Airborne particles and microorganisms in a dental clinic: Variability of indoor concentrations,impact of dental procedures,and personal exposure during everyday practice

This study presents for the first time comprehensive measurements of the particle number size distribution (10 nm to 10 μm) together with next-generation sequencing analysis of airborne bacteria inside a dental clinic. A substantial enrichment of the indoor environment with new particles in all size classes was identified by both activities to background and indoor/outdoor (I/O) ratios. Grinding and drilling were the principal dental activities to produce new particles in the air, closely followed by polishing. Illumina MiSeq sequencing of 16S rRNA of bioaerosol collected indoors revealed the presence of 86 bacterial genera, 26 of them previously characterized as potential human pathogens. Bacterial species richness and concentration determined both by qPCR, and culture-dependent analysis were significantly higher in the treatment room. Bacterial load of the treatment room impacted in the nearby waiting room where no dental procedures took place. I/O ratio of bacterial concentration in the treatment room followed the fluctuation of I/O ratio of airborne particles in the biology-relevant size classes of 1–2.5, 2.5–5, and 5–10 μm. Exposure analysis revealed increased inhaled number of particles and microorganisms during dental procedures. These findings provide a detailed insight on airborne particles of both biotic and abiotic origin in a dental clinic.     

Electrochemical Methods for Lithium Recovery: A Comprehensive and Critical Review

Due to the ubiquitous presence of lithium-ion batteries in portable applications, and their implementation in the transportation and large-scale energy sectors, the future cost and availability of lithium is currently under debate. Lithium demand is expected to grow in the near future, up to 900 ktons per year in 2025. Lithium utilization would depend on a strong increase in production. However, the currently most extended lithium extraction method, the lime-soda evaporation process, requires a period of time in the range of 1–2 years and depends on weather conditions. The actual global production of lithium by this technology will soon be far exceeded by market demand. Alternative production methods have recently attracted great attention. Among them, electrochemical lithium recovery, based on electrochemical ion-pumping technology, offers higher capacity production, it does not require the use of chemicals for the regeneration of the materials, reduces the consumption of water and the production of chemical wastes, and allows the production rate to be controlled, attending to the market demand. Here, this technology is analyzed with a special focus on the methodology, materials employed, and reactor designs. The state-of-the-art is reevaluated from a critical perspective and the viability of the different proposed methodologies analyzed.     

Effect of the addition mechanism of ZnO sintering aid on densification,microstructure and electrical properties of Ba(Zr,Y)O3-δ proton-conducting perovskite

We explore three different potential mechanisms to introduce 4 mol% ZnO sintering additive to the promising yttrium-doped barium zirconate (Ba(Zr,Y)O_3-δ, BZY) proton conductor. The mechanisms involve Zn substitution for Y, Zr, or B-site cation excess. The addition of ZnO promotes high densification levels (up to 98% of the theoretical value) at 1300 °C, irrespective of the mechanism. However, scanning electron microscopy shows that the B-site cation excess mechanism leads to an impaired grain growth compared to the other mechanisms. Rietveld refinement of the lattice-parameters and scanning transmission electron microscopy-energy dispersive X-ray spectroscopy indicates that Zn resides in both grains and grain boundaries in all cases. Determination of partial conductivities demonstrates that the Zr substitution mechanism provides slightly higher values of bulk protonic conductivity, as well as a higher hydration enthalpy. In contrast, the B-site excess mechanism provides the highest specific grain-boundary conductivity, as a result of greater Zn segregation to the grain boundary.     

Tuning the antimicrobial activity of collagen biomaterials through a liposomal approach

The development of advanced biocidal agents stands as a global challenge, focused on the increasing demand of new biomaterials with local and gradual release of antimicrobial agents. This is the first time that three well-known materials are strategically combined to develop a novel biomaterial with long-term bactericidal activity that avoids burst release and toxic effects, by the incorporation of silver nanoparticles in liposomes and the subsequent incorporation of these assemblies in collagen hydrogels. These systems show improved mechanical properties and prolonged inhibitory effect on the growth of Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa) bacteria, while remaining highly biocompatible for epithelial cells. In fact, the hybrid biocomposite prevents bacterial colonization for at least 72 h, allowing at the same time eukaryotic cell proliferation. As a result, this new bactericidal biomaterial provides a new alternative to improve current treatments of bacterial infections with many implications in significant applications, such as wound therapy and tissue regeneration.     

A Role for Human DNA Polymerase λ in Alternative Lengthening of Telomeres

Telomerase negative cancer cell types use the Alternative Lengthening of Telomeres (ALT) pathway to elongate telomeres ends. Here, we show that silencing human DNA polymerase (Pol λ) in ALT cells represses ALT activity and induces telomeric stress. In addition, replication stress in the absence of Pol λ, strongly affects the survival of ALT cells. In vitro, Pol λ can promote annealing of even a single G-rich telomeric repeat to its complementary strand and use it to prime DNA synthesis. The noncoding telomeric repeat containing RNA TERRA and replication protein A negatively regulate this activity, while the Protection of Telomeres protein 1 (POT1)/TPP1 heterodimer stimulates Pol λ. Pol λ associates with telomeres and colocalizes with TPP1 in cells. In summary, our data suggest a role of Pol λ in the maintenance of telomeres by the ALT mechanism.     

Anthropometric measurements among four Asian countries in designing sitting and standing workstations

An anthropometric database for sitting and standing dimensions for Malaysian operators was developed based on the measurements from 146 male and 168 female participants (18–45 years old). The anthropometric data were subsequently compared to those from three selected Asian countries, focussing on the sitting and standing posture dimensions. Thirty-six anthropometric dimensions were selected for comparison based on common availability among the four countries. The results indicated that the Indonesians were the tallest (male: 172 cm, female: 159 cm) among the four countries, whereas the Filipinos were the shortest for both male and female (male: 167 cm, female: 153.9 cm). Filipinos and Malaysian data were almost similar and appear to have the smallest values for eye height (male: 155 cm, female: 143 cm) and elbow height (male: 104 cm, female: 96 cm). The knowledge of variations in the population is useful in designing sound workstations and facilities for the betterment of the industrial environment.     

Wetting of SiC by Al-Ti alloys and joining by in-situ formation of interfacial Ti3Si(Al)C2

Two pressureless and reliable procedures for brazing SiC-based materials have been designed. The joining was obtained by the in-situ formation of a Ti₃Si(Al)C₂ MAX phase using simple Al-Ti interlayers. Wettability studies were conducted using several Al-Ti alloys in contact with SiC at 1500?°C. The interfacial microstructures and thermodynamic analysis demonstrated that liquid Al₃Ti in contact with SiC formed a well-bonded Ti₃Si(Al)C₂ interfacial layer. These findings guided the design of two joining methods: one consisted of the simple infiltration of Al₃Ti into the brazing seam, while an Al₃Ti paste/Ti/Al₃Ti paste interlayer assembly was designed for the second process. Sound interfaces without cracks were obtained in both processes. The average shear strength was very high, 296?MPa, for the infiltration method; the drawback was the presence of residual Al. Joining through Al₃Ti/Ti/Al₃Ti interlayers avoided the presence of low-temperature melting phases, with lower shear strength: 85 or 89?MPa depending on the testing method.     

Solubility parameter of oils by several models and experimental oil compatibility data: implications for asphaltene stability

In a previous study we obtained reference values of solubility parameter of two Brazilian crude oils based on asphaltene flocculation data. In this work, these reference values were compared to those obtained by nine models available in the literature and oil compatibility data were experimentally obtained to enhance the modeling evaluation. These evaluations allowed to select models to predict asphaltene stability and oil compatibility. As a result, only our method along with three other methods can accurately predict the experimental results of the compatibility between oil mixtures, and the conclusion is that usually recommended models are not the best choice.