Highly Sensitive and Selective Acetylene CuO/ZnO Heterostructure Sensors through Electrospinning at Lean O2 Concentration for Transformer Diagnosis.

Acetylene (C2H2) is a gas that can cause explosions in transformers even at low concentrations. Gas chromatography (GC) or photoacoustic spectroscopy (PAS) have been used to detect C2H2 during dissolved gas analysis (DGA), but they are not suitable for monitoring numerous transformers at substations. Even though metal oxide semiconductor (MOS) based C2H2 sensors have drawn much attention as a potential solution, existing MOS-based C2H2 sensors have low sensitivity toward C2H2 in the transformer environment (<2% O2 concentrations). This study develops high-performance C2H2 gas sensors for DGA using a heterostructure of CuO/ZnO (CZ) via the electrospinning process. Performance of various ratios of CZ composite nanofibers are compared in a transformer-like environment, and the optimal composition of CZ nanofibers for detection of C2H2 at 2% O2 concentration is proposed. The CuO:ZnO = 8:2 (CZ2) sensor achieves the highest response (Rg/Ra = 7.6 against 10 ppm of C2H2) toward low concentration of C2H2 at 200 °C with good stability (>10 h). In addition, the CZ2 sensor also shows a high selectivity (>5 times) to coexisting transformer oil gases which are H2, CH4, C2H4, C2H6, CO, and CO2. Overall, this study is the first to demonstrate a high performing DGA sensor under 2% O2 concentration that can provide a practical solution to monitoring the low concentration of C2H2 in transformers effectively.

The effects of mobile technology-based support on young women with depressive symptoms: A block randomized controlled trial.

BACKGROUND: The current body of knowledge highlights the potential role of mobile technology as a medium to deliver support for psychological and physical health. This study evaluated the influence of mobile technology support on depressive symptoms and physical activity in female university students. METHODS: A block randomized controlled trial design with a single site was used. Ninety-nine participants were block-randomized into 3 arms: Experimental Group 1 (emotional and informational support group), Experimental Group 2 (informational support group), and the control group. Interventions were delivered via mobile technology for 2 weeks. Data on depressive symptoms and physical activity were collected from 84 participants at baseline and on Days 8 and 15. Data analyses included descriptive statistics, t tests, one-way analysis of variance, and repeated-measures analysis of variance. RESULTS: This study showed no interaction effect of time and group on depressive symptom scores and physical activity, considering the emotional and informational support from mobile technology. However, Experimental Group 1 exhibited a significant reduction in depressive symptoms during the first week of the study compared to Experimental Group 2 and the control group. While physical activity in Experimental Group 2 and control group increased only during the first week of the study and subsequently decreased, Experimental Group 1 showed an initial increase during the first week that was sustained into the second week. CONCLUSIONS: Since informational and emotional support showed a strong effect over a short period of time, mobile technology offering emotional support could be used to provide crisis interventions for depression among young women when a short-term impact is required.

Stereoselective Approach for the Synthesis of Diverse 1'-Modified Carbanucleosides.

We describe an efficient and stereoselective synthesis of 1'-substituted-ß-carbocylic nucleosides 5 via gem-dichlorooxirane intermediate 7, which directly condensed with weak nucleophiles such as pyrimidines or purines. The formation of gem-dichlorooxirane 7 and direct nucleobase condensation exclusively proceeded in protic polar solvents like MeOH. This method provides a general and modular route for the late-stage diversification of 1'-modified nucleosides.

The rise and fall of face recognition awareness across the life span.

A core component of metacognition is cognitive awareness, insight into how one's cognitive abilities compare with others. Previous studies of cognitive awareness have focused on basic aspects of perception, memory, and learning. Further, studies of the awareness of one's social-cognitive abilities have been limited to examining awareness of others' thinking (i.e., theory of mind). The current study characterizes awareness of one's own social-cognitive abilities, specifically face recognition awareness, and examines its change across the life span. We used a large, web-based sample (N = 4,143) with a broad age range (ages 10-70), administering well-validated measures of objective (Cambridge Face Memory Test 3) and self-reported (Cambridge Face Memory Questionnaire) face recognition. We found a robust overall association between objective and self-reported face recognition (r = .42 in females, r = .36 in males). While we found that face recognition ability peaked in the early- to mid-30s, face recognition awareness peaked in the early- to mid-20s, was relatively stable throughout the 20s-40s, and declined in the 50s-60s. Relative subjective versus objective face recognition bias measures demonstrated that 10- to 18- and 51- to 70-year-olds overestimated their self-reported face recognition abilities in comparison with 19- to 50-year-olds. Finally, compared with males, females had greater face recognition awareness and a bias to relatively underestimate their face recognition abilities. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Atomic-Scale Homogeneous RuCu Alloy Nanoparticles for Highly Efficient Electrocatalytic Nitrogen Reduction.

Ruthenium (Ru) is the most widely used metal as an electrocatalyst for nitrogen (N2 ) reduction reaction (NRR) because of the relatively high N2 adsorption strength for successive reaction. Recently, it has been well reported that the homogeneous Ru-based metal alloys such as RuRh, RuPt, and RuCo significantly enhance the selectivity and formation rate of ammonia (NH3 ). However, the metal combinations for NRR have been limited to several miscible combinations of metals with Ru, although various immiscible combinations have immense potential to show high NRR performance. In this study, an immiscible combination of Ru and copper (Cu) is first utilized, and homogeneous alloy nanoparticles (RuCu NPs) are fabricated by the carbothermal shock method. The RuCu homogeneous NP alloys on cellulose/carbon nanotube sponge exhibit the highest selectivity and NH3 formation rate of ≈31% and -73 µmol h-1 cm-2 , respectively. These are the highest values of the selectivity and NH3 formation rates among existing Ru-based alloy metal combinations.

c-Axis-Oriented Platelets of Crystalline Hydroxyapatite in Biomimetic Intrafibrillar Mineralization of Polydopamine-Functionalized Collagen Type I.

Mineralized collagen fibrils are important basic building blocks of calcified tissues, such as bone and dentin. Polydopamine (PDA) can introduce functional groups, i.e., hydroxyl and amine groups, on the surfaces of type I collagen (Col-I) as possible nucleation sites of calcium phosphate (CaP) crystallization. Molecular bindings in between PDA and Col-I fibrils (Col-PDA) have been found to significantly reduce the interfacial energy. The wetting effect, mainly hydrophilicity due to the functional groups, escalates the degree of mineralization. The assembly of Col-I molecules into fibrils was initiated at the designated number of collagenous molecules and PDA. In contrast to the infiltration of amorphous calcium phosphate (ACP) precursors into the Col-I matrix by polyaspartic acid (pAsp), this collagen assembly process allows nucleation and ACP to exist in advance by PDA in the intrafibrillar matrix. PDA bound to specific sites, i.e., gap and overlap zones, by the regular arrangement of Col-I fibrils enhanced ACP nucleation and thus mineralization. As a result, the c-axis-oriented platelets of crystalline hydroxyapatite in the Col-I fibril matrix were observed in the enhanced mineralization through PDA functionalization.

Generation of high-density nanoparticles in the carbothermal shock method.

The carbothermal shock (CTS) method has attracted considerable attention in recent years because it enables the generation of finely controlled polyelemental alloy nanoparticles (NPs). However, fabricating high surface coverage of NPs with minimized exposure of the carbon substrate is essential for various electrochemical applications and has been a critical limitation in CTS method. Here, we developed a methodology for creating NPs with high surface coverage on a carbon substrate by maximizing defect sites of cellulose during CTS. Cu NPs with high surface coverage of ~85%, various single NPs and polyelemental alloy NPs were densely fabricated with high uniformity and dispersity. The synthesized Cu NPs on cellulose/carbon paper substrate were used in electrocatalytic CO2 reduction reaction showing selectivity to ethylene of ~49% and high stability for over 30 hours of reaction. Our cellulose-derived CTS method enables the greater availability of polyelemental NPs for a wide range of catalytic and electrochemical applications.

Molecular and functional characterization of two pyruvate decarboxylase genes, PDC1 and PDC5, in the thermotolerant yeast Kluyveromyces marxianus.

Pyruvate decarboxylase (Pdc) is a cytosolic enzyme located at the branch point between fermentative and respiratory sugar catabolism. Here, we identified and functionally characterized KmPDC1 and KmPDC5 encoding two homologs of Pdc in the thermotolerant yeast Kluyveromyces marxianus KCTC 17555. Despite the conservation of important Pdc domains, a few amino acid sequences essential for enzymatic activity are not conserved in KmPdc5p. Deletion of KmPDC1 alone eliminated most of Pdc activity, but the growth of the Kmpdc1Δ strain on glucose was comparable to that of the wild type (WT) strain under aerobic conditions. In contrast to the WT, Kmpdc1Δ could not grow on glucose under oxygen-limited conditions. The KmPDC5 deletion did not generate any apparent change in Pdc activity or growth patterns under several tested conditions. Whereas the expression of KmPDC1 was enhanced by glucose, the basic expression levels of KmPDC5 were very low, without a detectable difference between glucose and nonfermentable carbon sources. Moreover, KmPDC5 overexpression was unable to complement the growth defect of Kmpdc1Δ in the presence of antimycin A, and the purified recombinant KmPdc5p was inactive in Pdc activity assay, supporting the notion that KmPdc5p may lack Pdc enzymatic activity. Notably, compared to the WT, Kmpdc1Δ single and Kmpdc1Δpdc5Δ double mutants produced significantly less glycerol, acetate, and ethanol while accumulating pyruvate. Altogether, our data indicate that a single deletion of KmPDC1 is sufficient in Crabtree-negative K. marxianus strains to generate a starting host strain for engineering of production of high-value biomaterials derived from pyruvate without byproduct formation.

A Polysulfide-Infiltrated Carbon Cloth Cathode for High-Performance Flexible Lithium-Sulfur Batteries.

For practical application of lithium-sulfur batteries (LSBs), it is crucial to develop sulfur cathodes with high areal capacity and cycle stability in a simple and inexpensive manner. In this study, a carbon cloth infiltrated with a sulfur-containing electrolyte solution (CC-S) was utilized as an additive-free, flexible, high-sulfur-loading cathode. A freestanding carbon cloth performed double duty as a current collector and a sulfur-supporting/trapping material. The active material in the form of Li2S6 dissolved in a 1 M LiTFSI-DOL/DME solution was simply infiltrated into the carbon cloth (CC) during cell fabrication, and its optimal loading amount was found to be in a range between 2 and 10 mg/cm² via electrochemical characterization. It was found that the interwoven carbon microfibers retained structural integrity against volume expansion/contraction and that the embedded uniform micropores enabled a high loading and an efficient trapping of sulfur species during cycling. The LSB coin cell employing the CC-S electrode with an areal sulfur loading of 6 mg/cm² exhibited a high areal capacity of 4.3 and 3.2 mAh/cm² at C/10 for 145 cycles and C/3 for 200 cycles, respectively, with minor capacity loss (<0.03%/cycle). More importantly, such high performance could also be realized in flexible pouch cells with dimensions of 2 cm × 6 cm before and after 300 bending cycles. Simple and inexpensive preparation of sulfur cathodes using CC-S electrodes, therefore, has great potential for the manufacture of high-performance flexible LSBs.

Introduction of a bacterial acetyl-CoA synthesis pathway improves lactic acid production in Saccharomyces cerevisiae.

Acid-tolerant Saccharomyces cerevisiae was engineered to produce lactic acid by expressing heterologous lactate dehydrogenase (LDH) genes, while attenuating several key pathway genes, including glycerol-3-phosphate dehydrogenase1 (GPD1) and cytochrome-c oxidoreductase2 (CYB2). In order to increase the yield of lactic acid further, the ethanol production pathway was attenuated by disrupting the pyruvate decarboxylase1 (PDC1) and alcohol dehydrogenase1 (ADH1) genes. Despite an increase in lactic acid yield, severe reduction of the growth rate and glucose consumption rate owing to the absence of ADH1 caused a considerable decrease in the overall productivity. In Δadh1 cells, the levels of acetyl-CoA, a key precursor for biologically applicable components, could be insufficient for normal cell growth. To increase the cellular supply of acetyl-CoA, we introduced bacterial acetylating acetaldehyde dehydrogenase (A-ALD) enzyme (EC 1.2.1.10) genes into the lactic acid-producing S. cerevisiae. Escherichia coli-derived A-ALD genes, mhpF and eutE, were expressed and effectively complemented the attenuated acetaldehyde dehydrogenase (ALD)/acetyl-CoA synthetase (ACS) pathway in the yeast. The engineered strain, possessing a heterologous acetyl-CoA synthetic pathway, showed an increased glucose consumption rate and higher productivity of lactic acid fermentation. The production of lactic acid was reached at 142g/L with production yield of 0.89g/g and productivity of 3.55gL(-1)h(-1) under fed-batch fermentation in bioreactor. This study demonstrates a novel approach that improves productivity of lactic acid by metabolic engineering of the acetyl-CoA biosynthetic pathway in yeast.

Improvement of glucose uptake rate and production of target chemicals by overexpressing hexose transporters and transcriptional activator Gcr1 in Saccharomyces cerevisiae.

Metabolic engineering to increase the glucose uptake rate might be beneficial to improve microbial production of various fuels and chemicals. In this study, we enhanced the glucose uptake rate in Saccharomyces cerevisiae by overexpressing hexose transporters (HXTs). Among the 5 tested HXTs (Hxt1, Hxt2, Hxt3, Hxt4, and Hxt7), overexpression of high-affinity transporter Hxt7 was the most effective in increasing the glucose uptake rate, followed by moderate-affinity transporters Hxt2 and Hxt4. Deletion of STD1 and MTH1, encoding corepressors of HXT genes, exerted differential effects on the glucose uptake rate, depending on the culture conditions. In addition, improved cell growth and glucose uptake rates could be achieved by overexpression of GCR1, which led to increased transcription levels of HXT1 and ribosomal protein genes. All genetic modifications enhancing the glucose uptake rate also increased the ethanol production rate in wild-type S. cerevisiae. Furthermore, the growth-promoting effect of GCR1 overexpression was successfully applied to lactic acid production in an engineered lactic acid-producing strain, resulting in a significant improvement of productivity and titers of lactic acid production under acidic fermentation conditions.

Binding of the chaperone Jac1 protein and cysteine desulfurase Nfs1 to the iron-sulfur cluster scaffold Isu protein is mutually exclusive.

Biogenesis of mitochondrial iron-sulfur (Fe/S) cluster proteins requires the interaction of multiple proteins with the highly conserved 14-kDa scaffold protein Isu, on which clusters are built prior to their transfer to recipient proteins. For example, the assembly process requires the cysteine desulfurase Nfs1, which serves as the sulfur donor for cluster assembly. The transfer process requires Jac1, a J-protein Hsp70 cochaperone. We recently identified three residues on the surface of Jac1 that form a hydrophobic patch critical for interaction with Isu. The results of molecular modeling of the Isu1-Jac1 interaction, which was guided by these experimental data and structural/biophysical information available for bacterial homologs, predicted the importance of three hydrophobic residues forming a patch on the surface of Isu1 for interaction with Jac1. Using Isu variants having alterations in residues that form the hydrophobic patch on the surface of Isu, this prediction was experimentally validated by in vitro binding assays. In addition, Nfs1 was found to require the same hydrophobic residues of Isu for binding, as does Jac1, suggesting that Jac1 and Nfs1 binding is mutually exclusive. In support of this conclusion, Jac1 and Nfs1 compete for binding to Isu. Evolutionary analysis revealed that residues involved in these interactions are conserved and that they are critical residues for the biogenesis of Fe/S cluster protein in vivo. We propose that competition between Jac1 and Nfs1 for Isu binding plays an important role in transitioning the Fe/S cluster biogenesis machinery from the cluster assembly step to the Hsp70-mediated transfer of the Fe/S cluster to recipient proteins.

Cysteine desulfurase Nfs1 and Pim1 protease control levels of Isu, the Fe-S cluster biogenesis scaffold.

Fe-S clusters are critical prosthetic groups for proteins involved in various critical biological processes. Before being transferred to recipient apo-proteins, Fe-S clusters are assembled on the highly conserved scaffold protein Isu, the abundance of which is regulated posttranslationally on disruption of the cluster biogenesis system. Here we report that Isu is degraded by the Lon-type AAA+ ATPase protease of the mitochondrial matrix, Pim1. Nfs1, the cysteine desulfurase responsible for providing sulfur for cluster formation, is required for the increased Isu stability occurring after disruption of cluster formation on or transfer from Isu. Physical interaction between the Isu and Nfs1 proteins, not the enzymatic activity of Nfs1, is the important factor in increased stability. Analysis of several conditions revealed that high Isu levels can be advantageous or disadvantageous, depending on the physiological condition. During the stationary phase, elevated Isu levels were advantageous, resulting in prolonged chronological lifespan. On the other hand, under iron-limiting conditions, high Isu levels were deleterious. Compared with cells expressing normal levels of Isu, such cells grew poorly and exhibited reduced activity of the heme-containing enzyme ferric reductase. Our results suggest that modulation of the degradation of Isu by the Pim1 protease is a regulatory mechanism serving to rapidly help balance the cell's need for critical iron-requiring processes under changing environmental conditions.

Posttranslational regulation of the scaffold for Fe-S cluster biogenesis, Isu.

Isu, the scaffold protein on which Fe-S clusters are built in the mitochondrial matrix, plays a central role in the biogenesis of Fe-S cluster proteins. We report that the reduction in the activity of several components of the cluster biogenesis system, including the specialized Hsp70 Ssq1, causes a 15-20-fold up-regulation of Isu. This up-regulation results from changes at both the transcriptional and posttranslational level: an increase in ISU mRNA levels and in stability of ISU protein. Its biological importance is demonstrated by the fact that cells lacking Ssq1 grow poorly when Isu levels are prevented from rising above those found in wild-type cells. Of the biogenesis factors tested, Nfs1, the sulfur donor, was unique. Little increase in Isu levels occurred when Nfs1 was depleted. However, its presence was required for the up-regulation caused by reduction in activity of other components. Our results are consistent with the existence of a mechanism to increase the stability of Isu, and thus its level, that is dependent on the presence of the cysteine desulfurase Nfs1.

Thiol-independent action of mitochondrial thioredoxin to support the urea cycle of arginine biosynthesis in Schizosaccharomyces pombe.

Thioredoxins usually perform a role as a thiol-disulfide oxidoreductase using their active-site cysteines. The fission yeast Schizosaccharomyces pombe contains two thioredoxins: Trx1 for general stress protection and Trx2 for mitochondrial functions. The Deltatrx2 mutant grows as well as the wild type on complex media containing glucose. However, on nonfermentable carbon source such as glycerol, the mutant did not grow, indicating a defect in mitochondrial function. The mutant also exhibited auxotrophy for arginine and cysteine on minimal medium. In order to find the reason for the unexpected arginine auxotrophy, we searched for multicopy suppressors and found that the arg3(+) gene encoding ornithine carbamoyltransferase (OCTase) in the urea cycle of the arginine biosynthetic pathway rescued the arginine auxotrophy. The levels of arg3(+) transcript, Arg3 protein, and OCTase activity were all decreased in Deltatrx2. Through immunocoprecipitation, we observed a direct interaction between Trx2 and Arg3 in cell extracts. The mutant forms of Trx2 lacking either one or both of the active site cysteines through substitution to serines also rescued the arginine auxotrophy and restored the decreased OCTase activity. They also rescued the growth defect of Deltatrx2 on glycerol medium. This contrasts with the thiol-dependent action of overproduced Trx2 in complementing glutathione reductase. Therefore, Trx2 serves multiple functions in mitochondria, protecting mitochondrial components against thiol-oxidative damage as a thiol-disulfide oxidoreductase, and supporting urea cycle and respiration in mitochondria in a manner independent of active site thiols.

The role and regulation of Trxl, a cytosolic thioredoxin in Schizosaccharomyces pombe.

The genome of fission yeast Schizosaccharomyces pombe harbors two genes for thioredoxins, trx1(+) and trx2(+), which encode cytosolic and mitochondrial thioredoxins, respectively. The Deltatrx1 mutant was found sensitive to diverse external stressors such as various oxidants, heat, and salt, whereas Deltatrx2 mutant was not sensitive except to paraquat, a superoxide generator. Both Deltatrx1 and Deltatrx2 mutants were more resistant to diamide, a thiol-specific oxidant, than the wild type. The trx1(+) gene expression was induced by H(2)O(2) and menadione, being mediated through a stress-responsive transcription factor Papl. In Deltatrx1 cells, the basal expression of Pap1-regulated genes were elevated, suggesting a role for Trxl as a reducer for oxidized (activated) Papl. The Deltatrx1 mutant exhibited cysteine auxotrophy, which can be overcome by adding sulfite. This suggests that Trxl serves as a primary electron donor for 3'-phosphoadenosine-5'-phosphosulfate (PAPS) reductase and thus is an essential protein for sulfur assimilation in S. pombe. These results suggest that, in contrast to Trx2 whose role is more confined to mitochondrial functions, Trxl plays a major role in protecting S. pombe against various stressful conditions and enables proper sulfur metabolism.

Gpx1 is a stationary phase-specific thioredoxin peroxidase in fission yeast.

The genome sequence of Schizosaccharomyces pombe reveals only one gene for a putative glutathione peroxidase (gpx1(+)). The Gpx1 protein has a peroxidase activity but preferred thioredoxin to glutathione as an electron donor when examined in vitro and in vivo, and therefore is a thioredoxin peroxidase. Besides H(2)O(2), it can reduce alkyl and phospholipid hydroperoxides. Expression of the gpx1 gene was elevated at the stationary phase, and we found that it supported long-term survival of S. pombe. The mutant also exhibited some defect in the activity of aconitase, an oxidation-labile Fe-S enzyme in mitochondria. Activity of sulfite reductase, a labile Fe-S enzyme in the cytosol, was also dramatically lowered in the mutant in the stationary phase. The Gpx1 protein, without any obvious targeting sequence, was localized in mitochondria as well as in the cytosol. Therefore, Gpx1 must serve to ensure optimal mitochondrial function and cytosolic environment, especially in the stationary phase.

Glutathione reductase and a mitochondrial thioredoxin play overlapping roles in maintaining iron-sulfur enzymes in fission yeast.

In the fission yeast Schizosaccharomyces pombe, the pgr1+ gene encoding glutathione (GSH) reductase (GR) is essentially required for cell survival. Depletion of GR caused proliferation arrest at the G1 phase of the cell cycle under aerobic conditions. Multicopy suppressors that restore growth were screened, and one effective suppressor was found to be the trx2+ gene, encoding a mitochondrial thioredoxin. This suggests that GR is critically required for some mitochondrial function(s). We found that GR resides in both cytosolic and organellar fractions of the cell. Depletion of GR lowered the respiration rate and the activity of oxidation-labile Fe-S enzymes such as mitochondrial aconitase and cytosolic sulfite reductase. Trx2 did not reverse the high ratio of oxidized glutathione to GSH or the low respiration rate observed in GR-depleted cells. However, it brought the activity of oxidation-labile Fe-S enzymes to a normal level, suggesting that the maintenance of Fe-S enzymes is a critical factor in the survival of S. pombe. The activity of succinate dehydrogenase, an oxidation-insensitive Fe-S enzyme, however, was not affected by GR depletion, suggesting that GR is not required for the biogenesis of the Fe-S cluster. The total iron content was greatly increased by GR depletion and was brought to a nearly normal level by Trx2. These results indicate that the essentiality of GR in the aerobic growth of S. pombe is derived from its role in maintaining oxidation-labile Fe-S enzymes and iron homeostasis.

Controlling substrate concentration in fed-batch candida magnoliae culture increases mannitol production.

Candida magnoliae HH-01, a yeast strain that is currently used for the industrial production of mannitol, has the highest mannitol production ever reported for a mannitol-producing microorganism. However, when the fructose concentration exceeds 150 g/L, the volumetric mannitol production rate decreases because of a lag in mannitol production, and the yield decreases as a result of the formation of side products. In fed-batch culture, the volumetric production rate and mannitol yield from fructose vary substantially with the fructose concentration and are maximal at a controlled fructose concentration of 50 g/L. In continuous feeding experiments, the maximum mannitol yield was 85% (g/g) at a glucose/fructose feeding ratio of 1/20. A high glucose concentration in the production phase resulted in the formation of ethanol followed by a decrease in yield and productivity. NAD(P)H-dependent mannitol dehydrogenase was purified to homogeneity from C. magnoliae. In vitro, mannitol dehydrogenase was inhibited by increasing ethanol concentration. Mannitol product was also found to be inhibitory with a K(i) of 183 mM. Under optimum conditions, a final mannitol production of 213 g/L was obtained from 250 g fructose/L after 110 h.