Oxyanion-Sensitive Catalytic Activity of Ni(II)/Oxyanion Systems for Heterogeneous Organic Degradation: Differential Oxidizing Capacity of Ni(III) and Ni(IV) as High-Valent Intermediates.

This study demonstrated that NiO and Ni(OH)2 as Ni(II) catalysts exhibited significant activity for organic oxidation in the presence of various oxyanions, such as hypochlorous acid (HOCl), peroxymonosulfate (PMS), and peroxydisulfate (PDS), which markedly contrasted with Co-based counterparts exclusively activating PMS to yield sulfate radicals. The oxidizing capacity of the Ni catalyst/oxyanion varied depending on the oxyanion type. Ni catalyst/PMS (or HOCl) degraded a broad spectrum of organics, whereas PDS enabled selective phenol oxidation. This stemmed from the differential reactivity of two high-valent Ni intermediates, Ni(III) and Ni(IV). A high similarity with Ni(III)OOH in a substrate-specific reactivity indicated the role of Ni(III) as the primary oxidant of Ni-activated PDS. With the minor progress of redox reactions with radical probes and multiple spectroscopic evidence on moderate Ni(III) accumulation, the significant elimination of non-phenolic contaminants by NiOOH/PMS (or HOCl) suggested the involvement of Ni(IV) in the substrate-insensitive treatment capability of Ni catalyst/PMS (or HOCl). Since the electron-transfer oxidation of organics by high-valent Ni species involved Ni(II) regeneration, the loss of the treatment efficiency of Ni/oxyanion was marginal over multiple catalytic cycles.

Stadium-type resonator sensor based on a multi-mode waveguide with mode discrimination phenomenon.

In this work, we present a multi-mode resonator based on SU-8 polymer and experimentally verify that the resonator showed mode discrimination can be used as a sensor with high performance. According to field emission scanning electron microscopy (FE-SEM) images, the fabricated resonator shows sidewall roughness which is canonically considered to be undesirable after a typical development process. In order to analyze the effect of sidewall roughness, we conduct the resonator simulation considering the roughness under various conditions. Mode discrimination still occurs even in the presence of sidewall roughness. In addition, waveguide width controllable by UV exposure time effectively contributes to mode discrimination. To verify the resonator as a sensor, we perform a temperature variation experiment, which results in a high sensitivity of about 630.8 nm/RIU. This result shows that the multi-mode resonator sensor fabricated via a simple process is competitive with other single-mode waveguide sensors.

Three-Terminal Ovonic Threshold Switch (3T-OTS) with Tunable Threshold Voltage for Versatile Artificial Sensory Neurons.

Inspired by information processing in biological systems, sensor-combined edge-computing systems attract attention requesting artificial sensory neurons as essential ingredients. Here, we introduce a simple and versatile structure of artificial sensory neurons based on a novel three-terminal Ovonic threshold switch (3T-OTS), which features an electrically controllable threshold voltage (Vth). Combined with a sensor driving an output voltage, this 3T-OTS generates spikes with a frequency depending on an external stimulus. As a proof of concept, we have built an artificial retinal ganglion cell (RGC) by combining a 3T-OTS and a photodiode. Furthermore, this artificial RGC is combined with the reservoir-computing technique to perform a classification of chest X-ray images for normal, viral pneumonia, and COVID-19 infections, releasing the recognition accuracy of about 86.5%. These results indicate that the 3T-OTS is highly promising for applications in neuromorphic sensory systems, providing a building block for energy-efficient in-sensor computing devices.

Visible-Light Activation of a Dissolved Organic Matter-TiO2 Complex Mediated via Ligand-to-Metal Charge Transfer.

Given the widespread use of TiO2, its release into aquatic systems and complexation with dissolved organic matter (DOM) are highly possible, making it important to understand how such interactions affect photocatalytic activity under visible light. Here, we show that humic acid/TiO2 complexes (HA/TiO2) exhibit photoactivity (without significant electron-hole activation) under visible light through ligand-to-metal charge transfer (LMCT). The observed visible-light activities for pollutant removal and bacterial inactivation are primarily linked to the generation of H2O2via the conduction band. By systematically considering molecular-scale interactions between TiO2 and organic functional groups in HA, we find a key role of phenolic groups in visible-light absorption and H2O2 photogeneration. The photochemical formation of H2O2 in river waters spiked with TiO2 is notably elevated above naturally occurring H2O2 generated from background organic constituents due to LMCT contribution. Our findings suggest that H2O2 generation by HA/TiO2 is related to the quantity and functional group chemistry of DOM, which provides chemical insights into photocatalytic activity and potential ecotoxicity of TiO2 in environmental and engineered systems.

Revisiting the Oxidizing Capacity of the Periodate-H2O2 Mixture: Identification of the Primary Oxidants and Their Formation Mechanisms.

This study reexamined the mechanisms for oxidative organic degradation by the binary mixture of periodate and H2O2 (PI/H2O2) that was recently identified as a new advanced oxidation process. Our findings conflicted with the previous claims that (i) hydroxyl radical (•OH) and singlet oxygen (1O2) contributed as the primary oxidants, and (ii) •OH production resulted from H2O2 reduction by superoxide radical anion (O2•-). PI/H2O2 exhibited substantial oxidizing capacity at pH < 5, decomposing organics predominantly by •OH. The likelihood of a switch in the major oxidant under varying pH conditions was revealed. IO4- as the major PI form under acidic conditions underwent one-electron reduction by H2O2 to yield radical intermediates, whereas H2I2O104- preferentially occurring at pH > 7 caused 1O2 generation through two-electron oxidation of H2O2. PI reduction by O2•- was suggested to be a key reaction in •OH production, on the basis of the electron paramagnetic resonance detection of methyl radicals in the dimethyl sulfoxide solutions containing PI and KO2, and the absence of deuterated and 18O-labeled hydroxylated intermediates during PI activation using D2O and H218O2. Finally, simple oxyanion mixing subsequent to electrochemical PI and H2O2 production achieved organic oxidation, enabling a potential strategy to minimize the use of chemicals.

Operational status of and upgrade plan for the 100-MeV proton linac at the Korea multi-purpose accelerator complex.

The report presents the operation status of and upgrade plan for the 100-MeV proton linac at the Korea Multi-purpose Accelerator Complex (KOMAC). First, an operation history of the 100-MeV linac since its commissioning in 2013, such as operation hours, user services, machine availabilities, and downtimes, is discussed. Second, the status of the beamlines in service or under development is described in a detailed manner. Finally, the Korea Spallation Neutron Source (KSNS), which is part of the upgrade plan for the 100-MeV proton linac to expand its utilization fields, is discussed.

Respiratory Failure during BIS-Guided Sedation in a Patient with Relapsing Polychondritis: A Case Report.

Relapsing polychondritis (RP) is a rare autoimmune disorder that causes inflammation and deterioration of cartilaginous structures such as the ears, nose, joints and laryngotracheobronchial tree. A 42-year-old man receiving treatment for RP underwent open reduction and internal fixation of a femur fracture under spinal anesthesia and with sedation by propofol and remifentanil. The level of sedation was monitored via a bispectral index (BIS), and maintained at between 60 and 80. At the end of the operation, he lost consciousness and displayed weak respiratory effort. During mask ventilation, the patient was judged to have respiratory failure due to high end-tidal CO2 (EtCO2) concentration and respiratory acidosis in an arterial-blood-gas analysis (ABGA). Ventilation through a properly inserted laryngeal-mask-airway or endotracheal intubation were impossible; instead, a surgical tracheotomy was performed. After recovering from respiratory failure with ventilatory support in the intensive care unit (ICU), he experienced the same symptoms three more times, requiring ventilatory support. He was discharged with bilevel positive-airway-pressure (BiPAP), after successful adaptation.

Chloride-Mediated Enhancement in Heat-Induced Activation of Peroxymonosulfate: New Reaction Pathways for Oxidizing Radical Production.

This study is the first to demonstrate the capability of Cl- to markedly accelerate organic oxidation using thermally activated peroxymonosulfate (PMS) under acidic conditions. The treatment efficiency gain allowed heat-activated PMS to surpass heat-activated peroxydisulfate (PDS). During thermal PMS activation at excess Cl-, accelerated oxidation of 4-chlorophenol (susceptible to oxidation by hypochlorous acid (HOCl)) was observed along with significant degradation of benzoic acid and ClO3- occurrence, which involved oxidants with low substrate specificity. This indicated that heat facilitated HOCl formation via nucleophilic Cl- addition to PMS and enabled free chlorine conversion into less selective oxidizing radicals. HOCl acted as a key intermediate in the major oxidant transition based on temperature-dependent variation in HOCl concentration profiles, kinetically retarded organic oxidation upon NH4+ addition, and enabled rapid organic oxidation in heated PMS/HOCl mixtures. Chlorine atom that formed via the one-electron oxidation of Cl- by the sulfate radical served as the primary oxidant and was involved in hydroxyl radical production. This was corroborated by the quenching effects of alcohols and bicarbonates, reactivity toward multiple organics, and electron paramagnetic resonance spectral features. PMS outperformed PDS in degrading benzoic acid during thermal activation operated in reverse osmosis concentrate, which was in conflict with the well-established superiority of heat-activated PDS.

Persulfate-Based Advanced Oxidation: Critical Assessment of Opportunities and Roadblocks.

Reports that promote persulfate-based advanced oxidation process (AOP) as a viable alternative to hydrogen peroxide-based processes have been rapidly accumulating in recent water treatment literature. Various strategies to activate peroxide bonds in persulfate precursors have been proposed and the capacity to degrade a wide range of organic pollutants has been demonstrated. Compared to traditional AOPs in which hydroxyl radical serves as the main oxidant, persulfate-based AOPs have been claimed to involve different in situ generated oxidants such as sulfate radical and singlet oxygen as well as nonradical oxidation pathways. However, there exist controversial observations and interpretations around some of these claims, challenging robust scientific progress of this technology toward practical use. This Critical Review comparatively examines the activation mechanisms of peroxymonosulfate and peroxydisulfate and the formation pathways of oxidizing species. Properties of the main oxidizing species are scrutinized and the role of singlet oxygen is debated. In addition, the impacts of water parameters and constituents such as pH, background organic matter, halide, phosphate, and carbonate on persulfate-driven chemistry are discussed. The opportunity for niche applications is also presented, emphasizing the need for parallel efforts to remove currently prevalent knowledge roadblocks.

Electrochemical Oxidation-Membrane Distillation Hybrid Process: Utilizing Electric Resistance Heating for Distillation and Membrane Defouling through Thermal Activation of Anodically Formed Persulfate.

This study reports distillation-based salt removal by Ohmic heating in a hybrid process, in which electrochemical oxidation (EO) and direct contact membrane distillation (DCMD) are performed sequentially. In addition to anodically destructing the organics, the hybrid process also separated the sulfate-based electrolytes from treated water through distillation, without consuming external energy, owing to the temperature of the aqueous sulfate solution being elevated to 70 °C via resistive heating. The hybrid process treated organic compounds in a nonselective fashion, whereas DCMD alone did not completely reject (semi)volatile organics. Integrating EO with DCMD made the hybrid process resistant toward the wetting phenomenon; the process exhibited a steady distillate flux and salt rejection as the initial loading of amphiphilic sodium dodecyl sulfate was increased to 0.3 mM. Anodic persulfate formation from the sulfate and Ohmic heating caused an in situ yield of the sulfate radical in the feed solution; this eliminated membrane fouling, according to the observation that the water flux, which was drastically reduced upon adding alginate, was recovered immediately after an electric current was applied. The hybrid process concurrently decomposed spiked organics and removed naturally present inorganic ions in actual flue gas desulfurization wastewater, without an external supply of electrolyte and heat energy.