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Diglycolamides (DGAs) show excellent application prospects for the extraction and separation of rare earth metals from highly radioactive liquid wastes and rare earth ores. The extraction ability of DGAs for rare earth ions in nitrate or chloride media increases with increasing atomic number of the rare earth metal. To understand the origin of this phenomenon, three binuclear crystals [Ln(TEDGA)3][Ln(NO3)6] of N,N,N′,N′-tetraethyldiglycolamide (TEDGA) with rare earth ions La(III), Pr(III) and Eu(III) were prepared and characterized crystallographically. The three complexes belong to the triclinic crystal system, P-1 space group. The bond lengths of Ln–Oamide are significantly shorter than those of Ln–Oether in the same crystal. The Ln–Oamide and Ln–Oether bond lengths gradually decrease with increasing atomic number of the rare earth ion. The dihedral angle formed by TEDGA and metal ions through the tridentate coordination gradually increases with increasing metal ion atomic number, tending toward the formation of sizeable planar coordination structures for the most massive rare earth ions. The structures of the compounds formed by the extractant and metal ion were optimized by means of DFT simulations. We find that the interaction between TEDGA and the rare earth ion is dominated by electrostatic interaction by analyzing binding energy, WBIs, Mulliken charge, natural electron configurations, and molecular orbital interaction. The covalent component of the Ln–O bonds of the complexes increases with increasing metal atomic number. The observed increase in extraction and separation capacity of diglycolamides for rare earth ions with increasing atomic number might be due to the formation of two five-member rings by one tridentate ligand. The rare earth ions with large atomic numbers tend to form planar structures with large dihedral angles with DGA ligands.

The high cost and relative scarcity of platinum (Pt) restrict large-scale commercialization of fuel cells, which has spurred researchers to develop low-cost alternatives integrating with high hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) catalytic activity. Herein, we performed density functional theory (DFT) calculations to explore the electrocatalytic activity of graphyne nanotubes (GyNTs). Several GyNTs were found to be potential metal-free electrocatalysts, with both HER and ORR activity superior to Pt. Moreover, we revealed a linear relationship between the Gibbs free energy change of O2 adsorption (ΔGOOH) and binding energy of H adsorption (ΔEH), which could be attributed to the fact that both the C O bond of OOH adsorption and the C H bond of H adsorption are single bonds. Therefore, ΔEH is proposed as a general descriptor for the rational design of bifunctional graphyne materials toward HERs and ORRs. Our findings provide a simple strategy for the rational design of bifunctional materials.

Microporous organic polymer nanoparticles bearing tetraphenylethylene moieties (MOPTs) were prepared in the presence of poly(vinylpyrrolidone) (PVP). The PVP was entrapped into the microporous network of MOPT to form MOPT-P and played the roles of size control, porosity enhancement, and surface property management. MOPT materials without PVP showed superhydrophobicity with a water contact angle of 151°. In comparison, the MOPT-P showed excellent water compatibility. Moreover, due to the aggregation-induced emission property of tetraphenylethylene moieties, the MOPT-P showed emission and excellent emission-based sensing of nitrophenols in water with Ksv values in the range of 1.26 × 104 ∼ 3.37 × 104 M–1. It is noteworthy that the MOPT-P used water only as a sensing medium and did not require additional organic solvents to enhance water dispersibility of materials. The MOPT-P could be recovered and reused for the sensing at least five times.

The development of efficient electrocatalysts for the CO2 reduction reaction (CO2 RR) remains a challenge. Demonstrated here is a NiSn atomic-pair electrocatalyst (NiSn-APC) on a hierarchical integrated electrode, which exhibits a synergistic effect in simultaneously promoting the activity and selectivity of the CO2 RR to formate. The NiSn atomic pair consists of adjacent Ni and Sn, each coordinated with four nitrogen atoms (N4 -Ni-Sn-N4 ). The as-prepared NiSn-APC displays exceptional activity for the CO2 RR to formate with a turnover frequency of 4752 h-1 , a formate productivity of 36.7 mol h-1 gSn -1 and an utilization degree of active sites (57.9 %), which are superior to previously reported single-atomic catalysts. Both experimental data and density-functional theory calculations verify the electron redistribution of Sn imposed by adjacent Ni, which reduces the energy barrier of the *OCHO intermediate and makes this potential-determining step thermodynamically spontaneous. This synergistic catalysis provides a successful paradigm for rational design and preparation of atomic-pair electrocatalysts with enhanced performance.

This article aims to introduce the inception and operation of the COVID-19 International Collaborative Research Project, the world’s first coronavirus disease 2019 (COVID-19) open data project for research, along with its dataset and research method, and to discuss relevant considerations for collaborative research using nationwide real-world data (RWD). COVID-19 has spread across the world since early 2020, becoming a serious global health threat to life, safety, and social and economic activities. However, insufficient RWD from patients was available to help clinicians efficiently diagnose and treat patients with COVID-19, or to provide necessary information to the government for policy-making. Countries that saw a rapid surge of infections had to focus on leveraging medical professionals to treat patients, and the circumstances made it even more difficult to promptly use COVID-19 RWD. Against this backdrop, the Health Insurance Review and Assessment Service (HIRA) of Korea decided to open its COVID-19 RWD collected through Korea’s universal health insurance program, under the title of the COVID-19 International Collaborative Research Project. The dataset, consisting of 476 508 claim statements from 234 427 patients (7590 confirmed cases) and 18 691 318 claim statements of the same patients for the previous 3 years, was established and hosted on HIRA’s in-house server. Researchers who applied to participate in the project uploaded analysis code on the platform prepared by HIRA, and HIRA conducted the analysis and provided outcome values. As of November 2020, analyses have been completed for 129 research projects, which have been published or are in the process of being published in prestigious journals.

In 2020, the coronavirus disease 2019 (COVID-19) pandemic has caused unprecedented disruptions to global health systems. The Korea has taken full-fledged actions against this novel infectious disease, swiftly implementing a testing-tracing-treatment strategy. New obligations have therefore been given to the Health Insurance Review and Assessment Service (HIRA) to devote the utmost effort towards tackling this global health crisis. Thanks to the universal national health insurance and state-of-the-art information communications technology (ICT) of the Korea, HIRA has conducted far-reaching countermeasures to detect and treat cases early, prevent the spread of COVID-19, respond quickly to surging demand for the healthcare services, and translate evidence into policy. Three main factors have enabled HIRA to undertake pandemic control preemptively and systematically: nationwide data aggregated from all healthcare providers and patients, pre-existing ICT network systems, and real-time data exchanges. HIRA has maximized the use of data and pre-existing network systems to conduct rapid and responsive measures in a centralized way, both of which have been the most critical tactics and strategies used by the Korean healthcare system. In the face of new obligations, our promise is to strive for a more responsive and resilient health system during this prolonged crisis.

Magnesium in biogenic aragonite skeletons is widely used to infer the geochemical conditions under which the minerals precipitated. However, because molecular speciation of Mg2+ in the aragonite crystal structure remains uncertain, questions are often posed about the reliability and utility of Mg as a paleoenvironment proxy. In this study, we investigated the Mg2+ coordination in abiogenic aragonite by applying first-principles density functional theory (DFT). We report for the first time a Mg2+-site disordered structure model of aragonite: substituted Mg2+ is five-fold coordinated and induces substantial disorder in the bond distances that depends on the relative positions of Mg2+ sites. Using the site disorder model, DFT qualitatively reproduces the key features of experimental Mg K-edge X-ray absorption near-edge structure (XANES) spectra of aragonite. DFT also resolves a long-standing conflict between experimental and theoretical studies pertaining to the enrichment of 26Mg in aragonite relative to calcite. The Boltzmann-averaged 26Mg/24Mg reduced partition function ratios were calculated in the order of aqueous Mg2+ > Mg-doped aragonite > Mg-doped calcite. The disorder structure model is likely applicable to the substitution of cations with radii smaller than the radius of Ca2+ ions in aragonite. Our study provides atomistic insight into metal substitution effects on the metal content and isotope fractionation in biogenic aragonite, which are critical for developing a reliable paleoenvironment proxy.

To study the effect of a stable radical on the photophysical properties of a phosphorescent Pt(II) coordination framework and the intramolecular magnetic interaction between radical ligands in the N^N Pt(II) bisacetylide complexes, we prepared a series of N^N Pt(II) bis(acetylide) complexes with oxoverdazyl radical acetylide ligands. The linker between the Pt(II) center and the spin carrier was systematically varied, to probe the effect on the sign and magnitude of the spin exchange interactions between the radical ligands and photophysical properties. The complexes were studied with steady-state and femtosecond/nanosecond transient absorption spectroscopy, continuous-wave electron paramagnetic resonance (EPR) spectroscopy, and density functional theory (DFT) computations. The transient absorption spectral studies show that the doublet excited state of the radicals are short-lived (τ

Methylmercury is an environmental pollutant that causes neurotoxicity. Recent studies have reported that the ubiquitin-proteasome system is involved in defense against methylmercury toxicity through the degradation of proteins synthesizing the pyruvate. Mitochondrial accumulation of pyruvate can enhance methylmercury toxicity. In addition, methylmercury exposure induces several immune-related chemokines, specifically in the brain, and may cause neurotoxicity. This summary highlights several molecular mechanisms of methylmercury-induced neurotoxicity.

This study introduces a temperature-responsive attractive nanoemulsion (ANE) system, which is characterized by the polymer chain conformation-driven dipolar interaction across different oil droplets in an aqueous medium. To achieve this, highly stable ANEs were produced by co-assembly of amphiphilic triblock copolymers (ATCs), poly(ethylene oxide)-b-poly(e-caprolactone)-b-poly(ethylene oxide) (PEO-b-PCL-b-PEO), with lecithin at the oil-water interface. The dipolar attraction of the methoxy terminated-PEO (mPEO) of ATCs on one drop surface with the lecithin head located on the other drop surface led to the drop-to-drop association. We showed that the efficiency of this interdrop association was dominantly influenced by the chain conformation of mPEO blocks. From dense suspension rheology studies, it was demonstrated that the ANEs formed a gel-like phase below the lower critical solution temperature (LCST) of the mPEO, but transformed to a liquid-like phase above the LCST, which occurred reversibly, thus enabling the development of temperature-responsive emulsion fluids.

Nanodevices based on two-dimensional materials hold great promise for DNA sequencing. Owing to some unique properties, silicene has become a potential alternative to the well-known graphene as a se...

Two-dimensional van der Waals (vdW) heterojunctions have been regarded as promising candidates for photocatalytic water splitting and solar energy conversion. Here, we propose a two-dimensional GeC/GaN vdW heterostructure, where the GaN monolayer and the GeC monolayer are stacked. The binding energy, phonon spectrum, and elastic constants demonstrate this material's high dynamic and mechanical stability. Most notably, the GW band structure, GW + Bethe-Salpeter equation (BSE) optical absorption spectrum, and the band alignment of the density functional theory (DFT) scheme and empirical formula reveal that the GeC/GaN vdW heterostructures have a dramatically high optical absorption coefficient (∼105 cm-1) in the visible region and a suitable band edge with sufficiently large kinetic overpotentials of the hydrogen evolution reaction (ΔEc ≥ 1.945 eV) and the oxygen evolution reaction (ΔEv ≥ 1.244 eV). Photogenerated electrons and holes aggregate on the GeC monolayer and GaN monolayer surfaces, respectively, which could make this heterojunction a promising candidate for photocatalytic water splitting and solar energy conversion.

We report a facile, but robust approach to fabricate structurally stable giant unilamellar vesicles (GUVs), on which a 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) bilayer membrane was made rigid by introducing amphiphilic block polymers. Particularly, we found that lateral co-assembly of an amphiphilic triblock copolymer (ATC) structured with a hydrophobic middle block and long molecular weight (20 K g/mol) hydrophilic end blocks remarkably enhanced the stretching modulus (k) of GUVs. When the membrane composition was optimized, the k value of ATC-hybridized GUVs increased to 6.2 × 108 Pa, which was approximately 10-fold higher than that of DPPC GUVs, thus leading to a much longer half-life. Moreover, we demonstrated that our ATC-hybridized GUVs enabled development of a fascinating vesicular model, which shows great potential as a structurally stable cell membrane mimic.

Selective recovery of silver ions Ag+ has been a big challenge due to its difficult separation from complex aqueous feed streams. Herein, four novel highly selective 13- to 19-membered thia-crown ethers (TCEs) were successfully developed by intermolecular cyclization of S- and O-containing intermediates. The TCEs have reactive hydroxyl group(s) for coating on solid supports. To evaluate their ability to capture Ag+, the TCEs were coated on polypropylene (PP) membrane (TCE@PP) at high loading (∼280 wt%) via wet-incipient technique with glutaraldehyde acetalization. Adsorption results of all TCE@PP reveal high Ag+ capacities with qe ∼124–179 mg g−1, excellent Ag+ selectivities with Kd ∼291–778 L g−1 and rapid uptake rate within 1 h. But DH19-TCE4 or 19TCE@PP is the most effective as it achieved 96% Ag+ complexation compared with others ∼53–86% at feed Co = 1.5 mM. Density functional theory calculations reveal that DH19-TCE4 had the closest cavity size (∅c = 2.35 A) with Ag+ (∅Ag+ = 2.30 A), the most negative binding energy (BE = −65.76 kcal mol−1), and the least cavity distortion during Ag+ complexation. All adsorbents are reusable and stable with consistent performance even after five cycles of adsorption/desorption runs. Overall results demonstrate the effectiveness of the synthesis strategies for TCEs and their high potential as adsorbents, especially DH19-TCE4, for selective Ag+ recovery from aqueous sources.

Porphyromonas gingivalis induces destruction of periodontal tissues that surround and support the teeth, contributing to the development of periodontitis, which eventually results in tooth loss in adults. A 53-kDa protein of P. gingivalis is a major subunit variant protein of minor fimbriae (Mfa1), and is reported to be highly immunogenic and considered as a potential vaccine candidate. The gene encoding 53-kDa protein, was divided into three segments, and each DNA segment was fused to the gene coding for cholera toxin B subunit (CTB) to improve gut mucosal immune responses. The ctb-mfal fusion genes were expressed in the leaf tissues of Nicotiana benthamiana using agroinfiltration. Immunoblot analysis revealed that CTB-Mfa1 fusion proteins were produced in the agroinfiltrated leaves. The interaction of the plant-produced CTB-Mfa1 fusion proteins with GM1-ganglioside, which acts as the binding site for native CTB, was confirmed by GM1-ELISA. Mice immunized orally with the agroinfiltrated leaf powder containing the CTB-Mfa1 fusion proteins elicited serum IgG and fecal IgA antibodies to CTB and Mfa1. These results suggest that CTB-Mfa1 fusion proteins produced in plants can be used as an oral vaccine to control P. gingivalis infection-associated periodontitis.

We report unique observations from drilling and hydraulic stimulation at a depth of approximately 4.3 km in two Enhanced Geothermal System (EGS) wells at the Pohang EGS site, South Korea. We surveyed drilling logs and hydraulic stimulation data, simulated pore pressure diffusion around the fault delineated by seismic and drilling log analyses, conducted acoustic image logging through the EGS wells, observed significant water level drops (740 m) in one of the two EGS wells, and obtained hydrochemical and isotopic variation data in conjunction with the microbial community characteristics of the two EGS wells. We discuss the hydraulic and hydrochemical responses of formation pore water to a few key seismic events near the hypocenter. We focused on how the geochemistry of water that flowed back from the geothermal wells changed in association with key seismic events. These were (1) a swarm of small earthquakes that occurred when a significant circulation mud loss occurred during well drilling, (2) the MW 3.2 earthquake during hydraulic stimulation, and (3) the MW 5.5 main shock two months after the end of hydraulic stimulation. This study highlights the value of real-time monitoring and water chemistry analysis, in addition to seismic monitoring during EGS operation.

Author(s): Salimi, A; Cho, D; Lee, JY; Kang, S; Mukamel, S | Abstract: Third order polarizability, (γ) taken from the collective electronic oscillator (CEO) method was used to calculate the two-photon absorption (TPA) of tetrastyryl-[2,2]paracyclophane derivatives with different through-space charge transfer configurations considering various donor and acceptor combinations at the terminal styryl groups. For the virtually same linear absorption, different TPA spectra were obtained. For controlling and fine-tuning frequency and cross-sections of TPA the through-space charge transfer interactions can be used. The results are explained by the electronic density matrices corresponding to governing oscillators in one- and two-photon absorption and the ground state. It is indicated that for the studied systems mainly the lowest four oscillators are responsible for the TPA cross-sections rather than a simple effective three-state model.

Herein, we report a facile but straightforward way to control the rheological properties of hyaluronic acid (HA) solutions by taking advantage of the interchain association of electrostatically attractive polymeric micelles (APMs). For this, we synthesized an amphiphilic triblock copolymer, poly(2-aminoethyl methacrylate)-block-poly(3-caprolactone)-block-poly(2-aminoethyl methacrylate) (PAMA-b-PCL-b-PAMA), via atomic transfer radical polymerization and co-assembled it with amphiphilic poly(ethylene oxide)-block-poly(e-caprolactone) (PEO-b-PCL) to produce APMs with cationic charges. The incorporation of the APMs into a gel-type HA solution not only readily transitioned the viscous flow to elastic flow but also easily led to the deformation of the gel microstructure in response to the shear rate, which is comparable to the case of a linear HA solution. We identified that the unique rheological behavior of the gel-type HA solutions stemmed from the APM-mediated particulate crosslinking. Finally, we demonstrated that the fine tuning of the interchain association by manipulation of the electrostatic interaction between APMs and HA molecules enabled the diversification of the rheological properties of HA solutions, making this system a promising hydrogel rheology controller.

Oxygen vacancies in TiO2 nanoparticles are important for charge carrier dynamics, with recent studies reporting contradictory results on TiO2 nanoparticle photocatalytic activity. We demonstrate th...

This work provides a comprehensive study on the pore structure and performance of a coated microporous layer (MPL) and a novel sheet MPL for the polymer electrolyte membrane (PEM) fuel cell. We characterize the MPLs using micro-computed tomography, illustrating that the degree and unevenness of MPL intrusion are substantially reduced with the sheet MPL. In-operando X-ray synchrotron imaging reveals a highly surprising observation, whereby the sheet MPL facilitates superior electrochemical performance despite exhibiting higher quantities of liquid water accumulation within the GDL compared to the coated MPL. To further explain this counter-intuitive performance of the sheet MPL, liquid water transport within the GDL is simulated via pore network modeling, and the oxygen diffusion resistance under partially saturated conditions for each GDL is calculated. Under partially saturated conditions, the oxygen transport resistance of the MPL-substrate transition region dominates the overall performance of the PEM fuel cell, and we attribute the superior performance of the sheet MPL to the 10% lower oxygen diffusion resistance in the transition region compared to that of the conventional coated MPL. This work highlights how the interplay between liquid water saturation combined with partially saturated oxygen diffusion resistance must be considered in GDL design for next generation PEM fuel cells.

On September 12, 2018, President Jae-In Moon announced the Comprehensive Plan for Lifelong Care for People with Developmental Disabilities, with representatives from the associated government branches (Ministry of Health and Welfare, Ministry of Education, and Ministry of Employment and Labor) in attendance. The goals of this plan are to provide health, medical, rehabilitative, special education, and social welfare services according to the life-stages of the affected individuals; to reduce parental pressure; to promote social interventions; and to enhance community-level participation in order to create a 'welfare society in harmony.' However, in order for the plan to succeed, additional efforts must be made in the following areas. First, an epidemiological survey is needed to understand the scale, prevalence, and incidence of developmental disabilities and to establish an evidence base to support policy development. Second, accurate definitions of developmental disabilities must be established in order to avoid policy discrimination based on impairment type and age. Third, personal evaluations to assess disabled individuals' unmet needs and customized service designs to deliver those needs are required. Fourth, the plan must fulfill the goals of accessibility and fairness that the government intends to provide. Fifth, the government should consider an integrated financial support system and to propose a detailed plan for monetary distributions. Finally, an integrated system that links health, medical, employment, educational, and welfare services must be constructed.

The membrane hydration state of a polymer electrolyte membrane fuel cell is investigated in operando at high current densities (>1.5 A cm−2) for various inlet gas relative humidities (RH). The ohmic resistance, an indicator for membrane hydration, is found to have a non-monotonic dependence on current densities between 0 and 3.0 A cm−2, and the current density corresponding to the local minimum ohmic resistance is defined as the optimal hydration current density. While the relative thickness of the membrane increases with increasing inlet RH, an interesting observation was made whereby elevating the catalyst-coated membrane (CCM) temperature at current densities above the optimal hydration current density leads to membrane dehydration. Surprisingly, at high inlet gas RH values (70% and 100%) and high current densities, membrane dehydration results in membrane shrinkage (relative to its thickness at 0 A cm−2). We attribute the membrane dehydration and associated shrinkage to the reduced local RH at the CCM, even though the net water flux from the cathode to anode increases. The relative membrane thicknesses as a function of inlet RH conditions are determined from the low frequency arc time constants obtained via electrochemical impedance spectroscopy measurements.

The structures and properties of high capacity conversion electrodes are key factors as these undergo successive lithium insertion and conversion during an electrochemical process in the rechargeable lithium-ion batteries. The invention of alloying, conversion and displacement reactions seem to be crucial for reversible intercalation/de-intercalation of more than one Li during the metal redox oxidation state to achieve the high capacity with the electrode of modern lithium-ion batteries. Therefore, the exploration of new electrode materials is necessary based on the conversion or displacement concept and their potential applications. In addition, most of the electrode materials were selected on the basis of not only capacity, voltage and volume change of bulk, but it is also important to consider point defects, surface and interface properties, nano-size effects and metal-mixtures theoretically to meet their requirements of practical applications. In this review, we overview the development of recent conversion electrodes for their better performance experimentally and theoretically with key issues, challenges and future directions in this rapidly developing field.

The susceptibility of a water molecule to electric fields provides fundamental and essential information for understanding the vibrational spectra of water clusters and condensed-phase water. In th...

A novel reduced graphene oxide/poly(1,5-dihydroxynaphthalene)/TiO2 (RGO/PDHN/TiO2) ternary nanocomposite conducting polymer is electrochemically synthesized on gold electrodes for supercapacitor applications. The RGO/PDHN/TiO2 nanocomposite polymer film is characterized by field-emission scanning electron microscopy (FESEM), Fourier transform infrared spectra (FT-IR), and energy dispersive X-ray spectrometry (EDX) and X-ray diffraction (XRD). The electrochemical performance of the nanocomposite polymer-modified electrode in 1.0 M HClO4 is investigated by various electrochemical methods such as cyclic voltammetry (CV), galvanostatic charge-discharge, and electrochemical impedance spectroscopy (EIS). The RGO/PDHN/TiO2 nanocomposite polymer film in a three-electrode system exhibits a large specific capacitance of 556 F g−1 in comparison with those obtained using RGO/PDHN (432 F g−1) and PDHN (223 F g−1) at a current density of 2.4 A g−1. Simultaneous usage of the electrical double layer capacitance (EDLC) of RGO with the pseudocapacitive behavior of PDHN and TiO2 results in the large specific capacitance in RGO/PDHN/TiO2. The electrochemical self-stabilities of RGO/PDHN/TiO2, RGO/PDHN, and PDHN polymer films are investigated by continuous cycling between −0.20–0.45 V. The RGO/PDHN/TiO2 nanocomposite yields longer self-stability than that of other polymers after 1700 cycles and maintains about 74% of the initial capacitance values.

DFT calculations are performed to investigate the water oxidation reaction intermediates on Ag2M (M = Fe, Co, Ni, Cu), and Pt3 clusters in alkaline media both in the gas and solution (water) phases in the neutral and charged states. The calculated results revealed that the neutral and anionic clusters were found to be more suitable catalysts than cationic clusters because of weakly bonded water oxidation reaction intermediates. In addition, the calculated structural parameters of the water oxidation intermediates with Ag2M (M = Fe, Co, Ni, Cu) clusters revealed that M-OH bond strengths are found to be in the order of Cu

The manganese content of aragonitic bivalve shells is a potential archival indicator of temporal Mn bioavailability in aquatic environments. The Mn speciation mechanism in biogenic aragonite minerals remains elusive because the analog is challenging to synthesize, and the metastable phase has yet to be fully resolved experimentally. In this study, we performed density functional theory (DFT) computations of hypothetical Mn-doped aragonite to examine its local coordination structure and thermodynamic and electronic properties. Our DFT calculations reproduced the experimental crystal structures and solubility product constants (Ksp) of Mn-doped calcite. The magnetic moment of Mn was close to 5 μB in both Mn-doped calcite and Mn-doped aragonite (Ca1−xMnxCO3). The calculated Ksp of Mn-doped aragonite was higher than that of Mn-doped calcite and increased with Mn content, indicative of the unfavorable coprecipitation of Mn with the aragonite phase. We found that the incorporation of a small mole fraction of Mn into aragonite created significant structural distortion around the Mn site, resulting in mixed coordination numbers of Mn (mainly five and seven). Valence-to-core X-ray emission spectroscopy (XES) measurements are useful in determining the coordination environment of Mn complexes. We calculated theoretical XES spectra, with a 1s core hole in Mn, for Mn-doped calcite and four versions of Mn-doped aragonite. The Boltzmann-averaged spectrum for different coordination numbers in Mn-doped aragonite was akin to an experimental XES spectrum of aragonitic bivalve shells. The energy position of the Kβ2,5 band was calculated to be insensitive to Mn speciation in CaCO3; however, the band intensity was relatively sensitive to Mn speciation. The XES spectrum intensity decreased exponentially with increasing Mn–O distance. This quantitative XES relationship we report can reduce uncertainties in the spectral interpretation due to the absence of an Mn-doped aragonite reference spectrum.

In this work, we demonstrate how to synthesize a three-dimensional (3D) ordered PtAu nanoframe superstructure and evaluated its performance as an electrocatalyst. Compared to carbon supported platinum (Pt) nanocrystal electrocatalysts (wherein the aggregation- and carbon corrosion-induced fast degradation is a well-known drawback), the 3D PtAu nanoframe superstructure is free from aggregation and carbon corrosion. The 3D superstructure was self-assembled via drop-casting and evaporation using truncated octahedral PtAu nanoframes (TOh PtAu NFs) as building blocks that were produced by controlled wet-chemical etching of a TOh Au core whose edges and vertexes were selectively deposited with Pt atoms. Density functional theory calculations revealed that the surface alloy state of PtAu gave rise to an enhanced catalytic activity compared to pure Pt. Experimental investigations showed that such 3D superstructure electrocatalysts exhibited excellent mass transfer efficiency, higher catalytic activity and stability towards the methanol oxidation reaction (MOR) compared to a commercial Pt/C catalyst. The demonstrated 3D nanoframe superstructure shows great potential for practical catalytic application due to its high structural stability, high catalytic activity, high surface area and ease of fabrication.

Charge transport and electronic transition properties of a series of newly designed anthracene-based non-doped blue emitters were investigated by density functional theory calculations. For a highly efficient non-doped device, Cz3PhAn-based emitters were designed to suppress the hole and electron reorganization energies required for structural relaxation with respect to the changes of charged states. As a result, the hole hopping rates of triphenylamine (TPA) and phenylbenzimidazole (PBI) substituted Cz3PhAn derivatives (1, 4, and 5–7) were tremendously enhanced as compared to that of Cz3PhAn due to the suppression of the reorganization energy of holes, λh. Moreover, 1 and 4 emitters showed almost identical hopping rates of holes and electrons, which can possibly lead to a perfect charge balance and high efficiency. The photo-physical properties showed that the emission energy of all 1–10 emitters is in 439–473 nm range. It is expected that our rational design strategy can help develop non-doped blue fluorescent emitters for high efficiency.

Nitrogen doped graphdiyne (NGDY) has been reported to have comparable oxygen reduction reaction (ORR) performance to Pt-based catalysts. However, the source of this enhanced ORR performance is not clearly understood. Herein, density functional theory calculations were performed to study the detailed ORR process on NGDY. The theoretically predicted overpotential (η) of GDY materials was 0.442 V, which is comparable to that of Pt-based catalysts, suggesting that GDY is a candidate for non-expensive metal-free ORR catalyst. Our results revealed that the good ORR performance of NGDY originates from the synergy of sp-N and sp2-N, which rules out the experimental proposal that sp-N doping is the dominating factor. Our results further suggest that local positive charge is not a definite descriptor to predict the ORR performance of GDY; instead ΔGO shows a better correlation with performance. Furthermore, it was revealed that the adsorption site is crucial for determining ORR performance, which should not be ignored to fully understand the catalytic activity of GDY-based materials.

Polyphosphate (polyP) is a food additive with antimicrobial activity. Here we evaluated the effects of sodium tripolyphosphate (polyP3, Na5P3O10) on four major oral bacterial species, in both single- and mixed-culture. PolyP3 inhibited three opportunistic pathogenic species: Fusobacterium nucleatum, Prevotella intermedia, and Porphyromonas gingivalis. On the contrary, a commensal bacterium Streptococcus gordonii was relatively less susceptible to polyP3 than the pathogens. When all bacterial species were co-cultured, polyP3 (≥ 0.09%) significantly reduced their total growth and biofilm formation, among which the three pathogenic bacteria were selectively inhibited. Collectively, polyP3 may be an alternative antibacterial agent to control oral pathogenic bacteria. Polyphosphate (polyP) is a food additive with antimicrobial activity. Here we evaluated the effects of sodium tripolyphosphate (polyP3, Na5P3O10) on four major oral bacterial species, in both single- and mixed-culture. PolyP3 inhibited three opportunistic pathogenic species: Fusobacterium nucleatum, Prevotella intermedia, and Porphyromonas gingivalis. On the contrary, a commensal bacterium Streptococcus gordonii was relatively less susceptible to polyP3 than the pathogens. When all bacterial species were co-cultured, polyP3 (≥ 0.09%) significantly reduced their total growth and biofilm formation, among which the three pathogenic bacteria were selectively inhibited. Collectively, polyP3 may be an alternative antibacterial agent to control oral pathogenic bacteria.

Mitochondrial enzyme monoamine oxidase (MAO-A) is known to be overexpressed in prostate cancer (PCa) cells. Herein, we have developed a two-photon probe (PCP-1) for selectively targeting and imaging the MAO-A in PCa. Supported by enzymatic docking and in vitro experiments, PCP-1 showed efficiency to visualize MAO-A overexpressing cells and inhibit their growth and metastasis potential.

We performed DFT calculations to investigate the role of solvent of the non-aqueous electrolytes for the oxygen reduction reaction (ORR) kinetics in Li-air batteries. The calculated results on structural, thermodynamic and vibrational properties revealed that dimethyl sulfoxide (DMSO) is the most stable solvent among DME, DMSO, and MeCN of non-aqueous electrolytes. The LiCF3SO3/DMSO electrolyte was primarily assumed to be the most favorable for ORR kinetics from the IR analysis. We calculated thermodynamic properties of the ORR reactions held during the formation of superoxide (O2−) ion and the sole discharge products lithium peroxide (Li2O2), and lithium oxide (Li2O) to study the ORR kinetics of the stable salt LiCF3SO3 with three solvents namely dimethoxyethane (DME), dimethyl sulfoxide (DMSO), and acetonitrile (MeCN). The thermodynamic properties of the ORR reaction signified the best role of LiCF3SO3/DMSO electrolyte compared to LiCF3SO3/DME and LiCF3SO3/MeCN both in the gas and solution (water) phases.

Monoclinic clinobisvanite BiVO4 is one of the most promising photocatalyst due to its stability, low cost, narrow band gap, and suitable valence band maximum (VBM) position. The valence band maximum of about −7.10 eV at vacuum level was observed, which is well below the redox potential of water. However, the conduction band minimum, CBM of about −4.86 eV at vacuum level, which was responsible for its low efficiency. The presence of metal (Bi or V) vacancy changed the charge density and VBM of pristine BiVO4. Our calculated results revealed that 0.04% of the intrinsic Bi or V defects enhanced p-type conductivity and hence improved photocatalytic activity than O-interstitial in pristine BiVO4. The optical properties of both pristine and intrinsically defective BiVO4 were calculated and analyzed with perspective of their photocatalytic properties. Conclusively, the role of Bi or V (metal) vacancies in pristine BiVO4 was found to be significant than O interstitials in enhancing the photocatalytic properties regarding the solar water splitting.

Cadmium (Cd) is a toxic heavy metal, long-term exposure to which causes renal damage associated with disruption in gene expression. Transcription factors whose activities were altered in the kidneys of mice exposed to Cd for 3 months were assessed using protein/DNA-binding assays. Female C57BL/6J mice were exposed to 300 ppm Cd in the diet for 3 months. Nuclear extracts of kidney were used for protein/DNA-binding assays. The concentration of Cd was approximately 100 ppm in mouse kidney, a level that did not induce renal toxicity. Among the 345 transcription factors evaluated, five transcription factors showed over a two-fold increase in their activities and 14 transcription factors showed a half-fold change in their activities after Cd exposure. These findings may provide new information about the causative transcription factors associated with Cd renal toxicity.

Predicting the crystal structures of novel quaternary compounds can be challenging, as there are only a few stable structures among numerous possible ones. Using a recently developed particle swarm optimization-based crystal structure prediction method and the first-principles calculation method, we discover a new crystal family of quaternary GaNGeC compounds, including six direct band gap semiconductors (denoted as S-1, S-2, S-3, S-4, S-5 and S-6) and two metals (denoted as S-7 and S-8); these compounds can potentially be employed in optoelectronic and energy applications. S-1, S-2, S-3, S-4, S-5 and S-6 exhibit high optical absorption coefficients in the visible region. Moreover, S-1, S-2, S-3, S-4 and S-5 possess band edge positions of the valence band maximum and conduction band minimum that are suitable for photocatalytic overall water splitting in the visible region.

A microfluidic chip integrated with a microelectrode and a cathodic photoelectrochemical (PEC) biosensor for the ultrasensitive detection of non-small cell lung cancer cytokeratin fragments based on a signal amplification strategy was designed. The mechanism for signal amplification is developed based on the p-n junction of AgI/Bi2Ga4O9, with dissolved O2 as an electron acceptor to produce the superoxide anion radical (˙O2-) as the working microelectrode. By combining this with a novel superoxide-dismutase-loaded honeycomb manganese oxide nanostructure (SOD@hMnO2) as the co-catalyst signal amplification label, ˙O2- can be catalyzed by SOD via a disproportionation reaction to produce O2 and H2O2; then, hMnO2 is able to trigger the decomposition of H2O2 to generate O2 and H2O. Therefore, the increased O2 promotes the separation of electron-hole pairs via consuming more electrons, leading to an effective enhancement of the cathodic PEC behavior. Under optimum conditions, with the cytokeratin 19 fragments 21-1 (CYFRA 21-1) as the targeted detection objects, the microfluidic cathodic PEC biosensor chip exhibited excellent linearity from 0.1 pg mL-1 to 100 ng mL-1, with a detection limit of 0.026 pg mL-1 (S/N = 3). The exciting thing that this work offers is a new strategy for the detection of other important cancer biomarkers for disease diagnosis and prognosis.

This study analyzed the hydrochemical characteristics and microbial communities of karst water in Samcheok, Korea, and compared water quality results to identify the seasonal characteristics and hydrogeological connectivity of the study areas of Hamaengbang-ri, Gyogok-ri, Yeosam-ri, and the downtown area of Samcheok. Field survey and water quality analysis were performed in July 2019, February 2020, and April 2020. Hydrochemical analysis of karst water (groundwater and surface water) showed that most samples were comprised of Ca-HCO3 and that water&ndash, rock interactions were a dominant factor compared to precipitation and evaporation (crystallization). For seasonal characteristics, water&ndash, rock interactions appeared more active in the dry season than in the rainy season. Calcite weathering was dominant in the dry season, whereas dolomite weathering dominated the rainy season. Moreover, the saturation indexes for the dry and rainy seasons were less than and greater than 0, respectively, corresponding to an unsaturation (oversaturation) state, thus, white precipitate distributed in the study areas was deposited in the rainy season. Finally, as a result of analyzing the hydraulic characteristics between regions, hydrogeological similarities were identified between Hamaengbang-ri and Yeosam-ri, and between Gyogok-ri and downtown Samcheok, which suggested hydrogeological connectivity between each of the pairs.

Time-resolved circular dichroism signals (TRCD) in the X-ray regime can directly probe the magnitude and the direction of ring currents in molecules. The electronic ring currents in Mg-porphyrin, generated by a coherent superposition of electronic states induced by a circularly polarized UV pulse, are tracked by a time-delayed circularly polarized attosecond X-ray pulse. The signals are calculated using the minimal coupling Hamiltonian, which directly makes use of transition current densities. The TRCD signals obtained from the left and right circularly polarized light pump have opposite signs, revealing the direction of the ring current. Molecular aromaticity and its role in photochemical reactions such as ring opening or closure can be studied using this technique.

Factors controlling the spatial distribution and temporal trend of groundwater quality at a national scale are important to investigate for sustaining livelihood and ecological balance. This study evaluated groundwater quality data for 12 parameters (n = 6405 for each parameter), collected from 97 groundwater monitoring stations (=289 monitoring wells) for ten years. Spatial distribution of groundwater quality parameters varied through the regional scale. Six parameters: T, EC, Ca2+, Mg2+, HCO3&minus, and Cl&minus, were having dominant increasing trend, remaining pH, Eh, Na+, K+, SO42&minus, and NO3&minus, showed a dominant decreasing trend over time. Among land use types, the upland fields had the highest mean of groundwater NO3&minus, (22.2 mg/L), confirming plenty of application of fertilizers (5&ndash, 10 kg/a more than standard) to upland fields. Means of groundwater Cl&minus, and Na+ (705.3 and 298.4 mg/L, respectively) in the residential areas are greater than those in other land use types by 408&ndash, 685.9, 154.3&ndash, 274.2 mg/L, respectively. Agricultural activities were the main controlling factor of groundwater NO3&minus, contamination in rural areas, domestic activities were responsible for groundwater Cl&minus, and Na+ in urban areas, and seawater intrusion was controlling groundwater Cl&minus, in coastal areas (within 10 km from sea). Groundwater hydrochemistry was controlled by the mechanism of geogenic rock and evaporation dominance. The rock dominance mechanism indicated that groundwater was interacting with rocks and resulted in groundwater chemistry. The findings of this study showed that groundwater was mainly contaminated by anthropogenic factors in some rural and residential areas. Effective measures by government authorities are needed to improve the groundwater quality.

Despite being a clinically approved intervention for cancer, photodynamic therapy (PDT) still suffers from limitations. Prime among these is a therapeutic response that is mostly oxygen dependent. This limits the utility of PDT in treating hypoxic tumors since lower levels of cytotoxic reactive oxygen species (ROS) are generated in regions of low oxygen tension. Glutathione-pi (GST-pi) is a key enzyme that militates against ROS-mediated apoptosis. We report herein a new construct, EA-BPS, that contains both a brominated BODIPY photosensitizer (BPS) and an ethacrynic acid (EA) GST-pi inhibitor. Photoirradiation of EA-BPS induces a synergistic antitumor effect that results from the combination of ROS production and GST-pi inhibition. Relative to BPS alone, an enhanced cell-killing effect is seen under hypoxic conditions both in vitro and in vivo. We conclude that by making better use of the available oxygen in tumor environments, improved therapeutic PDT outcomes should be achievable even under hypoxic conditions.

The effects of the unpredictability of the flow system in a karst area, with respect to bacterial communities in the aquatic environment, were evaluated. Bacterial communities from two different types of flow conditions (spring and sinkhole) were characterized and compared in the karst area. Proteobacteria, Bacteroidetes, and Verrucomicrobia were the major phyla present in the sampled spring and sinkhole waters. The water samples from the spring points were heavily loaded with Actinobacteria, especially Firmicutes, which accounted for 4.3% of the bacterial content. Furthermore, Actinobacteria were prevalent in some water samples, serving as indicators of the effects of seawater inundation. The richness and diversity of bacterial species were evaluated at the spring and sinkhole water points. The spring waters showed a higher bacterial richness and diversity compared to the sinkhole waters. Our results provide valuable information for the evaluation and investigation of microbial compositions in karst areas, which are characterized by heterogeneous hydrological conditions. The microbial species in karst areas are already exposed to changing hydrogeological conditions, and are likely to be confronted with future changes, thus, their spatiotemporal variations reflect the shifting baselines of physicochemical and ecosystem processes.

The self-assembly of amyloid-β (Aβ) peptides into senile plaques in the brain is a hallmark of Alzheimer's disease (AD) pathology. Mutation and histidine tautomerism are considered intrinsic origins in the accumulation of Aβ. As a first step toward understanding the impact of A2V mutation and histidine tautomerism on the Aβ42 isoform, we performed replica-exchange molecular dynamics (REMD) simulations to investigate the effects of histidine tautomerism on the structural properties of A2V Aβ42 peptides. There are generally more β-sheet and less α-helix secondary structures in A2V Aβ42 monomers than in WT Aβ42, implying a higher aggregation tendency in A2V Aβ42, which is consistent with previous studies. The current research will help develop the histidine tautomerism hypothesis of misfolded protein aggregation and eventually elucidate the pathogenesis of AD.

To study the hyporheic exchange driven by a single peak flood‐induced water level fluctuation (i.e., flood wave), a method combining numerical simulation with theoretical derivation was proposed based on the Inbuk Stream, Korea, where flooding occurs frequently. The hyporheic exchanges induced by different flood waves were investigated by varying amplitude (A), duration (T), wave type parameter (r), and rising duration (tₚ), which were adopted from the real‐time stream stage fluctuations. Additionally, the idea of constant upstream flood volume (CUFV) condition for flood waves was put forward, and the effects of “Botan” (T/A) and peak number (N) on hyporheic exchange were studied. The results showed that the hyporheic exchange flux (q) was controlled by the water level h (sine‐type) and its change rate v (cosine‐type), and was proportional to the polynomial of them q ∝ (ω∙h + v), where ω is the angular frequency of the flood wave. Based on this mechanism, the influence principles on hyporheic exchanges of the typical flood wave parameters (A, T, r and tₚ) as well as T/A and N under CUFV condition were clarified. The main characteristic variables of hyporheic exchange, which were maximum aquifer storage and residence time, were positively correlated. They also had positive relations to the integral of the flood wave over time, which increased when the wave became higher, wider, rounder and less skewed. However, when CUFV condition was imposed, the residence time was positively correlated with T/A, whereas the maximum aquifer storage was negatively correlated with T/A. With the increase in N, water exchanged more frequently and some water returned to the stream early, leading to the slight decrease in maximum aquifer storage and residence time. These findings enriched the theory of hyporheic exchange driven by surface water fluctuation and be of great significance to enhance pollutant degradation in the hyporheic zone downstream of reservoirs.

By performing first-principles calculations, CO oxidation catalyzed by Fe-embedded defective α-graphyne was systematically investigated. It was found that Fe atoms were strongly anchored at the sp-C vacancy site of α-graphyne with a large binding energy of -5.28 eV and effectively adsorbed and activated O2 molecules. Then, we systematically compared CO oxidation by activated O2via Langmuir-Hinshelwood (LH) and Eley-Rideal (ER) mechanisms. The calculated potential energy surfaces show that the Fe-doped α-graphyne can efficiently oxidize CO via the ER mechanism, in which the threshold of the rate determining step is 0.77 eV. Furthermore, Fe doping shows little effect on the diffusivities of CO, O2, and CO2, which can further enhance its catalytic performance.

The development of active and inexpensive electrocatalysts for the oxygen evolution reaction (OER) to promote water splitting has always been a major challenge. Cobalt-based oxides and sulfides have been actively investigated due to their low cost and high activity. However, the lower intrinsic conductivity of cobalt oxide and the inferior stability of cobalt sulfides still limit their practical application. Herein, CoO was chosen for a proof-of-concept study in which the anion-doping strategy was used to obtain an excellent catalyst. Sulfur incorporation optimizes the charge-transfer properties and active sites of sulfur-doped CoO (S-CoO) and thus gives rise to improved catalytic activity. Besides sulfur doping, the stable framework of the cobalt oxide was well maintained, and thus high stability of S-CoO throughout the reaction process was ensured.

Functional groups in two-dimensional (2D) Ti3 C2 Tx MXene are an important factor influencing electrochemical performance in many applications involving energy storage, electrochemical sensors, and water purification. However, after dimethyl sulfoxide (DMSO) delamination, the effect of surface functionalities in Ti3 C2 Tx is still unclear and there are no systematic reports on its capacitive behavior. Experiments and theoretical calculations confirm the relationship between different surface functionalities, the DMSO delamination effect, and the electrochemical behavior of the DMSO-delaminated Ti3 C2 Tx . The dominant -O and -OH terminations are attributed for surfaces delaminated by using HF [Ti3 C2 Tx (HF)] and LiF/HCl [Ti3 C2 Tx (LiF/HCl)], respectively. Theoretical results are also in agreement with experimental results in that -OH terminations are essential for the formation of a free-standing film. Compared to non-delaminated Ti3 C2 Tx (HF) (similar O/F ratios of 1.37 and 1.42), there is a significant DMSO delamination effect for Ti3 C2 Tx (LiF/HCl) because of different O/F ratios of 2.9 and 3.6. Additionally, the delaminated Ti3 C2 Tx (LiF/HCl) electrodes deliver a higher capacitance of 508 F cm-3 than that of 333 F cm-3 for the delaminated Ti3 C2 Tx (HF), although it exhibited lower equivalent series resistance, lower interlayer spacing, and slightly lower specific surface area. This study provides direct and systematic experimental evidence for different functional groups in Ti3 C2 Tx MXene based on the DMSO delamination effect.

Hyporheic zones are considered hot spots for numerically vast and phylogenetically diverse microbial communities. However, biogeochemical effects of hyporheic zones have rarely been investigated in detail because of the difficulty in accurately measuring denitrification in these zones. To date, little is known about the hydroecology of hyporheic zones. The effect of changes in hydraulic conditions on the community variations of indigenous microorganisms and water quality was examined based on the depth of the hyporheic zone. In particular, we report on the use of the pyrosequencing technique to elucidate denitrifying bacteria (DNB) community profiles combined with the stable isotope composition of nitrate and hydrological patterns in the hyporheic zones to reveal whether denitrification occurs. δ15N-NO3 and δ18O-NO3 values of nitrate were analyzed to evaluate the transformation processes of nitrate in upwelling and downwelling areas and mixed zones. The isotope values indicated different origins of water in upwelling and downwelling zones and that denitrification occurred predominantly in the upwelling areas. Analyses of microbial communities in the hyporheic zone showed that the new genera, species, and isotope data were associated with the hydrological uniqueness of the hyporheic zones. The 16S rRNA sequences were determined and phylogenetic analysis revealed that the DNB communities distributed and gathered the genus Comamonas denitrificans within the mixing patterns of the hyporheic zones and that the relative scarcity of these microbes in these zones was caused by the lack of appropriate substrates. The delineation of the surface water-groundwater mixing zone was quantitatively determined by systematically combining the hydrological and heat transfer analyses and by comparing denitrifying bacteria communities and N isotope data. This study showed that pyrosequencing and isotopic approaches are useful for evaluating the transformation processes of nitrate at the upwelling and downwelling points of a hyporheic zone.