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| 2. |
- Kim, Se-Hoon, et al.
(författare)
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Nanophase oxalate precursors of thermoelectric CoSb3 by controlled coprecipitation predicted by thermodynamic modeling
- 2016
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Ingår i: Advanced Powder Technology. - : Elsevier. - 0921-8831 .- 1568-5527. ; 27:2, s. 773-778
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Tidskriftsartikel (refereegranskat)abstract
- The precursors for the formation of thermoelectric skutterudite CoSb3 nanoparticles are predicted by thermodynamic modeling of the complex chemical species. Based on the results, equimolar mixture of CoC2O4 center dot 2H(2)O and Sb(C2O4) OH are successively co-precipitated under controlled conditions of pH = 2.7 and concentration of reactants. The as synthesized powder was decomposed at 350 degrees C to remove the organic molecules and further reduced to CoSb3 phase by heating at 530 degrees C under hydrogen flow. The obtained powder was consolidated by spark plasma sintering (SPS). CoSb3 prepared by controlled chemical co-precipitation has p-type behavior with a positive sign of the Seebeck coefficient. TE transport properties were measured, which revealed that the Seebeck coefficient increased 2.5 times with increasing the temperature and it is lower than the ball milled CoSb3. Thermal conductivity of sintered CoSb3 at 773 K starts from 0.06 W/cm K at room temperature and decreases to 0.04 W/cm K at 700 K, which is lower than the bulk counterpart. The ZT of coprecipitated CoSb3 and SPS consolidated at 773 K shows 2 times higher than the ball milled one. (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.
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| 3. |
- Choi, Joong Il Jake, et al.
(författare)
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Atomic-scale view of stability and degradation of single-crystal MAPbBr(3) surfaces
- 2019
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 7:36, s. 20760-20766
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Tidskriftsartikel (refereegranskat)abstract
- While organic-inorganic hybrid perovskite solar cells are emerging as promising candidates for next-generation solar cells with fascinating power conversion efficiency, the instability of perovskites remains a significant bottleneck for their commercialization. An atomic scale understanding of the degradation of hybrid perovskites, however, is only in its beginning stages because of the difficulty in preparing well-defined surface conditions for characterization. Using atomic force microscopy at ultra-high vacuum and room temperature, we report the first direct observation of the degradation process of a cleaved methylammonium lead bromide, MAPbBr(3) (MA: CH3NH3+), single crystal. Upon in situ cleavage, atomic force microscopy images show large flat terraces with monolayer height steps, which correspond to the surface of cubic MAPbBr(3) with methylammonium ligand termination. While this surface can be prepared via the cleavage process and is energetically stable, we observe that after several weeks under dark and vacuum conditions it degrades and produces clusters surrounded by pits. Guided by density functional theory calculations, we propose a degradation pathway that initiates even at low humidity levels and leads to the formation of surface PbBr2 species. We finally identify the electronic structure of the MA-bromine-terminated flat surface and find that it is correlated with a strong field-induced degradation of the MAPbBr(3) only at positive sample bias voltages.
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| 4. |
- Kim, Hwi-Min, et al.
(författare)
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Monolithic integration of self-aligned nanoisland laser with shifted-air-hole waveguide
- 2018
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Ingår i: Optics Express. - : OPTICAL SOC AMER. - 1094-4087. ; 26:10, s. 12569-12578
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Tidskriftsartikel (refereegranskat)abstract
- We report a novel scheme for monolithic integration of a nanoisland laser with a shifted-air-hole waveguide by employing selective etching techniques. An active L3 laser cavity and passive shifted-air-hole waveguide are simultaneously formed through a single fabrication step. In the shifted-air-hole waveguide, the air-hole position is adjusted to be compatible with selective etching. The spectral overlap between the L3 laser resonance and guided mode is achieved by introducing small air holes at the nodes of the shifted-air-hole waveguide. Experiments show that >60% of the light is coupled from the nanoisland laser to the end of the 12-mu m-long waveguide.
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| 5. |
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| 6. |
- Kwon, Kiwoong, et al.
(författare)
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Traffic-aware stateless multipath routing for fault-tolerance in IEEE 802.15.4 wireless mesh networks
- 2018
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Ingår i: Wireless networks. - : Springer. - 1022-0038 .- 1572-8196. ; 24:5, s. 1755-1774
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Tidskriftsartikel (refereegranskat)abstract
- Single-path routing is widely used in wireless networks due to low resource consumption. However, it is vulnerable to link failure because such a failure may adversely affect an entire path. To overcome this, multipath routing has been proposed providing fault-tolerance. In this paper, we propose a novel multipath routing protocol called traffic-aware stateless multipath routing (TSMR) based on an overlaid tree topology comprising two topologies, namely, bounded degree tree (BDT) and root-oriented directional tree (RODT). BDT is strong on reducing routing overhead, and RODT is resilient against lossy links. By synergistically overlaying them, TSMR dynamically selects the local optimal path according to the given traffic flow and the failure on the primary path. In particular, TSMR enables stateless and low overhead routing despite multipath routing by keeping only one-hop neighbors to maintain multiple paths. To evaluate TSMR, we conducted simulations with a shadowing model reflecting lossy links, and compared with single and multipath routing protocols, such as ZTR, STR, AODV, and RPL. The simulation results show that the overall performance of TSMR surpasses that of others for packet delivery ratio, end-to-end delay, control overhead, memory consumption, and power consumption regardless of network size, number of sessions, and traffic flow.
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| 7. |
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| 8. |
- Cho, Hyunsoo, et al.
(författare)
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YAP and TAZ Negatively Regulate Prox1 During Developmental and Pathologic Lymphangiogenesis
- 2019
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Ingår i: Circulation Research. - : Lippincott Williams & Wilkins. - 0009-7330 .- 1524-4571. ; 124:2, s. 225-242
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Tidskriftsartikel (refereegranskat)abstract
- Rationale: The Hippo pathway governs cellular differentiation, morphogenesis, and homeostasis, but how it regulates these processes in lymphatic vessels is unknown. Objective: We aimed to reveal the role of the final effectors of the Hippo pathway, YAP (Yes-associated protein) and TAZ (transcriptional coactivator with PDZ-binding motif), in lymphatic endothelial cell (LEC) differentiation, morphogenesis, and homeostasis. Methods and Results: During mouse embryonic development, LEC-specific depletion of Yap/Taz disturbed both plexus patterning and valve initiation with upregulated Prox1 (prospero homeobox 1). Conversely, LEC-specific YAP/TAZ hyperactivation impaired lymphatic specification and restricted lymphatic sprouting with profoundly downregulated Prox1. Notably, lymphatic YAP/TAZ depletion or hyperactivation aggravated or attenuated pathological lymphangiogenesis in mouse cornea. Mechanistically, VEGF (vascular endothelial growth factor)-C activated canonical Hippo signaling pathway in LECs. Indeed, repression of PROX1 transcription by YAP/TAZ hyperactivation was mediated by recruitment of NuRD (nucleosome remodeling and histone deacetylase) complex and endogenous binding activity of TEAD (TEA domain family members) to the PROX1 promoter. Furthermore, YAP/TAZ hyperactivation enhanced MYC signaling and inhibited CDKN1C, leading to cell cycle dysregulation and aberrant proliferation. Conclusions: We find that YAP and TAZ play promoting roles in remodeling lymphatic plexus patterning and postnatal lymphatic valve maintenance by negatively regulating Prox1 expression. We further show that YAP and TAZ act as plastic regulators of lymphatic identity and define the Hippo signaling-mediated PROX1 transcriptional programing as a novel dynamic checkpoint underlying LEC plasticity and pathophysiology.
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| 9. |
- De Adhikari, Amrita, et al.
(författare)
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Polyaniline-Stabilized Intertwined Network-like Ferrocene/Graphene Nanoarchitecture for Supercapacitor Application
- 2017
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Ingår i: Chemistry - An Asian Journal. - : WILEY-V C H VERLAG GMBH. - 1861-4728 .- 1861-471X. ; 12:8, s. 900-909
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Tidskriftsartikel (refereegranskat)abstract
- The present work highlights the effective H-p interaction between metallocenes ( ferrocene; Fc) and graphene and their stabilization in the presence of polyaniline ( PANI) through pi-pi interactions. The PANI-stabilized Fc@ graphene nanocomposite ( FcGA) resembled an intertwined network-like morphology with high surface area and porosity, which could make it a potential candidate for energy-storage applications. The relative interactions between the components were assessed through theoretical ( DFT) calculations. The specific capacitance calculated from galvanostatic charging/discharging indicated that the PANI-stabilized ter-nary nanocomposite exhibited a maximum specific capacitance of 960 Fg(-) at an energy density of 85 WhKg(-1) and a current density of 1 Ag-. Furthermore, electrochemical impedance spectroscopy (EIS) analysis confirmed the low internal resistance of the as-prepared nanocomposites, which showed improved charge-transfer properties of graphene after incorporation of Fc and stabilization with PANI. Additionally, all electrodes were found to be stable up to 5000 cycles with a specific capacitance retention of 86%, thus demonstrating the good reversibility and durability of the electrode material.
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| 10. |
- Hosseini, Seyed Mehdi, et al.
(författare)
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Lipase-immobilized chitosan-crosslinked magnetic nanoparticle as a biocatalyst for ring opening esterification of itaconic anhydride
- 2019
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Ingår i: Biochemical Engineering Journal. - : Elsevier BV. - 1369-703X. ; 143, s. 141-150
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Tidskriftsartikel (refereegranskat)abstract
- Nano-magnetic biocatalyst particles, lipase-immobilized chitosan-crosslinked magnetic nanoparticles (LCMNs) were prepared by a new approach integrated from magnetic nanoparticle preparation, in situ thin layer coating and crosslinking of chitosan, and enzyme immobilization method. Thin layer coating of magnetic (Fe3O4) by crosslinked chitosan nanoparticles were prepared by reacting FeCl3.6H2O and sodium acetate in ethylene glycol, followed by suspension cross-linking using citric acid on the hydroxyl and amine group of chitosan at neutral pH. The resulting nanoparticles were used to immobilize the lipase from Candida antarctica Lipase B by linking using glutaraldehyde. The particles in each step were characterized by Fourier transform infrared spectrometry (FT-IR), vibrating-sample magnetometer measurements (VSM), and transmission electron microscopy (TEM). The magnetic biocatalyst, LCMN was found to have high storage stability and reusability due to the tightly crosslinked structure of chitosan and covalent bond immobilization. LCMNs were used for the oligomerization of itaconic anhydride by ring opening esterification, and the results were compared with those from free lipase and commercial immobilized lipase. The molecular mass of the products obtained with the biocatalysts showed similar Mn profiles with 308–381. This process represents a green approach for the preparation of both biobased magnetic biocatalysts and functional oligo-esters, and can be applied for both the immobilization of other enzymes and the utilization of photo-curable functional esters as biobased functional materials.
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