Search Results (10)

This study evaluated the pH, fluoride (F), and calcium (Ca) concentrations in saliva-derived microcosm biofilms following treatments with dentifrices applied at different amounts and F concentration. Human saliva was inoculated into McBain culture medium, and treatments were applied at 72/78/96 h (1 min). Fluoridated dentifrices containing 550 or 1100 ppm F (550F and 1100F, respectively) were used at the following combinations (intensities): (i-1) 550F/0.08 g or 1100F/0.04 g; (i-2) 550F/0.16 g or 1100F/0.08 g; (i-3) 550F/0.32 g or 1100F/0.16 g. A negative control (fluoride-free dentifrice—PLA) was also included. Biofilm F and Ca were measured with an ion-selective electrode and colorimetrically, respectively, while pH in the culture medium was measured with a pH electrode. Data were subjected to ANOVA and Student–Newman–Keuls’ test (p < 0.05). F-dentifrices did not significantly alter pH compared to PLA, except for 1100F at i-3. Biofilm F levels at i-1 and i-2 were comparable, for both 550F and 1100F, while 1100F at i-3 led to the highest biofilm F concentration. All F-groups showed significantly higher Ca levels than PLA, especially at i-2 and i-3. In conclusion, the interplay between dentifrice amount and F concentration was more influential on the biofilm’s inorganic composition and pH than either variable alone. Full article

The direct energy deposition (DED) metal additive manufacturing process enables rapid deposition and repair, providing an efficient approach to producing durable tool steel components. Here, 5 wt% Cr cold-work tool steel (Caldie) was developed by reducing carbon and chromium to suppress coarse carbide formation and by increasing molybdenum and vanadium to enhance dimensional stability. In this study, Caldie tool steel was fabricated via DED for the first time, and the effects of post-heat treatment on its hierarchical microstructure and mechanical properties were investigated and compared with those of wrought (reference) material. The as-built sample exhibited a mixed microstructure comprising lath martensite, retained austenite, polygonal ferrite, and carbide networks, which transformed into full martensite with fine carbides after heat treatment (DED-HT). The tensile strength of the DED Caldie material increased from 1340 MPa to 1949 MPa after heat treatment, demonstrating superior strength compared to other heat-treated, DED-processed high-carbon tool steels. Compared to DED-HT, the wrought material exhibited finer martensite, a more uniform Bain group distribution, and finer carbides, resulting in higher strength. This study provides insights into the effects of heat treatment on the hierarchical microstructure and mechanical behavior of Caldie tool steel manufactured by DED. Full article

Understanding the factors influencing the variability in the composition of fish assemblages is essential for bolstering the resilience of coral reef ecosystems, effective coral reef management and maintaining sustainable fisheries. The benthic composition and reef fish assemblages at eight sites at the poorly studied St. Brandon, also known as a bank fisheries area in the Indian Ocean, were assessed to discern distribution patterns, including differences between channel (Passe Grand Capitaine, Passe Ile Longue-Canal Coco and Passe La Cayane) and non-channel (Chaloupe, Anchor Points 1 and 2, Bain des Dames, Pearl Island) sites and fisheries sustainability. The benthic composition exhibited clusters, revealing the distinct separation of Chaloupe which predominantly featured sand (75.26%) interspersed with sporadic coral patches characterized by live and dead corals and rubble. The three channel sites composed a cluster. Coral species across eight families were identified, with significant variability (p < 0.05) observed in their benthic cover, particularly live coral cover (LCC). Fish density and diversity analyses unveiled 58 fish species from 12 families, with no statistically significant disparity in density among sites. Total fish biomass (TFB) and target fish biomass (TB) ranged from 138.02 ± 65.04 to 4110.16 ± 3048.70 kg/ha and from 28.31 ± 24.52 to 3851.27 ± 2753.18 kg/ha, respectively. TFB and TB differed significantly (p < 0.05) among sites irrespective of channel and non-channel sites, with Pearl Island recording the highest biomass. TFB and TB recorded at five out of the eight surveyed sites exceeded the mean biomass benchmark (B₀) for the Western Indian Ocean, set at 1150.00 and 560.00 kg/ha for TFB and TB, respectively. Functional group analysis unveiled six discrete groups influencing TFB, with scrapers being the most dominant. This study presents the first report on fish biomass surveys in St. Brandon, highlighting a case for sustainable fisheries in the waters of the Republic of Mauritius. Full article

The aim of this study was to evaluate the effect of the Cymbopogon citratus essential oil and its association with chlorhexidine on cariogenic microcosm biofilm composition and acidogenicity. Minimum inhibitory and bactericide concentrations from the essential oil and chlorhexidine were determined by broth microdilution assay. Microcosms (polymicrobial) biofilms were produced on glass coverslips, using inoculum from human saliva in McBain culture medium (0.5% sucrose exposure for 6 h/day) for 3 days in 24-well plates. The biofilms were treated twice a day and their composition was evaluated by microorganism quantification. The acidogenicity was evaluated by measuring the pH of the spent culture medium in contact with the biofilm. Overall, the association of C. citratus and chlorhexidine reduced total bacterial counts and aciduric bacteria (maximum reduction of 3.55 log UFC/mL) in microcosm biofilms. This group also presented the lowest acidogenicity even when exposed to sucrose-containing medium. C. citratus essential oil increases the effect of digluconate chlorhexidine on microcosm biofilms. Based on these findings, this study can contribute to the development of new formulations that might allow for the use of mouthwashes for a shorter period, which may reduce undesirable effects and increase patient compliance to the treatment. Full article

Tailoring martensite transformation is critical for improving the mechanical properties of advanced steels. To provide preliminary guidance for the control of martensite transformation behaviour using external fields by computational simulation method, the phase-field method was used to calculate the morphology evolution, kinetics, and variant selection of the martensite transformation under different loading modes and magnetic field intensities. The incubation, transformation, and stable stages of the three variants based on the Bain strain group were investigated using different kinetic curves. These results clearly indicate that both uniaxial tension and compression can greatly promote the formation of martensite during the transformation stage and cause an obvious preferred variant selection. In contrast, the different variants have relatively balanced forms under shearing conditions. In addition, the magnetic field is a gentler way to form a state with balanced variants than other techniques such as shearing. Additionally, all these simulation results are consistent with classical martensitic transformation theory and thermodynamic mechanism, which proves the rationality of this research. The aim of the present study was to provide qualitative guidance for the selection of external fields for microstructural improvement in advanced steels. Full article

The aim of the study was to assess the post-harvest life of the leaves of Hemerocallis × hybrida ‘Agata’, Limonium latifolium, and Heuchera hybrida ‘Chocolate Ruffles’ after the application of growth regulators from the group of gibberellins (GAs) and cytokinins (CKs), ionic liquids (2-hydroxyethyl)dimethylethylammonium gibberellinate [Chol][Gib] and acetylcholine gibberellinate [Gib][Ach]), as well as quaternary ammonium salts with the gibberellinate anion (1-ethyl quinine gibberellinate [Q-C₂][Gib]) and 1-dodecyl acetylcholine gibberellinate [Q-C₁₂][Gib]). The leaves were conditioned for 4 h in aqueous solutions of benzyladenine (BA), meta-methoxytopolin (MemT) and its riboside (MemTR), gibberellic acid (GA₃), [Q-C₂][Gib], [Gib][Ach], [Chol][Gib], and [Q-C₁₂][Gib] at concentrations of 50 and 100 mg·dm⁻³. Conditioning of Hemerocallis × hybrida ‘Agata’ with MemT and [Chol][Gib] at both concentrations, [Q-C₂][Gib] (100 mg·dm⁻³) and [Gib][Ach] (50 mg·dm⁻³), extended the vase life of the leaves by 7–9 days. The application of [Gib][Ach] (50 and 100 mg·dm⁻³) and [Q-C₁₂][Gib] (100 mg·dm⁻³) resulted in the longest vase life of the leaves of Limonium latifolium. Conditioning of the leaves of Heuchera hybrida ‘Chocolate Ruffles’ with BA, MemT, and MemTR (50 and 100 mg·dm⁻³) extended their vase life by 9.5–51.3 days. BA at a concentration of 100 mg·dm⁻³ was the most effective. MemT (50 mg·dm⁻³), MemTR (100 mg·dm⁻³), [Q-C₂][Gib] (100 mg·dm⁻³), [Gib][Ach] (100 mg·dm⁻³), and [Chol][Gib] (50 mg·dm⁻³) inhibited the degradation of proteins in the leaves of Hemerocallis × hybrida ‘Agata’; [Chol][Gib] (50 and 100 mg·dm⁻³)—in the leaves of Limonium latifolium; all the conditioners except for BA—in the leaves of Heuchera hybrida ‘Chocolate Ruffles’. GA₃, MemTR, [Gib][Ach], [Q-C₁₂][Gib] at both concentrations, [Q-C₂][Gib], and [Chol][Gib] (50 mg·dm⁻³) inhibited the degradation of chlorophyll in the leaves of Hemerocallis × hybrida ‘Agata’. All conditioners except for [Gib][Ach] and [Q-C₁₂][Gib] inhibited chlorophyll degradation in the leaves of Limonium latifolium. All conditioners except for MemT and MemTR (50 mg·dm⁻³) inhibited chlorophyll degradation in the leaves of Heuchera hybrida ‘Chocolate Ruffles’. [Chol][Gib] (50 mg·dm⁻³) was the most effective. Full article

Variant pairs have an indispensable function on mechanical properties such as low impact toughness. Therefore, it was assumed that they would also affect the HER (Hole Expansion Ratio, an indicator to evaluate stretch flanging performance). To clarify this, a comprehensive analysis of the common influential factors in an 800 MPa grade low carbon micro-alloyed steel, i.e., the retained austenite, the M/A (Martensite/Austenite) island, the titanium precipitations, the grain diameter, the density of high angle grain boundaries and the textures, was first conducted. It was found that they did not match well with the HER, suggesting that they were not the governing factor for HER in this steel. However, the dominating crystallography groups and the variant pairing results indicated that they fitted well with the HER. In the samples with high HERs, the CP (Close Packed) groups dominated the transformation, wherein one individual CP group consisted of two or more Bain groups, whereas it evolved into the domination of joint CP groups and Bain groups for the low HER sample. Further analysis on the variant pairing features indicated that a correlation occurred between the HER and the high angle variant pairs. In the steels with high HERs, high-angle variant pairs of V1/V2, V1/V3 that transformed from the same CP group, particularly of V1/V2 pair, were mostly generated. They turned to V1/V9, V1/V10, V1/V12, V1/V15, V1/V17, and V1/V18 pairs from differential CP groups, especially the V1/V12 and V1/V15 pair for low-HER steel. This result showed that V1/V2, V1/V12, and V1/V15 might have accounted most for the HER in this steel. The underlying reason was that the V1/V2 pair was specialized in supplying a slip passage for dislocation transmission across a grain boundary with little resistance, whereas the dislocation transmission ability for V1/V12 and V1/V15 pair was particularly poor. Thus, to efficiently enhance the HER, one should regulate the variant pairs by augmenting the V1/V2 fraction and suppressing the formation of the V1/V12 and V1/V15 pair. Full article

To estimate age at peak height velocity (APHV) in Portuguese male adolescents and; test the effect of maturational status in physical fitness attributes and individual game performance of U-14 basketball players. One mixed-longitudinal cohort with a sample of 439 Portuguese male adolescents and; one cross sectional sample of 172 Portuguese elite U-14 basketball players. The on-time group was defined within a 1-year band (more or less) from mean APHV. Preece-Baines model 1 was adopted to fit the mean stature curve. Independent samples t-tests and Kruskal-Wallis tests were performed and effect size (partial eta square) was calculated. The growth fitting revealed an APHV around 13.45 years for Portuguese male adolescents. Early maturing players exceeded significantly their peers in body size and composition, jump power and upper body strength. Early and on-time maturing players scored better in rebounds won per game (APHV = 13.81, 13.30 years), Performance Index Rating (PIR) and points scored per minute. Maturation influences morphology attributes and strength regardless of the APHV (13.81, 13.45, 13.30 years) used to obtain the cut-off points. It is recommended to use the new Portuguese mean APHV value to avoid extreme classifying bias groups. Full article

In this paper, we introduce a model representing the key characteristics of high frequency variations of solar irradiance and photovoltaic (PV) power production based on Clear Sky Index (CSI) data. The model is suitable for data-driven decision-making in electrical distribution grids, e.g., descriptive/predictive analyses, optimization, and numerical simulation. We concentrate on solar irradiance data since the power production of a PV system strongly correlates with solar irradiance at the site location. The solar irradiance is not constant due to the Earth’s orbit and irradiance absorption/scattering from the clouds. To simulate the operation of a PV system with one-minute resolution for a specific coordinate, we have to use a model based on the CSI of the solar irradiance data, capturing the uncertainties caused by cloud movements. The proposed model is based on clustering the days of each year into groups of days, e.g., (i) cloudy, (ii) intermittent cloudy, and (iii) clear sky. The CSI data of each group are divided into bins of magnitudes and the transition probabilities among the bins are identified to deliver a Markov Chain (MC) model to track the intraday weather condition variations. The proposed model is tested on the measurements of two PV systems located at two different climatic regions: (a) Yverdon-les-Bains, Switzerland; and (b) Oahu, Hawaii, USA. The model is compared with a previously published N-state MC model and the performance of the proposed model is elaborated. Full article

Hepatitis B virus (HBV) infection is a serious problem and earlier studies in Papua New Guinea have reported a high prevalence of hepatitis B virus infection. These studies were undertaken using insensitive tests and before an expanded immunization program. The current HBV status is therefore uncertain. A retrospective study to investigate the HBV status was carried out using blood donor data at Nonga General Hospital, East New Britain Province, Papua New Guinea, from January 2003 to December 2018. Additional data for Human Immunodeficiency Virus, syphilis and hepatitis C virus were also collected. Data were analysed using NCSS statistical software. The mean hepatitis B antigen (HBsAg) sero-prevalence was 21% for the period of study and showed a downward trend over the period of the study, which may reflect the effect of the extended immunization program. HBsAg prevalence in male donors (23%) was significantly higher than females (16%). Donors living in Pomio district had a significantly lower proportion of sero-positive HBsAg donors (7%) than Gazelle (22%), Kokopo (22%) and Rabaul (20%), which was attributed to this district’s geographical isolation. Ethnically, Pomios donors (8%) had significantly lower HBsAg prevalence than the Taulils, (29%), Bainings (21%) and Tolais (21%). Fifteen to nineteen year olds (23%) were the predominant age group affected, and vertical or perinatal transmission was probably the primary transmission route. Our findings call for greater awareness on the part of public policy makers and should be considered when planning future public health campaigns. Full article