(Ti0.25Zr0.25Nb0.25Ta0.25)C高熵陶瓷的制备、力学性能及氧化行为研究

本文通过对碳化物粉末进行放电等离子烧结(SPS),成功制备了(Ti_0.25Zr_0.25Nb_0.25Ta_0.25)C高熵陶瓷(HECs),系统研究了HECs的微观结构演变、力学性能和氧化行为。结果表明,单相HECs的形成温度为1 800 ℃,低于已报道的HECs烧结温度。1 900 ℃烧结的陶瓷晶粒细小,平均晶粒尺寸约7.5 μm,元素分布均匀,相对密度高达99.2%。1 800 ℃和1 900 ℃烧结的HECs的室温显微硬度值分别为30.9 GPa和33.2 GPa,断裂韧性值分别为(4.6±0.24) MPa·m^1/2和(4.5±0.31) MPa·m^1/2,高于大多数已报道的HECs。原位高温纳米压痕试验结果表明,HECs的硬度随温度的升高而降低,当温度达到500 ℃时,1 800 ℃和1 900 ℃烧结的陶瓷硬度分别下降到21.9 GPa和22.2 GPa,具有突出的高温稳定性。此外,HECs在温度低于500 ℃时无明显氧化,当温度超过650 ℃时会发生明显氧化,氧化速率随温度升高而增加。     

In Silico Discovery of Potential VEGFR-2 Inhibitors from Natural Derivatives for Anti-Angiogenesis Therapy

Angiogenesis is the growth of new capillaries from existing blood vessels that supply oxygen and nutrients and provide gateways for immune surveillance. Abnormal vessel growth in term of excessive angiogenesis is a hallmark of cancer, inflammatory and eye diseases. VEGFR-2 (vascular endothelial growth factor receptor 2) dominating the process of angiogenesis has led to approval of therapeutic inhibitors and is becoming a promising target for anti-angiogenic drugs. Notwithstanding these successes, the clinical use of current VEGFR-2 blockers is more challenging than anticipated. Taking axitinib as a reference drug, in our study we found three potent VEGFR-2 inhibitors (ZINC08254217, ZINC08254138, and ZINC03838680) from natural derivatives. Each of the three inhibitors acquired a better grid score than axitinib (−62.11) when docked to VEGFR-2. Molecular dynamics simulations demonstrated that ZINC08254217– and ZINC08254138–VEGFR-2 complexes were more stable than axitinib. Similar to bind free energy for axitinib (−54.68 kcal/mol), such for ZINC03838680, ZINC08254217, and ZINC08254138 was −49.37, −43.32, and −32.73 kcal/mol respectively. These results suggested these three compounds could be candidate drugs against angiogenesis, with comparable VEGFR-2 binding affinity of axitinib. Hence findings in our study are able to provide valuable information on discovery of effective anti-angiogenesis therapy.     

Effect of functional group polarity on the encapsulation of C60 derivatives in the inner space of carbon nanohorns

Encapsulation of C₆₀, its hydroxides (C₆₀(OH)_n, n = 10, 36, 44), and its hydride (C₆₀H₃₆) into inner space of carbon nanohorns (CNHs) from solutions or dispersions in various solvents by the nano-condensation method was attempted. The effect of the functional groups on the encapsulation was evaluated by transmission electron microscopy. C₆₀, C₆₀(OH)₁₀, and C₆₀H₃₆ can be efficiently encapsulated inside CNHs using toluene, THF, and DMSO as solvents, whereas C₆₀(OH)₃₆ and C₆₀(OH)₄₄ are hardly encapsulated from any solution. Because the molecular size of C₆₀(OH)₁₀ is similar to that of C₆₀(OH)₃₆ and C₆₀(OH)₄₄, the difference in encapsulation is not caused by molecular size. The efficient encapsulation of C₆₀H₃₆ in CNHs suggests that molecules can be encapsulated in carbon nanomaterials even when the π–π interaction with the sp²-hybridized carbon walls is weak. These results suggest the polarity of the functional group of the C₆₀ derivatives as the main factor in determining whether they can be encapsulated in CNHs. C₆₀(OH)₃₆ and C₆₀(OH)₄₄ contain many hydroxyl groups, thus these molecules self-aggregate and do not pass the holes of CNHs, resulting in poor encapsulation.     

Conductive nonwetting flexible substrate

In this paper an easy method to prepare flexible conductive substrates has been demonstrated. The substrates are mainly PET (PolyEthyleneTerephthalate), on which AgNW (silver nanowire) were deposited by spin casting method. For adhesion purpose a common cosmetic material has been utilized. The material provides versatile features to these coated substrates, including robustness, hydrophobicity with transparent bracing of nanowires (NW) with the flexible substrate. Four probe conductivity measurement shows the resistivity is 12 Ω/cm and is comparable to that of commercially available indium tin oxide (ITO) coated substrates. This method is cheap, easy and can be used for different objectives like flexible thin film photovoltaic, light emitting diodes, photosensors etc.     

Spatially resolved extrinsic photoresponse under additional intrinsic bias photoexcitation of two terminal pentacene devices

Spatially resolved extrinsic photoresponse experiments in pentacene two terminal devices without or under additional intrinsic bias-light excitation are employed. These experiments are used to investigate the microscopic mechanism of the recently observed phenomenon of the photoresponse enhancement under additional bias-light intrinsic excitation and to preclude that this phenomenon arises from contact-related artifacts. It is found that the extrinsic photogeneration near the contacts via electric field-assisted exciton splitting and/or light-induced depletion width-reduction have a negligible contribution to the extrinsic photoresponse. Under additional bias-light intrinsic excitation, a uniform increase of the photogenerated hole density is found to take place across the whole conduction channel, without changes in the electric field distribution and in the interfacial properties of the contacts. The photoresponse enhancement by the blue bias-light becomes stronger upon increasing the red-light intensity. A nearly square root dependence of the photoresponse enhancement on the blue bias-light intensity is found. It is shown that the observed dependence of the photoresponse enhancement on the light intensities of the extrinsic and intrinsic excitation can be explained with the extrinsic photogeneration mechanism based on hole detrapping by triplet exciton dissociation.     

An innovative process for synthesis of superfine nanostructured Li2TiO3 tritium breeder ceramic pebbles via TBOT hydrolysis – solvothermal method

In this paper, a method combining hydrolysis of tetrabutyl orthotitanate (TBOT) and solvothermal reaction was first used to fabricate nanostructured Li₂TiO₃ tritium breeder ceramic pebbles. Initially, superfine nanostructured Li₂TiO₃ powders were synthesized with average particle size of about 10?nm, according to TEM. The surface area of precursor particles synthesized via this method was found to be 115.85?m²/g by BET analysis, which is much larger than that of the product obtained using traditional methods. The results showed that precursor particles had high sintering activity. XRD pattern revealed that the phase transition temperature for monoclinic phase Li₂TiO₃ prepared by this method was nearly 450?°C, which was the lowest phase transition temperature reported among all wet chemical methods to date. Subsequently, investigation of ceramic sintering demonstrated that Li₂TiO₃ ceramic pebbles with desired nano-crystalline sizes (27.98 ~ 55.03?nm) were obtained by sintering at 500 ~ 600?°C for 4?h. The possible mechanisms were proposed based on the reaction processes of TBOT hydrolysis, solvothermal reaction and sintering.     

The prevalence of asthma and severe asthma in children influenced by transportation factors: Evidence from spatial analysis in Seoul,Korea

Although the causes of asthma are inconclusive, it is fairly known that exposure to outdoor air pollutants can cause asthma, especially children's asthma morbidity. Whereas transportation is one of the major sectors that generate air pollutants, previous research that investigates the correlation between transportation and asthma narrowly focuses on the contribution of automobile traffic to children's asthma. Developing three spatial regression models (a spatial lag (SL) model, a spatial error (SE) model, and a general spatial (SAC) model), this paper investigates the roles of a variety of transportation factors in two distinct stages of children's asthma morbidity; asthma and severe asthma. With consideration to asthma-related socio-economic factors in the City of Seoul, the SE (R² = 0.31) and SAC (R² = 0.34) models consistently indicate that three out of four transportation factors associate with children's severe asthma at statistically significant level. They include the negative influence of bus transit and dense intersections, and the positive influence of active transportation activities on children's asthma severity. Interestingly, however, no significant contribution of transportation factors to children's asthma morbidity was identified by the SE (R² = 0.29) and SAC (R² = 0.28) models. Shedding more light on the complexity of children's asthma morbidity and severity, this paper proposes collaborative partnerships not only among multi- dimensional agencies, but also among multi-level government organizations.     

微生物质水热碳锰复合材料对铀的吸附行为研究

以工业啤酒酵母为碳源，采用一步法合成了微生物质水热碳锰复合材料（MHTC），并利用XRD、FT-IR和SEM等对材料进行了表征。在此基础上，系统研究了不同C/Mn原子比、初始pH值、接触时间、初始铀浓度对MHTC吸附铀性能的影响。结果表明：C/Mn原子比为1∶10的碳锰复合材料（MHTC-10）对铀的吸附性能最优。在铀初始浓度为50 mg/L、初始pH=4.5条件下，12 h可达吸附平衡，最大吸附量为371 mg/g。吸附过程符合准二级动力学模型以及Freundlich等温模型。热力学数据表明，铀在MHTC-10上的吸附是一自发、放热的过程。该研究结果可为含铀环境中铀的分离富集提供新的思路。     

Relative phase shift in laguerre-gaussian beams propagating through an apertured paraxial ABCD system

Abstract

Based on the generalized Huygens-Fresnel diffraction integral, closed-form expressions for the relative phase shift of Laguerre-Gaussian beams propagating through an apertured paraxial optical ABCD system are derived. The dependence of the relative phase shift on the beam and system parameters, and the condition for eliminating phase shift are analysed and illustrated with numerical examples.     

Prediction of Mechanical Properties of Hot Rolled Strip by Using Semi-Parametric Single-Index Model

 A semi-parametric single-index model based approach was proposed for prediction of mechanical properties of hot rolled strip. Based on industrial production data, a semi-parametric single-index model was developed by choosing the appropriate kernel function and window width to predict the yield strength, tensile strength and elongation. When data samples are limited, compared with regression method and neural network method, the prediction results show that the semi-parametric single-index model based method is more adaptive and the prediction performance is superior to those by both regression and neural network methods.