1,371 research outputs found
Nonlinear Volatility of River Flux Fluctuations
We study the spectral properties of the magnitudes of river flux increments,
the volatility. The volatility series exhibits (i) strong seasonal periodicity
and (ii) strongly power-law correlations for time scales less than one year. We
test the nonlinear properties of the river flux increment series by randomizing
its Fourier phases and find that the surrogate volatility series (i) has almost
no seasonal periodicity and (ii) is weakly correlated for time scales less than
one year. We quantify the degree of nonlinearity by measuring (i) the amplitude
of the power spectrum at the seasonal peak and (ii) the correlation power-law
exponent of the volatility series.Comment: 5 revtex pages, 6 page
Entanglement of Dirac fields in non-inertial frames
We analyze the entanglement between two modes of a free Dirac field as seen
by two relatively accelerated parties. The entanglement is degraded by the
Unruh effect and asymptotically reaches a non-vanishing minimum value in the
infinite acceleration limit. This means that the state always remains entangled
to a degree and can be used in quantum information tasks, such as
teleportation, between parties in relative uniform acceleration. We analyze our
results from the point of view afforded by the phenomenon of entanglement
sharing and in terms of recent results in the area of multi-qubit
complementarity.Comment: 15 pages, with 8 figures (Mar 2006); accepted to Physical Review A,
July 2006 - slightly revise
Sensitive detection of glucagon aggregation using amyloid fibrilâspecific antibodies
Sensitive detection of protein aggregates is important for evaluating the quality of biopharmaceuticals and detecting misfolded proteins in several neurodegenerative diseases. However, it is challenging to detect extremely low concentrations (20 times more sensitive than detection using a conventional, amyloidâspecific fluorescent dye (Thioflavin T). We expect that this type of sensitive immunoassay can be readily integrated into the drug development process to improve the generation of safe and potent peptide therapeutics.Sensitive detection of protein aggregates is important for evaluating the quality of biopharmaceuticals and detecting misfolded proteins in several neurodegenerative diseases. However, it is challenging to detect extremely low concentrations (20 times more sensitive than conventional methods for detecting glucagon fibrils.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/150615/1/bit26994_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/150615/2/bit26994.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/150615/3/bit26994-sup-0001-Supporting_Information__submission_.pd
Computing prime factors with a Josephson phase qubit quantum processor
A quantum processor (QuP) can be used to exploit quantum mechanics to find
the prime factors of composite numbers[1]. Compiled versions of Shor's
algorithm have been demonstrated on ensemble quantum systems[2] and photonic
systems[3-5], however this has yet to be shown using solid state quantum bits
(qubits). Two advantages of superconducting qubit architectures are the use of
conventional microfabrication techniques, which allow straightforward scaling
to large numbers of qubits, and a toolkit of circuit elements that can be used
to engineer a variety of qubit types and interactions[6, 7]. Using a number of
recent qubit control and hardware advances [7-13], here we demonstrate a
nine-quantum-element solid-state QuP and show three experiments to highlight
its capabilities. We begin by characterizing the device with spectroscopy.
Next, we produces coherent interactions between five qubits and verify bi- and
tripartite entanglement via quantum state tomography (QST) [8, 12, 14, 15]. In
the final experiment, we run a three-qubit compiled version of Shor's algorithm
to factor the number 15, and successfully find the prime factors 48% of the
time. Improvements in the superconducting qubit coherence times and more
complex circuits should provide the resources necessary to factor larger
composite numbers and run more intricate quantum algorithms.Comment: 5 pages, 3 figure
Creation and restoration of coastal and estuarine habitats, a review of practical examples and a description of sequential guidelines for habitat creation and restoration in port areas
One of the themes of the NEW! Delta project is theme 3 "Creation and restoration of coastal and estuarine habitats" Within this theme two demonstration projects of habitat creation and restoration schemes have been implemented: one in the port of Antwerp and the other in the dune area "De Zilk" along the Dutch coast. The contributers of this study are from: ABP MER (United Kingdom), Alterra, Vlaamse overheid Afdeling Kust, DIREN Haute-Normandie, Grontmij, IMIEU Brussel, Haven van Antwerpen, Haven van Rotterdam, provincie Zuid-Hollan
14-3-3 Proteins Regulate a Cell-Intrinsic Switch from Sonic Hedgehog-Mediated Commissural Axon Attraction to Repulsion after Midline Crossing
SummaryAxons must switch responsiveness to guidance cues during development for correct pathfinding. Sonic Hedgehog (Shh) attracts spinal cord commissural axons ventrally toward the floorplate. We show that after crossing the floorplate, commissural axons switch their response to Shh from attraction to repulsion, so that they are repelled anteriorly by a posterior-high/anterior-low Shh gradient along the longitudinal axis. This switch is recapitulated in vitro with dissociated commissural neurons as they age, indicating that the switch is intrinsic and time dependent. 14-3-3 protein inhibition converted Shh-mediated repulsion of aged dissociated neurons to attraction and prevented the correct anterior turn of postcrossing commissural axons in vivo, an effect mediated through PKA. Conversely, overexpression of 14-3-3 proteins was sufficient to drive the switch from Shh-mediated attraction to repulsion both in vitro and in vivo. Therefore, we identify a 14-3-3 protein-dependent mechanism for a cell-intrinsic temporal switch in the polarity of axon turning responses
Theory and simulation of short-range models of globular protein solutions
We report theoretical and simulation studies of phase coexistence in model
globular protein solutions, based on short-range, central, pair potential
representations of the interaction among macro-particles. After reviewing our
previous investigations of hard-core Yukawa and generalised Lennard-Jones
potentials, we report more recent results obtained within a DLVO-like
description of lysozyme solutions in water and added salt. We show that a
one-parameter fit of this model based on Static Light Scattering and
Self-Interaction Chromatography data in the dilute protein regime, yields
demixing and crystallization curves in good agreement with experimental
protein-rich/protein-poor and solubility envelopes. The dependence of cloud and
solubility points temperature of the model on the ionic strength is also
investigated. Our findings highlight the minimal assumptions on the properties
of the microscopic interaction sufficient for a satisfactory reproduction of
the phase diagram topology of globular protein solutions.Comment: 17 pages, 8 figures, Proc. of Conference "Structural Arrest
Transitions in Colloidal Systems with Short-Range Attractions", Messina
(ITALY) 17-20 December 200
Entanglement Sharing in the Two-Atom Tavis-Cummings Model
Individual members of an ensemble of identical systems coupled to a common
probe can become entangled with one another, even when they do not interact
directly. We investigate how this type of multipartite entanglement is
generated in the context of a system consisting of two two-level atoms
resonantly coupled to a single mode of the electromagnetic field. The dynamical
evolution is studied in terms of the entanglements in the different bipartite
partitions of the system, as quantified by the I-tangle. We also propose a
generalization of the so-called residual tangle that quantifies the inherent
three-body correlations in our tripartite system. This enables us to completely
characterize the phenomenon of entanglement sharing in the case of the two-atom
Tavis-Cummings model, a system of both theoretical and experimental interest.Comment: 11 pages, 4 figures, submitted to PRA, v3 contains corrections to
small error
Structure-based design and synthesis of antiparasitic pyrrolopyrimidines targeting pteridine reductase 1
The treatment of Human African Trypanosomiasis remains a major unmet health need in sub-Saharan Africa. Approaches involving new molecular targets are important and pteridine reductase 1 (PTR1), an enzyme that reduces dihydrobiopterin in Trypanosoma spp. has been identified as a candidate target and it has been shown previously that substituted pyrrolo[2,3-d]pyrimidines are inhibitors of PTR1 from T. brucei (J. Med. Chem. 2010, 53, 221-229). In this study, 61 new pyrrolo[2,3-d]pyrimidines have been prepared, designed with input from new crystal structures of 23 of these compounds complexed with PTR1, and evaluated in screens for enzyme inhibitory activity against PTR1 and in vitro antitrypanosomal activity. 8 compounds were sufficiently active in both screens to take forward to in vivo evaluation. Thus although evidence for trypanocidal activity in a stage I disease model in mice was obtained, the compounds were too toxic to mice for further development
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