Livestock intensification and environmental sustainability: An analysis based on pasture management scenarios in the brazilian savanna.

Brazil's major beef production occurs in the Cerrado, predominantly as extensive pastures that covers ∼50 Mha of the biome, of which approximately 2/3 show signs of degradation. Pasture recovery is now a key environmental policy, as it improves land use efficiency and soil carbon sequestration. However, as intensification leads to higher cattle stocking rates and external inputs (fertilizers, liming, etc.), the impact of improved pastures on greenhouse gas mitigation is still debatable. This study focused on the Cerrado biome and aimed to (i) quantify soil carbon stock changes under different scenarios of management and recovery of degraded pastures. In addition, (ii) the potential for capturing carbon in the soil to mitigate emissions of greenhouse gases (GHG) by the intensification of pastures was evaluated. Soil C stock changes (0-20 cm) were assessed using the Century model version 4.5, which had been previously validated for the region. Model parameters were adjusted for three pastures classes (degraded, intermediately degraded, and not degraded) within a time-series (1985-2020) of land use maps for the Cerrado, serving as baselines. Scenarios of pasture intensification were modeled against these baselines, and an analysis was carried out on the estimated changes in soil C stock and greenhouse gas balance. Before the intensification scenario (year 2020), the total carbon stock was estimated to be ∼1830 Mt for the whole pasture area, whose spatial distribution corresponded to edaphoclimatic contrasts and pasture conditions. The highest soil organic carbon stocks were observed in the non-degraded pastures. With the increase in carrying capacity, beef production is estimated to potentially increase by 1/3 due to the recovery of degraded areas through intensive management. This increase would be sufficient to meet the projected ∼12% increase in Brazil's livestock production by the end of the decade if all pasture areas are restored, which is much possibly an unrealistic scenario as not all degraded areas are suitable for crops or can successfully improve pasture yield. In addition, the increase in soil C stocks was only sufficient to compensate for 27% and 42% of the GHG emissions resulting from intensification in areas with intermediate and severe degradation, respectively. Therefore, to strike a balance between economic considerations and environmental impact, additional strategies are needed to reduce GHG emissions and/or enhance C sinks, such as increasing tree density on farms. From this perspective, implementing livestock intensification at the landscape scale can promote C stocks and the diversity of ecosystem services, opening the possibility of ecosystem restoration.

Acute Effect of Oral Adenosine Triphosphate (ATP) Supplementation on Muscular Performance in Trained Adults.

INTRODUCTION: Adenosine Triphosphate is a molecule with the function of generating energy, where high levels are directly related to cellular and muscular health. Oral supplementation appears as a possibility to guarantee such levels, and is normally consumed in capsules, which can be acute or chronic. OBJECTIVES: To verify the influence of a dose of ATP on muscular performance in adults. METHODS: This is an acute, crossover, randomized, double-blind, placebo-controlled intervention study. 18 trained men were recruited, with an average age of 27.95 years. Two visits were made to the laboratory, where each of the protocols consisted of randomized supplementation of 400 mg of Peak ATP® or placebo, and 30 min later, five series were performed, where the first consisted of five repetitions and the following four of ten repetitions at 60° per second in knee extension and flexion on a Biodex® 4.0 isokinetic dynamometer, where the volunteers' muscle strength and resistance to fatigue were measured. For data analysis, data normality was assessed using Shapiro Wilk, the ANOVA repeated measures test with Bonferroni post hoc. To identify the size of the effect, the Cohen test was performed, and the statistical package used was SPSS 25 with an applied significance of p < 0.05. RESULTS: Acute supplementation was unable to achieve significant improvements in muscle strength indicators. The supplement delays drops in strength as the exercise progresses in knee extension compared to the placebo. CONCLUSIONS: An acute dose of 400 mg of ATP did not improve the volunteers' muscle strength indicators, but it was able to reduce fatigue levels as the exercise progressed, enabling greater performance for longer.

Minimally processed recycled yttria-stabilized tetragonal zirconia for dental applications: Effect of sintering temperature on glass infiltration.

This study aimed to develop a recycling process for the remnants of milled 3Y-TZP and enhance their properties using glass infiltration. 3Y-TZP powder was gathered from the vacuum system of CAD-CAM milling equipment, calcined and sieved (x < 75 µm). One hundred twenty discs were fabricated and pre-sintered at 1000 °C/h. These specimens were then divided into four groups, categorized by glass infiltration (non-infiltrated [Zr] or glass-infiltrated [Zr-G]) and sintering temperature (1450 °C [Zr-1450] or 1550 °C [Zr-1550]/2h). After sintering, the specimens were characterized by X-Ray Diffraction (XRD), relative density measurement, and scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS). The biaxial flexural strength test was performed according to the ISO 6872 and followed by fractographic analysis. Subsequent results were analyzed using Weibull statistics. Relative density values of the sintered specimens from Zr-1450 and Zr-1550 groups were 86.7 ± 1.5% and 92.2 ± 1.7%, respectively. Particle size distribution revealed particles within the range of 0.1-100 µm. XRD analysis highlighted the presence of the ZrO2-tetragonal in both the Zr-1450 and Zr-1550 groups. Glass infiltration, however, led to the formation of the ZrO2-monoclinic of 9.84% (Zr-1450-G) and 18.34% (Zr-1550-G). SEM micrographs demonstrated similar microstructural characteristics for Zr-1450 and Zr-1550, whereas the glass-infiltrated groups exhibited comparable infiltration patterns. The highest characteristic strength was observed in the glass-infiltrated groups. Fractographic analyses suggested that fracture origins were related to defects on the tensile side, which propagated to the compression side of the samples. Both the sintering temperature and glass infiltration significantly influenced the mechanical properties of the 3Y-TZP recycled.

Numerical analysis of the mechanical behavior of ceramic dental implants based on Ce-TZP/Al2O3 composite.

This study aimed to identify the potential use of the ceramic composite ZrO2(CeO2)-Al2O3 as a dental implant due to its intrinsic geometry and different masticatory loads based on finite element simulations. Ceramic samples were sintered at 1500 °C-2h, and characterized: The mechanical properties of the ceramic composite (hardness, fracture toughness, flexural strength, Young's Modulus, and Poisson ratio) were determined, in addition to the relative density and its structural characteristics. Commercial dental implant designs (incisal and third-molar) on CAD models were used in this study as an initial implant geometry applied in a typical simulated mandible anatomy. Finite element models were generated for implant geometries using CAD and CAE techniques. Loading cases were considered based on different intensities (100-500 N) and orientation angles to the implant axis (0° and 45°) to reproduce human masticatory conditions. For comparison purposes, the numerical predictions were compared with finite element simulations of gold-standard titanium implants. Ce-TZP/Al2O3 sintered ceramics showed flexural strength of 952.6 ± 88 MPa, hardness and fracture toughness of 1427 ± 46 HV and 11.3 ± 0.4 MPa m1/2, respectively, beside Young's modulus of 228.3 ± 65 GPa and Poisson ratio of 0.28. For both Ce-TZP/Al2O3 dental implant geometries, the implant prototypes showed adequate mechanical behavior regardless of the masticatory load value or the orientation angle applied in the simulations: All finite element predictions are lower than the values established by Mohr Coulomb's failure criterion, allowing the feasibility, preliminarily, of the proposed ceramics for dental implant applications without fracture risk.

Comparison between different fracture toughness techniques in zirconia dental ceramics.

Vickers indentation (IF) and single-edge-V-notched beam (SEVNB), to measure the fracture toughness (KIC ) of zirconia-based dental ceramics and mathematical models were proposed to establish a correlation between both. Zirconia (ZrO2 ) stabilized with 3 mol. % of Y2 O3 (3Y-TZP) and 5 mol% of Y2 O3 (5Y-PSZ) were compacted (n = 42) and sintered for 2 h at different temperatures (1475°C, 1500°C, 1550°C, or 1600°C). After sintering, they were characterized by relative density using the ASTM C373-88 standard, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The average grain size was measured according to the ASTM E1382-97 standard. The fracture toughness (KIC ) was determined using two methods: Vickers indentation fracture toughness (KIC-IF ): method based on mathematical modeling that considers the parameters used for the Vickers hardness test and Fracture toughness by the single-edge-V-notch-beam (KIC-SEVNB ): method proposed by ISO 23146:08. The main phases of the 3Y-TZP and 5Y-PSZ ceramics were ZrO2 -tetragonal and ZrO2 -cubic, respectively. The 3Y-TZP specimens showed equiaxed grains with average grain sizes ranging from 0.55 to 0.79 µm. The grain sizes of 5Y-PSZ of specimens sintered at 1475°C and 1600°C were 0.62 and 2.32 µm, respectively. For all ceramics the crack size ratio was c/a < 2.5, suggesting a Palmqvist-type crack system. The fracture toughness measured by the Vickers indentation method (KIC-IF ) and by the SEVNB method (KIC-SEVNB ) was the same when the experimental data were fit to a mathematical model.

Effect of the surface finish on the mechanical properties and cellular adhesion in (Ce,Y)-TZP/Al2O3 ceramic composites for denture implants.

Ceramic composites based on (Ce, Y)-TZP/Al2O3 system have great potential for applications as dental implants due to their unusually great balance between good mechanical properties and resistance to hydrothermal degradation. Surface roughness plays an important role in controlling these properties, but few studies have investigated the relationship between cytocompatibility and surface roughness, at levels considered moderate and low, comparable to titanium implants. In this work, bending strength, hydrothermal degradation and biological evaluation of a ceramic composite based on (Ce,Y)-TZP/Al2O3 system were investigated as a function of surface roughness. Compacted samples were sintered at 1500 °C - 2h and then submitted to different surface treatments: Group 1 composed of samples with smooth surfaces, Group 2 and Group 3 composed of rough surfaces (grinded with 15 µm or 45 µm diamond sandpaper, respectively. Samples were characterized by X-ray diffraction, scanning electron microscopy, contact angle and optical profilometry and then subjected to hydrothermal degradation tests in autoclave (134 °C - 2 bar) using artificial saliva. The Piston-on-three-balls (P-3B) testing was used to determine flexural strength. To assess indirect cytotoxicity, samples were immersed in the culture medium for NIH-3T3 cells for 72 h. Furthermore, cell adhesion and proliferation were investigated using MG63 cells (human osteosarcoma) after 3, 7, 14, and 21 days of culture. Cytotoxicity, adhesion, and cell proliferation were examined by the Methyl Tetrazolium salt (MTS) and Alizarin Red, using a confocal laser microscope. The results indicated that the materials have high resistance to degradation. Furthermore, the (Ce,Y)-TZP/Al2O3 composites are not cytotoxic. The flexural strength of the composites was 913 ± 103 MPa in samples presenting original (smooth) surface, however, a reduction in the order of 17% was observed in samples containing rough surfaces. The rougher samples show the best cellular adhesion and proliferation, leading to the formation of a mineralized matrix after 21 days. These results clearly suggest that the new (Ce,Y)-TZP/Al2O3 brand is strong and highly biocompatible and warrants further study.

Physical Properties and Color Stainability by Coffee and Red Wine of Opaque and High Translucency Zirconia Dental Ceramics after Hydrothermal Degradation.

The objective was to evaluate the bending strength, phase transformation, roughness, and color stainability by coffee and red wine of opaque and high translucency yttria-stabilized zirconia before and after hydrothermal degradation in saline solution or oral mouthwash. Presintered zirconia blocks with medium opacity (ZrO2-3 mol. % of Y2O3) designed as ZrOp and high translucency zirconia (5.2 mol. % of Y2O3) designed as ZrTrans were used. Specimens (n = 80/group) were cut and sintered at 1500°C for 2 h. The specimens were hydrothermally degraded in an autoclave (134°C-1.8 kg/cm2) for 20 h in saline solution (0.5 g/L) and oral mouthwash solution (0.02% sodium fluoride, without alcohol and with 21.6% alcohol). After hydrothermal degradation, the samples were immersed in containers with coffee or red wine for 14 days to determine their color stainability. The results showed that the ZrOp had a higher bending strength than the ZrTrans before and after hydrothermal aging. In ZrOp and ZrTrans, the roughness increased after hydrothermal degradation. ZrOp samples had a higher Ra roughness than the ZrTrans samples. Roughness did not change after immersion in coffee or red wine. The X-ray diffraction (XRD) results showed that ZrOp samples underwent a tetragonal to monoclinic phase transformation, while ZrTrans samples were unchanged. Both ZrOp and ZrTrans samples changed color after immersion in coffee and red wine.

Effects of aerobic exercise combined with resistance training on health-related physical fitness in adolescents: A randomized controlled trial.

Background: /Objective: This study aimed to compare the effects of two combined training methods on health-related physical fitness components in adolescents. Methods: Seventy-six adolescents (16.1 ± 1.1 years, n = 44 female) were randomized into groups of moderate-intensity continuous training combined with resistance training (MICT + RT), high-intensity interval training combined with resistance training (HIIT + RT), or Control. The training sessions were performed twice weekly for 12 weeks. The health-related physical fitness components evaluated were: body composition, muscular and cardiorespiratory fitness. Results: The intervention groups had a significant reduction in body fat percentage and improvement in abdominal repetitions and VO2peak after 12 weeks of combined exercise program (p < 0.001). Intervention effects were found to significantly reduce body fat percentage for the MICT + RT and HIIT + RT groups compared to the control group (mean difference: -3.8; 95% CI: -6.2; -1 0.3; mean difference: -4.7; 95%CI: -7.1; -2.3, respectively). For muscle fitness, significant effects of the intervention were found in increasing the number of abdominal repetitions favoring the MICT + RT group compared to the control group (mean difference: 9.5; 95% CI: 4.4; 14.7) and HIIT + RT compared to the control group (mean difference: 14.1; 95% CI 9; 19.3). For cardiorespiratory fitness, significant effects of the intervention on improving VO2peak were found in the experimental groups (MICT + RT vs Control group: mean difference: 4.4; 95% CI: 2.2; 6.6; and HIIT + RT vs. Control group: mean difference: 5.5, 95% CI: 3.3; 7.7). Conclusion: The results suggest that 12 weeks of training using MCIT + RT or HIIT + RT showed a similar effect for health-related physical fitness components in adolescents.

Experimental analysis and numerical simulations of the mechanical properties of a (Ce,Y)-TZP/Al2O3/H6A ceramic composite containing coupled toughening mechanisms.

OBJECTIVES: This study investigates the simulation of the mechanical behavior of a bioceramic composite based on (Ce,Y)-TZP reinforced with equiaxed Al2O3 and platelet-shaped hexaaluminate (H6A) grains using Finit Element Method (FEM). METHODS: A commercial (Ce, Y)-TZP/Al2O3 ceramic powder was compacted into disc-shaped specimens that were sintered at 1500 °C for 2 h. The sintered samples were further subjected to hydrothermal degradation in an autoclave at 134 °C, 0.2 MPa, for 10 h and characterized according to their phase composition, microstructure, and relative density. Their flexural strength values were determined by the piston-on-three-ball test, and Weibull statistics was used to evaluate the results. Their hardness, fracture toughness and elastic parameters were also measured. Numerical simulations of the biaxial strength test were performed using the ABAQUS finite element code. RESULTS: The sintered ceramic composite material presented relative density >99%, high resistance to hydrothermal degradation, average hardness of 1435 ± 35 HV, fracture toughness KIC of 9.7 ± 0.5 MPa m1/2, and average biaxial flexural strength of 952.6 ± 88 MPa. The numerical predictions of the biaxial flexural strength showed a consistently lower average biaxial flexural strength value of 880.9 MPa, ∼10% lower than the average experimental results. CONCLUSIONS: The differences observed are attributed to the complex coupled toughness mechanisms of this material, not included in the finite element simulations.

Flexural strength of 3Y-TZP bioceramics obtained by direct write assembly as function of residual connected-porosity.

OBJECTIVES: The present work reports the effect of the extrusion nozzles' size and consequent residual porosity on the flexural strength of 3Y-TZP bioceramics fabricated by direct write assembly technology. METHODS: A printable ink containing a volume fraction of 45% of 3Y-TZP (ZrO2 stabilized with 3 mol% Y2O3) submicron powder, carboxymethyl cellulose and polyethyleneimine as additives was fine-tuned by rheological measurements. Different nozzle diameters (0.41 mm, 0.33 mm, and 0.25 mm) were used to print 3D specimens with proper dimensions for structural and mechanical characterization after sintering, namely relative density, linear shrinkage, and three-point flexural strength. Bulk surface sample and exposed fractured surfaces after flexural strength tests were analyzed by X-ray diffraction, Rietveld refinement and scanning electronic microscopy. Strength reliability and failure probability of the three sample groups were analyzed by Weibull statistics. RESULTS: The sintered samples exhibited relative densities in the range of 78% (nozzle Ø 0.41 = mm) and 82% (nozzle Ø 0.25 = mm), i.e., a slight increase in the residual interfilamentous porosity is observed, as the extrusion tip diameter increases, while linear shrinkage is statistically similar (≈25%). Likewise, a progressive reduction of flexural strength and Weibull modulus as nozzle diameter increases was noticeable, being respectively σf = 337,5 ± 49 MPa and m = 6.6 for the smallest nozzle diameter (Ø = 0.25 mm) and σf = 261.4 ± 79 MPa and m = 3.2 for the biggest one (Ø = 0.41 mm). Unlike nozzle diameter, the material is constituted by 79-81 wt% tetragonal t-ZrO2 and 19-21 wt% cubic c-ZrO2 with equiaxed grain sizes between 0.3 and 0.6 µm. CONCLUSION: X-ray diffraction analyses on the fracture surface of flexural test samples suggests that the toughening mechanism by tetragonal→ monoclinic phase transformation is the main responsible for the mechanical strength of this structural ceramic. Additionally, the reduction of flexural strength for samples printed with extrusion nozzle of 0.41 mm could be explained by the surface roughness of the bending surfaces, as well as the lower effective resistance to crack-propagation arising from the higher size of residual pores on the fracture surface.

Optimizing the microstructure of a new machinable bioactive glass-ceramic.

OBJECTIVES: This study aimed to optimize the crystallization process and the microstructure of a new bioactive glass-ceramic (GC) previously developed by our research group to obtain machinable glass-ceramics. METHODS: Differential scanning calorimetry (DSC) analyses were conducted to explore the characteristic temperatures and construct a semi-quantitative nucleation curve. The GC specimens were characterized by X-ray diffraction (XRD) and Rietveld refinement. Their brittleness index (B) and machinability were characterized and compared with IPS e.max-CAD®. Their Young's modulus, fracture toughness, and hardness were assessed. RESULTS: We found that the maximum crystal nucleation rate temperature of this GC is ~470 °C. Treatments were designed based on the 1st DSC peak onset (570 °C), 1st peak offset (650 °C), and 2nd peak offset (705 °C) crystallization temperatures of lithium metasilicate (LS, LiSi2O3) and lithium disilicate (LS2, Li2Si2O5). Rietveld refinement indicated an increase in LS2 and a reduction in LS and amorphous phase for increased temperatures and longer treatment times. Their B values indicate good machinability compared with that of the control group based on statistical analyses. As expected, lower levels of LS2 increase the machinability regardless of the rotation speed adopted, leading to a greater depth of cut and reduced Edge Chipping Damage Depth (ECDD). CONCLUSION: This bioactive GC with optimized microstructure presents high machinability. For treatment temperatures above 570 °C, the number of elongated LS2 crystals increases and decreases the amorphous phase content, which reduce the machinability of the GC, and should therefore be avoided. The best results were obtained using heat treatment at 570 °C, which produces LS crystals embedded in a glassy matrix (67%) with small contents of secondary phases.

Mechanical properties of ceramic composites based on ZrO2 co-stabilized by Y2O3-CeO2 reinforced with Al2O3 platelets for dental implants.

OBJECTIVES: The objective of this work was the development and characterization of a ceramic composite based on (Ce,Y)-TZP/Al2O3 aiming an application on dental implants, comparing it with conventional monolithic 3Y-TZP ceramics, currently used for the same type of application. METHODS: Ceramic samples, 3Y-TZP (n = 40) and (Ce,Y)-TZP/Al2O3 (n = 40), were sintered at 1500 °C - 2h and characterized by relative density, X-Ray diffraction (XRD) and microstructure. Then, the samples of both materials were divided into two groups: 1) samples with original (as sintered) surfaces; 2) samples with conditioned, polished, surfaces. All samples were submitted to hydrothermal degradation tests, on an autoclave (134 °C - 2 bar), for 10 h in artificial saliva. The degraded samples were characterized by XRD and the polished group were also characterized by their elastic moduli, Vickers hardness and fracture toughness (Vickers indentation method). Both groups were also submitted to a flexural strength test, 3B-P testing, for which the data were interpreted using Weibull statistics. RESULTS: All sintered specimens presented nearly full densification. After the hydrothermal degradation tests, 3Y-TZP samples presented 16.4% of monoclinic (m)-ZrO2 phase while the composite samples withheld 100% of tetragonal (t)-ZrO2 phase. Both materials presented equiaxial ZrO2 grains with an average size of 0.48 ± 0.17 µm and 0.75 ± 0.22 µm, respectively, for the monolithic and composite ceramics. In the composites, is observed the presence of well distributed Al2O3 grains on the ZrO2 matrix, in two distinct morphologies: equiaxial grains and platelets. The composites (Ce,Y)-TZP/Al2O3 presented average values of elastic moduli, Vickers hardness and fracture toughness of 228.3 ± 6.5 GPa, 1427 ± 46 HV e 11.3 ± 0.4 MPa m1/2, respectively. An inversely proportional relationship is observed between the roughness and the bending strength, since the 3Y-TZP samples presented a average strength of 860.7 ± 81 MPa (as-sintered) and 965.4 ± 93 MPa (polished) while the (Ce,Y)-TZP/Al2O3 composites presented average strength of 810.6 ± 147 MPa (as-sintered) and 952.6 ± 88 MPa (polished). CONCLUSIONS: The composites (Ce,Y)-TZP/Al2O3 showed high resistance to degradation in saliva and adequate properties for use as dental implants. Values of flexural strength (>950 MPa) and Weibull modulus (m > 10) were similar to the conventional 3Y-TZP ceramics. Moreover, its hardness, elastic modulus and fracture toughness were higher than those obtained for 3Y-TZP. The expressive values of KIC obtained for (Ce,Y)-TZP/Al2O3 composites are results of association of different toughening mechanisms acting simultaneously in the material.

Effect of hydrothermal aging on the properties of zirconia with different levels of translucency.

OBJECTIVES: The aim of this study was to evaluate the effect of hydrothermal aging on the mechanical properties and translucency of dental zirconia with different levels of translucency. METHODS: Three different types of dental yttria-stabilized zirconia were used: 3Y-TZP (ZrO2 - 3 mol.% Y2O3) of medium opacity (designated Z3OP), 3Y-TZP of medium translucency (Z3MT), and 5Y-PSZ (ZrO2 - 5 mol.% Y2O3) of high translucency (Z5HT). A total of 120 specimens were sintered (n = 40 specimens/group). The control group (sintered→polished→heat-treated) and the aged group (sintered→polished→heat-treated→hydrothermally degraded at 134 °C, 2 bar, 5h) were characterized by relative density, quantitative phase analysis by X-ray diffraction using the Rietveld method, microstructural analysis by scanning electron microscopy, surface roughness and translucency. All groups were submitted to a biaxial flexural strength test. Data analysis using Kruskal-Wallis, Nemenyi (p-value = 0.05), and Weibull statistics were used. RESULTS: All sintered specimens presented full densification. After aging, an increase of the m-ZrO2 phase content was observed for the Z3OP group. On the other hand, Z3MT and Z5HT did not show any m-ZrO2 phase, indicating resistance to the hydrothermal degradation. Smaller grains were observed in the Z3MT group in relation to Z3OP group and the Z5HT group presented a bimodal grain distribution, where the largest grains were associated to cubic ZrO2. Z3OP exhibited a slight increase in roughness as a function of degradation, while the roughness remained statistically stable in the other groups. Translucency was little influenced by degradation, but considerably affected by increasing thickness. The Z5HT samples were the group with the highest translucency among the control groups. Z3OP exhibited the highest flexural strength, while being the most susceptible to hydrothermal degradation. The lowest values were presented by Z5HT in all groups, due to the high concentration of c-ZrO2 grains. CONCLUSION: Hydrothermal aging is less critical to the flexural strength of zirconia-based materials than the materials' composition and microstructure. Z5HT zirconia showed the highest translucency, however the measured difference is not visually perceptible. Z5HT was considered the most resistant to hydrothermal degradation.

Preparation of TiC/Ti3SiC2 Composite by Sintering Mechanical Alloyed Ti-Si-C Powder Mixtures.

The present work aims to evaluate the crystalline phases and microstructure of a TiC-Ti3SiC2 ceramic composite, obtained by mechanical alloying of Ti, C and Si powders and subsequent sintering. A mechanical alloying technique in a planetary ball mill for 1, 10, 50, 100 and 200 h using Ti, Si and C powders with molar ratios of 3:1:2 as feedstock in argon (Ar) gas was employed to prepare nano-sized Ti-Si-C powders. TiC crystallite size and lattice strain were evaluated by X-ray diffraction analysis (XRD) and the morphological characteristics and particle size distribution were examined using scanning electron microscope (SEM). After milling, a reduction of the average particle size and crystallinity is observed. Furthermore, after 10 h of milling time, TiC starts to crystallize. The powder mixture obtained after 200 h of milling was compacted and sintered at 1200 °C under controlled atmosphere, for 15 min, 2 h or 4 h with a heating rate of 5 °C/min. Almost full densification of samples sintered for 2 h and 4 h has been achieved, with relative densities close to 98.8±0.2% and TiC and Ti3SiC2 as crystalline phases with an average crystallite size of TiC near 0.7 µm. Rietveld refinement indicates that the majority TiC-cubic phase (>85 vol%) presents a unit cell volume of 8.03 nm³ after sintering at 1200 °C. Despite the maintenance of the volume of the hexagonal unit cell of Ti3SiC2, (15.05 nm³), the increase of the isothermal sintering time resulted in an increase of the lattice parameter "a", from 0.315 nm to 0.320 nm, and a reduction of the lattice parameter "c" from 1.750 nm to 1.705 nm. The control of the changes in the residual stresses within the TiC matrix and the Ti3SiC2 precipitates, which is associated with the deformation in the lattice parameters, must be controlled to achieve high fracture toughness in the composite.

Modeling of the Influence of Chemical Composition, Sintering Temperature, Density, and Thickness in the Light Transmittance of Four Zirconia Dental Prostheses.

Research has increasingly been conducted to improve the toughness and aesthetics of zirconium oxide (zirconia) used in prosthetic dentistry. However, the balance between better mechanical properties and greater translucency, to ensure aesthetic requirements, is still a challenge in the development of a novel zirconia for dentistry applications. This study evaluated the transmittance of visible light for four types of pre-sintered zirconia blocks used in dentistry (3Y-SBE, Zpex, Zpex-4, and Zpex-Smile). The objective is to analyze the simultaneous influence of sintering temperature, in the range of 1450-1560 °C, as well as the chemical composition (%Y2O3), density, and thickness (1.0, 1.3, 1.6, and 2.0 mm) in the zirconia's transmittance. To evaluate the interactive influence of these variables, a statistical learning model based on gradient boosting is applied. The results showed that the effect of the sintering temperature has an optimal (maximum transmittance) point. Increasing the temperature beyond this point reduces the transmittance of the material for all types of zirconia. Moreover, the optimal transmittance point is affected by the chemical composition of each type of zirconia. In addition, the results showed that the transmittance of all types of zirconia had an inverse relationship with the density, zirconia Zpex-Smile being the most sensitive to this parameter. Furthermore, the transmittance of 3Y-SBE, Zpex, and Zpex-4 decreases approximately linearly with the specimen thickness, whereas zirconia Zpex-Smile has a sublinear decrease, which is expected due to the optical isotropy of the cubic phase.

Prolonged tropical forest degradation due to compounding disturbances: Implications for CO2 and H2 O fluxes.

Drought, fire, and windstorms can interact to degrade tropical forests and the ecosystem services they provide, but how these forests recover after catastrophic disturbance events remains relatively unknown. Here, we analyze multi-year measurements of vegetation dynamics and function (fluxes of CO2 and H2 O) in forests recovering from 7 years of controlled burns, followed by wind disturbance. Located in southeast Amazonia, the experimental forest consists of three 50-ha plots burned annually, triennially, or not at all from 2004 to 2010. During the subsequent 6-year recovery period, postfire tree survivorship and biomass sharply declined, with aboveground C stocks decreasing by 70%-94% along forest edges (0-200 m into the forest) and 36%-40% in the forest interior. Vegetation regrowth in the forest understory triggered partial canopy closure (70%-80%) from 2010 to 2015. The composition and spatial distribution of grasses invading degraded forest evolved rapidly, likely because of the delayed mortality. Four years after the experimental fires ended (2014), the burned plots assimilated 36% less carbon than the Control, but net CO2 exchange and evapotranspiration (ET) had fully recovered 7 years after the experimental fires ended (2017). Carbon uptake recovery occurred largely in response to increased light-use efficiency and reduced postfire respiration, whereas increased water use associated with postfire growth of new recruits and remaining trees explained the recovery in ET. Although the effects of interacting disturbances (e.g., fires, forest fragmentation, and blowdown events) on mortality and biomass persist over many years, the rapid recovery of carbon and water fluxes can help stabilize local climate.

Mechanical properties of lithium metasilicate after short-term thermal treatments.

OBJECTIVES: The properties of lithium-silicate dental glass-ceramics are very sensitive to heat treatments which are conducted after CAD/CAM (Computer Aided Design/Computer Aided Machining) processing. In particular, temperature variations inside the furnace chamber which may occur between different models of furnaces may result in altered mechanical properties of these materials. In this work, the effect of thermal treatment parameters on the transformation of lithium metasilicate (Li2SiO3) into lithium disilicate (Li2Si2O5) and on the resulting mechanical properties has been investigated. METHODS: Lithium metasilicate samples. containing 59 vol% of amorphous phase, were thermal treated under vacuum at 820 °C for up to 9 min or at 840 °C for 7min (as control group). The samples were characterized by X-ray diffraction analysis using the Rietveld refinement and scanning electron microscopy. Hardness and fracture toughness (n = 30 indentations/group) were evaluated by the Vickers indentation technique. The elastic properties were measured by the Impulse Excitation Technique and the flexural strength (n = 15/group) was measured using the piston-on-three-ball (P-3B) testing assembly. Complementary Weibull statistic were conducted as statistical analysis. RESULTS: The results indicate a progressive reduction of the Li2SiO3 phase with increasing isothermal holding time at 820 °C until the conversion into Li2Si2O5, is completed for treatments longer than 7 min. A complete transformation of Li2SiO3 into Li2Si2O5 has also been observed for the control group of samples treated at 840 °C for 7min. Samples of the control group exhibited hardness, fracture toughness, Young's modulus and Poisson ratio 5.76 ±â€¯0.17 GPa, 1.60 ±â€¯0.03 MPa m1/2, 100.3 GPa e 0.21, respectively. The reduction of the thermal treatment temperature to 820 °C reduced the fracture toughness and the Young's modulus between 5-10%. Furthermore, the fracture strength was significantly reduced by approximately 71%, because of the lower amount of elongated Li2Si2O5 grains and higher amount of residual amorphous phase. CONCLUSION: In general, the glass-ceramic material containing residual amorphous phase associated with various crystalline phases, presented a reduction of its mechanical properties in relation to the lithium disilicate glass-ceramic. The reasons for these differences in the mechanical behavior are discussed by analyzing the influences of different phenomena such as thermal expansion anisotropy, residual stresses, amorphous phase content and microstructure on the properties.

Composição corporal e perfil somatotípico de atletas da seleção brasileira de futebol de 5 / Body composition and somatotype of athletes of Brazilian 5-a-side football team / Composición corporal y somatotipo de los atletas de la selección brasileña de fútbol 5

Resumo O objetivo deste estudo foi verificar o perfil somatotípico e a composição corporal de atletas da seleção brasileira de futebol de 5. Participaram 23 atletas do sexo masculino. Todos foram submetidos à avaliação antropométrica e em seguida foram feitos os cálculos de índice de massa corporal (IMC), percentual de gordura corporal (%GC), somatório de pregas cutâneas (Σ9DC) e somatotipo. Observou-se que apenas os goleiros apresentaram diferença significativa (p ≤ 0,05) nas variáveis de IMC, %GC e Σ9DC em relação às outras posições. Os goleiros apresentaram perfil endomorfo-mesomorfo, os fixos mesomorfo-equilibrado e os alas e pivôs, endo-mesomorfo. Concluímos que os goleiros apresentam diferença significativa de %GC quando comparados com as outras posições e apresentaram diferenças somatotipológicas significativas em relação às outras posições. O mesmo foi observado na posição fixo quando comparados com os pivôs.

Abstract The aim of this study was to determine the profiles somatotype and body composition of athletes of Brazilian 5-a-side football team. This study involved 23 male athletes. Were all submitted to anthropometric measurements and then were carried the calculations of body mass index (BMI), body fat percentage (BF%), Skinfolds sum (Σ9DC) and somatotype. It was observed that goalkeepers differ significantly (p ≤ 0.05) in body mass, BF% and Σ9DC for other positions. The goalkeepers showed profile endomorph-mesomorph, the defender mesomorph- balanced, while the winger and pivot, endo-mesomorph. Concluded that the goalkeepers were significant differences in BF% when compared to other positions and showed significant differences in somatotype compared to other positions, the same was observed in defenders when compared with pivots.

Resumen El objetivo del estudio fue determinar los perfiles somatotípicos y la composición corporal de los atletas de la selección brasileña de fútbol 5. Participaron en el estudio 23 atletas masculinos. Todos pasaron mediciones antropométricas y después se realizaron los cálculos del índice de masa corporal (IMC), porcentaje de grasa corporal (%GC), la suma de pliegues cutáneos (Σ9DC) y somatotipo. Los porteros difieren (p ≤ 0,05) en la MC, %BF y Σ9DC con relación a otras posiciones. Los porteros mostraron perfil mesomorfo-endomorfo, los defensas mostraron un perfil mesomorfo-equilibrado y laterales y pivotes, endomorfo-mesomorfo. Llegamos a la conclusión de que en los porteros se encontraron diferencias significativas en el %GC en comparación con otras posiciones y mostraron diferencias significativas en el somatotipo de otras posiciones. Lo mismo se observó en una posición fija en comparación con los pivotes.

Efeitos de uma intervenção com pedômetro sobre o risco metabólico em crianças obesas / Effects of an intervention with pedometer on metabolic risk in obese children / Efectos de una intervención con podómetro en el riesgo metabólico en niños obesos

RESUMO Introdução: Nas últimas décadas, a incidência de obesidade na população pediátrica vem aumentando, juntamente com a inatividade física. A obesidade e a inatividade física são componentes predisponentes para o agravo dos fatores de risco metabólico, sendo de fundamental importância seu tratamento visando melhora da saúde dos jovens. Objetivo: Verificar o efeito de 12 semanas de uma intervenção focada na atividade física sobre os fatores de risco metabólico em crianças obesas. Métodos: A amostra final foi composta por 19 escolares com idade entre oito e 10 anos (10 no grupo pedômetro e nove no grupo controle). A atividade física foi mensurada e orientada por meio do pedômetro Yamax(r) sw 700 (Tóquio, Honchu, Japão). Para comparações intra e entre grupos foi aplicado a ANOVA two way para medidas repetidas com significância estipulada em p < 0,05. Resultados: O número de passos aumentou significativamente somente no grupo pedômetro após as 12 semanas de intervenção (pré 9729,7 ± 2539,8 vs. pós 13151,6 ± 3581,7). Foi observado aumento significativo do peso corporal, da estatura e do IMC no grupo controle. No grupo pedômetro, observou-se aumento significativo apenas na estatura. Com relação aos fatores de risco metabólicos, não foi encontrada mudança significativa no grupo controle, enquanto no grupo pedômetro foi observada diminuição significante nos valores de insulina (pré 12,21 ± 8,53 vs. pós 7,26 ± 4,70 µUI/ml) e HOMA IR (pré 2,76 ± 1,93 vs. pós 1,49 ± 0,93). Conclusão: A presente intervenção com atividade física a partir do estabelecimento de metas utilizando pedômetros reduziu significativamente as concentrações de insulina e o índice de homeostase (HOMA IR) em crianças obesas, independentemente da perda de peso.

ABSTRACT Introduction: In recent decades, the incidence of obesity in children is increasing along with physical inactivity. Obesity and physical inactivity are predisposing components to the worsening of metabolic risk factors and treatment is fundamental aiming at improving the health of young people. Objective: To verify the effect of 12 weeks of an intervention focused on physical activity on metabolic risk factors in obese children. Methods: The final sample consisted of 19 students aged between 8 and 10 years (10 in the pedometer group and nine in the control group). Physical activity was measured and guided by the Yamax(r) sw 700 pedometer (Tokyo, Honshu, Japan). For within and between groups comparisons the two way ANOVA was applied for repeated measures with significance set at p<0.05. Results: The number of steps increased significantly only in the pedometer group after the 12-week intervention (9729.7±2539.8 before vs. 13151.6±3581.7 after). Significant increase was observed in body weight, height, and BMI in the control group. In the pedometer group, it was observed significant increase only in stature. Regarding the metabolic risk factors, there was no significant change found in the control group, while in the pedometer group a significant decrease in insulin levels was observed (12.21±8.53 before vs. 7.26±4.70 µUI/ml after) and HOMA IR (2.76±1.93 before vs. 1.49±0.93 after). Conclusion: This intervention with physical activity from setting goals using pedometers significantly reduced the concentrations of insulin and the homeostasis index (HOMA IR) in obese children regardless of weight loss.

RESUMEN Introducción: En las últimas décadas, la incidencia de la obesidad en los niños es cada vez mayor, junto con la inactividad física. La obesidad y la inactividad física son componentes que predisponen al empeoramiento de los factores de riesgo metabólico, siendo de fundamental importancia el tratamiento destinado a mejorar la salud de los jóvenes. Objetivo: Comprobar el efecto de 12 semanas de una intervención centrada en la actividad física sobre los factores de riesgo metabólico en los niños obesos. Métodos: La muestra final fue de 19 estudiantes de edades comprendidas entre ocho y 10 años (10 en el grupo podómetro y nueve en el grupo de control). La actividad física se midió y fue guiada por el podómetro Yamax(r) sw 700 (Tokio, Honchu, Japón). Para las comparaciones dentro y entre grupos se aplicó la ANOVA de dos vías para medidas repetidas, con una significación establecida en p < 0,05. Resultados: El número de pasos aumentó significativamente sólo en el grupo podómetro después de 12 semanas de intervención (pre 9729,7 ± 2539,8 vs. post 13151,6 ± 3581,7). Se observó un aumento significativo en el peso corporal, la estatura y el IMC en el grupo control. En el grupo podómetro, hubo un aumento significativo sólo en estatura. En cuanto a los factores de riesgo metabólico, no hubo ningún cambio significativo en el grupo control, mientras que en el grupo podómetro se observó disminución significativa de los valores de insulina (pre 12,21 ± 8,53 vs. post 7,26 ± 4,70 µUI/ml) y HOMA IR (pre 2,76 ± 1,93 vs. post 1,49 ± 0,93). Conclusión: Esta intervención con actividad física a partir del establecimiento de metas utilizando podómetros redujo significativamente las concentraciones de insulina y el índice de la homeostasis (HOMA-IR) en niños obesos, independientemente de la pérdida de peso.

Effect of exercise order on the number of repeats and training volume in the tri-set training method / Efeito da ordem dos exercícios sobre o número de repetições e volume de treino no método de treinamento tri-set

Abstract Although the tri-set system is widely adopted by athletes and experienced weight training practitioners aimed at optimizing the metabolic overload, there are still few works in literature on the effect of exercise order manipulation on this training system. Therefore, this work was aimed at investigating the effect of exercise order manipulation on the number of repeats and training volume using the tri-set system for lower limbs. This is a randomized cross-over design study. The experimental group consisted of 14 healthy men (23.53 ± 5.40 years; 24.51 ± 2.96 kg/m2). Subjects were submitted to two experimental sessions at different exercise order for lower limbs: Sequence A: squat on guided bar, leg press 45° and bilateral leg extension; sequence B: bilateral leg extension, leg press 45° and squat on guided bar. Three sets to volitional fatigue in all exercises were performed, with intensity of 75% 1RM. Superiority for sequence B in the total number of repeats (70.14 ± 13 vs 60.93 ± 7.94 repeats, p = 0.004) and total training volume (9129.64 ± 2830.05 vs 8238.29 ± 2354.20 kg, p = 0.014) was observed. Based on the above, the performance of single-joint exercises before multi-joint exercises in the tri-set system adopted for lower limbs induced higher number of repeats and total training volume.

Resumo Embora o sistema tri-set seja amplamente adotado por atletas e praticantes experientes de treinamento com pesos que buscam otimizar a sobrecarga metabólica, a literatura carece de investigações acerca do efeito da manipulação da ordem dos exercícios nesse sistema de treinamento. Sendo assim, objetivou-se investigar o efeito da manipulação da ordem dos exercícios sobre o número de repetições e volume de treino, utilizando o sistema tri-set para membros inferiores. Trata-se de uma pesquisa com delineamento cross-over aleatorizado. O grupo experimental foi composto por 14 homens saudáveis (23,53 ± 5,40 anos; 24,51 ± 2,96 kg/m2). Os avaliados foram submetidos a duas sessões experimentais em diferentes ordens de exercícios para membros inferiores: sequência A: agachamento na barra guiada, leg press 45° e cadeira extensora bilateral; sequência B: cadeira extensora bilateral, leg press 45° e agachamento na barra guiada. Foram executadas três séries até a fadiga voluntária em todos os exercícios, com intensidade de 75% de 1RM. Observou-se superioridade para a sequência B no número total de repetições (70,14 ± 13,00 vs 60,93 ± 7,94 repetições; p = 0,004) e volume total (9129,64 ± 2830,05 vs 8239,29 ± 2354,20 kg; p = 0,014). Diante do exposto, a execução de um exercício monoarticular antes de multiarticulares, no sistema tri-set adotado para membros inferiores, induziu a um maior número de repetições e volume total de treinamento.