693 research outputs found
Investigating the effect of target of rapamycin kinase inhibition on the Chlamydomonas reinhardtii phosphoproteome: from known homologs to new targets
Recuperado de: https://www.biorxiv.org/content/10.1101/310102v1Target of rapamycin (TOR) kinase is a conserved regulator of cell growth whose activity is modulated in response to nutrients, energy and stress. Key proteins involved in the pathway are conserved in the model photosynthetic microalga Chlamydomonas reinhardtii, but the substrates of TOR kinase and downstream signaling network have not been elucidated. Our study provides a new resource for investigating the phosphorylation networks governed by the TOR kinase pathway in Chlamydomonas. We used quantitative phosphoproteomics to investigate the effects of inhibiting Chlamydomonas TOR kinase on dynamic protein phosphorylation. Wild-type and AZD-insensitive Chlamydomonas strains were treated with TOR-specific chemical inhibitors (rapamycin, AZD8055 and Torin1), after which differentially affected phosphosites were identified. Our quantitative phosphoproteomic dataset comprised 2547 unique phosphosites from 1432 different proteins. Inhibition of TOR kinase caused significant quantitative changes in phosphorylation at 258 phosphosites, from 219 unique phosphopeptides. Our results include Chlamydomonas homologs of TOR signaling-related proteins, including a site on RPS6 with a decrease in phosphorylation. Additionally, phosphosites on proteins involved in translation and carotenoid biosynthesis were identified. Follow-up experiments guided by these phosphoproteomic findings in lycopene beta/epsilon cyclase showed that carotenoid levels are affected by TORC1 inhibition and carotenoid production is under TOR control in algae.National Science Foundation CAREER MCB-155252
Ramanujan sums for signal processing of low frequency noise
An aperiodic (low frequency) spectrum may originate from the error term in
the mean value of an arithmetical function such as M\"obius function or
Mangoldt function, which are coding sequences for prime numbers. In the
discrete Fourier transform the analyzing wave is periodic and not well suited
to represent the low frequency regime. In place we introduce a new signal
processing tool based on the Ramanujan sums c_q(n), well adapted to the
analysis of arithmetical sequences with many resonances p/q. The sums are
quasi-periodic versus the time n of the resonance and aperiodic versus the
order q of the resonance. New results arise from the use of this
Ramanujan-Fourier transform (RFT) in the context of arithmetical and
experimental signalsComment: 11 pages in IOP style, 14 figures, 2 tables, 16 reference
Efficiency and regulation tests of general electric transformer, type H, #497204
Citation: Forsberg, Carl F., Perrine, Arthur A., and McLean, Harry G. Efficiency and regulation tests of general electric transformer, type H, #497204. Senior thesis, Kansas State Agricultural College, 1908.Introduction: The static transformer is a device used for changing the voltage and current relations of an alternating current. It consists, essentially, of a pair of mutually inductive circuits called the primary and secondary coils, and a magnetic circuit interlinked with both coils. This magnetic circuit is called the core of the transforme
A multiwavelength study of the remnant of nova GK Persei
We present new observations of the nebular remnant of the old nova GK Persei
1901, in the optical using the 2m HCT and at low radio frequencies using the
GMRT. The evolution of the nova remnant indicates shock interaction with the
ambient medium, especially in the southwest quadrant. Application of a simple
model for the shock and its evolution to determine the time dependence of the
radius of the shell in the southwest quadrant indicates that the shell is now
expanding into an ambient medium that has a lower density compared to the
density of the ambient medium ahead of the shock in 1987.There are indications
of a recent interaction of the nova remnant with the ambient medium in the
northeast quadrant also. The nova remnant of GK Per is detected at all the
observed radio frequencies and is of similar extent as the optical remnant.
Putting together our radio observations with VLA archival data on GK Per from
1997, we obtain three interesting results: 1. The spectrum above 1.4 GHz
follows a power law with an index -0.7 and below 1.4 GHz follows a power law
with an index ~ -0.85. This could be due to the presence of at least two
populations of electrons dominating the global emission at different
frequencies. 2. We record an annual secular decrease of 2.1% in the flux
density of the nova remnant at 1.4 and 4.9 GHz between 1984 and 1997 which has
left the spectral index unchanged at -0.7. No such decrease is observed in the
flux densities below 1 GHz. 3. We record an increase in the flux density at
0.33 GHz compared to the previous estimate in 1987. We conclude that the
remnant of nova GK Per is similar to supernova remnants and in particular, to
the young supernova remnant Cas A.Comment: 10 pages; uses A&A style; figures 1, 2 & 6 are in JPEG format.
Accepted for publication in Astronomy & Astrophysics. Full paper including
Figures 1, 2 & 6 may be downloaded from
http://www.iiap.res.in/personnel/gca/gca.htm
Electronic and optical properties of electromigrated molecular junctions
Electromigrated nanoscale junctions have proven very useful for studying
electronic transport at the single-molecule scale. However, confirming that
conduction is through precisely the molecule of interest and not some
contaminant or metal nanoparticle has remained a persistent challenge,
typically requiring a statistical analysis of many devices. We review how
transport mechanisms in both purely electronic and optical measurements can be
used to infer information about the nanoscale junction configuration. The
electronic response to optical excitation is particularly revealing. We briefly
discuss surface-enhanced Raman spectroscopy on such junctions, and present new
results showing that currents due to optical rectification can provide a means
of estimating the local electric field at the junction due to illumination.Comment: 19 pages, 8 figures, invited paper for forthcoming special issue of
Journal of Physics: Condensed Matter. For other related papers, see
http://www.ruf.rice.edu/~natelson/publications.htm
Probing the X-Ray Binary Populations of the Ring Galaxy NGC 1291
We present Chandra studies of the X-ray binary (XRB) populations in the bulge
and ring regions of the ring galaxy NGC 1291. We detect 169 X-ray point sources
in the galaxy, 75 in the bulge and 71 in the ring, utilizing the four available
Chandra observations totaling an effective exposure of 179 ks. We report
photometric properties of these sources in a point-source catalog. There are
~40% of the bulge sources and ~25% of the ring sources showing >3\sigma
long-term variability in their X-ray count rate. The X-ray colors suggest that
a significant fraction of the bulge (~75%) and ring (~65%) sources are likely
low-mass X-ray binaries (LMXBs). The spectra of the nuclear source indicate
that it is a low-luminosity AGN with moderate obscuration; spectral variability
is observed between individual observations. We construct 0.3-8.0 keV X-ray
luminosity functions (XLFs) for the bulge and ring XRB populations, taking into
account the detection incompleteness and background AGN contamination. We reach
90% completeness limits of ~1.5\times10^{37} and ~2.2\times10^{37} erg/s for
the bulge and ring populations, respectively. Both XLFs can be fit with a
broken power-law model, and the shapes are consistent with those expected for
populations dominated by LMXBs. We perform detailed population synthesis
modeling of the XRB populations in NGC 1291, which suggests that the observed
combined XLF is dominated by an old LMXB population. We compare the bulge and
ring XRB populations, and argue that the ring XRBs are associated with a
younger stellar population than the bulge sources, based on the relative
overdensity of X-ray sources in the ring, the generally harder X-ray color of
the ring sources, the overabundance of luminous sources in the combined XLF,
and the flatter shape of the ring XLF.Comment: 15 pages, 11 figures. Accepted for publication in Ap
Evidence for tidal interaction and a supergiant HI shell in the Local Group dwarf galaxy NGC 6822
We present a wide-field, high spatial and velocity resolution map of the
entire extended HI distribution of the Local Group dwarf galaxy NGC 6822. The
observations were obtained with the Australia Telescope Compact Array in
mosaicing mode. The interstellar medium of NGC 6822 is shaped by the presence
of numerous H{\sc i} holes and shells, including a supergiant shell, and the
effects of tidal interaction, in the form of a tidal arm and an infalling or
interacting HI complex. The HI shell is situated outside the optical galaxy and
occupies roughly a quarter of the area of the main HI disk. It measures 2.0
times 1.4 kpc, making it one of the largest supergiant HI shells ever found.
The giant hole shows no signs of expansion and no obvious creation mechanism is
evident from our data. If star formation was the cause, an energy equivalent of
\~100 supernovae (10^53 erg) is needed to create the hole. We derive an upper
limit for the age of order 100 Myr. The presence of a possible tidal arm
indicates that NGC 6822 may recently have undergone some interaction. An HI
complex located in the north-west of the galaxy may be the interaction partner.
We argue that it is likely that these features were created about 100 Myr ago
in an event that also enhanced the star formation rateComment: Accepted for publication in Astrophysical Journal Letters (needs
emulateapj5.sty, included
Development of the ECOSAR P-Band Synthetic Aperture Radar
This paper describes objectives and recent progress on the development of the EcoSAR, a new P-band airborne radar instrument being developed at the NASA/ Goddard Space Flight Center (GSFC) for the polarimetric and interferometric measurements of ecosystem structure and biomass. These measurements support science requirements for the study of the carbon cycle and its relationship to climate change. The instrument is scheduled to be completed and flight tested in 2013. Index Terms SAR, Digital Beamforming, Interferometry
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