DGIST 전자도서관

Avian mud nest architecture by self-secreted saliva

2021-01Proceedings of the National Academy of Sciences of the United States of America, v.118, no.3, pp.e201850911

Mud nests built by swallows (Hirundinidae) and phoebes (Sayornis) are stable granular piles attached to cliffs, walls, or ceilings. Although these birds have been observed to mix saliva with incohesive mud granules, how such biopolymer solutions provide the nest with sufficient strength to support the weight of the residents as well as its own remains elusive. Here, we elucidate the mechanism of strong granular cohesion by the viscoelastic paste of bird saliva through a combination of theoretical analysis and experimental measurements in both natural and artificial nests. Our mathematical model considering the mechanics of mud nest construction allows us to explain the biological observation that all mud-nesting bird species should be lightweight. © 2021 National Academy of Sciences. All rights reserved.

New Cost-Effective Halide Solid Electrolytes for All-Solid-State Batteries: Mechanochemically Prepared Fe3+-Substituted Li2ZrCl6

ACCEPTAdvanced Energy Materials

Owing to the combined advantages of sulfide and oxide solid electrolytes (SEs), that is, mechanical sinterability and excellent (electro)chemical stability, recently emerging halide SEs such as Li3YCl6 are considered to be a game changer for the development of all-solid-state batteries. However, the use of expensive central metals hinders their practical applicability. Herein, a new halide superionic conductors are reported that are free of rare-earth metals: hexagonal close-packed (hcp) Li2ZrCl6 and Fe3+-substituted Li2ZrCl6, derived via a mechanochemical method. Conventional heat treatment yields cubic close-packed monoclinic Li2ZrCl6 with a low Li+ conductivity of 5.7 × 10−6 S cm−1 at 30 °C. In contrast, hcp Li2ZrCl6 with a high Li+ conductivity of 4.0 × 10−4 S cm−1 is derived via ball-milling. More importantly, the aliovalent substitution of Li2ZrCl6 with Fe3+, which is probed by complementary analyses using X-ray diffraction, pair distribution function, X-ray absorption spectroscopy, and Raman spectroscopy measurements, drastically enhances the Li+ conductivity up to ≈1 mS cm−1 for Li2.25Zr0.75Fe0.25Cl6. The superior interfacial stability when using Li2+xZr1−xFexCl6, as compared to that when using conventional Li6PS5Cl, is proved. Furthermore, an excellent electrochemical performance of the all-solid-state batteries is achieved via the combination of Li2ZrCl6 and single-crystalline LiNi0.88Co0.11Al0.01O2. © 2021 Wiley-VCH GmbH

Quantitative Assessment Method of Image Stitching Performance Based on Estimation of Planar Parallax

2021-01IEEE Access, v.9, pp.6152 - 6163

While parallax-tolerant image stitching is a relatively mature field, the performances of image stitching methods have been assessed subjectively and qualitatively. These methods primarily provide the stitched image itself to demonstrate the performance, rather than quantitative data. Although several objective assessment methods have been proposed for quantifying the quality of stitched images, only the stitched output images have been analyzed, without considering the parallax level in each input image. We propose a method for quantifying the parallax level of the input images and clustering them accordingly. This facilitates a quantitative assessment of the various stitching methods for each parallax level. The parallax levels of the images are grouped based on the magnitude and variation in the planar parallax, as estimated with the proposed metric using matching errors and patch similarity. The existing image stitching methods are compared experimentally in terms of the residual misalignment errors, based on 73 pairs of different levels of parallax images originally classified in this study. Among the existing methods, the elastic local alignment method exhibits the least error. The shape-preserving half-projective method produces a larger misalignment error, but creates a natural panorama with less geometric distortion. We introduce a quantitative assessment method for considering the parallax of input images in image stitching methods. It can aid in specifying their performances, and in finding an appropriate method depending on the parallax level of the input images.

자가구동형 전자소자 구현을 위한 에너지 발전/저장 융합 기술 동향

2018-11전기화학회지, v.21, no.4, pp.68 - 79

최근 늘어나는 배터리 수요를 대처하기 위하여 배터리를 대체하거나 배터리의 구동시간을 늘리기 위한 방법으로 제시되고 있는 에너지 발전소자와 에너지 저장소자의 융합연구는 에너지 관련 기술분야에서 가장 관심받고 있는 분야중 하나이다. 본 리뷰논문에서는 물리에너지 발전소자의 최근 연구동향과 함께 에너지 발전소자와 저장소자의 융합연구 동향을소개하고자 한다. 먼저, 물리에지를 전기에너지로 변환하는 압전 특성과 마찰대전 특성을 이용한 에너지 발전소자 관련 연구동향을 소개한다. 또한 압전/마찰대전 에너지 발전소자와 에너지 저장소자의 융합 연구동향을 소개한다. 특히 자가충전 에너지소자의 물리에너지를 전기화학적 에너지로 변환하는 새로운 접근방법을 소개하고자 한다. Currently, hybridization of energy generator and storage devices is considered to be one of the most important energy-related technologies due to the possibility of replacing batteries or extending the lifetime of a batteries in accordance with increasing battery demand. This review aims to describe current progress on the mechanical energy generator and hybridization of energy generator and energy storage devices for self-powered electronics. First, the research trends related to energy generation devices using piezoelectric and triboelectric effect that convert physical energy into electric energy is introduced. In addition, integration of energy generators and energy storage devices is introduced. In particular, self-charging energy cells provide an innovative approach to the direct conversion of mechanical energy into electrochemical energy to decrease energy conversion loss.

Post-modified FAU zeolites as efficient catalysts for the synthesis of coumarins

ACCEPTCatalysis Today

Herein, the effect of various treatments subjected to FAU zeolites to introduce mesoporosity has been examined on their efficiency as catalyst in the cyclisation of O-aryl 3-arylpropynoic acid ester to its corresponding coumarin. The addition of bio-sourced lignin residues in the alkaline desilication treatment induced the generation of supplementary mesoporosity, thus offering an optimal micro- and mesopores combination with respect to targeted activity and selectivity. The so-called bio-sourced secondary template (BSST) concept in the design of zeolite-based catalysts could be assessed. The use of renewable wood feedstocks can therefore be a valuable strategy for the zeolite post-modification, thus for the design of porous zeolite catalysts. © 2020 Elsevier B.V.

Deubiquitinase OTUD5 is a positive regulator of mTORC1 and mTORC2 signaling pathways

ACCEPTCell Death and Differentiation

The mammalian Target of Rapamycin (mTOR) pathway regulates a variety of physiological processes, including cell growth and cancer progression. The regulatory mechanisms of these signals are extremely complex and comprise many feedback loops. Here, we identified the deubiquitinating enzyme ovarian tumor domain-containing protein 5 (OTUD5) as a novel positive regulator of the mTOR complex (mTORC) 1 and 2 signaling pathways. We demonstrated that OTUD5 stabilized β-transducin repeat-containing protein 1 (βTrCP1) proteins via its deubiquitinase (DUB) activity, leading to the degradation of Disheveled, Egl-10, and pleckstrin domain-containing mTOR-interacting protein (DEPTOR), which is an inhibitory protein of mTORC1 and 2. We also showed that mTOR directly phosphorylated OTUD5 and activated its DUB activity. RNA sequencing analysis revealed that OTUD5 regulates the downstream gene expression of mTOR. Additionally, OTUD5 depletion elicited several mTOR-related phenotypes such as decreased cell size and increased autophagy in mammalian cells as well as the suppression of a dRheb-induced curled wing phenotype by RNA interference of Duba, a fly ortholog of OTUD5, in Drosophila melanogaster. Furthermore, OTUD5 knockdown inhibited the proliferation of the cancer cell lines with mutations activating mTOR pathway. Our results suggested a positive feedback loop between OTUD5 and mTOR signaling pathway. © 2020, The Author(s), under exclusive licence to ADMC Associazione Differenziamento e Morte Cellulare.

End-To-End Reliability of Satellite Communication Network Systems

ACCEPTIEEE Systems Journal, pp.1 - 11

Satellite communication networks with onboard processing (OBP) satellites can provide high-speed data transmission rates and global service coverage with reduced propagation delays. This article proposes a means of analyzing the quantitative reliability of the satellite communication network systems. First, we identify the four major factors that affect the quality of network services: the OBP states, uplink channels, downlink channels, and uplink packet collision losses. Based on these four factors, a Markov model is derived to analyze the probability distributions of various network states. Analytic results show the network reliability with respect to the OBP structures and space radiation environments. The relationship between network reliability and throughput according to the packet traffic load is also quantitatively analyzed. Finally, based on the developed model, a method is suggested for iteratively updating the reliability distribution of network systems affected by changes in the four factors as well as network access time changes. The numerical results show an indication of the satellite network reliability to provide references whether adjusted elements of the four factors are eligible to sustain reliable end-to-end services.

Eliminating Background Noise for STED Super-Resolution Microscopy Using Polarization Switching

2019-02Biophysical Journal, v.116, no.3, pp.24A - 24A

Stimulated emission depletion (STED) super-resolution microscopy (or nanoscopy) offers significant enhancement of optical resolution compared to conventional microscopy. To achieve resolution beyond the diffraction-limit, STED nanoscopy uses orders of magnitude (roughly ∼10∧5) more photons than the conventional confocal microscopy. Those additional ‘STED’ photons, which are designed to deplete the fluorescence at the periphery of focus, can induce unintended background noise. Increased low spatial frequency background noise decreases the signal-to-background ratio (SBR) and deteriorates the image quality by masking the high spatial frequency, super-resolved signal. Here, we report a simple and easy-to-implement method, which we call polarization switching STED (psSTED), that can efficiently eliminate the low spatial frequency background appearing in STED images. In psSTED, we switch the STED beam polarization between two different circularly polarized states to record a regular STED image and a background noise image. A simple, unambiguous subtraction process between these two images accomplishes a background-free super-resolved image. With both simulation and experimentation, we demonstrate psSTED works universally for different STED conditions. Finally, we compare the performance of psSTED with other state-of-the-art background subtraction methods and highlight its capability of efficient background suppression with a much simpler hardware implementation.

Blockers of Wnt3a, Wnt10a, or beta-Catenin Prevent Chemotherapy-Induced Neuropathic Pain In Vivo

ACCEPTNeurotherapeutics

Although chemotherapy is a key cancer treatment, many chemotherapeutic drugs produce chronic neuropathic pain, called chemotherapy-induced neuropathic pain (CINP), which is a dose-limiting adverse effect. To date, there is no medicine that prevents CINP in cancer patients and survivors. We determined whether blockers of the canonical Wnt signaling pathway prevent CINP. Neuropathic pain was induced by intraperitoneal injection of paclitaxel (PAC) on four alternate days in male Sprague-Dawley rats or male Axin2-LacZ knock-in mice. XAV-939, LGK-974, and iCRT14, Wnt/β-catenin blockers, were administered intraperitoneally as a single or multiple doses before or after injury. Mechanical allodynia, phosphoproteome profiling, Wnt ligands, and inflammatory mediators were measured by von Frey filament, phosphoproteomics, reverse transcription-polymerase chain reaction, and Western blot analysis. Localization of β-catenin was determined by immunohistochemical analysis in the dorsal root ganglia (DRGs) in rats and human. Our phosphoproteome profiling of CINP rats revealed significant phosphorylation changes in Wnt signaling components. Importantly, repeated systemic injections of XAV-939 or LGK-974 prevented the development of CINP in rats. In addition, XAV-939, LGK-974, and iCRT14 ameliorated CINP. PAC increased Wnt3a and Wnt10a, activated β-catenin in DRG, and increased monocyte chemoattractant protein-1 and interleukin-1β in DRG. PAC also upregulated rAxin2 in mice. Furthermore, β-catenin was expressed in neurons, including calcitonin gene–related protein-expressing neurons and satellite cells in rat and human DRG. In conclusion, chemotherapy increases Wnt3a, Wnt10a, and β-catenin in DRG and their pharmacological blockers prevent and ameliorate CINP, suggesting a target for the prevention and treatment of CINP. © 2020, The American Society for Experimental NeuroTherapeutics, Inc.

A 28.7V Modular Supply Multiplying Pulser With 75.4% Power Reduction Relative to CV2f

ACCEPTIEEE Transactions on Circuits and Systems II: Express Briefs, pp.1 - 1

This paper presents a high voltage modular supply multiplying pulser in a 0.18-μm BCD CMOS process. Two prototypes of the pulser were implemented for target loads of 55pF and 1nF, and generated up to 1MHz and 28.7V pulse from 1.2 and 5V supplies. Proposed modular based stepwise pulse generation achieved a peak power reduction of 75.4% relative to CV2f and a peak power efficiency of 82.3%. The proposed pulser was used for driving piezoelectric micromachined ultrasound transducer (pMUT) and achieved a relative efficiency improvement of 113.7% against conventional two-level square wave pulsing.

Recent Progress in Magnetically Actuated Microrobots for Targeted Delivery of Therapeutic Agents

2020-12Advanced Healthcare Materials, pp.2001596

Therapeutic agents, such as drugs and cells, play an essential role in virtually every treatment of injury, illness, or disease. However, the conventional practices of drug delivery often result in undesirable side effects caused by drug overdose and off-target delivery. In the case of cell delivery, the survival rate of the transplanted cells is extremely low and difficulties with the administration route of cells remain a problem. Recently, magnetically actuated microrobots have started offering unique opportunities in targeted therapeutic delivery due to their tiny size and ability to access hard-to-reach lesions in a minimally invasive manner; considerable advances in this regard have been made over the past decade. Here, recent progress in magnetically actuated microrobots, developed for targeted drug/cell delivery, is presented, with a focus on their design features and mechanisms for controlled therapeutic release. Additionally, the practical challenges faced by the microrobots, and future research directions toward the swift bench-to-bedside translation of the microrobots are addressed. © 2020 Wiley-VCH GmbH

Acoustically Mediated Controlled Drug Release and Targeted Therapy with Degradable 3D Porous Magnetic Microrobots

2021-01Advanced Healthcare Materials, v.10, no.2, pp.2001096

Microrobots for targeted drug delivery are of great interest due to their minimal invasiveness and wireless controllability. Here, a magnetically driven porous degradable microrobot (PDM) is reported that consists of a 3D printed helical soft polymeric chassis made of a poly(ethylene glycol) diacrylate and pentaerythritol triacrylate matrix containing magnetite nanoparticles and the anticancer drug 5-fluorouracil (5-FU). The encapsulated Fe3O4 nanoparticles render the PDM a precise wireless magnetic actuation by means of rotating magnetic fields (RMFs). The increased surface area of the porous PDM facilitates the acoustically induced drug release due to a higher response to the acoustic energy. The drug release profile from the PDM can be selected on command from three different modes, referred to herein as natural, burst, and constant, by differentiating the ultrasound exposure condition. Finally, in vitro test results reveal different therapeutic results for each release mode. The observed great reduction of cancer cell viability in the burst- and constant-release modes confirms that ultrasound with the proposed PDM can enhance the therapeutic effect by increasing drug concentration and sonoporation. © 2020 Wiley-VCH GmbH