561 research outputs found
The phylogenetically distinct early human embryo
The phylogenetic singularity of the human embryo remains unresolved as cell types of the human blastocyst have resisted classification. Combining clustering of single cellular transcriptomes and dynamically expressed genes we resolve the cell types. This unveils the missing inner cell mass (ICM) and reveals classical step-wise development. Conversely, numerous features render our blastocyst phylogenetically distinct: unlike mice, our epiblast is self-renewing and we have blastocyst non-committed cells (NCCs), part of an apoptosis-mediated quality control/purging process. At the transcriptome-level all primate embryos are distinct as the pluripotent cell types are uniquely fast evolving. A substantial fraction of gene expression gain and loss events between human and new-world monkeys involve endogenous retrovirus H (ERVH). Human pluripotent cells are unique in which (H)ERVH's are active, the extent to which these modulate neighbour gene expression and their ability to suppress mutagenic transposable elements. Current naive cultures are heterogeneous and both developmentally and phylogenetically "confused"
Simulations of Supernova Remnants in Diffuse Media III. The Population of Buoyant Remnants Above the Milky Way's Disk
We model SNRs at a variety of heights above the disk. Our detailed numerical
simulations include non-equilibrium ionization and recombination and follow the
remnants' evolution until their hot bubbles have cooled. We analytically
calculate the bubbles' buoyant acceleration. From the results, we estimate the
time and space average O VI, N V, and C IV column densities and emission
intensities, 1/4 keV soft X-ray surface brightness, area coverage, and volume
occupation of the population of isolated SNRs above the Galaxy's HI layer.
Irrespective of assumed supernova explosion energy, ambient nonthermal
pressure, or frictional drag coefficient, the predicted O VI column density
matches the observed distribution between 130 pc and 2000 pc. The SNRs' O VI
intensity is a significant fraction of the average observed intensity. Within
the range of uncertainty in the SN rate, such SNRs can explain all of the
observed 1/4 keV surface brightness attributed to the extraplanar gas beyond
the H I layer in the southern hemisphere (~400 x 10^-6 counts/s/arcmin^2).
Thus, extraplanar SNRs could be the most important source of hot gas between
the Local Bubble and z ~ 2000 pc in the relatively quiescent southern
hemisphere. These results stand whether the remnants are assumed to be buoyant
or not. The population of old extraplanar SNRs should cover most of the high
latitude sky, but bright young extraplanar SNRs should cover less than 1% of
the sky. Perhaps the l=247, b=-64 crescent in the 1/4 keV X-ray maps could be a
young remnant.Comment: Accepted by ApJ for publication on February 10, 2006 (Volume 638). 44
pages, including 6 figures, 10 tables (and 1 blank page
Equilibrium shapes and energies of coherent strained InP islands
The equilibrium shapes and energies of coherent strained InP islands grown on
GaP have been investigated with a hybrid approach that has been previously
applied to InAs islands on GaAs. This combines calculations of the surface
energies by density functional theory and the bulk deformation energies by
continuum elasticity theory. The calculated equilibrium shapes for different
chemical environments exhibit the {101}, {111}, {\=1\=1\=1} facets and a (001)
top surface. They compare quite well with recent atomic-force microscopy data.
Thus in the InP/GaInP-system a considerable equilibration of the individual
islands with respect to their shapes can be achieved. We discuss the
implications of our results for the Ostwald ripening of the coherent InP
islands. In addition we compare strain fields in uncapped and capped islands.Comment: 10 pages including 6 figures. Submitted to Phys. Rev. B. Related
publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm
A reporting and analysis framework for structured evaluation of COVID-19 clinical and imaging data
The COVID-19 pandemic has worldwide individual and socioeconomic consequences. Chest computed tomography has been found to support diagnostics and disease monitoring. A standardized approach to generate, collect, analyze, and share clinical and imaging information in the highest quality possible is urgently needed. We developed systematic, computer-assisted and context-guided electronic data capture on the FDA-approved mint LesionTM software platform to enable cloud-based data collection and real-time analysis. The acquisition and annotation include radiological findings and radiomics performed directly on primary imaging data together with information from the patient history and clinical data. As proof of concept, anonymized data of 283 patients with either suspected or confirmed SARS-CoV-2 infection from eight European medical centers were aggregated in data analysis dashboards. Aggregated data were compared to key findings of landmark research literature. This concept has been chosen for use in the national COVID-19 response of the radiological departments of all university hospitals in Germany
Search for a dark vector gauge boson decaying to using decays
We report a search for a dark vector gauge boson that couples to
quarks in the decay chain , . No signal is found and we set a
mass-dependent limit on the baryonic fine structure constant of in the mass range of 290 to 520 MeV/. This analysis is
based on a data sample of 976 fb collected by the Belle experiment at
the KEKB asymmetric-energy collider.Comment: 6 pages, 4 figure
Invariant-mass and fractional-energy dependence of inclusive production of di-hadrons in annihilation at 10.58 GeV
The inclusive cross sections for di-hadrons of charged pions and kaons
() in electron-positron annihilation are reported. They
are obtained as a function of the total fractional energy and invariant mass
for any di-hadron combination in the same hemisphere as defined by the thrust
event-shape variable and its axis. Since same-hemisphere di-hadrons can be
assumed to originate predominantly from the same initial parton, di-hadron
fragmentation functions are probed. These di-hadron fragmentation functions are
needed as an unpolarized baseline in order to quantitatively understand related
spin-dependent measurements in other processes and to apply them to the
extraction of quark transversity distribution functions in the nucleon. The
di-hadron cross sections are obtained from a data sample
collected at or near the resonance with the Belle detector at
the KEKB asymmetric-energy collider.Comment: 21 pages, 18 figures plus 25 figures in supplemental material,
submitted to PR
Observation of and search for violation in radiative charm decays
We report the first observation of the radiative charm decay and the first search for violation in decays , , and , using a data sample of
943 fb collected with the Belle detector at the KEKB asymmetric-energy
collider. The branching fraction is measured to be , where the first
uncertainty is statistical and the second is systematic. The obtained
asymmetries, , , and
, are consistent with no violation. We also present an improved
measurement of the branching fractions and
Study of Excited States Decaying into and Baryons
Using a data sample of 980 of annihilation data
taken with the Belle detector operating at the KEKB asymmetric-energy
collider, we report the results of a study of excited states that
decay, via the emission of photons and/or charged pions, into or
ground state charmed-strange baryons. We present new measurements of
the masses of all members of the , ,
, , and isodoublets, measurements of
the intrinsic widths of those that decay strongly, and evidence of previously
unknown transitions.Comment: Submitted to PR
Search for and branching fraction measurement of
We have searched for the Cabibbo-suppressed decay
in collisions using a data sample corresponding to an integrated
luminosity of 915 . The data were collected by the Belle
experiment at the KEKB asymmetric-energy collider running at or near
the and resonances. No significant signal is
observed, and we set an upper limit on the branching fraction of
at 90% confidence
level. The contribution for nonresonant decays
is found to be consistent with zero and the corresponding upper limit on its
branching fraction is set to be at 90% confidence level. We also measure the branching
fraction for the Cabibbo-favored decay ; the
result is , which is
the most precise measurement to date. Finally, we have searched for an
intermediate hidden-strangeness pentaquark decay . We see no
evidence for this intermediate decay and set an upper limit on the product
branching fraction of at 90% confidence level.Comment: 8 pages, 5 figures, 1 table, minor text change in version
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