magnetic field, cubic MnFe2O4 (c-MnFe2O4)-loaded micelles exhibit an excellent negative contrast enhancement of MR signals (373 mM-1·s-1), while core-shell MnFe2O4@Fe3O4-loaded micelles show a slightly lower signal for MR imaging (275 mM-1·s-1). These results suggest the potential of using sc-PLA-based polymer micelles as universal carriers for magnetic resonance imaging contrast agents with improved stability for different applications such as cancer diagnosis.

Au-Fe3O4 decorated polydopamine hollow nanoparticles as high performance catalysts with magnetic responsive properties.

We demonstrated a simple approach for fabricating Au-Fe3O4/PDA hollow nanoparticles as high-performance catalysts for water purification. The polydopamine (PDA) shell was in situ formed on the silica surface from self-polymerization, which acts as a medium support for coupling with metal ions (for Fe3O4 nanoparticle deposition) as well as a reducing agent and stabilizer for Au nanoparticle reduction and deposition. A step of simultaneous Fe3O4 nanoparticle deposition and silica core removal under alkaline conditions is first introduced in this study. This process significantly simplifies previous strategies which typically require the use of poisonous agents such as hydrogen fluoride or additional complicated post-treatment steps. Under optimized conditions, the Au-Fe3O4/PDA hollow nanoparticles show a high saturation magnetization of 18.8 emu g-1 and an excellent catalytic performance for the rapid reduction of p-nitrophenol with the reaction kinetic constant of 0.34 min-1. This catalyst can be easily recovered using a permanent magnet and recycled eight times with a high catalytic cycle stability. The strategy presented in this work provides a facile and versatile approach towards designing complicated Au-Fe3O4/PDA hollow nanostructures, which might have great potential for many applications within biological, energy, and environmental technologies.

Attack Detection and Approximation in Nonlinear Networked Control Systems Using Neural Networks.

In networked control systems (NCS), a certain class of attacks on the communication network is known to raise traffic flows causing delays and packet losses to increase. This paper presents a novel neural network (NN)-based attack detection and estimation scheme that captures the abnormal traffic flow due to a class of attacks on the communication links within the feedback loop of an NCS. By modeling the unknown network flow as a nonlinear function at the bottleneck node and using a NN observer, the network attack detection residual is defined and utilized to determine the onset of an attack in the communication network when the residual exceeds a predefined threshold. Upon detection, another NN is used to estimate the flow injected by the attack. For the physical system, we develop an attack detection scheme by using an adaptive dynamic programming-based optimal event-triggered NN controller in the presence of network delays and packet losses. Attacks on the network as well as on the sensors of the physical system can be detected and estimated with the proposed scheme. The simulation results confirm theoretical conclusions.

Fabrication of P(NIPAAm-co-AAm) coated optical-magnetic quantum dots/silica core-shell nanocomposites for temperature triggered drug release, bioimaging and in vivo tumor inhibition.

ZnS:Mn2+ quantum dots (QDs) Fe3O4 QDs/SiO2/P(NIPAAm-co-AAm) core-shell-shell nanocomposites have been successfully fabricated by free radical polymerization method. The average diameter and LCST of ZnS:Mn2+ QDs Fe3O4 QDs/SiO2/P(NIPAAm-co-AAm) (NIPAAm:AAm=90:10) nanocomposites was about 200 nm and 41.1°. It possessed a strong yellow-orange emission peak centered at 589 nm from the Mn2+ 4T1-6A1 transition and the desired superparamagnetic property at room temperature. The DOX encapsulation efficiency and loading capacity was 88% and 15.3 wt%, respectively. The nanocomposites showed the faster drug release behavior at 43 °C than that at 25 °C in vitro release experiment, and exhibited no significant cytotoxicity against the HeLa, HepG2 and HEK293 cell lines. Red fluorescence was observed in the cytoplasm of HeLa cells, confirming its application for biolabeling. Effective tumor inhibition was realized in vivo without the induction of toxicity in mice. ZnS:Mn2+ (QDs) Fe3O4 QDs/SiO2/P(NIPAAm-co-AAm) nanocomposites showed the red fluorescence in the cytoplasm of HeLa cells, faster drug release behavior at 43 °C than that at 25 °C in vitro, and effective tumor inhibition in vivo, confirming its application for drug delivery.

Biocompatible ZnS:Mn(2+) quantum dots/SiO2 nanocomposites as fluorescent probe for imaging HeLa cell.

ZnS:Mn(2+) quantum dots (QDs) were successfully embedded in SiO2 spheres by a reverse microemulsion method. The results showed that the monodispersed core/shell nanocomposites were uniform in size, with the majority of the SiO2 nanoparticles containing one QD in the center of the sphere. The shell thickness of SiO2 increased from 7 to 18 nm as the hydrolysis time of TEOS increased from 20 to 40 h. The quantum yield (QY) of the yellow-orange emission (coming from the Mn(2+) ions (4)T1-(6)A1 transition) for the ZnS:Mn(2+)(3 %) QDs and ZnS:Mn(2+)(3 %) QDs@SiO2 (when t = 40 h) nanocomposites was measured to be 34.5 and 22.4 %, respectively. All samples showed no significant cytotoxicity against the HeLa cells even at a high concentration of 500 µg/ml after incubation for 24 h. The red fluorescence can be observed in the cytoplasm of the HeLa cell, further proving its biolabeling applications.

Investigation of composition dependent structural and optical properties of the Zn(1-x)Cd(x)S, coaxial Zn(0.99-x)Cd(x)Cu(0.01)S/ZnS, Zn(0.99-x)Cd(x)Mn(0.01)S nanorods generated by a one-step hydrothermal process.

High-quality Zn(1-x)Cd(x)S, coaxial Zn(0.99-x)Cd(x)Cu(0.01)S/ZnS and Zn(0.99-x)Cd(x)Mn(0.01)S nanorods (NRs) were synthesized through a one-step hydrothermal method. The composition of the alloyed NRs was adjusted by controlling the Zn/Cd molar ratios. The results showed that all of the samples had a good crystallinity with the typical hexagonal wurtzite structure. The Zn/Cd molar ratios and Cu and Mn doping played an important role in affecting the final structure, morphology and optical properties of the alloyed NRs. The successive shift of the XRD and PL patterns indicated that the NRs obtained were not a mixture of ZnS and CdS, but the Zn(1-x)Cd(x)S solid solution. After doping Cu(2+) (1%) ions into the Zn(1-x)Cd(x)S NRs, the samples exhibited highly crystalline coaxial Zn(0.99-x)Cd(x)Cu(0.01)S/ZnS core-shell NRs and showed a strong green emission peak centered at 509.6 nm. After doping Mn(2+) (1%) ions into the Zn(1-x)Cd(x)S NRs, the samples exhibited a better crystal quality and showed a strong yellow-orange emission peak centered at 583 nm.