Evaluation of Antimicrobial Activity of A Fast-Setting Bioceramic Endodontic Material

Background: To evaluate the antimicrobial activity of the fast-setting bioceramic iRoot Fast Set Root Repair Material (iRoot FS) and two other calcium silicate cements. Methods: The antimicrobial activity of iRoot FS, ProRoot MTA and Biodentine against E. faecalis and P. gingivalis were evaluated in this study. The materials were freshly mixed or set for 1 and 7 days on 5mm diameter sterile filter papers. The agar diffusion test, direct contact test and carry-over effect test were conducted, and the pH values (using a digital pH meter) were also evaluated. The data were analyzed by an analysis of variance and two-way ANOVA (α=0.05).Results: In the agar diffusion experiment, no obvious inhibition zone was observed for iRoot FS, ProRootMTA or Biodentine at any time interval. In the direct contact test, all three materials showed good antibacterial activity after setting for 20 minutes. The antibacterial properties of the three materials decreased with the increase of setting time. None of the three materials showed carry-over antibacterial effect. The pH measurement showed that the suspension of all the three materials showed high pH values (11-12). With the extension of setting time, the pH of iRoot FS and Biodentine slightly decreased.Conclusions: Fresh iRoot FS, Biodentine, and MTA killed E. faecalis and P. gingivalis effectively, and the antimicrobial effect of all the three materials decreased over 1 and 7 days after mixing. All three materials showed a tendency of alkalinity which last for at least 7 days after setting.

Antimicrobial and cytotoxic capacity of pyroligneous extracts films of Eucalyptus grandis and chitosan for oral applications

Chitosan films containing distilled pyroligneous extracts of Eucalyptus grandis (DPEC), characterized and developed by Brazilian Agricultural Research Corporation—Embrapa Temperate Agriculture (EMBRAPA-CPACT), were evaluated for antimicrobial activity against Candida albicans, Streptococcus mutans, and Lactobacillus acidophilus by direct contact test. Further, their capacity for the prevention of teeth enamel demineralization and cytotoxicity in vitro were also determined. The natural polymers were tested at different concentrations (1500–7500 µg mL−1) and the formulation of an experimental fluoride varnish with antimicrobial activity was evaluated by direct contact test, whereas cytotoxicity was analyzed through the colorimetric MTT assay. Preliminary data showed no statistically significant differences in cytotoxicity to NIH/3T3 cell line when DPEC is compared to the control group. On the other hand, the antimicrobial capacity and demineralization effects were found between the test groups at the different concentrations tested. Chitosan films containing distilled pyroligneous extracts of E. grandis may be an effective control strategy to prevent biofilm formation related to dental caries when applied as a protective varnish. They may inhibit the colonization of oral microorganisms and possibly control dental caries through a decrease in pH and impairment of enamel demineralization.

Evaluation of Heartwood Extracts Combined with Linseed Oil as Wood Preservatives in Field Tests in Southern Mississippi, USA

Heartwood extracts of naturally durable wood species are often evaluated as alternatives to chemical wood preservatives, but field data from long-term performance testing are lacking. The current study evaluated the long-term (five-year) performance of two non-durable wood species treated with heartwood extracts of either Tectona grandis, Dalbergia sissoo, Cedrus deodara, or Pinus roxburghii alone or combined with linseed oil. Stakes (45.7 × 1.9 × 1.9 cm) and blocks (12.5 × 3.75 × 2.5 cm) cut from the sapwood of cottonwood and southern pine were vacuum-pressure impregnated with the individual heartwood species extract, linseed oil, or a mixture of each individual wood extract and linseed oil. For comparison, solid heartwood stakes and blocks of the wood species used to obtain extracts were also included in the tests. All samples were exposed for five years to decay and termites at a test site in southern Mississippi using ground contact (AWPA E7) and ground proximity (AWPA E26) tests. Results showed that extract-oil mixtures imparted higher termite and decay resistance in cottonwood and southern pine than linseed oil only or the individual heartwood species extract in both tests. However, these treatments were as not effective as to commercially used wood preservatives, copper naphthenate (CuN) or disodium octaborate tetrahydrate (DOT) in either test. Moreover, solid heartwood P. roxburghii stakes were completely decayed and attacked by termites after five years in the ground contact test. In contrast, C. deodara stakes were slightly attacked by termites and moderately attacked by decay fungi. However, T. grandis and D. sissoo stakes showed slight to superficial attack by termites and decay fungi in ground contact test. In contrast, T. grandis and D. sissoo blocks showed slight decay fungi attack in above-ground tests. However, termites did not attack T. grandis, D. sissoo, and C. deodara blocks. However, decay fungi moderately attacked C. deodara blocks, and P. roxburghii blocks were severely attacked by decay fungi and termites in the above-ground test.

Experimental Study of Effects of the Third Medium on the Maximum Friction Coefficient between Wheel and Rail for High-Speed Trains

The changes of the friction coefficient between wheel and rail affect the wheel-rail adhesion characteristics of high-speed trains. The adhesion state in the wheel-rail contact area could be distinguished by the maximum friction coefficient between wheel and rail. The wheel-rail adhesion is of great significance for high-speed train traction. In order to study the influence of water, oil, fallen leaves, quartz sand, or their mixtures on the maximum friction coefficient between high-speed wheel and rail, a wheel-rail contact test bed is built to carry out the wheel-rail contact test and wheel-rail friction contact test. The comparative analysis of the test results shows that the axle load has little influence on the maximum friction coefficient between wheel and rail. Water, oil, and fallen leaves would reduce the maximum friction coefficient. Quartz sand could increase the maximum friction coefficient in a short time, while the excessive static friction coefficient would damage the wheel and rail. Besides, the maximum friction coefficient of water, oil, and fallen leaves mixing in pairs is lower than each of them existing alone. Both water and oil could increase the adhesion of quartz sand, and the effect of water is better. Therefore, when the sand still could not meet enough traction, it could be considered to add some water to increase the wheel-rail adhesion.

Low-temperature flow-synthesis-assisted urethane-grafted zinc oxide-based dental composites: physical, mechanical, and antibacterial responses

A novel way was adopted to graft zinc oxide (ZnO) with urethane-modified dimethacrylate (UDMA) in order to utilize them as reinforcing agents in resin-based dental composites. Experimental novel composites were synthesized having UDMA-grafted and nongrafted ZnO, at a concentration of 0 wt.%, 5 wt.%, and 10 wt.%. The same concentrations of ZnO were also incorporated in Filtek Z250 XT (3 M ESPE, USA). The antibacterial behavior was evaluated against Streptococcus mutans by direct-contact test at one, three, and seven days of incubation. The compressive strength and Vickers microhardness were tested as per ISO 9917 and ISO/CD6507-1, respectively. For abrasive wear resistance, mass loss and roughness average after tooth-brushing cycles of 24,000 at custom-made tooth-brushing simulator were evaluated using noncontact profilometer. Data analysis was carried out using post hoc Tucky’s test and nonparametric Kruskal–Wallis test. Direct contact test revealed that the antibacterial potential of novel and commercial composites was increased with an increase in the concentration of grafted ZnO as compared with nongrafted, whereby the potential was the highest at day seven. There was a significant decrease in compressive strength and Vickers hardness of commercial composites on addition of grafted ZnO while there was no significant difference in the strength of experimental novel composite. The abrasive wear of commercial and experimental composites was within clinical limits. Low-temperature flow-synthesis method was successfully employed to synthesize grafted and nongrafted ZnO. The UDMA-grafted ZnO can be incorporated into dental composites without decreasing their strength and these composites can be used to combat secondary caries.

Investigative study into whether an insect repellent has virucidal activity against SARS-CoV-2

A small-scale study with Mosi-guard Natural spray, an insect repellent containing Citriodiol, was performed to determine if it has virucidal activity against SARS-CoV-2. A liquid test examined the activity of the insect repellent and the individual components for virucidal activity. A surface contact test looked at the activity of the insect repellent when impregnated on a latex surface as a synthetic skin for potential topical prophylactic application. Both Mosi-guard Natural spray and Citriodiol, as well as other components of the repellent, had virucidal activity in the liquid contact test. On a latex surface used to simulate treated skin, the titre of SARS-CoV-2 was less over time on the Mosi-guard Natural-treated surface but virus was still recovered.

Ecotoxicity testing of airborne particulate matter—comparison of sample preparation techniques for the Vibrio fischeri assay

The bioassay based on the bioluminescence inhibition of the marine bacterium Vibrio fischeri has been the most widely used test for the assessment of airborne particulate matter ecotoxicity. Most studies available use an extract of the solid sample, either made with water or organic solvents. As an alternative, a whole-aerosol test is also available where test bacteria are in actual contact with contaminated particles. In our study, different extraction procedures were compared to this direct contact test based on the V. fischeri assay and analytical measurements. The lowest PAH content and the highest EC50 were determined in water extract, while the highest PAH amount and lowest EC50 were measured in dichloromethane, hexane, and dimethyl-sulphoxide extracts. EC50 of the direct contact test was comparable to that of the methanol extract. Our results suggest that the sensitivity of the direct contact test equals to that of extraction procedures using organic solvents, moreover, it is mimicking an environmentally realistic exposure route.

Paleomagnetism of the ~860 Ma Manso dyke swarm, West Africa: implications for the assembly of Rodinia

<p>The West African Craton (WAC) is one of the major cratons in the Rodinia jigsaw puzzle (~1000–750 Ma). In the Rodinian models, the position of West Africa is mainly constrained by the assumption that it had been a partner of Amazonia since the Paleoproterozoic. Unfortunately, no paleomagnetic data are available for these cratons when the Rodina supercontinent is considered tectonically stable (~1000-750 Ma). Thus, every new reliable paleomagnetic pole for the West African Craton during the Neoproterozoic times is of paramount importance to constrain its position and testing the Rodinia models. In this study we present a combined paleomagnetic and geochronological investigation for the Manso dyke swarm in the Leo-Man Shield, southern West Africa (Ghana). The ~860 Ma emplacement age for the NNW-trending Manso dykes is thus well-constrained by two new U-Pb apatite ages of 857.2 ± 8.5 Ma and 855 ± 16 Ma, in agreement with baddeleyite data. Remanence of these coarse-to-fine grained dolerite dykes is carried by stable single to pseudo-single domain (SD-PSD) magnetite. A positive baked-contact test, associated to a positive reversal test (Class-C), support the primary remanence obtained for these dykes (13 sites). Moreover, our new paleomagnetic dataset satisfy all the seven R-criteria (R=7). The ~860 Ma Manso pole can thus be considered as the first key Tonian paleomagnetic pole for West Africa. We propose that the West Africa-Baltica-Amazonia-Congo-São Francisco were associated in a long-lived WABAMGO juxtaposition (~1100–800 Ma).</p><p><strong>Keywords:</strong> West Africa, Neoproterozoic, Tonian, Rodinia, paleomagnetism.</p><p> </p>

Leachate and contact test with Lepidium sativum L. to assess the phytotoxicity of waste

The study evaluated the use of Lepidium sativum L. to assess the phytotoxicity of three types of waste such as hazardous waste (slags from zinc to copper smelters) and nonhazardous waste (mineral–organic composite). Previous studies evaluated heavy metal leaching and the environmental impact of the tested waste. The purpose of phytotoxicity studies was to increase knowledge about this waste. Two types of tests were used to assess the phytotoxicity of wastes: germination index and accumulation test. Both tests were carried out for leachate (leachate test) and waste (contact test). The results of both tests were compared to assess the phytotoxic effects of tested waste. Phytotoxicity tests have shown that the mineral–organic composite leachate was stimulated plant growth, copper smelter slag leachate was characterized by no phytotoxicity and zinc slag leachate inhibited the growth of plants. In contrast, contact test showed inhibitory effects from all tested waste. Wherefore, the contact test was indicated as more sensitive in the assessment of phytotoxicity. However, this is not a clear assessment, because the germination index values for both tests were a result of differences of root length for both control samples (deionized water and sand). The study confirmed the usefulness of L. sativum for the assessment of phytotoxicity of various types of waste. Additionally, it was found that L. sativum was resistant to high concentrations of heavy metals in the leachate, without causing any negative physiological effects.