Ablation and ultrafast dynamics of zinc selenide under femtosecond laser irradiation

The ablation in zinc selenide (ZnSe) crystal is studied by using 150-fs, 800-nm laser system. The images of the ablation pit measured by scanning electronic microscope (SEM) show no thermal stress and melting dynamics. The threshold fluence is measured to be 0.7 J/cm2. The ultrafast ablation dynamics is studied by using pump and probe method. The result suggests that optical breakdown and ultrafast melting take place in ZnSe irradiated under femtosecond laser pulses.     

Two new benzolactones from the leaves of Nicotiana tabacum and their anti-tobacco mosaic virus activities

Two new benzolactones, 5-methyl-6-prenyl-isobenzofuran-1(3H)-one (1), 5-hydroxymethyl-6-prenyl-isobenzofuran-1(3H)-one (2), together with four known phenolic compounds (3–6), were isolated from the leaves of Nicotiana tabacum. Their structures were elucidated by spectroscopic methods, including extensive 1D and 2D NMR techniques. Compounds 1–6 were evaluated for their anti-tobacco mosaic virus (anti-TMV) activities. The results showed that compounds 1–6 exhibited high anti-TMV activities with inhibition rates in the range of 16.9–26.2%, respectively.     

Triplet Acceptors with a D-A Structure and Twisted Conformation for Efficient Organic Solar Cells

Triplet acceptors have been developed to construct high-performance organic solar cells (OSCs) as the long lifetime and diffusion range of triplet excitons may dissociate into free charges instead of net recombination when the energy levels of the lowest triplet state (T₁) are close to those of charge-transfer states (³CT). The current triplet acceptors were designed by introducing heavy atoms to enhance the intersystem crossing, limiting their applications. Herein, two twisted acceptors without heavy atoms, analogues of Y6, constructed with large π-conjugated core and D-A structure, were confirmed to be triplet materials, leading to high-performance OSCs. The mechanism of triplet excitons were investigated to show that the twisted and D-A structures result in large spin–orbit coupling (SOC) and small energy gap between the singlet and triplet states, and thus efficient intersystem crossing. Moreover, the energy level of T₁ is close to ³CT, facilitating the split of triplet exciton to free charges.     

Traffic of leukocytes in microfluidic channels with rectangular and rounded cross-sections

Traffic of leukocytes in microvascular networks (particularly through arteriolar bifurcations and venular convergences) affects the dynamics of capillary blood flow, initiation of leukocyte adhesion during inflammation, and localization and development of atherosclerotic plaques in vivo. Recently, a growing research effort has been focused on fabricating microvascular networks comprising artificial vessels with more realistic, rounded cross-sections. This paper investigated the impact of the cross-sectional geometry of microchannels on the traffic of leukocytes flowing with human whole blood through a non-symmetrical bifurcation that consisted of a 50 μm mother channel bifurcating into 30 μm and 50 μm daughter branches. Two versions of the same bifurcation comprising microchannels with rectangular and rounded cross-sections were fabricated using conventional multi-layer photolithography to produce rectangular microchannles that were then rounded in situ using a recently developed method of liquid PDMS/air bubble injection. For microchannels with rounded cross-sections, about two-thirds of marginated leukocytes traveling along a path in the top plane of the bifurcation entered the smallest 30 μm daughter branch. This distribution was reversed in microchannels with rectangular cross-sections--the majority of leukocytes traveling along a similar path continued to follow the 50 μm microchannels after the bifurcation. This dramatic difference in the distribution of leukocyte traffic among the branches of the bifurcation can be explained by preferential margination of leukocytes towards the corners of the 50 μm mother microchannels with rectangular cross-sections, and by the additional hindrance to leukocyte entry created by the sharp transition from the 50 μm mother microchannel to the 30 μm daughter branch at the intersection. The results of this study suggest that the trajectories of marginated leukocytes passing through non-symmetrical bifurcations are significantly affected by the cross-sectional geometry of microchannels and emphasize the importance of using microfludic systems with geometrical configurations closely matching physiological configurations when modeling the dynamics of whole blood flow in the microcirculation.     

Synthesis and reactivity of alkynyl-linked phosphonium borates

The phosphine tBu₂PC?CH ( 1 ) was reacted with B(C₆F₅) to give the zwitterionic species tBu₂P(H)C?CB(C₆F₅)₃ ( 2 ). The analogous species tBu₂P(Me)C?CB(C₆F₅)₃ ( 3 ), tBu₂P(H)C?CB(Cl)(C₆F₅)₂ ( 4 ), tBu₂P(H)C?CB(H)(C₆F₅)₂ ( 5 ), and tBu₂P(Me)C?CB(H)(C₆F₅) ₂ ( 6 ) were also prepared. The salt [tBu₂P(H)C?CB(C₆F₅)₂(THF)][B(C₆F₅)₄] ( 7 ) was prepared through abstraction of hydride by [Ph₃C][B(C₆F₅)₄]. Species 5 reacted with the imine tBuN?CHPh to give the borane–amine adduct tBu₂PC?CB[tBuN(H)CH₂Ph](C₆F₅)₂ ( 8 ). The related phosphine Mes₂PC?CH ( 9 ; Mes=C₆H₂Me₃) was used to prepare [tBu₃PH][Mes₂PC?CB(C₆F₅)₃] ( 10 ) and generate Mes₂PC?CB(C₆F₅)₂. The adduct Mes₂PC?CB(NCMe)(C₆F₅)₂ ( 11 ) was isolated. Reaction of Mes₂PC?CB(C₆F₅)₂ with H₂ gave the zwitterionic product (C₆F₅)₂(H)BC(H)?C[P(H)Mes₂][(C₆F₅)₂BC?CP(H)Mes₂] ( 12 ). Reaction of tBu₂PC?CB(C₆F₅)₂, a phosphine–borane generated in situ from 5 , with 1‐hexene gave the species [tBu₂PC?CB(C₆F₅)₂](CH₂CHnBu)[tBu₂PC?CB(C₆F₅)₂] ( 13 ) and subsequent reaction with methanol or hexene resulted in the formation of [tBu₂P(H)C?CB(C₆F₅)₂](CH₂CHnBu)[tBu₂PC?CB(C₆F₅)₂](OMe) ( 14 ) or the macrocycle {[tBu₂PC?CB(C₆F₅)₂](CH₂CH₂nBu)}₂ ( 15 ), respectively. In a related fashion, the reaction of 13 with THF afforded the macrocycle [tBu₂PC?CB(C₆F₅)₂](CH₂CHnBu)[tBu₂PC?CB(C₆F₅)₂][O(CH₂)₄] ( 16 ), although treatment of tBu₂PC?CB(C₆F₅)₂ with THF lead to the formation of {[tBu₂PC?CB(C₆F₅)₂][O(CH₂)₄]}₂ ( 17 ). In a related example, the reaction of Mes₂PC?CB(C₆F₅)₂ with PhC?CH gave {[Mes₂PC?CB(C₆F₅)₂](CH?CPh)}₂ ( 18 ). Compound 5 reacted with AlX₃ (X=Cl, Br) to give addition to the alkynyl unit, affording (C₆F₅)₂BC(H)?C[P(H)tBu₂](AlX₃) (X=Cl 19 , Br 20 ). In a similar fashion, 5 reacted with [Zn(C₆F₅)₂] ? C₇H₈, [Al(C₆F₅)₃] ? C₇H₈, or HB(C₆F₅)₂ to give (C₆F₅)₃BC(H)?C[P(H)tBu₂][Zn(C₆F₅)] ( 21 ), (C₆F₅)₃BC(H)?C[P(H)tBu₂][Al(C₆F₅)₂] ( 22 ), or [(C₆F₅)₂B]₂HC?CH[P(H)tBu₂] ( 23 ), respectively. The implications of this reactivity are discussed.     

Preparation,characterization of cationic terbium luminescent copolymer and its interaction with DNA

A complex of Tb³⁺, acrylic acid (AA), and 1, 10-phenanthroline (Phen) was synthesized. The structure and fluorescence of Tb(AA)₃Phen·H₂O was characterized with elemental analysis, FT-IR, and fluorescence spectroscopy. A novel copolymer containing rare earth complex, poly (METAC-co-NIPAm-co-Tb(AA)₃Phen·H₂O) (PMNTb), was prepared by free radical copolymerization in methanol with azodiisobutyronitrile (AIBN) as initiator. ¹H NMR, fluorescence spectroscopy, UV-vis spectroscopy, and TEM were used to characterize this copolymer. The interaction of PMNTb with DNA was studied by fluorescence spectroscopy, UV-vis spectroscopy, and agarose gel electrophoresis. The results of fluorescence, UV-vis absorption, and agarose electrophoresis indicated that the PMNTb could interact with DNA in an electrostatic bonding mode and the bonding constant was 3.4 × 10⁵ L mol⁻¹. The TEM observation showed that the PMNTb could form micelles in water solution; the efficient complexation of PMNTb with DNA occurred. The results of in vitro cytotoxicity indicated that PMNTb had good biocompability. These results laid the foundation for the further study in potential gene detective reagent and gene delivery carrier.     

Isolation of fucoxanthin from edible brown algae by microwave-assisted extraction coupled with high-speed countercurrent chromatography

A rapid and efficient method for the separation and purification of fucoxanthin from edible brown algae by microwave-assisted extraction coupled with high-speed countercurrent chromatography was developed. The algae were first extracted using microwave-assisted extraction, then the dried extract was dissolved and directly introduced into the high-speed countercurrent chromatography system with a two-phase solvent system consisting of hexane-ethyl acetate-ethanol-water (5:5:6:4, v/v/v/v). The isolation was done in less than 75 min, and a total of 0.83 mg, 1.09 mg, and 0.20 mg fucoxanthin were obtained from 25.0 g fresh Laminaria japonica Aresch, 1.5 g dry Undaria pinnatifida (Harv) Sur, and 15.0 g dry Sargassum fusiforme (Harv) Setch, respectively. The purity of fucoxanthin determined by HPLC was over 90% and its structure was further identified by LC-ESI-MS and (1) H-NMR.     

超短脉冲照射下氟化锂的烧蚀机理及其超快动力学研究

研究了超短脉冲激光照射下LiF晶体的破坏机理及其超快动力学过程,利用扫描电镜和原子力显微镜等测试手段,观测了飞秒激光照射下LiF晶体的烧蚀形貌。利用烧蚀面积与激光脉冲能量的对数关系确定了LiF晶体的破坏阈值,并利用非线性玻璃棒展宽脉宽,得到了800nm激光作用下LiF破坏阈值对激光脉宽（50～1000fs）的依赖关系;利用抽运一探针超快探测平台,探测了LiF烧蚀过程中反射率的变化。采用雪崩击穿模型,并根据晶体材料反射率与材料的介电常量的依赖关系,通过数值计算,模拟了材料烧蚀阈值与脉宽的依赖关系及材料激发过程中反射率的变化关系。结果表明,理论结果与实验结果符合较好。讨论了飞秒激光照射下LiF晶体中导带电子数密度的变化规律,并解释了相应的实验结果。     

Screening of Oleaginous Yeast Strains Tolerant to Lignocellulose Degradation Compounds

High cost of triacylglycerol lipid feedstock is the major barrier for commercial production of biodiesel. The fermentation of oleaginous yeasts for lipid production using lignocellulose biomass provides a practical option with high economic competitiveness. In this paper, the typical oleaginous yeast strains were screened under the pressure of lignocellulose degradation compounds for selection of the optimal strains tolerant to lignocellulose. The inhibitory effect of lignocellulose degradation products on the oleaginous yeast fermentation was carefully investigated. Preliminary screening was carried out in the minimum nutritious medium without adding any expensive complex ingredients then was carried out in the lignocellulosic hydrolysate pretreated by dilute sulfuric acid. Seven typical lignocellulose degradation products formed in various pretreatment and hydrolysis processing were selected as the model inhibitors, including three organic acids, two furan compounds, and two phenol derivatives. The inhibition of the degradation compounds on the cell growth and lipid productivity of the selected oleaginous yeasts were examined. Acetic acid, formic acid, furfural, and vanillin were found to be the strong inhibitors for the fermentation of oleaginous yeasts, while levulinic acid, 5-hydroxymethylfurfural, and hydroxybenzaldehyde were relatively weak inhibitors. Trichosporon cutaneum 2.1374 was found to be the most adopted strain to the lignocellulose degradation compounds.     

Inhibition Performance of Lignocellulose Degradation Products on Industrial Cellulase Enzymes During Cellulose Hydrolysis

This study examined the inhibition performance by the major lignocellulose degradation products, including organic acids, furan derivatives, lignin derivatives, and ethanol, on a broadly used commercial cellulase enzyme Spezyme CP (Genencor International, Rochester, NY, USA) to cellulose hydrolysis at both the well-mixing state (shaking flask) and the static state (test tube). The cellulase activity in the cellulase complex of Spezyme CP was assumed to be one single “cellulase”, and the apparent kinetic parameters of this cellulase enzyme were measured as an approximate index of the inhibitory effect to the industrial cellulase enzyme. The inhibition performance of these degradation products was compared and analyzed using the determined apparent kinetic parameters. All the degradation products strongly inhibit the cellulose hydrolysis by cellulase enzyme, and the inhibitions on cellulase were all competitive type. The order of the inhibition strength by the lignocellulose degradation products to cellulase is lignin derivatives > furan derivatives > organic acids > ethanol. This study gave a quantitative view to the enzymatic hydrolysis of lignocellulose under the inhibition performance of the lignocellulose degradation products and will help to understand the lignocellulose recalcitrance to enzyme hydrolysis.