Effects of termal treatment on the physical properties of Buchenavia sp. (branquilho) wood

This work aimed to evaluate the effect of heat treatment on the physical properties of wood from Buchenavia sp. The heat treatments were carried out at temperatures of 180 °C and 200 °C for 2 h. Apparent density (AD), basic density (BD), porosity (Ф), mass loss, longitudinal (LS), radial (RS), tangential (TS) and volumetric (VS) shrinkages and anisotropic factor (AF) were determined. The lowest values of basic density (0.67 g cm-3), apparent density (0.77 gcm-3), and porosity (43.3%) were observed for the wood treated at a temperature of 200 °C. Mass losses increased with increasing temperature and the highest values were observed under the condition of 200 °C (9.3%). The LS and AF was not affected by heat treatments. The mean values for RS (3.1%), TS (5.1%), and VS (9.1%) were reduced after the performance of heat treatments at temperatures of 180°C and 200°C, which did not differ from each other. The thermal treatments were able to reduce the dimensional instability of Buchenavia sp. Thermal treatments enhance the use of less prestigious Amazonian woods in the civil construction market.

Utilization of Bitter orange seeds as a novel source for recovery of pectin: Compositional and rheological characterization

The seeds from bitter orange, a by-product from the juice making step, hold the potential to facilitate novel, easy yet high quality pectin extraction. To test this hypothesis, the pectin from orange seeds (OSP) were extracted by distilled water and its compositional parameters and rheological behavior then evaluated. Results showed that galacturonic acid was the major component of OSP (~ 425 mg/g) confirming the purity of extracted pectin, followed by glucose and some minor neutral sugars. Mw, Rn and, Rz for the OSP were 4511.8 (kDa), 61 (nm), and 61.1 (nm), respectively. Rheological measurements showed shear-thinning behavior for OSP that by increasing temperature from 5 to 45 oC, the viscosity of the gum decreased. Power law fitted as the best rheological model describing the flow behavior of OSP. Strain sweep dynamic rheological measurements confirmed an entangled network structure for OSP and the addition of NaCl to the gum dispersion, decreased the consistency coefficient from 35.6 to 23.18 Pa.sn, while the flow behavior index remained unchanged. These results demonstrate for the first time that the OSP can be used as a new source of pectin, with likely a wide range of applications in food industry.

Temperature and interlayer coupling induced thermal transport across graphene/2D-SiC van der Waals heterostructure

Graphene based two-dimensional (2D) van der Waals (vdW) materials have attracted enormous attention because of their extraordinary physical properties. In this study, we explore the temperature and interlayer coupling induced thermal transport across the graphene/2D-SiC vdW interface using non-equilibrium molecular dynamics and transient pump probe methods. We find that the in-plane thermal conductivity κ deviates slightly from the 1/T law at high temperatures. A tunable κ is found with the variation of the interlayer coupling strength χ. The interlayer thermal resistance R across graphene/2D-SiC interface reaches 2.71 $$\times$$ × 10–7$${\text{Km}}^{2} /{\text{W}}$$ Km 2 / W at room temperature and χ = 1, and it reduces steadily with the elevation of system temperature and χ, demonstrating around 41% and 56% reduction with increasing temperature to 700 K and a χ of 25, respectively. We also elucidate the heat transport mechanism by estimating the in-plane and out-of-plane phonon modes. Higher phonon propagation possibility and Umklapp scattering across the interface at high temperatures and increased χ lead to the significant reduction of R. This work unveils the mechanism of heat transfer and interface thermal conductance engineering across the graphene/2D-SiC vdW heterostructure.

Effects of Temperature and Grain Size on Diffusivity of Aluminium: Electromigration Experiment and Molecular Dynamic Simulation

Understanding the atomic diffusion features in metallic material is significant to explain the diffusion-controlled physical processes. In this paper, using electromigration experiments and molecular dynamic (MD) simulations, we investigate the effects of grain size and temperature on the self-diffusion of polycrystalline aluminum (Al). The mass transport due to electromigration are accelerated by increasing temperature and decreasing grain size. Magnitudes of effective diffusivity (Deff) and grain boundary diffusivity (DGBs) are experimentally determined, in which the Deff changes as a function of grain size and temperature, but DGBs is independent of the grain size, only affected by the temperature. Moreover, MD simulations of atomic diffusion in polycrystalline Al demonstrate those observations from experiments. Based on MD results, the Arrhenius equation of DGBs and empirical formula of the thickness of grain boundaries at various temperatures are obtained. In total, Deff and DGBs obtained in the present study agree with literature results, and a comprehensive result of diffusivities related to the grain size is presented.

Individual variation in growth and physiology of symbionts in response to temperature

In many cases, understanding species level responses to climate change requires understanding variation among individuals in response to such change. For species with strong symbiotic relationships, such as many coral reef species, genetic variation in symbiont responses to temperature may affect the response to increased ocean temperatures. To assess variation among symbiont genotypes, we examined the population dynamics and physiological responses of genotypes of Breviolum antillogorgium in response to increased temperature. We found broad temperature tolerance across genotypes, with all genotypes showing positive growth at 26, 30, and 32 C. Genotypes differed in the magnitude of the response of growth rate and carrying capacity to increasing temperature, suggesting that natural selection could favor different genotypes at different temperatures. However, the historical temperature at which genotypes were reared was not a good predictor of temperature response, suggesting a lack of adaptation to temperature over hundreds of generations. We found increased photosynthetic rates and decreased respiration rates with increasing temperature, and differences in physiology among genotypes, but found no significant differences in the response of different genotypes to temperature. In species with such broad thermal tolerance, selection experiments on symbionts outside of the host may not yield results sufficient for evolutionary rescue from climate change.

Homogenization Modes Effect on Mechanical Properties and Corrosive Characteristics of the Rolled Products from Al-Mg (1570) Aluminum Alloy with Addition of Scandium and Zirconium

Objective of the study: study of various homogenization modes effects on mechanical and corrosive properties of rolled sheets from Al-Mg system alloy 1570 with additions of zirconium and scandium transition metals. The sheets were produced in laboratory conditions from the ingot, cast in production DC mold based on the commercial production practices and treatment modes. 4 homogenization modes, 2 tempers H12 and H321, and several modes of stabilization annealing in the temperature range from 240 °C to 325 °C have been reviewed. The samples have been comprehensively examined using optic and electron scanning microscope, mechanical properties were achieved by break test in compliance with ISO 6892-1, corrosion was examined using ASTM G66 and G67 standards. The curve of 1570 alloy sheets softening as the function of annealing temperature was constructed. It was demonstrated that the increasing temperature effect during homogenization leads to strength properties decrease and corrosion resistance improvement due to interdendritic segregation elimination. Among analyzed homogenization modes, 360 - 380 °C - 6 h mode is established as the most practical, and the sheets. produced without stabilization annealing, occurred to be the most resistant to exfoliation corrosion. The sheets, subjected to annealing at 260 °C - 2 h, show no traces of layer corrosion, but have pit corrosion locations rated as «PC» based on ASTM G-66 classification, such rating is unacceptable for the manufacture of products for use in the marine environment.

Examining Impacts of Acidic Bath Temperature on Nano-Synthesized Lead Selenide Thin Films for the Application of Solar Cells

The influence of bath temperature on nano-manufactured PbSe (lead selenide) films was successfully generated by utilizing CBD on the acid solution’s metal surface tool. Pb (NO3)2 was employed as a lead ion source as a precursor, while Na2O4Se was used as a selenide ion source. The XRD characterization revealed that the prepared samples are the property of crystalline structure (111), (101), (100), and (110) Miller indices. The scanning electron microscope indicated that the particles have a rock-like shape. There was a decrement of energy bandgap that is from 2.4 eV to 1.2 eV with increasing temperature 20°C–85°C. Thin films prepared at 85°C revealed the best polycrystal structure as well as homogeneously dispersed on the substrate at superior particle scales. The photoluminescence spectrophotometer witnessed that as the temperature of the solution bath increases from 20°C to 85°C, the average strength of PL emission of the film decreases. The maximum photoluminescence strength predominantly exists at high temperatures because of self-trapped exciton recombination, formed from O2 vacancy and particle size what we call defect centres, for the deposited thin films at 45°C and 85°C. Therefore, the finest solution temperature is 85°C.

Density-functional-theory predictions of mechanical behaviour and thermal properties as well as experimental hardness of the Ga-bilayer Mo2Ga2C

Mo2Ga2C is a new MAX phase with a stacking Ga-bilayer as well as possible unusual properties. To understand this unique MAX phase structure and promote possible future applications, the structure, chemical bonding, and mechanical and thermodynamic properties of Mo2Ga2C were investigated by first-principles. Using the “bond stiffness” model, the strongest covalent bonding (1162 GPa) was formed between Mo and C atoms in Mo2Ga2C, while the weakest Ga-Ga (389 GPa) bonding was formed between two Ga-atomic layers, different from other typical MAX phases. The ratio of the bond stiffness of the weakest bond to the strongest bond (0.33) was lower than 1/2, indicating the high damage tolerance and fracture toughness of Mo2Ga2C, which was confirmed by indentation without any cracks. The high-temperature heat capacity and thermal expansion of Mo2Ga2C were calculated in the framework of quasi-harmonic approximation from 0 to 1300 K. Because of the metal-like electronic structure, the electronic excitation contribution became more significant with increasing temperature above 300 K.

Long-Term Dynamic of Cold Stress during Heading and Flowering Stage and Its Effects on Rice Growth in China

Short episodes of low-temperature stress during reproductive stages can cause significant crop yield losses, but our understanding of the dynamics of extreme cold events and their impact on rice growth and yield in the past and present climate remains limited. In this study, by analyzing historical climate, phenology and yield component data, the spatial and temporal variability of cold stress during the rice heading and flowering stages and its impact on rice growth and yield in China was characterized. The results showed that cold stress was unevenly distributed throughout the study region, with the most severe events observed in the Yunnan Plateau with altitudes higher than 1800 m. With the increasing temperature, a significant decreasing trend in cold stress was observed across most of the three ecoregions after the 1970s. However, the phenological-shift effects with the prolonged growing period during the heading and flowering stages have slowed down the cold stress decreasing trend and led to an underestimation of the magnitude of cold stress events. Meanwhile, cold stress during heading and flowering will still be a potential threat to rice production. The cold stress-induced yield loss is related to both the intensification of extreme cold stress and the contribution of related components to yield in the three regions.

Combination of Methyl from Methane Early Cracking: A Possible Mechanism for Carbon Isotopic Reversal of Overmature Natural Gas

In this study, a methane (CH4) cracking experiment in the temperature range of 425–800°C is presented. The experimental result shows that there are some alkane and alkene generation during CH4 cracking, in addition to hydrogen (H2). Moreover, the hydrocarbon gas displays carbon isotopic reversal ( δ 13 C 1 > δ 13 C 2 ) below 700°C, while solid carbon appears on the inner wall of the gold tube above 700°C. The variation in experimental products (including gas and solid carbon) with increasing temperature suggests that CH4 does not crack into carbon and H2 directly during its cracking, but first cracks into methyl (CH3⋅) and proton (H+) groups. CH3⋅ shares depleted 13C for preferential bond cleavage in 12C–H rather than 13C–H. CH3⋅ combination leads to depletion of 13C in heavy gas and further causes the carbon isotopic reversal ( δ 13 C 1 > δ 13 C 2 ) of hydrocarbon gas. Geological analysis of the experimental data indicates that the amount of heavy gas formed by the combination of CH3⋅ from CH4 early cracking and with depleted 13C is so little that can be masked by the bulk heavy gas from organic matter (OM) and with enriched 13C at R o < 2.5 % . Thus, natural gas shows normal isotope distribution ( δ 13 C 1 < δ 13 C 2 ) in this maturity stage. CH3⋅ combination (or CH4 polymerization) intensifies on exhaustion gas generation from OM in the maturity range of R o > 2.5 % . Therefore, the carbon isotopic reversal of natural gas appears at the overmature stage. CH4 polymerization is a possible mechanism for carbon isotopic reversal of overmature natural gas. The experimental results indicate that although CH4 might have start cracking at R o > 2.5 % , but it cracks substantially above 6.0% R o in actual geological settings.