Fulde-Ferrell-Larkin-Ovchinnikov State in the absence of a Magnetic Field

We propose that in a system with pocket Fermi surfaces, a pairing state with a finite total momentum q_tot like the Fulde-Ferrell-Larkin-Ovchinnikov state can be stabilized even without a magnetic field. When a pair is composed of electrons on a pocket Fermi surface whose center is not located at Gamma point, the pair inevitably has finite q_tot. To investigate this possibility, we consider a two-orbital model on a square lattice that can realize pocket Fermi surfaces and we apply fluctuation exchange approximation. Then, by changing the electron number n per site, we indeed find that such superconducting states with finite q_tot are stabilized when the system has pocket Fermi surfaces.Comment: 4 pages, 5 figure

High Ratio of 44Ti/56Ni in Cas A and Axisymmetric Collapse-Driven Supernova Explosion

The large abundance ratio of $^{44}Ti/^{56}Ni$ in Cas A is puzzling. In fact, the ratio seems to be larger than the theoretical constraint derived by Woosley & Hoffman (1991). However, this constraint is obtained on the assumption that the explosion is spherically symmetric, whereas Cas A is famous for the asymmetric form of the remnant. Recently, Nagataki et al. (1997) calculated the explosive nucleosynthesis of axisymmetrically deformed collapse-driven supernova. They reported that the ratio of $^{44}Ti/^{56}Ni$ was enhanced by the stronger alpha-rich freezeout in the polar region. In this paper, we apply these results to Cas A and examine whether this effect can explain the large amount of $^{44}Ti$ and the large ratio of $^{44}Ti/^{56}Ni$. We demonstrate that the conventional spherically symmetric explosion model can not explain the $^{44}$Ti mass produced in Cas A if its lifetime is shorter than $\sim$ 80 years and the intervening space is transparent to the gamma-ray line from the decay of $^{44}$Ti. On the other hand, we show the axisymmetric explosion models can solve the problem. We expect the same effect from a three dimensionally asymmetric explosion, since the stronger alpha-rich freezeout will also occur in that case in the region where the larger energy is deposited.Comment: 10 pages, LaTeX text and 3 postscript figure

Dynamics of Multiferroic Domain Wall in Spin-Cycloidal Ferroelectric DyMnO3_{3}

We report the dielectric dispersion of the giant magnetocapacitance (GMC) in multiferroic DyMnO$_{3}$ over a wide frequency range. The GMC is found to be attributable not to the softened electromagnon but to the electric-field-driven motion of multiferroic domain wall (DW). In contrast to conventional ferroelectric DWs, the present multiferroic DW motion holds extremely high relaxation rate of $\sim$$10^{7}$ s$^{-1}$ even at low temperatures. This mobile nature as well as the model simulation suggests that the multiferroic DW is not atomically thin as in ferroelectrics but thick, reflecting its magnetic origin.Comment: 4 pages, 4 figure

Hydro-climatic variability and agricultural production on the shores of Lake Chad

The purpose of this study is to present and analyze previously unpublished quantitative agricultural data for the area on the shores of Lake Chad in Chad, and explore its relations to hydro-climatic factors (lake levels, rainfall and temperature). This is a rural area with livelihoods based on agropastoral and fishing activities, which are directly dependent on the region's high-varying hydro-climate. By using regression analysis on data from 1988-2012 this study was able to establish correlations between the latter and agricultural output. These correlations were used to build multivariate models to explore the predictive capacities of hydro-climatic factors with regards to the agricultural data. The selected models were able to account for considerable proportions of the agricultural dynamics. Some 5 of the 10 multivariate models tested had cross-validated R2s of 0.50 or more. Thus, there were still noteworthy unexplained variations in the agricultural data, which likely stem from technological, behavioral, economic and pest factors that were not explored in this study due do data limitations. Additional studies are called for to build on results presented here and further examine these relationships

Microscopic Model and Phase Diagrams of the Multiferroic Perovskite Manganites

Orthorhombically distorted perovskite manganites, RMnO3 with R being a trivalent rare-earth ion, exhibit a variety of magnetic and electric phases including multiferroic (i.e. concurrently magnetic and ferroelectric) phases and fascinating magnetoelectric phenomena. We theoretically study the phase diagram of RMnO3 by constructing a microscopic spin model, which includes not only the superexchange interaction but also the single-ion anisotropy (SIA) and the Dzyaloshinsky-Moriya interaction (DMI). Analysis of this model using the Monte-Carlo method reproduces the experimental phase diagrams as functions of the R-ion radius, which contain two different multiferroic states, i.e. the ab-plane spin cycloid with ferroelectric polarization P//a and the bc-plane spin cycloid with P//c. The orthorhombic lattice distortion or the second-neighbor spin exchanges enhanced by this distortion exquisitely controls the keen competition between these two phases through tuning the SIA and DMI energies. This leads to a lattice-distortion-induced reorientation of P from a to c in agreement with the experiments. We also discuss spin structures in the A-type antiferromagnetic state, those in the cycloidal spin states, origin and nature of the sinusoidal collinear spin state, and many other issues.Comment: 23 pages, 19 figures. Recalculated results after correcting errors in the assignment of Dzyaloshinsky-Moriya vector

Feeding-elicited cataplexy in orexin knockout mice

Mice lacking orexin/hypocretin signaling have sudden episodes of atonia and paralysis during active wakefulness. These events strongly resemble cataplexy, episodes of sudden muscle weakness triggered by strong positive emotions in people with narcolepsy, but it remains unknown whether murine cataplexy is triggered by positive emotions. To determine whether positive emotions elicit murine cataplexy, we placed orexin knockout (KO) mice on a scheduled feeding protocol with regular or highly palatable food. Baseline sleep/wake behavior was recorded with ad libitum regular chow. Mice were then placed on a scheduled feeding protocol in which they received 60% of their normal amount of chow 3 h after dark onset for the next 10 days. Wild-type and KO mice rapidly entrained to scheduled feeding with regular chow, with more wake and locomotor activity prior to the feeding time. On day 10 of scheduled feeding, orexin KO mice had slightly more cataplexy during the food-anticipation period and more cataplexy in the second half of the dark period, when they may have been foraging for residual food. To test whether more palatable food increases cataplexy, mice were then switched to scheduled feeding with an isocaloric amount of Froot Loops, a food often used as a reward in behavioral studies. With this highly palatable food, orexin KO mice had much more cataplexy during the food-anticipation period and throughout the dark period. The increase in cataplexy with scheduled feeding, especially with highly palatable food, suggests that positive emotions may trigger cataplexy in mice, just as in people with narcolepsy. Establishing this connection helps validate orexin KO mice as an excellent model of human narcolepsy and provides an opportunity to better understand the mechanisms that trigger cataplexy

DYNAMICAL FACTORS RELATED TO VERTICAL JUMP PERFOMANCE

INTRODUCTION - In most of sport exercises, the displacement of body Center of Mass (CM) is an important factor to de-terminate performance. And greater the velocity at takeoff phase, greater the height achieved by the body CM. High jumps are influenced by the net combination of different joints moments and its synchronization during this task. Thus, also the countermovement may influence high jump performance (HOCHMUTH & MARHOLD, 1978). To measure the effectiveness of training into increasing the height in vertical jump relays information to both coach and athlete in manner to adapt the training. The purpose of this study is to analyze temporal and frequencies factors of ground reaction force GRF and the effect of limitation of arms swing and trunk extension in vertical jump. METHODS AND EQUIPMENT - All the exercises were performed on a strain gauges force platform. The ground reaction force (GRF) had been sampled at 800 Hz frequency and after the determination of its frequency components by the use of FFT, the raw signals were low-pass filtered at 160 Hz. A video camera was exerted to control the set of jumps. The volunteer subject for this study was a male high jumper, 26 years old, 70.4f0.5 kg weight, 184.0k0.5 cm tall. Four different types of vertical jumps were performed (set of 5 trials) and analyzed in this study: 1) standard vertical jump; 2) jump with- out the elevation of upper limbs; 3) jump without the extension of trunk; and 4) jump without both the elevation of upper limbs and extension of trunk. All that jumps were preceded by countermovement. RESULTS AND DISCUSSION - Although four different techniques had been per- formed for high jumps, the temporal factors (DOWLINH & VAMOS, 1993) did not differ statistically (duration of major positive impulse and duration of major negative impulse). Eccentric and concentric phases was not different statistically. Power spectral analysis has showed that trunk mobility might be more influent than upper limb swing in the dynamic4 characteristics of the analyzed movement. Informations provided by spectral analysis probably relays important data to identify the influence of different body segments in vertical jump. It was not confirmed that the maintenance of a steady state just before the maximum vertical GRF or reducing the depression between the two positive peaks is related to the acceleration caused by arms swing. On the other hand, our results indicate that the first positive peak is probably exerted by trunk extension. In spite of the limitation of trunk and upper limb mobility, it is clear that is not possible to exclude their influence in total body moment of inertia. CONCLUSION - According to our results, despite different jumping exercises, restrictions to joints mobility changes the maxi- mum vertical GRF. Besides, tests that intend to measure the performance in high jumps according the use or not of parts of the human body may be reconsidered. REFERENCES Hochmuth G.; Marhold G. (1983) In Asmussen E. Jagenssen K. Biomechanics VI B. Dowling J.J.; Vamos L. (1 9933 J. Applied. Biornech. 9, 95-110

Origin of G-type Antiferromagnetism and Orbital-Spin Structures in LaTiO3{\rm LaTiO}_3

The possibility of the $D_{3d}$ distortion of ${\rm TiO}_6$ octahedra is examined theoretically in order to understand the origin of the G-type antiferromagnetism (AFM(G)) and experimentally observed puzzling properties of ${\rm LaTiO}_3$. By utilizing an effective spin and pseudospin Hamiltonian with the strong Coulomb repulsion, it is shown that AFM(G) state is stabilized through the lift of the $t_{2g}$-orbital degeneracy accompanied by a tiny $D_{3d}$-distortion . The estimated spin-exchange interaction is in agreement with that obtained by the neutron scattering. Moreover, the level-splitting energy due to the distortion can be considerably larger than the spin-orbit interaction even when the distortion becomes smaller than the detectable limit under the available experimental resolution. This suggests that the orbital momentum is fully quenched and the relativistic spin-orbit interaction is not effective in this system, in agreement with recent neutron-scattering experiment.Comment: 9 pages, 6 figure

G-type antiferromagnetism and orbital ordering due to the crystal field from the rare-earth ions induced by the GdFeO_3-type distortion in RTiO_3 with R=La, Pr, Nd and Sm

The origin of the antiferromagnetic order and puzzling properties of LaTiO_3 as well as the magnetic phase diagram of the perovskite titanates are studied theoretically. We show that in LaTiO_3, the t_{2g} degeneracy is eventually lifted by the La cations in the GdFeO_3-type structure, which generates a crystal field with nearly trigonal symmetry. This allows the description of the low-energy structure of LaTiO_3 by a single-band Hubbard model as a good starting point. The lowest-orbital occupation in this crystal field stabilizes the AFM(G) state, and well explains the spin-wave spectrum of LaTiO_3 obtained by the neutron scattering experiment. The orbital-spin structures for RTiO_3 with R=Pr, Nd and Sm are also accounted for by the same mechanism. We point out that through generating the R crystal field, the GdFeO_3-type distortion has a universal relevance in determining the orbital-spin structure of the perovskite compounds in competition with the Jahn-Teller mechanism, which has been overlooked in the literature. Since the GdFeO_3-type distortion is a universal phenomenon as is seen in a large number of perovskite compounds, this mechanism may also play important roles in other compounds of this type.Comment: 20 pages, 15 figure

59Co Nuclear Quadrupole Resonance Studies of Superconducting and Non-superconducting Bilayer Water Intercalated Sodium Cobalt Oxides NaxCoO2.yH2O

We report 59Co nuclear quadrupole resonance (NQR) studies of bilayer water intercalated sodium cobalt oxides NaxCoO2.yH2O (BLH) with the superconducting transition temperatures, 2 K < T_c <= 4.6 K, as well as a magnetic BLH sample without superconductivity. We obtained a magnetic phase diagram of T_c and the magnetic ordering temperature T_M against the peak frequency nu_3 59Co NQR transition I_z = +- 5/2 +-7/2 and found a dome shape superconducting phase. The 59Co NQR spectrum of the non-superconducting BLH shows a broadening below T_M without the critical divergence of 1/T_1 and 1/T_2, suggesting an unconventional magnetic ordering. The degree of the enhancement of 1/T_1T at low temperatures increases with the increase of nu_3 though the optimal nu_3~12.30 MHz. In the NaxCoO2.yH2O system, the optimal-T_c superconductivity emerges close to the magnetic instability. T_c is suppressed near the phase boundary at nu_3~12.50 MHz, which is not a conventional magnetic quantum critical point.Comment: 4 pages, 5 figure