Search

The Scale Invariant Feature Transform (SIFT) algorithm is utilized broadly in image registration to improve image qualities. However, the algorithm’s complexity reduces its efficiency in biology study and usually requires real-time. In this article, we present an improved SIFT technique in software architecture for matching sequences of images taken from a line-scanning ophthalmoscope (LSO). The method generates the Gaussian Scale-space pyramid in frequency domain to complete the SIFT feature detector more quickly. A novel SIFT descriptor invariable with rotation and illumination is then created to reduce calculation time, implementing the original SIFT method, our improved SIFT method, and the graphic processing unit (GPU) version of our improved SIFT method. The experiments have shown that the improved SIFT is almost 2–3 times faster than the original while maintaining more robust performance, and the GPU implementation of the improved SIFT is 20 times faster than central processing unit (CPU) implementation and achieves acceleration at real-time as expected. Although tested on an LSO system, the improved SIFT method does not rely on the acquisition setup. As a result, this method can be applied to other imaging instruments, e.g., adaptive optics to increase their resolution in agreement. [ABSTRACT FROM AUTHOR]

Abstract: Synthesis of a novel amphiphilic polymer brush with a sequence of alternating poly(ɛ-caprolactone) (PCL) and poly(ethylene oxide) (PEO) side chains through grafting-through approach is reported. This strategy consists of two steps: first, a PCL macromonomer carrying maleimide functional group (MI-PCL) and a PEO macromonomer with vinylbenzyl group (St-PEO) were prepared; then a conventional radical copolymerization of the MI-PCL and the St-PEO macromonomers was carried out to obtain the proto-type polymer brush. The reactivity ratios of two macromonomers were studied and the alternating sequence structure was proved. [Copyright &y& Elsevier]

Abstract: ABC-type miktoarm star polymers, poly(ethylene oxide)-block-polystyrene-block-poly (ε-caprolactone)s (PEO-b-PS-b-PCL) were synthesized via combination of “click” chemistry, atom-transfer radical polymerization (ATRP) and ring opening polymerization (ROP). Azide ended PEO arms, PEO–N3, and a trifunctional molecule, propargyl 2-hydroxylmethyl-2-(α-bromoisobutyraloxymethyl)-propionate (PHBP), were prepared first, respectively. A “click” reaction of PEO–N3 and PHBP generated a PEO macroinitiator, PEO–(Br)(OH) with two functionalities, one is hydroxyl group and the other is α-bromoisobutyraloxyl group. Consecutive ATRP of styrene (St) and ROP of ε-caprolactone (ε-CL) from the PEO macroinitiator produced the PEO-b-PS-b-PCL miktoarm stars. All the structures of the polymers were determined. [Copyright &y& Elsevier]

Abstract: A pragmatic one-pot approach to the synthesis of star polymers is reported using atom transfer radical copolymerization (ATRcP) of a bismaleimide and an excess of styrene (St) initiated with a conventional ATRP initiator. [Copyright &y& Elsevier]

Abstract: Versatile miktoarm three-arm star polymers, (polystyrene)(polyε-caprolactone)2 ((PS)(PCL)2), (PS-b-poly(n-butyl acrylate))(PCL-b-PS-b-poly(n-butyl acrylate))2 ((PS-b-PnBA)(PCL-b-PS-b-PnBA)2) and (PtBA-b-PS)(PCL-b-PtBA-b-PS)2 were synthesized via combination of atom-transfer radical polymerization (ATRP), functional group transformation technique and ring opening polymerization (ROP) using 1,1-dihydroxymethyl-1-(2-bromoisobutyryloxy)methyl ethane (DHB) as a heterofunctional initiator. In the synthesis of (PS)(PCL)2 by combination of ROP of ε-caprolactone (ε-CL) and ATRP, the implementation sequence, ROP followed by ATRP, was proved to be effective to get a well-defined miktoarm star polymer than the reverse one. The two miktoarm star block polymers, (PS-b-PnBA)(PCL-b-PS-b-PnBA)2 and (PtBA-b-PS)(PCL-b-PtBA-b-PS)2, were prepared by one ROP step, one group transformation and ATRP steps using the same initiator. All the polymers have defined structures and their molecular weights are adjustable with good controllability. [Copyright &y& Elsevier]

• Ducks play a key role in the maintenance and spread of avian influenza viruses. • A bivalent vaccine (rDEVus78HA) protect ducks against lethal challenge with DEV and H5N1 virus in a 60-week clinical trial. • rDEVus78HA induce broader protection against heterologous and antigenically drifted H5 influenza viruses. Ducks play a key role in the maintenance and spread of avian influenza viruses (AIVs) in nature, and control of AIVs in ducks has important implications for AIV eradication from poultry. We previously constructed a recombinant duck enteritis virus (DEV), rDEVus78HA, that expresses the HA gene of an H5N1 AIV and showed that rDEVus78HA immunization provides complete protection against both DEV and H5N1 AIV challenge in specific-pathogen-free ducks. In this study, we performed a 60-week clinical trial and found that this rDEVus78HA vaccine can function as a bivalent vaccine in farmed ducks against lethal challenge with DEV and H5N1 virus. Moreover, we found that rDEVus78HA-vaccinated ducks were efficiently protected against challenges with recently isolated heterologous H5N6 and H5N8 viruses. Our results demonstrate that rDEVus78HA could be extremely valuable for the control of DEV and H5 AIVs in ducks. [ABSTRACT FROM AUTHOR]

Binding exclusively to human-type receptors is a prerequisite for avian influenza viruses to transmit from human to human. We previously reported that 34% of H6 avian influenza viruses recognize the human-type receptor, but their affinity for the avian-type receptor remains higher than that for the human-type receptor. Here, we found that a single amino acid change from glutamine to leucine at position 226 of hemagglutinin caused a switch in receptor-binding preference from avian-type to human-type receptors and rendered A/chicken/Guangdong/S1312/2010(H6N2) capable of respiratory droplet transmission in guinea pigs. [ABSTRACT FROM AUTHOR]

A PDMS elastomer based on acylhydrazone groups with both acid- and heat-assisted self-healing properties was successfully prepared from tetra-acylhydrazine-terminated PDMS and terephthalaldehyde through solution casting. The good healing performance was obtained with catalytic acetic acid for 24 h at 25 °C or by annealing at 120 °C for 2 h. The elastomer exhibited a reversible transition near 80 °C observed by rheological measurements and variable-temperature FTIR, which corresponded to the dissociation and reconstruction of hydrogen bonds between acylhydrazone groups. Since the non-equimolar sample presented similar behaviors with the equimolar sample, it verifies that the reversible dissociation/reformation of hydrogen bonds dominates the heat-assisted self-healing process. This finding will enable better understanding of the contribution of hydrogen bonding interactions in acylhydrazone self-healing systems, thus promoting the development of self-healing bulk materials based on acylhydrazone groups. [ABSTRACT FROM AUTHOR]

There is concern regarding the long-term vibration effects caused by metro trains on historic buildings. In this paper, the impact of metro train-induced vibrations on the Bell Tower in Xi’an above two spatially overlapping tunnels was studied. Metro Line 2 has been operational since 2011, and Line 6 is still under construction. To study and control the effect of micro vibrations on the Bell Tower, a metro train–track–tunnel–soil 3D dynamic FE model was developed. The vibration response generated by Line 2 was then predicted, and the influences of train speed on ground vibration were analysed. In addition, a detailed in situ measurement, which helped calibrate the numerical model and determine the dynamic behaviour of timber structures, was performed. Finally, the calibrated models and measured results were used to predict vibrations caused by road traffic and trains from two spatially overlapping metro lines. This was performed under different route schemes and train operation conditions. The results showed that installing steel spring floating slab tracks (FST) and decreasing train speeds had obvious effects on controlling the ground peak particle velocity (PPV). Simulated results from both the input impulse and output response generated by metro Line 2 matched well with actual measurements. If correct designs are employed, it is possible to resolve the vibration problem on historic buildings caused by metro trains. [ABSTRACT FROM AUTHOR]

Wild birds are the natural reservoirs of avian influenza viruses, and surveillance and assessment of these viruses in wild birds provide valuable information for early warning and control of animal diseases. In this study, we isolated 19 H7N7 avian influenza viruses from wild bird between 2018 and 2020. Full genomic analysis revealed that these viruses bear a single basic amino acid in the cleavage site of their hemagglutinin gene, and formed four different genotypes by actively reassorting other avian influenza viruses circulating in wild birds and ducks. The H7N7 viruses bound to both avian-type and human-type receptors, although their affinity for human-type receptors was markedly lower than that for avian-type receptors. Moreover, we found that the H7N7 viruses could replicate efficiently in the upper respiratory tract and caecum of domestic ducks, and that the H5/H7 inactivated vaccine used in poultry in China provided complete protection against H7N7 wild bird virus challenge in ducks. Our findings demonstrate that wild bird H7N7 viruses pose a substantial threat to the poultry industry across the East Asian-Australian migratory flyway, emphasize the importance of influenza virus surveillance in both wild and domestic birds, and support the development of active control strategies against H7N7 virus. [ABSTRACT FROM AUTHOR]

Abstract: Dynamic polystyrene (d-PS) and poly(n-butyl acrylate) (d-PBA) with an acylhydrazone linkage at each chain center were synthesized by atom transfer radical polymerization (ATRP) of corresponding monomers using a bis-bromoisobutyrate initiator bearing one acylhydrazone bond. Kinetic studies demonstrated that the polymerization followed a first-order mechanism. When treated with trifluoroacetic acid or heated at 120 °C in solution, the polymer chains of d-PS and d-PBA were found to be cleaved partially into blocks of half original length, i.e. PS/2 and PBA/2, implying that a dynamic equilibrium of forming and breaking acylhydrazone bond was established. [Copyright &y& Elsevier]

Abstract: Crystallization kinetics and behavior of PCL side chains in polymer co-brushes constituted with PCL and PEO side chains alternatively attached on poly(styrene-alt-maleimide) backbones have been determined using in-situ FT-IR and DSC methods. Avrami analysis shows the exponent n increasing from one at 10 °C to two at 30 °C, demonstrating confined crystallization of PCL side chains through homogeneous or heterogeneous nucleation. PLM morphological characterization displays typical spherulites of which size is dependent on the crystallization temperature and further AFM visualization shows typical PCL lamellae at 30 °C and broken lamellae at 10 °C embedded within PEO + backbone matrix inside of spherulites. Such lamellar structure explains the confined crystallization with Avrami exponent n ≤ 2. Formation of the broken lamellae can further clarify the reason why Avrami exponent decreases to n ≈ 1 at 10 °C, that is, homogeneous nucleation in the isolated crystals. Dynamically confined crystallization has been proposed based on their special molecular architecture. Comparing to statically confined crystallization, the construction of confined space and the crystallization process were almost synchronous. The formation of spherulites mesoscopically reveals the entire molecule motion and assembly through a pathway of conventional crystalline polymers and the crystallization of PCL side chains in a space constituted by stiff backbones of poly(styrene-alt-maleimide) plus soft PEO layer microscopically reflects a confined character which has been observed in some conventional block copolymers. [Copyright &y& Elsevier]