李斯特钢琴作品中的技术成分及其艺术价值分析——以《十二卷钢琴技巧练习》为例

在李斯特的钢琴作品中,对钢琴技术的贡献具有里程碑式的意义。文章以《十二卷钢琴技巧练习》为例对李斯特钢琴作品中的各类技术成分进行分析,李斯特钢琴作品中的技术概括为四个种类:钢琴基本技术、拓展型基本技术、复合技术和综合配置的复合技术。而所谓的综合配置的复合技术即是炫技性钢琴技术,并归总结其艺术价值。

High rodent abundance increases seed removal but decreases scatter-hoarding and seedling recruitment along an elevational gradient

The distributions of small rodents in mountainous environments across different elevations can provide important information regarding the effects of climate change on the dispersal of plant species.However,few studies of oak forest ecosystems have compared the elevational patterns of sympatric rodent diversity,seed dispersal,seed bank,and seedling abundance.Thus,we tested the differences in the seed disperser composition and abundance,seed dispersal,seed bank abundance,and seedling recruitment for Quercus wutaishanica along 10 elevation levels in the Taihang Mountains,China.Our results provide strong evidence that complex asymmetric seed dispersal and seedling regeneration exist along an elevational gradient.The abundance of rodents had a significant negative correlation with the elevation and the seed removal rates peaked and then declined with increasing elevation.The seed removal rates were higher at middle and lower elevations than higher elevations but acorns were predated by 5 species of seed predators at middle and lower elevations,and thus,there was a lower likelihood of recruitment compared with those dropped beneath mother oaks at higher elevations.More importantly,the number of individual seeds in the seed bank and seedlings increased with the elevation,although dispersal services were reduced at sites lacking rodents.As conditional mutualists,the rodents could possibly act as antagonistic seed predators rather than mutualistic seed dispersers at low and middle elevations,thereby resulting in the asymmetric pattern of rodent and seedling abundance with increasing elevation to affect the community assembly and ecosystem functions on a large spatial scale.

Constructing hydrophobic protection for ionic interactions toward water,acid,and base-resistant self-healing elastomers and electronic devices

Dynamically crosslinked materials generally lose their self-healing ability and mechanical robustness in aqueous,acidic,and basic environments due to disruption of their dynamic interactions and bonds.Herein,a micelle-like structure with a hydrophobic outer layer is used to protect ionic interactions.This structure ensures the self-healing and long-term stability of the ionically crosslinked elastomers in aqueous,acidic,and basic environments.The elastomer possesses a tensile strength of 6.7 MPa and a strain at break of 1400%,which is superior to the existing waterproof selfhealing elastomers.The strain sensors and dielectric actuators based on the elastomer are highly stable and self-healable,even in extremely harsh environments.This design strategy of hydrophobic protection for dynamic interactions is quite general,allowing it to be extended to other self-healing materials.

A fast-healing and high-performance metallosupramolecular elastomer based on pyridine-Cu coordination

Elastomers easily undergo a catastrophic failure as soon as a crack is introduced by mechanical damage.Thus,it is extremely important for elastomers to possess fast healing ability,which enables the quick reparation of cracks.However,developing elastomers with fast self-healing ability and high mechanical strength is highly challenging.Herein,we fabricate a metallosupramolecular elastomer by facilely introducing pyridine-Cu coordination into a copolymer of ethyl acrylate and vinyl pyridine.Interestingly,the pyridine-Cu coordination has a strong photothermal effect,which readily increases the sample temperature to 60℃ in 30 s under near-infrared light.At this temperature,the sticky reptation modes are activated and thus serve as the driving force for network reorganization and fast self-healing of the metallosupramolecular elastomer.Albeit with a tensile strength of 10 MPa,the scratched and completely fractured samples can be healed within 2 min and 3 h,respectively.Moreover,during the damage and healing processes,the break and reformation of the coordination bonds can be tracked through laser confocal micro-Raman spectroscopy.This provides a microscopic methodology to monitor the bond-level healing kinetics of metallosupramolecular polymers.

A recyclable polyurethane with characteristic thermal stiffening behavior via B-N coordination with reversible B-O bonds

Thermal softening is an inevitable process in the physical network.Polyurethane(PU),a typical commercial material,is constructed by physical networks,which undergoes the serious thermal decay on mechanical properties at high temperature.Herein,a physically cross-linked PU with a unique thermal stiffening behavior has been developed by incorporating B–N coordination with reversible B–O bonds.The B–N coordination can significantly improve the mechanical properties of the PU.The reversible B–O bonds(temperature dependent reversible transformation between B–OH and B–O–B)are conducive to constructing more multicoordination macromolecular crosslinking points and more stable B–N coordination bonds at high temperature,endowing the PU with the special thermal stiffening behavior for the first time.Such thermal stiffening behavior compensates for the bond breakage and the network destruction caused by heat,significantly expands the rubbery plateau and delays the entire chain motion of the thermoplastic PU.As a result,the terminal flow occurs at a higher temperature up to 200°C.The modulus retention ratio of the materials is up to 87%even at 145oC,which is much higher than that of the existing PU elastomer with the physical network and even some covalent cross-link PU.Simultaneously,the physical network ensures the recyclability of the PU,and the thermal stiffening behavior is still obtained in recycled PU.This work provides a simple strategy to impart thermal stiffening behavior to the physically crosslinked PU,thereby significantly extending the operating temperature range of thermoplastic PU,which can potentially expand the scopes of PU in applications under harsh conditions.