Joohee Lee

N-doped monolayer graphene catalyst on silicon photocathode for hydrogen production

Carbon-based catalysts have been attracting attention in renewable energy technologies due to the low cost and high stability, but their insufficient activity is still a challenging issue. Here, we suggest that monolayer graphene can be used as a catalyst for solar-driven hydrogen evolution reaction on Si-photocathodes, and its catalytic activity is boosted by plasma treatment in N2-ambient. The plasma treatment induces abundant defects and the incorporation of nitrogen atoms in the graphene structure, which can act as catalytic sites on graphene. The monolayer graphene containing nitrogen impurities exhibits a remarkable increase in the exchange current density and leads to a significant anodic shift of the onset of photocurrent from the Si-photocathode. Additionally, monolayer graphene shows the passivation effect that suppresses the surface oxidation of Si, thus enabling the operation of the Si-photocathode in neutral water. This study shows that graphene itself can be applied to a photoelectrochemical system as a catalyst with high activity and chemical stability.

Organolead Halide Perovskites for Low Operating Voltage Multilevel Resistive Switching

Organolead halide perovskites are used for low-operating-voltage multilevel resistive switching. Ag/CH3 NH3 PbI3 /Pt cells exhibit electroforming-free resistive switching at an electric field of 3.25 × 10(3) V cm(-1) for four distinguishable ON-state resistance levels. The migration of iodine interstitials and vacancies with low activation energies is responsible for the low-electric-field resistive switching via filament formation and annihilation.

Heme oxygenase-1-mediated anti-inflammatory effects of tussilagonone on macrophages and 12-O-tetradecanoylphorbol-13-acetate-induced skin inflammation in mice

The dried flower buds of Tussilago farfara L. have been used in traditional medicine, mainly as an antitussive in the treatment of cough and other respiratory problems. In the present study, we investigated the anti-inflammatory signaling pathway via the upregulation of heme oxygenase-1 (HO-1) in response to tussilagonone (TGN), a sesquiterpene compound isolated from T. farfara. TGN induced HO-1 expression and nuclear factor-E2-related factor 2 (Nrf2) activation in RAW 264.7 cells. Nuclear translocation of Nrf2 by TGN also increased in a time- and dose-dependent manner, indicating that TGN induced HO-1 via the Nrf2 pathway. Consistent with the notion that HO-1 has anti-inflammatory properties, TGN suppressed inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression and reduced the mRNA expression of proinflammatory cytokines, as well as nitric oxide (NO) and prostaglandin E2 (PGE2) production in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. TGN inhibited the phosphorylation and degradation of inhibitory κB-α (IκB-α) and the nuclear translocation of nuclear factor (NF)-κB. However, a specific inhibitor of HO-1 reversed the TGN-mediated suppression of NO production and knockdown of HO-1 by small interfering RNA abrogated inhibitory effects of TGN on iNOS and COX-2 protein expression and NF-κB nuclear translocation. Furthermore, TGN reduced iNOS and COX-2 expression in a 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced skin inflammation mouse model. Taken together, these findings suggest an important role for TGN-induced HO-1 activation in regulating inflammatory responses. Moreover, TGN is a potent therapeutic candidate for targeting the crosstalk between Nrf2/HO-1 and the NF-κB signaling pathway in the prevention or treatment of inflammation-associated diseases.

Lizard: Cut Off the Tail! A Practical Post-quantum Public-Key Encryption from LWE and LWR

The LWE problem has been widely used in many constructions for post-quantum cryptography due to its reduction from the worst-case of lattice hard problems and the lightweight operations for generating its instances. The PKE schemes based on the LWE problem have a simple and fast decryption, but the encryption phase requires large parameter size for the leftover hash lemma or Gaussian samplings.

Neurogenic differentiation of human dental stem cells in vitro.

Objectives The purpose of this study was to investigate the neurogenic differentiation of human dental pulp stem cells (DPSCs), periodontal ligament stem cells (PDLSCs), and stem cells from apical papilla (SCAP). Materials and Methods After induction of neurogenic differentiation using commercial differentiation medium, expression levels of neural markers, microtubule-associated protein 2 (MAP2), class III β-tubulin, and glial fibrillary acidic protein (GFAP) were identified using reverse transcriptase polymerase chain reaction (PCR), real-time PCR, and immunocytochemistry. Results The induced cells showed neuron-like morphologies, similar to axons, dendrites, and perikaryons, which are composed of neurons in DPSCs, PDLSCs, and SCAP. The mRNA levels of neuronal markers tended to increase in differentiated cells. The expression of MAP2 and β-tubulin III also increased at the protein level in differentiation groups, even though GFAP was not detected via immunocytochemistry. Conclusion Human dental stem cells including DPSCs, PDLSCs, and SCAP may have neurogenic differentiation capability in vitro. The presented data support the use of human dental stem cells as a possible alternative source of stem cells for therapeutic utility in the treatment of neurological diseases.

Property database for single-element doping in ZnO obtained by automated first-principles calculations.

Throughout the past decades, doped-ZnO has been widely used in various optical, electrical, magnetic, and energy devices. While almost every element in the Periodic Table was doped in ZnO, the systematic computational study is still limited to a small number of dopants, which may hinder a firm understanding of experimental observations. In this report, we systematically calculate the single-element doping property of ZnO using first-principles calculations. We develop an automation code that enables efficient and reliable high-throughput calculations on thousands of possible dopant configurations. As a result, we obtain formation-energy diagrams for total 61 dopants, ranging from Li to Bi. Furthermore, we evaluate each dopant in terms of n-type/p-type behaviors by identifying the major dopant configurations and calculating carrier concentrations at a specific dopant density. The existence of localized magnetic moment is also examined for spintronic applications. The property database obtained here for doped ZnO will serve as a useful reference in engineering the material property of ZnO through doping.

Drastically enhanced hydrogen evolution activity by 2D to 3D structural transition in anion-engineered molybdenum disulfide thin films for efficient Si-based water splitting photocathodes

We synthesized transferrable and transparent anion-engineered molybdenum disulfide thin-film catalysts through a simple thermolysis method by using [(NH4)2MoS4] solution and powder precursors with different sulphur/phosphorus weight ratios. The synthesized sulphur-doped molybdenum phosphide (S:MoP) thin film changed from a two-dimensional van der Waals structure to a three-dimensional hexagonal structure by introduction of phosphorus atoms in the MoS2 thin film. The S:MoP thin film catalyst, which is composed of cheap and earth abundant elements, could provide the lowest onset potential and the highest photocurrent density for planar p-type Si photocathodes. The density functional theory calculations indicate that the surface of S:MoP thin films absorb hydrogen better than that of MoS2 thin films. The structurally engineered thin film catalyst facilitates the easy transfer of photogenerated electrons from the p-Si light absorber to the electrolyte. Anion-engineering of the MoS2 thin film catalyst would be an efficient way to enhance the catalytic activity for photoelectrochemical water splitting.

Privacy-Preserving Computations of Predictive Medical Models with Minimax Approximation and Non-Adjacent Form

In 2014, Bos et al. introduced a cloud service scenario to provide private predictive analyses on encrypted medical data, and gave a proof of concept implementation by utilizing homomorphic encryption (HE) scheme. In their implementation, they needed to approximate an analytic predictive model to a polynomial, using Taylor approximations. However, their approach could not reach a satisfactory compromise so that they just restricted the pool of data to guarantee suitable accuracy. In this paper, we suggest and implement a new efficient approach to provide the service using minimax approximation and Non-Adjacent Form (NAF) encoding. With our method, it is possible to remove the limitation of input range and reduce maximum errors, allowing faster analyses than the previous work. Moreover, we prove that the NAF encoding allows us to use more efficient parameters than the binary encoding used in the previous work or balaced base-B encoding. For comparison with the previous work, we present implementation results using HElib. Our implementation gives a prediction with 7-bit precision (of maximal error 0.0044) for having a heart attack, and makes the prediction in 0.5 s on a single laptop. We also implement the private healthcare service analyzing a Cox Proportional Hazard Model for the first time.

Attenuation of neuropathic pain and neuroinflammatory responses by a pyranocoumarin derivative, anomalin in animal and cellular models

The present study investigated the neuropathic pain, anti-neuroinflammatory and neuroprotective properties of a pyranocoumarin derivative (anomalin) in in vivo and in vitro models. An in vivo streptozotocin (STZ)-induced diabetic neuropathic pain model demonstrated that anomalin significantly suppressed neuropathic pain in mice. To identify the molecular mechanism of the anti-neuropathic pain activity of anomalin, sodium-nitroprusside (SNP)-induced neuroinflammation in neuro-2a (N2a) cells was further investigated in signaling pathways. The effects of anomalin against SNP-induced toxicity, nitrite production and related mRNA gene expression (iNOS and COX-2) were considerably reduced by anomalin in the SNP-induced N2a cells. In the molecular signaling pathway, anomalin effectively blocked the SNP-induced activation of the IKKα/β, IκBα, ERK1/2 and p38 MAPK pathways. Furthermore, anomalin remarkably reduced the increase in the SNP-induced nuclear factor (erythroid-derived 2)-like 2 (Nrf2) pathway. Additionally, the pro-inflammatory cytokines level was remarkably inhibited by anomalin in high glucose-induced DRG primary neurons and SNP-induced N2a cells. These findings indicate that anomalin has anti-neuropathic pain, anti-neuroinflammatory and neuroprotective effects against STZ-induced diabetic type I neuropathic pain and SNP-induced in neuronal cell models via the inactivation of the NF-κB, Nrf2 and MAPK signaling pathways.

Upregulation of GM-CSF by TGF-β1 in epithelial mesenchymal transition of human HERS/ERM cells.

Hertwig’s epithelial root sheath/epithelial rests of Malassez (HERS/ERM) have been suggested to play an important role in tooth root formation, particularly in periodontal development. Epithelial mesenchymal transition (EMT) has been suggested to contribute to root development in tooth. However, the mechanism of interaction between HERS/ERM cells and dental mesenchymal cells has not been fully understood. In this study, we investigated the effect of exogenous transforming growth factor beta 1 (TGF-β1) in human HERS/ERM cells in order to verify the role of granulocyte macrophage colony-stimulating factor (GM-CSF) in EMT process. Antibody array was used to screen secretion factors by exogenous TGF-β1. Secretion of GM-CSF was increased by exogenous TGF-β1. Expression levels of EMT markers, vimentin, ZEB1 (zinc finger E-box binding homeobox 1), and E-cadherin, were confirmed using reverse transcription polymerase chain reaction and immunocytochemistry. Treatment with GM-CSF increased the expression of vimentin and ZEB1, similar to TGF-β1 treatment, and decreased the expression of E-cadherin. Our results suggest that GM-CSF could induce EMT in human HERS/ERM cells.