Three unprecedented biphenyl derivatives bearing C6-C3 carbon skeleton from the bark of Magnolia officinalis var. biloba

(±)-Magoilgomer A [(±)-1] and magoilgomer B (2) were identified from the bark of Magnolia officinalis var. biloba. (+)-1 and (−)-1 were a pair of novel biphenyl derivatives featuring three C6-C3 subunits. 2 was an unprecedented adduct containing magnolol and honokiol. These three oligomers possessed new parallel mode which should be biosynthesized from the coupling of three or four C6-C3 subunits. The structures of (±)-1 and 2 were elucidated based on the spectroscopic data analyses and electronic circular dichroism (ECD) calculations. 2 exhibited neuroprotective effects of oxygen glucose deprivation-induced SK-N-SH cell injury.     

Magnetic field as a means to identify initiating reaction in oxidation of organic substances with molecular oxygen

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Noble metal nanoparticles meet molecular cages: A tale of integration and synergy

Noble metal nanoparticles attract growing interest owing to their high surface-to-volume ratio and unique optical, electric and catalytic properties. Fine-tuning these properties and broadening potential applications can be envisaged if nanoparticles are coupled to supramolecular cages that afford a highly tailorable inner environment as well as rich endo-/exo-functionalization. Due to rich chemical/physical properties of cages, integration of multiple host-guest interactions in confined cavities through endo-molecular design has been achieved. Such cages provide ideal confined templates for size-controlled synthesis of ultrafine nanoparticles with superior catalytic activities. Moreover, exo-functionalization of cages offers huge opportunities to couple with nanoparticles, generating cage-nanoparticle hybrids or hierarchical assemblies that combine merits of both. The present review provides recent advances in cage-mediated nanoparticle systems with synergistic effects and integrated functions, and demonstrates their applications in catalysis, sensing, chiral amplification, plasmonic switches, imaging and cell therapy. Finally, we highlight key challenges and identify emerging directions in the coming years.     

Excluded‐Volume Effects in Living Cells

Biomolecules evolve and function in densely crowded and highly heterogeneous cellular environments. Such conditions are often mimicked in the test tube by the addition of artificial macromolecular crowding agents. Still, it is unclear if such cosolutes indeed reflect the physicochemical properties of the cellular environment as the in‐cell crowding effect has not yet been quantified. We have developed a macromolecular crowding sensor based on a FRET‐labeled polymer to probe the macromolecular crowding effect inside single living cells. Surprisingly, we find that excluded‐volume effects, although observed in the presence of artificial crowding agents, do not lead to a compression of the sensor in the cell. The average conformation of the sensor is similar to that in aqueous buffer solution and cell lysate. However, the in‐cell crowding effect is distributed heterogeneously and changes significantly upon cell stress. We present a tool to systematically study the in‐cell crowding effect as a modulator of biomolecular reactions.     

Scaling effect on the tensile properties of [±45/0/±45/0/±45] Polypropylene/Twaron laminates

The effects of scaling on the mechanical response under tension of balanced nonsymmetrical laminates were investigated for a thermoplastic composite: Polypropylene reinforced with Twaron^® fibers. The composite baseline was an 8-ply laminate which consisted of unidirectional plies arranged in the sequence [±45/0/±45/0/±45]. The influence of specimen size on the tensile properties was studied for one (thickness), two (in-plane) and three (volume) dimensional scaling. The stress-strain curves suggested some variation in laminate behavior owing to the dimensional scaling; nevertheless, a further analysis with the classical lamination theory demonstrated that the observed effect was due to small variations in the fiber volume fraction of the laminates. It was concluded that the mechanical properties of these thermoplastic laminates do not exhibit scaling effects. The failure mechanism of the laminates was studied at macroscopic level; a scale effect of the fracture mechanism was observed.     

The role of induced current density in Steroelectronic effects: Perlin effect

The normal and reverse Perlin effect is usually explained by the redistribution of electron density produced by hyperconjugative mechanisms, which increases the electron population within axial or equatorial proton in normal or reverse effect, respectively. Here an alternative explanation for the Perlin effect is presented on the basis of the topology of the induced current density, which directly determines the nuclear magnetic shielding. Current densities around the C? H bond critical point and intra‐atomic and interatomic contributions to the magnetic shielding explain the observed Perlin effect. The balance between intra‐atomic and interatomic contributions determines the difference in the total atomic shielding. Normal Perlin effect is dominated by intra‐atomic part, whereas reverse effect is dominated by interatomic contribution. © 2015 Wiley Periodicals, Inc.     

Triplet excitation dynamics of β-carotene studied in three solvents by ns flash photolysis spectroscopy

Upon anthracene-sensitizing, triplet excitation dynamics of β-carotene(β-Car) were studied in nhexane, in methanol, and in acetonitrile, respectively, by ns flash photolysis spectroscopy. In n-hexane,only the bleaching of the ground state absorption(GSB) and the excitation triplet(~3Car*) absorption were observed, and there were no cationic species detected. In both methanol and acetonitrile, similar excitation dynamics were observed, i.e.,~3Car* having a similar lifetime to that in n-hexane, and the immediate generation of the cation dehydrodimer(~#[Car]2~+) upon excitation following transformation into the radical cation Car*~+, since Car*~+ has much longer lifetime in acetonitrile than in methanol. The results prove that both solvent and carotenoid structure determine the triplet excitation mechanism.     

具有高灵敏性且稳定可重复的正温度系数效应的PVDF/CF导电复合材料

以碳纤维(CF)为填料,聚偏氟乙烯(PVDF)为基体,通过熔融共混法制备PVDF/CF导电复合材料.所得复合材料具有显著的正温度系数(PTC)效应,温度上升到聚合物熔点附近时,电阻率对温度变化敏感.在转折温度区间(155.5~171.0oC,(35)(28)15.5oC)内,其体积电阻率的增加速率约为1.3×105?cm K-1.在不同CF含量下,复合材料表现出不同的PTC行为.随着CF含量的增加,其峰值电阻略有下降.高导电粒子含量下,无负温度系数(NTC)效应.在冷却循环过程,导电网络的重构性良好.复合材料即使经过多次热循环,依然表现出良好的PTC特性重现性.