Impurity-doping induced ferroelectricity in frustrated antiferromagnet CuFeO2

Dielectric responses have been investigated on the triangular-lattice antiferromagnet CuFeO2 and its site-diluted analogs CuFe1-xAlxO2 (x=0.01 and 0.02) with and without application of magnetic field. We have found a ferroelectric behavior at zero magnetic field for x=0.02. At any doping level, the onset field of the ferroelectricity always coincides with that of the noncollinear magnetic structure while the transition field dramatically decreases to zero field with Al doping. The results imply the further possibility of producing the ferroelectricity by modifying the frustrated spin structure in terms of site-doping and external magnetic field.Comment: 4 pages, 4 figure

Acceleration disturbances due to local gravity gradients in ASTROD I

The Astrodynamical Space Test of Relativity using Optical Devices (ASTROD) mission consists of three spacecraft in separate solar orbits and carries out laser interferometric ranging. ASTROD aims at testing relativistic gravity, measuring the solar system and detecting gravitational waves. Because of the larger arm length, the sensitivity of ASTROD to gravitational waves is estimated to be about 30 times better than Laser Interferometer Space Antenna (LISA) in the frequency range lower than about 0.1 mHz. ASTROD I is a simple version of ASTROD, employing one spacecraft in a solar orbit. It is the first step for ASTROD and serves as a technology demonstration mission for ASTROD. In addition, several scientific results are expected in the ASTROD I experiment. The required acceleration noise level of ASTROD I is 10^-13 m s^-2 Hz^{-1/2} at the frequency of 0.1 mHz. In this paper, we focus on local gravity gradient noise that could be one of the largest acceleration disturbances in the ASTROD I experiment. We have carried out gravitational modelling for the current test-mass design and simplified configurations of ASTROD I by using an analytical method and the Monte Carlo method. Our analyses can be applied to figure out the optimal designs of the test mass and the constructing materials of the spacecraft, and the configuration of compensation mass to reduce local gravity gradients.Comment: 6 pages, presented at the 6th Edoardo Amaldi Conference (Okinawa Japan, June 2005); to be published in Journal of Physics: Conference Serie

Universal scaling for the spin-electricity conversion on surface states of topological insulators

We have investigated spin-electricity conversion on surface states of bulk-insulating topological insulator (TI) materials using a spin pumping technique. The sample structure is Ni-Fe|Cu|TI trilayers, in which magnetic proximity effects on the TI surfaces are negligibly small owing to the inserted Cu layer. Voltage signals produced by the spin-electricity conversion are clearly observed, and enhanced with decreasing temperature in line with the dominated surface transport at lower temperatures. The efficiency of the spin-electricity conversion is greater for TI samples with higher resistivity of bulk states and longer mean free path of surface states, consistent with the surface spin-electricity conversion

Diabetes Mellitus in South Asia

The prevalence rates of diabetes mellitus and its complications in South Asia are much higher than in other developed and developing countries; therefore, diabetes mellitus has become a serious problem in this region. While the prevalence of diabetes mellitus in South Asia is remarkable, its characteristics and causes have not been well-elucidated. More than 85% of the diabetic population in South Asia suffer from type 2 diabetes, and the causes can be divided into two categories: internal/traditional causes and causes induced by rapid development. Factors such as age, gender, diet and lifestyle changes, including a lack of physical activity caused by modernization and urbanization, are major contributory factors. The majority of the healthcare costs associated with diabetes are due to its later complications and are not preventable. Therefore, inexpensive treatment at an early stage of diabetes is important. In this review, the following are recommended as preventive measures of the incidence of the disease: (1) induction of UCP1 through the diet, (2) increasing the intake of antidiabetic bioactive components and/or food and (3) evolution of the consensus through educational programs and government policy. National strategies and interventions should be implemented immediately for both the primary and secondary prevention of diabetes mellitus and its complications in order to advocate healthy living among the South Asian populations

Hall effect of spin-chirality origin in a triangular-lattice helimagnet Fe1.3Sb

We report on a topological Hall effect possibly induced by scalar spin chirality in a quasi-two- dimensional helimagnet Fe$_{1+x}$Sb. In the low-temperature region where the spins on interstitial- Fe (concentration $x=0.3$) intervening the $120^\circ$ spin-ordered triangular planes tend to freeze, a non-trivial component of Hall resistivity with opposite sign of the conventional anomalous Hall term is observed under magnetic field applied perpendicular to the triangular-lattice plane. The observed unconventional Hall effect is ascribed to the scalar spin chirality arising from the heptamer spin-clusters around the interstitial-Fe sites, which can be induced by the spin modulation by the Dzyaloshinsky-Moriya interaction