Energy relaxation in disordered charge and spin density waves

We investigate collective effects in the strong pinning model of disordered charge and spin density waves (CDWs and SDWs) in connection with heat relaxation experiments. We discuss the classical and quantum limits that contribute to two distinct contribution to the specific heat (a $C_v \sim T^{-2}$ contribution and a $C_v \sim T^{\alpha}$ contribution respectively), with two different types of disorder (strong pinning versus substitutional impurities). From the calculation of the two level system energy splitting distribution in the classical limit we find no slow relaxation in the commensurate case and a broad spectrum of relaxation times in the incommensurate case. In the commensurate case quantum effects restore a non vanishing energy relaxation, and generate stronger disorder effects in incommensurate systems. For substitutional disorder we obtain Friedel oscillations of bound states close to the Fermi energy. With negligible interchain couplings this explains the power-law specific heat $C_v \sim T^{\alpha}$ observed in experiments on CDWs and SDWs combined to the power-law susceptibility $\chi(T)\sim T^{-1+\alpha}$ observed in the CDW o-TaS$_3$.Comment: 13 pages, 10 figures, improvements in the presentatio

Strong-Pinning Effects in Low-Temperature Creep: Charge-Density Waves in TaS_3

Nonlinear conduction in the quasi-one dimensional conductor o-TaS_3 has been studied in the low-temperature region down to 30 mK. It was found that at temperatures below a few Kelvins the current-voltage (I-V) characteristics consist of several branches. The temperature evolution of the I-V curve proceeds through sequential freezing-out of the branches. The origin of each branch is attributed to a particular strong pinning impurity type. Similar behavior is expected for other physical systems with collective transport (spin-density waves, Wigner crystals, vortex lattices in type-II superconductors etc.) in the presence of strong pinning centers.Comment: 11 pages, 3 ps figures, Revtex, To be published in Phys. Rev. Letters (1997

〈論文・報告〉希土類元素一タンパク質--SDBS系の蛍光特性を利用したタンパク質の検出

[概要]希土類元素--タンパク質--ドデシルベンゼンスルホン酸ナトリウム(SDBS)系における蛍光増感効果を調べた。Tb^3+-SDBS-タンパク質系の蛍光は大変弱い。しかしながら、この系にGd^3+やエタノールを加えると、蛍光が著しく増加した。 コラーゲンの場合には、この効果が最大であった。この結果をもとに、タンパク質をナノグラム/mlレベルで感度良く検出する方法を確立した。 [Abstract] The fluorescence enhancement effect in rare earth-protein-sodium dodecyl benzenesulfonate (SDBS) system has been studied. The photoluminescence of Tb^3+-SDBS-protein system was very weak. However, when Gd^3+or ethanol was added into this system, the fluorescence was significantly enhanced. In the case of collagen, this effect was greatest. Based on this, a method was established to determine proteins sensitively at nanogram/ml level