Daegu Gyeongbuk Institute of Science and Technology

autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.

We have synthesized, characterized, and computationally simulated/validated the behavior of two new metal-organic framework (MOF) materials displaying the highest experimental Brunauer-Emmett-Teller (BET) surface areas of any porous materials reported to date (~7000 m(2)/g). Key to evacuating the initially solvent-filled materials without pore collapse, and thereby accessing the ultrahigh areas, is the use of a supercritical CO(2) activation technique. Additionally, we demonstrate computationally that by shifting from phenyl groups to "space efficient" acetylene moieties as linker expansion units, the hypothetical maximum surface area for a MOF material is substantially greater than previously envisioned (~14600 m(2)/g (or greater) versus ~10500 m(2)/g).

A recent approach for solar‐to‐hydrogen generation has been water electrolysis using efficient, stable, and inexpensive bifunctional electrocatalysts within strong electrolytes. Herein, the direct growth of 1D NiCo 2 S 4 nanowire (NW) arrays on a 3D Ni foam (NF) is described. This NiCo 2 S 4 NW/NF array functions as an efficient bifunctional electrocatalyst for overall water splitting with excellent activity and stability. The 3D‐Ni foam facilitates the directional growth, exposing more active sites of the catalyst for electrochemical reactions at the electrode–electrolyte interface. The binder‐free, self‐made NiCo 2 S 4 NW/NF electrode delivers a hydrogen production current density of 10 mA cm –2 at an overpotential of 260 mV for the oxygen evolution reaction and at 210 mV (versus a reversible hydrogen electrode) for the hydrogen evolution reaction in 1 m KOH. This highly active and stable bifunctional electrocatalyst enables the preparation of an alkaline water electrolyzer that could deliver 10 mA cm –2 under a cell voltage of 1.63 V. Because the nonprecious‐metal NiCo 2 S 4 NW/NF foam‐based electrodes afford the vigorous and continuous evolution of both H 2 and O 2 at 1.68 V, generated using a solar panel, they appear to be promising water splitting devices for large‐scale solar‐to‐hydrogen generation.

Herein, we describe simple, fast and reproducible halide ion exchange reactions in CsPbX3 (X = Cl, Br, I) nanocrystals (NCs) at room temperature. Through the simple adjustment of the halide ion concentration, the photoluminescence of these NCs can be tuned over the entire visible region (425-655 nm). Photodetector devices based on entirely inorganic CsPbI3 NCs are demonstrated for the first time. The photodetectors exhibited a good on/off photocurrent ratio of 10(5).

The deficiency of segmentation labels is one of the main obstacles to semantic segmentation in the wild. To alleviate this issue, we present a novel framework that generates segmentation labels of images given their image-level class labels. In this weakly supervised setting, trained models have been known to segment local discriminative parts rather than the entire object area. Our solution is to propagate such local responses to nearby areas which belong to the same semantic entity. To this end, we propose a Deep Neural Network (DNN) called AffinityNet that predicts semantic affinity between a pair of adjacent image coordinates. The semantic propagation is then realized by random walk with the affinities predicted by AffinityNet. More importantly, the supervision employed to train AffinityNet is given by the initial discriminative part segmentation, which is incomplete as a segmentation annotation but sufficient for learning semantic affinities within small image areas. Thus the entire framework relies only on image-level class labels and does not require any extra data or annotations. On the PASCAL VOC 2012 dataset, a DNN learned with segmentation labels generated by our method outperforms previous models trained with the same level of supervision, and is even as competitive as those relying on stronger supervision.

Existing vital sign monitoring systems in the neonatal intensive care unit (NICU) require multiple wires connected to rigid sensors with strongly adherent interfaces to the skin. We introduce a pair of ultrathin, soft, skin-like electronic devices whose coordinated, wireless operation reproduces the functionality of these traditional technologies but bypasses their intrinsic limitations. The enabling advances in engineering science include designs that support wireless, battery-free operation; real-time, in-sensor data analytics; time-synchronized, continuous data streaming; soft mechanics and gentle adhesive interfaces to the skin; and compatibility with visual inspection and with medical imaging techniques used in the NICU. Preliminary studies on neonates admitted to operating NICUs demonstrate performance comparable to the most advanced clinical-standard monitoring systems.

Photocatalytic CO 2 conversion is vital technology to realize global carbon neutrality and generate future energy supplies. This review proposes fundamentals, challenges, strategies, and prospects for photocatalytic CO 2 conversion research.

Significance Water is considered to be a stable and relatively inert molecule in bulk solution. We report an exceptional behavior of water: Water molecules are spontaneously oxidized to form hydrogen peroxide near the water−air interface of micron-sized water droplets. This process does not require any chemical reagent, catalyst, applied electric potential, or radiation. Only pure water in the form of microdroplets in air is necessary for the appearance of hydrogen peroxide. We suggest that this discovery opens various innovative opportunities including green and inexpensive production of hydrogen peroxide, green chemical synthesis, safe cleaning, and food processing.

We propose the use of deep convolutional neural networks (DCNNs) for human detection and activity classification based on Doppler radar. Previously, proposed schemes for these problems remained in the conventional supervised learning paradigm that relies on the design of handcrafted features. Whereas these schemes attained high accuracy, the requirement for domain knowledge of each problem limits the scalability of the proposed schemes. In this letter, we present an alternative deep learning approach. We apply the DCNN, one of the most successful deep learning algorithms, directly to a raw micro-Doppler spectrogram for both human detection and activity classification problem. The DCNN can jointly learn the necessary features and classification boundaries using the measured data without employing any explicit features on the micro-Doppler signals. We show that the DCNN can achieve accuracy results of 97.6% for human detection and 90.9% for human activity classification.

This paper presents a novel approach for learning instance segmentation with image-level class labels as supervision. Our approach generates pseudo instance segmentation labels of training images, which are used to train a fully supervised model. For generating the pseudo labels, we first identify confident seed areas of object classes from attention maps of an image classification model, and propagate them to discover the entire instance areas with accurate boundaries. To this end, we propose IRNet, which estimates rough areas of individual instances and detects boundaries between different object classes. It thus enables to assign instance labels to the seeds and to propagate them within the boundaries so that the entire areas of instances can be estimated accurately. Furthermore, IRNet is trained with inter-pixel relations on the attention maps, thus no extra supervision is required. Our method with IRNet achieves an outstanding performance on the PASCAL VOC 2012 dataset, surpassing not only previous state-of-the-art trained with the same level of supervision, but also some of previous models relying on stronger supervision.

Electrochemical oxygen evolution and reduction reactions have received great attention due to their importance in several key technologies such as fuel cells, electrolyzers, and metal–air batteries. Here, we present a simple approach to the preparation of cobalt sulfide nanoparticles in situ grown on a nitrogen and sulfur codoped graphene oxide surface. The particle size and phase were controlled by changing the treatment temperature. Cobalt sulfide nanoparticles dispersed on graphene oxide hybrids were successfully prepared by a solid-state thermolysis approach at different temperatures (400, 500, and 600 °C) using cobalt thiourea and graphene oxide. X-ray diffraction studies revealed that hybrids prepared at 400 and 500 °C result in pure CoS2 phase, whereas the hybrid prepared at 600 °C exhibits Co9S8 phase. X-ray photoelectron spectroscopy studies revealed that nitrogen and sulfur simultaneously codoped on the graphene oxide surface, and these sites act to anchor the CoS2 nanoparticles strongly on the GO surface. The strong coupling between CoS2 and N,S-GO was reflected in the improvement of the oxygen electrode potential. CoS2(400)/N,S-GO showed an outstanding oxygen electrode activity with a potential of about 0.82 V against a reversible hydrogen electrode in alkaline medium, which is far better than the performance of precious catalysts such as Pt/C (1.16 V), Ru/C (1.01 V), and Ir/C (0.92 V).

Given that energy (exciton) migration in natural photosynthesis primarily occurs in highly ordered porphyrin-like pigments (chlorophylls), equally highly ordered porphyrin-based metal-organic frameworks (MOFs) might be expected to exhibit similar behavior, thereby facilitating antenna-like light-harvesting and positioning such materials for use in solar energy conversion schemes. Herein, we report the first example of directional, long-distance energy migration within a MOF. Two MOFs, namely F-MOF and DA-MOF that are composed of two Zn(II) porphyrin struts [5,15-dipyridyl-10,20-bis(pentafluorophenyl)porphinato]zinc(II) and [5,15-bis[4-(pyridyl)ethynyl]-10,20-diphenylporphinato]zinc(II), respectively, were investigated. From fluorescence quenching experiments and theoretical calculations, we find that the photogenerated exciton migrates over a net distance of up to ~45 porphyrin struts within its lifetime in DA-MOF (but only ~3 in F-MOF), with a high anisotropy along a specific direction. The remarkably efficient exciton migration in DA-MOF is attributed to enhanced π-conjugation through the addition of two acetylene moieties in the porphyrin molecule, which leads to greater Q-band absorption intensity and much faster exciton-hopping (energy transfer between adjacent porphyrin struts). The long distance and directional energy migration in DA-MOF suggests promising applications of this compound or related compounds in solar energy conversion schemes as an efficient light-harvesting and energy-transport component.

Since Klaus Schwab and the World Economic Forum declared the arrival of the Fourth Industrial Revolution, there has been much discussion about it. However, there is no commonly agreed-upon definition of the Fourth Industrial Revolution. Therefore, we attempted to answer the following four research questions. “What is the definition of the Fourth Industrial Revolution?”, “How can we respond to the Fourth Industrial Revolution in terms of institutions?”, “How can we respond to the Fourth Industrial Revolution in terms of technology?”, “How can we respond to the Fourth Industrial Revolution in terms of firm innovation and start-up strategy?” Brainstorming was conducted by 11 scholars from several countries to answer these four research questions. Therefore, this research is not the end product of four research questions, but a kind of advanced template to answer the four research questions for continuing research.

Serious climate changes and energy-related environmental problems are currently critical issues in the world. In order to reduce carbon emissions and save our environment, renewable energy harvesting technologies will serve as a key solution in the near future. Among them, triboelectric nanogenerators (TENGs), which is one of the most promising mechanical energy harvesters by means of contact electrification phenomenon, are explosively developing due to abundant wasting mechanical energy sources and a number of superior advantages in a wide availability and selection of materials, relatively simple device configurations, and low-cost processing. Significant experimental and theoretical efforts have been achieved toward understanding fundamental behaviors and a wide range of demonstrations since its report in 2012. As a result, considerable technological advancement has been exhibited and it advances the timeline of achievement in the proposed roadmap. Now, the technology has reached the stage of prototype development with verification of performance beyond the lab scale environment toward its commercialization. In this review, distinguished authors in the world worked together to summarize the state of the art in theory, materials, devices, systems, circuits, and applications in TENG fields. The great research achievements of researchers in this field around the world over the past decade are expected to play a major role in coming to fruition of unexpectedly accelerated technological advances over the next decade.

Leaf senescence is an important developmental process involving orderly disassembly of macromolecules for relocating nutrients from leaves to other organs and is critical for plants' fitness. Leaf senescence is the response of an intricate integration of various environmental signals and leaf age information and involves a complex and highly regulated process with the coordinated actions of multiple pathways. Impressive progress has been made in understanding how senescence signals are perceived and processed, how the orderly degeneration process is regulated, how the senescence program interacts with environmental signals, and how senescence regulatory genes contribute to plant productivity and fitness. Employment of systems approaches using omics-based technologies and characterization of key regulators have been fruitful in providing newly emerging regulatory mechanisms. This review mainly discusses recent advances in systems understanding of leaf senescence from a molecular network dynamics perspective. Genetic strategies for improving the productivity and quality of crops are also described.

Low modulus, compliant systems of sensors, circuits and radios designed to intimately interface with the soft tissues of the human body are of growing interest, due to their emerging applications in continuous, clinical-quality health monitors and advanced, bioelectronic therapeutics. Although recent research establishes various materials and mechanics concepts for such technologies, all existing approaches involve simple, two-dimensional (2D) layouts in the constituent micro-components and interconnects. Here we introduce concepts in three-dimensional (3D) architectures that bypass important engineering constraints and performance limitations set by traditional, 2D designs. Specifically, open-mesh, 3D interconnect networks of helical microcoils formed by deterministic compressive buckling establish the basis for systems that can offer exceptional low modulus, elastic mechanics, in compact geometries, with active components and sophisticated levels of functionality. Coupled mechanical and electrical design approaches enable layout optimization, assembly processes and encapsulation schemes to yield 3D configurations that satisfy requirements in demanding, complex systems, such as wireless, skin-compatible electronic sensors.

Various methods have been developed in surface chemistry to control interface properties of a solid material. A selection rule among surface chemistries is compatibility between a surface functionalization tool and a target material. For example, alkanethiol deposition on noble metal surfaces, widely known as the formation of a self-assembled monolayer (SAM), cannot be performed on oxide material surfaces. One must choose organosilane molecules to functionalize oxide surfaces. Thus, the surface chemistry strictly depends on the properties of the surface. Polydopamine coating is now generally accepted as the first toolbox for functionalization of virtually any material surface. Layer-by-layer (LbL) assembly is a widely used method to modify properties of versatile surfaces, including organic materials, metal oxides, and noble metals, along with polydopamine coating. On flat solid substrates, the two chemistries of polydopamine coating and LbL assembly provide similar levels of surface modifications. However, there are additional distinct features in polydopamine. First, polydopamine coating is effective for two- or three-dimensional porous materials such as metal-organic frameworks (MOFs), synthetic polyolefin membranes, and others because small-sized dopamine (MW = 153.18 u) and its oxidized oligomers are readily attached onto narrow-spaced surfaces without exhibiting steric hindrance. In contrast, polymers used in LbL assembly are slow in diffusion because of steric hindrance due to their high molecular weight. Second, it is applicable to structurally nonflat surfaces showing special wettability such as superhydrophobicity or superoleophobicity. Third, a nonconducting, insulating polydopamine layer can be converted to be a conducting layer by pyrolysis. The product after pyrolysis is a N-doped graphene-like material that is useful for graphene or carbon nanotube-containing composites. Fourth, it is a suitable method for engineering the surface properties of various composite materials. The surface properties of participating components in composite materials can be unified by polydopamine coating with a simple one-step process. Fifth, a polydopamine layer exhibits intrinsic chemical reactivity by the presence of catecholquinone moieties and catechol radical species on surfaces. Nucleophiles such as amine and thiolate spontaneously react with the functionalized layer. Applications of polydopamine coating are exponentially growing and include cell culture/patterning, microfluidics, antimicrobial surfaces, tissue engineering, drug delivery systems, photothermal therapy, immobilization of photocatalysts, Li-ion battery membranes, Li-sulfur battery cathode materials, oil/water separation, water detoxification, organocatalysts, membrane separation technologies, carbonization, and others. In this Account, we describe various polydopamine coating methods and then introduce a number of chemical derivatives of dopamine that will open further development of material-independent surface chemistry.

A nickel-doped cobalt oxide spinel structure is a promising non-precious metal electrocatalyst for oxygen evolution and oxygen reduction in rechargeable metal-air batteries and water electrolyzers operating with alkaline electrolytes. One dimensional NiCo2O4 (NCO) nanostructures were prepared by using a simple electrospinning technique with two different metal precursors (metal nitrate/PAN and metal acetylacetonate/PAN). The effect of precursor concentration on the morphologies was investigated. Single-phase, NCO with an average diameter of 100 nm, porous interconnected fibrous morphology was revealed by FESEM and FETEM analysis. The hierarchical nanostructured 1D-spinel NiCo2O4 materials showed a remarkable electrocatalytic activity towards oxygen reduction and evolution in an aqueous alkaline medium. The extraordinary bi-functional catalytic activity towards both ORR and OER was observed by the low over potential (0.84 V), which is better than that of noble metal catalysts [Pt/C (1.16 V), Ru/C (1.01 V) and Ir/C (0.92 V)], making them promising cathode materials for metal-air batteries. Furthermore, the rechargeable zinc-air battery with NCO-A1 as a bifunctional electrocatalyst displays high activity and stability during battery discharge, charge, and cycling processes.

Magnetically manipulated microrobots are demonstrated for targeted cell transportation. Full three-dimensional (3D) porous structures are fabricated with an SU-8 photoresist using a 3D laser lithography system. Nickel and titanium are deposited as a magnetic material and biocompatible material, respectively. The fabricated microrobots are controlled in the fluid by external magnetic fields. Human embryonic kidney 239 (HEK 239) cells are cultivated in the microrobot to show the possibility for targeted cell transportation.

Platinum-ion-doped TiO2 (Pt(ion)-TiO2) was synthesized by a sol-gel method, and its visible light photocatalytic activities were successfully demonstrated for the oxidative and reductive degradation of chlorinated organic compounds. Pt(ion)-TiO2 exhibited a yellow-brown color, and its band gap was lower than that of undoped TiO2 by about 0.2 eV. The flat band potential of Pt(ion)-TiO2 was positively shifted by 50 mV compared with that of undoped TiO2. X-ray absorption spectroscopy and X-ray photoelectron spectroscopy analyses showed that the Pt ions substituted in the TiO2 lattice were present mainly in the Pt(IV) state with some Pt(II) on the sample surface. Pt(ion)-TiO2 exhibited higher photocatalytic activities than undoped TiO2 under UV irradiation as well. The visible light activity of Pt(ion)-TiO2 was strongly affected by the calcination temperature and the concentration of Pt ion dopant, which were optimal at 673 K and 0.5 atom %, respectively. Under visible irradiation, Pt(ion)-TiO2 degraded dichloroacetate and 4-chlorophenol through an oxidative path and trichloroacetate via a reductive path. The activity of Pt(ion)-TiO2 was not reduced when used repeatedly under visible light. However, visible-light-illuminated Pt(ion)-TiO2 could not degrade substrates such as tetramethylammonium and trichloroethylene, which are degraded with UV-illuminated TiO2. The characteristics and reactivities of Pt(ion)-TiO2 as a new visible light photocatalyst were investigated in various ways and discussed in detail.