Conspectus During the last few decades, the design of catalytic systems for CO2 reduction has been extensively researched and generally involves (1) traditional approaches using molecular ...organic/organometallic materials and heterogeneous inorganic semiconductors and (2) combinatory approaches wherein these materials are combined as needed. Recently, we have devised a number of new TiO2-mediated multicomponent hybrid systems that synergistically integrate the intrinsic merits of various materials, namely, molecular photosensitizers/catalysts and n-type TiO2 semiconductors, and lower the energetic and kinetic barriers between components. We have termed such multicomponent hybrid systems assembled from the hybridization of various organic/inorganic/organometallic units in a single platform inorganometallic photocatalysts. The multicomponent inorganometallic (MIOM) hybrid system onto which the photosensitizer and catalyst are coadsorbed efficiently eliminates the need for bulk-phase diffusion of the components and avoids the accumulation of radical intermediates that invokes a degradation pathway, in contrast to the homogeneous system, in which the free reactive species are concentrated in a confined reaction space. In particular, in energetic terms, we discovered that in nonaqueous media, the conduction band (CB) levels of reduced TiO2 (TiO2(e–)) are positioned at a higher level (in the range −1.5 to −1.9 V vs SCE). This energetic benefit of reduced TiO2 allows smooth electron transfer (ET) from injected electrons (TiO2(e–)) to the coadsorbed CO2 reduction catalyst, which requires relatively high reducing power (at least more than −1.1 V vs SCE). On the other hand, the existence of various shallow surface trapping sites and surface bands, which are 0.3–1.0 eV below the CB of TiO2, efficiently facilitates electron injection from any photosensitizer (including dyes having low excited energy levels) to TiO2 without energetic limitation. This is contrasted with most photocatalytic systems, wherein successive absorption of single high-energy photons is required to produce excited states with enough energy to fulfill photocatalytic reaction, which may allow unwanted side reactions during photocatalysis. In this Account, we present our recent research efforts toward advancing these MIOM hybrid systems for photochemical CO2 reduction and discuss their working mechanisms in detail. Basic ET processes within the MIOM system, including intervalence ET in organic/organometallic redox systems, metal-to-ligand charge transfer of organometallic complexes, and interfacial/outer-sphere charge transfer between components, were investigated by conducting serial photophysical and electrochemical analyses. Because such ET events occur primarily at the interface between the components, the efficiency of interfacial ET between the molecular components (organic/organometallic photosensitizers and molecular reduction catalysts) and the bulk inorganic solid (mainly n-type TiO2 semiconductors) has a significant influence on the overall photochemical reaction kinetics and mechanism. In some TiO2-mediated MIOM hybrids, the chemical attachment of organic or organometallic photosensitizing units onto TiO2 semiconductors efficiently eliminates the step of diffusion/collision-controlled ET between components and prevents the accumulation of reactive species (oxidatively quenched cations or reductively quenched anions) in the reaction solution, ensuring steady photosensitization over an extended reaction period. The site isolation of a single-site organometallic catalyst employing TiO2 immobilization promotes the monomeric catalytic pathway during the CO2 reduction process, resulting in enhanced product selectivity and catalytic performance, including lifetime extension. In addition, as an alternative inorganic solid scaffold, the introduction of a host porphyrin matrix (interlinked in a metal–organic framework (MOF) material) led to efficient and durable photocatalytic CO2 conversion by the new MOF–Re(I) hybrid as a result of efficient light harvesting/exciton migration in the porphyrinic MOF and rapid quenching of the photogenerated electrons by the doped Re(I) catalytic sites. Overall, the case studies presented herein provide valuable insights for the rational design of advanced multicomponent hybrid systems for artificial photosynthesis involving CO2 reduction.
A focused microwave thermotherapy system for non-invasively treating cancerous tumors has recently been actively developed. To accurately focus on the target location, the system needs information ...about the patient’s body boundary. However, a water bolus is placed between the human body and the microwave applicators to allow the microwave to penetrate the body more easily and cool the body’s skin. The structural configuration makes it difficult to measure the body boundary. In this paper, we present a body boundary measurement method using multiple line lasers and cameras for the application of a focused microwave thermotherapy system. Even with a lack of acquired boundary data, a completely closed boundary line can be reconstructed. In addition, real-time movement tracking is possible as it can be measured quickly, even in situations where the patient is moving, such as breathing and wriggling. The performance is verified with several indicators in a water-filled experimental testbed.
Abstract
For kesterite copper zinc tin sulfide/selenide (CZTSSe) solar cells to enter the market, in addition to efficiency improvements, the technological capability to produce flexible and ...large-area modules with homogeneous properties is necessary. Here, we report a greater than 10% efficiency for a cell area of approximately 0.5 cm
2
and a greater than 8% efficiency for a cell area larger than 2 cm
2
of certified flexible CZTSSe solar cells. By designing a thin and multi-layered precursor structure, the formation of defects and defect clusters, particularly tin-related donor defects, is controlled, and the open circuit voltage value is enhanced. Using statistical analysis, we verify that the cell-to-cell and within-cell uniformity characteristics are improved. This study reports the highest efficiency so far for flexible CZTSSe solar cells with small and large areas. These results also present methods for improving the efficiency and enlarging the cell area.
To determine whether the TyG index, a product of the levels of triglycerides and fasting plasma glucose (FPG) might be a valuable marker for predicting future diabetes.
A total of 5,354 nondiabetic ...subjects who had completed their follow-up visit for evaluating diabetes status were selected from a large cohort of middle-aged Koreans in the Chungju Metabolic Disease Cohort study. The risk of diabetes was assessed according to the baseline TyG index, calculated as lnfasting triglycerides (mg/dL) × FPG (mg/dL)/2. The median follow-up period was 4.6 years.
During the follow-up period, 420 subjects (7.8%) developed diabetes. The baseline values of the TyG index were significantly higher in these subjects compared with nondiabetic subjects (8.9 ± 0.6 vs. 8.6 ± 0.6; P<0.0001) and the incidence of diabetes increased in proportion to TyG index quartiles. After adjusting for age, gender, body mass index, waist circumference, systolic blood pressure, high-density lipoprotein (HDL)-cholesterol level, a family history of diabetes, smoking, alcohol drinking, education level and serum insulin level, the risk of diabetes onset was more than fourfold higher in the highest vs. the lowest quartile of the TyG index (relative risk, 4.095; 95% CI, 2.701-6.207). The predictive power of the TyG index was better than the triglyceride/HDL-cholesterol ratio or the homeostasis model assessment of insulin resistance.
The TyG index, a simple measure reflecting insulin resistance, might be useful in identifying individuals at high risk of developing diabetes.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Currently, wind energy harvesting is in the limelight. However, with the existing electromagnetic wind generators, it is difficult to harvest multifariously‐wasted breezes. To harvest energy from ...winds at a wide range of speeds, wind‐driven triboelectric nanogenerators (TENGs) are studied. However, a critical limitation of general wind‐driven TENGs is that their power output is low. Therefore, an innovative strategy is necessary to generate high output power even from breeze. Herein, an approach to test a charge‐polarization‐based flutter‐driven TENG (CPF‐TENG) with ambient air ionizing channel (AAIC) is reported. Owing to AAIC, the device generates peak voltage and current outputs of 2000 V and 4 A, respectively. Moreover, because the proposed CPF‐TENG can generate power from breeze, it can be stacked in series to completely harvest wind energy. The stacked CPF‐TENG is demonstrated to operate 3000 light‐emitting diodes (LEDs) and 12 hygrometers, separately, and produce hydrogen at a rate of 342.3 µL h−1 with the electrolysis cell.
It is demonstrated charge‐polarization‐based flutter‐driven triboelectric nanogenerator (CPF‐TENG) that can generate high electrical output by utilizing ambient air ionizing channel (AAIC) is fabricated. Even with low velocity wind input, CPF‐TENG with AAIC can generate high electrical output so the stacked device can completely harvest unidirectional wind energy. Consequently, the device can turn on several electronics and produce 342.3 µL h−1 of hydrogen.
Diosgenin (a steroidal saponin of yam) has long been used as a raw material for the industrial production of steroid drugs, and reported to have a hypocholesterolemic effect by suppressing ...cholesterol absorption and increasing cholesterol secretion. Oxidative stress has been suggested as a main risk factor in the development of atherosclerosis. The aim of this study is to investigate the possible hypolipidemic and antioxidative effect of diosgenin on rats fed with a high-cholesterol diet supplemented with either 0.1% or 0.5% diosgenin for 6 weeks. We measured the lipid profile in the plasma and liver, lipid peroxidation and antioxidative enzyme activities in the plasma, erythrocyte and gene expression of antioxidative enzymes in the liver, and the oxidative DNA damage in lymphocytes. Diosgenin showed a decrease in the plasma and hepatic total cholesterol levels, but increased the plasma high-density lipoprotein (HDL) cholesterol level. Erythrocyte TBARS and lymphocyte DNA damage measured by the comet assay were decreased in the diosgenin supplemented group. Furthermore, diosgenin feeding enhanced the resistance to lymphocyte DNA damage caused by an oxidant challenge with H2O2. The antioxidative enzyme activities were also affected by diosgenin supplementation. Total superoxide dismutase (SOD) in the plasma and liver, glutathione peroxidase (GSH-Px) in erythrocytes, and catalase (CAT) in erythrocytes and liver were significantly increased in the 0.5% diosgenin group. The expression of antioxidative enzymes was up-regulated by diosgenin, the expression of GSH-Px being the highest in the 0.5% diosgenin group. These results suggest that diosgenin could be a very useful compound to control hypercholesterolemia by both improving the lipid profile and modulating oxidative stress.
Because of their efficient energy-transport properties, porphyrin-based metal–organic frameworks (MOFs) are attractive compounds for solar photochemistry applications. However, their absorption bands ...provide limited coverage in the visible spectral range for light-harvesting applications. We report here the functionalization of porphyrin-based MOFs with CdSe/ZnS core/shell quantum dots (QDs) for the enhancement of light harvesting via energy transfer from the QDs to the MOFs. The broad absorption band of the QDs in the visible region offers greater coverage of the solar spectrum by QD–MOF hybrid structures. We show through time-resolved emission studies that photoexcitation of the QDs is followed by energy transfer to the MOFs with efficiencies of more than 80%. This sensitization approach can result in a >50% increase in the number of photons harvested by a single monolayer MOF structure with a monolayer of QDs on the surface of the MOF.
We report the synthesis and characterization of two thin films (DA-MOF and L2-MOF) of porphyrin-based MOFs on functionalized surfaces using a layer-by-layer (LbL) approach. Profilometry measurements ...confirm that the film thickness increases systematically with number of growth cycles. Polarization excitation and fluorescence measurements indicate that the porphyrin units are preferentially oriented, while X-ray reflectivity scans point to periodic ordering. Ellipsometry measurements show that the films are highly porous. Since there are currently few methods capable of yielding microporous MOFs containing accessible free-base porphyrins, it is noteworthy that the LbL growth permits direct MOF incorporation of unmetalated porphyrins. Long-range energy transfer is demonstrated for both MOF films. The findings offer useful insights for subsequent fabrication of MOF-based solar energy conversion devices.
High-voltage direct-current (HVDC) systems are being widely employed in various applications owing to their advantages, such as bulk power transmission, long-distance transmission, and power-flow ...control. However, HVDC systems suffer from commutation failure, a major drawback that leads to increased device stress, interruptions in transmitted power, and problems related to protection relay setting, in turn, resulting in system instability during operation. Therefore, many studies have investigated the mitigation of commutation failure by considering its underlying factors, that is, ac voltage reduction, dc current increment, and crossing point shifts of phase voltage. However, these approaches are limited in that they are unable to mitigate intermittent commutation failure in a transient state. This study proposes an improved algorithm that mitigates commutation failure by considering the results of previous studies as well as the control characteristics of HVDC systems. The proposed algorithm is tested in various scenarios, and the test results verify its feasibility.
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