A quasi-time-dependent radiative transfer model of OH104.9+2.4

We investigate the pulsation-phase dependent properties of the circumstellar dust shell (CDS) of the OH/IR star OH104.9+2.4 based on radiative transfer modeling (RTM) using the code DUSTY. Our previous study concerning simultaneous modeling of the spectral energy distribution (SED) and near-infrared (NIR) visibilities (Riechers et al. 2004) has now been extended by means of a more detailed analysis of the pulsation-phase dependence of the model parameters of OH104.9+2.4. In order to investigate the temporal variation in the spatial structure of the CDS, additional NIR speckle interferometric observations in the K' band were carried out with the 6 m telescope of the Special Astrophysical Observatory (SAO). At a wavelength of 2.12 micron the diffraction-limited resolution of 74 mas was attained. Several key parameters of our previous best-fitting model had to be adjusted in order to be consistent with the newly extended amount of observational data. It was found that a simple rescaling of the bolometric flux F_bol is not sufficient to take the variability of the source into account, as the change in optical depth over a full pulsation cycle is rather high. On the other hand, the impact of a change in effective temperature T_eff on SED and visibility is rather small. However, observations, as well as models for other AGB stars, show the necessity of including a variation of T_eff with pulsation phase in the radiative transfer models. Therefore, our new best-fitting model accounts for these changes.Comment: 7 pages, including 5 postscript figures and 3 tables. Published in Astronomy and Astrophysics. (v1: accepted version; v2: published version, minor grammatical changes

Fine tuning of Rac1 and RhoA alters cuspal shapes by remolding the cellular geometry

published_or_final_versio

Stripe structure, spectral feature and soliton gap in high Tc cuprates

We show that the lightly doped La_{2-x}Sr_{x}CuO_{4} can be described in terms of a stripe magnetic structure or soliton picture. The internal relationship between the recent neutron observation of the diagonal (x=0.05) to vertical (x >= 0.06) stripe transition, which was predicted, and the concomitant metal-insulator transition is clarified by this solitonic physics. The phase diagram with the unidentified transition lines between antiferromagnetic to stripe phases, the doping dependence of the modulation period, the origin of the mid-infrared optical absorption are investigated comparatively with other single layer systems: La_{2-x}Sr_{x}NiO_{4} and (La,Nd)_{2-x}Sr_{x}CuO_{4}. The novel type of quasi-particles and holes is fully responsible for metallic conduction and ultimately superconductivity.Comment: 4 pages RevTex, 5 figure

Interplay between carrier and impurity concentrations in annealed Ga1−x_{1-x}Mnx_{x}As intrinsic anomalous Hall Effect

Investigating the scaling behavior of annealed Ga$_{1-x}$Mn$_{x}$As anomalous Hall coefficients, we note a universal crossover regime where the scaling behavior changes from quadratic to linear, attributed to the anomalous Hall Effect intrinsic and extrinsic origins, respectively. Furthermore, measured anomalous Hall conductivities when properly scaled by carrier concentration remain constant, equal to theoretically predicated values, spanning nearly a decade in conductivity as well as over 100 K in T$_{C}$. Both the qualitative and quantitative agreement confirms the validity of new equations of motion including the Berry phase contributions as well as tunablility of the intrinsic anomalous Hall Effect.Comment: 4 pages, 5 figure

Shear stress fluctuations in the granular liquid and solid phases

We report on experimentally observed shear stress fluctuations in both granular solid and fluid states, showing that they are non-Gaussian at low shear rates, reflecting the predominance of correlated structures (force chains) in the solidlike phase, which also exhibit finite rigidity to shear. Peaks in the rigidity and the stress distribution's skewness indicate that a change to the force-bearing mechanism occurs at the transition to fluid behaviour, which, it is shown, can be predicted from the behaviour of the stress at lower shear rates. In the fluid state stress is Gaussian distributed, suggesting that the central limit theorem holds. The fibre bundle model with random load sharing effectively reproduces the stress distribution at the yield point and also exhibits the exponential stress distribution anticipated from extant work on stress propagation in granular materials.Comment: 11 pages, 3 figures, latex. Replacement adds journal reference and addresses referee comment

Suppression of Antiferromagnetic Order by Light Hole Doping in La_2Cu_{1-x}Li_xO_4: A ^{139}La NQR Study

^{139}La nuclear quadrupole resonance measurements in lightly doped La_2Cu_{1-x}Li_xO_4 have been performed to reveal the dependence of the magnetic properties of the antiferromagnetic CuO_2 planes on the character of the doped holes and their interactions with the dopant. A detailed study shows that the magnetic properties are remarkably insensitive to the character of the dopant impurity. This indicates that the added holes form previously unrecognized collective structures.Comment: 4 pages, 3 figures. Slightly modified version, as accepted for publication in Physical Review Letter

Phantom for Evaluating Accuracy of Image Registration Software

Provided is a phantom for evaluating the accuracy of image registration software based on a result of matching tomograms of a predetermined position of the phantom, taken using two or more imaging apparatuses. Accordingly, it is possible to more efficiently evaluate the accuracy of the image registration software by comparing the tomograms with one another using a three-dimensional analysis. In addition, it is possible to facilitate the comparison of the tomograms with one another by installing a plurality of indicating bars in the phantom so that their cross sections can appear on each of the tomograms

Spin Dynamics in the LTT Phase of ~1/8 Doped Single Crystal La_{1.67}Eu_{0.2}Sr_{0.13}CuO_4

We present La and Cu NMR relaxation measurements in single crystal La_{1.67}Eu_{0.2}Sr_{0.13}CuO_4. A strong peak in the La spin-lattice relaxation rate observed in the spin ordered state is well-described by the BPP mechanism[1] and arises from continuous slowing of electronic spin fluctuations with decreasing temperature; these spin fluctuations exhibit XY-like anisotropy in the ordered state. The spin pseudogap is enhanced by the static charge-stripe order in the LTT phase.Comment: Four pages, three figure

Superconductivity of the Sr2Ca12Cu24O41Sr_2 Ca_{12} Cu_{24} O_{41} spin ladder system: Are the superconducting pairing and the spin-gap formation of the same origin?

Pressure-induced superconductivity in a spin-ladder cuprate Sr$_2$Ca$_{12}$Cu$_{24}$O$_{41}$ has not been studied on a microscopic level so far although the superconductivity was already discovered in 1996. We have improved high-pressure technique with using a large high-quality crystal, and succeeded in studying the superconductivity using $^{63}$Cu nuclear magnetic resonance (NMR). We found that anomalous metallic state reflecting the spin-ladder structure is realized and the superconductivity possesses a s-wavelike character in the meaning that a finite gap exists in the quasi-particle excitation: At pressure of 3.5GPa we observed two excitation modes in the normal state from the relaxation rate $T_1^{-1}$. One gives rise to an activation-type component in $T_1^{-1}$, and the other $T$-linear component linking directly with the superconductivity. This gapless mode likely arises from free motion of holon-spinon bound states appearing by hole doping, and the pairing of them likely causes the superconductivity.Comment: to be published in Phys. Rev. Let