Precise determination of two-carrier transport properties in the topological insulator TlBiSe2_2

We report the electric transport study of the three-dimensional topological insulator TlBiSe$_2$. We applied a newly developed analysis procedure and precisely determined two-carrier transport properties. Magnetotransport properties revealed a multicarrier conduction of high- and low-mobility electrons in the bulk, which was in qualitative agreement with angle-resolved photoemission results~[K. Kuroda $et~al.$, Phys. Rev. Lett. $\bm{105}$, 146801 (2010)]. The temperature dependence of the Hall mobility was explained well with the conventional Bloch-Gr{\"u}neisen formula and yielded the Debye temperature $\varTheta_{\rm{D}}=113 \pm 14$~K. The results indicate that the scattering of bulk electrons is dominated by acoustic phonons.Comment: 6 pages, 5 figures, to be published in Physical Review

Real-space observation of current-driven domain wall motion in submicron magnetic wires

Spintronic devices, whose operation is based on the motion of a magnetic domain wall (DW), have been proposed recently. If a DW could be driven directly by flowing an electric current instead of a magnetic field, the performance and functions of such device would be drastically improved. Here we report real-space observation of the current-driven DW motion by using a well-defined single DW in a micro-fabricated magnetic wire with submicron width. Magnetic force microscopy (MFM) visualizes that a single DW introduced in the wire is displaced back and forth by positive and negative pulsed-current, respectively. We can control the DW position in the wire by tuning the intensity, the duration and the polarity of the pulsed-current. It is, thus, demonstrated that spintronic device operation by the current-driven DW motion is possible.Comment: Accepted and published in PR

Propagation of a magnetic domain wall in magnetic wires with asymmetric notches

The propagation of a magnetic domain wall (DW) in a submicron magnetic wire consisting of a magnetic/nonmagnetic/magnetic trilayered structure with asymmetric notches was investigated by utilizing the giant magnetoresistance effect. The propagation direction of a DW was controlled by a pulsed local magnetic field, which nucleates the DW at one of the two ends of the wire. It was found that the depinning field of the DW from the notch depends on the propagation direction of the DW.Comment: 12 pages, 3 figure

Caffeine intake and the risk of chronic obstructive pulmonary disease in Japanese adults

Background: To investigate the association between caffeine intake and the risk of developing chronic obstructive pulmonary disease (COPD) among Japanese older adults, a case–control study was conducted in central Japan. Methods: A total of 277 patients with COPD aged 50 to 75 years were referred by respiratory physicians, while 340 controls were recruited from the community. All participants had their disease status confirmed by spirometry. Information on habitual caffeine intake, demographic, and lifestyle characteristics was obtained by face-to-face interview using a validated questionnaire. Results: The COPD patients drank more coffee and had a higher mean caffeine intake (311.3, SD 176.2mg/day) than the control group (278.4, SD 188.1 mg/day), p = 0.03. Relative to nondrinkers, the risk of COPD apparently increased for those drinking at least two cups of coffee daily (adjusted odds ratio 1.58, 95% confidence interval [CI] 0.93 to 2.71). Similarly, total caffeine intake was associated with the prevalence of COPD—the adjusted odds ratio being 1.30 (95% CI 1.09 to 2.12) for consuming over 312mg/day when compared to a low intake of less than 184mg/day. Conclusions: The epidemiological evidence suggested a positive association between caffeine intake and the development of COPD in Japanese adults. Further study of the effect of caffeine on lung function and the risk of COPD should be undertaken

Breakdown of a conservation law in incommensurate systems

We show that invariance properties of the Lagrangian of an incommensurate system, as described by the Frenkel Kontorova model, imply the existence of a generalized angular momentum which is an integral of motion if the system remains floating. The behavior of this quantity can therefore monitor the character of the system as floating (when it is conserved) or locked (when it is not). We find that, during the dynamics, the non-linear couplings of our model cause parametric phonon excitations which lead to the appearance of Umklapp terms and to a sudden deviation of the generalized momentum from a constant value, signalling a dynamical transition from a floating to a pinned state. We point out that this transition is related but does not coincide with the onset of sliding friction which can take place when the system is still floating.Comment: 7 pages, 6 figures, typed with RevTex, submitted to Phys. Rev. E Replaced 27-03-2001: changes to text, minor revision of figure

Effect of Joule heating in current-driven domain wall motion

It was found that high current density needed for the current-driven domain wall motion results in the Joule heating of the sample. The sample temperature, when the current-driven domain wall motion occurred, was estimated by measuring the sample resistance during the application of a pulsed-current. The sample temperature was 750 K for the threshold current density of 6.7 x 10^11 A/m2 in a 10 nm-thick Ni81Fe19 wire with a width of 240 nm. The temperature was raised to 830 K for the current density of 7.5 x 10^11 A/m2, which is very close to the Curie temperature of bulk Ni81Fe19. When the current density exceeded 7.5 x 10^11 A/m2, an appearance of a multi-domain structure in the wire was observed by magnetic force microscopy, suggesting that the sample temperature exceeded the Curie temperature.Comment: 13 pages, 4 figure

Evolution and stability of a magnetic vortex in small cylindrical ferromagnetic particle under applied field

The energy of a displaced magnetic vortex in a cylindrical particle made of isotropic ferromagnetic material (magnetic dot) is calculated taking into account the magnetic dipolar and the exchange interactions. Under the simplifying assumption of small dot thickness the closed-form expressions for the dot energy is written in a non-perturbative way as a function of the coordinate of the vortex center. Then, the process of losing the stability of the vortex under the influence of the externally applied magnetic field is considered. The field destabilizing the vortex as well as the field when the vortex energy is equal to the energy of a uniformly magnetized state are calculated and presented as a function of dot geometry. The results (containing no adjustable parameters) are compared to the recent experiment and are in good agreement.Comment: 4 pages, 2 figures, RevTe

Identification of plant genetic resources with high potential contribution to soil fertility enhancement in the Sahel, with special interest in fallow vegetation

The sandy soil in the Sahel is characterized as low inherent fertility, that is, having nutrient deficiency (total N and available P), low organic matter and high risk of erosion. Under the concept of integrated soil fertility management (ISFM), possible contribution of natural inhabitant plants to the improvement of soil fertility in the Sahel was evaluated. A broad variation in δ 15N values was observed among the plant species commonly found in cropland and fallow land of the Sahelian zone. Annual leguminous herbs, Cassia mimosoides (Caesalpiniaceae) and Alysicarpus ovalifolius (Papilionaceae), had low δ 15N values, showing their higher dependency on biological nitrogen fixation. They will be efficiently utilized as an extensive means of soil fertility management, for example, through more encouraged incorporation into the fallow vegetation. Ctenium elegans, Eragrostis tremula and Schizachyrium exile, greatly dominating annual grass species in the fallow land, though their δ 15N values were high, would contribute to the soil fertility by supplying a significant amount of organic matte