Phase synchronization between collective rhythms of globally coupled oscillator groups: noiseless nonidentical case

We theoretically study the synchronization between collective oscillations exhibited by two weakly interacting groups of nonidentical phase oscillators with internal and external global sinusoidal couplings of the groups. Coupled amplitude equations describing the collective oscillations of the oscillator groups are obtained by using the Ott-Antonsen ansatz, and then coupled phase equations for the collective oscillations are derived by phase reduction of the amplitude equations. The collective phase coupling function, which determines the dynamics of macroscopic phase differences between the groups, is calculated analytically. We demonstrate that the groups can exhibit effective antiphase collective synchronization even if the microscopic external coupling between individual oscillator pairs belonging to different groups is in-phase, and similarly effective in-phase collective synchronization in spite of microscopic antiphase external coupling between the groups.     

Entropy balance in distributed reversible Gray-Scott model

A practical way to calculate the entropy change in the distributed media composed of reversible Gray-Scott model is demonstrated. The entropy change is given as the sum of the entropy production and the divergence of entropy flow. The divergence of entropy is calculated based on the chemical potential of steady state. It becomes evident that: (i) the entropy change for the emergence of dissipative structures in the open system can be positive or negative, (ii) most of the entropy produced inside the system is thrown out to the environment when dissipative structures are developing, (iii) the entropy production and the divergence of entropy flow balance completely, when the system shows static steady states, (iv) the entropy change behaves as if it is the time derivative of the entropy production. Prior to these calculations of entropy balance, the features of emergent patterns in the two-dimensional system are examined in terms of entropy production solely. The results imply that the entropy production can be an index for us to discriminate spatial patterns, but is not a global thermodynamic potential for the evolution of dissipative structures.     

Exclusive Observation of the (132R)-Enantiomer of Chlorophyll-c from a Diatom Chaetoseros calcitrans

Chiral high-performance liquid-chromatography (HPLC) for quantitative analysis of optically active chlorophyll(Chl)-c molecules, which are seen in many marine photosynthetic organisms, was developed. Chls-c have a single asymmetric carbon at the 13²-position, so their stereoisomers are (13²R)- and (13²S)-enantiomers. After the separation of each enantiomer, the stereochemistry was unambiguously characterized using its circular dichroism spectrum in comparison with that of the structure-related compound, protochlorophyllide-a. Moreover, Chls-c were carefully extracted from the cells of a diatom Chaetoseros calcitrans without racemization and were subjected to the chiral HPLC. The results clearly demonstrated that naturally occurring Chl-c molecules are enantiomerically pure (13²R)-forms, which are generally found in photosynthetically active chlorophyllous pigments.     

High Field ESR System and Its Application to the Study of Quantum Spin Systems

Developments of the high field ESR system in Kobe University is presented. Using Gunn oscillators and backward traveling oscillators (BWO), we can cover the frequency region from 30 to 1183.6 GHz with the use of InSb detector. Pulsed magnetic field up to 30 T is available and we are now trying to extend the field up to 40 T. Temperature range is from 1.8 to 300 K. Using this system, we studied S=1/2 ladder like system Cu₂(C₅H₁₂N₂)₂Cl₄, and found a new magnetic transition at 10.1 T at 1.8 K. The temperature dependence of ESR in Cu₂(C₅H₁₂N₂)₂CI₄ shows g-shift below 8 K which corresponds to the maximum of the magnetic susceptibility. The g-shift below 8 K suggests the increase of the quantum fluctuation in the system, and the role of the quantum fluctuation in Cu₂(C₅H₁₂N₂)₂CI₄ is discussed.     

Mutual-probability prediction and higher-order correlation effects among acoustic,light and electromagnetic waves in a video display terminal environment

A probabilistic signal processing method, with which is possible to get some methodological suggestion to the measurement method of correlative and/or accumulative effects in the compound environment of sound, light and electromagnetic (EM) waves is discussed. In order to extract various types of latent interrelation characteristics among wave environmental factors leaked from an actually operating video display terminal (VDT), an extended regression system model, hierarchically reflecting not only linear correlation information but also nonlinear correlation information, is first introduced, especially from a viewpoint of ‘relationism-first’. Then, through estimating each regression parameter of this model, some original evaluation methods for predicting a whole probability distribution form, from one another, are proposed. Finally, the effectiveness of the methods is experimentally confirmed, by applying them to the actual observed data leaked by a VDT with some television games. To cite this article: M. Ohta et al., C. R. Mecanique 333 (2005).     

Synthesis and properties of σ–π conjugated alternating polymers consisting of carbazole and organosilicon units

We have synthesized novel σ–π conjugated polymers with an alternating organosilanylene and π‐electron system, intending to utilize them for hole‐transporting materials of electroluminescent (EL) devices. 3,6‐Di(lithioethynyl)carbazoles were co‐polymerized with organodichlorosilanes to give the corresponding polymers with molecular weights of M_W = 2000–5000. Another type of polymer with a thienylene unit was also synthesized by the nickel‐catalyzed reaction of the di‐Grignard reagent of 1,2‐bis[2‐(5‐bromothienyl)]tetraethyldisilane with 3,6‐dibromocarbazole, the molecular weight being M_n = 3100. The EL devices with a double‐layer system composed of tris(8‐quinolinolato)aluminum(III) and the present polymers as the emitting‐electron‐transporting and hole‐transporting layers, respectively, emit green EL with a maximum intensity of the order of 10³ cd m^?2. Of these, the device with the thienylene–carbazole polymers exhibited the highest luminance of 1480 cd m^?2. Copyright © 2001 John Wiley & Sons, Ltd.     

Flattening of micro-structured Si surfaces by hydrogen annealing

We report atomic scale flattening of surfaces of microstructures formed on Si wafers by furnace annealing. To avoid thermal deformation of the fabricated structures, advantage was taken of hydrogen annealing, which enables us to decrease the relaxation rate of Si surfaces due to surface hydrogenation. We examined cross-sectional shape and sidewall morphology of 3 μm deep trenches on Si(0 0 1) substrates after annealing at 1000 °C under various H₂ pressures of 40-760 Torr. We successfully formed Si trenches with flat surfaces composed of terraces and steps while preserving the designed trench profile by increasing H₂ pressure to 760 Torr.