63 research outputs found
Diffractive point sets with entropy
After a brief historical survey, the paper introduces the notion of entropic
model sets (cut and project sets), and, more generally, the notion of
diffractive point sets with entropy. Such sets may be thought of as
generalizations of lattice gases. We show that taking the site occupation of a
model set stochastically results, with probabilistic certainty, in well-defined
diffractive properties augmented by a constant diffuse background. We discuss
both the case of independent, but identically distributed (i.i.d.) random
variables and that of independent, but different (i.e., site dependent) random
variables. Several examples are shown.Comment: 25 pages; dedicated to Hans-Ude Nissen on the occasion of his 65th
birthday; final version, some minor addition
Reconstructing the Inflaton Potential---in Principle and in Practice
Generalizing the original work by Hodges and Blumenthal, we outline a
formalism which allows one, in principle, to reconstruct the potential of the
inflaton field from knowledge of the tensor gravitational wave spectrum or the
scalar density fluctuation spectrum, with special emphasis on the importance of
the tensor spectrum. We provide some illustrative examples of such
reconstruction. We then discuss in some detail the question of whether one can
use real observations to carry out this procedure. We conclude that in
practice, a full reconstruction of the functional form of the potential will
not be possible within the foreseeable future. However, with a knowledge of the
dark matter components, it should soon be possible to combine
intermediate-scale data with measurements of large-scale cosmic microwave
background anisotropies to yield useful information regarding the potential.Comment: 39 pages plus 2 figures (upon request:[email protected]), LaTeX,
FNAL--PUB--93/029-A; SUSSEX-AST 93/3-
Nontrivial Dynamics in the Early Stages of Inflation
Inflationary cosmologies, regarded as dynamical systems, have rather simple
asymptotic behavior, insofar as the cosmic baldness principle holds.
Nevertheless, in the early stages of an inflationary process, the dynamical
behavior may be very complex. In this paper, we show how even a simple
inflationary scenario, based on Linde's ``chaotic inflation'' proposal,
manifests nontrivial dynamical effects such as the breakup of invariant tori,
formation of cantori and Arnol'd's diffusion. The relevance of such effects is
highlighted by the fact that even the occurrence or not of inflation in a given
Universe is dependent upon them.Comment: 26 pages, Latex, 9 Figures available on request, GTCRG-94-1
Calmodulin Interaction with hEAG1 Visualized by FRET Microscopy
BACKGROUND: Ca(2+)-mediated regulation of ion channels provides a link between intracellular signaling pathways and membrane electrical activity. Intracellular Ca(2+) inhibits the voltage-gated potassium channel EAG1 through the direct binding of calmodulin (CaM). Three CaM binding sites (BD-C1: 674-683, BD-C2: 711-721, BD-N: 151-165) have been identified in a peptide screen and were proposed to mediate binding. The participation of the three sites in CaM binding to the native channel, however, remains unclear. METHODOLOGY/PRINCIPAL FINDINGS: Here we studied the binding of Ca(2+)/CaM to the EAG channel by visualizing the interaction between YFP-labeled CaM and Cerulean-labeled hEAG1 in mammalian cells by FRET. The results of our cellular approach substantiate that two CaM binding sites are predominantly involved; the high-affinity 1-8-14 based CaM binding domain in the N-terminus and the second C-terminal binding domain BD-C2. Mutations at these sites completely abolished CaM binding to hEAG1. CONCLUSIONS/SIGNIFICANCE: We demonstrated that the BD-N and BD-C2 binding domains are sufficient for CaM binding to the native channel, and, therefore, that BD-C1 is unable to bind CaM independently
Recovering the Inflationary Potential and Primordial Power Spectrum With a Slow Roll Prior: Methodology and Application to WMAP 3 Year Data
We introduce a new method for applying an inflationary prior to a
cosmological dataset that includes relations between observables at arbitrary
order in the slow roll expansion. The process is based on the inflationary flow
equations, and the slow roll parameters appear explicitly in the cosmological
parameter set. We contrast our method to other ways of imposing an inflationary
prior on a cosmological dataset, and argue that this method is ideal for use
with heterogeneous datasets. In particular, it would be well suited to
exploiting any direct detection of fundamental tensor modes by a BBO-style
mission. To demonstrate the practical use of this method we apply it to the
WMAPI+All dataset, and the newly released WMAPII dataset on its own and
together with the SDSS data. We find that all basic classes of single field
inflationary models are still allowed at the 1-2sigma level, but the overall
parameter space is sharply constrained. In particular, we find evidence that
the combination of WMAPII+SDSS is sensitive to effects arising from terms that
are quadratic in the two leading-order slow roll parameters.Comment: v2 adds references and fixes typos. New explanatory material added
clarifying effects that depend on terms that are second order in the slow
roll parameters, and the impact of the beam parametrization and SZ prior on
the central value of n_s v3: Added refs, minor clarifications, title
modified. In press with JCAP v4: New figures, with minor smoothing artifacts
removed. Matches published version. v5 Fixed typo in caption of Figure
Identifying Regulators for EAG1 Channels with a Novel Electrophysiology and Tryptophan Fluorescence Based Screen
Ether-à-go-go (EAG) channels are expressed throughout the central nervous system and are also crucial regulators of cell cycle and tumor progression. The large intracellular amino- and carboxy- terminal domains of EAG1 each share similarity with known ligand binding motifs in other proteins, yet EAG1 channels have no known regulatory ligands.Here we screened a library of small biologically relevant molecules against EAG1 channels with a novel two-pronged screen to identify channel regulators. In one arm of the screen we used electrophysiology to assess the functional effects of the library compounds on full-length EAG1 channels. In an orthogonal arm, we used tryptophan fluorescence to screen for binding of the library compounds to the isolated C-terminal region.Several compounds from the flavonoid, indole and benzofuran chemical families emerged as binding partners and/or regulators of EAG1 channels. The two-prong screen can aid ligand and drug discovery for ligand-binding domains of other ion channels
Neodymium isotope constraints on provenance, dispersal, and climate-driven supply of Zambezi sediments along the Mozambique Margin during the past ∼45,000 years
Marine sediments deposited off the Zambezi River that drains a considerable part of the southeast African continent provide continuous records of the continental climatic and environmental conditions.
Here we present time series of neodymium (Nd) isotope signatures of the detrital sediment fraction during the past ~45,000 years, to reconstruct climate-driven changes in the provenance of clays deposited along the Mozambique Margin. Coherent with the surface current regime, the Nd isotope distribution in surface sediments reveals mixing of the alongshore flowing Zambezi suspension load with sediments supplied by smaller rivers located further north. To reconstruct past changes in sediment provenances, Nd isotope signatures
of clays that are not significantly fractionated during weathering processes have been obtained from core 64PE304-80, which was recovered just north of the Zambezi mouth at 1329 m water depth. Distinctly unradiogenic clay signatures (ENd values <214.2) are found during the Last Glacial Maximum, Heinrich Stadial 1, and Younger Dryas. In contrast, the Nd isotope record shows higher, more radiogenic isotope signatures during Marine Isotope Stage 3 and between ~15 and ~5 ka BP, the latter coinciding with the timing of the northern hemisphere African Humid Period. The clay-sized sediment fraction with the least radiogenic Nd isotope signatures was deposited during the Holocene, when the adjacent Mozambique Shelf became completely flooded. In general, the contribution of the distinctly unradiogenic Zambezi suspension load has followed the intensity of precession-forced monsoonal precipitation and enhanced during periods of increased southern hemisphere insolation and high-latitude northern hemispheric climate
variability
Genetic polymorphisms of the RAS-cytokine pathway and chronic kidney disease
Chronic kidney disease (CKD) in children is irreversible. It is associated with renal failure progression and atherosclerotic cardiovascular (CV) abnormalities. Nearly 60% of children with CKD are affected since birth with congenital or inherited kidney disorders. Preliminary evidence primarily from adult CKD studies indicates common genetic risk factors for CKD and atherosclerotic CV disease. Although multiple physiologic pathways share common genes for CKD and CV disease, substantial evidence supports our attention to the renin angiotensin system (RAS) and the interlinked inflammatory cascade because they modulate the progressions of renal and CV disease. Gene polymorphisms in the RAS-cytokine pathway, through altered gene expression of inflammatory cytokines, are potential factors that modulate the rate of CKD progression and CV abnormalities in patients with CKD. For studying such hypotheses, the cooperative efforts among scientific groups and the availability of robust and affordable technologies to genotype thousands of single nucleotide polymorphisms (SNPs) across the genome make genome-wide association studies an attractive paradigm for studying polygenic diseases such as CKD. Although attractive, such studies should be interpreted carefully, with a fundamental understanding of their potential weaknesses. Nevertheless, whole-genome association studies for diabetic nephropathy and future studies pertaining to other types of CKD will offer further insight for the development of targeted interventions to treat CKD and associated atherosclerotic CV abnormalities in the pediatric CKD population
Interaction entre les anions dodécylsulfate et chlorure et la sérum albumine humaine. Etude par autodiffusion de l'effet de compétition
Magnetic-Resonance Studies of the Interactions between Bovine-Serum Albumin and Surfactants. 1. Nature of Binding Site
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