Search

The damp-heat stability and photostability of solar cells were investigated depending on the ZnO fabrication methodology. Although the initial PCEs of the devices were similar, the ZnOs affected the solar cell performance after the aging process.

A strategy to obtain low Jd in OPDs from a material point of view is presented: fluorination of the electron donor unit in a donor–acceptor type conjugated polymer is an effective way to reduce the Jd of OPDs by suppressing the trap DOS.

A series of combustion tests was conducted to control and suppress the initiation of low-frequency instability (LFI) by using fuel inserts, through which a small step appeared gradually because of ...

To determine the suitability of the control performance of the VTVL system with hybrid rocket engine, simulations were done for the vertical and horizontal motion using various engine data. In the simulation, the thrust modulation characteristics of each engine were modeled with the same second-order transfer function in all cases. The results showed that the VTVL system with HRE showed better performance in terms of vertical motion error and touch down speed. In addition, this confirms the possibility for successful VTVL flight missions using HRE. In the next step, a better control algorithm and an efficient control technique will be attempted for developing the VTVL demonstrator.

The resonance of thermal lags of solid fuel with heat transfer oscillations in a boundary layer flow is the primary cause of low-frequency instability initiation in hybrid rocket combustion. A detailed study of two cases was conducted experimentally to investigate how the boundary layer is disturbed and leads to low-frequency instability (LFI); combustion with swirl injection and combustion with the frequency jump. The fluctuating boundary layer was successfully captured by visualizing images and proper orthogonal decomposition analysis was performed. The results show that swirl injection with an appropriate intensity substantially reduces the amplitudes of high frequency p’, and no boundary layer perturbation is found in the spectral analysis of mode 2, and Rayleigh index amplifications disappear. While the frequency jump occurs, the coupling status between p’ and q’ became weakly positive and the driving force disturbing the upstream flow was not made. As a result, oscillatory heat transfer was difficult to occur. Therefore, the appearance of boundary layer perturbation is the necessary precondition for the initiation of the low-frequency instability. And the resonance with the thermal lag characteristic leads to the occurrence of LFI.

CD4/CD8 T-cell lineage differentiation is a key process in immune system development; however, a defined regulator(s) that converts the signal from T-cell receptor and co-receptor complexes into lineage differentiation remains unclear. Here, we show that Twist2 is a critical factor in CD4/CD8 thymocyte differentiation. Twist2 expression is differentially regulated by T-cell receptor signaling, leading to differentiation into the CD4 or CD8 lineage. Forced Twist2 expression perturbed CD4+ thymocyte differentiation while enhancing CD8+ thymocyte differentiation. Furthermore, Twist2 expression produced mature CD8+ thymocytes in B2m-/- mice, while its deficiency significantly impaired CD8+ cells in MHC class-II-/- and TCR transgenic mice, favoring CD8 T-cell differentiation. During CD8 lineage differentiation, Twist2 interacted with Runx3 to bind to the silencer region of the ThPOK locus, thereby blocking ThPOK expression. These findings indicate that Twist2 is a part of the transcription factor network controlling CD8 lineage differentiation.

Perhydropolysilazane (PHPS), an inorganic polymer composed of Si-N and Si-H, has attracted much attention as a precursor for gate dielectrics of thin-film transistors (TFTs) due to its facile processing even at a relatively low temperature. However, an in-depth understanding of the tunable dielectric behavior of PHPS-derived dielectrics and their effects on TFT device performance is still lacking. In this study, the PHPS-derived dielectric films formed at different annealing temperatures have been used as the gate dielectric layer for solution-processed indium zinc oxide (IZO) TFTs. Notably, the IZO TFTs fabricated on PHPS annealed at 350 °C exhibit mobility as high as 118 cm

In this paper, a series of combustion tests using PMMA/O2 was conducted to examine the initiating characteristics of low frequency instability (LFI) in relation to the changes in both flow and combustion conditions. By selecting parameters such as the oxidizer mass flow rate, fuel grain length, and mixing ratio of mixture oxidizer composed of oxygen and nitrogen; combustion tests were conducted to vary the equivalence ratio in the combustion. This study further validated instability characteristics in connection with coupling behavior between the high frequency pressure and heat release oscillations in 500 Hz band. Based on the results, a combustion stability map was plotted and it shows that the initiation of LFI is contingent upon the satisfaction of specific conditions of flow and combustion. The results also confirmed that the initiation of LFI is highly linked to an establishment of a positive coupling between high frequency pressure and heat release oscillations. In addition, equivalence ratio was found to be a critical factor in the transition of coupling status between the two high frequency oscillations. For a given flow condition, the sole increase in equivalence ratio above a certain threshold resulted in the phase shift between the two oscillations leading to a positive coupling or vice versa.

A series of experimental tests was conducted to investigate the effect of swirl injection on the combustion instability in hybrid rocket using combustion visualization technique. As a result, swirl injection seems to modify two main physical processes responsible for the initiation of LFI. First one is the transition of coupling status between two fluctuations of combustion pressure (p') and heat release (q') of 500 Hz band. The transition of p' and q' to negative coupling seems to be a crucial modification for stabilizing the combustion. Another noticeable effect of swirl injection is the gradual increase in the peak frequency of pressure oscillation from its initial value of around 20 Hz–50 Hz band, which is caused by the thermal lag, as the swirl intensity increases. Also, POD (Proper Orthogonal Decomposition) analysis was done to understand flow response to the swirl injection near the fuel surface. The analysis of temporal behavior of mode 1 and 2 suggested that the swirl injection with proper intensity not only suppress the generation of p' of 500 Hz band but induces a shift of low frequency peaks of 20 Hz band by adjusting the turbulent structures in boundary layer. And the shift of low frequency peaks seems to be another contributing factor for combustion stabilization.

The occurrence of low-frequency instability (LFI) appears to be related to multiple interactions among many complex physical processes, such as vortex shedding, boundary-layer oscillation, and additional combustion in the post-combustion chamber. In this study, two combustion tests were conducted to suppress LFI and to examine which physical processes its occurrence was most sensitive. In the first test, two fuel inserts were used to modify the formation of a boundary layer, vortex shedding at the end of the fuel, and vortex impingement. In the second test, the fuel insert located at the front end was replaced with swirl injection. The first test was aimed at controlling and suppressing the initiation of LFI using fuel inserts, through which a small step appeared gradually due to differences in the regression rates of the two materials, i.e., polymethyl methacrylate and high-density polyethylene. The test results confirmed that (i) there are physical connections among several processes, such as the thermoacoustic coupling between p′and q′ and the oscillations of the upstream boundary flow, and (ii) LFI suppression is possible by disrupting or eliminating the connections among these physical processes. The second test was also aimed to control LFI while minimizing the deviation in combustion performance using proper swirl injection along with a fuel insert. Even when replaced by swirl injection, LFI suppression was still possible and showed reasonable combustion performance without causing too much deviation from the baseline in terms of the oxygen-to-fuel ratio and the fuel regression rate.

SummaryCognitive flexibility is an essential ability to adapt to changing environment and circumstances. NMDAR has long been implicated in cognitive flexibility, but the precise molecular and cellular mechanism is not well understood. Here, we report that astrocytes regulate NMDAR tone through Best1-mediated glutamate and D-serine release, which is critical for cognitive flexibility. Co-release of D-serine and glutamate is required for not only homosynaptic LTD but also heterosynaptic LTD, which is induced at unstimulated synapses upon release of norepinephrine and activation of astrocytic α1-AR during homosynaptic LTP. Remarkably, heterosynaptic LTD at unstimulated synapses during memory acquisition is required for later repotentiation LTP during reversal learning, laying a foundation for flexible memory and cognitive flexibility. Our study sheds light on the pivotal role of astrocytes in orchestrating multiple synapses during memory formation and determining the fate of consolidated memory to be retained as a flexible memory.HighlightsAstrocytes regulate NMDAR tone via Best1-mediated glutamate and D-serine releaseActivation of astrocytic α1-AR induces heterosynaptic LTD via NMDAR toneHeterosynaptic LTD is required for repotentiation LTP and spatial reversal learningAstrocytic regulation of NMDAR tone is critical for metaplasticity and flexible memory

We report the synthesis of composite interlayers by using alcohol-soluble polyfluorene-wrapped single-walled carbon nanotubes (ASP-wrapped SWNTs) and their application to the electron transport layer in efficient organic solar cells. The ASP enable the individual dispersion of SWNTs in solution. Impressively, ASP-wrapped SWNTs solutions are stable for 54 days, indicating very high dispersion stability. Using the ASP-wrapped SWNTs as a cathode interlayer on zinc oxide nanoparticles (ZnO NPs), 9.45% of power conversion efficiency (PCE) can be obtained in PTB7-th:PC71BM-based organic solar cells, which is mainly attributed to the improvement of the short circuit current. Performance enhancements of 18% and 17% were achieved compared to those of pure ZnO NPs and ASP on ZnO NPs, respectively. The improvement of solar cell performance originates from an increased internal quantum efficiency, balanced mobility between electrons and holes, and minimization of charge recombination.

Leptomeningeal metastasis (LM) has a poor prognosis and is difficult to diagnose and predict the response of treatment. In this study, we suggested that the monitoring of changes in the concentration of extracellular vesicles in cerebrospinal fluid could help diagnose or predict outcomes for LM. We measured nanoparticles in 472 human cerebrospinal fluid (CSF) from patients including LM with both Dynamic Light Scattering (DLS) and Nanoparticle Tracking Analysis (NTA) after two-step centrifugations. NTA revealed that the concentration of CSF nanoparticles was significantly increased in LM compared to other groups (2.80 &times, 108 /mL vs. 1.49 &times, 108 /mL, p &lt, 0.01). Changes in NTA-measured nanoparticles concentration after intra-CSF chemotherapy were further examined in 33 non-small cell lung cancer patients with LM. Overall survival was longer for patients with increased EV than the others (442 vs. 165 days, p &lt, 0.001). Markers of extracellular vesicles (CD9/CD63/CD81) significantly decreased in the EV-decreased group. MicroRNA-21 expression decreased in this favorable prognostic group, whereas it increased in the EV-decreased group. In conclusion, the elevated concentration of extracellular vesicles in cerebrospinal fluid in patients with LM may be a predictive marker for survival duration. Moreover, EV changes combined with microRNA-21 might be a biomarker for monitoring the efficacy of intracranial chemotherapy of LM in non-small cell lung cancer patients.

Organic photodetectors (OPDs) are attracting attention for use in flexible and portable electronic applications such as image sensors, remote sensing, optical communications, and medical sensors because of their strong photon responsivity in thin films over a broad range of wavelengths. In particular, the efficient photon-to-current conversion of OPDs under visible light allows their use in indirect X-ray detectors using scintillators to convert X-rays to visible light. The polymer poly(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2- b:4,5- b']dithiophene- co-5-(2-hexyldecyl)-1,3-bis(6-octylthieno[3,2- b]thiophen-2-yl)-4 H-thieno[3,4- c]pyrrole-4,6(5 H)-dione) (PBDTT-8ttTPD) shows strong absorption bands in the region of 500-650 nm, as well as high hole mobility, which provides excellent photoresponsivity and photon-to-current conversion efficiency. A p-n junction photodetector was fabricated by blending PBDTT-8ttTPD and [6,6]-phenyl C

The julolidine based interfacial modifier (IM-J) for cathode buffer layer following the "donor-acceptor" design concept with julolidine substituent as an electron donating moiety was incoporated to improve the surface properties of ZnO. Simple treatment of metal oxide type cathode buffer materials with organic interfacial modifier induces the enhanced photovoltaic performance and could effectively overcome several interfacial problems in inverted organic photovoltaic cells (I-OPVs). We studied on the coverage of IM-J on ZnO surface with variation of solution concentrations to reduce charge recombination and macroscopic phase separation. At the optimum condition, ZnO/IM-J (0.05 w/v%), IM-J significantly decreased the surface tension (46.1 mN/m) and improved surface morphology (RMS roughness: 0.61 nm). As a result, compared to the unmodified ZnO based device, the ZnO/IM-J based I-OPVs showed significantly improved power conversion efficiency (PCE) from 7.41 to 8.07% due to the increased photocurrent density (Jsc) and fill factor (FF). It is concluded that IM-J is one of the promising candidates for controlling electronic property of ZnO buffer layer in inverted organic photovoltaic cells. Also, our interfacial modified system can be utilized in other optoelectronic devices.

Small-bundled single-walled carbon nanotube (SSWCNT) nanocomposite films made with various small molecules were facilely fabricated using the micronizing mill process. Finely dispersed small molecules in the SSWCNT film can effectively reduce the in-plane thermal conductivity of the nanocomposite due to π-π interactions. Furthermore, the micronizing mill process ensures the uniform distribution of the small molecules and the SSWCNTs in the nanocomposite film without any damage or deformation of the SSWCNT structure. Moreover, the influence of the shape of the small molecules on the thermoelectric properties of SSWCNT nanocomposite was systematically investigated. The thermoelectric properties of the pyrene/SSWCNT nanocomposite were found to have been greatly improved by the planar pyrene molecules with a slightly increased electrical conductivity of 978.6 S cm−1 and a significantly decreased in-plane thermal conductivity of 13.5 W m-1 K-2. The evaluated ZT value of the pyrene/SSWCNT nanocomposite was 4.4 × 10−3 and is about 20 times higher than that of the pristine SSWCNT nanocomposite. A planar-type thermoelectric generator (TEG) consisting of 20 legs was also fabricated using this pyrene/SSWCNT nanocomposite. The TEG showed an open circuit voltage of 20 mV and a short circuit current of 350 μA, resulting in a maximum output power of 1.5 μW at ΔT = 20 °C.

The technology to record image information at high resolution is of great importance in the optical areas of applied physics and biochemical imaging, as well as in commercial imaging applications such as cameras and machine vision. Organic semiconductors are drawing interest as photodetecting materials for next-generation high-resolution image sensors (IS) owing to their excellent properties such as high absorption coefficient, and color tunability and cost-effective manufacturability. These advantages offer the potential to exceed the technical limitation of silicon-based IS. This article reviews the state-of-the-art technologies of materials and devices in solution-processed organic photodiodes (OPDs) to meet the demands for future high-resolution ISs, which involves challenges ranging from the absence of a fundamental understanding of OPDs to commercialization requirements. Further, this article overviews the progress in the industry as well as academic society. The various requirements and technologies for the development of color-filter-free OPDs with narrow-wavelength detection are also discussed. This review concludes with an outlook of advances in these materials and devices to open up new commercialization routes.