High Resistance Research Articles

Sulphuric precipitates in novel titanium-based, sulphur-bearing bulk metallic glass – a BMG composite?

ABSTRACT New titanium-based metallic glasses containing sulphur as a key element have recently been developed and are the subject of ongoing research related to the effects of sulphur introduction into glass-forming alloy systems. Here we report on the formation of sulphuric precipitates during solidification of a Ti40Zr35Cu17S8 alloy and on the occurrence of secondary intermetallic compound crystallization starting in sulphur-depleted zones around the precipitates. The alloy is a promising metallic glass for use as a structural and biomedical material as it shows a high yield strength and good corrosion resistance paired with a low density. The role of sulphur for the glass formation in the Ti-Zr-Cu-S system is discussed and specimens quenched into different structural states are investigated by means of high-energy synchrotron diffraction and electron microscopy. The electron microscopic findings reveal that sulphuric precipitates precede the crystallization of an intermetallic (Ti, Zr)2Cu phase, which is the primary phase when sulphur is not present in the system and thus lead to a higher glass-forming ability. The sulphuric precipitates are found in specimens of various casting thickness and differ in their volume percentages depending on the size of the cast sample, while the secondary phase (Ti, Zr)2Cu crystallizes heterogeneously in the interfaces between the sulphuric precipitates and the local matrix.

The Effectiveness of Three Different Irrigant Activation Methods in the Elimination of Enterococcus faecalis from Root Canals.

Background and Objective: Eliminating intracanal Enterococcus faecalis (E. faecalis) is challenging because of its ability to penetrate deep dentinal tubules and its high resistance to many chemicals. This study evaluated the effectiveness of conventional needle irrigation and three different irrigant activation methods in reducing E. faecalis. Methods: The root canals of extracted teeth were shaped, contaminated with E. faecalis, and incubated for three weeks. They were randomly allocated to four experimental groups of 15 teeth each according to the final irrigation method: group 1, conventional needle irrigation; group 2, passive ultrasonic (PU) irrigation; group 3, XP-endo Finisher (XPF); and group 4, laser-activated (LA) irrigation. Bacterial samples were taken and cultured before and after these final irrigation procedures. The colony-forming units were counted, and the bacterial reduction percentages of each group were calculated. The Kruskal-Wallis and Dunnet tests were used for statistical analysis. Results: All irrigant activation methods were significantly more effective than conventional needle irrigation. Although the LA group generated more negative samples than PU, there was no statistically significant difference between the LA and PU groups. LA was significantly more effective than the XPF, whereas PU and XPF were statistically similar. Conclusions: Within the limitations of this study, the final irrigation with LA and PU showed the best reductive effect on E. faecalis colonies. Considering that the LA group had more negative samples, it may be chosen as an alternative to enhance root canal disinfection, especially in difficult cases.

Possibilities of decontaminating organic waste from swine-farming complexes using anaerobic digestion

AbstractAnaerobic digestion with simultaneous production of biogas is one of the most common methods of recycling, processing and decontamination of organic waste to produce alternative fuels. A commonly used indicator of the sanitary safety of the substrate is eggs of Ascaris suum nematodes of pigs, which are characterised by extremely high resistance to environmental factors. The aim is to investigate the effect of the mesophilic mode of anaerobic digestion on the activity of pathogens, particularly Ascaris suum eggs. The eggs of the studied nematode species were placed in a biogas installation at a temperature of 37 °C. The digestate samples with eggs were then taken every 4 days for 28 days, followed by larvae culture to determine the viability of the eggs. The results of our research have shown that the mesophilic regime of anaerobic digestion is an effective method of controlling parasites, but at the same time, it needs to be improved, since only 7.6% of A. suum eggs remained alive after a 1-day stay, about 50% after the week stay and about 9% in the third week stay in the biogas reactor. Thus, further optimisation of anaerobic fermentation in the mesophilic mode can be aimed at improving the suppression of pathogenic activity.

ANTIMICROBIAL RESISTANCE PATTERNS AMONG BACTERIAL PATHOGENS ISOLATED FROM CLINICAL SAMPLES IN SANA'A HOSPITALS

Background and objectives: Yemen is among the developing nations where antimicrobial resistance (AMR) is posing a danger to public health. AMR can lead to increased morbidity and mortality from treatment failures and a lack of effective therapies. Particularly in the research arena, there is a dearth of knowledge about the antimicrobial resistance patterns of frequently isolated, locally occurring diseases. Therefore, the purpose of this study was to evaluate the diseases' microbiological profiles and resistance trends in Sana'a, Yemen. Methods: In Sana'a, Yemen, a retrospective study was carried out at various governmental and private hospitals between June and September of 2020. Information about antibiotic susceptibilities and cultures was taken from the microbiology department's 2019 files. The data analysis method employed was descriptive statistics. Results: This study includes 4156 pathogen isolates, with 58.2% of the isolates being Gram negative. Of all the isolates, urine (26.1 %, n = 1086) and pus specimens (24.6 %, n = 1025) demonstrated the greatest detection rates. The most often isolated pathogens were S. aureus (35.6%, n=1479), E. coli (29.2%, n=1215), P. aeroginosa (14.1%, n=586), and Klebsiella species (10.7%, n=443). The highest rates of resistance were found for cephalosporins (cefixime 90%, cefadroxil 87.9%, cefepime 72%, and ceftriaxone 70%) and penicillins (carbincillin 87%, amoxacillin 80%, and amoxacillin/clavulanic acid 77%). Gram positive and Gram negative isolates showed minimal resistance to linezolid and vancomycin, with Enterococcus showing higher resistance. Colistin was most effective against Gram negative, while E. coli, Klebseilla, and Proteus showed high resistance. Conclusions: The high rate of resistance discovered in the current study in both Gram-positive and Gram-negative organisms is alarming and highlights the necessity of routinely determining the prevalence of resistance in a given area in order to guide empirical therapy and choose the most effective course of antibiotic treatment. Peer Review History: Received 27 March 2024; Revised 8 May 2024; Accepted 27 June; Available online 15 July 2024 Academic Editor: Prof. Dr. Gorkem Dulger, Duzce University, Turkey, gorkemdulger@yandex.com Average Peer review marks at initial stage: 6.5/10 Average Peer review marks at publication stage: 7.0/10 Reviewers: Dr. Heba M. Abd El-Azim, Damanhour University, Egypt, h_m_abdelazim@hotmail.com Dr. Jennifer Audu-Peter, University of Jos, Nigeria, drambia44@gmail.com

Antimicrobial resistance pattern of Klebsiella species isolated from various clinical specimens

Objective: The present study was carried out to identify Klebsiella species and their antimicrobial resistance pattern from various clinical specimens. Methods: This cross study was conducted at a tertiary care hospital, Dhaka, Bangladesh from July2020 to June 2021. Written consent was taken from the concerned authority. A total 6739 clinical samples including urine, wound swab/ pus, sputum, blood and endotracheal aspirates were collected and processed for isolation of bacteria by following standard guidelines from adult patients. All the urine, wound swab, blood and endotracheal aspirates were inoculated in both blood agar and MacConkey agar media, for blood samples blood culture was done in BacT/ALERT 3D 60 aerobic bottles irrespective to antibiotics administration. After incubation at 370C aerobically for 24 hours incubated plates were examined. Phenotypic identification of the organisms were done by observing colony morphology, hemolytic properties, pigment production, Gram staining and biochemical tests (oxidase test, catalase test and biochemical reactions after inoculation in TSI, MIU, citrate agar media). The Kirby - Bauer disk diffusion method was used for antimicrobial susceptibility testing of the isolated organism using Mueller-Hinton agar and commercially available antibiotic discs (Oxoid Ltd, UK). The data were analyzed using SPSS software Version-20 (SPSS Inc., Chicago, IL, USA). Categorical variables were expressed as numbers (n) and percentages (%). Results: A total 6739 samples were included in the present study. Of which, 170 were urine, 162 were wound swabs, 71 were sputum, 52 were endotracheal aspirates and 45 were blood samples. Culture positivity among the samples is shown in table I. Conclusion: Most of the Klebsiella species are highly resistant to commonly used antibiotics. This higher resistance is the major cause morbidity and mortality related with infections in hospitalized patients. So, a regular surveillance of antibiotic susceptibility pattern is needed to prevent indiscriminate use of antibiotics. CME J 2024; 3(2); 12-15

Salmonella spp. in Domestic Ruminants, Evaluation of Antimicrobial Resistance Based on the One Health Approach-A Systematic Review and Meta-Analysis.

Salmonella spp. pose a global threat as a leading cause of foodborne illnesses, particularly prevalent in the European Union (EU), where it remains the second cause of foodborne outbreaks. The emergence of antimicrobial resistance (AMR) in Salmonella spp. has become a critical concern, complicating treatment strategies and escalating the risk of severe infections. The study focuses on large and small ruminants, identifying a prevalence of Salmonella spp. in slaughterhouses and revealing varied AMR rates across antimicrobial families throughout a meta-analysis. Also, comparison with AMR in human medicine was carried out by a systematic review. The results of the present meta-analysis displayed a prevalence of Salmonella spp. in large and small ruminants at slaughterhouses of 8.01% (8.31%, cattle; 7.04%, goats; 6.12%, sheep). According to the AMR of Salmonella spp., 20, 14, and 13 out of 62 antimicrobials studied were classified as low (<5%), high (>5% but <10%), and very high (>10%), respectively. Salmonella spp. did not display AMR against aztreonam, mezlocillin, ertapenem, meropenem, cefoxitin, ceftazidime, levofloxacin, tilmicosin, linezolid, fosfomycin, furazolidone, quinupristin, trimethoprim and spectinomycin. In contrast, a prevalence of 100% of AMR has been described against ofloxacin, lincomycin, and cloxacillin. In the context of the main antibiotics used in the treatment of human salmonellosis, azithromycin was shown to have the highest resistance among Salmonella spp. isolates from humans. Regarding cephalosporins, which are also used for the treatment of salmonellosis in humans, the prevalence of Salmonella spp. resistance to this class of antibiotics was similar in both human and animal samples. Concerning quinolones, despite a heightened resistance profile in Salmonella spp. isolates from ruminant samples, there appears to be no discernible compromise to the efficacy of salmonellosis treatment in humans since lower prevalences of AMR in Salmonella spp. isolated from human specimens were observed. Although the resistance of Salmonella spp. indicates some degree of concern, most antibiotics are not used in veterinary medicine. Thus, the contribution of cattle, sheep and goats to the rise of antibiotic resistance of Salmonella spp. and its potential impact on public health appears to be relatively insignificant, due to their low prevalence in carcasses and organs. Nevertheless, the observed low prevalence of Salmonella spp. in ruminants at slaughterhouse and the correspondingly low AMR rates of Salmonella spp. to key antibiotics employed in human medicine do not indicate that ruminant livestock poses a substantial public health risk concerning the transmission of AMR. Thus, the results observed in both the meta-analysis and systematic review suggests that AMR is not solely attributed to veterinary antibiotic use but is also influenced by factors such as animal health management (i.e., biosecurity measures, prophylactic schemes) and human medicine.

Unique Aspects of Scaffolding Design for the Urgent Seismic Retrofitting of Zagreb Cathedral

The 2020 Zagreb earthquake caused extensive damage to historically significant buildings, including the Cathedral of the Assumption of Mary, a key monument of Croatian cultural heritage. The earthquake rendered the cathedral unsafe due to significant damage to its towers and numerous cracks in its vaults and walls. Urgent measures were necessary to ensure safety and facilitate planned reconstruction and strengthening efforts. A specialised scaffolding design was developed to support inaccessible and unstable areas, involving over 1000 tonnes of steel. This paper details the structural concepts and specific scaffolding design implemented for the urgent restoration and seismic retrofitting of Zagreb Cathedral, ensuring it meets high earthquake resistance requirements.

Flexible ionic liquid aided “LAGP in PVDF” quasi-solid-state electrolyte for high performance and stable Li metal batteries

The NASICON-type ceramic Li1·5Al0.5Ge1.5(PO4)3 (LAGP) electrolyte has been proposed as the most competitive candidates of electrolyte materials toward solid-state Li metal batteries (LMBs) by reason of its high ionic conductivity, cyclic stability under extreme temperatures and wide voltage window. However, poor interface contact, high interfacial resistance and intractable mechanical properties greatly limit its practical applications. In this work, an inorganic-polymer “LAGP in PVDF” quasi-solid-state electrolyte (QSSE) is developed via solution casting method, in which pyr14TFSI ionic liquid (IL) and LiTFSI are combined as functional wetting interface. Benefiting from the coherent interaction of LAGP nanoparticles incorporated into the polymer matrix, and inherent protection of IL, the overall performance of the optimized QSSE include thermal stability, dense structure, flexibility and electrochemical properties. The XRD, SEM, XPS tests demonstrate that the IL using as a solid/electrolyte modified interlayer can enhance Li+ transport, interfacial infiltration and homogenize lithium deposition. The LiFePO4|PL-25LAGP|Li solid-state battery presents an excellent circulation performance under ambient temperature, which displayed an initial discharge specific capacity of 146.8 mAh g−1 at 0.5C and capacity retention of 96.25 % after 150 cycles. The flexibility PL-LAGP CSE shows superior safety and greater development potential for the “LAGP in PVDF” composite electrolyte in solid state LMBs.

Improvement in inhibition performance of anti-corrosion coatings using polyolefin matrix embedded with modified TiO2 nanoparticles

Corrosion remains a critical issue for steel structures, leading to costly repairs and potential failures in industrial sectors. This study presents the development and characterization of polyolefin coatings for enhanced corrosion protection. Initially, the porous TiO2 nanoparticles were synthesized using the sol-gel method, followed by their modification through the encapsulation of sodium benzoate (SB) as a corrosion inhibitor. Modified Polyolefin coatings were prepared by incorporating modified nanoparticles (TiO2 loaded with sodium benzoate) into the polyolefin matrix, and an unmodified/blank polyolefin coating was prepared without any additive in the polyolefin matrix. The loading of the inhibitor into porous TiO2 was 10 % analyzed using thermogravimetric analysis. Furthermore, the electrochemical analysis revealed significant improvements in the corrosion resistance and barrier properties of the modified coatings compared to the unmodified blank coatings. Specifically, after 7 days in a corrosive environment, the blank coating pore resistance dropped from 1 × 1010 Ω·cm2 to 5 × 108 Ω·cm2, while the modified coating maintained a high pore resistance of 5 × 1011 Ω·cm2. A localized corrosion study for scratched blank polyolefin coatings showed growing corrosion activity from 5 h of immersion, while modified coatings ceased the detectable activity before 4 h of immersion, which evidenced the improved corrosion inhibition efficiency of the modified coating. This stability in corrosive environments was attributed to the successful loading of modified nanoparticles (TiO2/SB), where SB served as an active agent by forming a protective film on the steel substrate. Which inhibits the corrosion processes along with Ti-based compounds and prevents corrosion propagation under the damaged coating. The enhanced hydrophobic nature of 99° and electrochemical properties support the suitability of these coatings for corrosion protection of steel in various industries.

Layered Bismuth Selenide with a Kinetics‐Enhanced Iodine Doping Strategy Toward High‐Performance Aqueous Potassium‐Ion Storage

AbstractAqueous potassium‐ion batteries with inherent safety, high abundance, and competitive hydrated ion‐radius point to future availability in energy storage. However, the extensively studied electrodes (metal‐oxides, Prussian‐blue‐analogues, etc.) typically suffer from undesirable capacities and sluggish kinetics owing to overwhelming ion diffusion barriers. Herein, for the first time, the metal chalcogenide bismuth selenide reinforced by iodine‐doping (I‐Bi2Se3) is implemented for high‐performance aqueous potassium‐ion storage. The co‐intercalation mechanism of potassium‐ion with proton in I‐Bi2Se3 is entirely revealed by operando synchrotron X‐ray diffraction and substantial ex‐situ analysis, and the excellent interlayer diffusion kinetics in the high‐conductive host are further enhanced by iodine‐doping, as proposed by theoretic calculations. Therefore, the resulting high diffusion coefficient and low interfacial transfer resistance endow I‐Bi2Se3 with superior rate performance (109.2 mAh g−1 at 10 A g−1) and cycling stability (91% capacity retention after 1200 cycles). Employing in hybrid‐ion batteries matching zinc metal, the highest reversible aqueous potassium‐ion storage to date of 316.8 mAh g−1 is demonstrated, permitting the establishment of reliable performance pouch cells. The promising aqueous potassium intercalation chemistry built in the improved metal chalcogenide is proven to be extendable to other hybrid‐ion devices, offering novel mechanistic insights and material practices for aqueous energy storage.

Investigating the effect of zirconium dioxide micro and nano particles on the mechanical characteristics of Al-7075 alloy

ABSTRACT The study investigates the influence of zirconium dioxide (ZrO2) particles on the mechanical properties of Al7075 alloy and aims to assess the potential for tailored compositions to meet specific engineering requirements, particularly in aerospace applications. Al7075-ZrO2 composite was fabricated with varying percentages of micro (µ) ZrO2 (1%, 2%, and 3%) and nano ZrO2 (0.17%, 0.34%, and 0.51%) particles using the stir casting technique. Mechanical testing was conducted to evaluate the peak stress, load, and yield strength of the resulting Al7075-ZrO2 composites. Experimental findings reveal that the highest peak stress and load were achieved at 0.51% nano ZrO2 content, indicating a reinforcement effect. Moreover, the composite with 0.34% nano ZrO2 exhibited 59% increased peak stress of 153 MPa and 24% decreased strain 3.7% compared 125 MPa and 4.9% for pure Al7075. Al7075-µZrO2 composite has shown 125 MPa of peak stress and 2.9% maximum strain. These properties highlight the potential of Al7075-ZrO2 composite for applications requiring high resistance to tensile failure. Incorporating nano ZrO2 particles positively impact the load-bearing capacity and strength of Al7075 alloy matrix. Specifically, compositions with tailored ZrO2 content percentages demonstrate the potential for meeting the stringent requirements of aerospace applications.

History of apple breeding and breeding achievements at FSBSO ARHCBAN

New apple varieties should possess a set of adaptive traits that provide yield, stable fruiting, and highly marketable fruits with a long period of postharvest storage, thus ensuring the profitability of their use in industrial plantings. According to the State Register, the central region of the Russian Federation is one of the leading regions in terms of the number of apple varieties approved for use. Long-term research of scientists and specialists from FSBSO ARHCBAN has greatly contributed to the development and improvement of the assortment both in the region and beyond. The key directions for apple breeding at the institution include improving winter hardiness, resistance to scab, and the columnar shape of the crown. The review article presents the history of shaping the directions for breeding work and modern achievements of FSBSO ARHCBAN in apple breeding, as well as an analysis of the long-term focused scientific activity of breeders. The most significant breeding results were achieved by Prof. V. Kichina, who, together with his students and followers, was the first in Russia to create several columnar apple varieties that offer high winter hardiness, resistance to scab, and marketable qualities of fruits (‘Dialog’, ‘Lukomor’, ‘Malyukha’, ‘Ostankino’, ‘President’, and ‘Chervonets’), as well as fundamentally new high-yielding varieties with a conventional crown shape that possess high adaptability and resistance to pathogens (‘Arkadik’, ‘Legendа’, ‘Marat Busurin’, and ‘Mayak Zagorye’). The article presents the main characteristics of breeding achievements of the last decades: tree crown shape; ripening time of fruits and their qualitative and quantitative indicators (tasting evaluation, average weight, shape, etc.); yield; resistance to abiotic and biotic factors. Data are presented on the use of apple varieties bred by FSBSO ARHCBAN both in agricultural production (on the basis of license agreements) and in scientific and technological cooperation with Russian National Research Universities (inclusion in breeding programs). The apple breeding activities conducted at FSBSO ARHCBAN are described, and the main directions for breeding work are outlined.

Point Mutations in Furazolidone and Rifampicin Resistance Genes in Helicobacter pylori Strains from Colombia.

The eradication of Helicobacter pylori is a valid strategy for preventing gastric cancer; however, the therapeutic failure of first-line treatments in Colombia is associated with high resistance to metronidazole and amoxicillin. This study explored alternative antibiotics and analyzed point mutations in resistance genes to furazolidone and rifampicin in order to include them in rescue therapy regimens. A total of 239 complete genomes of Helicobacter pylori Colombian strains were compared to that of the ATCC 26695 strain to identify mutations in the rpoB and porD genes for rifampicin and furazolidinone resistance, respectively. While rifampicin resistance mutations were not found, only 0.84% of the isolates showed the porD gene, suggesting that Helicobacter pylori is sensitive to these antibiotics. A phylogenomic analysis of Helicobacter pylori revealed an independent lineage in Colombia (hspColombia). The absence of point mutations in the rpoB gene, together with the scarce mutations identified in the porD gene of Helicobacter pylori, suggest that the hspColombia isolates are sensitive to rifampicin and furazolidone, which could be key to including these antibiotics in the rescue therapies against Helicobacter pylori.

A Glutathione S-Transferase from Thinopyrum ponticum Confers Fhb7 Resistance to Fusarium Head Blight in Wheat.

Fusarium head blight (FHB), mainly incited by Fusarium graminearum, has caused great losses in grain yield and quality of wheat globally. Fhb7, a major gene from 7E chromosome of Thinopyrum ponticum, confers broad resistance to multiple Fusarium species in wheat and has recently been cloned and identified as encoding a glutathione S-transferase (GST). However, some recent reports raised doubt about whether GST is the causal gene of Fhb7. To resolve the discrepancy and validate the gene function of GST in wheat, we phenotyped Fhb7 near-isogenic lines (Jimai22-Fhb7 versus Jimai22) and GST overexpressed lines for FHB resistance. Jimai22-Fhb7 showed significantly higher FHB resistance with a lower percentage of symptomatic spikelets, Fusarium-damaged kernels, and deoxynivalenol content than susceptible Jimai22 in three experiments. All the positive GST transgenic lines driven by either the maize ubiquitin promoter or its native promoter with high gene expression in the wheat cultivar 'Fielder' showed high FHB resistance. Only one maize ubiquitin promoter-driven transgenic line showed low GST expression and similar susceptibility to Fielder, suggesting that high GST expression confers Fhb7 resistance to FHB. Knockout of GST in the Jimai22-Fhb7 line using CRISPR-Cas9-based gene editing showed significantly higher FHB susceptibility compared with the nonedited control plants. Therefore, we confirmed GST as the causal gene of Fhb7 for FHB resistance. Considering its major effect on FHB resistance, pyramiding Fhb7 with other quantitative trait loci has a great potential to create highly FHB-resistant wheat cultivars.

All-natural, thermally conductive, flame-retardant electrical insulating lignocellulose-mica composite film fabricated via in-situ mineralization

Miniaturized, integrated, and functional electronic devices generate a large amount of heat accumulation during operation, which significantly affects the reliability, durability, and safety of electronic devices. In severe cases, it may even lead to fires. Therefore, the development of insulation composite materials with thermal conductivity and flame-retardant properties is particularly important. In this study, we propose an in-situ mineralization strategy to prepare insulation composite materials with thermal conductivity and flame-retardant properties. By dissolving and preparing a gel film, Al3+ and Zn2+ retained inside the lignocellulose are in situ mineralized to form Al(OH)3 and ZnO, and introducing inorganic blocks with high insulation performance (industrial waste mica tailings and synthetic mica). The prepared film has excellent tensile strength (117.4 MPa), low dielectric loss, high dielectric strength (83.8 kV mm−1), high insulation resistance, four times higher thermal conductivity than the unmineralized film, and excellent flame-retardant properties. Meanwhile, the environmental impact of the composite film is much lower than that of petrochemical-based plastic films and can easily degrade under natural conditions within 32 days. It is a composite material that meets the standards of the new electrical insulation field, and the in-situ mineralization strategy can also provide ideas for the preparation of high-performance lignocellulose-based materials.

Nonstoichiometry Induced Amorphous Grain Boundary of Na5SmSi4O12 Solid-State Electrolyte for Long-Life Dendrite-Free Sodium Metal Battery.

Oxide ceramics are considered promising candidates as solid electrolytes (SEs) for sodium metal batteries. However, the high sintering temperature induced boundaries and pores between angular grains lead to high grain boundary resistance and pathways for dendrite growth. Herein, we report a grain boundary modification strategy, which in situ generates an amorphous matrix among Na5SmSi4O12 oxide grains via tuning the chemical composition. The mechanical properties as well as electron mitigating capability of modified SE have been significantly enhanced. As a result, the SE achieves a room-temperature total ionic conductivity of 5.61 mS cm-1, the highest value for sodium-based oxide SEs. The Na|SE|Na symmetric cell achieves a high critical current density of 2.5 mA cm-2 and excellent cycle life over more than 2800 h at 0.15 mA cm-2 without dendrite formation. The full cell with Na3V2(PO4)3 as the cathode demonstrates impressive cycling performance, maintaining stability over 3000 cycles at 5C without observable loss of capacity.

Experimental study of bond behavior of geopolymer concrete under different curing condition using a pull-out test

Researchers recently have focused on geopolymer concrete as it has several advantages compared to traditional Portland cement, such as lower carbon footprint, high early strength, chemical resistance and long-lasting structural performance. This paper designed 192 pull-out specimens to investigate the influence of factors on the bond-slip behavior between geopolymer and steel bar such as curing condition (ambient and 80 °C for 7 hours), longitudinal rib angle, the position of longitudinal bar, bar diameter (12 mm and 24 mm), stirrup usage (with and without stirrup) and bond length (2d and 4d). The maximum bond strength, bond failure modes, and bond stress-slip relations were discussed. The test results showed that the longitudinal rib angle, and the position of rebar play a vital role in determining the bond strength as well as the bar diameter. In comparison with the specimens without the stirrup, the bond performance of specimens with stirrup increased more significantly, and this phenomenon became even more pronounced as the bar diameter increased. The stirrup usage in samples under ambient and heat cure increased the bond strength by an average of 45 % and %40, respectively. Moreover, it has been determined that the curing conditions have a significant effect on the bond performance, as especially the compressive and tensile strengths of the samples under heat cure improve. In samples exposed to both ambient and heat cure, doubling the bond length increased the bond strength by 70 %. Furthermore, increasing the bar diameter increased the bond strength of the samples exposed to ambient and heat curing by a maximum of 84 % and 79 %, respectively. The findings lay the groundwork for understanding the bond behavior of geopolymer, which is critical for the successful application of geopolymer-bonded rebar.

Mutations Affecting Cellular Levels of Cobalamin (Vitamin B12) Confer Tolerance to Bactericidal Antibiotics in Burkholderia cenocepacia.

The Burkholderia cepacia complex (Bcc) consists of opportunistic pathogens known to cause pneumonia in immunocompromised individuals, especially those with cystic fibrosis. Treating Bcc pneumonia is challenging due to the pathogens' high multidrug resistance. Therefore, inhalation therapy with tobramycin powder, which can achieve high antibiotic concentrations in the lungs, is a promising treatment option. In this study, we investigated potential mechanisms that could compromise the effectiveness of tobramycin therapy. By selecting for Burkholderia cenocepacia survivors against tobramycin, we identified three spontaneous mutations that disrupt a gene encoding a key enzyme in the biosynthesis of cobalamin (Vitamin B12). This disruption may affect the production of succinyl-CoA by methylmalonyl-CoA mutase, which requires adenosylcobalamin as a cofactor. The depletion of cellular succinyl-CoA may impact the tricarboxylic acid (TCA) cycle, which becomes metabolically overloaded upon exposure to tobramycin. Consequently, the mutants exhibited significantly reduced reactive oxygen species (ROS) production. Both the wild-type and mutants showed tolerance to tobramycin and various other bactericidal antibiotics under microaerobic conditions. This suggests that compromised ROS-mediated killing, due to the impacted TCA cycle, underlies the mutants' tolerance to bactericidal antibiotics. The importance of ROS-mediated killing and the potential emergence of mutants that evade it through the depletion of cobalamin (Vitamin B12) provide valuable insights for developing strategies to enhance antibiotic treatments of Bcc pneumonia.

Molecular Mechanisms of Resistance against PSII-Inhibiting Herbicides in Amaranthus retroflexus from the Czech Republic.

Amaranthus retroflexus L. (redroot pigweed) is one of the most problematic weeds in maize, sugar beet, vegetables, and soybean crop fields in Europe. Two pigweed amaranth biotypes (R1 and R2) from the Czech Republic resistant to photosystem II (PSII)-inhibiting herbicides were analyzed in this study. This study aimed to identify the genetic mechanisms that underlie the resistance observed in the biotypes. Additionally, we also intended to establish the use of chlorophyll fluorescence measurement as a rapid and reliable method for confirming herbicide resistance in this weed species. Both biotypes analyzed showed high resistance factors in a dose-response study and were thus confirmed to be resistant to PSII-inhibiting herbicides. A sequence analysis of the D1 protein revealed a well-known Ser-Gly substitution at amino acid position 264 in both biotypes. Molecular docking studies, along with the wild-type and mutant D1 protein's secondary structure analyses, revealed that the S264G mutation did not reduce herbicide affinity but instead indirectly affected the interaction between the target protein and the herbicides. The current study identified the S264G mutation as being responsible for conferring herbicide resistance in the pigweed amaranth biotypes. These findings can provide a strong basis for future studies that might use protein structure and mutation-based approaches to gain further insights into the detailed mechanisms of resistance in this weed species. In many individuals from both biotypes, resistance at a very early stage (BBCH10) of plants was demonstrated several hours after the application of the active ingredients by the chlorophyll fluorescence method. The effective PS II quantum yield parameter can be used as a rapid diagnostic tool for distinguishing between sensitive and resistant plants on an individual level. This method can be useful for identifying herbicide-resistant weed biotypes in the field, which can help farmers and weed management practitioners develop more effective weed control tactics.

Dual tobramycin and docosahexaenoic acid loaded nanoemulsions combating Pseudomonas aeruginosa-induced pulmonary infection

Pseudomonas aeruginosa (P. aeruginosa) typically forms biofilms in vivo, which exhibit high resistance and complicate eradication efforts. Additionally, persistent inflammation and excessive oxidative stress can lead to severe lung dysfunction, facilitating bacterial colonization and infection. Herein, we prepared oil-in-water (O/W) nanoemulsions (TD-αT NEs) by using PEG5k-block-PCL5k and α-tocopherol to encapsulate tobramycin (TOB). To enhance TOB’s drug load, a hydrophobic ion pair (TDIP) composed of TOB and docosahexaenoic acid (DHA) was pre-prepared. TD-αT NEs was not only easily prepared and aerosolized, but stable in both physics and chemistry. The negatively charged TD-αT NEs facilitated penetration through mucus, reaching infection sites. Subsequently, TD-αT NEs permeated biofilms due to their small size and released drugs via lipase-triggered carrier dissociation, aiding in eradicating internal bacteria within biofilms (with a 16-fold reduction in CFU vs. free TOB group). TD-αT NEs simultaneously exerted superior anti-inflammatory effects, reducing levels of pro-inflammatory cytokines (NO, IL-6, IL-8, and TNF-α) while increasing the level of anti-inflammatory cytokine (IL-10). It was achieved through the upregulation of PPAR-γ and downregulation of NF-κB signaling, thus mitigating the lung damage. In addition, TD-αT NEs demonstrated strong antioxidant activity, alleviating the oxidative stress induced by P. aeruginosa. Notably, when administered via inhalation, TD-αT NEs significantly reduced the lung bacterial burden, lung inflammation, and oxidative stress in vivo compared to TOB solution. TD-αT NEs could prove beneficial in treating chronic pulmonary infections induced by P. aeruginosa through a comprehensive strategy, specifically enhancing biofilm eradication, reducing inflammation, and alleviating oxidative stress.