Metabolic control of mitochondrial biogenesis through the PGC-1 family regulatory network

AbstractThe PGC-1 family of regulated coactivators, consisting of PGC-1α, PGC-1β and PRC, plays a central role in a regulatory network governing the transcriptional control of mitochondrial biogenesis and respiratory function. These coactivators target multiple transcription factors including NRF-1, NRF-2 and the orphan nuclear hormone receptor, ERRα, among others. In addition, they themselves are the targets of coactivator and co-repressor complexes that regulate gene expression through chromatin remodeling. The expression of PGC-1 family members is modulated by extracellular signals controlling metabolism, differentiation or cell growth and in some cases their activities are known to be regulated by post-translational modification by the energy sensors, AMPK and SIRT1. Recent gene knockout and silencing studies of many members of the PGC-1 network have revealed phenotypes of wide ranging severity suggestive of complex compensatory interactions or broadly integrative functions that are not exclusive to mitochondrial biogenesis. The results point to a central role for the PGC-1 family in integrating mitochondrial biogenesis and energy production with many diverse cellular functions. This article is part of a Special Issue entitled: Mitochondria and Cardioprotection

Carrier Concentration Dependencies of Magnetization & Transport in Ga1-xMnxAs1-yTey

We have investigated the transport and magnetization characteristics of Ga1-xMnxAs intentionally compensated with shallow Te donors. Using ion implantation followed by pulsed-laser melting, we vary the Te compensation and drive the system through a metal-insulator transition (MIT). This MIT is associated with enhanced low-temperature magnetization and an evolution from concave to convex temperature-dependent magnetization.Comment: 2 pages, 2 figures. To appear in the proceedings of the 27th International Conference on the Physics of Semiconductors (ICPS-27, Flagstaff, AZ, July 26-30, 2004

Four submarginal cells on a forewing of \u3ci\u3eMelitoma taurea\u3c/i\u3e (Say) (Hymenoptera: Apidae), and a summary of known records of atypical and variable numbers of submarginal cells

A specimen of Melitoma taurea (Say) (Hymenoptera: Apidae) was captured on Hart-Miller Island, Chesapeake Bay, Baltimore County, Maryland. The specimen possessed the typical three submarginal cells on the right forewing but exhibited four submarginal cells on the left forewing due to the presence of an additional submarginal crossvein dividing the second submarginal cell. The presence of four submarginal cells is a rare occurrence in bees. Besides documenting this occurrence, this paper presents a summary of known published and previously unpublished records of atypical and variable numbers of submarginal cells. Published records were found for 66 species: Colletidae (1), Andrenidae (28), Halictidae (19), and Apidae (18). In four instances, published records were also found at the genus or subgenus level. Previously unpublished records are reported for 29 species: Colletidae (1), Andrenidae (5), Halictidae (13), and Apidae (10). Previously unpublished records are also shown for six specimens that are only identified to genus or subgenus. Twelve-and-one-third percent of the specimens with atypical numbers of submarginal cells would normally have had two submarginal cells; 87.7% would normally have had three submarginal cells. Approximately, 49.4% of the specimens had atypical numbers on one wing, and approximately 50.6% had atypical numbers on both wings. Of the normally two submarginal cell specimens, 80.0% gained and 20.0% lost one submarginal crossvein. Of the normally three submarginal cell specimens, 1.4% gained one submarginal crossvein and 98.6% lost one or more submarginal crossveins

Hydrogen patterning of Ga1-xMnxAs for planar spintronics

We demonstrate two patterning techniques based on hydrogen passivation of Ga1-xMnxAs to produce isolated ferromagnetically active regions embedded uniformly in a paramagnetic, insulating host. The first method consists of selective hydrogenation of Ga1-xMnxAs by lithographic masking. Magnetotransport measurements of Hall-bars made in this manner display the characteristic properties of the hole-mediated ferromagnetic phase, which result from good pattern isolation. Arrays of Ga1-xMnxAs dots as small as 250 nm across have been realized by this process. The second process consists of blanket hydrogenation of Ga1-xMnxAs followed by local reactivation using confined low-power pulsed-laser annealing. Conductance imaging reveals local electrical reactivation of micrometer-sized regions that accompanies the restoration of ferromagnetism. The spatial resolution achievable with this method can potentially reach <100 nm by employing near-field laser processing. The high spatial resolution attainable by hydrogenation patterning enables the development of systems with novel functionalities such as lateral spin-injection as well as the exploration of magnetization dynamics in individual and coupled structures made from this novel class of semiconductors.Comment: ICDS-24, July 2007. 8 pages with 4 figure

Electronic structure of ferromagnetic semiconductor Ga1-xMnxAs probed by sub-gap magneto-optical spectroscopyElectronic

We employ Faraday and Kerr effect spectroscopy in the infrared range to investigate the electronicstructure ofGa1 xMnxAsnear the Fermi energy. The band structure of this archetypical dilute-momentferromagnetic semiconductor has been a matter of controversy, fueled partly by previous measurements ofthe unpolarized infrared absorption and their phenomenological impurity-band interpretation. Unlike theunpolarized absorption, the infrared magneto-optical effects we study are intimately related to ferromag-netism, and their interpretation is much more microscopically constrained in terms of the orbital characterof the relevant band states. We show that the conventional theory of the disordered valence band with anantiferromatnetic exchange term accounts semiquantitatively for the overall characteristics of themeasured infrared magneto-optical spectra

Temperature dependent conductivity of polycrystalline Cu 2ZnSnS 4 thin films

pre-printThe temperature-dependent conductivity of Cu2ZnSnS4 (CZTS) thin films prepared by sulfurization of different sputtered ZnS/Cu/Sn stacks and also of the same stack annealed for different times was investigated from 30-300 K. Fitting of the through-thickness conductivity requires a model including Mott variable-range hopping (M-VRH), nearest-neighbor hopping (NNH), and thermionic emission over grain boundary (GB) barriers. The GB barrier height varies sensitively from 50-150 (65) meV with annealing and especially with [Cu]/([Zn]þ[Sn]) ratio but is independent of [Zn]/[Sn] ratio. These results are critical for understanding the behavior of solar cells based on polycrystalline CZTS absorber layers

SnS thin-films by RF sputtering at room temperature

Journal ArticleTin monosulfide (SnS) is of interest as a potential solar cell absorber material. We present a preliminary investigation of the effects of sputtering conditions on SnS thin-film structural, optical, and electronic properties. Films were RF sputtered from an SnS target using an argon plasma. Resistivity, stoichiometry, phase, grain size and shape, bandgap, and optical absorption coefficient can be varied by modifying argon pressure for a fixed deposition time. Most films have an indirect bandgap in the range of 1.08?1.18 eV. XRD patterns confirmed the films as mostly crystalline, and grain morphology was examined using profile and surface SEM images