2,218 research outputs found
A regulatory governance perspective on health technology assessment (HTA) in France: the contextual mediation of common functional pressures
The new regulatory governance perspective has introduced several insights to the study of health technology assessment (HTA): it has broadened the scope for the analysis of HTA; it has provided a more sophisticated account of national diversity and the potential for cross-border policy learning; and, it has dissolved the distinction between HTA assessment and appraisal processes. In this paper, we undertake a qualitative study of the French process for HTA with a view to introducing a fourth insight: that the emergence and continuing function of national agencies for HTA follows a broadly evolutionary pattern in which contextual factors play an important mediating role. We demonstrate that the French process for HTA is characterised by distinctive institutions, processes and evidential requirements. Consistent with the mediating role of this divergent policy context, we argue that even initiatives for the harmonisation of national approaches to HTA are likely to meet with divergent national policy responses
Terrestrial–marine connectivity: patterns of terrestrial soil carbon deposition in coastal sediments determined by analysis of glomalin related soil protein
Glomalin, an arbuscular mycorrhizal protein component of soil, can be used as an indicator of terrigenous-derived carbon. We measured glomalin in sediments using the terrestrial end-member as a reference in four coastal settings: (1) intertidal seagrass meadows distributed over a rainfall gradient, (2) sediments inshore and offshore from the mouth of a river, (3) coastal coral reefs at various distances from the shore, and (4) intertidal wetlands with varying levels of groundwater influence. Across the rainfall gradient, glomalin in seagrass meadow sediments increased at sites with high mean annual rainfall during the wet season (r(2) = 0.27; F-1,F-29 = 5.75; p = 0.029). Glomalin decreased in inshore river sediments (terrestrial) to offshore (marine) sediments (r(2) = 0.81; F-1,F-17 = 71.7;
Folding and Hydrodynamics of a DNA i-Motif from the c-MYC Promoter Determined by Fluorescent Cytidine Analogs
AbstractThe four-stranded i-motif (iM) conformation of cytosine-rich DNA has importance to a wide variety of biochemical systems that range from their use in nanomaterials to potential roles in oncogene regulation. The iM structure is formed at slightly acidic pH, where hemiprotonation of cytosine results in a stable C-C+ basepair. Here, we performed fundamental studies to examine iM formation from a C-rich strand from the promoter of the human c-MYC gene. We used a number of biophysical techniques to characterize both the hydrodynamic properties and folding kinetics of a folded iM. Our hydrodynamic studies using fluorescence anisotropy decay and analytical ultracentrifugation show that the iM structure has a compact size in solution and displays the rigidity of a double strand. By studying the rates of circular dichroism spectral changes and quenching of fluorescent cytidine analogs, we also established a mechanism for the folding of a random coil oligo into the iM. In the course of determining this folding pathway, we established that the fluorescent dC analogs tC° and PdC can be used to monitor individual residues of an iM structure and to determine the pKa of an iM. We established that the C-C+ hydrogen bonding of certain bases initiates the folding of the iM structure. We also showed that substitutions in the loop regions of iMs give a distinctly different kinetic signature during folding compared with bases that are intercalated. Our data reveal that the iM passes through a distinct intermediate form between the unfolded and folded forms. Taken together, our results lay the foundation for using fluorescent dC analogs to follow structural changes during iM formation. Our technique may also be useful for examining folding and structural changes in more complex iMs
Spitzer Photometry of WISE-Selected Brown Dwarf and Hyper-Luminous Infrared Galaxy Candidates
We present Spitzer 3.6 and 4.5 m photometry and positions for a sample
of 1510 brown dwarf candidates identified by the WISE all-sky survey. Of these,
166 have been spectroscopically classified as objects with spectral types M(1),
L(7), T(146), and Y(12); Sixteen other objects are non-(sub)stellar in nature.
The remainder are most likely distant L and T dwarfs lacking spectroscopic
verification, other Y dwarf candidates still awaiting follow-up, and assorted
other objects whose Spitzer photometry reveals them to be background sources.
We present a catalog of Spitzer photometry for all astrophysical sources
identified in these fields and use this catalog to identify 7 fainter (4.5
m 17.0 mag) brown dwarf candidates, which are possibly wide-field
companions to the original WISE sources. To test this hypothesis, we use a
sample of 919 Spitzer observations around WISE-selected high-redshift
hyper-luminous infrared galaxy (HyLIRG) candidates. For this control sample we
find another 6 brown dwarf candidates, suggesting that the 7 companion
candidates are not physically associated. In fact, only one of these 7 Spitzer
brown dwarf candidates has a photometric distance estimate consistent with
being a companion to the WISE brown dwarf candidate. Other than this there is
no evidence for any widely separated ( 20 AU) ultra-cool binaries. As an
adjunct to this paper, we make available a source catalog of 7.33
objects detected in all of these Spitzer follow-up fields for use
by the astronomical community. The complete catalog includes the Spitzer 3.6
and 4.5 m photometry, along with positionally matched and
photometry from USNO-B; , , and photometry from 2MASS; and ,
, , and photometry from the WISE all-sky catalog
Genetic Comparison of a Croatian Isolate and CEPH European Founders
Human isolates have been postulated as a good resource for the identification of QTL due to reduced genetic diversity and a more homogeneous environment. Isolates may also have increased linkage disequilibrium (LD) due to small effective population size and, either loss or increase in frequency of alleles that are rare in the general population from which they originate. Here we investigate the difference in allele and genotype frequencies, LD and homozygous tracts between an isolate—several villages from the island of Vis in Croatia—and an outbred population of European origin: the Hapmap CEPH founders. Using the HumanHap300 v1 Genotyping BeadChip, we show that our population does not differ greatly from the reference CEU outbred population despite having a slightly higher proportion of monomorphic loci, a slightly higher long-range LD, and a greater proportion of individuals with long homozygous tracts. We conclude that genotyping arrays should perform equally well in our isolate as in outbred European populations for disease mapping studies and that SNP–trait associations discovered in our well-characterized Croatian isolate should be valid in the general European population from which they descend. Genet. Epidemiol. 34: 140–145, 2010. © 2009 Wiley-Liss, Inc
Five Kepler target stars that show multiple transiting exoplanet candidates
We present and discuss five candidate exoplanetary systems identified with
the Kepler spacecraft. These five systems show transits from multiple exoplanet
candidates. Should these objects prove to be planetary in nature, then these
five systems open new opportunities for the field of exoplanets and provide new
insights into the formation and dynamical evolution of planetary systems. We
discuss the methods used to identify multiple transiting objects from the
Kepler photometry as well as the false-positive rejection methods that have
been applied to these data. One system shows transits from three distinct
objects while the remaining four systems show transits from two objects. Three
systems have planet candidates that are near mean motion
commensurabilities---two near 2:1 and one just outside 5:2. We discuss the
implications that multitransiting systems have on the distribution of orbital
inclinations in planetary systems, and hence their dynamical histories; as well
as their likely masses and chemical compositions. A Monte Carlo study indicates
that, with additional data, most of these systems should exhibit detectable
transit timing variations (TTV) due to gravitational interactions---though none
are apparent in these data. We also discuss new challenges that arise in TTV
analyses due to the presence of more than two planets in a system.Comment: Accepted to Ap
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