Novel Aspects on Motor Neuron Disease: The Recent Genetic Studies on ALS

At present, with the advanced affordable genetic testing, the rate of discovering amyotrophic lateral sclerosis (ALS)-related genes rapidly increases. These genetic findings provide new insights into therapies that target genetic subset of ALS. However, the research on the genetic and environmental causes of ALS is still in the early stage. In this chapter, we review the current understanding of ALS-related genes and summarize the worldwide ALS distribution feature by the frequency of occurrence in different regions. We summarize the advances in genetic testing and counseling for ALS. Based on the increase in genetic testing, we believe that the ALS patients and families would be benefited from our studies in the near future

Anisotropic optical properties of rhombohedral and tetragonal thin film BiFeO3_3 phases

The anisotropic optical properties of multiferroic BiFeO$_3$ thin films have been determined with Mueller matrix ellipsometry at room-temperature. The full dielectric tensors of tetragonal-like and rhombohedral-like BiFeO$_3$ phases epitaxially grown on LaAlO$_3$ and SrTiO$_3$ single crystal substrates, respectively, within the spectral range of 0.6 and 6.5 eV are reported. Strain-driven anisotropy changes and transition shifts are observed as well as evidence of sub-band gap many-particle excitations are found. The transition shifts, mostly to higher energies for the highly strained tetragonal-like BiFeO$_3$ phase on LaAlO$_3$, are indicative of band structure differences. Additionally, optical modelling, confirmed by piezoelectric force microscopy studies, revealed that the average polarization direction of bivariant BiFeO$_3$ on LaAlO$_3$ is not parallel to the crystallographic [001] direction but tilted by about $7^{\circ}$. Spectral weight analyses reveal phase-dependent differences underlining that theoretical calculations of optical spectra need further improvement to appropriately account for electronic and excitonic correlations to fully understand multiferroic BiFeO$_3$.Comment: 7 pages, 5 figure

Deposition and Characterization of Multiferroic BiFeO3 Thin Films

Multiferroics, defined as materials with coexistence of at least two of the electric, elastic, and magnetic orders, have attracted enormous research activities recently. A subsystem of multiferroics is the ferroelectromagnet, which possesses both electric and magnetic orders. One of the natural ferroelectromagnets is BiFeO3, which has ferroelectric (TC~1100K) and antiferromagnetic (TN~640K) orders at room temperature. Even though bulk samples have been synthesized back in 1950s, characterizations of its intrinsic properties have been difficult due to poor sample quality. This work is the first study on epitaxial BiFeO3 thin films. Highly resistive films have been prepared using Pulsed Laser Deposition. (001), (110) and (111) cut SrTiO3 substrates were used to control the film orientation. Film structures were characterized using both X-ray diffraction and transmission electron microscope. It was found that epitaxial stress changes the film structure. Monoclinic domain splitting was observed from both (101) and (001) oriented films, while (111) films remain rhombohedral similliar to single crystals. Much larger polarizations were observed for all three orientations (~55 C/cm2 for (001) films, ~80 C/cm2 for (101) films, and ~100 C/cm2 for (111) films). Calculation using the effective charges and reported ion displacements is performed; indicating that the large observed polarization is likely the intrinsic property of BiFeO3. Magnetic measurements reveal that these resistive BiFeO3 thin films show hysteresis behavior at room temperature, which was not observed in bulk single crystal under the same field range. Thickness dependence of the magnetic property was studied. It is proposed that epitaxial stress destroys the cycloidal spin structure of BiFeO3, releasing the weak ferromagnetic property due to spin canting. In addition, integration of BiFeO3 with Si using SrTiO3 template layer was also studied. Large dielectric constant and piezoelectric coefficients were observed, showing promise for applications in MEMs and actuators