-
Archives of Environmental Contamination... Jun 2024Plastics are synthetic organic compounds whose widespread use generates enormous waste. Different processes, such as mechanical abrasion, microbiological activity, and...
Plastics are synthetic organic compounds whose widespread use generates enormous waste. Different processes, such as mechanical abrasion, microbiological activity, and UVB irradiation, can fragment the plastic material and generate microplastics (MPs). MPs are ubiquitous, and various organisms, including humans, can ingest or inhale them, with potential adverse health effects. The differences between UV-aged and virgin particles were studied to evaluate the genotoxic damage and oxidative stress induced by polystyrene MPs with 1 and 5 µm sizes on the monocyte-like cell line (THP-1). Fourier transform infrared spectroscopy and Ζ-potential measurements were used to characterise MP particles after UVB exposure. Cells exposed to MPs show a widespread change in the cellular environment with the generation of reactive oxidative species (ROS), as indicated by the increased malondialdehyde level. The occurrence of genotoxic damage is correlated to the smaller size and ageing state of the MPs. The biochemical and genomic alterations observed in this in vitro study suggest that MPs, ubiquitous pollutants, following natural degradation and oxidation processes can cause various adverse effects on the health of the exposed population, making it necessary to carry out further studies to better define the real risk.
PubMed: 38896243
DOI: 10.1007/s00244-024-01073-x -
Ethnoarchaeology 2024The identification of beer production in past societies remains a challenge as very few studies have discussed its material evidence. Our investigation in Senegal aimed...
The identification of beer production in past societies remains a challenge as very few studies have discussed its material evidence. Our investigation in Senegal aimed at filling this gap. We documented 14 beer houses and several beer cooking areas in five Bedik villages and excavated a beer house and associated cooking area in a recently abandoned village. We recorded the architectural attributes of the beer-making structures (location, shape, size, materials, techniques, internal layouts). We also analyzed associated pottery combining typometry and use-wear. Such an integrated study revealed that the pottery types (large vessels, small bottles) and use-alteration (inner non-abrasive attrition), are the most distinctive features for identifying beer production, besides the beer houses' internal layouts (wedge holes of large pottery, altar) and the beer cooking areas' location outside the compound. Exploration of the same criteria in other cultural contexts in Africa lends support to the broader significance of these findings.
PubMed: 38895163
DOI: 10.1080/19442890.2024.2334509 -
Materials (Basel, Switzerland) Jun 2024The present work is aimed at studying the effects of the magnetorheological finishing process, using a low-frequency alternating magnetic field, on the finishing...
The present work is aimed at studying the effects of the magnetorheological finishing process, using a low-frequency alternating magnetic field, on the finishing performance of 6063 aluminum alloy. The study investigates the influence of key excitation parameters such as current, frequency, excitation gap, and iron powder diameter on the material removal and surface roughness (Ra) of the finished workpiece by experiments. This study employs a single-factor experimental method, and the finish surface is analyzed by a Zigo non-contact white light interferometer. The magnetic field strength in the processing area increases with the increase in the excitation current and decreases with the increase in the excitation gap. When the current frequency is set to 1 Hz, the circulation and renewal of abrasives in the magnetic cluster is most sufficient, resulting in the optimal surface roughness value for the workpiece. According to the experimental results of the excitation parameters, more suitable process parameters were selected for a two-stage finishing experiment. The surface roughness of 6063 aluminum alloy was improved from 285 nm to 3.54 nm. Experimental results highlighted that the magnetorheological finishing using a low-frequency alternating magnetic field is a potential technique for obtaining nano-scale finishing of the 6063 aluminum alloy.
PubMed: 38893934
DOI: 10.3390/ma17112670 -
Materials (Basel, Switzerland) May 2024Various contents of carbon fibers (CFs) and potassium titanate whiskers (PTWs) were added to an Fe-based impregnated diamond bit (IDB) matrix to enhance its adaptability...
Various contents of carbon fibers (CFs) and potassium titanate whiskers (PTWs) were added to an Fe-based impregnated diamond bit (IDB) matrix to enhance its adaptability to percussive-rotary drilling. A series of mechanical tests were conducted successively to find the effects of the reinforcing materials on the properties of the Fe-based IDB samples. Then, the fracture surfaces of the samples were analyzed via scanning electron microscopy (SEM) and energy-dispersive spectroscopy, and the worn surfaces and abrasive debris of the samples were analyzed using a laser scanning confocal microscope and SEM. The results show that both the CF and PTW can effectively improve the hardness and bending strength of an Fe-based IDB matrix, and those parameters reached their maximum values at the additive amount of 1 wt%. However, the CF had a better enhancement effect than the PTW. Furthermore, the CF improved the impact wear resistance of the IDB matrix, with a minimum wear rate of 2.38 g/min at the additive amount of 2 wt%. However, the PTW continuously weakened the impact wear resistance of the IDB matrix with increases in its content. Moreover, the morphologies of the worn surfaces indicated that the minimum roughness of the CF-reinforced IDB matrix decreased significantly to as low as 4.91 μm, which was 46.16% lower than that without CF, whereas the minimum roughness of the PTW-reinforced samples decreased by 11.31%. Meanwhile, the abrasive debris of the CF-reinforced samples was more uniform and continuous compared to that of the PTW-reinforced samples. Overall, the appropriate addition of CF or PTWs can enhance the mechanical properties of Fe-based IDB matrices, which can be used on different formations based on their impact wear resistance.
PubMed: 38893912
DOI: 10.3390/ma17112645 -
Materials (Basel, Switzerland) May 2024The main motivation for this research was to improve the properties of geopolymers by reinforcement using synthetic and natural fibers, and to gain new knowledge...
The main motivation for this research was to improve the properties of geopolymers by reinforcement using synthetic and natural fibers, and to gain new knowledge regarding how the nature and/or the quantity of reinforcement fibers influences the properties of the final geopolymers. The main objective was to investigate the effects of different types of reinforcement fibers on the properties of the geopolymers. These reinforcement fibers were mainly environmentally friendly materials that can be used as alternatives to ordinary Portland cement. The authors used fly ash and river sand as the raw materials for the matrix, and added carbon fibers (CF), flax fibers (FF), or a hybrid of both (CFM) as reinforcements. The samples were prepared by mixing, casting, and curing, and then subjected to various tests. The main research methods used were compressive strength (CS), flexural strength (FS), water absorption (WA), abrasion resistance (Böhme's disk method), microstructure analysis (SEM), chemical composition (XRF), and crystal structure analysis (XRD). The results showed that the addition of fibers partially improved the mechanical properties of the geopolymers, as well as reducing microcracks. The CF-reinforced geopolymers exhibited the highest compressive strength, while the FF-reinforced geopolymers showed the lowest water absorption. The authors, based on previous research, also discussed the factors that influence fiber-matrix adhesion, and the optimal fiber content for geopolymers.
PubMed: 38893897
DOI: 10.3390/ma17112633 -
Materials (Basel, Switzerland) May 2024An express method for assessing the effectiveness of lubricating compositions with nano-additives of various chemical compositions is proposed, and a joint analysis of...
An express method for assessing the effectiveness of lubricating compositions with nano-additives of various chemical compositions is proposed, and a joint analysis of experimental data on the changes in the value of wear and the level of damage to the surface layers of metallic friction pairs was performed. The variation in the current relative hardness of the sample's surface, the variation in the current relative material damage level, the current value of wear, and the current level of the coefficient of friction were chosen as the key parameters to conduct a performance assessment. The level of material damage in the contact zone was determined using the parameters of the statistical law of hardness value scattering. Based on an analysis of data in the literature, it was observed that the structural changes occurring in metallic materials during long-term, cyclic, static, and frictional loading are correlated with changes in the statistical characteristics of the hardness scattering results. An experimental substantiation of the proposed method was carried out for steel-sliding friction pairs using lubricating compositions based on Greaseline Lithium BIO Rail 000 oil manufactured by AIMOL with nano-additives of copper, magnesium and aluminum alloys, graphite, and two grades of medium-carbon steel. According to the system of indicators presented in this research, the greatest efficiency (in terms of increasing the wear resistance of friction steel pairs) was achieved with lubricating compositions including nano-powder additives made of steel, which have lower hardness. For the friction experiments, where the determining factor was abrasive wear, such lubricants ensured minimal damage and wear to the friction surface, while the value of the friction coefficient was maintained at a level that is optimal for wheel-rail friction pairs.
PubMed: 38893763
DOI: 10.3390/ma17112499 -
Polymers May 2024This study investigates the impact of mechanical alteration on resin composite surfaces and its subsequent effect on repair bond strength. A total of 100 resin composite...
This study investigates the impact of mechanical alteration on resin composite surfaces and its subsequent effect on repair bond strength. A total of 100 resin composite disks were prepared and were allocated for 24 h or 1 year of artificial aging. Specimens were embedded in epoxy resin, and the composite surfaces were mechanically altered using either diamond burs or air abrasion with aluminum oxide or glass beads. A universal bonding material was applied and a 2 mm circular and 3 mm high repair composite cylinder were prepared using a Teflon mold. Then, the specimens were tested for their shear bond strength, and the de-bonded specimens were observed under a scanning electron microscope to determine the failure pattern. SPSS 26.0 statistical software was used to analyze the data. Two-way ANOVA showed a statistically significant effect of mechanical alteration and aging on the shear bond strength of S-PRG-filler-based resin composite ( < 0.05). Surface modification with a fine diamond bur showed a significantly higher bond strength in both 24-h- and 1-year-aged specimens. Surface modification with alumina significantly increased the bond strength of 1-year-aged specimens; however, it was statistically insignificant for 24 h-aged specimens. Mechanical alteration with a fine diamond bur and 50-micron alumina can improve the repair bond strength of the composite.
PubMed: 38891435
DOI: 10.3390/polym16111488 -
Healthcare (Basel, Switzerland) May 2024Dental wear arises from mechanical (attrition or abrasion) and chemical (erosion) factors. Despite its prevalence and clinical significance, accurately measuring and...
Dental wear arises from mechanical (attrition or abrasion) and chemical (erosion) factors. Despite its prevalence and clinical significance, accurately measuring and understanding its causes remain challenging in everyday practice. This one-year study with 39 participants involved comprehensive examinations and full-arch intraoral scans at the start and after 12 months. Volume loss exceeding 100 µ on each tooth's surfaces (buccal, lingual/palatine and incisal/occlusal) was measured by comparing three-dimensional scans from both time points. This study also assessed factors such as abrasion and erosion through clinical exams and questionnaires. There were no significant differences in dental wear in participants with sleep bruxism. However, noticeable wear occurred in the front teeth of those with waking bruxism and joint-related symptoms. Increased wear was associated with frequent consumption of acidic drinks, regular swimming, dry mouth, nocturnal drooling and heartburn, while no significant wear was found in patients with reflux. The used methodology proved effective in accurately assessing the progression of dental wear, which is important as many patients may initially be asymptomatic. The variability observed in dental wear patterns underscores the need to develop specific software applications that allow immediate and efficient comparison of wear areas based on extensive analysis of patient databases.
PubMed: 38891145
DOI: 10.3390/healthcare12111069 -
The Saudi Dental Journal Jun 2024To explore the feasibility and effectiveness of using sandblasting with aluminum oxide particles to improve the shear bond strength of labial veneer restorations in...
OBJECTIVES
To explore the feasibility and effectiveness of using sandblasting with aluminum oxide particles to improve the shear bond strength of labial veneer restorations in dentistry.
MATERIALS AND METHODS
A sample size of 50 extracted teeth was divided into five groups, with each group containing ten teeth (n = 10) subject to different treatment protocols. Group 1the control group, underwent conventional surface treatment for labial veneer restorations, including the application of phosphoric acid etchant and bonding protocols. Groups 2 and 3 underwent micro-abrasion using aluminum oxide particles alone for durations of 30 and 45 s, respectively. Groups 4 and 5 experienced a combined approach of micro-abrasion for 30 and 45 s, respectively, followed by conventional surface treatment. The shear bond strength test was performed on each specimen. The resulting modes of failure and surface characteristics were then examined under a digital microscope.The data was analyzed statistically using a one-way analysis of variance (ANOVA) and a post hoc test.
RESULTS
Significant differences were observed in shear bond strength among the five groups (p < 0.05). The group that underwent conventional + 45-second micro-abrasion treatment exhibited the highest mean shear bond strength (25.69 MPa), while the conventional (controlled) group had the lowest (9.01 MPa).
CONCLUSION
Fusing sandblasting and aluminum oxide particles could improve the bond strength of labial veneer restorations. Yet, more research is needed to refine this technique for practical application. This includes a broad array of cement types, particle sizes, and clinical situations to ensure the long-term success of veneer restorations.
PubMed: 38883910
DOI: 10.1016/j.sdentj.2024.04.003 -
Research Square Jun 2024Despite potential benefit, outpatient use of topical ophthalmic anesthetics can result in poor healing, infection, scar, and blindness. An unbiased analysis of...
BACKGROUND
Despite potential benefit, outpatient use of topical ophthalmic anesthetics can result in poor healing, infection, scar, and blindness. An unbiased analysis of randomized controlled trials (RCTs) is needed to examine their effectiveness and safety compared with placebo or other treatments for corneal abrasions.
METHODS
Cochrane Central Register of Controlled Trials, MEDLINE, Embase.com, Latin American and Caribbean Health Sciences, ClinicalTrials.gov, and the World Health Organization International Clinical Trials Registry Platform were searched on February 10, 2023, without restriction on language or publication date.
RESULTS
Systematic review and meta-analysis of nine RCTs describing 314 participants with post-traumatic abrasions and 242 participants with post-surgical abrasions, with a median study length of 7 days (interquartile range, 7-14), show no evidence of a difference in pain control between anesthetics and placebo at 24 hours in post-trauma cases. Self-reported pain at 24 hours is reduced with anesthetics plus topical nonsteroid anti-inflammatory drug in post-surgical participants (mean difference [MD], -5.72 on a 10-point scale; 95% CI, -7.35 to -4.09; 1 RCT; 30 participants) and at 48 hours with anesthetics alone in post-trauma participants (MD, -5.68; 95% CI, -6.38 to -4.98; 1 RCT; 111 participants). Anesthetics are associated with 37% increased risk of non-healing defects (risk ratio, 1.37; 95% CI, 0.78 to 2.42; 3 RCTs; 221 post-trauma participants). All evidence is of very low certainty. Over 50% of trials have an overall high risk of bias.
CONCLUSIONS
Available evidence is insufficient to support outpatient use of topical anesthetics for corneal abrasions with respect to pain, re-epithelialization, and complication risk.
PubMed: 38883773
DOI: 10.21203/rs.3.rs-4160700/v1