Janus amphiphilic particles have gained much attention for their important application value in areas as diverse as interfacial modification, sensors, drug delivery, optics, and actuators. In this ...work, we prepared Janus amphiphilic nanosheets composed of nitrogen-doped stratiform meso-macroporous carbons (NMC) and molybdenum sulfide (MoS2) for hydrophilic and hydrophobic sides, respectively. The dicyandiamide and glucose were used as precursors for synthesizing two-dimensional nitrogen-doped meso-macroporous carbons, and the molybdate could be anchored by the functional groups on the surface of carbon layers and then transform into uniformly MoS2 to form the Janus amphiphilic layer by layer NMC/MoS2 support. Transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy are used to demonstrate the successful preparation of Janus materials. As the typical interfacial enzyme, Candida rugosa lipase (CRL) immobilized on the Janus amphiphilic NMC/MoS2 support brought forth to improvement of its performance because the Janus nanosheets can be easily attached on the oil–aqueous interface for better catalytic activity (interfacial activation of lipases). The obtained immobilized lipase (NMC/MoS2@CRL) exhibited satisfactory lipase loading (193.1 mg protein per g), specific hydrolytic activity (95.76 U g–1), thermostability (at 55 °C, 84% of the initial activity remained after 210 min), pH flexibility, and recyclability (60% of the initial activity remained after nine runs). In terms of its application, the esterification rate of using NMC/MoS2@CRL (75%) is higher than those of NMC@CRL (20%) and MoS2@CRL (11.8%) in the “oil–water” biphase and CRL as well as NMC/MoS2@CRL in the one-phase. Comparing with the free CRL, NMC@CRL, and MoS2@CRL, the Janus amphiphilic NMC/MoS2 served as a carrier that exhibited more optimal performance and practicability.
Since the publication of the Age-Related Eye Disease Study 2 (AREDS2) in 2013, the macular pigment carotenoids lutein (L) and zeaxanthin (Z) have become well known to both the eye care community and ...the public. It is a fascinating aspect of evolution that primates have repurposed photoprotective pigments and binding proteins from plants and insects to protect and enhance visual acuity. Moreover, utilization of these plant-derived nutrients has been widely embraced for preventing vision loss from age-related macular degeneration. More recently, there has been growing awareness that these nutrients can also play a role in improving visual performance in adults. On the other hand, the potential benefits of L and Z supplementation at very young ages have been underappreciated. In this review, we examine the biochemical mechanisms and supportive data for L and Z supplementation throughout the lifespan, with particular emphasis on prenatal supplementation. We propose that prenatal nutritional recommendations may aim at improving maternal and infant carotenoid status. Prenatal supplementation with L and Z might enhance infant visual development and performance and may even prevent retinopathy of prematurity, possibilities that should be examined in future clinical studies.
Recycled glass has been demonstrated to be a sustainable alternative for sand in concrete, which can tackle the stockpiling of waste glass and shortage of natural aggregate. However, alkali–silica ...reaction is the major impediment to its wide adoption where more research is required. This paper examined the long-term ASR expansion of mortar containing glass from experimental and numerical analyses. In the experimental study, the effect of glass size (0.15–0.3 mm, 0.3–0.6 mm, 0.6–1.18 mm, 1.18–2.36 mm, 2.36–4.75 mm), glass content (25%, 50%, 75%, 100% by mass) and curing temperature (38 °C, 60 °C 80 °C) were investigated. The accelerated ASR expansion tests were conducted in the elevated temperature and boosted alkali supply. Experimental results showed that the size fraction 1.18–2.36 mm caused the highest ASR expansion, and the size fractions smaller than 0.6–1.18 mm was found to be innocuous. Besides, ASR expansion increased as glass content increased. Furthermore, ASR kinetic was slower and final expansion reduced when temperature decreased. To provide insights into the ASR expansion behaviours, a novel meso-scale chemical-mechanical model was proposed in this study. In the numerical model, the tested specimens were modelled as a three-phase composite including the matrix, glass aggregate and interfacial transition zone. The mechanical and chemical components in the model were calibrated and validated by uniaxial compression and ASR expansion tests. The validated model not only can accurately predict the ASR expansion but also reveal that internal damage became more homogeneous with increasing content of reactive aggregate.
•A combined experimental and numerical study was conducted.•A meso-scale chemical-mechanical model was developed to predict ASR expansion.•Effect of particle size, reactive content and temperature was considered.•Influence of chemical-related parameters was investigated by sensitivity analysis.•Influence of various aggregate properties was investigated by sensitivity analysis.
Benthic faunas and their palaeobiogeographic affinities related to climate gradient can provide insightful information to unravel the tectonic histories of their hosted blocks if they moved across ...different latitude zones. In this study, three different quantitative analyses (network, cluster and non-metric multi-dimensional scaling analyses) are employed to carry out a palaeobiogeographic study of the Kungurian–Roadian brachiopod faunas of the Cimmerian blocks. A spin-glass algorithm that enables network community detection is here used for the first time and its six groups-partition is considered as the optimal solution. Two new palaeobiogeographic subprovinces, the Southern and Northern Cimmerian subprovinces in the Southern Transitional Zone, are first recognised besides the previously perceived Cathaysian, Transhimalayan, Westralian and Austrazean provinces. Based on distinct palaeobiogeographic discrepancies, it is suggested that the Lhasa, Tengchong and Irrawaddy blocks, constituting the main parts of the Southern Cimmerian Subprovince, were probably situated near the peri-Gondwanan region; whereas the South Qiangtang, Baoshan and Sibuma blocks of the Northern Cimmerian Subprovince probably were located in the temperate region of the southern hemisphere during the Cisuralian to Guadalupian transition. Such discrepancies in palaeobiogeographic affinitites between two continental slices imply that the Meso-Tethys Ocean had existed before the late Cisuralian and its present oceanic remnants are represented by the Bangong-Nujiang Suture Zone in central Tibet, the Gaoligongshan shear zone in western Yunnan and the Medial-Myanmar Suture Zone in southern Myanmar and Peninsula Thailand. Moreover, the Neo-Tethys Ocean had likely co-existed with the Meso-Tethys Ocean during that time. Given that all these blocks were attached to the northern peri-Gondwanan margin during the early Cisuralian, the Kungurian-Roadian faunal discrepancies among different continental slices with a distinct latitude gradient can be interpreted by the allometric northward drifting of the Cimmerian blocks, which led to the formation of the Meso-Tethys and Neo-Tethys oceans.
•A spin-glass algorithm for network community detection is applied for the first time in a palaeobiogeographic analysis.•The Southern and Northern Cimmerian subprovinces are first identified in the Tethys during the Kungurian–Roadian.•The Meso-Tethys Ocean had opened before late Cisuralian due to allometric northward drifting of the Cimmerian blocks.
To achieve more accurate prediction of the potential failure location and to conduct a deeper analysis of the failure mechanism of concrete constructions, it is critical to probe the evolution ...process of internal meso-cracks that bear various intensities of load. While a computer Tomography (CT) test provides a non-destructive detection technique for obtaining the internal meso-damage state of concrete, traditional image processing and Digital Image Correlation (DIC) are ineffective in extracting meso-damage information from concrete CT images. On the other hand, by observing the shape change law of concrete’s internal holes under load, it is proposed to use the hole roundness and area fraction formula, developed based on the stereology principle and morphology, to characterize and predict the potential failure location. Four features particularly addressed include the CT image as a whole, image equal partitioning, crack and non-crack areas, and representative holes. The approach is to explore the variation law of critical hole shape parameters, especially the hole roundness under different loading stages, and analyze the relationship between the change in hole shapes and the final macro-crack positions. It is found that compared with the average area fraction, the average hole roundness value of cross section images is more sensitive to the change in stress. In both uniform partitioning and non-uniform partitioning, the average hole roundness value near the final macro-crack location exhibits an increase trend with the stress, while the smoothing effect caused by the hole roundness averaging always exists. Near the final macro-crack location, the roundness of each individual hole is positively associated with the stress, while away from the final macro-crack location such a relation may not be observed. This trend expounds the evolution process of meso-damage in concrete, and the finding can be used to predict the accurate locations of macro-cracks.
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•Hierarchical meso/macroporous BN fibers were prepared using luffa sponge as a template.•The BN fibers exhibited remarkable adsorption performance for different heavy metal ions.•The ...adsorption capability for Cd2+ (2989 mg/g) and Zn2+ (1885 mg/g) exceed the highest values reported for BN materials.
Boron nitride (BN) has received tremendous attention as a promising adsorbent material. However, unsatisfactory uptake capacities over heavy metal ions limit their practical applications. Herein, we have synthesized a novel hierarchical meso/macroporous BN fibers (MBNFs) via a simple carbothermal reduction method using luffa sponge as a template. The as-obtained MBNFs comprise densely arranged parallel macrochannels on a micrometer scale, with mesopores on the surface of the channel. The resulting MBNFs exhibited remarkable adsorption performance for different heavy metal ions including Cd2+, Zn2+, Cr3+, and Pb2+ with maximum uptake capacities as high as 2989, 1885, 723, and 453 mg/g, respectively. In particular, the adsorption capacity for Cd2+ and Zn2+ exceed the highest values reported for BN materials. In addition, the MBNFs showed excellent stability to re-use for a few times. The present MBNFs materials prepared using cheap and earth abundant luffa sponge may find broad applications such as adsorbent for environmental remediation applications.
Porphyrin derivatives are widely used as donors in organic solar cells (OSCs) due to their excellent optical and electrochemical properties. Although porphyrins can be functionalized at the meso‐ and ...β‐positions, only meso‐functionalized porphyrins have been reported as OSCs. Consequently, a direct comparison of the properties of porphyrins functionalized at these two positions is needed. The synthesis of two similar D–π–A–π–D materials is described herein and these compounds contain benzothiadiazole as the acceptor core and two Ni‐porphyrins as donors functionalized at the meso‐ and β‐positions to give RC19 and RC20, respectively. The optical and electrochemical properties of these compounds are reported. All‐small‐molecule OSCs based on RC19:TOCR1 and RC20:TOCR1 active layers show power conversion efficiencies (PCEs) of 13.72% and 5.20%, respectively. It should be noted that the PCE of 13.72% obtained for RC19:TOCR1 devices is, to one's knowledge, the highest value reported for porphyrin‐based binary OSCs. The higher PCE obtained for RC19 is due to its higher photon harvesting ability, more efficient exciton dissociation and charge transfer, balanced charge transport, and lower bimolecular and trap‐assisted recombination.
Two D–π–A–π–D materials, RC19 and RC20, with benzothiadiazole as the acceptor core and meso‐ or β‐functionalized Ni‐porphyrins, are synthesized and studied in organic solar cell devices. RC19:TOCR1 exhibits a remarkable 13.72% power conversion efficiency, the highest reported for porphyrin‐based binary organic solar cells. This achievement results from enhanced photon harvesting, efficient exciton dissociation, balanced charge transport, and reduced recombination in RC19‐based organic solar cell.
We developed a chiral symmetry breaking method for monoacylated meso diols. The X‐ray crystal structure analysis of monoacylated 1,4‐anhydroerythritols, meso cyclic diols with a cis configuration, ...revealed that the O‐(p‐anisoyl) derivative crystallized as a racemic conglomerate of the P212121 crystal system. It was confirmed that the substrate racemized by intramolecular transfer of the acyl group in the presence of a catalytic amount of base. Evaporating the solvent gradually from the solution or Viedma ripening to promote crystallization‐induced deracemization efficiently led to enantiomer crystals. These results provide the first successful example of asymmetric expression and amplification by deracemization of sugar derivatives without an external chemical chiral source. Furthermore, we applied this methodology to acyclic meso‐1,2‐diols. Three O‐monoacylated substrates were successfully deracemized to 99 % ee by Viedma ripening. We also developed asymmetric desymmetrization of meso‐1,2‐diols by combining acylation and crystallization‐induced deracemization.
The X‐ray crystal structure analysis of monoacylated 1,4‐anhydroerythritols and acyclic meso‐1,2‐diols with a cis configuration revealed that four compounds crystallized as a racemic conglomerate. All compounds racemized by intramolecular transfer of the acyl group in the presence of a catalytic amount of base. Crystallization‐induced deracemization efficiently led to enantiomer crystals of 99 % ee.
Expansive soils located in permafrost and seasonal frozen regions can easily suffer from the action of frost heaving and repeated freezing–thawing. When exposed to freeze–thaw (F–T) cycles, it may ...pose risk to civil engineering structures and thus causes heavy economic losses. In this study, a series of cylindrical expansive soil specimens were compacted at three different molding water contents (15%, 20% and 23%) and then subjected to a maximum of 12 closed–system F–T cycles. Besides, selected specimens compacted at the optimum water content were also tested under cyclic freezing–thawing with varying freezing temperatures (−5 °C, −10 °C and −20 °C). After each cycle of F–T, volume changes were measured and unconfined compression testing was also performed to estimate stress–strain behavior, resilient modulus and failure strength. Moreover, meso–structural analysis was conducted by using a simple optical test system to quantitatively extract the surface porosity and the pore orientation degree of expansive soil specimens after different F–T cycles. It is found that: 1) Volume changes for expansive soil specimens with higher and lower saturations present opposite directions and different magnitudes upon freezing, but show a similar trend of volume expansion after thawing. A moderate freezing temperature (i.e. –10 °C, in this study) has the greatest effect on volume changes. 2) Expansive soils tend to exhibit strain–softening behavior under unconfined compression conditions. The resilient modulus and failure strength decrease significantly at the first cycle of F–T and then reduce gradually to a stable value with increasing F–T cycles. The higher molding water content and a moderate freezing temperature will lead to a more pronounced degradation of mechanical behaviors with the F–T cycles. 3) It is suggested from the meso–structural analysis that the internal pores of expansive soils after a sequence of F–T cycles tend to become larger and more uniform, especially for the soil with higher water contents or experienced at a moderate freezing temperature.
•Volume changes and mechanical behavior at different water contents and freezing temperatures were investigated.•Freezing-induced volume changes is interpreted from the perspective of the inter- and intra-aggregate pores interaction.•Mechanical degradation upon F-T cycles are evident in higher water contents and a moderate freezing temperature.•Porosity and pore orientation of internal pores change upon F-T cycles.
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