Commentary on "Mechanical properties of monodomain side-chain nematic elastomers" by P. Martinoty, P. Stein, H. Finkelmann, H. Pleiner and H.R. Brand

We discuss the background to static and dynamic soft elasticity. The evidence in the static case and the symmetry basis for soft and semi-soft elasticity is well understood. By contrast the dynamic analogy is less clear. Lack of clean time scale separation clouds the interpretation of director relaxation keeping up, or not, with imposed strains. However, the reduction in modulus between geometries obtaining at low frequencies and being lost at high frequencies confirms that director reaction indeed determines dynamical semi-softness.     

Comment on "silent research vessels are not quiet" [J. Acoust. Soc. Am. 121, EL145-EL150

The recent paper by Ona et al. [J. Acoust. Soc. Am. 121, EL145-EL150] compared avoidance reactions by herring (Clupea harengus) to a traditional and a "silent" research vessel. Surprisingly, the latter evoked the strongest avoidance, leading to the conclusion that "candidate stimuli for vessel avoidance remain obscure." In this Comment, it is emphasized that the otolith organs in fish are linear acceleration detectors with extreme sensitivity to infrasonic particle acceleration. Near-field particle motions generated by a moving hull are mainly in the infrasonic range, and infrasound is particularly potent in evoking directional avoidance responses in several species of fish. The stimuli initiating vessel avoidance may thus include infrasonic particle acceleration.     

最具潜力的新型"奇迹材料"——石墨烯

2009年4月29日据物理世界网报道,意大利的科研人员成功地用石墨烯制造了首枚包含两个晶体管的集成电路(见封面主图),它拥有简单的计算能力,标制着碳基电子学时代的到来.这枚只有两个晶体管的集成电路虽然很小,却是向制造碳基高性能电子器件迈出的重要一步.     

Addendum to the paper "Dead-time free measurement of dipole-dipole interactions between electron spins" by M. Pannier, S. Veit, A. Godt, G. Jeschke, and H.W. Spiess [J. Magn. Reson. 142 (2000) 331-340

The development of four-pulse DEER as described, which has been published in the Journal of Magnetic Resonance more than 10 years ago. The corresponding paper is an example where a slight advance, such as adding a refocusing pulse, which in retrospect looks so simple, can have a remarkable impact on an entire field of science. In our case it offered a simple way to exact measurements of distances between defined species in the nanometer range. The current applications are mainly in determining structures of proteins and nucleic acids.     

0-extended supergravity and Chern-Simons theories

We give generalizations of extended Poincaré supergravity with arbitrarily many supersymmetries in the absence of central charges in three dimensions by gauging its intrinsic global SO(N) symmetry. We call these ₀ (Aleph-null) supergravity theories. We further couple a non-Abelian supersymmetric Chern-Simons theory and an Abelian topological BF theory to ₀ supergravity. Our result overcomes the previous difficulty for supersymmetrization of Chern-Simons theories beyond N = 4. This feature is peculiar to the Chern-Simons and BF theories including supergravity in three dimensions. We also show that dimensional reduction schemes for four-dimensional theories such as N = 1 self-dual supersymmetric Yang-Mills theory or N = 1 supergravity theory that can generate ₀ globally and locally supersymmetric theories in three dimensions. As an interesting application, we present ₀ supergravity Liouville theory in two dimensions after appropriate dimensional reduction from three dimensions.     

A quantum-chemical study of LiC=O interactions in polyester-based polymer electrolytes

Quantum-chemical calculations on model ester molecules have been performed to study the interactions of carbonyl groups with lithium cation. The preferred conformations of the complexes and their stabilization energies have been determined. The largest complexation energy has been obtained for Li⁺ binding to four carbonyl groups. The vibrational frequency calculations have been used to predict the changes in the IR spectrum of polyester upon Li⁺ complexation. For the most stable complex the red-shift of about − 29 to − 24 cm^− 1 in the frequency of the C=O stretching mode has been calculated in a good agreement with the experimental value [I.D. Wu, F. C. Chang, Polymer 48 (2007) 989].     

Voice source characteristics in Mongolian "throat singing" studied with high-speed imaging technique, acoustic spectra, and inverse filtering.

Mongolian "throat singing" can be performed in different modes. In Mongolia, the bass-type is called Kargyraa. The voice source in bass-type throat singing was studied in one male singer. The subject alternated between modal voice and the throat singing mode. Vocal fold vibrations were observed with high-speed photography, using a computerized recording system. The spectral characteristics of the sound signal were analyzed. Kymographic image data were compared to the sound signal and flow inverse filtering data from the same singer were obtained on a separate occasion. It was found that the vocal folds vibrated at the same frequency throughout both modes of singing. During throat singing the ventricular folds vibrated with complete but short closures at half the frequency of the true vocal folds, covering every second vocal fold closure. Kymographic data confirmed the findings. The spectrum contained added subharmonics compared to modal voice. In the inverse filtered signal the amplitude of every second airflow pulse was considerably lowered. The ventricular folds appeared to modulate the sound by reducing the glottal flow of every other vocal fold vibratory cycle.