Search

In this study, methionine sulfoxide (MetO) was identified as an active metabolite that suppresses adipogenesis after screening obese individuals versus the normal population. MetO suppressed the gene and protein expression of CCAAT/enhancer binding protein (C/EBP) α, adipocyte fatty acid binding protein 4 (FABP4), and the nuclear receptor peroxisome proliferator-activated receptor γ (PPARγ) during human preadipocyte (HPA) differentiation. Adipogenesis decreased following MetO treatment; however, the preadipocyte number, proliferation, and apoptosis were unaffected. The activity of phosphorylated extracellular signal-related kinase (P-ERK) of the mitogen-activated protein kinase (MAPK) pathway was significantly inhibited in HPA after MetO treatment. Furthermore, treatment of preadipocytes with the selective P-ERK1/2 agonist Ro 67-7476 abolished the effect of MetO against adipogenesis suggesting that MetO function is dependent on the MAPK pathway. The mechanistic insights of adipogenesis suppression by MetO presented in this study shows its potential as an antiobesity drug.

The surface properties of fused silica (FS) change after H2O2 treatment, but the surface and subsurface damage behaviors and their mechanisms under various physical contact conditions have not been elucidated yet. This work investigated the effect of H2O2 treatment on mechanical and mechanochemical properties of FS surface. The results show that the hydrophilicity and adsorbed water film thickness of the FS surface increase with the concentration of H2O2 solution. The surface damage, nanowear, and subsurface deformation of FS caused by indentation increase with the concentration of H2O2 solution, while the nanohardness and reduced modulus decrease. Further analysis revealed that the water activity on the FS surface plays a critical role in reducing the mechanical and mechanochemical properties. In addition, the treatment with H2O2 solution on the FS surface shows a weakly corrosive effect, which implies the H2O2 treatment can be an alternative method to remove the surface defects on FS optics.

In graph G G , a vertex dominates itself and its neighbors. A subset S ⊆ V ( G ) S\subseteq V\left(G) is said to be a double-dominating set of G G if S S dominates every vertex of G G at least twice. The double domination number γ × 2 ( G ) {\gamma }_{\times 2}\left(G) is the minimum cardinality of a double dominating set of G G . We show that if G G is a maximal outerplanar graph on n ≥ 3 n\ge 3 vertices, then γ × 2 ( G ) ≤ 2 n 3 {\gamma }_{\times 2}\left(G)\le ⌊\frac{2n}{3}⌋ . Further, if n ≥ 4 n\ge 4 , then γ × 2 ( G ) ≤ min n + t 2 , n − t {\gamma }_{\times 2}\left(G)\le \min \left\{⌊\frac{n+t}{2}⌋,n-t\right\} , where t t is the number of vertices of degree 2 in G G . These bounds are shown to be tight. In addition, we also study the case that G G is a striped maximal outerplanar graph.

The rapid industrial development calls for alloys that possess higher comprehensive properties. In this study, the effect of micro-alloying La addition on the precipitation behavior during artificial aging as well as the mechanical properties and electrical conductivity of Al-Mg-Si alloys were investigated by thermal analysis, microstructural characterizations and properties tests. The results demonstrated that micro-alloying La addition does not change the whole precipitation sequence during the artificial aging of Al-Mg-Si alloys as well as the atomic structure of the precipitates. However, the higher La-vacancy binding energy as well as the strong La-Si and La-Mg interactions can decrease the solubility of Si and Mg in the Al matrix and the β″ precipitation activation energy from 89.9 to 76.7 kJ/mol, leading to the improvement of the strength and electrical conductivity of Al-Mg-Si alloys simultaneously. The microstructural features affecting the strength and electrical conductivity were theoretically discussed in terms of the La addition.

There are few reports about symmetrical electrodes based on BaFeO3−δ-parent oxides. In this study, a novel Ba0.95La0.05Fe0.9Nb0.1O3−δ (BLFN) ceramic electrode is developed for use as an electrode for symmetrical solid oxide fuel cells (S-SOFCs). The X-ray diffraction (XRD) result reveals that the Nb dopant can keep the cubic perovskite structure of the BLFN material stable against wet hydrogen reduction due to the steady valence state of Nb and the strong Nb–O bond. The maximum electrical conductivities of the BLFN material are 4.91 and 1.58 S cm−1 in air and 5% H2/Ar, respectively. Electrochemical impedance spectra (EIS) studies discovered the outstanding catalytic activity of the BLFN electrode toward the hydrogen oxidation reaction and oxygen reduction reaction. Polarization resistances at 750 °C are as low as 0.055 and 0.148 Ω cm2 in air and hydrogen, respectively, far lower than those of reported symmetrical electrodes. The analysis of the distribution of relaxation times (DRT) for EIS under different PO2 and PH2 indicates that the rate-limiting steps of the BLFN electrode are determined by the hydrogen adsorption/dissociation process for the anode and the dissociation of adsorbed oxygen for the cathode, respectively. The single S-SOFC achieves a high peak power density of 581 mW cm−2 and low polarization resistance of 0.096 Ω cm2 at 800 °C. These results indicate that the BLFN material is a potential candidate for S-SOFC electrode applications.

Lithium aluminosilicate glass-ceramics (LAS GCs) are ideal shell materials for mobile phones, however, the mechanical properties of LAS GCs are comparatively lower than that of other shell materials. In this work, the impact of TiO2/(TiO2 + ZrO2) ratio on properties of LAS GCs was studied and the ion-exchange methods were applied to improve the mechanical properties of LAS GCs. The results show that LAS GCs with TiO2/(TiO2 + ZrO2) = 1/2 exhibit the best flexural strength (109 MPa) and Vickers hardness (525 Kg/mm2). The as-prepared glass was nucleated at 560 °C for 1 h and crystallized at 720 °C for 0.5 h. The main crystalline phases of LAS GCs are β-quartz solid solution, β-spodumene solid solution, and Li2SiO3. Moreover, the flexural strength and Vickers hardness of LAS GCs with TiO2/(TiO2 + ZrO2) = 1/2 further increased to 356 MPa and 838 Kg/mm2 after an ion-exchange at 420 °C for 6 h in pure KNO3 molten salt. The LAS GCs with enhanced mechanical strength have the potential to be applied as mobile phone back panels.

Rice blast is one of the major rice diseases recognized in the world, and it is also the most serious rice disease in Northeast China. This study is based on the natural disease in the field, using a six-rotor drone equipped with a six-channel multi-spectral camera Micro-MCA6 Snap to obtain multi-spectral data of the diseased field. According to the results of the canopy scale research and applying the variance analysis method, 19 characteristic spectra are selected. The regional scale rice panicle blast classification models were constructed by three classification methods of stepwise linear discriminant analysis, support vector machine and neural network respectively. The experimental results showed that the recognition accuracy of various models was above 87.5%. The best classification effect was the discriminant analysis model. It only selected 3 features to achieve a cross-validation accuracy of 90.6% and a predicted sample recognition accuracy of 92.8%.

Viscosity at the liquidus temperature (TL), ηL, is a critical parameter for the design of new glasses, particularly for industrial glass production where crystallization must be suppressed. However, a direct viscometric determination of ηL for a glass-forming system is difficult due to crystallization. Here we propose an alternative approach for determining ηL through differential scanning calorimetry (DSC). Specifically, DSC is used to measure both the viscosity curve and liquidus temperature of a glass-forming system and then derive its ηL value. The ηL values determined using DSC are found to be in excellent agreement with those measured through viscometry. The DSC approach is applicable to various glass-forming systems covering a wide range of fragilities and ηL values spanning over five orders of magnitude. Other advantages of this approach are its accuracy and small sample requirements.

Only a few glass structure relaxation parameters are applicable for finite element simulation. The structural relaxation characteristics of K-LCV161 glass were described using the Tool–Narayanaswamy–Moynihan (TNM) model in multiple differential scanning calorimetry(DSC) experiments. First, the proposed method of narrowing the fitting parameter range was based on the influence of TNM model parameters on DSC curve. The position of the DSC curve peak is affected by changing Δ h * / R and A, the height of the DSC curve peak is affected by changing x and β. The least squares fitting method to solve the TNM model parameters was then systematically presented systematically presented, and the following results were obtained: ∆h*/R = 52,394.91 K, A = 6.15e−31 s, x = 0.77, β=0.70. Finally, the volume change of K-LCV161 glass during cooling was predicted by using the thermal expansion and structural relaxation models, and the difference between these two models was approximately 23%.

Herein, we systematically study the crystallization behaviors and critical nucleation rates (qc*) of mixed alkaline earth basalt glasses and melts. Based on the change of Raman spectra, the higher Tg of the Ca-containing endmember glass compared to the Mg-containing one could be mainly ascribed to the variance of medium-range order rather than the polymerization of the glassy network. According to the evolution of crystal behaviors with the replacement of Mg by Ca, we clarify how mixed alkali earth effects influence the crystallization process and particularly the glass forming ability. In addition, Raman spectral variations with Ca and Mg interchange imply that the basalt melt with the minimum qc* is closely correlated to the topological structure rather than the viscosity at Tm. Compared with that of the calcium-containing glass, the higher glass-forming ability of magnesium-containing endmember sample should be related to the medium-range structural order and higher polymerization degree.

The mixed alkali effect, the deviation from expected linear property changes when alkali ions are mixed in a glass, remains a point of contention in the glass community. While several earlier models have been proposed to explain mixed alkali effects on ionic motion, models based on or containing discussion of structural aspects of mixed-alkali glasses remain rare by comparison. However, the transition-range viscosity depression effect is many orders in magnitude for mixed-alkali glasses, and the original observation of the effect (then known as the Thermometer Effect) concerned the highly anomalous temperature dependence of stress and structural relaxation time constants. With this in mind, a new structural model based on topological constraint theory is proposed herein which elucidates the origin of the mixed alkali effect as a consequence of network strain due to differing cation radii. Discussion of literature models and data alongside new molecular dynamics simulations and experimental data are presented in support of the model, with good agreement.

The elastic response of glass is one of its most important properties for a wide range of applications in architecture, transportation, information display, and healthcare. Unfortunately, there is currently no model to predict quantitatively accurate values of elastic moduli from the underlying network topology of the glass. Here we introduce a topological model to calculate the Young's modulus of glass in terms of the free energy density of rigid constraints in the network. The model shows quantitatively accurate agreement with glasses across a variety of compositional families. More remarkably, the variation of modulus with temperature can also be predicted by accounting for the temperature dependence of the constraints, including the approach to the viscoelastic region near the glass transition. Keywords: Disordered solids, Glasses, Elasticity, Elastic moduli

Differential scanning calorimetry (DSC) is a powerful tool to address some of the most challenging issues in glass science and technology, such as the nonequilibrium nature of the glassy state and the detailed thermodynamics and kinetics of glass-forming systems during glass transition, relaxation, rejuvenation, polyamorphic transition, and crystallization. The utility of the DSC technique spans across all glass-forming chemistries, including oxide, chalcogenide, metallic, and organic systems, as well as recently discovered metal-organic framework glass-forming systems. Here we present a comprehensive review of the many applications of DSC in glass science with focus on glass transition, relaxation, polyamorphism, and crystallization phenomena. We also emphasize recent advances in DSC characterization technology, including flash DSC and temperature-modulated DSC. This review demonstrates how DSC studies have led to a multitude of relevant advances in the understanding of glass physics, chemistry, and even technology.

The effects of rare earth element on the microstructures, tensile properties and electrical properties of aluminum alloys have brought about widespread interesting in the last few decades. However, contradictory results are usually reported, and there is little research concerning the effect law of trace lanthanum (the addition is below 0.1 wt%) on the as-cast microstructures, electrical conductivity and the tensile properties of 8176 aluminum alloy which is one of the most widely used aluminum conductor alloy. In this work, solidification experiments were performed with 8176 aluminum alloy and the effects of lanthanum addition was investigated. The results demonstrated that the lanthanum addition can promote the refinement of the alpha Al grains, the modification of Al13Fe4 intermetallic phase. The elongation and electrical conductivity simultaneously enhance with lanthanum addition when the additive amount is less than 0.08%, while the elongation decreases when the additive amount reaches to 0.1% due to the formation of intermetallic phase. The enhancement of the elongation is mainly ascribed to the modification of Al13Fe4 intermetallic phase, the enhancement of the electrical conductivity is attributed to the reduction of solid solubility of Si and Fe elements in Al matrix. These results indicate that the addition of micro-alloying element lanthanum is a prospective method for simultaneously elevating the electrical conductivity and tensile properties of the 8176 aluminum alloy.

As one of the most important properties of glass-forming liquids, viscosity has drawn significant attention in both glass manufacturing and fundamental research. We review the recent scientific progress in viscosity of glass-forming systems, including both the liquid and glassy states. After the Vogel-Fulcher-Tammann (VFT) equation was introduced, many more efforts have been made to develop more accurate models to describe the temperature dependence of viscosity. In addition to the VFT equation, we also discuss three other viscosity models, viz., the Adam-Gibbs, Avramov-Milchev, and Mauro-Yue-Ellison-Gupta-Allan models. We compare the four viscosity models in terms of their theoretical underpinnings and ability to fit measured viscosity curves. The concept of fragility and the universality of the high-temperature viscosity limit are also discussed. Temperature-dependent constraint theory is introduced in detail as a powerful tool for predicting the composition dependence of viscosity. Some examples of the application of this approach to predict the glass transition temperature and fragility of various glass systems are shown. Topological constraint theory is not only of scientific interest, but also has important industrial applicability. We also discuss the thermal history dependence of viscosity in the glassy state. Some phenomenological models are briefly reviewed, while the main focus is given to the modified Mauro-Allan-Potuzak model, which can accurately predict the nonequilibrium viscosity as a function of temperature, thermal history, and composition. The correlation of viscosity with elasticity is described in terms of the shoving model. Some theoretical implications of the various viscosity models are discussed, including the concepts of the Kauzmann paradox and the ideal glass transition. Some of the evidence against the existence of these phenomena are discussed. We also review the link between glass relaxation and viscosity, that is, emphasizing that the viscosity equations presented in this review can also be used to model different types of relaxation effects based on the Maxwell relation.

The mixed alkaline earth effect (MAEE) is important for several families of industrial borosilicate and aluminosilicate glasses, including glasses used in pharmaceutical packaging and as substrates for flat panel displays. Despite the technological importance of the mixed alkaline earth effect, the physical origin of this phenomenon is not well understood, and there is currently no model to offer quantitative prediction of the effect. In this work, the MAEE is studied both experimentally and through modeling in a series of boroaluminosilicate glasses with systematic substitution of CaO with MgO. The network structure is characterized by magic angle spinning nuclear magnetic resonance (MAS NMR) analyses of 27Al, 11B, 29Si, and 23Na. Molecular dynamics (MD) simulations are conducted to simulate the glass structures and calculate the evolution of the bond angle distributions with composition. Based on the structural data, a topological constraint model is proposed to capture the MAEE on glass transition temperature (Tg), liquid fragility index (m), and Young's modulus (E) of the glasses. Results of the topological constraint model are in good quantitative agreement with experimental data. The success of the constraint model confirms that the mixed alkaline earth effect is the result of a shift in angle around oxygen in the cation-oxygen-cation bond in the glass network. This is related to the constraint strength that ultimately governs the nonlinear property variation.

Fiber spinnability is the ability of a glass-forming melt to be steadily stretched and spun into defect-free fiber filaments. However, its quantification has not been well established owing to many controlling factors such as melt fragility, melt strength, surface tension, liquidus temperature, liquidus viscosity, and crystallization. To understand and quantify the fiber spinnability of a glass melt, we consider two key aspects: fiberizing viscosity window and melt stability. The fiberizing viscosity window is defined by the upper and lower viscosity limits. Fibers rupture above the upper viscosity limit, whereas a stable melt stream cannot form below the lower limit (ηlow). We introduce a simple parameter to quantify fiber spinnability, namely, Kfib=ηL/ηlow, where ηL is the viscosity at liquidus temperature (TL). A fiber can only form if Kfib>1. To quantify melt stability we propose the parameter of S=(TL-TC)/(TL-Tg), where TL and TC are the liquidus temperature, and the onset temperature of melt crystallization during cooling, respectively. Both parameters (Kfib and S) are important for a rational design of glass fiber compositions, and fiberizing process. We use two basalt melts as examples of this study to demonstrate the high sensitivity of fiber spinnability to a minor variation in chemical composition of melts.

Topological constraint theory has previously been applied to predict the composition dependence of glass hardness for a variety of different composition families. Some recent findings have cast doubt on the correlation between glass hardness and the number of rigid constraints per atom in silicate glasses. In this letter, we revisit the prediction of hardness for borosilicate and phosphosilicate glasses using four different types of constraint counting approaches: total number of constraints per atom, angular constraints per atom, total constraint density, and angular constraint density. We find that the counting approaches using total constraint density or angular constraint density give an improved prediction of glass hardness. We therefore conclude that glass hardness is governed by the density of rigid constraints under an indenter, rather than by the number of rigid constraints per atom.

The liquid fragility index ( m vis ) describes the rate of viscosity change of a glass-forming liquid with temperature at the glass transition temperature ( T g ), which is very important for understanding liquid dynamics and the glass transition itself. Fragility can be directly determined using viscosity measurements. However, due to various technical complications with determining viscosity, alternative methods to obtain fragility are needed. One simple method is based on measurement of the calorimetric fragility index ( m DSC ), i.e., the changing rate of fictive temperature ( T f ) with heating (cooling) rate in a small T f range around T g . The crucial question is how m DSC is quantitatively related to m vis . Here, we establish this relation by performing both dynamic and calorimetric measurements on some selected glass compositions covering a wide range of liquid fragilities. The results show that m DSC deviates systematically from m vis . The deviation is attributed to the Arrhenian approximation of the log(1/ q c ) ~ T g / T f relationship in the glass transition range. We have developed an empirical model to quantify the deviation, by which m vis can be well predicted from m DSC across a large range of fragilities. Combined with the high- T viscosity limit (10 –2.93 Pa·s), we are able to obtain the entire viscosity curve of a glass-forming liquid by only performing DSC measurements.

Sodium tracer diffusion coefficients, D*Na, have been measured using the radioactive isotope Na-22 in sodium boroaluminosilicate (NBAS) glasses containing either a small amount of As2O3 or Fe2O3. The chemical compositions of the first type of glasses are given by the formula [(Na2O)0.71(Fe2O3)0.05(B2O3)0.24]0.2[(SiO2)x(Al2O3)1 − x]0.8 and those of the second type of glasses correspond to the formula [(Na2O)0.73(B2O3)0.24(As2O3)0.03]0.18[(SiO2)x(Al2O3)1 − x]0.82. Tracer diffusion measurements were performed at different temperatures between 198 and 350 °C. Pre-annealing of the glass samples at their glass transition temperatures in common air was found to lead to changes in the values of sodium tracer diffusion coefficients. For the NBAS glasses containing Fe2O3, after pre-annealing for 5 h, the activation enthalpy derived for the sodium tracer diffusion increases almost linearly from 57.5 to 71.3 kJ/mol with a decrease in the alumina content while the pre-exponential factor of the sodium tracer diffusion coefficient increases from 2.1 · 10− 4 to 5.3 · 10− 4 cm2/s. For the iron-free NBAS glasses pre-annealed for 5 h, the activation enthalpy varies between 63.9 and 71.4 kJ/mol while the pre-exponential factor varies between 1.5 · 10− 4 and 1.2 · 10− 3 cm2/s. In addition, it was observed that the considered glasses take up water when annealed at 300 °C in wet air with PH2O = 474 mbar.

The complicated structural speciation in boroaluminosilicate glasses leads to a mixed network former effect yielding nonlinear variation in many macroscopic properties as a function of chemical composition. Here we study the composition–structure–property relationships in a series of sodium boroaluminosilicate glasses from peralkaline to peraluminous compositions by substituting Al 2 O 3 for SiO 2 . Our results reveal a pronounced change in all the measured physical properties (density, elastic moduli, hardness, glass transition temperature, and liquid fragility) around [Al 2 O 3 ]–[Na 2 O] = 0. The structural origin of this change is elucidated through nuclear magnetic resonance analyses and topological considerations. Furthermore, we find that addition of 1 mol% Fe 2 O 3 exerts a complicated impact on the measured properties.

We investigate the composition dependence of glass-forming ability (GFA) of a series of iron-containing soda lime borate liquids by substituting Na 2 O for B 2 O 3 . We have characterized GFA by measuring the glass stability against crystallization using a differential scanning calorimeter (DSC). The results show that the GFA decreases when substituting Na 2 O for B 2 O 3 . Moreover, we find that there is no direct link between the kinetic fragility and GFA for the soda lime borate series studied herein. We have also discovered and clarified a striking thermal history dependence of the glass stability against crystallization. In particular, the two glasses containing 20 and 25 Na 2 O mol% do not exhibit crystallization exotherms during the second DSC upscan at 10 and 20 K/min following prior slow (10 and 20 K/min) downscans. This indicates that the glass stability of these compositions can be enhanced by cooling their melts to the glassy state slowly, before any reheating. We explain this phenomenon in terms of the thermal history dependence of boron speciation.