High Temperature Requirement Research Articles

Friction Reduction and Antiwear Mechanisms of Cerium Sulfide Nanosheets under Different Sliding Conditions.

With the rapid development of modern industry, traditional lubricants often require a variety of additives to be used in conjunction with each other, which not only increases the cost but also causes a waste of resources. Therefore, the development of a lubricant additive with both a dyeing function and an antiwear and friction reduction performance can more effectively meet the industrial needs. Cerium sulfide (Ce2S3), with its excellent photostability, weather resistance, thermal stability, and nontoxicity, shows great potential as an environmentally friendly pigment. However, traditional methods for synthesizing Ce2S3 are typically hindered by high-temperature requirements and potential toxicity issues, which limits the broad application of Ce2S3 in lubricants. To overcome these limitations, this study employed a liquid-phase method under mild conditions to synthesize oleylamine-modified, wrinkle-free Ce2S3 nanosheets (OA-Ce2S3 NSs). The antiwear and friction-reducing properties of OA-Ce2S3 NSs in poly alpha-olefin-6 base oils were evaluated under various friction conditions with a four-ball tribometer. Experimental results indicate that OA-Ce2S3 NSs significantly enhance the friction-reducing and antiwear performance of lubricants by forming a physical adsorption film and an ultra thick tribochemical reaction film (with a typical thickness of 350 nm and a maximum thickness of up to 700 nm) on the friction surface. Furthermore, the study elucidates the lubrication mechanism of OA-Ce2S3 NSs and proposes their sliding mechanism on friction surfaces. This research highlights the potential of Ce2S3 nanosheets as lubricant additives and provides future directions for optimizing their synthesis and multifunctional applications, offering new insights into the field of lubrication science.

State-of-the-art advances in homogeneous molecular catalysis for the Guerbet upgrading of bio-ethanol to fuel-grade bio-butanol.

The upgrading of ethanol to n-butanol marks a major breakthrough in the field of biofuel technology, offering the advantages of compatibility with existing infrastructure while simultaneously offering potential benefits in terms of transport efficiency and energy density. With its lower vapour pressure and reduced corrosiveness compared to ethanol, n-butanol is easier not only to manage but also to transport, eliminating the need for costly infrastructure changes. This leads to improved fuel efficiency and reduced fuel consumption. These features position n-butanol as a promising alternative to ethanol in the future of biodiesel. This review article delves into the cutting-edge advancements in upgrading ethanol to butanol, highlighting the critical importance of this transformation in enhancing the value and practical application of biofuels. While traditional methods for making butanol rely heavily on fossil fuels, those that employ ethanol as a starting material are dominated by heterogeneous catalysis, which is limited by the requirement of high temperatures and a lack of selectivity. Homogeneous catalysts have been pivotal in enhancing the efficiency and selectivity of this conversion, owing to their unique mode of operation at the molecular level. A comprehensive review of the various homogeneous catalytic processes employed in the transformation of feedstock-agnostic bio-ethanol to fuel-grade bio-n-butanol is provided here, with a major focus on the key advancements in catalyst design, reaction conditions and mechanisms that have significantly improved the efficiency and selectivity of these Guerbet reactions.

Preparation of superhydrophobic, high-temperature resistant fluorine-free silica-based powder and coatings and their applications in various environments

Superhydrophobic materials still face the challenge of resisting oxidation at high temperature. Herein, submicron powder with high-temperature resistance and superhydrophobicity was synthesized by hydrolysis of octamethylcyclotetrasiloxane (D4). The powder thin layer can reach a water contact angle (WCA) of 157° and withstand high temperature up to 500°C. Its superhydrophobicity could persist for more than 50 h at 400°C. Meanwhile, the powder and polydimethylsiloxane (PDMS) were mixed and applied to the coating to prepare high-temperature resistant superhydrophobic composite coatings. The effects of different powder incorporation ratios on coating properties were investigated. The composite coatings exhibit excellent self-cleaning ability, mechanical robustness, thermal stability, UV resistance, chemical corrosion resistance, boiling water resistance and delayed icing performance. When the ratio of powder to PDMS in the coating is 0.7:1, the high-temperature resistance performance is optimal. It can withstand temperature up to 450°C. The coating at -18°C could delay the freezing time of water droplets from 341 s to 650 s. The power and composite coatings have great advantages and application potential in fields with hydrophobicity and high-temperature resistance requirements.

Surface and Defect Modulation via Flame Technique for Efficient Photoelectrochemical Water-Splitting

The conversion of solar energy into chemical fuel via photoelectrochemical (PEC) water splitting shows great promise for solving the energy crisis, achieving carbon neutrality, and a sustainable future. Iron (Fe)-based materials have attracted tremendous attention from various light absorber materials due to their earth abundance, high light absorption, and robust PEC stability under harsh conditions[1]. However, diverse shortcomings, such as the short hole diffusion length, severe bulk/interface recombination, and sluggish water oxidation kinetics, limit the photocurrent generation for achieving high solar-to-hydrogen efficiency[2,3]. In particular, the high-temperature annealing requirement necessitates suitable synthesis and activation strategies to awaken their PEC activity.In this talk, we present a novel high-temperature flame technique to activate two Fe-based model photoanodes, i.e., zinc ferrite (ZnFe2O4, ZFO) and hematite (Fe2O3). The flame-activated ZFO (just a few tens of seconds) exhibits an enhanced charge collection ability and enriched active sites compared to the non-activated ZFO. These improvements are attributed to the high-temperature induced grain growth, enhanced grain connection, and rich defect formation caused by the fuel-rich flame environment[4]. On the other hand, a unique textured and mesoporous hematite (tm-hematite) photoanode can be synthesized via the same flame technique combining solution chemistry. The resultant tm-hematite exhibited enlarged surface area, enhanced charge transport, and transfer properties. We show that the unique mesoporous morphology, dominated (110) plane, and rich Ti dopant concentration on grain surface are responsible for the enhanced PEC activity. Notably, the tm-hematite showed greatly enhanced photocurrent density (3.1 mA/cm2 at 1.23 V vs the reversible hydrogen electrode, RHE) compared to the conventional nanorod hematite (~1.4 mA/cm2 at 1.23 VRHE) under 1 sun illumination. The flame-activated ferrite photoanodes demonstrated excellent PEC stability for 50 hours, even without additional coating/treatments. Our flame technique shows extraordinary potential for synthesizing high-efficiency ferrite-based photoelectrodes and puts a step forward to achieving the goal of sustainable energy and environment future. Keywords: Photoelectrochemical water splitting, Ferrites, Flame treatment, defect control, mesoporous structure, charge collection, photocurrent density, stability References [1] R. Tan, A. Sivanantham, B. J. Rani, Y. J. Jeong, I. S. Cho, Coord. Chem. Rev. 2023, 494, 215362.[2] I. S. Cho, M. Logar, C. H. Lee, L. Cai, F. B. Prinz, X. Zheng, Nano Lett. 2014, 14, 24.[3] I. S. Cho, H. S. Han, M. Logar, J. Park, X. Zheng, Adv. Energy Mater. 2016, 6, 1501840.[4] R. Tan, Y. J. Jeong, Q. Li, M. Kang, I. S. Cho, J. Adv. Ceram. 2023, 12(3): 612-624. Figure 1

Near-fully dense nanocrystalline hafnium via pressureless two-step sintering

Grain refinement in hafnium (Hf), a typical refractory metal, encounters significant challenges due to its inherent high sintering temperature requirements and uneven sintered capillary force that lead to rapid grain coarsening and inhomogeneity. Herein, we present a novel approach of the pressureless two-step sintering to prepare near-fully dense nanocrystalline Hf with an average grain size of around 40 nm, which represents the smallest grain and highest density for nanocrystalline pure Hf to the date. Such achievements not only broaden the applicability of pressureless two-step sintering but also offer insights to produce large size of finer-grained refractory metals and their alloys.

Bimetallic Rex-Ru/C catalyst for fatty acid esters to diesel-range alkanes under low temperature

ABSTRACT The hydrogenation of bio-based oil into biodiesel is a key strategy in reducing reliance on fossil fuels. However, efficient catalysts are needed to enable low-temperature hydrogenation reactions due to the current high-temperature requirement for bio-based oil hydrogenation. Here, bimetallic catalysts Rex-Ru/C for low-temperature hydrogenation of bio-based oils were prepared. The presence of Re oxides (ReOx) in the catalyst enhances the abundance of weak and medium acid sites, thereby facilitating the adsorption of H2. The DFT calculation shows the introduction of Re also improved the adsorption capacity of the catalyst for fatty acid methyl ester and H2. The Re0.25-Ru/C catalyst exhibits superior conversion, selectivity, and recyclability at low temperatures compared to the previously reported catalysts, achieving 100% conversion of methyl stearate with 100% selectivity toward n-heptadecane (C17) and n-octadecane (C18) (reaction conditions: 150°C, 4 h, 2.5 MPa H2). Moreover, the catalyst also shows excellent hydrogenation activity toward various fatty acids or esters, including methyl palmitate, stearic acid, and palmitate at low temperatures. The Re0.25-Ru/C catalyst showed consistent recycling performance over 9 cycles. The decline in catalytic performance of the catalyst was primarily caused by a reduction in ReOx content, resulting in a decrease in acid site concentration. Consequently, there was reduced adsorption of H2 and oil on the catalyst.

Plasma-Assisted Synthesis of Methanol Through Hydrogenation of Carbon Dioxide With Non-Noble Metal Mixed Oxide Catalysts.

The utilization of carbon dioxide through chemical conversion is a promising approach for the recycling of carbon resources. Despite well-developed industrial processes for CO2 hydrogenation to methanol, the effective use of CO2 as a feedstock remains challenging because of the costly requirements of high temperature and reaction pressure. In this paper, we report the methanol synthesis from CO2 and hydrogen using a dielectric barrier discharge (DBD) reactor under atmospheric pressure with a nickel-cerium-aluminum mixed oxide (Ni/Ce-Al MOx) catalyst. The combined use of plasma and the Ni/Ce-Al MOx catalyst was observed to yield 13.3±0.4 % of methanol, favorably compared to the 2.6±0.5 % yield of the case without catalyst. Microscopy images, selected area electron diffraction patterns, and energy-dispersive X-ray analysis confirmed the presence of fluorite-structured ceria, aluminium, nickel, and nickel oxide particles in the catalyst. The reaction mechanism for the plasma-assisted hydrogenation of CO2 was hypothesized to involve a carbide formation pathway due to the presence of carbide confirmed by X-ray photoelectron spectroscopic characterization.

Ultrasonic-assisted radial jet reattachment atomizer

Ultrasonic atomization, a powerful method using high-frequency sound waves, has gained notable significance across diverse industries due to its capacity to disintegrate liquids into very fine droplets. The use of ultrasonic vibrations for spray formation can effectively address the challenges associated with conventional methods, including the requirement for high temperatures and high-pressure fluids. Compared to conventional methods, ultrasonic atomizers can deliver a spray with lower velocity, operate at lower temperatures, produce smaller particle sizes, achieve high evaporation rates, and impose low mechanical stress. The radial jet reattachment (RJR) nozzle is a unique design to modify a jet’s flow and improve its transport characteristics, especially in air drying and cooling processes. In this paper, a novel technology is utilized with the combination of an RJR nozzle and ultrasonic atomization to atomize most liquids. The corresponding atomization rate, mist droplet size distribution, and mist droplet velocity distribution, influenced by liquid properties, temperature change, transducer mesh pore size, and applied voltage have been investigated in this paper. The energy consumption ratios, defined as the ratio of thermal energy required to evaporate liquid divided by ultrasonic energy, are analyzed based on atomization rate and applied power, showing very promising results among atomizing methods. Furthermore, the results in terms of the droplet average diameter and mean velocity as well as the resultant volumetric flow rate under different operating conditions and for all working fluids considered have been correlated with the aid of non-dimensional parameters. In addition, certain potential applications based on the remarkable characteristics of the ultrasonic-assisted RJR atomizer such as misting liquids and spray drying are highlighted.

Comparative analysis of canine and human HtrA2 to delineate its role in apoptosis and cancer.

Therapeutically, targeting the pro- and anti-apoptotic proteins has been one of the major approaches behind devising strategies to combat associated diseases. Human high-temperature requirement serine protease A2 (hHtrA2), which induces apoptosis through both caspase-dependent and independent pathways is implicated in several diseases including cancer, ischemic heart diseases, and neurodegeneration, thus making it a promising target molecule. In the recent past, the canine model has gained prominence in the understanding of human pathophysiology that was otherwise limited to the rodent system. Moreover, canine models in cancer research provide an opportunity to study spontaneous tumors as their size, lifespan, and environmental exposure are significantly closer to that of humans compared with laboratory rodents. Therefore, using HtrA2 as a model protein, comparative analysis has been done to revisit the hypothesis that canines might be excellent models for cancer research. We have performed evolutionary phylogenetic analyses that confirm a close relationship between canine and human HtrA2s. Molecular modeling demonstrates structural similarities including orientation of the catalytic triad residues, followed by in silico docking and molecular dynamics simulation studies that identify the potential interacting partners for canine HtrA2 (cHtrA2). In vitro biophysical and protease studies depict similarities in interaction with their respective substrates as well as transient transfection of cHtrA2 in mammalian cell culture shows induction of apoptosis. This work, therefore, promises to open a new avenue in cancer research through the study of spontaneous cancer model systems in canines.

The effect of long-term adherence to physical activity recommendations in midlife on plasma proteins associated with frailty in the Atherosclerosis Risk in Communities (ARIC) study.

Clinical trials have shown favorable effects of exercise on frailty, supporting physical activity (PA) as a treatment and prevention strategy. Proteomics studies suggest that PA alters levels of many proteins, some of which may function as molecules in the biological processes underlying frailty. However, these studies have focused on structured exercise programs or cross-sectional PA-protein associations. Therefore, the effects of long-term PA on frailty-associated proteins remain unknown. Among 14,898 middle-aged adults, we emulated a target trial that assigned individuals to either (i) achieve and maintain the recommended PA level (≥150 minutes/week of moderate-to-vigorous physical activity [MVPA]) through 6 (±0.3) years of follow-up or (ii) follow a "natural course" strategy, where all individuals engage in various amounts of habitual MVPA. We estimated the effects of long-term adherence to recommended MVPA versus the natural course strategy on 45 previously identified frailty-associated proteins (log 2 transformed and standardized) at the end of the follow-up using inverse probability of weighting (IPW) and iterative conditional expectations (ICE). We found that long-term adherence to recommended MVPA improved the population levels of many frailty-associated proteins (ranged from 0.04 to 0.11 standard deviation); the greatest benefits were seen in proteins involved in the nervous system (e.g., voltage-dependent calcium channel subunit alpha-2/delta-3 [CACNA2D3], contactin-1 [CNTN1], neural cell adhesion molecule 1 [NCAM1], and transmembrane protein 132D [TMEM132D]) and inflammation (e.g., high-temperature requirement serine protease A1 [HTRA1] and C-reactive protein [CRP]). Our findings suggest long-term engagement in adequate habitual PA may reduce frailty risk through specific nervous systems and inflammatory proteins.

Reusable metal-free mesoporous carbon-catalyzed reductive N-formylation of nitroarenes and quinolines

The high-value transformation of nitrogen-containing compounds through a facile, cost-effective, and eco-friendly one-pot strategy holds significant importance. However, this process typically involves the use of metal catalysts and is limited by low activity as well as the requirement of high temperature and pressure. Herein, we describe a general and efficient metal-free N-doped mesoporous carbon material using well-defined ligand 1,10-phenanthroline as the precursor and silica colloid as the hard template. Formic acid is both a reducing agent and a formylation reagent, and structurally distinct mono- or multi-substituted nitroarenes and quinolines can be selectively N-formylation in a one-pot method. The catalyst can be easily recovered without observable loss of efficiency for ten consecutive uses. The control experiments and density functional theory (DFT) calculations indicate that formic acid mainly obtains active hydrogen in the form of O–H bond cleavage, which benefits from the strong adsorption and enhanced activity generated by the interaction between graphitic nitrogen species in the catalyst and formic acid. The excellent catalytic performance of the meso-phen-X catalyst is attributed to the synergistic effect of graphitic N and large specific surface area, providing a promising method for the development of non-metallic catalyst-modified carbon materials.

Association of polymorphisms in the HTRA1 gene with myopia

PurposeTo evaluate the associations of single-nucleotide polymorphisms (SNPs) in the high-temperature requirement protease A 1 (HTRA1) gene with myopia.Methods25 SNPs in HTRA1 were selected, including 23 haplotype-tagging SNPs, SNP rs2142308...

Sandwich-structured polymer dielectrics exhibiting significantly improved capacitive performance at high temperatures by roll-to-roll physical vapor deposition

Electrostatic capacitors with ultrahigh power density are the key components in modern electrical and electronic systems. Polymers are preferred dielectrics for high-voltage electrostatic capacitors, however, unable to meet the ever-growing high-temperature requirements in emerging applications, such as electric vehicles, and photovoltaic power generation. In this work, sandwich-structured Polyphenylene sulfide (PPS) films with Al2O3 as the coating layer have been prepared by using roll-to-roll magnetron sputtering. The incorporation of Al2O3 coating layers enhances the potential barrier height at the electrode/dielectric interface, thereby impeding charge injection from electrodes and suppressing high-temperature electrical conduction. Consequently, the sandwich-structured PPS films demonstrate significantly improved breakdown strengths and enhanced capacitive performance at elevated temperatures compared to neat PPS films. The roll-to-roll magnetron sputtering process employed in fabricating these sandwich-structured dielectric films is highly compatible with large-scale capacitor film production. Thus, sandwich-structured PPS films hold promise in addressing the challenge of scalable fabrication of high-performance, high-quality polymer films required for high-temperature capacitive energy storage.

An Association between HTRA1 and TGF-β2 in the Vitreous Humor of Patients with Chorioretinal Vascular Diseases.

Background: The aim of this paper was to investigate the protein concentrations of high-temperature requirement A 1 (HTRA1) and transforming growth factor-β (TGF-β) in the vitreous humor of patients with chorioretinal vascular diseases. Methods: This study measured protein concentrations of HTRA1, TGF-β1-3, and vascular endothelial growth factor A (hereinafter called VEGF) in the vitreous humor from seven eyes of patients with chorioretinal vascular diseases (age-related macular degeneration, diabetic macular edema, and retinal vein occlusion) and six control eyes (idiopathic epiretinal membrane and macular hole). We analyzed the mutual relationship among the protein levels. Results: The protein levels of HTRA1 and VEGF were significantly increased in the chorioretinal vascular disease group compared with the control group (1.57 ± 0.79 ×10-9 mol/mL vs. 0.68 ± 0.79 ×10-9 mol/mL, p = 0.039; 3447.00 ± 3423.47 pg/mL vs. 35.33 ± 79.01 pg/mL, p = 0.046, respectively). TGF-β2 levels were not significantly different between groups (2222.71 ± 1151.25 pg/mL for the chorioretinal vascular disease group vs. 1918.83 ± 744.01 pg/mL for the control group, p = 0.62). The concentration of HTRA1 was strongly associated with TGF-β2 levels in the vitreous humor, independent of VEGF (r = 0.80, p = 0.0010). Conclusions: We revealed that vitreous HTRA1 was increased in patients with chorioretinal vascular diseases and strongly correlated with TGF-β2.

Rutile (In0.5Ta0.5)0.1Ti0.87O1.88F0.12 ceramics with excellent dielectric performance and thermal stability sintered at 1220 °C

TiO2-based colossal dielectric ceramics have emerged as a prominent research focus in recent years. However, their further applications have been constrained by several key limitations, including the requirement of high sintering temperature (>1400 °C), relatively high dielectric loss (>0.05, 1 kHz), and temperature stability (<200 °C). This study reports rutile (In0.5Ta0.5)0.1Ti0.87O1.88F0.12 ceramics at 1220 °C sintering using 12 % InF3 as the acceptor In3+ source, which exhibits a colossal dielectric constant (1.1 × 105) and an ultra-low dielectric loss (0.0071) at 1 kHz and room temperature, even loss values below 0.04 (20 Hz - 100 kHz). Notably, the thermal stabilities (10 kHz, 100 kHz) simultaneously satisfy X9E (Δεr/ε25 °C ≤ ±4.7 %) above 300 °C. F− not only supplies electrons to enhance the semiconductivity of grains, but also decreases the oxygen vacancy and average grain size (270 ± 12.53 nm) to improve grain boundaries resistances, which reduces dielectric loss and enhances frequency and temperature stabilities. As a result, the dielectric mechanism is mainly related to internal barrier layer capacitor (IBLC) and high grain boundary resistance. Therefore, this strategy provides a creative design for developing TiO2-based ceramics.

Trimetallic-doped carbon nitride achieves chondroitin sulfate degradation via a free radical degradation strategy

Traditional Fenton principles for degrading polysaccharides, including chondroitin sulfate (CS), are fraught with limitations, such as strict pH-dependence, higher temperature requirements, desulfurization, and environmentally perilous. In this study, an effective Fenton-like system comprising trimetallic-doped carbon nitride material (tri-CN) with hydrogen-bonded melamine-cyanuric acid (MCA) supramolecular aggregates as its basic skeleton was engineered to overcome the challenges of traditional methods. Detailed material characterizations revealed that, compared to monometallic-doped or bimetallic-doped counterparts, tri-CN offered a larger surface area, higher porosity, and increased metal loading, thereby enhancing reactant accessibility and polysaccharide degradation efficiency. The characterization and activity assessment of the degraded polysaccharide revealed structurally intact products without significant desulfurization, indicating the effectiveness of the designed approach. Moreover, the degraded chondroitin sulfate CS3 catalyzed by tri-CN, exhibited promising antioxidant activity and anti-CRISPR potential. The results elucidated that the high-valent iron species in the material served as primary active sites, catalyzing the cleavage of hydrogen peroxide to generate hydroxyl radicals that subsequently attacked CS chains, leading to their fragmentation. Hence, the designed material can be efficiently applied to polysaccharide degradation, but not limited to photocatalysis, electrocatalysis, sensor, energy storage materials, and wastewater treatment.

Comparative study of microwave-assisted and hydrothermal hydroxyapatite synthesis from neutralization slag: Optimization, energy, and adsorption

The study proposes the utilization of microwave-assisted methods for converting neutralization slag (NS) into hydroxyapatite (HAP), offering an alternative to the conventional hydrothermal method. The microwave-assisted approach addresses the challenges encountered in hydrothermal reactions, such as particle agglomeration, reduced specific surface area, prolonged reaction time, high temperature requirements, and inadequate saturation adsorption capacity. By employing the response surface methodology with a Box-Behnken design, the study found that the microwave-assisted method significantly reduced the synthesis time from 90 to 25 min and the temperature from 120 °C to 56 °C. Furthermore, the microwave method consumed only 1/43 of the energy utilized in hydrothermal synthesis. To assess the performance of the synthesized HAP, various detection methods were utilized, including XRD, SEM-EDS, FTIR, Zeta potential, and ICP, which analyzed the crystal structure, crystallinity, morphology, chemical composition, and surface charge of HAP. The BET method was used to measure the specific surface area, further confirming the successful synthesis of HAP. The HAP synthesized through this microwave-assisted method exhibited a saturation adsorption capacity of up to 98.4 mg/g of fluoride ions from vanadium industrial raffinate. This study demonstrates that the microwave-assisted method provides a viable solution for reducing energy consumption and enhancing HAP synthesis efficiency for wastewater treatment in the vanadium industry.

The HtrA chaperone monitors sortase-assembled pilus biogenesis in Enterococcus faecalis.

Sortase-assembled pili contribute to virulence in many Gram-positive bacteria. In Enterococcus faecalis, the endocarditis and biofilm-associated pilus (Ebp) is polymerized on the membrane by sortase C (SrtC) and attached to the cell wall by sortase A (SrtA). In the absence of SrtA, polymerized pili remain anchored to the membrane (i.e. off-pathway). Here we show that the high temperature requirement A (HtrA) bifunctional chaperone/protease of E. faecalis is a quality control system that clears aberrant off-pathway pili from the cell membrane. In the absence of HtrA and SrtA, accumulation of membrane-bound pili leads to cell envelope stress and partially induces the regulon of the ceftriaxone resistance-associated CroRS two-component system, which in turn causes hyper-piliation and cell morphology alterations. Inactivation of croR in the OG1RF ΔsrtAΔhtrA background partially restores the observed defects of the ΔsrtAΔhtrA strain, supporting a role for CroRS in the response to membrane perturbations. Moreover, absence of SrtA and HtrA decreases basal resistance of E. faecalis against cephalosporins and daptomycin. The link between HtrA, pilus biogenesis and the CroRS two-component system provides new insights into the E. faecalis response to endogenous membrane perturbations.

Proteolytic activity of surface-exposed HtrA determines its expression level and is needed to survive acidic conditions in Clostridioides difficile.

To survive in the host, pathogenic bacteria need to be able to react to the unfavorable conditions that they encounter, like low pH, elevated temperatures, antimicrobial peptides and many more. These conditions may lead to unfolding of envelope proteins and this may be lethal. One of the mechanisms through which bacteria are able to survive these conditions is through the protease/foldase activity of the high temperature requirement A (HtrA) protein. The gut pathogen Clostridioides difficile encodes one HtrA homolog that is predicted to contain a membrane anchor and a single PDZ domain. The function of HtrA in C. difficile is hitherto unknown but previous work has shown that an insertional mutant of htrA displayed elevated toxin levels, less sporulation and decreased binding to target cells. Here, we show that HtrA is membrane associated and localized on the surface of C. difficile and characterize the requirements for proteolytic activity of recombinant soluble HtrA. In addition, we show that the level of HtrA in the bacteria heavily depends on its proteolytic activity. Finally, we show that proteolytic activity of HtrA is required for survival under acidic conditions.

Nano Photo Bleaching Method of Cotton Fabrics for a Sustainable Finishing

In modern textile-bleaching methods, H2O2 is commonly preferred due to its less harmful effects on the environment. The use of hydrogen peroxide in bleaching processes, although biodegradable on its own, increases the waste load due to the high amount of auxiliary chemicals used. The long processing times and high-temperature requirements of hydrogen peroxide bleaching led to increased energy consumption. Moreover, the high-water consumption required for post-treatment is also a disadvantageous factor. In other words, while the use of a high amount of auxiliary chemicals in hydrogen peroxide bleaching increases the waste load, long time and high-temperature requirements also increase energy consumption, and the high-water consumption required for post-treatment has a disadvantageous effect. In this study, raw cotton fabric is subjected to chemical finishing treatments that either oxidize or reduce it as part of the bleaching process. The results of photo bleaching were compared with conventional hydrogen peroxide finishing applications. Our findings showed that nano-TiO2-treated cotton had a better whiteness value than treated with H2O2 cotton according to the color spectrum whiteness indexes. It is strongly considered that this method could be a new alternative way for bleaching textile materials in the finishing departments.