Thickness Optimization of Charge Transport Layers on Perovskite Solar Cells for Aerospace Applications.

In aerospace applications, SiOx deposition on perovskite solar cells makes them more stable. However, the reflectance of the light changes and the current density decreases can lower the efficiency of the solar cell. The thickness of the perovskite material, ETL, and HTL must be re-optimized, and testing the number of cases experimentally takes a long time and costs a lot of money. In this paper, an OPAL2 simulation was used to find the thickness and material of ETL and HTL that reduces the amount of light reflected by the perovskite material in a perovskite solar cell with a silicon oxide film. In our simulations, we used an air/SiO2/AZO/transport layer/perovskite structure to find the ratio of incident light to the current density generated by the perovskite material and the thickness of the transport layer to maximize the current density. The results showed that when 7 nm of ZnS material was used for CH3NH3PbI3-nanocrystalline perovskite material, a high ratio of 95.3% was achieved. In the case of CsFAPbIBr with a band gap of 1.70 eV, a high ratio of 94.89% was shown when ZnS was used.

Effect of Hydrogen Annealing on Performances of BN-Based RRAM.

BN-based resistive random-access memory (RRAM) has emerged as a potential candidate for non-volatile memory (NVM) in aerospace applications, offering high thermal conductivity, excellent mechanical, and chemical stability, low power consumption, high density, and reliability. However, the presence of defects and trap states in BN-based RRAM can limit its performance and reliability in aerospace applications. As a result, higher set voltages of 1.4 and 1.23 V were obtained for non-annealed and nitrogen-annealed BN-based RRAM, respectively, but lower set voltages of 1.06 V were obtained for hydrogen-annealed BN-based RRAM. In addition, the hydrogen-annealed BN-based RRAM showed an on/off ratio of 100, which is 10 times higher than the non-annealed BN-based RRAM. We observed that the LRS changed to the HRS state before 10,000 s for both the non-annealed and nitrogen-annealed BN-based RRAMs. In contrast, the hydrogen-annealed BN-based RRAM showed excellent retention characteristics, with data retained up to 10,000 s.

Correlation between Sensing Accuracy and Read Margin of a Memristor-Based NO Gas Sensor Array Estimated by Neural Network Analysis.

Memristor-based gas sensors (gasistors) have been considered as the most promising candidate for detecting NO gas suitable for neural network (NN) analysis. In this work, in order to solve an overfitting issue arising from the training data when using a single gasistor, which degrades the accuracy of NN, we here propose a metal-insulator-silicon (MIS)-structured Zr3N4-based gasistor array that results in an improvement in both the accuracy of the NN analysis and the efficiency of the operating power. As a result, the proposed gasistor array showed a decrease of epoch and a 2.5% improvement of prediction accuracy at room temperature compared to single cells with metal/insulator/metal (MIM) and MIS structures. These results imply that an array structure based on MIS can efficiently solve the overfitting issue by receiving multiple responses at once, compared to a single gas sensor that obtains one response per sensing.

Influence of WO3-Based Antireflection Coatings on Current Density in Silicon Heterojunction Solar Cells.

Antireflection coatings (ARCs) with an indium thin oxide (ITO) layer on silicon heterojunction solar cells (SHJ) have garnered significant attention, which is due to their potential for increasing current density (Jsc) and enhancing reliability. We propose an additional tungsten trioxide (WO3) layer on the ITO/Si structure in this paper in order to raise the Jsc and demonstrate the influence on the SHJ solar cell. First, we simulate the Jsc characteristics for the proposed WO3/ITO/Si structure in order to analyze Jsc depending on the thickness of WO3 using an OPAL 2 simulator. As a result, the OPAL 2 simulation shows an increase in Jsc of 0.65 mA/cm2 after the 19 nm WO3 deposition on ITO with a doping concentration of 6.1 × 1020/cm2. We then fabricate the proposed samples and observe an improved efficiency of 0.5% with an increased Jsc of 0.75 mA/cm2 when using a 20 nm thick WO3 layer on the SHJ solar cell. The results indicate that the WO3 layer can be a candidate to improve the efficiency of SHJ solar cells with a low fabrication cost.

Low-Power Consumption IGZO Memristor-Based Gas Sensor Embedded in an Internet of Things Monitoring System for Isopropanol Alcohol Gas.

Low-power-consumption gas sensors are crucial for diverse applications, including environmental monitoring and portable Internet of Things (IoT) systems. However, the desorption and adsorption characteristics of conventional metal oxide-based gas sensors require supplementary equipment, such as heaters, which is not optimal for low-power IoT monitoring systems. Memristor-based sensors (gasistors) have been investigated as innovative gas sensors owing to their advantages, including high response, low power consumption, and room-temperature (RT) operation. Based on IGZO, the proposed isopropanol alcohol (IPA) gas sensor demonstrates a detection speed of 105 s and a high response of 55.15 for 50 ppm of IPA gas at RT. Moreover, rapid recovery to the initial state was achievable in 50 µs using pulsed voltage and without gas purging. Finally, a low-power circuit module was integrated for wireless signal transmission and processing to ensure IoT compatibility. The stability of sensing results from gasistors based on IGZO has been demonstrated, even when integrated into IoT systems. This enables energy-efficient gas analysis and real-time monitoring at ~0.34 mW, supporting recovery via pulse bias. This research offers practical insights into IoT gas detection, presenting a wireless sensing system for sensitive, low-powered sensors.

Highly Sensitive Oxygen Sensing Characteristics Observed in IGZO Based Gasistor in a Mixed Gas Ambient at Room Temperature.

Oxygen (O2) sensing in trace amounts and mixed gas is essential in many types of industries. Semiconductor sensors have proven to be invaluable tools for the O2 measurements in a wide concentration range, but the sensors are only able to quantify O2 in a concentration range of subppm, thus far, especially in mixed gas. We present in this paper a new concept for O2 sensing with incomparable sensitivity using IGZO-films with oxygen vacancy-based conducting filaments (CFs). O2 sensing relies on rupturing of the CFs, and the proposed device quickly recovers to the initial state using a pulse of 0.6 V/90 µs after the sensing. The proposed device has a high sensitivity of 14 even at an O2 concentration of 500 ppb, a detection limit of 150 ppb for O2 at RT, and excellent selectivity for O2 in mixed gas, which is remarkable compared to other gas sensors. The proposed device can be widely used in gas sensors especially for detecting O2 at a low ppb level, which is due to excellent sensing characteristics.

Insider vs. outsider CEO and firm performance: Evidence from the Covid-19 pandemic.

We examine the connection between firm performance and a CEO's previous position (inside or outside the firm), using Covid-19 as an exogenous shock. Firms led by insider CEOs outperformed those led by outsider CEOs in terms of return on assets during the Covid-19 crisis period in 2020, but there was no performance differential in the period before the crisis. Additional tests indicate that outperformance under insider CEOs is observed in firms holding more cash and firms with a higher proportion of internally promoted non-CEO executives. These findings have important implications for boards of directors making CEO appointments.

Advanced Recovery and High-Sensitive Properties of Memristor-Based Gas Sensor Devices Operated at Room Temperature.

Fast recovery, high sensitivity, high selectivity, and room temperature (RT) sensing characteristics of NO gas sensors are essential for environmental monitoring, artificial intelligence, and inflammatory diagnosis of asthma patients. However, the conventional semiconductor-type gas sensors have poor sensing characteristics that need to be solved, such as slow recovery speeds (>360 s), low sensitivity (3.8), and high operating temperatures (>300 °C). We propose here a memristor-based NO gas sensor as a gasistor (gas sensor + memory resistor) with SnO2, Ta2O5, and HfO2 films, which successfully demonstrated the feasibility of fast reaction/recovery (<1 s/90 ns) and high sensitivities such as 11.66 and 5.22 in Ta2O5 and HfO2 gasistors for NO gas, at RT. Furthermore, so as to reinforce the selectivity in multigas ambient, we suggest a parallel circuit using three kinds of gasistors having different sensitivities for NO, O2, and C2H6 gases, which results in an improvement of selectivity for the selected gas at RT.

High-Intensity Warm-Up Increases Anaerobic Energy Contribution during 100-m Sprint.

This study aimed to evaluate the effects of warm-up intensity on energetic contribution and performance during a 100-m sprint. Ten young male sprinters performed 100-m sprints following both a high-intensity warm-up (HIW) and a low-intensity warm-up (LIW). Both the HIW and LIW were included in common baseline warm-ups and interventional warm-ups (eight 60-m runs, HIW; 60 to 95%, LIW; 40% alone). Blood lactate concentration [La-], time trial, and oxygen uptake (VO2) were measured. The different energy system contribution was calculated by using physiological variables. [La-1]Max following HIW was significantly higher than in LIW (11.86 ± 2.52 vs. 9.24 ± 1.61 mmol·L-1; p < 0.01, respectively). The 100-m sprint time trial was not significantly different between HIW and LIW (11.83 ± 0.57 vs. 12.10 ± 0.63 s; p > 0.05, respectively). The relative (%) phosphagen system contribution was higher in the HIW compared to the LIW (70 vs. 61%; p < 0.01, respectively). These results indicate that an HIW increases phosphagen and glycolytic system contributions as compared to an LIW for the 100-m sprint. Furthermore, an HIW prior to short-term intense exercise has no effect on a 100-m sprint time trial; however, it tends to improve times (decreased 100-m time trial; -0.27 s in HIW vs. LIW).

Effects of Individualized Low-Intensity Exercise and Its Duration on Recovery Ability in Adults.

Exercise is recommended to increase physical health and performance. However, it is unclear how low-intensity exercise (LIE) of different durations may affect or improve recovery ability. This study aimed to investigate how LIE-duration with the same volume affects recovery ability in adults. Twenty healthy male adults participated in this study. Participants were randomly assigned to the 30-min (n = 10) or the 1-h LIE group (n = 10). The intervention included sixteen exercise sessions/four weeks with a 30-min LIE group, and eight exercise sessions/four weeks with a 1-h LIE group. Heart rate (HR) corresponding to <2 mmol∙L-1 blood lactate (La-) was controlled for LIE. Pre- and post-testing was conducted before and after 4-week LIE and tests included jogging/running speed (S), HR, and differences (delta; ∆) in HR and S between pre- and post-testing at 1.5, 2.0, and 4.0 mmol∙L-1 La-. Only the HR at 2.0 mmol∙L-1 La- of the 30-min LIE group was decreased in the post-test compared to the pre-test (p = 0.043). The jogging/running speed of the 1-h LIE group was improved in the post-test compared to the pre-test (p < 0.001, p = 0.006, p = 0.002, respectively). ∆HR at 2.0 and ∆S between the 30-min and 1-h LIE group at 1.5, 2.0, and 4.0 mmol∙L-1 La- were significantly different (p = 0.023, p < 0.001, p = 0.002, and p = 0.019, respectively). Furthermore, moderate to high positive correlations between ∆HR and ∆S of all subjects at 1.5 (r = 0.77), 2.0 (r = 0.77), and 4.0 (r = 0.64) mmol∙L-1 La- were observed. The 1-h LIE group showed improved endurance not only in the low-intensity exercise domain, but also in the beginning of the moderate to high-intensity exercise domain while the 30-min LIE group was not affected by the 4-week LIE intervention. Therefore, LIE (<2.0 mmol∙L-1) for at least 1-h, twice a week, for 4 weeks is suggested to improve recovery ability in adults.

Policies and innovations to battle Covid-19 - A case study of South Korea.

OBJECTIVES: To describe how health care crisis resulting from the COVID-19 pandemic in South Korea has led to innovation and changes to government policy. This paper presents the significant cluster events, relevant developments of innovation, and economical impact in Korea that could inform policy makers on how to respond to health crises in the future. METHODS: Health care, economy, epidemiological data are collected from various sources including the Korea Centers for Disease Control and Prevention (KCDC) or other government sources. RESULTS: The KCDC jointly with medical professionals developed a series of innovations such as 1) Full contact tracing and rapid testing with a 12 h turnaround and 10 min movement tracking systems, 2) transparent disclosure of all contract tracing data to the public through a central database, 3) Drive-Through and Walk-Through testing methods, and 4) a 4 tier patient severity index and community treatment isolation centers. Korea moved from the 4th in the world for total confirmed cases in March down to 76th in August. CONCLUSIONS: Expedited enforcement of amended legislation acts to protect the healthcare workforce resulted in only 10 healthcare professionals contracting the virus while caring for Covid-19 patients. This has resulted in minimal human capital loss and the government was able to re-direct existing medical workforce to areas in need. The quarantine strategies implemented resulted in little need to lock down the whole economy but also limited the cost spent to gain a year of life to 193,848 Won (US$163).

Energy System Contributions and Physical Activity in Specific Age Groups during Exergames.

Exergames have been recommended as alternative ways to increase the health benefits of physical exercise. However, energy system contributions (phosphagen, glycolytic, and oxidative) of exergames in specific age groups remain unclear. The purpose of this study was to investigate the contributions of three energy systems and metabolic profiles in specific age groups during exergames. Seventy-four healthy males and females participated in this study (older adults, n = 26: Age of 75.4 ± 4.4 years, body mass of 59.4 ± 8.7 kg, height of 157.2 ± 8.6 cm; adults, n = 24: Age of 27.8 ± 3.3 years, body mass of 73.4 ± 17.8 kg, height of 170.9 ± 11.9 cm; and adolescents, n = 24: Age of 14 ± 0.8 years, body mass of 71.3 ± 11.5 kg, height of 173.3 ± 5.2 cm). To evaluate the demands of different energy systems, all participants engaged in exergames named Action-Racing. Exergames protocol comprised whole-body exercises such as standing, sitting, stopping, jumping, and arm swinging. During exergames, mean heart rate (HRmean), peak heart rate (HRpeak), mean oxygen uptake (VO2mean), peak oxygen uptake (VO2peak), peak lactate (Peak La-), difference in lactate (ΔLa-), phosphagen (WPCr), glycolytic (WLa-), oxidative (WAER), and total energy demands (WTotal) were analyzed. The contribution of the oxidative energy system was higher than that of the phosphagen or glycolytic energy system (65.9 ± 12% vs. 29.5 ± 11.1% or 4.6 ± 3.3%, both p < 0.001). The contributions of the total energy demands and oxidative system in older adults were significantly lower than those in adults and adolescents (72.1 ± 28 kJ, p = 0.028; 70.3 ± 24.1 kJ, p = 0.024, respectively). The oxidative energy system was predominantly used for exergames applied in the current study. In addition, total metabolic work in older adults was lower than that in adolescents and adults. This was due to a decrease in the oxidative energy system. For future studies, quantification of intensity and volume is needed to optimize exergames. Such an approach plays a crucial role in encouraging physical activity in limited spaces.

Improvement of Ohmic Contact Between the Indium Tin Oxide and Copper-Plated Contact of Solar Cells by Using the Cu-Sn Alloy Film.

Copper plating has been considered as a future metallization technique to reduce metal contact area and material cost in silicon heterojunction (SHJ) solar cells. In this paper, a Cu-Sn alloy film is used as a seed layer material on an indium tin oxide (ITO) layer with the goal to enhance contact resistivity between the seed and ITO layer. The contact resistivity between the seed layer and ITO is an important parameter because low contact resistivity is required for the high fill factor of the solar cells. In addition, it was confirmed that tin diffusion to ITO can affect contact resistivity by annealing samples having a Cu-Sn seed layer. Contact resistivity values of the samples were extracted by using transfer length method (TLM). Atomic percentage of tin in the Cu-Sn film was measured by the energy dispersive spectrometer (EDS). Also, tape tests were carried out to simply confirm the adhesion of contacts with the Cu-Sn seed layer.

Ultrarapid and ultrasensitive electrical detection of proteins in a three-dimensional biosensor with high capture efficiency.

The realization of a high-throughput biosensor platform with ultrarapid detection of biomolecular interactions and an ultralow limit of detection in the femtomolar (fM) range or below has been retarded due to sluggish binding kinetics caused by the scarcity of probe molecules on the nanostructures and/or limited mass transport. Here, as a new method for the highly efficient capture of biomolecules at extremely low concentration, we tested a three-dimensional (3D) platform of a bioelectronic field-effect transistor (bio-FET) with vertically aligned and highly dense one-dimensional (1D) ZnO nanorods (NRs) as a sensing surface capped by an ultrathin TiO2 layer for improved electrolytic stability on a chemical-vapor-deposited graphene (Gr) channel. The ultrarapid detection capability with a very fast response time (∼1 min) at the fM level of proteins in the proposed 3D bio-FET is primarily attributed to the fast binding kinetics of the probe-target proteins due to the small diffusion length of the target molecules to reach the sensor surface and the substantial number of probe molecules available on the largely increased surface area of the vertical ZnO NRs. This new 3D electrical biosensor platform can be easily extended to other electrochemical nanobiosensors and has great potential for practical applications in miniaturized biosensor integrated systems.

Ultrahigh Responsivity in Graphene-ZnO Nanorod Hybrid UV Photodetector.

Ultraviolet (UV) photodetectors based on ZnO nanostructure/graphene (Gr) hybrid-channel field-effect transistors (FETs) are investigated under illumination at various incident photon intensities and wavelengths. The time-dependent behaviors of hybrid-channel FETs reveal a high sensitivity and selectivity toward the near-UV region at the wavelength of 365 nm. The devices can operate at low voltage and show excellent selectivity, high responsivity (RI ), and high photoconductive gain (G). The change in the transfer characteristics of hybrid-channel FETs under UV light illumination allows to detect both photovoltage and photocurrent. The shift of the Dirac point (V Dirac ) observed during UV exposure leads to a clearer explanation of the response mechanism and carrier transport properties of Gr, and this phenomenon permits the calculation of electron concentration per UV power density transferred from ZnO nanorods and ZnO nanoparticles to Gr, which is 9 × 10(10) and 4 × 10(10) per mW, respectively. The maximum values of RI and G infer from the fitted curves of RI and G versus UV intensity are 3 × 10(5) A W(-1) and 10(6) , respectively. Therefore, the hybrid-channel FETs studied herein can be used as UV sensing devices with high performance and low power consumption, opening up new opportunities for future optoelectronic devices.

Structural and transcriptional analyses of a purine nucleotide-binding protein from Pyrococcus furiosus: a component of a novel, membrane-bound multiprotein complex unique to this hyperthermophilic archaeon.

The open-reading frame PF0895 in the genome of the hyperthermophilic archaeon, Pyrococcus furiosus, encodes a 206-residue protein (M(R )23,152). The structure of the recombinant protein was solved by single isomorphous replacement with anomalous scattering (SIRAS) using a mercury derivative. It has been refined to 1.70 A with a crystallographic R and R(free )values of 19.7% and 22.3%, respectively. The PF0895 structure is similar to those of the ATP binding cassettes observed in the ABC transporter family. However, bioinformatics and molecular analyses indicate that PF0895 is not part of the expected five-gene operon that encodes a typical prokaryotic solute-binding ABC transporter. Rather, transcriptional profiling data show that PF0895 is part of a novel four-gene operon (PF0895-PF0896-PF0897-PF0897.1) where only PF0895 has homologs in other organisms. Interestingly, from genome analysis, P. furiosus itself contains a second version of this complex, encoded by PF1090-PF1093. From the structural studies we can only conclude that one of the subunits of this novel membrane complex, PF0895, and its homolog PF1090, likely bind a purine nucleotide. PF0895 is therefore predicted to be part of a membrane-bound multiprotein complex unrelated to ABC transporters that is so far unique to P. furiosus. It appears to play a role in the stress response, as its expression is down regulated when the organism is subjected to cold-shock, where cells are transferred from 95 degrees C, near the optimal growth temperature, to 72 degrees C, near the minimal growth temperature. The related PF1090-containing operon is unaffected by cold-shock and is independently regulated.

Structure of the hypothetical protein PF0899 from Pyrococcus furiosus at 1.85 A resolution.

The hypothetical protein PF0899 is a 95-residue peptide from the hyperthermophilic archaeon Pyrococcus furiosus that represents a gene family with six members. P. furiosus ORF PF0899 has been cloned, expressed and crystallized and its structure has been determined by the Southeast Collaboratory for Structural Genomics (http://www.secsg.org). The structure was solved using the SCA2Structure pipeline from multiple data sets and has been refined to 1.85 A against the highest resolution data set collected (a presumed gold derivative), with a crystallographic R factor of 21.0% and R(free) of 24.0%. The refined structure shows some structural similarity to a wedge-shaped domain observed in the structure of the major capsid protein from bacteriophage HK97, suggesting that PF0899 may be a structural protein.

Characterization of a corrinoid protein involved in the C1 metabolism of strict anaerobic bacterium Moorella thermoacetica.

The strict anaerobic, thermophilic bacterium Moorella thermoacetica metabolizes C1 compounds for example CO(2)/H(2), CO, formate, and methanol into acetate via the Wood/Ljungdahl pathway. Some of the key steps in this pathway include the metabolism of the C1 compounds into the methyl group of methylenetetrahydrofolate (MTHF) and the transfer of the methyl group from MTHF to the methyl group of acetyl-CoA catalyzed by methyltransferase, corrinoid protein and CO dehydrogenase/acetyl CoA synthase. Recently, we reported the crystallization of a 25 kDa methanol-induced corrinoid protein from M. thermoacetica (Zhou et al., Acta Crystallogr F 2005; 61:537-540). In this study we analyzed the crystal structure of the 25 kDa protein and provide genetic and biochemical evidences supporting its role in the methanol metabolism of M. thermoacetia. The 25 kDa protein was encoded by orf1948 of contig 303 in the M. thermoacetica genome. It resembles similarity to MtaC the corrinoid protein of the methanol:CoM methyltransferase system of methane producing archaea. The latter enzyme system also contains two additional enzymes MtaA and MtaB. Homologs of MtaA and MtaB were found to be encoded by orf2632 of contig 303 and orf1949 of contig 309, respectively, in the M. thermoacetica genome. The orf1948 and orf1949 were co-transcribed from a single polycistronic operon. Metal analysis and spectroscopic data confirmed the presence of cobalt and the corrinoid in the purified 25 kDa protein. High resolution X-ray crystal structure of the purified 25 kDa protein revealed corrinoid as methylcobalamin with the imidazole of histidine as the alpha-axial ligand replacing benziimidazole, suggesting base-off configuration for the corrinoid. Methanol significantly activated the expression of the 25 kDa protein. Cyanide and nitrate inhibited methanol metabolism and suppressed the level of the 25 kDa protein. The results suggest a role of the 25 kDa protein in the methanol metabolism of M. thermoacetica.

Salvaging Pyrococcus furiosus protein targets at SECSG.

Proteins derived from the coding regions of Pyrococcus furiosus are targets for three-dimensional X-ray and NMR structure determination by the Southeast Collaboratory for Structural Genomics (SECSG). Of the 2,200 open reading frames (ORFs) in this organism, 220 protein targets were cloned and expressed in a high-throughput (HT) recombinant system for crystallographic studies. However, only 96 of the expressed proteins could be crystallized and, of these, only 15 have led to structures. To address this issue, SECSG has recently developed a two-tier approach to protein production and crystallization. In this approach, tier-1 efforts are focused on producing protein for new Pfu(italics?) targets using a high-throughput approach. Tier-2 protein production efforts support tier-1 activities by (1) producing additional protein for further crystallization trials, (2) producing modified protein (further purification, methylation, tag removal, selenium labeling, etc) as required and (3) serving as a salvaging pathway for failed tier-1 proteins. In a recent study using this two-tiered approach, nine structures were determined from a set of 50 Pfu proteins, which failed to produce crystals suitable for X-ray diffraction analysis. These results validate this approach and suggest that it has application to other HT crystal structure determination applications.