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•Multilayered distribution of FRs and CNTs was tailored by layer multiplication.•Synergistic effect between flame-retarding and EMI-shielding layers was disclosed.•Impedance ...difference between adjacent layers enlarged the EMI-shielding capacity.•Continuous carbonaceous structure could be yielded among layers in combustion.•EMI SE of the char residue was beyond 60 dB.
A flexible and flame-retarding thermoplastic polyurethane (TPU)-based electromagnetic interference (EMI)-shielding composite with multilayered structure was fabricated via coextrusion technology. The layer multiplication could not only create numerous layer interfaces, but also tailor the selective distribution of flame retardants (FRs) and carbon nanotubes (CNTs) endowing each extrudate excellent flexibility. When the layer numbers reached 32, synergistic flame-retarding and EMI-shielding multiple functional networks were generated and performed the optimum comprehensive performances, overcoming the major disadvantage of the conventional composites where the networks may breakup each other. Due to the interfacial polarization loss caused by the impedance difference between conducting and flame-retarding layers, the maximum shielding effectiveness (SE) of 38.5 dB was obtained with less than 4 wt% CNTs. Besides, superior flame retardancy rated by V-0 with quick self-extinguishment and low heat release was achieved owning to the production of continuous and foaming carbonaceous structure among layers. More significantly, the SE of the char residue, which was less concerned in conventional composite systems, was even beyond 60 dB. The maintenance of the multilayered architecture and the generation of atmosphere cavities were regarded to benefit for providing numerous impedance-mismatched interfaces and extending the transmission path of the microwaves. Consequently, the multilayer-assembled strategy was proposed to balance the mechanical, flame-retarding and EMI-shielding performances for satisfying with the stringent requirements of protective materials.
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The environment-material interface plays a key role in determining the performance of a material in a variety of applications such as separating gas molecules or solutes, harnessing ...photons or electrons, and responding to biomolecules or organisms. Layer-by-layer assembly (LbL) technologies provide a means of controlling the surface and interface of a material, resulting in a composite in which the interface and the bulk of the material can be designed and controlled to a large extent independently. In addition, some exciting and novel applications have been widely studied for LbL assembly, such as vibration damping composites, shape memory materials, advanced dielectric composites, and radiation protection composites. In this paper, we review the development history and state-of-the-art of LbL assembly, and highlight the limitations of traditional LbL assembly in polymer solutions. As the forced assembly technology is simple, fast, and widely used for polymer substrates, it has attracted extensive attention and shows potential for application. Moreover, with the emergence of a new strategy and mechanism of LbL assembly (e.g., assembly with polymer crystallization) and the expansion of application fields, a comprehensive review focusing on the progress of LbL assembly in recent years is still lacking, which is the motivation for this review. Topics such as morphological characterization and control methods, the resulting multilayered interfaces, and their outstanding properties are discussed. A general but comprehensive review covering all aspects of the LbL assembly from mechanism to application has been carried out.
It is well known that abscisic acid (ABA)-induced leaf senescence and premature leaf senescence negatively affect the yield of rice (Oryza sativa). However, the molecular mechanism underlying this ...relationship, especially the upstream transcriptional network that modulates ABA level during leaf senescence, remains largely unknown. Here, we demonstrate a rice NAC transcription factor, OsNAC2, that participates in ABA-induced leaf senescence. Overexpression of OsNAC2 dramatically accelerated leaf senescence, whereas its knockdown lines showed a delay in leaf senescence. Chromatin immunoprecipitation-quantitative PCR, dual-luciferase, and yeast one-hybrid assays demonstrated that OsNAC2 directly activates expression of chlorophyll degradation genes, OsSGR and OsNYC3. Moreover, ectopic expression of OsNAC2 leads to an increase in ABA levels via directly up-regulating expression of ABA biosynthetic genes (OsNCED3 and OsZEP1) as well as down-regulating the ABA catabolic gene (OsABA8ox1). Interestingly, OsNAC2 is upregulated by a lower level of ABA but downregulated by a higher level of ABA, indicating a feedback repression of OsNAC2 by ABA. Additionally, reduced OsNAC2 expression leads to about 10% increase in the grain yield of RNAi lines. The novel ABA-NAC-SAGs regulatory module might provide a new insight into the molecular action of ABA to enhance leaf senescence and elucidates the transcriptional network of ABA production during leaf senescence in rice.
Plants can perceive environmental changes and respond to external stressors. Here, we show that OsNAC2, a member of the NAC transcription factor family, was strongly induced by ABA and osmotic ...stressors such as drought and high salt. With reduced yields under drought conditions at the flowering stage, OsNAC2 overexpression lines had lower resistance to high salt and drought conditions. RNAi plants showed enhanced tolerance to high salinity and drought stress at both the vegetative and flowering stages. Furthermore, RNAi plants had improved yields after drought stress. A microarray assay indicated that many ABA-dependent stress-related genes were down-regulated in OsNAC2 overexpression lines. We further confirmed that OsNAC2 directly binds the promoters of LATE EMBRYOGENESIS ABUNDANT 3 (OsLEA3) and Stress-Activated Protein Kinases 1 (OsSAPK1), two marker genes in the abiotic stress and ABA response pathways, respectively. Our results suggest that in rice OsNAC2 regulates both abiotic stress responses and ABA-mediated responses, and acts at the junction between the ABA and abiotic stress pathways.
We reported the design of a grape-cluster-like conductive network in a polypropylene (PP) matrix, where oriented multi-walled carbon nanotubes (MWCNTs) served as branches and provided charge ...transport over large distances while grape-like carbon black (CB) aggregates enriched around MWCNTs and linked these conductive tubes through charge transport over small distances. The key for construction of this grape-cluster-like conductive network was the extension and orientation of MWCNTs, which was achieved in this work by multistage stretching extrusion with an assembly of laminating-multiplying elements (LMEs, which divide and recombine polymer melts). The highest efficient grape-cluster-like conductive network was obtained at a CB:MWCNT weight ratio of 6. The experimental results showed that this novel grape-cluster-like conductive network provided a low percolation threshold for PP/CB/MWCNT composites due to the synergistic effect of CB and oriented MWCNTs. When the combined CB and MWCNT content was about 6.9vol%, the electrical resistivity of PP/CB/MWCNT composites prepared by multistage stretching extrusion with 6 LMEs decreased to only 0.63Ωcm.
This novel grape-cluster-like conductive network provided a low percolation threshold for PP/CB/MWCNT composites due to the synergistic effect of CB and oriented MWCNTs. Display omitted
Injury is a leading cause of morbidity and mortality among children in the USA. Understanding the impact of executive functions (EFs) on the risk of injuries is crucial for developing effective ...interventions. However, literature has failed to examine the relationship between multiple EFs and injury domains. The present paper quantitatively synthesized research on
cool
and
hot
EFs and children’s intentional and unintentional injury risks using a novel meta-analytic structural equation modeling (MASEM) approach. A systematic review was conducted in the following databases: PsycINFO, Scopus, SafetyLit, Cochrane Central, and PubMed (Medline). After screening titles, abstracts, and full texts, a total of 31 studies were eligible for the MASEM analysis. One-stage MASEM was conducted on six conceptualized path analysis models according to the complexity of exogenous and endogenous variables. The MASEM models suggested that hot and cool EFs were negatively associated with children’s risk of injury or injury-related risk behaviors regardless of mean age and proportion of females. Among cool EF skills, inhibitory control, but not working memory or cognitive flexibility, was significantly associated with risks of unintentional injuries. Emotion regulation was the dominant hot EF skill examined in the literature and was found significantly associated with risks of non-suicidal self-injuries (NSSIs). EF has a significant impact on children’s risk of both unintentional and intentional injuries. Future research should focus on the combined force of hot and cool EF on children’s risks of injuries and injury-related risk behaviors.
The multilayered distribution of intumescent flame retardants (IFRs) was obtained by fabricating a series of alternating multilayered composites consisting of polypropylene (PP) and IFR-filled PP ...(PPFR) layers through a layer-multiplying coextrusion technology. With increasing the layer numbers, the limiting oxygen index (LOI) and elongation at break (εb) of the multilayered composites were enhanced, accompanied with the gradually decreased values of the peak heat release rate and the total heat release. When the layer numbers beyond 16, the LOI and εb values were even larger than those of the PP/IFR conventional composite filled with the same content of IFRs. The layer interfaces and confined layer spaces in the multilayered system were considered to play a crucial role in retarding the spread of fire as well as the propagation of crazes. The significance of this work was providing an optimal route to fabricate flame-retarding composites with excellent mechanical properties.
Doping is indispensable to tailor phase-change materials (PCM) in optical and electronic data storage. Very few experimental studies, however, have provided quantitative information on the ...distribution of dopants on the atomic-scale. Here, we present atom-resolved images of Ag and In dopants in Sb
Te-based (AIST) PCM using electron microscopy and atom-probe tomography. Combing these with DFT calculations and chemical-bonding analysis, we unambiguously determine the dopants' role upon recrystallization. Composition profiles corroborate the substitution of Sb by In and Ag, and the segregation of excessive Ag into grain boundaries. While In is bonded covalently to neighboring Te, Ag binds ionically. Moreover, In doping accelerates the crystallization and hence operation while Ag doping limits the random diffusion of In atoms and enhances the thermal stability of the amorphous phase.
Flexible strain sensors have received increasing attention with the development of wearable electronic devices. However, integrating wide strain detection range, high sensitivity while maintaining ...relatively wide linear response range for such sensor system still remain a challenge. A fabric based flexible sensor (S-CNT/PDMS-F) was designed and fabricated, and the sensor can simultaneously achieve high sensitivity, wide linear response and strain detection range by combining self-segregated carbon nanotube (CNT)/polydimethylsiloxane (PDMS) composites and elastic medical bandage. It has been observed that this new sensor system can achieve a high sensitivity with a gauge factor of 615, a large linear responsive range of 0–100% strain (R2 = 0.993) and a wide strain detection range of ∼ 200%, which is superior to almost all the reported CNT/PDMS flexible strain sensors. Compared to the similar fabric based strain sensor system deploying non self-segregated structure (C-CNT/PDMS-F), our S-CNT/PDMS-F demonstrates higher electrical conductivity and lower electrical percolation threshold and response time of 55 ms, as well as more stable and repeatable performance under cyclic loading conditions. The capability of the sensors in monitoring physiological activities and weight distribution has also been demonstrated.
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•A CNT/PDMS nanocomposite coating with a self-segregated structure was prepared.•The nanocomposite coating was applied on an elastic medical bandage to obtain a fabric-based strain sensor.•The sensor showed a high sensitivity, wide linear response and strain detection range.
At the 2008 inaugural meeting of the Consortium of Universities for Global Health (CUGH), participants discussed the rapid expansion of global health programs and the lack of standardized ...competencies and curricula to guide these programs. In 2013, CUGH appointed a Global Health Competency Subcommittee and charged this subcommittee with identifying broad global health core competencies applicable across disciplines.
The purpose of this paper is to describe the Subcommittee's work and proposed list of interprofessional global health competencies.
After agreeing on a definition of global health to guide the Subcommittee's work, members conducted an extensive literature review to identify existing competencies in all fields relevant to global health. Subcommittee members initially identified 82 competencies in 12 separate domains, and proposed four different competency levels. The proposed competencies and domains were discussed during multiple conference calls, and subcommittee members voted to determine the final competencies to be included in two of the four proposed competency levels (global citizen and basic operational level – program oriented).
The final proposed list included a total of 13 competencies across 8 domains for the Global Citizen Level and 39 competencies across 11 domains for the Basic Operational Program-Oriented Level.
There is a need for continued debate and dialog to validate the proposed set of competencies, and a need for further research to identify best strategies for incorporating these competencies into global health educational programs. Future research should focus on implementation and evaluation of these competencies across a range of educational programs, and further delineating the competencies needed across all four proposed competency levels.
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