Preparation of nanocrystalline MoSi2 with enhanced lithium storage by sol–gel and carbonthermal reduction method

Herein nanocrystalline MoSi₂ with enhanced lithium storage was successfully synthesized via a sol-gel and carbonthermal reduction method. Reduction of the gel mixture of Mo precursor and Si precursor by carbon at a desired temperature resulted in the formation of MoSi₂ nanoparticles. The gel mixture was obtained through the hydrolysis of TEOS and ammonium molybdate and the polymerization of hydrolysis products of TEOS. The reducing agent carbon was produced via decarburition of sucrose's hydrolysis products, which have been wrapped in the gel during its formation process. Addition of HCl to the mixed solution controlled the hydrolysis and polymerization rate, and enabled the formation of a gel mixture with homogeneously distributed hydrolysis products of ammonium molybdate, TEOS and sucrose. This achievement likely generates a novel route to synthesize non-oxide compounds such as silicide, carbide through the sol–gel and carbonthermal reduction process. In addition, the as-received MoSi₂ nanoparticles showed considerable activities in the reversible lithiation and delithiation process. When using as an anode for Li-ion batteries, MoSi₂ nanoparticles delivered a specific capacity of 325 mAh g^?1 at C/12 and showed an increasing capacity with cycling.     

Ablation mechanism of C/C–SiC and C/C–SiC–ZrC composites in hypersonic oxygen-enriched environment

In this study, C/C–SiC and C/C–SiC–ZrC composites were prepared via chemical vapor infiltration and polymer infiltration pyrolysis, and the ablation mechanism under hypersonic oxygen-rich environmental conditions was investigated. The C/C–SiC composites demonstrate an excellent ablation resistance in a hypersonic oxygen-rich environment with a relatively low temperature and speed of approximately 1800 K and 1100 m/s, respectively. It is only in the ablation center area with higher temperatures that a certain degree of thermochemical ablation was observed. The mass and linear ablation rates of C/C–SiC composites (0.027 g/s and 0.117 mm/s, respectively) showed a significant increase in a hypersonic oxygen-rich environment with a temperature and velocity of approximately 2050 K and 2000 m/s, respectively. The high-temperature ablation resistance of ZrC-modified C/C–SiC–ZrC composites improved significantly. However, the ZrC ceramic component had a considerable impact on the ablation resistance of the material. The structural integrity of C/C–20SiC–30ZrC composites was relatively high in hypersonic oxygen-rich environments with a jet temperature and velocity of 2050 K and 2000 m/s, respectively, and mass and linear ablation rates were 0.012 g/s and 0.015 mm/s, respectively. When the ZrC content increased by 40%, the ablation resistance of the composite reduced significantly, whereas the mass and linear ablation rates increased to 0.043 g/s and 0.130 mm/s, respectively.     

Hydrogen Peroxide Stimulates Dihydrotestosterone Release in C2C12 Myotubes: A New Perspective for Exercise-Related Muscle Steroidogenesis?

Skeletal muscle is a tissue that has recently been recognized for its ability to produce androgens under physiological conditions. The steroidogenesis process is known to be negatively influenced by reactive oxygen species (ROS) in reproductive Leydig and ovary cells, while their effect on muscle steroidogenesis is still an unexplored field. Muscle cells are continuously exposed to ROS, resulting from both their metabolic activity and the surrounding environment. Interestingly, the regulation of signaling pathways, induced by mild ROS levels, plays an important role in muscle fiber adaptation to exercise, in a process that also elicits a significant modulation in the hormonal response. The aim of the present study was to investigate whether ROS could influence steroidogenesis in skeletal muscle cells by evaluating the release of testosterone (T) and dihydrotestosterone (DHT), as well as the evaluation of the relative expression of the key steroidogenic enzymes 5α-reductase, 3β-hydroxysteroid dehydrogenase (HSD), 17β-HSD, and aromatase. C2C12 mouse myotubes were exposed to a non-cytotoxic concentration of hydrogen peroxide (H₂O₂), a condition intended to reproduce, in vitro, one of the main stimuli linked to the process of homeostasis and adaptation induced by exercise in skeletal muscle. Moreover, the influence of tadalafil (TAD), a phosphodiesterase 5 inhibitor (PDE5i) originally used to treat erectile dysfunction but often misused among athletes as a “performance-enhancing” drug, was evaluated in a single treatment or in combination with H₂O₂. Our data showed that a mild hydrogen peroxide exposure induced the release of DHT, but not T, and modulated the expression of the enzymes involved in steroidogenesis, while TAD treatment significantly reduced the H₂O₂-induced DHT release. This study adds a new piece of information about the adaptive skeletal muscle cell response to an oxidative environment, revealing that hydrogen peroxide plays an important role in activating muscle steroidogenesis.     

Encapsulation of TiO₂(B) nanowire cores into SnO₂/carbon nanoparticle shells and their high performance in lithium storage

TiO(2)(B)@SnO(2)/carbon hybrid nanowires have been synthesized by two simple hydrothermal processes and subsequent heat treatment in argon. The composite has a unique architecture, as its morphology consists of particles having a TiO(2)(B) nanowire core and a porous SnO(2)/carbon nanoparticle shell layer. The unique core/shell structure and chemical composition will be useful for many potential applications, including the lithium ion battery. The electrochemical results on the composite are presented to demonstrate the superior cycling performance and rate capability of the TiO(2)(B)@SnO(2)/carbon nanowires. This composite exhibits a high reversible capacity of ～669mAhg(-1), and excellent cycling stability, indicating that the composite is a promising anode material for Li-ion batteries.     

Sintering behavior and growth mechanism of β-TCP in nanocrystalline hydroxyapatite synthesized by mechanical alloying

Nanocrystalline carbonated HAp powder has been synthesized successfully within 2 h by mechanical alloying the stoichiometric mixture of CaCO₃, CaHPO₄·2H₂O at room temperature under open air. To observe the sintering behavior of HAp the as-milled sample is sintered at different temperatures. The amorphous HAp phase (~14 vol%) in as-synthesized sample transforms completely to crystalline HAp after sintering at 700 °C and after sintering the sample at 800 °C, the crystalline HAp partially transforms to β-TCP phase. Presence of low content of β-TCP phase in HAp powder could be useful in artificial hard tissue applications. Increase in sintering temperature up to 1000 °C results in enhancement of decomposition rate of HAp into β-TCP phase. Microstructure characterization in terms of lattice imperfections and relative phase abundances in non-sintered and all sintered samples are made both by analyzing the respective XRD patterns using Rietveld's structure refinement method as well as TEM images. The growth mechanism of β-TCP from crystalline HAp phase has been proposed based on structure and microstructure characterizations of sintered samples.     

Synthesis of graphene/α-Fe2O3 nanospindles by hydrothermal assembly and their lithium storage performance

Nanocomposite of graphene/α-Fe₂O₃ (G/α-Fe₂O₃) nanospindles was synthesized by a simple hydrothermal assembly method followed by thermal treatment. The α-Fe₂O₃ nanospindles were evenly enwrapped by the graphene nanosheets. When evaluated as an anode for Li-ion batteries (LIBs), the G/α-Fe₂O₃ nanocomposite showed enhanced cycling performance and rate capability compared to pure α-Fe₂O₃. G/α-Fe₂O₃ retained a reversible capacity of 607 mAh g^?1 after 100 cycles at 100 mA g^?1-, which is far higher than that (160 mAh g^?1) of α-Fe₂O₃. The superior electrochemical performance of G/α-Fe₂O₃ can be attributed to the protection effect of graphene nanosheets to accommodate the volume change of α-Fe₂O₃ during lithiation/delithiation.     

Frequency and Voltage Dependence of Interface States and Series Resistance in Ti/Au/p-Si Diodes with 100 μm and 200 μm Diameter Fabricated by Photolithography

Silicon - Ti/Au/p-Si diodes with the diameters of 100 and 200 μ m were fabricated by photolithographic technique. Capacitance–voltage (C–V) and conductance–voltage...     

Effect of polymer–nanoparticle interactions on the glass transition dynamics and the conductivity mechanism in polyurethane titanium dioxide nanocomposites

We report on the glass transition dynamics and the conductivity properties of a nanodielectric system composed of pre-synthesized TiO₂ nanoparticles embedded in thermoplastic polyurethane. Increase of TiO₂ loading results in enhanced segmental mobility of the composites and less steep temperature dependence, i.e., lower fragility index. The decrease in the fragility index and glass transition temperature is discussed based on the FTIR results. We observe different behavior of conductivity for temperatures above and below the glass transition temperature. At high temperatures the composites exhibit conductivity values more than 2 orders of magnitude higher than those in the pristine matrix. At the same time, at sub-T_g temperatures composites are characterized by superior electrical insulation properties compared to pristine matrix material. Such drastic temperature dependence of the conductivity/insulating ability of the flexible and light-weight, low-T_g composite material can be utilized in various applications including sensing and temperature switching materials.     

Hydrogen adsorption on M-ZSM-12 zeolite clusters (M = K,Na and Li): a density functional theory study

The molecular adsorption of hydrogen has been studied theoretically via DFT on additional framework with alkali metal atoms (K, Na and Li) in ZSM-12 zeolite. A 14T channel zeolite cluster model was used. Lewis acidity of alkali metals decreases with increasing atomic radius of alkali metal and H₂ adsorption. Adsorption enthalpy values were computed to be ?7.4 and ?5.1 kJ/mol on Li- and Na-ZSM-12 clusters, respectively. Hydrogen adsorption enthalpy values for Li- and Na-cases are meaningfully larger than the liquefaction enthalpy of hydrogen molecule. This designates that Li- and Na-ZSM-12 zeolites are potential cryoadsorbent materials for hydrogen storage.     

Stability of Tocopherol Homologs in Bulk Oils at 60°C Oxidation and Chlorophyll Photosensitization by the Action of Moisture

The effects of deuterium oxide (D₂O) on the stability of tocopherol homologs were evaluated in corn oil stored at 60°C or in the process of chlorophyll photosensitization. The degree of oxidation, changes in moisture, and the levels of tocopherol homologs were analyzed. The moisture content in corn oil incubated with deuterium-free water (H₂O) was significantly (P < 0.05) higher than that in corn oil incubated with D₂O. The presence of D₂O accelerated the rate of lipid oxidation in corn oil, irrespective of whether it has been oxidized at 60°C or has been photosensitized by chlorophyll. After exposure to either of the oxidative stresses, the stability of β + γ-tocopherols present in corn oil was enhanced in the presence of D₂O compared to corn oil incubated in the presence of H₂O, or control corn oil without the addition of moisture. However, the stability of α-tocopherol in corn oil incubated with D₂O was significantly lower after oxidation at 60°C compared to the other conditions (P < 0.05), whereas it was significantly higher than under the other conditions after chlorophyll photosensitization (P < 0.05). The moisture and type of oxidative stress, therefore, play important roles in the stability of tocopherol homologs in bulk oils.     

Measurement of Temperature and Concentration of OH Radicals in Combustion of Hydrogen and Ethanol by the Laser‐Induced Fluorescence Technique

Diffusion combustion of ethanol and hydrogen and homogeneous combustion of hydrogen–oxygen mixtures are studied by the laserinduced fluorescence technique in the linear regime and with signal saturation. Data on the flame temperature and OH concentration are obtained. The burning temperature of 3090 K for a stoichiometric O₂–H₂ mixture is in agreement with the known value. It is shown that the maximum concentrations of radicals in the hydrogen–air and stoichiometric hydrogen–oxygen flames are close to each other (4.4· 10¹⁶ cm^-3).     

In situ synthesis and interfacial bonding mechanism of SiC in MgO–SiC–C refractories

Adding SiC directly to MgO–C refractories possesses the disadvantages of low dispersion and interfacial bonding strength. Herein, the in situ synthesized SiC was introduced into the MgO–SiC–C refractories to maintain the original excellent performance of MgO–C refractories and reduce the carbon dissolution in molten steel. With the increase of Si and C content in raw materials, the morphology of SiC changed from whisker to network, whose growth mechanism was vapor–solid and vapor–liquid–solid. The network structure and uniform distribution of SiC improved the thermal shock resistance of MgO–SiC–C refractories. According to the analysis of molecular dynamics simulation by Materials Studio software, SiC strengthened the relationship between periclase and graphite to enhance the structure of the compound.     

Synthesis of ternary Li–Mn–O phase at a temperature of 260 ∘C and electrochemical lithium insertion into the oxide

A lithium–manganese oxide, Li _x MnO₂ (x=0.30.6), has been synthesized by heating a mixture (Li/Mn ratio=0.30.8) of electrolytic manganese dioxide (EMD) and LiNO₃ in air at moderate temperature, 260 C. The formation of the Li–Mn–O phase was confirmed by X-ray diffraction, atomic absorption and electrochemical measurements. Electrochemical properties of the Li–Mn–O were examined in LiClO₄-propylene carbonate electrolyte solution. About 0.3 Li in Li _x MnO₂ (x=0.30.6) was removed on initial charging, resulting in characteristic two discharge plateaus around 3.5V and 2.8V vs Li/Li⁺. The Li _x MnO₂ synthesized by heating at Li/Mn ratio=0.5 demonstrated higher discharge capacity, about 250mAh (g of oxide)^–1 initially, and better cyclability as a positive electrode for lithium secondary battery use as compared to EMD.     

Evolution of the oxidation process in olive oil triacylglycerol under accelerated storage conditions (40–60°C)

This paper presents an analysis of oxidation in olive oil TAG at different temperatures within a range of 40–60°C in darkness, as measured by the rate of formation of hydroperoxides, their decomposition products, and sensory and chemical flavor deterioration. At 60°C, the oxidation process was relatively fast, and all the indexes of the extent of oxidation behaved in a very similar way. The behaviors of the rate of formation of conjugated dienes (measured as the K ₂₃₂), of oxidized TAG (determined by HPLC), and of carbonyl compounds (measured as anisidine value) were very similar to that of the PV. The induction periods (IP) of the four indexes were less than 36 h. Nevertheless, the IP for K ₂₇₀ and the sum of oxidized TAG dimers and polymers were 5 d. At 50 and 40°C, the rate of formation of secondary oxidation products was lower. Residual linolenic acid or PUFA as determined by GC showed correlation coefficients higher than 0.999 with the Totox index at all of the assayed temperatures. The rancid recognition threshold corresponded to lower values of the oxidation indexes at lower temperature. Moreover, at all assayed temperatures, the rancidity threshold apparently coincided with the IP for the kinetics of 2,4-decadienal formation.     

Is competition between Li+ and Mg2+ the underlying theme in the proposed mechanisms for the pharmacological action of lithium salts in bipolar disorder?

Lithium salts have been in use for the treatment of bipolar disorder for more than 50 years, but their pharmacological mode of action remains a matter of conjecture. Li(+) and Mg(2+) share many physicochemical properties. Not surprisingly, many reported cellular targets for Li(+) action involve Mg(2+)-activated enzymes, which are inhibited by Li(+). In this Account, we describe results from our and other laboratories that suggest that a competition mechanism between Li(+) and Mg(2+) ions for Mg(2+)-binding sites in cellular components is the underlying theme in putative mechanisms of Li(+) action.     

Efficient treatment of salty organic wastewater by α-MnO2-N/C synergistic catalytic ozonation: Effect and mechanism

A novel and efficient α-MnO₂-N/C@active carbon (AC) catalyst was proposed and synthesized through a surface modification method based on imprinting process. Uniformly dispersed α-MnO₂ and N/C sites were constructed simultaneously and the competitive adsorption of metal precursors with nonmetal precursors was avoided. Conformational relationship of α-MnO₂-N/C@AC revealed that α-MnO₂ and graphite N were the main active sites, cleverly forming synergistic catalytic effect, which results in a good degradation effect for two actual printing and dyeing wastewater. The removal rate of chemical oxygen demand (COD) could reach 78% and 58% within 60 min, respectively, and it maintained stable after 20 repetitions without leaching of metal ions. Mechanistic investigation demonstrated that N/C sites rapidly adsorbed ozone to generate ·O₂⁻ and synergistically catalyzed with adjacent α-MnO₂ sites to further produce ·OH, significantly facilitating the generation of ·OH. This work provides a promising strategy to synthesize novel and efficient catalysts for ozone catalytic oxidation process.