Hierarchical Joint Graph Learning and Multivariate Time Series Forecasting

Multivariate time series is prevalent in many scientific and industrial domains. Modeling multivariate signals is challenging due to their long-range temporal dependencies and intricate interactions--both direct and indirect. To confront these complexities, we introduce a method of representing multivariate signals as nodes in a graph with edges indicating interdependency between them. Specifically, we leverage graph neural networks (GNN) and attention mechanisms to efficiently learn the underlying relationships within the time series data. Moreover, we suggest employing hierarchical signal decompositions running over the graphs to capture multiple spatial dependencies. The effectiveness of our proposed model is evaluated across various real-world benchmark datasets designed for long-term forecasting tasks. The results consistently showcase the superiority of our model, achieving an average 23\% reduction in mean squared error (MSE) compared to existing models.Comment: Temporal Graph Learning Workshop @ NeurIPS 2023, New Orleans, United State

Selective electrochemical reduction of nitric oxide to hydroxylamine by atomically dispersed iron catalyst

Electrocatalytic conversion of nitrogen oxides to value-added chemicals is a promising strategy for mitigating the human-caused unbalance of the global nitrogen-cycle, but controlling product selectivity remains a great challenge. Here we show iron–nitrogen-doped carbon as an efficient and durable electrocatalyst for selective nitric oxide reduction into hydroxylamine. Using in operando spectroscopic techniques, the catalytic site is identified as isolated ferrous moieties, at which the rate for hydroxylamine production increases in a super-Nernstian way upon pH decrease. Computational multiscale modelling attributes the origin of unconventional pH dependence to the redox active (non-innocent) property of NO. This makes the rate-limiting NO adsorbate state more sensitive to surface charge which varies with the pH-dependent overpotential. Guided by these fundamental insights, we achieve a Faradaic efficiency of 71% and an unprecedented production rate of 215 μmol cm−2 h−1 at a short-circuit mode in a flow-type fuel cell without significant catalytic deactivation over 50 h operation. © 2021, The Author(s).1

Paroxysmal Atrial Fibrillation Presenting as Acute Lower Limb Ischemia

An ischemic foot can be developed by acute arterial occlusion. Given proper treatment within critical time, the patient can avoid foot amputation and death. Early proper diagnosis and treatment by family physician at the initial clinical interviewing is important in saving the affected leg and the life. Thrombosis and embolism are the common causes of acute arterial occlusion. Thrombosis mostly arises from underlying cardiac disease such as arrhythmia, coronary artery disease and valvular heart disease while arterial occlusion by embolism can be shown on a narrowed artery related with systemic atherosclerosis. Because the treatment options depend on the underlying cause of the acute ischemic foot, it is important to identify the cause of acute ischemic foot. At this paper, we reported a case that the cause of acute ischemic foot of the patient proved paroxysmal atrial fibrillation after some diagnostic tests

Nafion Modified TiO2 Nanoparticles for an Artificial Photosynthesis

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Hierarchical Inorganic Assemblies for Artificial Photosynthesis.

Artificial photosynthesis is an attractive approach for renewable fuel generation because it offers the prospect of a technology suitable for deployment on highly abundant, non-arable land. Recent leaps forward in the development of efficient and durable light absorbers and catalysts for oxygen evolution and the growing attention to catalysts for carbon dioxide activation brings into focus the tasks of hierarchically integrating the components into assemblies for closing of the photosynthetic cycle. A particular challenge is the efficient coupling of the multi-electron processes of CO2 reduction and H2O oxidation. Among the most important requirements for a complete integrated system are catalytic rates that match the solar flux, efficient charge transport between the various components, and scalability of the photosynthetic assembly on the unprecedented scale of terawatts in order to have impact on fuel consumption. To address these challenges, we have developed a heterogeneous inorganic materials approach with molecularly precise control of light absorption and charge transport pathways. Oxo-bridged heterobinuclear units with metal-to-metal charge-transfer transitions absorbing deep in the visible act as single photon, single charge transfer pumps for driving multi-electron catalysts. A photodeposition method has been introduced for the spatially directed assembly of nanoparticle catalysts for selective coupling to the donor or acceptor metal of the light absorber. For CO2 reduction, a Cu oxide cluster is coupled to the Zr center of a ZrOCo light absorber, while coupling of an Ir nanoparticle catalyst for water oxidation to the Co donor affords closing of the photosynthetic cycle of CO2 conversion by H2O to CO and O2. Optical, vibrational, and X-ray spectroscopy provide detailed structural knowledge of the polynuclear assemblies. Time resolved visible and rapid-scan FT-IR studies reveal charge transfer mechanisms and transient surface intermediates under photocatalytic conditions for guiding performance improvements. Separation of the water oxidation and carbon dioxide reduction half reactions by a membrane is essential for efficient photoreduction of CO2 by H2O to liquid fuel products. A concept of a macroscale artificial photosystem consisting of arrays of Co oxide-silica core-shell nanotubes is introduced in which each tube operates as a complete, independent photosynthetic unit with built-in membrane separation. The ultrathin amorphous silica shell with embedded molecular wires functions as a proton conducting, molecule impermeable membrane. Photoelectrochemical and transient optical measurements confirm tight control of charge transport through the membrane by the orbital energetics of the wire molecules. Hierarchical arrangement of the components is accomplished by a combination of photodeposition, controlled anchoring, and atomic layer deposition methods

Photocatalytic enhancement of cesium removal by Prussian blue-deposited TiO2

After the Fukushima nuclear accident, tremendous efforts were made to treat radiocesium, radiostrontium, and other radioactive materials. For the first time, we demonstrate that a TiO2 photocatalyst can significantly enhance Cs adsorption by Prussian blue-deposited TiO2 (PB/TiO2) under UV irradiation. In this study, we synthesized PB/TiO2 using the photodeposition method. After the Cs ions were adsorbed on the PB/TiO2 in darkness, we then exposed the PB/TiO2 to UV light irradiation. This resulted in a further increase in Cs ion adsorption of more than 10 times the amount adsorbed in darkness. This photocatalytic-enhanced adsorption of Cs ions was not observed on PB mixed with SiO2, nor under visible light irradiation. We investigated the effects of PB concentration, PB/TiO2 concentration, and gas purging on both dark and photocatalytic-enhanced adsorption of Cs ions by PB/TiO2. Based on the results, we suggest that the photocatalytic-enhanced adsorption of Cs ions on PB/TiO2 is due to photocatalytic reduction of PB, which leads to additional adsorption of Cs ions. The change in solution color before and after the reaction, and the change in solution pH in the dark and during UV irradiation strongly support this suggestion. The photocatalytic-enhanced adsorption of Cs ions was equivalent during radioactive 137Cs removal, indicating important applications for pollutant removal from contaminated water. © 2018 Elsevier B.V.1

Directed Assembly of Cuprous Oxide Nanocatalyst for CO₂ Reduction Coupled to Heterobinuclear ZrOCo^II Light Absorber in Mesoporous Silica

Hierarchical assembly of an oxo-bridged binuclear ZrOCo^II light absorber unit coupled to a cuprous oxide nanocluster catalyst for CO₂ reduction on mesoporous silica support is demonstrated. The proper positioning of the Cu oxide cluster was achieved by photodeposition of a [Cu­(NCCH₃)₄]²⁺precursor by visible light excitation of the ZrOCo charge transfer chromophore, followed by mild calcination at 350 C. Illumination of the Cu_<i>x</i>O_<i>y</i>-ZrOCo unit so formed in the presence of a diethylamine electron donor resulted in the reduction of surface Cu centers to Cu⁰ as demonstrated by the characteristic infrared band of adsorbed ¹³CO probe molecules at 2056 cm^–1. For analogous Cu_<i>x</i>O_<i>y</i>-TiOCo^II units, the oxidation state makeup of the surface Cu centers was dominated by Cu^I, and the Cu⁰, Cu^I, and Cu^II composition was found to depend on the wavelength of MMCT excitation. The observed strong dependence of the CO₂ photoreduction yield on the oxidation state of the surface Cu centers directly proves that CO₂ is reduced on the Cu_<i>x</i>O_<i>y</i> surface, thus establishing that the ZrOCo^II unit functions as light absorber, donating electrons to the Cu_<i>x</i>O_<i>y</i> catalyst on whose surface CO₂ is reduced

Environmentally benign synthesis of CuInS2/ZnO heteronanorods: visible light activated photocatalysis of organic pollutant/bacteria and study of its mechanism

Due to its high light absorption coefficient and appropriate bandgap, CuInS2 (CIS) has been receiving much attention as an absorber material for thin film solar cells and also as a visible light photocatalyst. Herein we present heterostructured CIS/ZnO nanorods (NRs) in an attempt to enhance light absorption and facilitate charge separation/transfer in the photocatalysis system. CIS nanoparticles (NPs) were directly deposited on ZnO nanorod arrays (NRAs) to fabricate heterostructured CIS/ZnO NRAs using an environmentally benign, non-hydrazine solution reaction. These heterostructured NRAs are immobilized on FTO glass, which has additional merits of recyclability and bias-applicability. The ideal type-II band structure of CIS/ZnO enables efficient charge separation/transfer, which is confirmed by PL (photoluminescence) decay measurements. Also, the 1D-ZnO NR structure facilitates fast charge transfer along with enhancing light absorption via light scattering. These synergistic effects improved the photocatalytic activity in both organic dye and bacteria decomposition. The photodecomposition efficiency was further enhanced with an aid of external bias. The underlying photocatalytic mechanism was also investigated through controlled experiments under various scavenging conditions. The results suggest that reactive oxygen species (ROS) formed by multistep reduction of O-2 play a main role in photocatalysis, while hole-induced photodecomposition is relatively deactivated due to the band structure of the heterostructures of CIS/ZnO.112sciescopuskc