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81.
Ford J.E. Goossen K.W. Walker J.A. Neilson D.T. Tennant D.M. Seo Yeon Park Sulhoff J.W. 《IEEE journal of selected topics in quantum electronics》2004,10(3):579-587
Dynamic gain equalization filters (DGEFs) are important for high-performance wavelength division multiplexed (WDM) communications. One of the first demonstrated DGEF used a micromechanical etalon filter array illuminated with free-space spectral demultiplexing optics. Here, we present subsequent research on etalon-based dynamic spectral filters, including vertical device structures which linearize and reduce the drive voltage from 70 to 40 V, and spatially-segmented etalons which allow channelized spectral equalization and further reduce drive voltage. We describe a prototype using a simplified cylindrical optomechanical package with a 104-nm broadband spectral response, 7.5-dB insertion loss and less than 16-V operation voltage. Finally, we show the use of a 42-nm bandwidth DGEF prototype with feedback stabilization to more than double the number of channels and operating bandwidth of a conventional Erbium-doped fiber amplifier while maintaining < 1-dB power uniformity. 相似文献
82.
Fazli Akram Rizwan Ahmed Malik Salman Ali Khan Ali Hussain Soonil Lee Myang-Hwan Lee Choi Hai In Tae-Kwon Song Won-Jeong Kim Yeon Soo Sung Myong-Ho Kim 《Journal of Electroceramics》2018,41(1-4):93-98
In the present work, composition dependent crystal structure, ferroelectric, piezoelectric, and temperature dependent dielectric properties of the BiGaO3-modified (1–x)(0.65Bi1.05FeO3–0.35BaTiO3) (BFBT35–xBG, where x?=?0.00–0.03) lead-free ceramics were systematically investigated by solid-state reaction method, followed by water quenching process. The substitution of BG successfully diffuses into the lattice of the BFBT ceramics, without changing the pseudo-cubic structure of the samples. The scanning electron microscopy (SEM) results revealed that the average grain size was increased with BG-content in BFBT system. The BFBT–xBG ceramics showed a maximum in permittivity (?max) at temperatures (Tmax) above 500 °C in the compositional range of 0.00?≤?x?≤?0.03. The electro-strain is measured to be 0.125% (d*33 ~ 250 pm/V) under unipolar fields (5 kV/mm) for BFBT–0.01BG ceramics. The same composition (x?=?0.01), large static piezoelectric constant (d33 ~ 165 pC/N) and electromechanical coupling factor (kp ~ 25%) were obtained. The above investigated characterizations suggests that BFBT–BG material is favorable for piezoelectric and high temperature applications. 相似文献
83.
84.
Novel biomineralized hydrogels composed of hyaluronic acid (HA) and vinyl phosphonic acid (VPAc) were designed with the aim of developing a biomimetic hydrogel system to improve bone regeneration by local delivery of a protein drug including bone morphogenetic proteins. We synthesized crosslinked hydrogels composed of methacrylated HA and poly(VPAc) [P(VPAc)], which serves as a binding site for calcium ions during the mineralization process. The HA/P(VPAc) hydrogels were biomineralized by a urea‐mediation method to create functional polymer hydrogels that can deliver the protein drug and mimic the bone extracellular matrix. The water content of the hydrogels was influenced by the HA/P(VPAc) composition, crosslinking density, biomineralization, and ionic strength of the swelling media. All HA/P(VPAc) hydrogels maintained more than 84% water content. Enzymatic degradation of HA/P(VPAc) hydrogels was dependent on the concentration of hyaluronidase and the crosslinking density of the polymer network within the hydrogel. In addition, the release behavior of bovine serum albumin from the HA/PVPAc hydrogels was mainly influenced by the drug loading content, water content, and biomineralization of the hydrogels. In a cytotoxicity study, the HA/P(VPAc) and biomineralized HA/P(VPAc) hydrogels did not significantly affect cell viability. These results suggest that biomineralized HA/P(VPAc) hydrogels can be tailored to create a biomimetic hydrogel system that promotes bone tissue repair and regeneration by local delivery of protein drugs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41194. 相似文献
85.
86.
Tai Yeon LeeTodd M Roper E.Sönny JonssonIgor Kudyakov K ViswanathanC Nason C.A GuymonC.E Hoyle 《Polymer》2003,44(10):2859-2865
The photopolymerization of vinyl acrylate has been investigated using real-time FTIR. The acrylate and vinyl groups exhibit different polymerization kinetics with the acrylate functionality polymerizing at a much faster rate. Vinyl acrylate not only self-initiates its own free-radical polymerization, but also photoinitiates the polymerization of mono- and difunctional acrylates. Kinetic studies using a model monomer system indicate that it is essential for the acrylate and vinyl group to be part of the same molecule in order to function as an effective initiator for acrylate polymerization. 相似文献
87.
Junyeong Kim Jeong Yeon Do No-Kuk Park Seung Jong Lee Jin-Pyo Hong Misook Kang 《Korean Journal of Chemical Engineering》2018,35(5):1089-1098
Nano-sized bismuth sulfide (Bi2S3) and titanium dioxide (TiO2) with the orthorhombic and anatase tetragonal structures, respectively, were synthesized for application as catalysts for the reduction of carbon dioxide (CO2) to methane (CH4). Four double-layered dense films were fabricated with different coating sequences—TiO2 (bottom layer)/Bi2S3 (top layer), Bi2S3/TiO2, TiO2/Bi2S3: TiO2 (1 : 1) mix, and Bi2S3: TiO2 (1 : 1) mix/Bi2S3: TiO2 (1 : 1) mix—and applied to the photoreduction of CO2 to CH4; the catalytic activity of the fabricated films was compared to that of the pure TiO2/TiO2 and Bi2S3/Bi2S3 doubled-layered films. The TiO2/Bi2S3 double-layered film exhibited superior photocatalytic behavior, and higher CH4 production was obtained with the TiO2/Bi2S3 double-layered film than with the other films. A model of the mechanism underlying the enhanced photoactivity of the TiO2/Bi2S3 double-layered film was proposed, and it was attributed in effective charge separation. 相似文献
88.
Ziqi Zhou Ji-Won Choi Joon Yeon Shin Dong-Uk Kim Bitna Kweon Hyuncheol Oh Youn-Chul Kim Ho-Joon Song Gi-Sang Bae Sung-Joo Park 《International journal of molecular sciences》2021,22(13)
Acute pancreatitis (AP) is an inflammatory disorder, involving acinar cell death and the release of inflammatory cytokines. Currently, there are limited effective therapeutic agents for AP. Betulinic acid (BA) is a pentacyclic triterpenoid extracted from Betula platyphylla that has been shown to have anti-inflammatory effects. In this study, we aimed to investigate the effects of BA on AP and elucidate the potential underlying mechanisms. AP was induced in mice through six intraperitoneal injections of cerulein. After the last cerulein injection, the mice were sacrificed. Our results revealed that pre- and post-treatment with BA significantly reduced the severity of pancreatitis, as evidenced by a decrease in histological damage in the pancreas and lung, serum amylase and lipase activity and pancreatic myeloperoxidase activity. Furthermore, BA pretreatment reduced proinflammatory cytokine production, augmentation of chemokines, and infiltration of macrophages and neutrophils in the pancreas of AP mice. In addition, mice that were pretreated with BA showed a reduction in Iκ-Bα degradation and nuclear factor-kappa B (NF-κB) binding activity in the pancreas. Moreover, BA reduced the production of proinflammatory cytokines and NF-κB activation in pancreatic acinar cells (PACs). These findings suggest that BA may have prophylactic and therapeutic effects on AP via inhibition of the NF-κB signaling pathway. 相似文献
89.
Vinoth Kumar Rethineswaran Da Yeon Kim Yeon-Ju Kim WoongBi Jang Seung Taek Ji Le Thi Hong Van Ly Thanh Truong Giang Jong Seong Ha Jisoo Yun Jinsup Jung Sang-Mo Kwon 《International journal of molecular sciences》2021,22(9)
Endothelial progenitor cells (EPCs) are specialized cells in circulating blood, well known for their ability to form new vascular structures. Aging and various ailments such as diabetes, atherosclerosis and cardiovascular disease make EPCs vulnerable to decreasing in number, which affects their migration, proliferation and angiogenesis. Myocardial ischemia is also linked to a reduced number of EPCs and their endothelial functional role, which hinders proper blood circulation to the myocardium. The current study shows that an aminopyrimidine derivative compound (CHIR99021) induces the inhibition of GSK-3β in cultured late EPCs. GSK-3β inhibition subsequently inhibits mTOR by blocking the phosphorylation of TSC2 and lysosomal localization of mTOR. Furthermore, suppression of GSK-3β activity considerably increased lysosomal activation and autophagy. The activation of lysosomes and autophagy by GSK-3β inhibition not only prevented replicative senescence of the late EPCs but also directed their migration, proliferation and angiogenesis. To conclude, our results demonstrate that lysosome activation and autophagy play a crucial role in blocking the replicative senescence of EPCs and in increasing their endothelial function. Thus, the findings provide an insight towards the treatment of ischemia-associated cardiovascular diseases based on the role of late EPCs. 相似文献
90.
Ji Eun Lee Hoon Chae Park Hang Seok Choi Seung Yeon Cho Tae Young Jeong Sung Cheoul Roh 《Korean Journal of Chemical Engineering》2016,33(3):782-794
Numerical simulations were conducted using computational fluid dynamics to evaluate the effect of ventilation conditions on radon (222Rn) reduction performance in a residential building. The results indicate that at the same ventilation rate, a mechanical ventilation system is more effective in reducing indoor radon than a natural ventilation system. For the same ventilation type, the indoor radon concentration decreases as the ventilation rate increases. When the air change per hour (ACH) was 1, the indoor radon concentration was maintained at less than 100 Bq/m3. However, when the ACH was lowered to 0.01, the average indoor radon concentration in several rooms exceeded 148 Bq/m3. The angle of the inflow air was found to affect the indoor air stream and consequently the distribution of the radon concentration. Even when the ACH was 1, the radon concentrations of some areas were higher than 100 Bq/m3 for inflow air angles of 5° and 175°. 相似文献