Poly(ethylene glycol)-interpenetrated genipin-crosslinked chitosan hydrogels: Structure,pH responsiveness,gelation kinetics,and rheology

In the development of pH-responsive chitosan-based hydrogels, achieving reproducible porosity and swelling behavior is essential for the design of hydrogel networks. Herein, we enhance the level of control in hydrogel microarchitecture by incorporating poly(ethylene glycol) (PEG) into the chitosan–genipin matrix. Hydrogels, varied in composition, were synthesized under mild conditions (37°C, 1 atm, 24 hr), yielding microporous structures with a pore diameter ranging from 11 to 57 μm and an average cross-sectional porosity of approximately 40–64%. Compared to chitosan–genipin hydrogels without PEG, presence of PEG in concentrations up to 1.9 mM generated the same effect as would increase in genipin content, yielding structures with a smaller pore diameter, a lower swelling degree in pH 2 buffer and a higher elastic modulus. Considering cost effectiveness and scale-up, reducing genipin content by the addition of PEG is favorable. Importantly, hydrogel samples containing higher concentrations of PEG (2.9 mM and above) showed a sudden increase in the swelling degree accompanied with a decrease in the elastic modulus. Findings showcase the potential variation in the composition of these hydrogels has in yielding scaffolds with significantly different physico-chemical behaviors.     

The effect of postharvest 1-MCP treatment and storage atmosphere on ‘Cripps Pink’ apple phenolics and antioxidant activity

This study investigated the effect of a postharvest 1-methylcyclopropene (1-MCP) treatment, controlled atmosphere and storage time on the total antioxidant activity (TAA) and phenolic compounds in the peel and flesh of ‘Cripps Pink’ apples (Malus domestica Borkh.). Preclimacteric apples were harvested and treated with 1-MCP then stored in normal atmosphere (NA) or controlled atmosphere (CA) at 0 °C for up to 160 days. In general, the level of phenolics decreased by 9% in the peel and significantly increased twofold in the flesh during cold storage, regardless of storage atmosphere or 1-MCP treatment. However, treatment with 1-MCP resulted in significantly lower concentrations of chlorogenic acid and procyanidin B2 in apple flesh, and catechin and epicatechin in the peel compared to the control fruits. There was no significant effect of CA on the phenolic compounds during long-term storage, except for quercetin 3-galactoside and quercetin 3-glucoside, which both significantly increased under CA storage. Total antioxidant activity (TAA) is an important nutritional attribute of apples in the human diet. The results showed that TAA in the peel tissue was about eight times higher than that of the flesh, with mean values of 4.75 g TE/kg FW and 0.56 TE/kg FW, respectively. The TAA in both the peel and flesh tissue increased significantly during storage by 40% and 70%, respectively. The storage atmosphere did not significantly affect TAA in either the peel or flesh, whilst the 1-MCP treatment significantly reduced the TAA in the peel tissue only. These results show the beneficial combined effects of pre-storage 1-MCP treatment and CA on ‘Cripps Pink’ apple phenolic composition and antioxidant capacity during long term storage.     

Ebola Entry Inhibitors Discovered from Maesa perlarius

Ebola virus disease (EVD), a disease caused by infection with Ebola virus (EBOV), is characterized by hemorrhagic fever and a high case fatality rate. With limited options for the treatment of EVD, anti-Ebola viral therapeutics need to be urgently developed. In this study, over 500 extracts of medicinal plants collected in the Lingnan region were tested against infection with Ebola-virus-pseudotyped particles (EBOVpp), leading to the discovery of Maesa perlarius as an anti-EBOV plant lead. The methanol extract (MPBE) of the stems of this plant showed an inhibitory effect against EBOVpp, with an IC₅₀ value of 0.52 µg/mL, which was confirmed by testing the extract against infectious EBOV in a biosafety level 4 laboratory. The bioassay-guided fractionation of MPBE resulted in three proanthocyanidins (procyanidin B2 (1), procyanidin C1 (2), and epicatechin-(4β→8)-epicatechin-(4β→8)-epicatechin-(4β→8)-epicatechin (3)), along with two flavan-3-ols ((+)-catechin (4) and (−)-epicatechin (5)). The IC₅₀ values of the compounds against pseudovirion-bearing EBOV-GP ranged from 0.83 to 36.0 µM, with 1 as the most potent inhibitor. The anti-EBOV activities of five synthetic derivatives together with six commercially available analogues, including EGCG ((−)-epigallocatechin-3-O-gallate (8)), were further investigated. Molecular docking analysis and binding affinity measurement suggested the EBOV glycoprotein could be a potential molecular target for 1 and its related compounds.     

Estimating aboveground biomass of a mangrove plantation on the Northern coast of Vietnam using machine learning techniques with an integration of ALOS-2 PALSAR-2 and Sentinel-2A data

ABSTRACT

Aboveground biomass (AGB) of mangrove forest plays a crucial role in global carbon cycle by reducing greenhouse gas emissions and mitigating climate change impacts. Monitoring mangrove forests biomass accurately still remains challenging compared to other forest ecosystems. We investigated the usability of machine learning techniques for the estimation of AGB of mangrove plantation at a coastal area of Hai Phong city (Vietnam). The study employed a GIS database and support vector regression (SVR) to build and verify a model of AGB, drawing upon data from a survey in 25 sampling plots and an integration of Advanced Land Observing Satellite-2 Phased Array Type L-band Synthetic Aperture Radar-2 (ALOS-2 PALSAR-2) dual-polarization horizontal transmitting and horizontal receiving (HH) and horizontal transmitting and vertical receiving (HV) and Sentinel-2A multispectral data. The performance of the model was assessed using root mean square error (RMSE), mean absolute error (MAE), coefficient of determination (R²), and leave-one-out cross-validation. Usability of the SVR model was assessed by comparing with four state-of-the-art machine learning techniques, i.e. radial basis function neural networks, multi-layer perceptron neural networks, Gaussian process, and random forest. The SVR model shows a satisfactory result (R² = 0.596, RMSE = 0.187, MAE = 0.123) and outperforms the four machine learning models. The SVR model-estimated AGB ranged between 36.22 and 230.14 Mg ha^?1 (average = 87.67 Mg ha^?1). We conclude that an integration of ALOS-2 PALSAR-2 and Sentinel-2A data used with SVR model can improve the AGB accuracy estimation of mangrove plantations in tropical areas.     

Covalent functionalization of silica nanoparticles with poly(N-isopropylacrylamide) employing thiol-ene chemistry and activator regenerated by electron transfer ATRP protocol

A facile method has been developed for the synthesis of core–shell nanostructure poly(N-isopropylacrylamide) grafted on silica nanoparticles (SiO₂ NPs) by using the combination of ARGET ATRP and thiol-ene click chemistry. The covalent attachment of the thermo-responsive polymer was achieved by taking advantage of the fast, robust, and high efficient thiol-ene click reaction as demonstrated by FT-IR and XPS. The ARGET ATRP provides the good conversion of the monomer in a well-controlled manner as indicated by the narrow value of PDI (1.21). The grafting amount of the polymer on SiO₂ NPs was found to be ca. 18 % as determined by TGA technique. TEM images of the encapsulated SiO₂ NPs suggested that the SiO₂ NPs core was covered by the soft polymer layer. Interestingly, dynamic light scattering analysis revealed that the as-synthesized nanocomposites exhibited the thermo-responsive behavior with the transition temperature around 31–33 °C.     

Thermomagnetic fluctuations and hysteresis loops of magnetic cantilevers for magnetic resonance force microscopy

We have used frequency-shift cantilever magnetometry to study individual nickel magnets patterned at the end of ultra-sensitive silicon cantilevers for use in magnetic resonance force microscopy (MRFM). We present a procedure for inferring a magnet's full hysteresis curve from the response of cantilever resonance frequency versus magnetic field. Hysteresis loops and small-angle fluctuations were determined at 4.2 K with an applied magnetic field up to 6 T for magnets covering a range of dimensions and aspect ratios. Compared to magnetic materials with higher anisotropy, we find that nickel is preferable for MRFM experiments on nuclear spins at high magnetic fields.     

Photoresist coating methods for the integration of novel 3-D RF microstructures

This paper presents three coating methods of photoresist on large three-dimensional (3-D) topography surfaces. Two special methods, spray and electrodeposition (ED) are introduced and investigated for the fabrication of 3-D microstructures and RF-MEMS devices. Characteristics of each method as well as its advantage and disadvantages are outlined. A comparison is made to point out the most suitable coating method in terms of complexity, performance and type of application. The potential of these coating methods is demonstrated through several applications such as fabrication of multilevel micromachined structures and RF MEMS devices.