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The aggregation of graphene oxide (GO) is considered as main challenge, although GO possesses excellent mechanical properties which arouses widespread attention as reinforcement for ...polymers.
In this study, silicon dioxide (SiO2) nanoparticles were decorated onto surface of GO nanosheets through in situ growth method for promoting dispersion of GO in poly(l-lactic acid) (PLLA) bone scaffold.
Hydroxyl and carboxyl functional groups of GO provided sites for SiO2 nucleation, and SiO2 grew with hydrolysis and polycondensation of tetraethyl orthosilicate (TEOS) and finally formed nanoparticles onto surface of GO with covalent bonds. Then, the GO@ SiO2 nanocomposite was blended with PLLA for the fabrication of bone scaffold by selective laser sintering (SLS).
The results indicated that the obtained SiO2 were distributed relatively uniformly on surface of GO under TEOS concentration of 0.10 mol/L (GO@SiO2-10), and the covering of SiO2 on GO could increase interlayer distance of GO nanosheets from 0.799 nm to 0.894 nm, thus reducing van der Waals forces between GO nanosheets and facilitating the dispersion. Tensile and compressive strength of scaffold containing GO@SiO2 hybrids were significantly enhanced, especially for the scaffold containing GO@SiO2-10 hybrids with enhancement of 30.95 % in tensile strength and 66.33 % in compressive strength compared with the scaffold containing GO. Additionally, cell adhesion and fluorescence experiments demonstrated excellent cytocompatibility of the scaffold.
The good dispersion of GO@SiO2 enhances the mechanical properties and cytocompatibility of scaffold, making it a potential candidate for bone tissue engineering applications.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We present an experimental demonstration of the feasibility of the first 20 + Mb/s Gaussian modulated coherent state continuous variable quantum key distribution system with a locally generated local ...oscillator at the receiver (LLO-CVQKD). To increase the signal repetition rate, and hence the potential secure key rate, we equip our system with high-performance, wideband devices and design the components to support high repetition rate operation. We have successfully trialed the signal repetition rate as high as 500 MHz. To reduce the system complexity and correct for any phase shift during transmission, reference pulses are interleaved with quantum signals at Alice. Customized monitoring software has been developed, allowing all parameters to be controlled in real-time without any physical setup modification. We introduce a system-level noise model analysis at high bandwidth and propose a new 'combined-optimization' technique to optimize system parameters simultaneously to high precision. We use the measured excess noise, to predict that the system is capable of realizing a record 26.9 Mb/s key generation in the asymptotic regime over a 15 km signal mode fibre. We further demonstrate the potential for an even faster implementation.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The reinforcement effect of fiber-reinforced polymer composites is usually limited because of the poor interfacial interaction between fiber and polymer, though fiber reinforcement is regarded as an ...effective method to enhance the mechanical properties of polymer. In this study, nano-SiO.sub.2 particles grafted by 3-Glycidoxypropyltrimethoxysilane (KH560) were introduced onto the surface of 3-Aminopropyltriethoxysilane (KH550) modified carbon fiber (CF) by a self-assembly strategy to improve the interfacial bonding between CF and biopolymer poly (lactic acid) (PLLA). The results indicated that PLLA chains preferred to anchor at the surface of nano-SiO.sub.2 particles and then formed high order crystalline structures. Subsequently, PLLA spherulites could epitaxially grow on the surface of functionalized CF, forming a transcrystalline structure at the CF/PLLA interface. Meanwhile, the nano-SiO.sub.2 particles were fixed in the transcrystalline structure, which induced a stronger mechanical locking effect between CF and PLLA matrix. The results of tensile experiments indicated that the PLLA/CF-SiO.sub.2 scaffold with a ratio of CF to SiO.sub.2 of 9:3 possessed the optimal strength and modulus of 10.11 MPa and 1.18 GPa, respectively. In addition, in vitro tests including cell adhesion and fluorescence indicated that the scaffold had no toxicity and could provide a suitable microenvironment for the growth and proliferation of cell. In short, the PLLA/CF-SiO.sub.2 scaffold with good mechanical properties and cytocompatibility had great potential in the application of bone tissue engineering.
In this work, we present a new framework for the stylization of text-based binary images. First, our method stylizes the stroke-based geometric shape like text, symbols, and icons in the target ...binary image based on an input style image. Second, the composition of the stylized geometric shape and a background image is explored. To accomplish the task, we propose legibility-preserving structure and texture transfer algorithms, which progressively narrow the visual differences between the binary image and the style image. The stylization is then followed by a context-aware layout design algorithm, where the cues for both seamlessness and aesthetics are employed to determine the optimal layout of the shape in the background. Given the layout, the binary image is seamlessly embedded into the background by texture synthesis under a context-aware boundary constraint. According to the contents of binary images, our method can be applied to many fields. We show that the proposed method is capable of addressing the unsupervised text stylization problem and is superior to state-of-the-art style transfer methods in automatic artistic typography creation. Besides, extensive experiments on various tasks, such as visual-textual presentation synthesis, icon/symbol rendering, and structure-guided image inpainting demonstrate the effectiveness of the proposed method.
In the analysis of complex historical layering, studies on how to avoid theoretical analysis and use quantitative methods of display and analysis are scarce. Therefore, we used space syntax to fill ...this gap in historical layering analysis. We established a spatial digital model by combining the urban historical landscape theory with the space syntax analysis method. Then, we quantitatively analysed the streetscapes in the four historical periods of Macau and the value-related development of the city’s economy, society, and culture. To this end, we used the theory of urban historical landscape to interpret the streetscape of Macau. We reviewed urban development under different spatial scales, which represent different states of historical layering. Changing ideological trends of construction have induced changes in the city, which have led to changes in the city style. The analysis considers the dimensions of space and time, and its results can guide the continued benign growth of the urban landscape and solve protection problems in practice. Meanwhile, the results of this work also indicate that the unique streetscape of Macau bred by the development of the city does not affect the newly constructed roads. The newly reclaimed areas and the streetscape of the new city are on the verge of homogeneity and cannot reflect the unique regional characteristics of Macau. Therefore, we used the historical map of Macau as a carrier, used space syntax to analyse the structure of Macau’s streetscape, and explored the apparent characteristics and value associations carried by the streetscape of Macau under different historical slices. Our results can help retrieve the value of Macau’s historical streetscape and devise a targeted protection strategy that can help pass on the historical streetscape of Macau to posterity.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The end-Devonian Hangenberg Crisis was one of the biggest Phanerozoic mass extinctions. However, the mechanism(s) that triggered this event is still debated. In this study, multiple geochemical ...paleoredox proxies (redox-sensitive trace metals e.g., Mo, U, Re, V and isotope systems Mo, U, S, C) were applied to the Exshaw Formation black shales to infer ocean redox conditions during the Hangenberg Crisis. The measured δ13Corg values generally decrease upsection in the Exshaw Formation. The Exshaw black shales have increasing maturity levels from east to west in the Western Canada Sedimentary Basin. Large sulfur isotope fractionations (–15‰ to 65‰) between original seawater sulfate and pyrite is best explained by microbial sulfate reduction during deposition and early diagenesis rather than thermochemical sulfate reduction. Precise Re-Os ages previously reported for the Exshaw Formation suggest that metal geochemical signatures in these shales, including overmature shales, were minimally affected by hydrocarbon maturation and reflected depositional conditions. Both Sr/Ba and TS/TOC ratios (the latter only from immature shales affected minimally by hydrocarbon generation) suggest predominantly brackish and marine settings with significant water exchange between the basin and open ocean. The TOC contents, redox-sensitive trace metal concentrations (Mo, U, Re), and Fe speciation indicate local bottom waters ranged from suboxic (with sulfidic pore waters) to euxinic. The authigenic δ98Mo and δ238U values for the Exshaw shales range from 0.3‰ to 1.1‰, and from –0.23‰ to 0.39‰, respectively. The δ98Mo of the Exshaw Formation may have been offset to lower values than coeval seawater because of a local particulate Fe-Mn shuttle and/or local weakly euxinic bottom waters. Two different correlation patterns (positive correlation and no correlation) of δ238U and U enrichment factors (EF) were observed for Exshaw black shales deposited from locally euxinic bottom waters. The positive correlation group samples (−0.13‰ to 0.23‰) suggest U isotope fractionations (0.4‰ to 0.8‰) between sediments and seawater like those observed in modern euxinic basins. Higher δ238U values (>0.2‰) in the no correlation group suggest even larger U isotope offsets (0.8–1.2‰) from seawater, possibly associated with removal of U into organic floccule layers during deposition. Applying the above Mo and U isotope fractionations to the Exshaw shales, global seawater δ98Mo and δ238U at the Devonian-Carboniferous boundary (DCB) may have been in the range of 1.4‰ to 1.9‰ and −0.9‰ to −0.5‰, respectively. A Mo and U isotope mass balance model suggests a large areal extent of euxinic seafloor (6–10%) at the DCB, which could be pervasive along continental margins and in epicontinental seas during transgression. Therefore, our data support expanded ocean euxinia at the DCB as an important contributor to the Hangenberg Crisis.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The figure-of-merits of ferroelectrics for transducer applications are their electromechanical coupling factor and the operable temperature range. Relaxor-PbTiO
ferroelectric crystals show a much ...improved electromechanical coupling factor k
(88~93%) compared to their ceramic counterparts (65~78%) by taking advantage of the strong anisotropy of crystals. However, only a few relaxor-PbTiO
systems, for example Pb(In
Nb
)O
-Pb(Mg
Nb
)O
-PbTiO
, can be grown into single crystals, whose operable temperature range is limited by their rhombohedral-tetragonal phase transition temperatures (T
: 60~120 °C). Here, we develop a templated grain-growth approach to fabricate -textured Pb(In
Nb
)O
-Pb(Sc
Nb
)O
-PbTiO
(PIN-PSN-PT) ceramics that contain a large amount of the refractory component Sc
O
, which has the ability to increase the T
of the system. The high k
of 85~89% and the greatly increased T
of 160~200 °C are simultaneously achieved in the textured PIN-PSN-PT ceramics. The above merits will make textured PIN-PSN-PT ceramics an alternative to single crystals, benefiting the development of numerous advanced piezoelectric devices.
During the actual construction of tunnel sidewall lining, construction workers often use only one or two windows per layer for pouring in order to reduce the construction sequence, which often leads ...to a reduction in the quality of tunnel sidewall concrete pouring. Therefore, this study analysed the necessity of the window-by-window pouring of sidewall lining through the study of concrete flow characteristics of the tunnel sidewall lining pouring process, and the reasonable spacing of pouring windows was analysed. This study firstly verified the accuracy of the simulation parameters and the feasibility of the simulation method of the lining pouring process through indoor experiments and simulation analyses, and then it numerically simulated and analysed the flow of concrete during the lining pouring process of tunnel sidewalls. The following conclusions were made: the smaller the slump of the freshly mixed concrete, the higher the pumping flow rate; additionally, the shorter the one-time pouring distance, the smaller the spacing of the trolley feeding window should be. Furthermore, this study makes suggestions for the reasonable spacing of pouring trolleys under several working conditions.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Abstract
To achieve high-efficiency catalysts for CO
2
reduction reaction, various catalytic metal centres and linker molecules have been assembled into covalent organic frameworks. The ...amine-linkages enhance the binding ability of CO
2
molecules, and the ionic frameworks enable to improve the electronic conductivity and the charge transfer along the frameworks. However, directly synthesis of covalent organic frameworks with amine-linkages and ionic frameworks is hardly achieved due to the electrostatic repulsion and predicament for the strength of the linkage. Herein, we demonstrate covalent organic frameworks for CO
2
reduction reaction by modulating the linkers and linkages of the template covalent organic framework to build the correlation between the catalytic performance and the structures of covalent organic frameworks. Through the double modifications, the CO
2
binding ability and the electronic states are well tuned, resulting in controllable activity and selectivity for CO
2
reduction reaction. Notably, the dual-functional covalent organic framework achieves high selectivity with a maximum CO Faradaic efficiency of 97.32% and the turnover frequencies value of 9922.68 h
−1
, which are higher than those of the base covalent organic framework and the single-modified covalent organic frameworks. Moreover, the theoretical calculations further reveal that the higher activity is attributed to the easier formation of immediate *CO from COOH*. This study provides insights into developing covalent organic frameworks for CO
2
reduction reaction.
The assembly of two tripyridinium‐tricarboxylate ligands and different metal ions leads to seven isostructural MOFs, which show novel 2D→2D supramolecular entanglement featuring catenane‐like ...interlocking of tricyclic cages. The MOFs show tripyridinium‐afforded and metal‐modulated photoresponsive properties. The MOFs with d10 metal centers (1‐Cd, 1‐Zn, 2‐Cd, 2‐Zn) show fast and reversible photochromism and concomitant fluorescence quenching, 1‐Ni displays slower photochromism but does not fluoresce, and 1‐Co and 2‐Co are neither photochromic nor fluorescent. It is shown here that the network entanglement dictates donor‐acceptor close contacts, which enable fluorescence originated from interligand charge transfer. The contacts also allow photoinduced electron transfer, which underlies photochromism and concomitant fluorescence response. The metal dependence in fluorescence and photochromism can be related to energy transfer through metal‐centered d‐d transitions. In addition, 1‐Cd is demonstrated to be a potential fluorescence sensor for sensitive and selective detection of UO22+ in water.
Organo‐originated and metal‐modulated photoresponsive properties were elucidated for a family of isostructural MOFs with tripyridinium‐tricarboxylate likers. Supramolecular entanglement between 2D networks dictates electron donor‐acceptor close contacts, which not only allow photoluminescence through interligand charge‐transfer excitation/emission but also cause photochromism through photoinduced electron transfer. Transition metal centers can weaken or prevent the photoresponsive properties because of energy transfer through d‐d transitions. The MOFs also show highly sensitive and selective fluorescence quenching response to UO22+ in water.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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