39,265 research outputs found
Measurement of Electron Content at the Magnetic Equator
Ionospheric electron content measurements at magnetic equator obtained by Faraday rotation data analysis from radio beacon satellit
Dietary Uncoupling of Gut Microbiota and Energy Harvesting from Obesity and Glucose Tolerance in Mice
The authors gratefully acknowledge Doctoral Training Partnership funding from the BBSRC (M.J.D.) and funding from the Scottish Government (P.J.M., A.W.R., and A.W.W.). We also thank the Centre for Genome-Enabled Biology and Medicine for help with next-generation sequencing and Karen Garden and the Rowettâs Analytical Services for SCFA analysis. SUPPLEMENTAL INFORMATION Supplemental Information includes four figures and two tables and can be found with this article online at https://doi.org/10.1016/j.celrep.2017.10.056.Peer reviewedPublisher PD
The time-of-flight system on the Goddard medium energy gamma-ray telescope
A scintillation counter time of flight system, incorporated into the Goddard 50 cm by 50 cm spark chamber gamma ray telescope is described. The system, which utilizes constant fractions timing and particle position compensation and digitizes up to 10 ns time differences to six bit accuracy in less than 500 ns is analyzed. The performance of this system during balloon flight is discussed
The selection, appraisal and retention of digital scientific data: dighlights of an ERPANET/CODATA workshop
CODATA and ERPANET collaborated to convene an international archiving workshop on the selection, appraisal, and retention of digital scientific data, which was held on 15-17 December 2003 at the Biblioteca Nacional in Lisbon, Portugal. The workshop brought together more than 65 researchers, data and information managers, archivists, and librarians from 13 countries to discuss the issues involved in making critical decisions regarding the long-term preservation of the scientific record. One of the major aims for this workshop was to provide an international forum to exchange information about data archiving policies and practices across different scientific, institutional, and national contexts. Highlights from the workshop discussions are presented
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Embryonic POU5F1 is Required for Expanded Bovine Blastocyst Formation.
POU5F1 is a transcription factor and master regulator of cell pluripotency with indispensable roles in early embryo development and cell lineage specification. The role of embryonic POU5F1 in blastocyst formation and cell lineage specification differs between mammalian species but remains completely unknown in cattle. The CRISPR/Cas9 system was utilized for targeted disruption of the POU5F1 gene by direct injection into zygotes. Disruption of the bovine POU5F1 locus prevented blastocyst formation and was associated with embryonic arrest at the morula stage. POU5F1 knockout morulas developed at a similar rate as control embryos and presented a similar number of blastomeres by day 5 of development. Initiation of SOX2 expression by day 5 of development was not affected by lack of POU5F1. On the other hand, CDX2 expression was aberrant in embryos lacking POU5F1. Notably, the phenotype observed in bovine POU5F1 knockout embryos reveals conserved functions associated with loss of human embryonic POU5F1 that differ from Pou5f1- null mice. The similarity observed in transcriptional regulation of early embryo development between cattle and humans combined with highly efficient gene editing techniques make the bovine a valuable model for human embryo biology with expanded applications in agriculture and assisted reproductive technologies
Design of a Multi-Moon Orbiter
The Multi-Moon Orbiter concept is introduced, wherein a single spacecraft orbits
several moons of Jupiter, allowing long duration observations. The ÎV requirements
for this mission can be low if ballistic captures and resonant gravity assists by Jupiterâs
moons are used. For example, using only 22 m/s, a spacecraft initially injected in a
jovian orbit can be directed into a capture orbit around Europa, orbiting both Callisto
and Ganymede enroute. The time of flight for this preliminary trajectory is four years,
but may be reduced by striking a compromise between fuel and time optimization during
the inter-moon transfer phases
Application of dynamical systems theory to a very low energy transfer
We use lobe dynamics in the restricted three-body problem to design orbits with
prescribed itineraries with respect to the resonance regions within a Hillâs region. The
application we envision is the design of a low energy trajectory to orbit three of Jupiterâs
moons using the patched three-body approximation (P3BA). We introduce the âswitching
region,â the P3BA analogue to the âsphere of influence.â Numerical results are given
for the problem of finding the fastest trajectory from an initial region of phase space
(escape orbits from moon A) to a target region (orbits captured by moon B) using small
controls
Invariant Manifolds, the Spatial Three-Body Problem and Space Mission Design
The invariant manifold structures of the collinear libration points for the
spatial restricted three-body problem provide the framework for understanding
complex dynamical phenomena from a geometric point of view.
In particular, the stable and unstable invariant manifold \tubes" associated
to libration point orbits are the phase space structures that provide a
conduit for orbits between primary bodies for separate three-body systems.
These invariant manifold tubes can be used to construct new spacecraft
trajectories, such as a \Petit Grand Tour" of the moons of Jupiter. Previous
work focused on the planar circular restricted three-body problem.
The current work extends the results to the spatial case
Anisotropic focusing characteristics of micro-domain structures within crystalline Sr<sub>0.61</sub>Ba<sub>0.39</sub>Nb<sub>2</sub>O<sub>6</sub> : the crystal ball
We report the anisotropic focusing characteristics of a spherically configured region of micro-domains that have been induced within a cubic shaped crystal of Ce:doped Sr0.61Ba0.39Nb2O6. The internal spherical structure focuses extraordinary polarised light, but not ordinary polarised. The spherical region, which is easily observed via scattering, is formed as the crystal cools down, after a repoling cycle through the Curie temperature, with an applied field. Analytic modelling of the thermal gradients that exist within the crystal during cooling reveals a small (< 1°) temperature difference between the central and outside regions. The similarity in shape between these temperature profiles and the observed scattering region suggests a possible mechanism for the growth of this spherical micro-domained structure
A continuum model for the dynamics of the phase transition from slow-wave sleep to REM sleep
Previous studies have shown that activated cortical states (awake and rapid eye-movement (REM) sleep), are associated with increased cholinergic input into the cerebral cortex. However, the mechanisms that underlie the detailed dynamics of the cortical transition from slow-wave to REM sleep have not been quantitatively modeled. How does the sequence of abrupt changes in the cortical dynamics (as detected in the electrocorticogram) result from the more gradual change in subcortical cholinergic input? We compare the output from a continuum model of cortical neuronal dynamics with experimentally-derived rat electrocorticogram data. The output from the computer model was consistent with experimental observations. In slow-wave sleep, 0.5â2-Hz oscillations arise from the cortex jumping between âupâ and âdownâ states on the stationary-state manifold. As cholinergic input increases, the upper state undergoes a bifurcation to an 8-Hz oscillation. The coexistence of both oscillations is similar to that found in the intermediate stage of sleep of the rat. Further cholinergic input moves the trajectory to a point where the lower part of the manifold in not available, and thus the slow oscillation abruptly ceases (REM sleep). The model provides a natural basis to explain neuromodulator-induced changes in cortical activity, and indicates that a cortical phase change, rather than a brainstem âflip-flopâ, may describe the transition from slow-wave sleep to REM
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