Vickers Micromechanical Indentation Studies of Barium Oxalate Dihydrate Crystals

Vickers microhardness measurements have been carried out on gel grown single crystals of barium oxalate dihydrate. The dependence of hardness on indentation load has been described. Attempts have also been made to understand the cracks developed around the micro indentation. The material chipping off and median vents observed around indentation figures have been discussed. Also explained are the fracture at high indentation load. The average load independent hardness value is 58.27 kg · mm².     

Media Supplementation with Mannitol and Biotin Enhances Squalene Production of Thraustochytrium ATCC 26185 through Increased Glucose Uptake and Antioxidative Mechanisms

Media supplementation with exogenous chemicals is known to stimulate the accumulation of important lipids produced by microalgae and thraustochytrids. However, the roles of exogenous chemicals in promoting and preserving the terpenoids pool of thraustochytrids have been rarely investigated. Here, we realized the effects of two media supplements—mannitol and biotin—on the biomass and squalene production by a thraustochytrid strain (Thraustochytrium sp. ATCC 26185) and elucidated their mechanism of action. A significant change in the biomass was not evident with the exogenous addition of these supplements. However, with mannitol (1 g/L) supplementation, the ATCC 26185 culture achieved the best concentration (642 ± 13.6 mg/L) and yield (72.9 ± 9.6 mg/g) of squalene, which were 1.5-fold that of the control culture (non-supplemented). Similarly, with biotin supplementation (0.15 mg/L), the culture showed 459 ± 2.9 g/L and 55.7 ± 3.2 mg/g of squalene concentration and yield, respectively. The glucose uptake rate at 24 h of fermentation increased markedly with mannitol (0.31 g/Lh⁻¹) or biotin (0.26 g/Lh⁻¹) supplemented culture compared with non-supplemented culture (0.09 g/Lh⁻¹). In addition, the reactive oxygen species (ROS) level of culture supplemented with mannitol remained alleviated during the entire period of fermentation while it alleviated after 24 h with biotin supplementation. The ∆ROS with mannitol was better compared with biotin supplementation. The total antioxidant capacity (T-AOC) of the supplemented culture was more than 50% during the late stage (72–96 h) of fermentation. Our study provides the potential of mannitol and biotin to enhance squalene yield and the first lines of experimental evidence for their protective role against oxidative stress during the culture of thraustochytrids.     

Microhardness investigations on gel-grown barium cadmium oxalate mixed crystals

Microhardness characteristics of barium-cadmium oxalate crystals were undertaken using the indentation technique and the results there of are reported. The observed results were compared with the microhardness values of barium oxalate dihydrate and cadmium oxalate trihydrate crystals. The indentation induced cracks etched in 1N HCl reveal the surface of the dislocation pattern arround indentation mark. The mixed crystals show higher values of microhardness than the components barium oxalate dihydrate and cadmium oxalate trihydrate crystals.     

磁_微极广义热弹性介质中轴对称变形的弹性动力学

The present investigation is concerned with an axi-symmetric problem in the electromagnetic micropolar thermoelastic half-space whose surface is subjected to the mechanical or thermal source. Laplace and Hankel transform techniques are used to solve the problem. Various types of sources are taken to illustrate the utility of the approach. Integral transforms are inverted by using a numerical technique to obtain the components of stresses, temperature distribution, and induced electric and magnetic fields. The expressions of these quantities are illustrated graphically to depict the magnetic effect for two different generalized thermoelasticity theories, i.e., Lord and Shulman （L-S theory） and Green and Lindsay （G-L theory）. Some particular interesting cases are also deduced from the present investigation.     

Propagation of Lamb waves in transversely isotropic thermoelastic diffusive plate

The constitutive relations and field equations for anisotropic generalized thermoelastic diffusion are derived and deduced for a particular type of anisotropy, i.e. transverse isotropy. Green and Lindsay (GL) theory, in which, thermodiffusion and thermodiffusion–mechanical relaxations are governed by four different time constants, is selected for study. The propagation of plane harmonic thermoelastic diffusive waves in a homogeneous, transversely isotropic, elastic plate of finite width is studied, in the context of generalized theory of thermoelastic diffusion. According to the characteristic equation, three quasi-longitudinal waves namely, quasi-elastodiffusive (QED-mode), quasi-massdiffusive (QMD-mode) and quasi-thermodiffusive (QTD-mode) can propagate in addition to quasi-transverse waves (QSV-mode) and the purely quasi-transverse motion (QSH-mode), which is not affected by thermal and diffusion vibrations, gets decoupled from the rest of the motion of wave propagation. The secular equations corresponding to the symmetric and skew symmetric modes of the plate are derived. The amplitudes of displacements, temperature change and concentration for symmetric and skew symmetric modes of vibration of plate are computed numerically. Anisotropy and diffusion effects on the phase velocity, attenuation coefficient and amplitudes of wave propagation are presented graphically in order to illustrate and compare the analytically results. Some special cases of frequency equation are also deduced from the existing results.     

X-ray diffraction study of the effects of boron on occurrence of deformation faults in Ni3Al alloy

Ni₃Al and Ni₃Al alloys containing varying amounts of boron in L1₂ phase were prepared. All the samples were suitably annealed and then cold-worked by hand filing. X-ray diffraction data are collected on annealed and cold-worked samples. The deformation fault probabilities have been evaluated by two methods, viz. peak shift analysis of powder pattern X-ray reflections of annealed and cold-worked samples, and lattice parameter change between annealed and corresponding cold-worked samples. The values obtained by both the methods are in reasonable agreement. It has been found that the deformation fault probability of Ni₃Al and Ni₃Al containing boron alloys are very high compared to Ag and Cu base alloys. Further the deformation fault probability of Ni₃Al is more sensitive to boron addition. It has been found that at least 1.22 at. % of boron goes into the Ni₃Al lattice.     

Some observations on melt-grown cadmium iodide crystals

Single crystals of richly polytypic compound cadmium iodide have been grown using a zone-refining system. The frequent appearance of cracks in the grown crystals has been attributed to the thermal stresses and the presence of impurities. Structure of all the crystals has been found to be of the type 4H.     

萤火虫生物发光中加氧反应机理的理论研究

萤火虫生物发光是最常见的生物发光,在生物和医药等领域已得到重要应用.发光过程涉及到其活体内的一系列复杂的化学反应.引起发光的起始反应是单重态荧光素分子与三重态氧气的加成反应.这是一个自旋禁阻的酶催化反应,通常效率很低,但萤火虫是目前将化学能转化为光能最高效的系统.这个自旋禁阻的反应为什么能高效率发生?实验研究认为该反应由单电子转移(SET)诱发而发生,但对反应的详细过程和机理并没有完整的描述.本工作通过理论计算,描述了该反应的完整过程,解释了这个自旋禁阻反应高效发生的原因.     

Status Quo on Graphene Electrode Catalysts for Improved Oxygen Reduction and Evolution Reactions in Li-Air Batteries

Reduced global warming is the goal of carbon neutrality. Therefore, batteries are considered to be the best alternatives to current fossil fuels and an icon of the emerging energy industry. Voltaic cells are one of the power sources more frequently employed than photovoltaic cells in vehicles, consumer electronics, energy storage systems, and medical equipment. The most adaptable voltaic cells are lithium-ion batteries, which have the potential to meet the eagerly anticipated demands of the power sector. Working to increase their power generating and storage capability is therefore a challenging area of scientific focus. Apart from typical Li-ion batteries, Li-Air (Li-O₂) batteries are expected to produce high theoretical power densities (3505 W h kg⁻¹), which are ten times greater than that of Li-ion batteries (387 W h kg⁻¹). On the other hand, there are many challenges to reaching their maximum power capacity. Due to the oxygen reduction reaction (ORR) and oxygen evolution reaction (OES), the cathode usually faces many problems. Designing robust structured catalytic electrode materials and optimizing the electrolytes to improve their ability is highly challenging. Graphene is a 2D material with a stable hexagonal carbon network with high surface area, electrical, thermal conductivity, and flexibility with excellent chemical stability that could be a robust electrode material for Li-O₂ batteries. In this review, we covered graphene-based Li-O₂ batteries along with their existing problems and updated advantages, with conclusions and future perspectives.     

A critical view on the environmental sustainability of biorefinery systems

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