854 research outputs found
Nurse Expertise: A Critical Resource in the COVID-19 Pandemic Response
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Characteristics of transposable element exonization within human and mouse
Insertion of transposed elements within mammalian genes is thought to be an
important contributor to mammalian evolution and speciation. Insertion of
transposed elements into introns can lead to their activation as alternatively
spliced cassette exons, an event called exonization. Elucidation of the
evolutionary constraints that have shaped fixation of transposed elements
within human and mouse protein coding genes and subsequent exonization is
important for understanding of how the exonization process has affected
transcriptome and proteome complexities. Here we show that exonization of
transposed elements is biased towards the beginning of the coding sequence in
both human and mouse genes. Analysis of single nucleotide polymorphisms (SNPs)
revealed that exonization of transposed elements can be population-specific,
implying that exonizations may enhance divergence and lead to speciation. SNP
density analysis revealed differences between Alu and other transposed
elements. Finally, we identified cases of primate-specific Alu elements that
depend on RNA editing for their exonization. These results shed light on TE
fixation and the exonization process within human and mouse genes.Comment: 11 pages, 4 figure
Sociological and Communication-Theoretical Perspectives on the Commercialization of the Sciences
Both self-organization and organization are important for the further
development of the sciences: the two dynamics condition and enable each other.
Commercial and public considerations can interact and "interpenetrate" in
historical organization; different codes of communication are then
"recombined." However, self-organization in the symbolically generalized codes
of communication can be expected to operate at the global level. The Triple
Helix model allows for both a neo-institutional appreciation in terms of
historical networks of university-industry-government relations and a
neo-evolutionary interpretation in terms of three functions: (i) novelty
production, (i) wealth generation, and (iii) political control. Using this
model, one can appreciate both subdynamics. The mutual information in three
dimensions enables us to measure the trade-off between organization and
self-organization as a possible synergy. The question of optimization between
commercial and public interests in the different sciences can thus be made
empirical.Comment: Science & Education (forthcoming
Observation of an Exotic Baryon in Exclusive Photoproduction from the Deuteron
In an exclusive measurement of the reaction , a
narrow peak that can be attributed to an exotic baryon with strangeness
is seen in the invariant mass spectrum. The peak is at
GeV/c with a measured width of 0.021 GeV/c FWHM, which is largely
determined by experimental mass resolution. The statistical significance of the
peak is . The mass and width of the observed peak are
consistent with recent reports of a narrow baryon by other experimental
groups.Comment: 5 pages, 5 figure
Search for the pentaquark in the reaction
A search for the \thp in the reaction was completed
using the CLAS detector at Jefferson Lab. A study of the same reaction,
published earlier, reported the observation of a narrow \thp resonance. The
present experiment, with more than 30 times the integrated luminosity of our
earlier measurement, does not show any evidence for a narrow pentaquark
resonance. The angle-integrated upper limit on \thp production in the mass
range of 1.52 to 1.56 GeV/c for the reaction is
0.3 nb (95% CL). This upper limit depends on assumptions made for the mass and
angular distribution of \thp production. Using \lamstar production as an
empirical measure of rescattering in the deuteron, the cross section upper
limit for the elementary reaction is estimated to be
a factor of 10 higher, {\it i.e.}, nb (95% CL).Comment: 5 figures, submitted to PRL, revised for referee comment
Measurement of the Polarized Structure Function for in the Resonance Region
The polarized longitudinal-transverse structure function
has been measured in the resonance region at and 0.65
GeV. Data for the reaction were taken at Jefferson Lab
with the CEBAF Large Acceptance Spectrometer (CLAS) using longitudinally
polarized electrons at an energy of 1.515 GeV. For the first time a complete
angular distribution was measured, permitting the separation of different
non-resonant amplitudes using a partial wave analysis. Comparison with previous
beam asymmetry measurements at MAMI indicate a deviation from the predicted
dependence of using recent phenomenological
models.Comment: 5 pages, LaTex, 4 eps figures: to be published in PRC/Rapid
Communications. Version 2 has revised Q^2 analysi
Two-Nucleon Momentum Distributions Measured in 3He(e,e'pp)n
We have measured the 3He(e,e'pp)n reaction at 2.2 GeV over a wide kinematic
range. The kinetic energy distribution for `fast' nucleons (p > 250 MeV/c)
peaks where two nucleons each have 20% or less, and the third nucleon has most
of the transferred energy. These fast pp and pn pairs are back-to-back with
little momentum along the three-momentum transfer, indicating that they are
spectators. Experimental and theoretical evidence indicates that we have
measured distorted two-nucleon momentum distributions by striking the third
nucleon and detecting the spectator correlated pair.Comment: 6 pages, 5 figures, submitted to PR
Survey of A_LT' asymmetries in semi-exclusive electron scattering on He4 and C12
Single spin azimuthal asymmetries A_LT' were measured at Jefferson Lab using
2.2 and 4.4 GeV longitudinally polarized electrons incident on He4 and C12
targets in the CLAS detector. A_LT' is related to the imaginary part of the
longitudinal-transverse interference and in quasifree nucleon knockout it
provides an unambiguous signature for final state interactions (FSI).
Experimental values of A_LT' were found to be below 5%, typically |A_LT'| < 3%
for data with good statistical precision. Optical Model in Eikonal
Approximation (OMEA) and Relativistic Multiple-Scattering Glauber Approximation
(RMSGA) calculations are shown to be consistent with the measured asymmetries.Comment: 9 pages, 5 figure
Onset of asymptotic scaling in deuteron photodisintegration
We investigate the transition from the nucleon-meson to quark-gluon
description of the strong interaction using the photon energy dependence of the
differential cross section for photon energies above 0.5 GeV and
center-of-mass proton angles between and . A possible
signature for this transition is the onset of cross section scaling
with the total energy squared, , at some proton transverse momentum, .
The results show that the scaling has been reached for proton transverse
momentum above about 1.1 GeV/c. This may indicate that the quark-gluon regime
is reached above this momentum.Comment: Accepted by PRL; 5 pages, 2 figure
First Measurement of Transferred Polarization in the Exclusive e p --> e' K+ Lambda Reaction
The first measurements of the transferred polarization for the exclusive ep
--> e'K+ Lambda reaction have been performed in Hall B at the Thomas Jefferson
National Accelerator Facility using the CLAS spectrometer. A 2.567 GeV electron
beam was used to measure the hyperon polarization over a range of Q2 from 0.3
to 1.5 (GeV/c)2, W from 1.6 to 2.15 GeV, and over the full center-of-mass
angular range of the K+ meson. Comparison with predictions of hadrodynamic
models indicates strong sensitivity to the underlying resonance contributions.
A non-relativistic quark model interpretation of our data suggests that the
s-sbar quark pair is produced with spins predominantly anti-aligned.
Implications for the validity of the widely used 3P0 quark-pair creation
operator are discussed.Comment: 6 pages, 4 figure
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