544 research outputs found
A 7 Day Multiwavelength Flare Campaign on AU Mic. I. High-time-resolution Light Curves and the Thermal Empirical Neupert Effect
No full textWe present light curves and flares from a 7 day, multiwavelength observational campaign of AU Mic, a young and active dM1e star with exoplanets and a debris disk. We report on 73 unique flares between the X-ray to optical data. We use high-time-resolution near-UV (NUV) photometry and soft X-ray (SXR) data from the X-ray Multi-Mirror Mission to study the empirical Neupert effect, which correlates the gradual and impulsive phase flaring emissions. We find that 65% (30 of 46) flares do not follow the Neupert effect, which is 3 times more excursions than seen in solar flares, and propose a four-part Neupert effect classification (Neupert, quasi-Neupert, non-Neupert types I and II) to explain the multiwavelength responses. While the SXR emission generally lags behind the NUV as expected from the chromospheric evaporation flare models, the Neupert effect is more prevalent in larger, more impulsive flares. Preliminary flaring rate analysis with X-ray and U-band data suggests that previously estimated energy ratios hold for a collection of flares observed over the same time period, but not necessarily for an individual, multiwavelength flare. These results imply that one model cannot explain all stellar flares and care should be taken when extrapolating between wavelength regimes. Future work will expand wavelength coverage using radio data to constrain the nonthermal empirical and theoretical Neupert effects to better refine models and bridge the gap between stellar and solar flare physics
Scene af Brand
No full textThis is an original manuscript dedicated to the owner of this collection.https://scholarexchange.furman.edu/periphery-neupert/1001/thumbnail.jp
Timor-Leste human development report 2011 : managing natural resources for human development : developing the non-oil economy to achieve the MDGs
No full textPrincipal Author John G Taylor, Coordinator Rui Gomes, Authors, Technical Background Papers Tobias N. Rasmussen, Andrew Rosser, Martin Sandbu, Michael Ross, Tibor van Staveren, Ricardo F. Neupert, Rui A. Gomes, John G Taylor, Sonny Harmadi, Hafiz Pash
Characterization of Translocation Contact Sites Involved in the Import of Mitochondrial Proteins
No full textImport of proteins into the mitochondrial matrix requires translocation across two membranes. Translocational intermediates of mitochondrial proteins, which span the outer and inner membrane simultaneously and thus suggest that translocation occurs in one step, have recently been described (Schleyer, M., and W. Neupert, 1985, Cell, 43:339-350). In this study we present evidence that distinct membrane areas are involved in the translocation process. Mitochondria that had lost most of their outer membrane by digitonin treatment (mitoplasts) still had the ability to import proteins. Import depended on proteinaceous structures of the residual outer membrane and on a factor that is located between the outer and inner membranes and that could be extracted with detergent plus salt. Translocational intermediates, which had been preformed before fractionation, remained with the mitoplasts under conditions where most of the outer membrane was subsequently removed. Submitochondrial vesicles were isolated in which translocational intermediates were enriched. Immunocytochemical studies also suggested that the translocational intermediates are located in areas where outer and inner membranes are in close proximity. We conclude that the membrane-potential-dependent import of precursor proteins involves translocation contact sites where the two membranes are closely apposed and are linked in a stable manner
Partial sequence of a chloroform-methanol soluble polypeptide from Neurospora mitochondrial membranes
No full textProtein translocation across mitochondrial membranes
No full textProtein translocation across biological membranes is of fundamental importance for the biogenesis of organelles and in protein secretion. We will give an overview of the recent achievements in the understanding of protein translocation across mitochondrial membranes(1-5). In particular we will focus on recently identified components of the mitochondrial import apparatus
- …
