Design,Synthesis, and Biological Evaluation of Shikonin and Alkannin Derivatives as Potential Anticancer Agents via a Prodrug Approach

To minimize the cytotoxicity of shikonin and alkannin that arises through the generation of reactive oxygen species (ROS) and alkylation of the naphthazarin ring, two series of novel core‐scaffold‐modified shikonin and alkannin derivatives were designed. These derivatives, which differ in their configurational and positional isomerism (R‐, S‐, and 2‐ and 6‐isomers) were synthesized in high enantiomeric excess (>99 % ee). The selectivity of the dimethylated derivatives was significantly higher than the parent shikonin in vitro, but some side effects were still observed in vivo. Surprisingly, the dimethylated diacetyl derivatives with poor anticancer activity in vitro showed tumor‐inhibiting effects similar to paclitaxel without any toxicity in vivo. The anticancer activity of these derivatives is in agreement with their low ROS generation and alkylating capacity, emphasizing their potential as prodrugs. This strategy provides means to address the nonspecific cytotoxicity of naphthazarin analogues toward normal cells.     

Baicalin Ameliorates H2O2 Induced Cytotoxicity in HK-2 Cells through the Inhibition of ER Stress and the Activation of Nrf2 Signaling

Renal ischemia-reperfusion injury plays a key role in renal transplantation and greatly affects the outcome of allograft. Our previous study proved that Baicalin, a flavonoid glycoside isolated from Scutellaria baicalensis, protects kidney from ischemia-reperfusion injury. This study aimed to study the underlying mechanism in vitro. Human renal proximal tubular epithelial cell line HK-2 cells were stimulated by H₂O₂ with and without Baicalin pretreatment. The cell viability, apoptosis and oxidative stress level were measured. The expression of endoplasmic reticulum (ER) stress hallmarks, such as binding immunoglobulin protein (BiP) and C/EBP homologous protein (CHOP), were analyzed by western blot and real-time PCR. NF-E2-related factor 2 (Nrf2) expression was also measured. In the H₂O₂ group, cell viability decreased and cell apoptosis increased. Reactive Oxygen Species (ROS) and Glutathione/Oxidized Glutathione (GSH/GSSG) analysis revealed increased oxidative stress. ER stress and Nrf2 signaling also increased. Baicalin pretreatment ameliorated H₂O₂-induced cytotoxicity, reduced oxidative stress and ER stress and further activated the anti-oxidative Nrf2 signaling pathway. The inducer of ER stress and the inhibitor of Nrf2 abrogated the protective effects, while the inhibitor of ER stress and the inducer of Nrf2 did not improve the outcome. This study revealed that Baicalin pretreatment serves a protective role against H₂O₂-induced cytotoxicity in HK-2 cells, where the inhibition of ER stress and the activation of downstream Nrf2 signaling are involved.     

Numerical simulations of the current-matching effect and operation mechanisms on the performance of InGaN/Si tandem cells

Numerical simulations are conducted to study the current-matching effect and operation mechanisms in and to design the optimized device structure of InGaN/Si tandem cells. The characteristics of short circuit current density (J_sc), open circuit voltage (V_oc), fill factor (FF), and conversion efficiency (η) of InGaN/Si tandem cells are determined by the current-matching effect. The similar trend of η to that of J_sc shows that J_sc is a dominant factor in determining the performance of InGaN/Si tandem cells. In addition, the combined effects of the J_sc, V_oc, and FF lead to an optimized η in the medium-indium, xpn-InGaNInGaN‒to‒Si, InGaN/Si tandem cell. At xpn-InGaNInGaN‒to‒Si, the J_sc of the InGaN subcell is equal to that of the Si subcell such that an InGaN/Si tandem cell reaches the current matching condition to operate at the maximum power point. Similar to the J_sc and FF, the η for low- xpn-InGaN<xpn‒InGaNInGaN‒to‒Si and high-In xpn-InGaN>xpn-InGaNInGaN‒to‒Si InGaN/Si tandem cells are InGaN- and Si subcell-limited, respectively. Furthermore, the p- and n-layer thicknesses, indium content, and position of depletion region of InGaN subcell should be adjusted to reapportion the light between the two subcells and to achieve the maximum conversion efficiency. With appropriate thicknesses of p- and n-InGaN, In_0.5–0.6Ga_0.5–0.4 N/Si tandem cells can exhibit as high as approximately 34% to 36.5% conversion efficiency, demonstrating that a medium-indium InGaN/Si tandem cell results in a high-efficiency solar cell. Simulation results determine that the current-matching effect and operation mechanisms of InGaN/Si tandem cells can be utilized for efficiency enhancement through the optimized device structures.     

Porous Si3N4/SiC Ceramics Prepared via Nitridation of Si Powder with SiC Addition

Porous Si₃N₄/SiC ceramics with high porosity were prepared via nitridation of Si powder, using SiC as the second phase and Y₂O₃ as sintering additive. With increasing SiC addition, porous Si₃N₄/SiC ceramics showed high porosity, low flexural strength, and decreased grain size. However, the sample with 20wt% SiC addition showed highest flexural strength and lowest porosity. Porous Si₃N₄/SiC ceramics with a porosity of 36–45% and a flexural strength of 107‐46MPa were obtained. The linear shrinkage of all porous Si₃N₄/SiC ceramics is below 0.42%. This study reveals that the nitridation route is a promising way to prepare porous Si₃N₄/SiC ceramics with favorable flexural strength, high porosity, and low linear shrinkage.     

Enhanced Piezoelectric and Dielectric Responses in 92.5%(Bi0.5Na0.5) TiO3 ‐7.5%BaTiO3 Ceramics

Structure and piezoelectric coefficient (d₃₃) of lead‐free 7.5% mole BaTiO₃‐doped (Bi_0.5Na_0.5) TiO₃ (BNT‐7.5%BT) polycrystalline piezoceramics have been characterized systematically as a function of poling electric (E) field. Dielectric permittivity and loss were also measured as functions of frequency and temperature. The piezoelectric coefficient d₃₃ after poling at E = 35 kV/cm can reach d₃₃~186 pC/N, which is the highest value reported among (1?x) BNT–xBT compositions. A prior poling E field can reduce rhomobherdal lattice distortion, and enhance tetragonal phase and polarization ordering, that contribute significantly to the rapid raise of d₃₃ and lower depolarizing temperature (T_d). The reduced dielectric permittivity for the poled sample is attributed to ordered state and the pinning of field‐induced nanodomain walls by the presence of oxygen vacancies.     

国内外油基钻井液研究现状

油基钻井液具有抗侵蚀、抗高温、润滑性好、有利于井壁稳定以及对储层污染程度小等特点,主要用于地层情况复杂的深井、超深井和水平井等。主要介绍了国内外油基钻井液的研究现状,油基钻井液按基油类型可分为四类:白油基钻井液、柴油基钻井液、气制油基钻井液、低毒钻井液。对各类油基钻井液进行了评价与比较,并对油基钻井液今后的发展提出了建议。     

Recycling carbon fiber composites using microwave irradiation: Reinforcement study of the recycled fiber in new composites

With increasing use of carbon fiber reinforced polymer (CFRP) composites in transportation, sports, and many other industries, recycling of the scrap and end‐of‐life composites has presented both great challenges and opportunities. In this work, we report our study on reclaiming carbon fibers from CFRP using energy efficient microwave irradiation. Different irradiation conditions were used and the optimal conditions were determined based on the surface morphology of the recycled fiber. Polypropylene (PP) and Nylon, representing nonpolar and polar polymers, respectively, were reinforced using the recycled fiber through extrusion and injection molding. For comparison, PP and Nylon reinforced by virgin carbon fiber were also prepared using the same processing conditions. Tensile, flexural, and impact test results showed that, while both carbon fibers could improve these properties, they exhibited different reinforcing effects on the two polymers. The recycled fiber outperformed the virgin fiber in reinforcing PP whereas the virgin fiber performed better in Nylon. This was due to the differences in surface roughness, surface bonding, and fiber aspect ratio between the two fibers. This study shows the great potential of recycled carbon fiber and microwave irradiation as an effective recycling technique. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42658.     

Ferroelectricity and Ferromagnetism of M‐Type Lead Hexaferrite

Polarization and related properties in the M‐type lead hexaferrite (PbFe₁₂O₁₉) are reported for the first time. The remnant polarization of PbFe₁₂O₁₉ exhibits a maximum value of 104 μC/cm², as well as large spontaneous polarization at room temperature. Annealing of PbFe₁₂O₁₉ in oxygen plays a key role in the saturation of its polarization hysteresis loop because it greatly enhances the ceramic's electric resistance. Two current peaks in the I–V curve reveal a polarization switch, providing effective evidence for the ferroelectricity of PbFe₁₂O₁₉. Its temperature‐dependent dielectric constant undergoes colossal change in the vicinity of two temperatures (322°C and 518°C), which are assigned to the transitions from ferro‐ to antiferro‐ and antiferro‐ to paraelectric phases, respectively. The plots of logarithm of (1/ε–1/ε_m) as a function of logarithm of (T–T_m) obey a modified Curie–Weiss law, verifying the relaxor ferroelectric characterization of PbFe₁₂O₁₉. The ceramic also exhibits a strong magnetic hysteresis loop. These combined functional responses of ferroelectricity and ferromagnetism in PbFe₁₂O₁₉ ceramic present an opportunity to create electric devices that actively couple the magnetic and ferroelectric orders.