32,057 research outputs found
Comment on "Improving the seasonal cycle and interannual variations of biomass burning aerosol sources" by Generoso et al.
International audienceGeneroso et al. (2003) suggest a method for improving current inventories of aerosol emission from biomass burning based on the Along Track Scanning Radiometer (ATSR) nighttime hot spot product. In order to show the validity and representative of the nighttime burning product for such applications, Genoroso et al. (2003) compared the ATSR nighttime products to the daily fire products from TRMM, AVHRR etc. in nine selected regions. Their analyses demonstrate that in most cases, the nighttime products show a seasonal cycle that is consistent with the daily observations. However, they noticed significant discrepancies in biomass seasonality between ATSR nighttime product and TRMM daily product in Sahel region. In a commentary paper, Giglio and Kendall (2003) clarify that the origin of TRMM fire data used in Generoso et al. (2003) is from TRMM Science Data and Information System (Ji and Stocker, 2002). We thank Giglio and Kendall for such clarifications that provide an opportunity for us to clarify several issues on the applications of TSDIS fire data
Cell death regulation in Drosophila: Conservation of mechanism and unique insights
Programmed cell death, or apoptosis, is a genetically encoded form of cell suicide that results in the orderly death and phagocytic removal of excess, damaged, or dangerous cells during normal development and in the adult. The cellular machinery required to carry out apoptosis is present in most, if not all cells, but is only activated in cells instructed to die (for review see Jacobson et al. 1997). Here, we review cell death regulation in the fly in the context of a first pass look at the complete Drosophila genome and what is known about death regulation in other organisms, particularly worms and vertebrates
Culture, change and prediction
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91927/1/culture_change_prediction.pd
Joint modeling of ChIP-seq data via a Markov random field model
Chromatin ImmunoPrecipitation-sequencing (ChIP-seq) experiments have now become routine in biology for the detection of protein-binding sites. In this paper, we present a Markov random field model for the joint analysis of multiple ChIP-seq experiments. The proposed model naturally accounts for spatial dependencies in the data, by assuming first-order Markov dependence and, for the large proportion of zero counts, by using zero-inflated mixture distributions. In contrast to all other available implementations, the model allows for the joint modeling of multiple experiments, by incorporating key aspects of the experimental design. In particular, the model uses the information about replicates and about the different antibodies used in the experiments. An extensive simulation study shows a lower false non-discovery rate for the proposed method, compared with existing methods, at the same false discovery rate. Finally, we present an analysis on real data for the detection of histone modifications of two chromatin modifiers from eight ChIP-seq experiments, including technical replicates with different IP efficiencies
Investigation of the energy dependence of the orbital light curve in LS 5039
LS 5039 is so far the best studied -ray binary system at
multi-wavelength energies. A time resolved study of its spectral energy
distribution (SED) shows that above 1 keV its power output is changing along
its binary orbit as well as being a function of energy. To disentangle the
energy dependence of the power output as a function of orbital phase, we
investigated in detail the orbital light curves as derived with different
telescopes at different energy bands. We analysed the data from all existing
\textit{INTEGRAL}/IBIS/ISGRI observations of the source and generated the most
up-to-date orbital light curves at hard X-ray energies. In the -ray
band, we carried out orbital phase-resolved analysis of \textit{Fermi}-LAT data
between 30 MeV and 10 GeV in 5 different energy bands. We found that, at
100 MeV and 1 TeV the peak of the -ray emission is
near orbital phase 0.7, while between 100 MeV and 1 GeV it moves
close to orbital phase 1.0 in an orbital anti-clockwise manner. This result
suggests that the transition region in the SED at soft -rays (below a
hundred MeV) is related to the orbital phase interval of 0.5--1.0 but not to
the one of 0.0--0.5, when the compact object is "behind" its companion. Another
interesting result is that between 3 and 20 GeV no orbital modulation is found,
although \textit{Fermi}-LAT significantly (18) detects LS 5039.
This is consistent with the fact that at these energies, the contributions to
the overall emission from the inferior conjunction phase region (INFC, orbital
phase 0.45 to 0.9) and from the superior conjunction phase region (SUPC,
orbital phase 0.9 to 0.45) are equal in strength. At TeV energies the power
output is again dominant in the INFC region and the flux peak occurs at phase
0.7.Comment: 7 pages, 6 figures, accepted for publication in MNRA
Topological Properties of Spatial Coherence Function
Topology of the spatial coherence function is considered in details. The
phase singularity (coherence vortices) structures of coherence function are
classified by Hopf index and Brouwer degree in topology. The coherence flux
quantization and the linking of the closed coherence vortices are also studied
from the topological properties of the spatial coherence function.Comment: 9 page
An Electronic Mach-Zehnder Interferometer
Double-slit electron interferometers, fabricated in high mobility
two-dimensional electron gas (2DEG), proved to be very powerful tools in
studying coherent wave-like phenomena in mesoscopic systems. However, they
suffer from small fringe visibility due to the many channels in each slit and
poor sensitivity to small currents due to their open geometry. Moreover, the
interferometers do not function in a high magnetic field, namely, in the
quantum Hall effect (QHE) regime, since it destroys the symmetry between left
and right slits. Here, we report on the fabrication and operation of a novel,
single channel, two-path electron interferometer that functions in a high
magnetic field. It is the first electronic analog of the well-known optical
Mach-Zehnder (MZ) interferometer. Based on single edge state and closed
geometry transport in the QHE regime the interferometer is highly sensitive and
exhibits very high visibility (62%). However, the interference pattern decays
precipitously with increasing electron temperature or energy. While we do not
understand the reason for the dephasing we show, via shot noise measurement,
that it is not a decoherence process that results from inelastic scattering
events.Comment: to appear in Natur
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