Microbially induced corrosion (MIC), caused by iron-cycling microorganisms that directly uptake electrons from metallic iron, is a serious economic and environmental problem. Iron corrosion is inhibited at pH above 9.0 in the presence of carbonate by the formation of a passivating film, but the possibility of direct oxidation of metallic iron by anaerobic alkaliphiles has not been thoroughly investigated. This bioinduced process may pose a serious environmental hazard under anaerobic alkaline conditions of underground radioactive waste disposal in metal containers with bentonite clays. We used Geoalkalibacter ferrihydriticus, an anaerobic iron-cycling bacterium capable of both dissimilatory iron reduction and anaerobic iron oxidation, as a model organism to investigate the microbial ability to utilize Fe0 from steel wire as an electron donor under anaerobic autotrophic conditions at pH 9.5. During bacterial growth, corrosion of the steel wire was induced and accompanied by intense H2 production and precipitation of a solid phase. Mössbauer spectroscopy revealed that green rust with siderite admixture was the major mineral formed during Fe oxidation. Protons appeared to be the only thermodynamically favorable electron acceptor for G. ferrihydriticus. Their reduction could lead to hydrogen production. Genomic analysis supported the proposal of such a metabolic mode for the organism. Thus, we have shown that MIC can be realized under anaerobic alkaline conditions by iron-cycling microorganisms in the absence of organic substrates. Microbial hydrogen production may facilitate the further development of authigenic microflora, which could further increase corrosion in radioactive waste repositories and reduce the barrier properties of bentonite clays.IMPORTANCEMicrobially induced corrosion (MIC) is a problem with significant economic damage. MIC processes occurring under anaerobic conditions at neutral pH have been actively studied over the last decades. Meanwhile, MIC processes under anaerobic alkaline conditions remain very poorly understood, although they represent a serious environmental problem, as such conditions are characteristic of the geological disposal of nuclear waste stored in metal containers isolated by clays. Our studies of the corrosion of steel by the anaerobic iron-cycling bacterium Geoalkalibacter ferrihydriticus at pH 9.5 in the absence of any organic matter have shown that this process is possible and can be accompanied by the active release of hydrogen. The formation of this gas can trigger the development of an authigenic anaerobic microflora that uses it as an electron donor and can negatively affect the insulating properties of the clay barrier through microbial metabolic activity.
- Klíčová slova
- Geoalkalibacter ferrihydriticus, alkaline environments, direct Fe0-oxidation, iron-cycling anaerobes, microbially induced corrosion, protons reduction, steel,
- MeSH
- anaerobióza MeSH
- autotrofní procesy MeSH
- koncentrace vodíkových iontů MeSH
- koroze MeSH
- ocel * chemie MeSH
- oxidace-redukce MeSH
- železo * metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- ocel * MeSH
- železo * MeSH
Additive friction stir deposition (AFSD) is a novel solid-state additive manufacturing technique that circumvents issues of porosity, cracking, and properties anisotropy that plague traditional powder bed fusion and directed energy deposition approaches. However, correlations between process parameters, thermal profiles, and resulting microstructure in AFSD still need to be better understood. This hinders process optimization for properties. This work employs a framework combining supervised machine learning (SML) and physics-informed neural networks (PINNs) to predict peak temperature distribution in AFSD from process parameters. Eight regression algorithms were implemented for SML modeling, while four PINNs leveraged governing equations for transport, wave propagation, heat transfer, and quantum mechanics. Across multiple statistical measures, ensemble techniques like gradient boosting proved superior for SML, with the lowest MSE of 165.78. The integrated ML approach was also applied to classify deposition quality from process factors, with logistic regression delivering robust accuracy. By fusing data-driven learning and fundamental physics, this dual methodology provides comprehensive insights into tailoring microstructure through thermal management in AFSD. The work demonstrates the power of bridging statistical and physics-based modeling for elucidating AM process-property relationships.
This study presents the results of archaeometallurgical investigation of iron objects from the Sanctuary of Apollo in ancient Didyma, dating to the Archaic period (7th to the early 5th centuries BCE). The analysed precision work tools and semi-formed objects exhibit distinct material characteristics that differentiate them from other iron-steel artefacts of both small and large formats (weapons, implements, and architectural fittings) so far investigated in the Aegean. They were made of medium, high, and ultra-high carbon steel. Three objects belonging to this latter category consist of remarkably clean, homogeneous, and high-quality steel. After presenting the analytical results, this article discusses various explanatory models for the production of these objects and attempts to answer questions about the motivations for this innovation, highlighting their functional characteristics and context of production and consumption.
Plasma-activated water (PAW) has been shown to have antimicrobial properties, making it a promising tool for surface decontamination. This study evaluated the ability of PAW generated from high voltage atmospheric cold plasma to remove Salmonella from common surfaces (stainless steel (SS), polyvinyl chloride (PVC), concrete, and wood) found in poultry houses. PAW was generated by exposing distilled water to atmospheric cold plasma in 80% humid air at 90 kV and 60 Hz for 30 min. The resulting PAW contained 1120 ppm of nitrate and 1370 ppm of hydrogen peroxide, with a pH of 1.83. PAW was then applied to coupons of SS, PVC, wood, and concrete surfaces inoculated with 7-8 log10 CFU of cocktail of Salmonella spp. (S. Typhimurium, S. Newport, S. Montevideo, and S. Enteritidis). PAW effectively reduced Salmonella levels on SS and PVC surfaces to below the detection limit within 30 s. On wood surfaces, a longer treatment time of 7.5 min was required to achieve a maximum reduction of 2.63 log10 CFU, likely due to the porosity of the wood limiting PAW contact with the bacteria. On concrete surfaces, the reduction in Salmonella levels was only 0.98 log10 CFU. This was likely due to the greater surface roughness and high alkalinity, which neutralized the PAW species.
- Klíčová slova
- Cold plasma, Decontamination, Plasma-activated water, Poultry house, Salmonella spp,
- MeSH
- bydlení zvířat * MeSH
- dekontaminace * metody MeSH
- dezinficiencia farmakologie MeSH
- dřevo mikrobiologie chemie MeSH
- drůbež * mikrobiologie MeSH
- konstrukční materiály mikrobiologie MeSH
- nerezavějící ocel MeSH
- peroxid vodíku farmakologie MeSH
- plazmové plyny * farmakologie MeSH
- počet mikrobiálních kolonií MeSH
- polyvinylchlorid chemie MeSH
- Salmonella * růst a vývoj MeSH
- voda * chemie MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- hodnotící studie MeSH
- Názvy látek
- dezinficiencia MeSH
- nerezavějící ocel MeSH
- peroxid vodíku MeSH
- plazmové plyny * MeSH
- polyvinylchlorid MeSH
- voda * MeSH
Gastroenteritis caused by Campylobacter represents the most common reported foodborne bacterial illness worldwide, followed by salmonellosis. Both diseases are often caused by the consumption of contaminated, insufficiently heated poultry meat. This can result from contamination of the meat during the slaughtering processes. Food contact surfaces like stainless steel or plucking fingers contribute significantly to cross-contamination of poultry carcasses. Modification of these surfaces could lead to a reduction of the bacterial burden, as already proven by successful application in various food industry sectors, such as packaging.In this study, nanoscale silica-coated and uncoated stainless-steel surfaces and plucking fingers were compared on a pilot scale regarding attachment and detachment of Campylobacter jejuni, Salmonella Enteritidis and Escherichia coli.The bacteria did not adhere less to the coated plucking fingers or stainless-steel sections than to the uncoated ones. The coating also did not lead to a significant difference in detachment of Campylobacter jejuni, Salmonella Enteritidis and Escherichia coli from the investigated surfaces compared to the uncoated ones.Our study did not reveal any differences between the coated and uncoated surfaces with regard to the investigated bacteria. In order to achieve a better adaptation of the coating to slaughterhouse conditions, future studies should focus on its further development based on the investigation of specific coating parameters.
- Klíčová slova
- Cross-contamination, Food contact surfaces, Nanomaterials, Poultry, Slaughtering,
- MeSH
- bakteriální adheze * MeSH
- Campylobacter jejuni * účinky léků fyziologie MeSH
- drůbež mikrobiologie MeSH
- Escherichia coli * růst a vývoj fyziologie MeSH
- jatka * MeSH
- kontaminace potravin prevence a kontrola analýza MeSH
- maso mikrobiologie MeSH
- nerezavějící ocel * MeSH
- oxid křemičitý chemie MeSH
- potravinářská mikrobiologie MeSH
- Salmonella enteritidis * účinky léků fyziologie růst a vývoj MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- nerezavějící ocel * MeSH
- oxid křemičitý MeSH
LM5 alloy is suitable for metal castings for marine and aesthetic uses due to its admirable resistance to corrosion. In order to make intricate shapes in the LM5 alloy, this study intends to assess the impact of Wire Electric Discharge Machining process variables, like Pulse on Time (Ton), Pulse off Time (Toff), Gap Voltage (GV) and Wire Feed (WF) on responses like Material Removal Rate (MRR), Surface Roughness (SR), and Kerf Width (Kw). The LM5 aluminium alloy plate was produced through stir casting process. SEM, EDAX and XRD images confirm the LM5 Al alloy's microstructure and crystal structure. WEDM studies were conducted using design of experiments approach based on L9 orthogonal array and analysed using Taguchi's Signal to Noise Ratio (S/N) analysis. Pulse on Time has the greatest statistical effects on MRR (68.25%), SR (79.46%) and kerf (81.97%). In order to assess the surface integrity of the WEDM machined surfaces, the SEM study on the topography was conducted using the optimum surface roughness process variables: Ton 110 μs, Toff 50 μs, GV 40 V, and WF 9 m/min. SEM images show the recast layer and its thickness. The average absolute error for MRR is 1.69%, SR is 3.89% and kerf is 0.88%, based on mathematical (linear regression) models. The Taguchi's Signal to Noise ratio analysis is the most appropriate for single objective optimization of responses.
- MeSH
- hliník * chemie MeSH
- mikroskopie elektronová rastrovací MeSH
- povrchové vlastnosti * MeSH
- slitiny * chemie MeSH
- testování materiálů MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- hliník * MeSH
- slitiny * MeSH
Metals are widely utilized as implant materials for bone fixtures as well as stents. Biodegradable versions of these implants are highly desirable since patients do not have to undergo a second surgery for the materials to be removed. Attractive options for such materials are zinc silver alloys since they also offer the benefit of being antibacterial. However, it is important to investigate the effect of the degradation products of such alloys on the surrounding cells, taking into account silver cytotoxicity. Here we investigated zinc alloyed with 1 % of silver (Zn1Ag) and how differently concentrated extracts (1 %-100 %) of this material impact human umbilical vein endothelial cells (HUVECs). More specifically, we focused on free radical generation and oxidative stress as well as the impact on cell viability. To determine free radical production we used diamond-based quantum sensing as well as conventional fluorescent assays. The viability was assessed by observing cell morphology and the metabolic activity via the MTT assay. We found that 1 % and 10 % extracts are well tolerated by the cells. However, at higher extract concentrations we observed severe impact on cell viability and oxidative stress. We were also able to show that quantum sensing was able to detect significant free radical generation even at the lowest tested concentrations.
- Klíčová slova
- Biodegradable zinc, Cytotoxicity, Free radical, NV center, Nanodiamond, Relaxometry,
- MeSH
- biokompatibilní materiály chemie farmakologie MeSH
- endoteliální buňky pupečníkové žíly (lidské) * účinky léků MeSH
- lidé MeSH
- nanodiamanty * chemie MeSH
- oxidační stres * účinky léků MeSH
- slitiny * chemie MeSH
- stříbro toxicita chemie MeSH
- testování materiálů metody MeSH
- viabilita buněk * účinky léků MeSH
- volné radikály metabolismus MeSH
- vstřebatelné implantáty škodlivé účinky MeSH
- zinek * MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- biokompatibilní materiály MeSH
- nanodiamanty * MeSH
- slitiny * MeSH
- stříbro MeSH
- volné radikály MeSH
- zinek * MeSH
Using a cutting-edge net-shape manufacturing technique called Additive Layer Manufacturing (ALM), highly complex components that are not achievable with conventional wrought and cast methods can be produced. As a result, the aerospace sector is paying closer attention to using this technology to fabricate superalloys based on nickel to develop the holistic gas turbine. Because of this, there is an increasing need for the mechanical characterisation of such material. Conventional mechanical testing is hampered by the limited availability of material that has been processed, especially given the large number of process factors that need to be assessed. Thus, the present study focuses on manufacturing CM247LC Ni-based superalloy with exceptional mechanical characteristics by laser powder bed fusion (L-PBF). This study evaluates the effect of input process variables such as laser power, scan speed, hatch distance and volumetric energy density on the mechanical performance of the LPBF CM247LC superalloy. The maximum value of as-built tensile strength obtained in the study is 997.81 MPa. Plotting Pearson's heatmap and the Feature importance (F-test) was used in the data analysis to examine the impact of input parameters on tensile strength. The accuracy of the tensile strength data classification by machine learning algorithms, such as k-nearest neighbours, Naïve Baiyes, Support vector machine, XGBoost, AdaBoost, Decision tree, Random forest, and logistic regression algorithms, was 92.5%, 83.75%, 83%, 85%, 87.5%, 90%, 91.25%, and 77.5%, respectively.
Stainless steel welders are exposed to heavy filler metals. We evaluated the concentration of these metals in whole blood and urine, and the relevant biochemical parameters in relation to the total chromosomal aberrations (CAs), chromatid-type (CTA-type, CTAs) and chromosome-type (CSA-type, CSAs), in 117 welders and control individuals. Statistically higher concentrations of the total Cr, Ni and Mn were observed in whole blood and urine of welders, and the concentrations were higher in welders who smoked. On the contrary, concentrations of urinary heavy metals Cr and Mn adjusted for creatinine were significantly higher in the control groups. A statistically higher frequency of total CAs was observed in the whole group of welders, and also in the non-smoking welders, as compared to controls. The frequency of total CAs significantly correlated with the concentration of Cr, Ni and Mn in whole blood (R=0.61, P˂0.0001, R=0.33, P˂0.0001 and R=0.66, P˂0.0001, respectively), with urinary concentrations of Ni and Mn (R=0.27, P=0.003 and R=0.28, P=0.003, respectively) and with urinary concentrations of Cr, Ni and Mn adjusted for creatinine (R=0.22, P=0.029, R=0.26, P=0.005 and R=0.20, P=0.030, respectively). Likewise, the frequency of CTA-types significantly correlated with the concentration of Cr and Mn in whole blood (R=0.31, P=0.0007 and R=0.34, P=0.0002). The frequency of CSA-types significantly correlated with concentrations of Cr, Ni and Mn in whole blood (R=0.43, P˂0.0001, R=0.38, P˂0.0001 and R=0.46, P˂0.0001, respectively). The statistically higher values of serum creatinine and total bilirubin were detected in all welders, as well as in smokers when compared to the corresponding controls. The exposure to heavy metals in welders increased the frequencies of CAs and altered the balance between urinary excretion of heavy metals and their possible accumulation.
- Klíčová slova
- Biochemical parameters, Chromosomal aberrations, Effects of smoking, Metal concentrations in urine and whole blood, Welders,
- MeSH
- chrom moč krev MeSH
- chromozomální aberace * chemicky indukované MeSH
- dospělí MeSH
- kouření škodlivé účinky moč krev MeSH
- kreatinin moč krev MeSH
- lidé středního věku MeSH
- lidé MeSH
- mangan moč krev MeSH
- nerezavějící ocel MeSH
- nikl moč krev MeSH
- pracovní expozice * škodlivé účinky analýza MeSH
- studie případů a kontrol MeSH
- svařování * MeSH
- těžké kovy * moč krev MeSH
- Check Tag
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- chrom MeSH
- kreatinin MeSH
- mangan MeSH
- nerezavějící ocel MeSH
- nikl MeSH
- těžké kovy * MeSH
Interfaces between AISI 304 stainless steel screws and cranial bone were investigated after long-term implantation lasting for 42 years. Samples containing the interface regions were analyzed using state-of-the-art analytical techniques including secondary ion mass, Fourier-transform infrared, Raman, and X-ray photoelectron spectroscopies. Local samples for scanning transmission electron microscopy were cut from the interface regions using the focused ion beam technique. A chemical composition across the interface was recorded in length scales covering micrometric and nanometric resolutions and relevant differences were found between peri-implant and the distant cranial bone, indicating generally younger bone tissue in the peri-implant area. Furthermore, the energy dispersive spectroscopy revealed an 80 nm thick steel surface layer enriched by oxygen suggesting that the AISI 304 material undergoes a corrosion attack. The attack is associated with transport of metallic ions, namely, ferrous and ferric iron, into the bone layer adjacent to the implant. The results comply with an anticipated interplay between released iron ions and osteoclast proliferation. The interplay gives rise to an autocatalytic process in which the iron ions stimulate the osteoclast activity while a formation of fresh bone resorption sites boosts the corrosion process through interactions between acidic osteoclast extracellular compartments and the implant surface. The autocatalytic process thus may account for an accelerated turnover of the peri-implant bone.
- Klíčová slova
- biocorrosion, implant, peri-implant bone, remodelling, stainless steel AISI 304,
- MeSH
- fotoelektronová spektroskopie MeSH
- koroze MeSH
- kostní šrouby * škodlivé účinky MeSH
- lebka * patologie MeSH
- lidé MeSH
- nerezavějící ocel * chemie MeSH
- povrchové vlastnosti MeSH
- Ramanova spektroskopie MeSH
- rozhraní kost/implantát MeSH
- spektroskopie infračervená s Fourierovou transformací MeSH
- železo chemie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- nerezavějící ocel * MeSH
- železo MeSH
