Preparation of highly conductive reduced graphite oxide/poly(styrene-co-butyl acrylate) composites via miniemulsion polymerization

Polymer/reduced graphite oxide (rGO) composite nanoparticles with a high electrical conductivity were synthesized using the miniemulsion polymerization technique. The rGO was modified with a reactive surfactant, 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), to facilitate monomer intercalation into the rGO nanogalleries. The AMPS-modified rGO was emulsified in the presence of styrene (St) and butyl acrylate (BA) monomers, and the stable miniemulsion was polymerized to form poly(St-co-BA)/rGO composite latex nanoparticles. The transition in the composite nanoparticles from an electrical insulator to an electrical conductor occurred at an rGO content of 10 wt% (relative to the monolayer content), yielding an electrical conductivity of 0.49 S/cm. The electrical conductivity of the composite nanoparticles reached 2.22 S/cm at 20 wt% rGO, yielding a much better conductivity than other polymer composites prepared using a GO filler. Importantly, the miniemulsion polymerization method for fabricating poly(St-co-BA)/rGO composite nanoparticles is easy, green, low-cost, and scalable, providing a universal route to the rational design and engineering of highly conductive polymer composites.     

Antiplasticization behavior of polycaprolactone/polycarbonate-modified epoxies

Antiplasticization behavior was found in the polycaprolactone (PCL)/polycarbonate (PC)-modified epoxy system, cured with an aromatic amine. The initial modulus increased and the fracture toughness and the elongation at break decreased with the addition of the PCL/PC modifier. The glass transition temperature (T_g) decreased slightly. In this system, the antiplasticization phenomenon can be explained well by the formation of hydrogen bonding between the carbonyl groups in the PCL/PC and the hydroxyl groups in the epoxy. The hydrogen bonding proportion, as analyzed from Fourier transform infrared spectra, increased with the addition of PCL/PC up to 15 parts. This is consistent with the trend observed in the mechanical properties. It was thought that for antiplasticization to occur, a strong molecular interaction is necessary for a restriction of molecular motion, in turn decreasing the free volume of the matrix and thereby causing an increase in the modulus of the material. The dynamic mechanical thermal behavior of these systems was also studied. It was found that there was no change in the molecular weights between crosslinks, which excluded the effect of crosslink density on the changes of the properties. Instead, the activation energy was increased and the peak area was decreased for the β relaxation because of the restriction of the molecular motion by hydrogen bonding. The results indirectly support the hypothesis that the motion of the 2-hydroxypropyl ether is responsible for the β relaxation process.     

Comparison of solvent performance for CO2 capture from coal-derived flue gas: A pilot scale study

The performance of a proprietary solvent (CAER-B2), an amine-carbonate blend, for the absorption of CO₂ from coal-derived flue gas is evaluated and compared with state-of-the-art 30 wt% monoethanolamine (MEA) under similar experimental conditions in a 0.1 MWth pilot plant. The evaluation was done by comparing the carbon capture efficiency, the overall mass transfer rates, and the energy of regeneration of the solvents. For similar carbon loadings of the solvents in the scrubber, comparable mass transfer rates were obtained. The rich loading obtained for the blend was 0.50 mol CO₂/mol amine compared to 0.44 mol CO₂/mol amine for MEA. The energy of regeneration for the blend was about 10% lower than that of 30 wt% MEA. At optimum conditions, the blend shows promise in reducing the energy penalty associated with using industry standard, MEA, as a solvent for CO₂ capture.     

黄河小浪底工程泥沙问题的研究

本文系统地研究了原型沙和模型沙（电木粉）的基本运动特性。首次提出了可应用于高含沙水流模型试验的相似关系，据此理论建造了黄河小浪底枢纽１:８０的正态泥沙模型。研究了小浪底工程不同运用阶段的泥沙问题。同时，还重点研究了高含沙异重流和泄水建筑物的防淤堵问题。     

Correlation between anisotropic bending stiffness of GDL and land/channel width ratio of polymer electrolyte membrane fuel cells

A correlation between anisotropic bending stiffness of a gas diffusion layer (GDL) and land/channel width ratios of metallic bipolar plates (MBPs) in polymer electrolyte membrane fuel cells has been systematically investigated. I–V performances of the fuel cells with 90° GDLs, whose directions of higher stiffness are perpendicular to the direction of the major flow field, are generally higher than those with 0° GDLs, whose directions of higher stiffness are parallel with the direction of the major flow field. However, the differences of I–V performances and high-frequency resistance values between 0° and 90° GDL cells gradually decrease with increasing land/channel width ratio, because of the reduced anisotropic stiffness effects of the GDLs due to the better support by the MBPs with wider lands. The cross-sectional images of GDLs upon compression indicate that the 0° GDL appears to be more deformed and intruded into channel than the 90° GDL under the narrowest lands, whereas both 0° and 90° GDLs show very little intrusion and deformation under the widest lands. The results clearly explain why some MBPs (i.e., narrower lands) exhibit strong effects of GDL’s anisotropic stiffness on cell performances, whereas other MBPs (i.e., wider lands) do not experience such effects.     

Experimental study on mitigating the cathode flooding at low temperature by adding hydrogen to the cathode reactant gas in PEM fuel cell

Severe flooding can be critical in a fuel cell vehicle operating at a high current density, and in a fuel cell vehicle at the initial stage of start up. It is often difficult to remove the condensed water from the cathode gas diffusion layer (GDL) of the fuel cell because of the surface tension between the water and the GDL. In this research, in order to remove the condensed water from the cathode GDL, a small amount of hydrogen was injected into the cathode reactant gases. The results showed that the hydrogen addition method successfully removed the liquid water from the cathode GDL. Water removal was verified for various hydrogen flow rates and hydrogen addition durations. Furthermore, the dew point temperature of the outlet gas at the cathode was observed to determine the amount of water removed from the cathode GDL. In addition, the water droplet in the cathode gas flow channel was visualized by using a transparent cell. Furthermore, degradation tests are also performed. Considering the degradation test, the hydrogen addition method is expected to be effective in mitigating cathode flooding.     

Physicochemical and retrogradation properties of modified chestnut starches

Food Science and Biotechnology - Physicochemical properties of acetylated (AC), cross-linked (CL), and hydroxypropylated (HP) chestnut starches were investigated. Modified chestnut starch showed...     

Supramolecular Assembly of Aminoethylene‐Lipopeptide PMO Conjugates into RNA Splice‐Switching Nanomicelles

Phosphorodiamidate morpholino oligomers (PMOs) are oligonucleotide analogs that can be used for therapeutic modulation of pre‐mRNA splicing. Similar to other classes of nucleic acid‐based therapeutics, PMOs require delivery systems for efficient transport to the intracellular target sites. Here, artificial peptides based on the oligo(ethylenamino) acid succinyl‐tetraethylenpentamine (Stp), hydrophobic modifications, and an azide group are presented, which are used for strain‐promoted azide‐alkyne cycloaddition conjugation with splice‐switching PMOs. By systematically varying the lead structure and formulation, it is determined that the type of contained fatty acid and supramolecular assembly have a critical impact on the delivery efficacy. A compound containing linolenic acid with three cis double bonds exhibits the highest splice‐switching activity and significantly increases functional protein expression in pLuc/705 reporter cells in vitro and after local administration in vivo. Structural and mechanistic studies reveal that the lipopeptide PMO conjugates form nanoparticles, which accelerate cellular uptake and that the content of unsaturated fatty acids enhances endosomal escape. In an in vitro Duchenne muscular dystrophy exon skipping model using H2K‐mdx52 dystrophic skeletal myotubes, the highly potent PMO conjugates mediate significant splice‐switching at very low nanomolar concentrations. The presented aminoethylene‐lipopeptides are thus a promising platform for the generation of PMO‐therapeutics with a favorable activity/toxicity profile.     

Super-Resolution Reconstruction of Images Based on Microarray Camera

In the field of images and imaging, super-resolution (SR) reconstruction of images is a technique that converts one or more low-resolution (LR) images into a highresolution (HR) image. The classical two types of SR methods are mainly based on applying a single image or multiple images captured by a single camera. Microarray camera has the characteristics of small size, multi views, and the possibility of applying to portable devices. It has become a research hotspot in image processing. In this paper, we propose a SR reconstruction of images based on a microarray camera for sharpening and registration processing of array images. The array images are interpolated to obtain a HR image initially followed by a convolution neural network (CNN) procedure for enhancement. The convolution layers of our convolution neural network are 3×3 or 1×1 layers, of which the 1×1 layers are used to improve the network performance particularly. A bottleneck structure is applied to reduce the parameter numbers of the nonlinear mapping and to improve the nonlinear capability of the whole network. Finally, we use a 3×3 deconvolution layer to significantly reduce the number of parameters compared to the deconvolution layer of FSRCNN-s. The experiments show that the proposed method can not only ameliorate effectively the texture quality of the target image based on the array images information, but also further enhance the quality of the initial high resolution image by the improved CNN.