Synthesis and characterization of core-shell high-nickel cobalt-free layered LiNi0.95Mg0.02Al0.03O2@Li2ZrO3 cathode for high-performance lithium ion batteries.

High-nickel cobalt-free layered cathode is regarded as a highly potential cathode material for the next generation lithium ion batteries (LIBs) because of its high energy density, low cost and environmentally benign. However, the poor cycle performance caused by its intrinsic unstable structure and chemo-mechanical instability frustrates its practical applications. Herein, we have developed a new core-shell high-nickel cobalt-free layered LiNi0.95Mg0.02Al0.03O2@Li2ZrO3 (LZO-NMA9523) cathode for high-performance LIBs. The Li2ZrO3 coating layer firstly helps to suppress and reduce the degree of Li+/Ni2+ cation mixing during the material preparation process. In addition, the Li2ZrO3 coating layer can not only accommodate the volume variations and enhance the electricity of the active materials, but also effectively inhibit the harmful irreversible phase transition during the charging/discharging process, thus greatly stabilizing the structure of the high-nickel cobalt-free cathode. As an advanced cathode for LIBs, the LZO-NMA9523 exhibits an excellent reversible capacity of 146.9 mAh g-1 after 100 cycles at 0.5 C with capacity retention of about 80%. This study provides a possible high-nickel cobalt-free layered cathode material for the next generation LIBs.

Thermal Study of Carbon-Fiber-Reinforced Polymer Composites Using Multiscale Modeling.

The layered fibers of carbon-fiber-reinforced polymer (CFRP) composites exhibit low thermal conductivity (TC) throughout their thickness due to the poor TC of the polymeric resin. Improved heat transmission inside the hydrogen storage tank during the filling process can reduce further compression work, and improved heat insulation can minimize energy loss. Therefore, it is crucial to understand the thermal properties of composites. This paper reports the thermal behavior of plain-woven CFRP composite using simulation at the micro-, meso-, and macro-scales. The TC was predicted numerically and compared to experimental findings and analytical models. Good results were found. Using the approach of multi-scale modeling, a parametric study was carried out to analyze in depth the influence of certain variables on thermal properties. The study revealed that both fiber volume fraction and temperature significantly influenced the TC of the composite, with the interphase fiber/matrix thickness following closely in terms of impact. The matrix porosity was found to have a relatively slighter impact, particularly within the porosity range of 5 to 15%.

Evolutionary Progress of Silica Aerogels and Their Classification Based on Composition: An Overview.

Aerogels are highly porous materials with fascinating properties prepared using sol-gel chemistry. Due to their unique physical and chemical properties, aerogels are recognized as potential candidates for diverse applications, including thermal insulation, sensor, environmental remediation, etc. Despite these applications, aerogels are not routinely found in our daily life because they are fragile and have highly limited scale-up productions. It remains extremely challenging to improve the mechanical properties of aerogels without adversely affecting their other properties. To boost the practical applications, it is necessary to develop efficient, low-cost methods to produce aerogels in a sustainable way. This comprehensive review surveys the progress in the development of aerogels and their classification based on the chemical composition of the network. Recent achievements in organic, inorganic, and hybrid materials and their outstanding physical properties are discussed. The major focus of this review lies in approaches that allow tailoring of aerogel properties to meet application-driven requirements. We begin with a brief discussion of the fundamental issues in silica aerogels and then proceed to provide an overview of the synthesis of organic and hybrid aerogels from various precursors. Organic aerogels show promising results with excellent mechanical strength, but there are still several issues that need further exploration. Finally, growing points and perspectives of the aerogel field are summarized.

Fossil and non-fossil sources of the carbonaceous component of PM2.5 in forest and urban areas.

Atmospheric particulate matter (PM2.5) can damage human health. Biogenic organic compounds emitted from trees may increase the concentration of PM2.5 via formation of secondary aerosols. Therefore, the role of biogenic emissions in PM2.5 formation and the sources of PM2.5 need to be investigated. Dual carbon isotope and levoglucosan analyses are powerful tools to track the sources of total carbon (TC) in PM2.5. We collected a total of 47 PM2.5 samples from 2019 to 2020 inside a pine forest and in urban areas in South Korea. The average δ13C and Δ14C of TC in PM2.5 at the Taehwa Research Forest (TRF) were - 25.7 and - 380.7‰, respectively, which were not significantly different from those collected at Seoul National University (SNU) in urban areas. Contribution of fossil fuel, C3-, and C4- plants to carbonaceous component of PM2.5 were 52, 27, and 21% at SNU, whereas those were 46, 35, and 19% at TRF, respectively. The biomass burning tracer, levoglucosan, was most abundant in winter and correlated with the contribution of C4 plants derived carbon. Results indicate that biogenic aerosols emitted from trees is less likely to be an important source of PM2.5 and that trees can act as a bio-filter to reduce PM2.5.

Properties of river organic carbon affected by wastewater treatment plants.

Tracking the sources of organic carbon (OC) is critical not only for understanding riverine carbon dynamics but also for providing management options to improve water quality. We collected water samples from upland forest streams to the mainstream Geumho River (GHR) of South Korea, which included a variety of wastewater treatment plants (WWTP) effluents. We analyzed the concentrations, optical properties, and dual carbon isotope ratios of these samples to identify the sources of OC. Dissolved organic carbon (DOC) was the dominant form of OC in the GHR compared to particulate organic carbon (POC), as the former accounted for 87 % of OC. The concentrations of DOC and POC ranged from 1.2 to 11.2 mg L-1 and from 0 and 3.6 mg L-1, respectively, aside from the livestock WWTP effluent. Dominant fluorescence components were terrestrial humic substances in upper reaches whereas protein-like materials in lower reaches of the GHR whose watershed includes a large city with many WWTPs. Significantly lower Δ14C-DOC and Δ14C-POC were observed in industrial WWTP effluents than the other sites due to the contribution of fossil OC. Livestock WWTP effluents had higher δ13C-DOC and δ13C-POC than most of the sites, possibly due to the animal feed derived from C4 plants such as corn. Fossil OC contributed 29-52 % of [DOC] and 36-56 % of [POC] from industrial WWTP effluents, whereas C4-plants derived OC contributed about half of [DOC] and [POC] from a livestock WWTP effluent. The results suggest that anthropogenic sources of organic carbon could alter river carbon dynamics, and that caution is needed when we interpret isotope ratios of riverine organic carbon, particularly when the river passes through highly populated areas wherein WWTP effluents are large.

Green synthesis of multifunctional ZnO/chitosan nanocomposite film using wild Mentha pulegium extract for packaging applications.

Following the global corona virus pandemic and environmental contamination caused by chemical plastic packaging, awareness of the need for environmentally friendly biofilms and antibacterial coatings is increasing. In this study, a biodegradable hybrid film, comprising of green-synthesized zinc oxide nanoparticles (ZnO NPs) with a chitosan (CS) matrix, was fabricated using a simple casting procedure. The ZnO NPs were synthesized using wild Mentha pulegium extract, and the synthesized NPs and films were characterized using different approaches. The structural, morphological, mechanical, antibacterial, and optical properties, as well as the hydrophilicity, of the prepared samples were investigated using various techniques. Gas chromatography-mass spectrometry measurements revealed the presence of phenolic compounds in the M. pulegium extract. In addition, a strong coordination connection between Zn2+ and the chitosan matrix was confirmed, which resulted in a good dispersion of ZnO in the chitosan film. The surface of the composite films was transparent, smooth, and uniform, and the flexible bio-based hybrid films exhibited significant antibacterial and antioxidant characteristics, strong visible emission in the 480 nm region, and UV-blocking properties. The ZnO/CS films displayed a potential to extend the shelf life of fruits by up to eight days when stored at 23°C, and also acted as an acceptable barrier against oxygen and water. The biodegradable ZnO/CS film is expected to keep fruit fresher than general chemical plastic films and be used for the packaging of active ingredients.

Crystal structures of human NSDHL and development of its novel inhibitor with the potential to suppress EGFR activity.

NAD(P)-dependent steroid dehydrogenase-like (NSDHL), an essential enzyme in human cholesterol synthesis and a regulator of epidermal growth factor receptor (EGFR) trafficking pathways, has attracted interest as a therapeutic target due to its crucial relevance to cholesterol-related diseases and carcinomas. However, the development of pharmacological agents for targeting NSDHL has been hindered by the absence of the atomic details of NSDHL. In this study, we reported two X-ray crystal structures of human NSDHL, which revealed a detailed description of the coenzyme-binding site and the unique conformational change upon the binding of a coenzyme. A structure-based virtual screening and biochemical evaluation were performed and identified a novel inhibitor for NSDHL harboring suppressive activity towards EGFR. In EGFR-driven human cancer cells, treatment with the potent NSDHL inhibitor enhanced the antitumor effect of an EGFR kinase inhibitor. Overall, these findings could serve as good platforms for the development of therapeutic agents against NSDHL-related diseases.

Structural and functional study of SaAcP, an acylphosphatase from Staphylococcus aureus.

Acylphosphatase is the smallest enzyme that is widely distributed in many diverse organisms ranging from archaebacteria to higher-eukaryotes including the humans. The enzyme hydrolyzes the carboxyl-phosphate bonds of the acyl phosphates which are important intermediates in glycolysis, membrane pumps, tricarboxylic acid cycle, and urea biosynthesis. Despite its biological importance in critical cellular functions, very limited structural investigations have been conducted on bacterial acylphosphatases. Here, we first unveiled the crystal structure of SaAcP, an acylphosphatase from gram-positive S. aureus at the atomic level. Structural insights on the active site together with mutation study provided greater understanding of the catalytic mechanism of SaAcP as a bacterial acylphosphatase and as a putative apyrase. Furthermore, through NMR titration experiment of SaAcP in its solution state, the dynamics and the alterations of residues affected by the phosphate ion were validated. Our findings elucidate the structure-function relationship of acylphosphatases in gram-positive bacteria and will provide a valuable basis for researchers in the field related to bacterial acylphosphatases.

A structural study of TatD from Staphylococcus aureus elucidates a putative DNA-binding mode of a Mg2+-dependent nuclease.

TatD has been thoroughly investigated as a DNA-repair enzyme and an apoptotic nuclease, and still-unknown TatD-related DNases are considered to play crucial cellular roles. However, studies of TatD from Gram-positive bacteria have been hindered by an absence of atomic detail and the resulting inability to determine function from structure. In this study, an X-ray crystal structure of SAV0491, which is the TatD enzyme from the Gram-positive bacterium Staphylococcus aureus (SaTatD), is reported at a high resolution of 1.85 Šwith a detailed atomic description. Although SaTatD has the common TIM-barrel fold shared by most TatD-related homologs, and PDB entry 2gzx shares 100% sequence identity with SAV0491, the crystal structure of SaTatD revealed a unique binding mode of two phosphates interacting with two Ni2+ ions. Through a functional study, it was verified that SaTatD has Mg2+-dependent nuclease activity as a DNase and an RNase. In addition, structural comparison with TatD homologs and the identification of key residues contributing to the binding mode of Ni2+ ions and phosphates allowed mutational studies to be performed that revealed the catalytic mechanism of SaTatD. Among the key residues composing the active site, the acidic residues Glu92 and Glu202 had a critical impact on catalysis by SaTatD. Furthermore, based on the binding mode of the two phosphates and structural insights, a putative DNA-binding mode of SaTatD was proposed using in silico docking. Overall, these findings may serve as a good basis for understanding the relationship between the structure and function of TatD proteins from Gram-positive bacteria and may provide critical insights into the DNA-binding mode of SaTatD.

The thermoelectric properties of Au nanoparticle-incorporated Al-doped mesoporous ZnO thin films.

Mesoporous Al-doped ZnO thin films incorporated with gold nanoparticles (Au NPs) were synthesized using a sol-gel and evaporation-induced self-assembly process. In this study, the complementary effects of Au NP incorporation and Al doping on the thermoelectric properties of mesoporous ZnO thin films were analysed. The incorporated Au NPs induced an increase in electrical conductivity but a detriment in the pore arrangement of the mesoporous ZnO thin film, which was accompanied by a decrease in porosity. However, the addition of the Al dopant minimized the pore structural collapse because of the inhibition of the grain growth in the ZnO skeletal structure, resulting in the enhancement of the pore arrangement and porosity. When the Au NPs and Al dopant were added at the same time, the degradation in the pore structure was minimized and the electrical conductivity was effectively increased, but the absolute value of the Seebeck coefficient was decreased. However, as a result, the thermoelectric power factor was increased by 2.4 times compared to that of the pristine mesoporous ZnO thin film. It was found that co-introducing the Au NPs and Al doping to the mesoporous ZnO structure was effective in preserving the pore structure and increasing the electric conductivity, thereby enhancing the thermoelectric property of the mesoporous ZnO thin film.

#DeleteFacebook: Antecedents of Facebook Fatigue.

Despite the trend of leaving Facebook (#DeleteFacebook campaign), investigation on both the social and psychological factors affecting Facebook fatigue is limited. This study aims to explore the social and psychological antecedents of Facebook fatigue and identify the effects of the antecedents on overall Facebook fatigue. A total of 327 Facebook users participated in an online survey. Respondents were recruited from a major online panel in Korea. The results from the principal component analysis suggest that there are six social and psychological antecedents: impression management, unwanted posts, reputation concern, personal relative deprivation, privacy concern, and relationship concern. In addition, the results show that personal relative deprivation, privacy concern, impression management, and relationship concern positively predicted overall Facebook fatigue. This research not only sheds light on the antecedents of social networking services (SNS) fatigue that influence overall Facebook fatigue but also suggests practical implications for the everexpanding SNS market.

Synthesis and Properties of Metal Oxide Aerogels via Ambient Pressure Drying.

Metal oxide aerogels such as zirconia (ZrO2), titania (TiO2), and alumina (Al2O3) aerogels are very interesting nanoporous materials applicable as thermal insulators, catalysts, sensors, and so on. To obtain the aerogels, the first key step is a sol-gel process to prepare the gel followed by either supercritical drying, ambient pressure drying, or freeze-drying. Although the expensive and energy-intensive supercritical drying method restricts the commercialization of the aerogels, ambient pressure drying has shown great potential as an alternative and very simple method for aerogel synthesis. The sol-gel method and preparation parameters such as hydrolysis water, the silylating agent concentration, and the thermal treatment temperature have a profound impact on the textural and structural properties of the aerogels. Therefore, in this review, we study the synthesis and the influence of these parameters on the properties of metal oxide aerogels via ambient pressure drying.

Polypropylene/Silica Aerogel Composite Incorporating a Conformal Coating of Methyltrimethoxysilane-Based Aerogel.

Silica aerogels possess low thermal conductivity but have a brittle nature, while their polymers tend to exhibit enhanced mechanical properties. In this study, we introduce a new approach to overcoming this brittle property of silica aerogels. Polypropylene/silica aerogel composites were prepared by thermally induced phase separation followed by a supercritical CO2 drying method. Silica aerogel was formed onto a polypropylene scaffold using a two-step sol-gel process with methyltrimethoxysilane as the silica precursor. Enhancement of the mechanical properties of the polypropylene/silica aerogel composite compared with a pristine methyltrimethoxysilane-based silica aerogel was observed. The effects of the latter on the microstructure and physical properties of the polypropylene/silica aerogel (hereafter referred to as the polymer matrix aerogel) composite were investigated. Compared with the polypropylene monolith, the polymer matrix aerogel composite demonstrated enhanced surface-chemical and microporous-structural properties such as higher hydrophobicity (135°), pore volume (0.18 cm³/g), average pore diameter (12.55 nm), and specific surface area (57.2 m²/g). This novel approach of incorporating methyltrimethoxysilane-based silica aerogel onto polypropylene when synthesizing the polymer matrix aerogel composite shows great potential as a durable superhydrophobic and corrosion resistant thermal insulating material.

Superhydrophobic and Compressible Silica-polyHIPE Covalently Bonded Porous Networks via Emulsion Templating for Oil Spill Cleanup and Recovery.

We synthesize porous polyHIPE networks with silanol functionalities in the polyHIPE backbone. These silanol functionalities are used for covalent bonding with silica aerogels embedded in the polyHIPE. Covalent bonding between silica and polyHIPE networks are confirmed using Fourier-transform infrared spectroscopy and scanning electron microscopy. Silica aerogels covalently bonded with polyHIPE network show macroporous and mesoporous morphologies and possess excellent properties like high bendability, high elasticity, superhydrophobicity (~160°), low density (~0.128 g/cm3), and low thermal conductivity (~0.045 W/m·K). Oil absorption from water/oil mixtures and recovery of the absorbed oil (by squeezing) from flexible silica-polyHIPE networks is studied. The silica-polyHIPE is shown to absorb crude oil ~16-times its own weight and can be reused multiple times after recovery. Hence, such materials are very important for oil spill cleanup applications from aqueous systems.

Regulatory mechanisms of thiol-based redox sensors: lessons learned from structural studies on prokaryotic redox sensors.

Oxidative stresses, such as reactive oxygen species, reactive electrophilic species, reactive nitrogen species, and reactive chlorine species, can damage cellular components, leading to cellular malfunction and death. In response to oxidative stress, bacteria have evolved redox-responsive sensors that enable them to simultaneously monitor and eradicate potential oxidative stress. Specifically, redox-sensing transcription regulators react to oxidative stress by means of modifying the thiol groups of cysteine residues, functioning as part of an efficient survival mechanism for many bacteria. In general, oxidative molecules can induce changes in the three-dimensional structures of redox sensors, which, in turn, affects the transcription of specific genes in detoxification pathways and defense mechanisms. Moreover, pathogenic bacteria utilize these redox sensors for adaptation and to evade subsequent oxidative attacks from host immune defense. For this reason, the redox sensors of pathogenic bacteria are potential antibiotic targets. Understanding the regulatory mechanisms of thiol-based redox sensors in bacteria will provide insight and knowledge into the discovery of new antibiotics.

Autoinducer-2 Quorum Sensing Influences Viability of Escherichia coli O157:H7 under Osmotic and In Vitro Gastrointestinal Stress Conditions.

Bacteria use autoinducer molecules to communicate both at intra-species and inter-species levels by quorum sensing. One such cell density-dependent signaling system is the luxS-mediated universal quorum sensing using autoinducer-2 (AI-2). Virulence of several pathogens is determined by an AI-2 system and is related to colonization and infection of the host. From this concept, numerous papers have suggested that AI-2 inhibition is an important strategy toward designing of new antimicrobial agents. However, recent studies indicate that the AI-2 system is also involved in adaptation and survival under environmental stress conditions. Therefore, we hypothesized that interaction between quorum sensing and environmental conditions may be critical in influencing predicted results in a control and when combating of target pathogens. We investigated the growth of enterohemorrhagic Escherichia coli O157:H7 (EHEC) and its luxS-deficient (non AI-2 producing) mutant strain under various stress conditions, and found significant differences in the growth rate under osmotic stress. Moreover, we could also show the impact of the AI-2 molecule on viability in the gastrointestinal tract model representing a complex environmental condition. Differences in vital responses of the strains suggest that AI-2 quorum sensing has a significant influence on the viability of EHEC under environmental stress conditions.

Fermented Moringa oleifera Decreases Hepatic Adiposity and Ameliorates Glucose Intolerance in High-Fat Diet-Induced Obese Mice.

Metabolic diseases, such as glucose intolerance and nonalcoholic fatty-liver disease (NAFLD), are primary risk factors for life-threatening conditions such as diabetes, heart attack, stroke, and hepatic cancer. Extracts from the tropical tree Moringa oleifera show antidiabetic, antioxidant, anti-inflammatory, and anticancer effects. Fermentation can further improve the safety and nutritional value of certain foods. We investigated the efficacy of fermented M. oleifera extract (FM) against high-fat diet (HFD)-induced glucose intolerance and hepatic lipid accumulation and investigated the underlying mechanisms by analyzing expression of proteins and genes involved in glucose and lipid regulation. C57BL/6 mice were fed with normal chow diet (ND) or HFD supplemented with distilled water (DW, control), nonfermented M. oleifera extract (NFM), or FM for 10 weeks. Although body weights were similar among HFD-fed treatment groups, liver weight was decreased, and glucose tolerance test (GTT) results improved in the FM group compared with DW and NFM groups. Hepatic lipid accumulation was also lower in the FM group, and expressions of genes involved in liver lipid metabolism were upregulated. In addition, HFD-induced endoplasmic reticulum (ER) stress, oxidative stress, and lipotoxicity in quadriceps muscles were decreased by FM. Finally, proinflammatory cytokine mRNA expression was decreased by FM in the liver, epididymal adipose tissue, and quadriceps of HFD-fed mice. FMs may decrease glucose intolerance and NAFLD under HFD-induced obesity by decreasing ER stress, oxidative stress, and inflammation.

Autoinducer-2 properties of kimchi are associated with lactic acid bacteria involved in its fermentation.

Bacteria use the cell density-dependent quorum signalling system to regulate particular gene expressions. In food microbiology, signalling is well known for its relation to (foodborne) pathogenicity, food spoilage, and biofilm formation. Quorum quenching and inhibition are thus being considered as a feasible approach in food preservation and safety. In the case of the luxS-mediated universal quorum sensing using autoinducer-2 (AI-2), however, it could be a different issue. Several studies have reported a luxS AI-2 synthase homologue in numerous bacteria, comprising both pathogens and beneficial strains. A recent study has shown the AI-2 signal to restore the balance of the major phyla of the gut microbiota in antibiotic-induced dysbiosis. We measured the AI-2 activity of the lactic fermented food, kimchi, and found different AI-2 signalling intensities. In order to trace the origin of the signal production, we obtained 229 lactic acid bacterial isolates from the kimchi samples, and detected the AI-2 properties of each isolate using a modified AI-2 bioluminescence assay. Our results showed isolates of dominant species of the genera Lactobacillus, Weissella and Leuconostoc which either produced or inhibited the AI-2 signal. No isolate of the dominant species Lactobacillus sakei (75 isolates) and Lactobacillus curvatus (28 isolates) showed AI-2 producing activity, while AI-2 inhibition could not be detected for any of the 31 Lactobacillus plantarum isolates. These results suggest the AI-2 activity of kimchi to result from the interaction of the associated microbial food cultures (MFCs) during fermentation. Thus far, only sparse information is available on AI-2 signalling interaction in fermented food, however, we suggest that fermented food may be a supplier of AI-2 signalling molecules via typical MFCs.

Structure-based functional identification of Helicobacter pylori HP0268 as a nuclease with both DNA nicking and RNase activities.

HP0268 is a conserved, uncharacterized protein from Helicobacter pylori. Here, we determined the solution structure of HP0268 using three-dimensional nuclear magnetic resonance (NMR) spectroscopy, revealing that this protein is structurally most similar to a small MutS-related (SMR) domain that exhibits nicking endonuclease activity. We also demonstrated for the first time that HP0268 is a nicking endonuclease and a purine-specific ribonuclease through gel electrophoresis and fluorescence spectroscopy. The nuclease activities for DNA and RNA were maximally increased by Mn(2+) and Mg(2+) ions, respectively, and decreased by Cu(2+) ions. Using NMR chemical shift perturbations, the metal and nucleotide binding sites of HP0268 were determined to be spatially divided but close to each other. The lysine residues (Lys7, Lys11 and Lys43) are clustered and form the nucleotide binding site. Moreover, site-directed mutagenesis was used to define the catalytic active site of HP0268, revealing that this site contains two acidic residues, Asp50 and Glu54, in the metal binding site. The nucleotide binding and active sites are not conserved in the structural homologues of HP0268. This study will contribute to improving our understanding of the structure and functionality of a wide spectrum of nucleases.

Crystal structure of YwpF from Staphylococcus aureus reveals its architecture comprised of a ß-barrel core domain resembling type VI secretion system proteins and a two-helix pair.

The ywpF gene (SAV2097) of the Staphylococcus aureus strain Mu50 encodes the YwpF protein, which may play a role in antibiotic resistance. Here, we report the first crystal structure of the YwpF superfamily from S. aureus at 2.5-Å resolution. The YwpF structure consists of two regions: an N-terminal core ß-barrel domain that shows structural similarity to type VI secretion system (T6SS) proteins (e.g., Hcp1, Hcp3, and EvpC) and a C-terminal two-helix pair. Although the monomer structure of S. aureus YwpF resembles those of T6SS proteins, the dimer/tetramer model of S. aureus YwpF is distinct from the functionally important hexameric ring of T6SS proteins. We therefore suggest that the S. aureus YwpF may have a different function compared to T6SS proteins.