Delving into the study of lactic acid bacteria and yeasts distribution in table olive biofilms using a non-destructive procedure.

To turn table olives into appropriate carriers of beneficial bacteria and yeasts to consumers, it is essential to have reliable methods for analysing microorganisms in biofilms. This work validates the application of a non-destructive procedure to study the lactic acid bacteria and yeasts distribution in fruits during Spanish-style green table olive fermentations. Laboratory-scale fermentations were inoculated simultaneously with three Lactiplantibacillus pentosus strains (LPG1, 119, and 13B4) and two yeasts (Wickerhamomyces anomalus Y12 and Saccharomyces cerevisiae Y30), all of them natives of table olive fermentations. Data showed that L. pentosus LPG1 and yeasts W. anomalus Y12 were quite prone to colonise olive biofilms, but only the Lactiplantibacillus strain also can penetrate the epidermis of the fruit and colonise the flesh. Applying a non-destructive treatment consisting in shelling the fruits with glass beads led to obtaining similar lactic acid bacteria and yeast recovery than the classical stomacher destructive method. However, the glass bead procedure improved the quality of the metagenomics analysis (especially when using 16 S rRNA gene-based sequencing). Results show the great utility of procedures that do not destroy the fruit for studying fermented vegetable biofilms.

Purification of lipase from Burkholderia metallica fermentation broth in a column chromatography using polymer impregnated resins.

In this work, porous glass beads grafted with polyethylene glycol (PEG) were used as an adsorbent to purify lipase from Burkholderia metallica in column chromatography. The purification parameters viz. salt stability, types and concentrations of PEG and salt, pH of the binding solution, and flow rate were studied to determine the performance of the purification system in an XK16/20 column. The crude lipase was mixed with different types and concentrations of salts 1-5% (w/w) (sodium citrate, potassium citrate, and sodium acetate) and subjected to the column containing the polymeric glass bead. One-variable-at-a-time experimentation revealed that 20% (w/w) PEG 6000 g/mol impregnated glass beads with a binding solution of 5% sodium citrate at pH 7.7, a flow rate of 1.0 mL/min and extraction time of 10 min resulted in the highest purification factor and recovery yield at 3.67 and 88%, respectively. The purified lipase has 55 ∼ 60 kDa molecular mass. The outcome of the study showed PEG could be applied to modify the inert glass beads into polymeric form, providing a biocompatible and mild separation condition for lipase. Thus, PEG could be successfully applied for the purification of lipase from B. metallica fermentation broth using column chromatography.

The effects of different silicatization and silanization protocols on the bond durability of resin cements to new high-translucent zirconia.

OBJECTIVE: The aim of this study was to assess the influence of different silicatization protocols with various silane treatment methods on the bond performance to high-translucent zirconia. MATERIALS AND METHODS: High-translucent zirconia specimens were assigned to five groups according to mechanical surface pretreatment: as-sintered (Con), 0.2 MPa alumina sandblasting (AB2), tribochemical silica coating (TSC), 0.2 and 0.4 MPa glass bead air abrasion (GB2) and (GB4). Each group was subjected to 4 different cementation protocols: Panavia SA Universal (SAU), Panavia SA plus (SAP), silane + SAP (S-SAP), and Universal adhesive + SAP (U-SAP). Tensile bond strength (TBS) was measured after 24 h and 10,000 thermocycling (TC). Surface topography, surface energy, and elemental composition of the abraded zirconia surface analyses were completed. TBS data was analyzed using the Weibull analysis method. Surface roughness and surface energy were compared by one-way ANOVA analysis of variance (α = 0.05). RESULTS: After 24 h, higher TBS was achieved with all cementation protocols in AB2 and TSC, also, in GB2 with all protocols except U-SAP, and in GB4 with SAU and S-SAP. After aging, GB4/S-SAP, GB2/S-SAP, AB2/U-SAP, and TSC/S-SAP showed the highest bond strength. GB groups showed the lowest surface roughness and highest surface energy. CONCLUSION: Glass bead abrasion achieved the durable bond strength to high-translucent zirconia using a separate silane coupling agent while altered surface chemistry, surface energy, and roughness without effect on morphology. CLINICAL RELEVANCE: Glass bead air abrasion is an alternative to alumina sandblasting and tribochemical silica coating and improves bond strength to high translucent zirconia.

Effect of Air-Particle Abrasion Protocol and Primer on The Topography and Bond Strength of a High-Translucent Zirconia Ceramic.

PURPOSE: To evaluate effect of air-particle abrasion protocol and primer on surface topography and bond strength of resin cement to high-translucent zirconia ceramics. MATERIALS AND METHODS: Two hundred disk-shaped high-translucent zirconia specimens of 5Y-PSZ were prepared. The specimens were assigned to 5 groups in terms of particle type and air-particle abrasion pressure: (1) control, (2) alumina with 0.2 MPa-air pressure [AB-0.2], (3) alumina with 0.4 MPa-air pressure [AB-0.4], (4) glass beads with 0.2 MPa-air pressure [GB-0.2], and (5) glass beads with 0.4 MPa-air pressure [GB-0.4]. Two different primers 1% MDP (Experimental) and MDP-silane primer (Clearfil Ceramic Primer Plus) was also tested. Stainless steel rods were bonded to the 5Y-PSZ specimens with PANAVIA V5. For each group, the tensile bond strength (TBS) was measured after 24-hour water storage (n = 10) and after 5000 thermal-cycling (n = 10) at crosshead speed of 2 mm/min. The data were statistically analyzed using Weibull analysis. Surface roughness (Sa) was measured using a 3D-Laser Scanning Confocal Microscope (n = 5) and analyzed by t-test with Bonferroni correction. Surface topography using scanning electron microscopy (SEM) and surface elemental analysis using energy dispersion spectroscopy (EDX), and cross-section SEM at the interface with composite cement were also investigated. RESULTS: In MDP-silane groups, the highest TBS was observed in AB-0.4 after 24 hours and GB-0.4 after thermal-cycling (p < 0.05). In MDP groups, AB groups resulted in the significantly higher TBS than GB groups (p < 0.05). AB-0.4 group showed the highest Sa value compared to all groups (p < 0.005), meanwhile GB groups did not show different Sa compared to control (p > 0.005). CONCLUSION: Air-abrasion with different particle and blasting pressure can improve bonding to zirconia with proper primer selection. Particularly, glass beads abrasion followed by MDP-silane primer and alumina abrasion followed by MDP primer alone provided stable bond strength of resin cement to high-translucent zirconia after aging. High-translucent zirconia abraded with glass beads achieves a desirable bonding performance without creating surface microcracks which may hinder zirconia's mechanical properties.

Igbo-Ukwu at 50: A Symposium on Recent Archaeological Research and Analysis.

As an introduction to several papers from the "Igbo-Ukwu at 50" symposium in September 2021, this article reviews the history of the discoveries and excavations, the early debates over chronology, and more recent research contributions that refine and expand our understanding of this unique site. These include new field investigations at Igbo Ukwu, new radiocarbon dates, textile analysis, chemical analyses of glass, and carnelian beads plus lead isotope analyses of leaded bronze and copper artifacts to identify source areas, and metallographic studies.

Comme introduction à plusieurs articles du symposium "Igbo-Ukwu at 50" en septembre 2021, cet article passe en revue l'histoire des découvertes et des fouilles, les premiers débats sur la chronologie et les contributions de recherche plus récentes qui affinent et élargissent notre compréhension de ce site unique. Il s'agit notamment de nouvelles enquêtes sur le terrain à Igbo-Ukwu, de nouvelles datations au radiocarbone, d'analyses textiles, d'analyses chimiques de perles de verre et de cornaline ainsi que d'études métallographiques et d'analyses isotopiques du plomb d'artefacts en bronze au plomb et en cuivre pour identifier les zones sources.

Acetotrophic sulfate-reducing consortia develop active biofilms on zeolite and glass beads in batch cultures at initial pH 3.

Sulfate-reducing microbial communities remain a suitable option for the remediation of acid mine drainage using several types of carrier materials and appropriate reactor configurations. However, acetate prevails as a product derived from the incomplete oxidation of most organic substrates by sulfate reducers, limiting the efficiency of the whole process. An established sulfate-reducing consortium, able to degrade acetate at initial acidic pH (3.0), was used to develop biofilms over granular activated carbon (GAC), glass beads, and zeolite as carrier materials. In batch assays using glycerol, biofilms successfully formed on zeolite, glass beads, and GAC with sulfide production rates of 0.32, 0.26, and 0.14 mmol H2S/L·d, respectively, but only with glass beads and zeolite, acetate was degraded completely. The planktonic and biofilm communities were determined by the 16S rRNA gene analysis to evaluate the microbial selectivity of the carrier materials. In total, 46 OTUs (family level) composed the microbial communities. Ruminococcaceae and Clostridiaceae families were present in zeolite and glass beads, whereas Peptococcaceae was mostly enriched on zeolite and Desulfovibrionaceae on glass beads. The most abundant sulfate reducer in the biofilm of zeolite was Desulfotomaculum sp., while Desulfatirhabdium sp. abounded in the planktonic community. With glass beads, Desulfovibrio sp. dominated the biofilm and the planktonic communities. Our results indicate that both materials (glass beads and zeolite) selected different key sulfate-reducing microorganisms able to oxidize glycerol completely at initial acidic pH, which is relevant for a future application of the consortium in continuous bioreactors to treat acidic streams. KEY POINTS: • Complete consumption of glycerol and acetate at acidic pH by sulfate reduction. • Glass beads and zeolite are suitable materials to form sulfate-reducing biofilms. • Acetotrophic sulfate-reducing bacteria attached to zeolite preferably.

Efficiency of three boar sperm enrichment techniques.

The objective of the study was to investigate the efficiency of three enrichment methods to separate boar spermatozoa. Twenty-four ejaculates from 12 boars (2 ejaculates/boar) were extended (30 × 106 spermatozoa/mL) in commercial Beltsville Thawing Solution. Each semen sample was processed with glass wool column (GW) and glass beads (GB) filtration and with the single-layer centrifugation (SLC) technique. Semen samples before (control; C) and after treatment were evaluated for sperm CASA motility/kinetics and concentration, viability, morphology and chromatin integrity. Data were analysed with mixed models. The concentration of total and motile spermatozoa was significantly decreased after treatment in groups GW and SLC, but not in group GB. Group GW showed increased values of WOB compared with both groups C and GB. Group GB showed greater values of rapid movement spermatozoa and lower values of slow movement spermatozoa compared with group C. In group SLC, higher values of VSL, LIN and STR were observed compared with group C. In conclusion, all techniques under examination enhanced various CASA variables. Based on our results, the GB method is a promising alternative separation technique for boar sperm and deserves further research regarding swine in vitro fertilization.

Improvement of carotenoid extraction from a recently isolated, robust microalga, Tetraselmis sp. CTP4 (chlorophyta).

In recent years, there has been increasing consumer interest in carotenoids, particularly of marine sustainable origin with applications in the food, cosmeceutical, nutritional supplement and pharmaceutical industries. For instance, microalgae belonging to the genus Tetraselmis are known for their biotechnologically relevant carotenoid profile. The recently isolated marine microalgal strain Tetraselmis sp. CTP4 is a fast-growing, robust industrial strain, which has successfully been produced in 100-m3 photobioreactors. However, there are no reports on total carotenoid contents from this strain belonging to T. striata/convolutae clade. Although there are several reports on extraction methods targeting chlorophytes, extraction depends on the strength of cell coverings, solvent polarity and the nature of the targeted carotenoids. Therefore, this article evaluates different extraction methods targeting Tetraselmis sp. CTP4, a strain known to contain a mechanically resistant theca. Here, we propose a factorial experimental design to compare extraction of total carotenoids from wet and freeze-dried microalgal biomass using four different solvents (acetone, ethanol, methanol or tetrahydrofuran) in combination with two types of mechanical cell disruption (glass beads or dispersion). The extraction efficiency of the methods was assessed by pigment contents and profiles present in the extracts. Extraction of wet biomass by means of glass bead-assisted cell disruption using tetrahydrofuran yielded the highest amounts of lutein and ß-carotene (622 ± 40 and 618 ± 32 µg g-1 DW, respectively). Although acetone was slightly less efficient than tetrahydrofuran, it is preferable due to its lower costs and toxicity.

Efficient Editing of the Nuclear APT Reporter Gene in Chlamydomonas reinhardtii via Expression of a CRISPR-Cas9 Module.

The clustered regularly interspaced short palindromic repeat/CRISPR-associated protein 9 (CRISPR/Cas9) technology is a versatile and useful tool to perform genome editing in different organisms ranging from bacteria and yeast to plants and mammalian cells. For a couple of years, it was believed that the system was inefficient and toxic in the alga Chlamydomonas reinhardtii. However, recently the system has been successfully implemented in this model organism, albeit relying mostly on the electroporation of ribonucleoproteins (RNPs) into cell wall deficient strains. This requires a constant source of RNPs and limits the application of the technology to strains that are not necessarily the most relevant from a biotechnological point of view. Here, we show that transient expression of the Streptococcus pyogenes Cas9 gene and sgRNAs, targeted to the single-copy nuclear apt9 gene, encoding an adenine phosphoribosyl transferase (APT), results in efficient disruption at the expected locus. Introduction of indels to the apt9 locus results in cell insensitivity to the otherwise toxic compound 2-fluoroadenine (2-FA). We have used agitation with glass beads and particle bombardment to introduce the plasmids carrying the coding sequences for Cas9 and the sgRNAs in a cell-walled strain of C. reinhardtii (CC-125). Using sgRNAs targeting exons 1 and 3 of apt9, we obtained disruption efficiencies of 3 and 30% on preselected 2-FA resistant colonies, respectively. Our results show that transient expression of Cas9 and a sgRNA can be used for editing of the nuclear genome inexpensively and at high efficiency. Targeting of the APT gene could potentially be used as a pre-selection marker for multiplexed editing or disruption of genes of interest.

High-Throughput Reaction Screening with Nanomoles of Solid Reagents Coated on Glass Beads.

Technologies that enable rapid screening of diverse reaction conditions are of critical importance to methodology development and reaction optimization, especially when molecules of high complexity and scarcity are involved. The lack of a general solid dispensing method for chemical reagents on micro- and nanomole scale prevents the full utilization of reaction screening technologies. We herein report the development of a technology in which glass beads coated with solid chemical reagents (ChemBeads) enable the delivery of nanomole quantities of solid chemical reagents efficiently. By exploring the concept of preferred screening sets, the flexibility and generality of this technology for high-throughput reaction screening was validated.

[Improvement of Fat Suppressing Effect for Finger and Neck MRI by Using Small Glass Beads].

The defectiveness of the fat suppression becomes the factor of the decrease of the quality of the diagnosis of magnetic resonance imaging. It is reported that the use of magnetic field uniformity adjuvant pad is effective for reduce poor fat suppression. The ball bullets, polystyrene balls, and polished rice are used for pad packing material, in recently, it was reported that fat suppression effect was good by the use of the small glass beads. Therefore, we tested the utility of small glass beads pad in the neck and fingers in this study. Neck and the fingers of subjects were imaged with T1-weighted image with fat suppression and T1-high resolution isotropic volume excitation image. The fat suppression effect of each image was compared with the polished rice and glass beads as material of pad used by physical, observation, and contact evaluation. In the result, satisfactory results were obtained by using glass beads, and it is suggested that fat suppression effect is improved by using glass beads as a filling material of pad in clinical study as a conclusion.

Development of the rectal dosage form with silver-coated glass beads for local-action applications in lower sections of the gastrointestinal tract.

CONTEXT: Recent findings indicating the anti-inflammatory action of silver preparations through modulation of the gut microbiota and apoptosis of inflammatory cells predestine silver use in inflammatory bowel disease (IBD). OBJECTIVE: The aim of our study was to validate the possibility of effective silver release from silver-coated glass beads for anti-inflammatory local application in the lower sections of the gastrointestinal (GI) tract. MATERIALS AND METHODS: Silver-coated glass beads were prepared using magnetron method. Release of silver from the silver-coated glass bead surface was carried out in BIO-DIS reciprocating cylinder apparatus. Erosion of silver coating and indirect estimation of the silver release dynamics was assessed using scanning electron microscope. Rectal suppositories containing silver-coated glass beads were prepared using five different methods (M1-M5) and X-ray scanned for their composition. RESULTS AND DISCUSSION: The XR microanalysis and the chemical composition analysis evidenced for a rapid (within 30 min) release of nearly 50% of silver from the coating of the glass beads, which remained stable up to 24 h of incubation. The most homogeneous distribution of beads in the entire volume of the suppository was obtained for formulation M5, where the molten base was poured into mold placed in an ice bath, and the beads were added after 10 s. CONCLUSIONS: Our study is the first to present the concept of enclosing silver-coated glass beads in the lipophilic suppository base to attenuate inflammation in the lower GI tract and promises efficient treatment with reduced side effects.

A Cheap and Convenient Method of Liposome Preparation Using Glass Beads as a Source of Shear Force.

Liposomes, the biocompatible lipid bilayer vesicles, have attracted immense attention due to their distinctive features such as efficient vehicle for the delivery of a wide range of therapeutic agents, adjustable formulation properties, and high drug entrapment efficiency. In this contribution, we present a simple method for the preparation of liposomes using glass beads and compared the potential of this method with conventional methods of liposome preparation. The prepared liposomes were characterized by different analytical techniques (HPLC, DLS, TEM, differential scanning calorimetry, and in vitro drug release). Our findings revealed that the particle size of liposomes is mainly dependent on the size of the glass beads and the glass bead shearing time. An average liposome size of 67.7 ± 25.5 nm was obtained using 2-mm glass beads after 24-h incubation at 200 rpm. The liposomes prepared under the optimized conditions exhibited a high encapsulation efficiency of 92.1 ± 1.7% with 31.08% drug release after 360 min at 37°C. In conclusion, the developed method is a simple and convenient process of liposome preparation of different sizes with desirable entrapment efficiency capacity.

Influence of surface characteristics of modified glass beads as model carriers in dry powder inhalers (DPIs) on the aerosolization performance.

The aim of this work is to investigate the effect of surface characteristics (surface roughness and specific surface area) of surface-modified glass beads as model carriers in dry powder inhalers (DPIs) on the aerosolization, and thus, the in vitro respirable fraction often referred to as fine particle fraction (FPF). By processing glass beads in a ball mill with different grinding materials (quartz and tungsten carbide) and varying grinding time (4 h and 8 h), and by plasma etching for 1 min, glass beads with different shades of surface roughness and increased surface area were prepared. Compared with untreated glass beads, the surface-modified rough glass beads show increased FPFs. The drug detachment from the modified glass beads is also more reproducible than from untreated glass beads indicated by lower standard deviations for the FPFs of the modified glass beads. Moreover, the FPF of the modified glass beads correlates with their surface characteristics. The higher the surface roughness and the higher the specific surface area of the glass beads the higher is the FPF. Thus, surface-modified glass beads make an ideal carrier for tailoring the performance of DPIs in the therapy of asthma and chronically obstructive pulmonary diseases.

Effect of particle density on microplastics transport in artificial and natural porous media.

The occurrence and persistence of microplastics (MPs) in natural environments are of increasing concern. Along with this, the transport of MPs in sediments has been investigated mainly focusing on the effect of plastic size and shape, media size effect, and solution chemistry. Yet, the influence of particle density is only partially understood. Therefore, column experiments on the transport of variably buoyant MPs in saturated natural sediments and glass beads were conducted, and transport parameters were quantified using a two-site kinetic transport model with a depth-dependent blocking function (the amount of retained MPs does not decrease at a constant rate with increasing depth, the majority of MPs were retained near the column inlet). Neutral, sinking, and buoyant MPs within the same size range were selected, with stable water isotope applied as conservative tracer to explore water and MP movement in the tested sediments. The results showed that 95.5 ± 1.4% of sinking MPs remained in columns packed with gravel, followed by buoyant and neutral MPs, thus indicating that particle density does affect MP mobility. Similar recovered amounts of MPs were found in columns packed with glass beads, indicating that tested sediment types do not affect the deposition behavior of MPs. The breakthrough curves of MPs were accurately described by the selected model. However, the simulated retention profiles overestimated the observed MP amount in layers closest to the column inlet. The coupled experimental and modeled results suggest an enhanced retention of sinking MPs, while neutrally and buoyant MPs exhibit a higher mobility in comparison. Thus, neutral or buoyant MPs can potentially pose a higher contamination risk to subsurface porous media environments compared to sinking MPs. Discrepancies between observed and simulated retention profiles indicate that future model development is needed for advancing the MP deposition as affected by particle density.

Contamination of consumer composts by metals, microplastics and other microscopic debris.

Very little information exists on the particle and chemical contamination of consumer (horticultural) composts. In this study, anthropogenic microcellulosics (AMCs), microplastics (MPs) and other microscopic debris, along with anthropogenically impacted metals (Cu, Zn, Pb), have been determined in 12 composts (seven garden composts and five growbags) purchased at outlets in the UK. AMCs and MPs, determined microscopically, were present in all samples at up to about 1100 kg-1 dw. AMCs were more abundant and were dominated by fibres constructed of rayon and cotton, while petroleum-based MPs exhibited a greater diversity in shape and polymeric construction (including polyolefins, polyethylene terephthalate, polyvinyl chloride, resins, paints and rubbers). Other microdebris, present in much smaller concentrations in the composts, consisted of fragments of glass, metal and machined wood and spherical glass beads. Concentrations of the anthropogenically impacted metals, Cu, Pb and Zn, determined directly by energy-dispersive X-ray fluorescence spectrometry, were heterogeneously distributed and averaged 52.4, 192 and 51.6 mg kg-1 dw, respectively. Although concentrations of anthropogenic particles were not related to cost or type of compost, physico-chemical properties or metal concentrations, a significant relationship between Pb content and particle diversity (number of polymers and debris types) was established. This relationship might result from the general contamination of the environment by both Pb and anthropogenic particulates, or the association of the metal with various types of material (e.g. paints, polyvinyl chloride, glass). Despite the ubiquity and diversity of MPs and microdebris in consumer composts, an understanding of their impacts on plant growth, either directly or indirectly (e.g. by interacting with metals), is unknown.

Nanobubble transport in porous media: Towards agro- and environmental applications.

Nanobubbles have been increasingly used in various applications involving porous media, such as groundwater remediation and irrigation. However, the fundamental scientific knowledge regarding the interactions between nanobubbles and the media is still limited. The interactions can be repulsive, attractive, or inert, and can involve reversible or irreversible attachment as well as destructive mechanisms. Specifically, the stability and mobility of nanobubbles in porous media is expected to be dependent on the dynamic conditions and the physicochemical properties of the porous media, solutions, and nanobubbles themselves. In this study, we investigated how changes in solution chemistry (pH, ionic strength, and valence) and media characteristics (size and wettability) affect the size and concentration of nanobubbles under dynamic conditions using column experiments. Quartz crystal microbalance with dissipation monitoring provided a deeper understanding of irreversible and elastic nanobubbles' interactions with silica-coated surfaces. Our findings suggest that nanobubbles are less mobile in solutions of higher ionic strength and valence, acidic pH and smaller porous media sizes, while the wettability of porous media has a negligible influence on the retention of nanobubbles. Overall, our findings provide insights into the underlying mechanisms of nanobubble interactions and suggest potential strategies to optimize their delivery in various applications.

Utilization of Silica Filler as Reinforcement Material of Polylactic Acid (PLA) in 3D Printing Applications: Thermal, Rheological, and Mechanical Performance.

Glass was introduced as an additive to filaments used for the manufacturing of composite materials, employed by Additive Manufacturing applications. Glass accounts for a large waste electric and electronic equipment (WEEE) percentage, and its recovery and recycling can lead to the production of sustainable composite materials. In this work, poly(lactic acid) (PLA)/commercially available silicon oxide composite filaments were manufactured and their structural, thermal, rheological, and mechanical properties were assessed. Scanning Electron Microscopy confirmed the 1:2 ratio of silicon: oxygen, along with the relatively low adhesion between the filler and the matrix. Differential Scanning Calorimetry presented steady glass transition and melting temperatures of composites, whereas a crystallization temperature of 10% wt. and a crystallinity of 15% wt. composite slightly increased. Rheological analysis showcased that the viscosity of the composite filaments decreased compared to PLA (10-100 compared to 300-400 Pa·s), with a more shear-thinning behavior. Dynamic mechanical analysis exhibited increased elastic, flexural moduli, and flexural strength of composites (up to 16, 23, and 11%, respectively), whereas tensile strength and elongation decreased. The affordability of raw materials (with the future introduction of recycled ones) and the minimal processing steps can lead to the potential scaling up of the study.

Redox condition changes caused by impacts: Insights from Chang'e-5 lunar glass beads.

Lunar materials are overall more reducing compared with their terrestrial counterparts, but the mechanism remains to be elucidated. In this study, we present a possible explanation for the changes in redox state of the lunar regolith caused by impact events, based on our investigations of the impact glass beads from Chang'e-5 mission. These glass beads contain iron metal grains and show concentration gradients of FeO and K2O (with or without Na2O) from their rims to centers. The compositional profiles exhibit error-function-like shapes, which indicates a diffusion-limited mechanism. Our numerical modeling results suggest that the iron metal grains on the surface of the glass beads were generated through the reduction of FeO by elemental K and (or) Na produced during the impact events. Meanwhile, the iron metal grains inside the bead may have formed due to oxygen diffusion driven by redox potential gradients. Furthermore, our study suggests that impact processes intensify the local reducing conditions, as evidenced by the presence of calcium sulfide particles within troilite grains that coexist with iron metal grains on the surface of the glass beads. This study provides insights into the oxygen diffusion kinetics during the formation of iron metal spherules and sheds light on the changes in redox conditions of lunar materials caused by impact events.

The Effect of Mechanical Alteration on Repair Bond Strength of S-PRG-Filler-Based Resin Composite Materials.

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 (p < 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.