A series of lanthanide complexes with the 3,4,5-trimethoxybenzoic acid （3,4,5-tmoba） and 1,10-phenanthroline（phen）, Ln（3,4,5-tmoba）3phen2（Ln = Pr（l）, Nd （2） and Ho（3））, have been synthesized and ...characterized by a series of techniques including elemental analysis, IR spectra, X-ray crystallography and TG/DSC-FTIR technology. The three complexes have two kinds of coordination modes, in which the Pr3＋ and Nd3＋ cations are nine-coordinated and the Ho3＋ cation is eight-coordinated. The three-dimensional IR accumulation spectra of gaseous products for complexes 1-3 were analyzed and the gaseous products were identified by the typical IR spectra obtained from the 3D surface graphs. Meanwhile, we obtained the activation energy E of the first steps of complexes 1-3 by the integral isoconversional non-linear （NL-INT） method and discussed the non-isothermal kinetics of complexes 1-3 using the Malek method. Finally, SB（m, n） was defined as the kinetic method of the first-step thermal decomposition. The thermodynamic parameters △G≠, △H≠ and △S≠ of activation at the peak temperature were also calculated.
Although previous research has highlighted the disproportional contributions of star employees to their teams, an emerging line of research has begun to examine the potentially negative consequences ...of team stars. Drawing on a social model of team creativity, we develop a dualistic model of the influences of team creative stars on team creativity. Specifically, we explore the roles of two types of team members-star and nonstar employees-in driving team creativity. Across two multiwave and multisource field samples, we find that a creative star who occupies a central position in the team workflow network has both a positive direct effect on team creativity and a negative indirect effect on team creativity via reducing nonstars' learning (i.e., exploratory and exploitative activities). Our study also reveals that team coordination can mitigate the detrimental effect of a star's centrality on nonstars' learning behavior, and subsequently buffer the indirect effect on team creativity.
One potential benefit of team contexts is that members can share knowledge and ideas to help one another solve problems (e.g., advice-giving), thereby enhancing members’ creative potential. However, ...individuals’ advice-giving actions do not guarantee increases in recipients’ creativity and, in some cases, may even be a creative liability for the giver’s own subsequent creativity. We argue that considering advice givers’ brokerage in the team’s advice-giving network (i.e., advice brokerage) may clarify this phenomenon. Specifically, we posit that advice given from a brokerage position contains more nonredundant content that boosts recipients’ creativity. Further, we expect advice brokerage to positively influence a giver’s own creativity, though this effect is at least partially explained via recipients’ proximal creativity gains (e.g., recipients’ creativity change mediates the relationship). Recipients’ perceptions of psychological safety accentuate these relationships. Longitudinal field data support the main hypotheses, but also suggest that advice brokerage has more immediate proximal effects on givers’ creativity; an additional qualitative study elucidates several mechanisms by which brokered advice boosts creativity, including two associated with generating diverse ideas (idea integration, perspective-taking), two associated with domain-specific knowledge accumulation (knowledge accumulation, reflection), collective creativity, and creative feedback. The study yields several important implications.
•Spray falling film of oily wastewater over a horizontal tube was investigated.•VOF model was used to simulate the gas-liquid falling film flow.•The non-uniform film flow, temperature and thickness ...distributions were analyzed.•The non-uniform heat transfer properties were quantitatively investigated.•The effects of oil content, spray density and tube diameter were studied.
Recently, the spray heat exchanger became an important technology in a sewage source heat pump (SSHP) to recover thermal energy from oily wastewater. Hence, it's necessary to study the heat transfer properties and its enhancements. In this paper, a numerical model with VOF method was established to study the oily wastewater spray falling film over a horizontal tube. The flow field, falling film distribution and temperature distribution and heat transfer coefficient were investigated, and the non-uniformity of flow, temperature and heat transfer were further analyzed. Regions of low level film thickness were found around tube suggesting the non-uniform axial and circumferential distribution, corresponding to low film temperature regions. The non-uniformity of heat transfer coefficient at different circumferential angles was evaluated showing severe non-uniformity in impingement and departure regions due to the intense impinging of falling wastewater at the top and instability of dropping flow at the bottom. Thereafter, the influence of oil content, spray density and tube diameter were studied. The increase in oil content led the flow pattern changed from sheet flow to column-sheet flow due to increase in viscosity, resulting to non-uniformity increase from 0.15 to 0.19. Compared to tube diameter of 25.4 mm, the 12.7 mm tube accelerated flow downstream, therefore, the non-uniformity at the top was weakened to 0.13 and the downstream non-uniformity was strengthened to 0.19. The higher spray density of 0.262 kg/m∙s reduced the negative effect of viscosity, enhanced the flow velocity and weakened the non-uniformity at the top. However, the increase in flow velocity raised the flow instability in downstream suggesting higher non-uniformity.
Video anomaly detection is commonly used in many applications, such as security surveillance, and is very challenging. A majority of recent video anomaly detection approaches utilize deep ...reconstruction models, but their performance is often suboptimal because of insufficient reconstruction error differences between normal and abnormal video frames in practice. Meanwhile, frame prediction-based anomaly detection methods have shown promising performance. In this article, we propose a novel and robust unsupervised video anomaly detection method by frame prediction with a proper design which is more in line with the characteristics of surveillance videos. The proposed method is equipped with a multipath ConvGRU-based frame prediction network that can better handle semantically informative objects and areas of different scales and capture spatial-temporal dependencies in normal videos. A noise tolerance loss is introduced during training to mitigate the interference caused by background noise. Extensive experiments have been conducted on the CUHK Avenue, ShanghaiTech Campus, and UCSD Pedestrian datasets, and the results show that our proposed method outperforms existing state-of-the-art approaches. Remarkably, our proposed method obtains the frame-level AUROC score of 88.3% on the CUHK Avenue dataset.
Biogenesis of plant microRNAs (miRNAs) takes place in nuclear dicing bodies (D-bodies), where the ribonulease III-type enzyme Dicer-like 1 (DCL1) processes primary transcripts of miRNAs (pri-miRNAs) ...into miRNA/miRNA* (*, passenger strand) duplexes from either base-to-loop or loop-to-base directions. Hyponastic Leaves 1 (HYL1), a double-stranded RNA-binding protein, is crucial for efficient and accurate processing. However, whether HYL1 has additional function remains unknown. Here, we report that HYL1 plays a noncanonical role in protecting pri-miRNAs from nuclear exosome attack in addition to ensuring processing. Loss of functions in SOP1 or HEN2, two cofactors of the nucleoplasmic exosome, significantly suppressed the morphological phenotypes of hyl1-2. Remarkably, mature miRNAs generated from loop-to-base processing were partially but preferentially restored in the hyl1 sop1 and hyl1 hen2 double mutants. Accordingly, loop-to-base–processed pri-miRNAs accumulated to higher levels in double mutants. In addition, dysfunction of HEN2, but not of SOP1, in hyl1-2 resulted in overaccumulation of many base-to-loop–processed pri-miRNAs, with most of their respective miRNAs unaffected. In summary, our findings reveal an antagonistic action of exosome in pri-miRNA biogenesis and uncover dual roles of HYL1 in stabilizing and processing of pri-miRNAs.
Towards super-clean graphene Lin, Li; Zhang, Jincan; Su, Haisheng ...
Nature communications,
04/2019, Letnik:
10, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Impurities produced during the synthesis process of a material pose detrimental impacts upon the intrinsic properties and device performances of the as-obtained product. This effect is especially ...pronounced in graphene, where surface contamination has long been a critical, unresolved issue, given graphene's two-dimensionality. Here we report the origins of surface contamination of graphene, which is primarily rooted in chemical vapour deposition production at elevated temperatures, rather than during transfer and storage. In turn, we demonstrate a design of Cu substrate architecture towards the scalable production of super-clean graphene (>99% clean regions). The readily available, super-clean graphene sheets contribute to an enhancement in the optical transparency and thermal conductivity, an exceptionally lower-level of electrical contact resistance and intrinsically hydrophilic nature. This work not only opens up frontiers for graphene growth but also provides exciting opportunities for the utilization of as-obtained super-clean graphene films for advanced applications.
•Spray falling film of oily wastewater over a horizontal tube was investigated.•VOF model was used to simulate the gas-liquid falling film flow.•The unsteady film and tube temperature distributions ...were analyzed.•The unsteady heat transfer properties were investigated.•The effects of oil content, spray density and tube diameter were studied.
The oil exploit in late-period oilfield usually produce large amount of oily wastewater at moderate and high temperature, the thermal energy of which can be recuperated through a sewage source heat pump (SSHP). Among different kinds of heat recovery facility in SSHP, the spray heat exchanger is a better choice to recover energy from the oily wastewater due to its advantages of simple structure, high heat transfer efficiency and anti-blocking ability. However, the spray falling heat transfer was an unsteady procedure, and the complex properties of oil-water mixer will lead to different heat transfer and flow characteristics in the heat exchanger, which also affect the unsteady heat transfer. Hence, in this paper, a numerical model with VOF method was established to study the unsteady heat transfer properties of oily wastewater spray falling film on a horizontal tube, and the effects of different oil contents, spray densities and tube diameters on the unsteady properties of heat transfer coefficient. The results show that the film temperature and tube temperature were continuously varying with time, and the slight variation in upper part and greater variation in lower part of the tube were observed. A further understanding on the flow field of liquid on the tube revealed the unsteady heat transfer was due to the falling flow instability. Thereafter, the influences of oil content, tube diameter and spray density on the unsteady heat transfer were analyzed. It was found that the decrease in oil content, increase in tube diameter will reduce the fluctuation intensity of heat transfer properties.
•Spray falling film of oily wastewater over a horizontal tube was investigated.•VOF model was used to track the gas-liquid interface of falling film flow.•The effect of different glycerin content on ...heat transfer was investigated.•The effects of spray parameters and tube parameters were studied.•The temperature distribution inside the liquid film was analyzed.
Sewage heat exchanger is the key equipment of oily sewage source heat pump system, which has great influence on its performance. Among many kinds of heat exchangers, the spray heat exchanger has the advantages of simple structure, high heat transfer efficiency, good operability and anti-blocking ability. Therefore, it can be used in a sewage source heat pump to recover energy from the oily wastewater. However, the heat transfer and flow characteristics of oily wastewater spraying in the heat exchanger are different from the ordinary sewage heat pump system. Hence, it’s necessary to investigate the heat transfer of oily wastewater spray falling film on horizontal tube for better application. In this paper, a three-dimensional numerical model was established for a spraying heat exchanger in the oily sewage source heat pump system, and a mixture of water and glycerin was used to simulate the oily wastewater. The VOF model was used to track the liquid-gas interface of oily wastewater spray falling film over a horizontal tube in the heat exchanger, and the effects of different glycerin content, heat flux, spray density, tube diameter, liquid distributor height and spray temperature on the heat transfer coefficient were investigated. To further understand the mechanism of heat transfer inside the film, the temperature distribution inside the liquid film was obtained and analyzed. The results show that: (1) the heat transfer characteristic can be divided into three regions around the tube; (2) the local heat transfer coefficient decreased with increase of glycerin content in the thermal developing region; (3) the local heat transfer coefficient increased with the increase of the spray density and spray temperature, decreased with the increase of the tube diameter and was little affected by heat flux in the thermal developing region, and the increase in the liquid distributor height caused increase of local heat transfer coefficient in the upper part of the tube.
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