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We report on the characteristics of enhanced and balanced white-light emission from bi-directional organic light-emitting diodes (BiOLEDs) enabled by the introduction of micro-cavity effects. The insertion of an additional metal layer between the indium tin oxide anode and the hole transporting layer results in similar light output of our BiOLEDs in both top and bottom direction and in reduced distortion of the electroluminescence spectrum. Furthermore, we find that by utilizing MC effects, the overall current efficiency can be improved by 26.2% compared to that of a conventional device. (C) 2013 Optical Society of America

Characteristics of reattachment and blowout of laminar lifted flames in partially premixed jets of propane fuel have been investigated experimentally. As flow rate decreased from a lifted flame, liftoff height decreases nonlinearly and the flame reattached to a nozzle at a certain liftoff height. By using the similarity solutions for jets by taking into account the virtual origins for both velocity and concentration, it has been predicted that the flow velocity along a stoichiometric contour has a maximum value. From this velocity behavior, a flame reattachment can be successfully explained based on the balance between the propagation speed of a tribrachial flame and flow velocity. Predicted displacement speeds during reattachment and liftoff agreed well with experiment. With improved accuracy in the velocity and concentration solutions accounting the virtual origins, conditions at reattachment and blowout as functions of jet velocity, fuel mass fraction, axial distance, and nozzle diameter can be more accurately predicted compared to those without considering virtual origins.

We fabricated environmentally stable and transparent organic/oxide hybrid transistor on a glass substrate using the conventional photolithography. The obtained device, which was composed of an In-Ga-Zn-O active layer/soluble polyimide (KSPI) organic insulator, showed a mobility of 6.65 cm2/Vs, a subthreshold swing slope of 350 mV/decade, a threshold voltage (VT) of 3.10 V, and an on-off ratio of 3.9 × 109. The transistor also showed good uniformity characteristics and was found to be environmentally stable for 90 days under ambient conditions.

Steady-state and time-resolved photoluminescence spectra of poly[9,9-bis(2′-ethylhexyl)fluorene-2,7-diyl] and a copolymer of poly[9,9-bis(2′-ethylhexyl)fluorene-2,7-diyl-co-α-cyanostilbene-4,4′-diyl] were investigated. In THF, the copolymer exhibits the characteristic blue emission band of the homopolymer together with another emission band arising from chromophoric segments containing comonomer units. A total suppression of the homopolymer emission band in copolymer thin film demonstrates the efficient exciton migration and trapping into the segments containing comonomer units. Exciton migration and trapping in copolymer thin film gives rise to a red-shift in photoluminescence as compared with the homopolymer. Time-resolved photoluminescence results are also consistent with the facile exciton migration from fluorene polymer units to trapping sites composed of cyanostilbene comonomer units. The exciton trapping processes result in a red-shift in the emission spectrum with enhanced color stability in the copolymer relative to the homopolymer.

We report on the bias stability characteristics of transparent ZnO thin film transistors (TFTs) under visible light illumination. The transfer curve shows virtually no change under positive gate bias stress with light illumination, while it shows dramatic negative shifts under negative gate bias stress. The major mechanism of the bias stability under visible illumination of our ZnO TFTs is thought to be the charge trapping of photo-generated holes at the gate insulator and/or insulator/channel interface.

Porcine-specific obstacles in islet isolation frequently result from the low purity or contamination with exocrine tissues. We implemented a new technique involving as capsulation of islets with excess exocrine tissue as a beneficial material to address those difficulties. Pig islets were hand-picked as high purity (HI) or low purity (LO) islets containing significant amounts of exocrine tissue. We performed static (ST) or shaking (SK) cultures of HI and LO islets. Islet function was examined after 24 hours by a glucose challenge test. Insulin secretion into the culture media was continuously measured using ELISA during a 6-day culture period. Islet function after 24 hours exhibited better maintenance under SK than ST culture as assessed by a stimulation index. The ideal islet morphology was seen in LO islets at 3 days of SK culture with typical islet shapes of a smooth surface and a spherical configuration. In contrast, typical islet morphology was not observed in HI islets under SK culture; maintenance of typical spherical appearances was difficult. Insulin secretion from LO islets under SK culture was higher than under other conditions during the 6-day period. Under SK culture conditions, exocrine-encapsulated LO islets showed enhanced islet function by condensing loose islet aggregates into firm spheroids with native exocrine tissues as a natural scaffold.

We have prepared a series of cross-linkable oligo- and poly(dialkylfluorene)s by nickel(0)-mediated polymerization of 2,7-dibromo-9,9-dialkylfluorene (alkyl = n-hexyl) and 4-bromostyrene. The resulting fully soluble and processable, styryl-functionalized oligomers and polymers can be cross-linked via the vinyl end-groups by curing at 175−200 °C, consistent with the autopolymerization mechanism of styrene. These relatively mild conditions render the materials insoluble and enable multilayering of polymers in organic light emitting devices. At the same time, the electrical and/or optical properties of the cross-linked polymers are preserved and no deleterious species or undesirable byproducts are produced. Furthermore, the cross-linking allows control of the supramolecular ordering of the planarized rigid rod-type fluorene segments in the polymer backbone that leads to suppression of troublesome excimer/aggregate in the photo- and electrolumenescence.

Poly[2-(5-cyclohexylmethoxypentyloxy)-5-methoxy-1,4-phenylenevinylene] (PMCYHPV) was synthesized through dehydrohalogenation polymerization. This polymer shows good solubility in common organic solvents. The absorption and photoluminescence (PL) emission maxima of PMCYHPV are 497 nm and 590 nm, respectively. The electroluminescence (EL) properties of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and PMCYHPV were studied by means of the EL spectra, current-voltage characteristics, and EL power-current characteristics. The measured relative EL quantum efficiency of PMCYHPV is about 6 times higher than that of MEH-PPV. The EL enhancement of PMCYHPV originates from the reduction of non-radiative decay of excitons caused by better separation of the polymer chains due to the rigid cyclohexyl side group. Furthermore, we found that the PL quantum efficiency of PMCYHPV is 15% higher than that of MEH-PPV.

Poly(9,9-dialkylfluorene-2,7-diyl) derivatives end-capped with 2-fluorenyl, 9,9-di-n-hexyl-2-fluorenyl, and 9-fluorenone-2-yl substituents have been synthesized through Ni(0)-mediated polymerization. Absorption and emission spectra of these polymers were measured after annealing at elevated temperatures in air as a function of annealing time. The fluorescence stability of the polymers end-capped using 2-bromo-9,9-di-n-hexylfluorene was much better than for the polymers end-capped with 2-bromofluorene. The exceptional sensitivity of the luminescence of the polymers end-capped with 2-fluorenyl substituents to thermal annealing in air is rationalized by a combination of π-stacking and chemical oxidation of the end groups to fluorenones. The latter was demonstrated by the IR spectra of annealed films and comparison of the results with the absorption, emission, and IR spectra of the polymers deliberately end-capped using 2-bromo-9-fluorenone. This study is directed toward the investigation of color stability o...

We developed white OLED device with high power efficiency, in which blue and orange phosphorescent emitters were used. By introduction of multi-functional interlayer which has partial doping of orange dopant inside EBL, we report WOLEDs with peak external efficiencies up to (14.1% EQE, 31.3 Im/W) without light out-coupling technique. At 1000 cd/m2, the performance achieved was 11.9% EQE, 18.7 Im/W with CIE = (0.39, 0.44). We also found that WOLED performances are related with doping ratio of the orange dopant that was inserted inside EBL.

We synthesized [poly(2,5-bis(trimethylsilyl)-1,4-phenylenevinylene)] (BTMS-PPV) via two different precursor polymers, i.e., a water-soluble sulfonium and an organic soluble thiophenoxy precursor polymers, and compared their properties with each other. The thiophenoxy precursor polymer shows a good thermal stability and it is eliminated from 320 °C. BTMS-PPV film through the thiophenoxy precursor route shows a blue-shifted UV-visible absorption and PL emission spectra compared with those from the water-soluble precursor route. A single layer EL device fabricated with BTMS-PPV from the thiophenoxy precursor polymer as an emitting layer shows the threshold voltage of 20 V and the emission maximum at about 545 nm. The external quantum efficiency of the device is greater than 6.0 × 10−4 % photons per electron in air and room temperature condition.

PPV was sensitized by ethyl viologen which is well known as a good electron acceptor, to achieve efficient ionization of the excitons created by photoexcitation of PPV. PPV/ethyl-viologen composites were successfully prepared from PPV-precursor and ethyl-viologen because both compounds could be soluble in polar solvents such as methanol, water etc. We observed dramatic decrease of photoluminescence efficiency in the PPV/ethyl-viologen composite film as compared with PPV film. This is attributed to photoinduced electron transfer in PPV/ethyl-viologen composites and the efficient ionization of the excitons was occurred in this composite film. Time-resolved photoluminescence of composite films was also studied to obtain the information of this photoinduced electron transfer dynamics.

Light emitting properties of poly(2-fluoro-l,4-phenylenevinylene) (PFPV) were investigated by using steady-state and time-resolved photoluminescence spectroscopies, EL spectra and current-voltage c...

Organic LEDs (OLEDs) are light sources that do not produce excessive heat and do not contain toxic materials.1 The light emitted from OLEDs is UV-free and can therefore be used to illuminate biological substances without causing harmful effects. OLEDs are ultra-thin (about 150nm), have very low weight, and can be tailored to many formats. A specific type of OLED—a so-called transparent OLED (TOLED)—is bidirectional, i.e., it emits light from its top and bottom surfaces (see Figure 1).2–4 It is vital that all components in a TOLED are transparent so that the simultaneous top and bottom light emission can be achieved. To ensure transparency of TOLEDs, the thickness of their cathodes should not exceed 20nm. Transparent cathodes in TOLEDs usually consist of a multilayer metallic thin film.3, 4 However, limited light transmission through the cathode means that the efficiency of top emission is lower than that of the bottom emission. As such, the asymmetric structure of the light propagation causes different electroluminescence (EL) spectra for the top and bottom emissions from TOLEDs. To address the problem of asymmetry in the EL spectra, we designed a TOLED that uses a capping layer (CL), with a unique optical function.2 The use of the CL does not disturb the electrical characteristics of the device and therefore obviates the need to alter the stack structure. Our CL is an optical dielectric that can enhance the transmittance of the device and the top-emission efficiency. Including the CL on the cathode produces two interfaces, i.e., air/CL and CL/cathode. Due to the complexity of multilayer interference, it is difficult to establish a straightforward optical principle that achieves the EL spectral matching of bottom and top emissions in our TOLED. We achieve high transmittance and high top-emission efficiency by adjusting the CL thickness so that we created Figure 1. A schematic illustration of a typical transparent organic LED (TOLED). The capping layer and transparent cathode are key components in the device.

Pancreatic islets have been the focus of recent studies exploring the pathologic mechanisms of diabetes mellitus as well as more effective and radical treatments for this disease. Islet transplantation is a promising therapeutic strategy; however, isolation of pancreatic islets for this purpose has been challenging, because the technique is time consuming and technically difficult, and tissue handling can be variable. Pseudo-islets can be used as an alternative to naive islets, but require cellular sources or artificial materials. In this study, pancreas-derived cells were used to generate pseudo-islets. Because the pancreas is composed of a variety of cell types, namely α cells, β cells, δ cells, and other pancreatic cells that perform different functions, we used 3 different cell lines—NIT-1 (a β-cell line), α TC1 clone 6 (an α-cell line), and TGP52 (a pancreatic epithelial-like cell line)—which we cocultured in nonadhesive culture plates to produce hybrid cellular spheroids. These pseudo-islets had an oval shape and were morphologically similar to naive islets; additionally, they expressed and secreted the pancreatic hormones insulin, glucagon, and somatostatin, as confirmed by reverse-transcription polymerase chain reaction and enzyme-linked immunosorbent assay. The results demonstrate that pseudo-islets that mimic naive islets can be successfully generated by a coculture method. These artificial islets can potentially be used for in vitro tests related to diabetes mellitus, specifically, in drug discovery or for investigating pathology. Moreover, they can be useful for examining basic questions pertaining to cell-cell interactions and tissue development.

Mesenchymal stem cells (MSCs) are multipotent stromal elements that can differentiate into a variety of cell types. MSCs are good sources of therapeutic cells for degenerative diseases. For these reason, many researchers have focused on searching for other sources of MSCs. To obtain MSCs for clinical use requires surgery of the donor that therefore can induce donor morbidity, since the common sources at present are bone marrow and adipose tissues. In this study, we investigated the existence of MSCs in postoperative discarded tissues. Subacromial bursal tissues were obtained from the shoulders of 3 injured patients. The cells from the bursa tissues were isolated through treatment with collagenase. The isolated cells were then seeded and expanded by serial passaging under normal culture system. To evaluate MSC characteristics of the cells, their MSC markers were confirmed by mRNA and protein expression. Multipotent ability was assessed using differentiation media and immunohistochemistry. Cells from the bursa expressed MSCs markers-CD29, CD73, CD90, and PDGFRB (platelet-derived growth factor receptor-beta). Moreover, as to their multipotency, bursal cells differentiated into adipocytes (fat cells), osteocytes (bone cells), and chondrocytes (cartilage cells). In summary, we showed that MSCs could be generated from the subacromial bursa, which is medical waste after surgery.

Investigators conducting diabetes-related research have focused on islet transplantation as a radical therapy for type 1 diabetes mellitus. Pancreatic islet isolation, an essential process, is a very demanding work because of the proteolytic enzymes, species, treatment time, and individual difference. Replacement of primary isolated pancreatic islets must be carried out continuously for various in vitro tests, making primary isolated islets a useful tool for cell transplantation research. Hence, we sought to develop pseudoislets from commercial pancreas-derived cell lines. In this study, we used RIN-5F and RIN-m cells, which secrete insulin, somatostatin, or glucagon. To manufacture hybrid cellular spheroids, the cells were cultured under hanging drop plate and nonadhesive plate methods. We observed that hybrid cellular pseudoislets exhibited an oval shape, with sizes ranging from 590 to 1200 μm. Their morphology was similar to naive islets. Cell line pseudoislets secreted and expressed insulin, glucagon, and somatostatin, as confirmed by reverse transcriptase polymerase chain reaction, enzyme-linked immunosorbent assay, and immunohistochemistry analyses. Thus, the current artificially manufactured biomimetic pseudoislets resembled pancreatic islets of the endocrine system, appearing as cellular aggregates that secreted insulin, glucagon, and somatostatin. Enhanced immunoisolation techniques may lead to the development of new islet sources for pancreatic transplantation through this pseudoislet strategy.

Autologous chondrocyte transplantation (ACT) has been established to contribute cartilage regeneration over the past years; however, many obstacles need to be overcome. Recently, newer ACT technique involves cotransplantation of chondrocytes and biomaterial. Although various proposed intelligent biomaterials exist, many of them remain insufficient and controversial. In this study, we aimed to examine the effects of natural extracellular matrix (ECM) to the proliferation rate and differentiation on the chondrocytes. We first derived a natural ECM sheet from 10-μm-thick frozen sections of porcine knee cartilages. We then cultured the chondrocytes derived from a rabbit's knee on a dish precoated with the natural ECM. Then we assessed differentiation and chondrogenic potential of the cells compared with those grown in untreated culture dishes. We characterized the gene expression of chondrogenic markers, such as collagen type II, SOX-9, and aggrecan, as well as the level of ECM protein with the use of reverse-transcription polymerase chain reaction analysis. The cells cultured with the ECM sheet showed highest chondrogenic potential and differentiation. Therefore, we can induce good chondrogenesis by with the use of a natural ECM sheet on the culture dish. The readily available and easy-to-handle thin ECM sheets create an environment that promotes efficient cartilage regeneration. Our data suggest that this natural ECM scaffold improved the chondrogenic differentiation of the cells in vitro by providing a favorable microenvironment.

Autologous chondrocyte transplantation involves isolating chondrocytes from a patient's cartilage tissue. Storage conditions such as storage time and temperature are important for the quality of the isolated cells. However, few studies have focused on variables for optimum tissue preservation, and there is neither an established method for storing cartilage nor reliable reports on how different conditions affect the isolated chondrocytes. Therefore, in the present study, we stored cartilage in various preservation solutions, under different temperatures, and for varying durations and determined their effects on the characteristics and viability of isolated chondrocytes. We assessed chondrocyte viability with the use of a cell proliferation assay and determined their chondrogenic potential with the use of reverse-transcription polymerase chain reaction, enzyme-linked immunosorbent assay, and glycosaminoglycan assays. Our results demonstrated that cartilage tissue stored in a preservation medium composed of dimethyl sulfoxide, fetal bovine serum, and Dulbecco Modified Eagle Medium at a ratio of 1:2:7 (v/v) or stored with a commercially available preservation solution generated greater numbers of chondrocytes when the storage temperature was −80°C than when it was 4°C. The viability of isolated cells decreased with time at 4°C, whereas these values remained constant for tissues stored at −80°C. Our data suggest that an optimal method for preserving cartilage tissue is required to ensure the quality of cells used for transplantation.

The concern about the global climate change and the unstable supply of fossil fuels stimulate the research of the new energy source utilization and the efficient energy system design. As the interests on the future energy sources and renovating the conventional power plants grow, an efficient and widely applicable power conversion system is required to satisfy both requirements. S-CO2 cycle is considered as a promising candidate with the advantages of 1) relatively high efficiency in the modest temperature (450–750°C) region because of non-ideal properties near the critical point, 2) effectively reduced size of the total cycle with compact turbo-machines and heat exchangers, 3) potential for using in various applications with competitive efficiency and simple layout. The S-CO2 cycle was originally considered as an attractive candidate for the power conversion cycle of the next generation nuclear reactors. However, due to many benefits of the S-CO2 cycle, it is recently considered in other conventional and renewable energy system applications including fossil fuel power plant system, ship propulsion application, concentrated solar power system, fuel cell bottoming power cycle and so on. This paper will discuss about the design of S-CO2 cycle for the various energy system applications over different temperature range. Unlike a large size power plant which usually focuses more on maximizing the cycle efficiency, a small capacity energy system is seriously concerned about the total size of the cycle. In this manner, several preliminary S-CO2 cycle designs will be compared in terms of the efficiency and the physical size. Various layouts and components of S-CO2 cycle are compared to find the optimum cycle for each energy systems. The in-house codes developed by the KAIST research team are used to evaluate the various cycle performances and component preliminary designs. The obtained results will be compared to the conventional power conversion systems along with its implication to other existing designs.Copyright © 2013 by ASME

Supercritical carbon dioxide (S-CO2) Brayton cycle has gaining attention due to its compactness and high efficiency at intermediate temperature range of turbine inlet temperature. Thus, many research groups have been trying to develop their own S-CO2 Brayton cycle technology or component design technology. KAIST research team has been trying to develop a S-CO2 turbomachinery design methodology. As a part of this effort, In-House code KAIST_TMD (KAIST Turbomachinery Design) was developed based on open literatures. KAIST_TMD can reflect real gas effect since it uses precise equations and property database rather than ideal gas assumptions. Most special characteristic of KAIST_TMD is that KAIST_TMD can design both of radial type and axial type turbomachineries so it can compare performance of both radial and axial turbomachineries under the same operating conditions. KAIST_TMD provides geometry of turbomachinery and off design performance map also. This research team built a S-CO2 Pump Experiment facility (SCO2PE) to experience the S-CO2 loop operation and to perform validation and verification of KAIST_TMD in near future. Canned motor pump and shell and tube type heat exchanger were installed as the main components of SCO2PE. Main objectives of this paper are to present preliminary experimental data and share the operating experience and troubleshooting of the facility. Data analysis and detailed discussions about an experimental procedure and major issues when pump operates near the critical point will be presented in the paper. As a result, preliminary data were obtained that can be used for improving the facility to increase accuracy of the data for future validation and verification of KAIST_TMD for radial compressor/pump design.

Electrical modeling of the chemical gas sensors was successfully applied to TiO2 nanofiber gas sensors by developing an equivalent circuit model where the junction capacitance as well as the resistance can be separated from the comparable stray capacitance. The Schottky junction impedance exhibited a characteristic skewed arc described by a Cole–Davidson function, and the variation of the fit and derived parameters with temperature, bias, and NO2 gas concentration indicated definitely a physicochemical sensing mechanism based on the Pt|TiO2 Schottky junctions against the conventional supposition of the enhanced sensitivity in nanostructured gas sensors with high grain boundary/surface area. Analysis on a model Pt|TiO2|Pt structure also confirmed the characteristic impedance response of TiO2 nanofiber sensors.

A series of benzopyrano-2-isoxazoline compounds have been prepared efficiently by three-step synthesis from corresponding salicylaldehyde derivatives.

PPV derivatives containing electron-donating and electron-withdrawing group attached stilbene moiety, poly[2-methoxy-5-(2-phenylethenyl)-1,4-phenylenevinylene] (PMPEPV), poly[2-(2-phenyl ethenyl)-1,4-phenylenevinylene] (PPEPV), poly [2-(2-(4-cyanophenyl)ethenyl)-5-methoxy-1,4-phenylenevinylene] (PCEMPV) and poly [2-(2-(4-trifluoromethyl)phenyl)ethenyl-1,4-phenylenevinylene] (PFEMPV) were synthesized through a water-soluble precursor polymers, and their third-order nonlinear optical susceptibilities were determined by using third-harmonic generation measurement technique at 1907 nm, fundamental wavelength. The measured χ(3) values of PMPEPV, PPEPV, PCEMPV and PFEMPV were 2.1 |MX 10−12, 1.7 |MX 10−12, 1.2 |MX 10−12esu and 0.9 |MX 10−12esu, respectively.

The energy transfer in a blend of electroluminescent conjugated polymers, poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and conjugated−nonconjugated multiblock copolymers (CNMBC), was investigated. Energy transfer from CNMBC to MEH-PPV leads to the enhanced emission of MEH-PPV. Fluorescence decays also support this energy-transfer process, which is faster than radiative and nonradiative decays. PL and EL quantum efficiencies of the blended polymer were enhanced as the relative content of CNMBC was increased, and surprisingly, 500 times improved EL efficiency was observed for some blend ratios. These results provide further insight into the photophysics of conjugated polymers and the improvement of the electroluminescence quantum efficiency using the blended polymer systems.

Because the electrochromic (EC) performance significantly affects the diffusion of ions into the EC layer, EC layer thicknesses vary, ranging from approximately 100 nm to 400 nm. Their optimized and maximized EC performance in both optical contrast and color-switching behaviors are investigated as a function of EC layer thicknesses and applied bias voltages. Commercially available poly(3,4-ethylenedioxythiophene): poly(styrene-sulfonate) (PEDOT:PSS) is selected as the EC layer due to its environmentally friendly condition and expected reproducible uniformity. Among the four different thicknesses of the PEDOT:PSS layer fabricated, the ~200 nm thick PEDOT:PSS layer exhibits the highest optical contrast ratio at an applied bias voltage of + 3.0 V for the bleached state and - 3.0 V for the colored state. Moreover, through increasing the applied bias voltage slightly to + 3.5 V/- 3.5 V, the color-switching speed is also significantly improved from 10 s to 5 s for switching from the bleached state to the colored state.

Organic light-emitting diodes (OLEDs) have successfully entered mobile-phone display market and large-size OLED TVs have also been available by overcomming many technical obstacles. However, novel and innovative technologies are still required for flexible, transparent, and high-resolution displays. For example, augmented reaility (AR) and virtual reality (VR) have recently received peculiar attention and they need transparent and high-resolution displays with thousands of pixels per inch (PPI) to realize immersive displays. Top-emitting OLEDs (TEOLEDs) have an advantage for high-resolution displays due to their large aperture ratio. Top electrode is one of crutial factors to decide the performance of TEOLEDs as well as transparent OLEDs (TOLEDs) and should have high transmittance, low reflectance, and high conductivity. There are many candidate materials for transparent conductive electrodes but the top electrode choices are limited, because top electrode materials should not damage the organic layers of OLEDs during the deposition process. Most TEOLEDs and TOLEDs that have been reported so far utilize semitransparent thin metal top electrode owing to their compatibility with OLED fabrication process, but thin metal top electrodes without sophisticated optical design degrade the efficiency and color quality [1]. Indium-tin-oxide (ITO) has optically good properties, but it needs sputtering and high temperature precess which leads to damage of organic layers in OLEDs [2]. Carbon-based materials suchs as carbon nanotubes (CNT), graphene, and conducting polymers are lately used as transparent conductive top electrodes in OLEDs and polymer solar cells because of their high trasmittance and low reflectance [3-6]. Most devices show optically good but electrical poor properties due to low conductivity of carbon-based non-metal transparent conductive materials. To apply carbon-based electrodes to large-size devices, their electrical conductivity should be improved. In this work, we make carbon-based transparent conductive electrode films and enhace the conductivity of the film by embedding silver mesh electrodes. The film showed high transmittance and low reflectance in visible spectral region in spite of existence of metal auxiliary wire. We have fabricated small molecule-based transparent OLEDs with these electrode films as top electrodes using a dry lamination technique and inverted structure which has cathodes on the substrate is employed because the conducting polymer has high work function that is suitable for an anode instead of a cathode. The device exhibited low driving voltage with high transmittance. In addition, we have demonstrated a 4 cm x 4 cm transparent segment panel with silver mesh embedded conducting polymer top electrodes. We also investigated color shift of white TEOLEDs with conducting polymer top electrodes depending on viewing angle. Acknowledgment This work was supported by Institute for Information & communications Technology Promotion(IITP) grant funded by the Korea government(MSIP) (B0101-16-0133, The core technology development of light and space adaptable energy-saving I/O platform for future advertising service) References 1. S.-F. Hsu, C.-C. Lee, S.-W. Hwang, C. H. Chen, Appl. Phys. Lett., 86, 253508 (2005). 2. H. Kanno, Y. Sun, S. R. Forrest, Appl. Phys. Lett., 86, 263502 (2005). 3. Z. Yu, Z. Liu, M. Wang, M. Sun, G. Lei, Q. Pei, J. Photonics Energy, 1, 011003 (2011). 4. J.-H. Chang, W.-H. Lin, P.-C. Wang, J.-I. Taur, T.-A. Ku, W.-T. Chen, S.-J. Yan, C.-I. Wu, Sci. Rep., 5, 9693 (2015). 5. J. T. Lim, H. Lee, H. Cho, B.-H. Kwon, N. S. Cho, B. K. Lee, J. Park, J. Kim, J.-H. Han, J.-H. Yang, B.-G. Yu, C.-S. Hwang, S. C. Lim, J.-I. Lee, Sci. Rep., 5, 17748 (2015). 6. S. K. Hau, H.-L. Yip, J. Zou, A. K.-Y. Jen, Org. Electron., 10, 1401 (2009).

Asymmetrically disubstituted poly(2-methoxy-5-methyl-1,4-phenylenevinylene) (PMMPV) and a series of poly(1,4-phenylenevinylene-co-2-methoxy-5-methyl-1,4-phenylenevinylene)s (poly(PV-co-MMPV)) were synthesized through a water-soluble precursor route. These polymers were characterized using UV-visible, FT-IR spectroscopy, and a DSC, TGA thermal analyzer. The electrical conductivities of the polymers were investigated by the four-in-line method at room temperature. A PMMPV film can be stretched up to 5 times and doped with FeCl 3 and I 2 to give electrical conductivities of 27 and 7.4 S/cm, respectively, along the drawn direction. In copolymers, as the content of the MMPV unit increases, the electrical conductivity steadily increases. The X (3) (-3ω ; ω, ω, ω) value of PMMPV was determined by the third harmonic generation (THG) technique at 1907 nm, the fundamental wavelength. The measured X (3) value was 7.5 x 10 -12 esu.

Asymmetrically disubstituted poly(2-isopropoxy-5-methoxy-1,4-phenylene-vinylene), PIMPV, was prepared in thin films via organic-soluble precursor polymer method. These polymer films could be easily stretched up to 7 times, and the drawn films of the PIMPV could be doped with FeCl3 and I2 to give conductivities of 26.9 and 11.3 Scm-1, respectively. The third-order nonlinear optical susceptibility of the polymer was determined using third harmonic generation(THG) method at 1907 nm, fundamental wavelength. Measured χ(30) (-3α: α, α, α) value was 3.7x10-12 esu.

Area-selective external light extraction films based on wrinkle structured films were applied to large transparent organic light-emitting diodes (TOLEDs) with auxiliary metal buses. To be specific, on the external surface of the glass, we selectively formed a wrinkle structured film, which was aligned to the auxiliary metal electrodes. The wrinkle-structured film was patterned using a photo-mask and UV curing, which has the same shape of the auxiliary metal electrodes. With this area-selective film, it was possible to enhance the external quantum efficiencies of the bottom and top emissions TOLEDs by 15.7% and 15.1%, respectively, without significant loss in transmittance. Widened angular luminance distributions were also achieved in both emissions directions. (C) 2016 Optical Society of America

An optical functional film applicable to various lighting devices is demonstrated in this study. The phase separation of two immiscible polymers in a common solvent was used to fabricate the film. In this paper, a self-organized lens-like structure is realized in this manner with optical OLED functional film. For an OLED, there are a few optical drawbacks, including light confinement or viewing angle distortion. By applying the optical film to an OLED, the angular spectra distortion resulting from the designed organic stack which produced the highest efficiency was successfully stabilized, simultaneously enhancing the efficiency of the OLED. We prove the effect of the film on the efficiency of OLEDs through an optical simulation. With the capability to overcome the main drawbacks of OLEDs, we contend that the proposed film can be applied to various lighting devices.

Spirobifluorene derivative, which is useful for obtaining small molecule or polymer blue light emitting materials, has been prepared. To improve the solubility of final materials, long alkoxy side chains were introduced to spirobifluorene moiety. Coupling reaction with biphenyl led to small molecule blue light emitting material. A polymer blue light emitting material was obtained through Ni(0) mediated polymerization. Using vacuum deposition and spin coating methods, small molecule and polymer light emitting devices were fabricated and their device characteristics were investigated. In this paper, the detailed preparation methods of small molecule and polymer materials, and the device characteristics will be discussed.

Many obstacles beset islet transplantation, particularly insufficient tissue mass. Previously, we reported production of pseudo-islets. In addition, there have been reports in which coculture with pancreatic islet and bone marrow mesenchymal stem cells (BMSCs) demonstrated positive effects on pancreatic islet function. The purpose of this study was to perform morphologic and functional evaluations of pancreatic pseudo-islets cocultured with BMSCs. Pancreatic endocrine cells (PECs) were collected with a previously reported method; bone marrow was aspirated from the rat femur. Subsequently, PECs and BMSCs cocultured at high density on low-cell-binding culture dishes kept suspended by shaking. The functionality and characteristics of the mixed cell complexes were evaluated by glucose challenge, insulin enzyme-linked immunosorbent assay, reverse-transcription polymerase chain reaction, and immunohistochemistry. Through expansion for 2 weeks in continuous culture passages, ∼1 million PECs were recovered after aggregation. They presented spherical shapes and sizes similar to naive islets, according to phase-contrast microscopy. The spheroid aggregates of pancreatic islet cells and BMSCs showed fortified functions and maintained viability. In conclusion, PECs served as a cell source for pseudo-islets, which were both morphologically and genetically similar to naive islets. We also suggest a manufacturing method for mixed cellular complexes from 2 different origins that can improve secretion ability and cell differentiation.

Over the years, cardiovascular diseases continue to increase and affect not only human health but also the economic stability worldwide. The advancement in tissue engineering is contributing a lot in dealing with this immediate need of alleviating human health. Blood vessel diseases are considered as major cardiovascular health problems. Although blood vessel transplantation is the most convenient treatment, it has been delimited due to scarcity of donors and the patient’s conditions. However, tissue-engineered blood vessels are promising alternatives as mode of treatment for blood vessel defects. The purpose of this paper is to show the importance of the advancement on biofabrication technology for treatment of soft tissue defects particularly for vascular tissues. This will also provide an overview and update on the current status of tissue reconstruction especially from autologous stem cells, scaffolds, and scaffold-free cellular transplantable constructs. The discussion of this paper will be focused on the historical view of cardiovascular tissue engineering and stem cell biology. The representative studies featured in this paper are limited within the last decade in order to trace the trend and evolution of techniques for blood vessel tissue engineering.

In this work, we demonstrate fully uniform blue fluorescence graphene anode OLEDs, which have an emission area of 10u7 mm 2 . Catalytically grown multilayered graphene films have been used as the anode material. In order to compensate the current drop, which is due to the graphene’s electrical resistance, we have furnished metal bus lines on the support. Processing and optical issues involved in graphene anode OLED fabrications are presented. The fabricated OLEDs with graphene anode showed comparable performances to that of ITO anode OLEDs. Our works shows that metal bus furnished graphene anode can be extended into large area OLED lighting applications in which flexibility and transparency is required.

The present numerical study focuses on the predictions of thermal mixing in a T-junction using two types of approaches; the Large Eddy Simulation (LES) and the Unsteady RANS technique. The numerical predictions are compared to the experimental reference data of Westin et al. (2008). Beforehand, the LES using the commercial code Star-CD are across validated with the open source Code_Saturne in a simple academic channel flow case at Re=395. For this case, both codes predictions are found in a satisfactory agreement with the DNS data which provides sufficient evidence, from a numerical dissipation related issues point of view, that any of these codes can be used for the LES runs of the more complex T-Junction test case. For the later, in agreement with previous findings reported in the open literature the LES approach is found capable to mimic correctly the flow behavior and to provide valuable instantaneous data needed for the thermal stress fatigue analysis for instance. The URANS technique on the other hand, even with an advanced non-linear eddy-viscosity model, is not only incapable of predicting correctly the mean variables, but also largely dumping the flow turbulence.

The supercritical CO2(S-CO2) Brayton Cycle is gaining attention due to its high thermal efficiency at relatively low turbine inlet temperature and compactness of turbomachineries. For designing turbomachineries of the S-CO2 Cycle, however, most of existing codes based on ideal gas assumption are not proven yet to be accurate near the supercritical condition. Furthermore, many of existing design computer programs usually focuses on a specific type of turbomachinery, e.g. axial or radial, which makes hard to compare performance of both types at the same design condition. Since both axial and radial types of turbomachineries were pointed out as an equally possible candidate for the S-CO2 Brayton cycle, in order to compare and determine the best effective type of turbomachinery requires considering both types under the same design conditions. Taking into consideration of these facts, some modifications to the conventional design methodology of gas cycle turbomachinery are necessary to design a turbomachinery for the S-CO2 cycle. Especially, a modified design method should consider non-linear property variation of CO2 near the critical point to obtain an accurate result. Thus, the modified design method for the S-CO2 Brayton cycle turbomachineries is suggested in this paper and the method was implemented in the in-house code. In addition, some preliminary results will be discussed with the plan for validation and verification of the code.

We are successful to lit the OLED lighting panel through the magnetically coupled wireless power transmission technology. For the wireless power transmission, we used the operation frequency 932 kHz, specially designed double spiral type transmitter, small and thin receiver on the four layered printed circuit board, and schottky diodes for the full bridge rectifier. Our white OLED is a hybrid type, in which phosphorescent and fluorescent organics are used together to generate stable white color. The total efficiency of power transmission is around 72 %.

Introduction Although Islet cell isolation and culture have been well developed, there has been little progress to prolong transplanted islet sruvival. Hepatic ischemia and insufficient neovascularization of islets are considered to be the barriers to long-term survival, Hepatocytes that survive ischemic injury have been reported to protect themeslves and regenerate using the IL-6 interleukin 6 and STAT3 pathways. Materials and Methods The hepatocellular carcinoma (Hep-G2) cell line preconditioned for 0, 2, 4, 6, and 24 hours in a hypoxic chamber, was cocultured with rat insulin-secreting celline (RIN-5F) cells. We measured cell viabilities, insulin secretion, and p-STAT3, IL-6, and NF-κB levels. Results Cocultured Hep-G2 and RIN-5F cells aggregated to form spheroids. Viabilities of Hep-G2 cells were no different after various ischemic preconditioning times, but insulin secretion increased in a time-dependent fashion with preconditioning. Western blotting showed p-STAT3, NF-κB, and IL-6 levels to increase with preconditioning time. Conclusion The IL-6/STAT3 pathway of Hep-G2 cells after ischemic injury showed beneficial effects on insulin secretion of RIN-5f cells cocultured with themselves.

Background Like all mammalian cells, normal adult chondrocytes have a limited replicative life span, which decreases with age. To facilitate the therapeutic use of chondrocytes from older donors, a method is needed to prolong their life span. Methods We transfected chondrocytes with hTERT or GRP78 and cultured them in a 3-dimensional atelocollagen honeycomb-shaped scaffold with a membrane seal. Then, we measured the amount of nuclear DNA and glycosaminoglycans (GAGs) and the expression level of type II collagen as markers of cell proliferation and extracellular matrix formation, respectively, in these cultures. In addition, we allografted this tissue-engineered cartilage into osteochondral defects in old rabbits to assess their repair activity in vivo. Results Our results showed different degrees of differentiation in terms of GAG content between chondrocytes from old and young rabbits. Chondrocytes that were cotransfected with hTERT and GRP78 showed higher cellular proliferation and expression of type II collagen than those of nontransfected chondrocytes, regardless of the age of the cartilage donor. In addition, the in vitro growth rates of hTERT- or GRP78-transfected chondrocytes were higher than those of nontransfected chondrocytes, regardless of donor age. In vivo, the tissue-engineered cartilage implants exhibited strong repairing activity, maintained a chondrocyte-specific phenotype, and produced extracellular matrix components. Conclusions Focal gene delivery to aged articular chondrocytes exhibited strong repairing activity and may be therapeutically useful for articular cartilage regeneration.

Poly[(2-(2-(4-cyanophenyl)ethenyl)-5-methoxy-1,4-phenylene)vinylene] (PCEMPV) and a series of copolymers containing 1,4-phenylenevinylene (PV) units were synthesized through a water-soluble precursor route, and their electrical and second- and third-order nonlinear optical properties were studied. The PCEMPV films could not be doped with I 2 but could be doped with FeCl 3 to show an electrical conductivity of 5.0×10 -3 S/cm. The conductivities of FeCl 3 -doped copolymer films ranged from 8.0×10 -3 to 6.5 S/cm depending on their copolymer compositions

A series of poly (2-alkoxy-1,4-phenylenevinylene)'s was synthesized by water-soluble precursor method. In this paper, three poly(1,4-phenylenevinylene) (PPV) derivatives were included, poly (2-methoxy-1,4-phenylenevinylene), poly(2-butoxy-1,4-phenylenevinylene) and poly (2-dodecyloxy-1,4-phenylenevinylene). These polymers were characterized using UV-visible, FT-IR spectroscopy and DSC, TGA thermal analyzer. The third order nonlinear optical susceptibilities of the polymers were determined using third harmonic generation (THG) method at 1907 nm, fundamental wavelength. Measured x (3) values are 10−11–10−12 esu order and as the side chain length is increased, the x (3) value is decreased because of the side chain effect on conjugation and of volume fraction.

Organic thin-film transistors using the pentacene as an active electronic material have shown the mobility of 0.8 cm2/V s and the grains larger than 1 μm. To study the characteristics of electronic charge concentrations and the interface traps of the pentacene thin films, the capacitance properties were measured in the metal/insulator/organic semiconductor structure device by employing the capacitance–voltage and deep-level transient spectroscopy (DLTS) measurements. Based on the DLTS measurements, the concentrations and the energy levels of hole and electron traps in the obtained pentacene films were formed to be approximately 4.2×1015 cm−3 at Ev+0.24 eV, 9.6×1014 cm−3 at Ev+1.08 eV, 6.5×1015 cm−3 at Ev+0.31 eV and 2.6×1014 cm−3 at Ec−0.69 eV.

Autologous chondrocyte implantation (ACI) is the treatment of choice for osteoarthritis. However, to regenerate articular cartilage using this method, the procedure paradoxically demands that the cell source of the articular chondrocytes (ACs) for ex vivo expansion be from the patient's own healthy cartilage, which can result in donor site morbidity. Accordingly, it is essential to develop a substitute for AC. In the present study, we investigated whether synovium-derived cells (SYs) could be used as a partial replacement for ACs in ACI. ACs and SYs from the knees of rabbits were isolated and cultured, and the growth rates of the cells were compared. To manufacture the cellular transplants, we developed a high-density suspension-shaking culture method (HDSS), which circulates the cells in culture media, promoting self-assembly of scaffold-free cellular aggregates. ACs and SYs were mixed in various ratios using HDSS. Injectable cellular transplants were harvested and transplanted into full-thickness osteochondral defects. Simultaneously, histological evaluations were conducted with toluidine blue and safranin O, and immunohistochemistry of collagen type I and II was conducted. Gene expression to evaluate chondrocyte-specific differentiation was also performed. We successfully prepared a large quantity of spheroids (spheroidal cell aggregates) in a short time using mixed ACs and SYs, for all cellular composition ratios. Our data showed that the minimal therapeutic unit for the transplants contributed to in situ regeneration of cartilage. In summary, SYs can be used as a replacement for ACs in clinical cases of ACI in patients with broad areas of osteoarthritic lesions.

We have developed the highly efficient OLEDs using the embossed glass substrate and the low yellowing TiO 2 /Epoxy nano composite layer. The nano composite can be applied to a scattering layer and a planarization layer on an embossed glass. The TiO 2 /Epoxy nano composite was effective for increasing the light extraction efficiency of OLEDs, however the yellowing degraded the luminous efficacy seriously. The luminous efficacy of the OLED with the nano composite layer on the embossed glass was 21.0 lm/W at 1000 cd/m2 and it increased by 36% compared to the conventional OLED.

Background There have been many efforts to find methods to increase insulin production by islets or modified cells. Commercially available established cell lines can be a good source of artificial islets. We manufactured sphere-shaped cell clusters composed of insulin-secreting cells from the commercially available RIN-5F cell line. Methods To generate artificial islets with insulin-secretion functions, we used the RIN-5F cell line. When cells cultured in RPMI-1640 medium containing 10% fetal bovine serum reached near confluency, they were trypsinized for suspension culture at high density, using a horizontal shaker. The cells were maintained for 5 days under 5% CO2 with humidification. Next, the media from the RIN cell spheroid culture was collected over 5 consecutive days to test for insulin secretion. Results Spheroids of artificial islets exhibited an oval shape with an approximate size of 94.13 ± 20.41 μm on day 5 during the shaking culture. Abnormal outgrowth of spheroids was not observed. Terminal deoxynucleotidyl transferase–mediated dUTP nick-end labeling–positive cells were not detected among the overall spheroids, including the core position. Insulin secretion, measured by enzyme-linked immunosorbent assay, was well maintained in the culture media over 5 days after spheroid formation. Conclusion This result suggested that a culture method with shaking can be applied to commercially available established cell lines to generate artificial islets, which might be used for a bioartificial pancreas.

A series of benzopyrano-2-isoxazoline compounds have been prepared efficiently by three-step synthesis from corresponding salicylaldehyde derivatives.