Coupled magnetic-ferroelectric metal-insulator transitions in epitaxially-strained SrCoO3_{3} from first principles

First-principles calculations of the epitaxial-strain phase diagram of perovskite SrCoO$_{3}$ are presented. Through combination of the large spin-phonon coupling with polarization-strain coupling and coupling of the band gap to the polar distortion, both tensile and compressive epitaxial strain are seen to drive the bulk ferromagnetic-metallic (FM-M) phase to antiferromagnetic-insulating-ferroelectric (AFM-I-FE) phases, the latter having unusually low elastic energy. At these coupled magnetic-ferroelectric metal-insulator phase boundaries, cross responses to applied electric and magnetic fields and stresses are expected. In particular, a magnetic field or compressive uniaxial stress applied to the AFM phases could induce an insulator-metal transition, and an electric field applied to the FM-M phase could induce a metal-insulator transition.Comment: 2 figures and 1 tabl

Epitaxial-strain-induced multiferroicity in SrMnO3_{3} from first principles

First-principles density-functional calculations reveal a large spin-phonon coupling in cubic SrMnO$_{3}$, with ferromagnetic ordering producing a polar instability. Through combination of this coupling with the strain-polarization coupling characteristic of perovskites, the bulk antiferromagnetic paraelectric ground state of SrMnO$_3$ is shown to be driven to a previously unreported multiferroic ferroelectric-ferromagnetic state by increasing epitaxial strain, both tensile and compressive. This state has a computed polarization and estimated Curie temperature above 54 $\mu$C/cm$^2$ and 92 K. Large mixed magnetic-electric-elastic responses are predicted in the vicinity of the phase boundaries.Comment: 5 pages, 2 figures, 1 tabl

Epidemiological Aspects of Exotic Malaria and Dengue Fever in Travelers in Korea

In order to compare the epidemiological aspects of exotic malaria (EM) and dengue fever (DF) imported by travelers in Korea, we have analyzed the current state both of the disease incidence and related risk factors. A total of 345 cases of EM occurred between 2001 and 2008 in Korea, and the average incidence rate per 100,000 population was 0.091. A total of 252 of DF cases occurred during the same period, and its rate was 0.063. While most of the EM and DF prevalence occurred in summer, prevalence in spring and winter was more prominent for EM (P < 0.05 ~ P < 0.01), while outbreaks in summer were more frequent for DF (P < 0.01). In Korea, more males were infected with EM and DF than females (P < 0.01). The remarkable difference between gender distributions in Korea is believed to reflect cultural differences in terms of work and travel. In both diseases, the manhood age bracket (20 - 39 years old) is possible due to increased oversea activities and travel. Moreover, reported EM cases in several prefectures in the regions of Asia and Africa were widely spread by the appropriate vector of mosquitoes, while the vectors of DF in the region of Asia are limited

Role of Myokines in Regulating Skeletal Muscle Mass and Function

Loss of skeletal muscle mass and strength has recently become a hot research topic with the extension of life span and an increasingly sedentary lifestyle in modern society. Maintenance of skeletal muscle mass is considered an essential determinant of muscle strength and function. Myokines are cytokines synthesized and released by myocytes during muscular contractions. They are implicated in autocrine regulation of metabolism in the muscle as well as in the paracrine/endocrine regulation of other tissues and organs including adipose tissue, the liver, and the brain through their receptors. Till date, secretome analysis of human myocyte culture medium has revealed over 600 myokines. In this review article, we summarize our current knowledge of major identified and characterized myokines focusing on their biological activity and function, particularly in muscle mass and function

First-principles approach to the dynamic magnetoelectric couplings for the non-reciprocal directional dichroism in BiFeO3

Due to the complicated magnetic and crystallographic structures of BiFeO3, its magnetoelectric (ME) couplings and microscopic model Hamiltonian remain poorly understood. By employing a first-principles approach, we uncover all possible ME couplings associated with the spin-current (SC) and exchange-striction (ES) polarizations, and construct an appropriate Hamiltonian for the long-range spin-cycloid in BiFeO3. First-principles calculations are used to understand the microscopic origins of the ME couplings. We find that inversion symmetries broken by ferroelectric and antiferroelectric distortions induce the SC and the ES polarizations, which cooperatively produce the dynamic ME effects in BiFeO3. A model motivated by first principles reproduces the absorption difference of counter-propagating light beams called non-reciprocal directional dichroism. The current paper focuses on the spin-driven (SD) polarizations produced by a dynamic electric field, i.e. the dynamic ME couplings. Due to the inertial properties of Fe, the dynamic SD polarizations differ significantly from the static SD polarizations. Our systematic approach can be generally applied to any multiferroic material, laying the foundation for revealing hidden ME couplings on the atomic scale and for exploiting optical ME effects in the next generation of technological devices such as optical diodes.ope