172 research outputs found
Antioxidant intervention in rheumatoid arthritis: results of an open pilot study
There is evidence that reactive oxygen species play a causal role in auto-immune diseases, such as rheumatoid arthritis (RA). Despite the supporting evidence for a beneficial effect of antioxidants on clinical characteristics of RA, the right balance for optimal effectiveness of antioxidants is largely unknown. To determine the potential beneficial effects of an antioxidant intervention on clinical parameters for RA, an open pilot study was designed. Eight non-smoking female patients with rheumatoid factor + RA and a Disease Activity Score (DAS 28) higher than 2.5 were enrolled in the study. Patients had to be receiving stable non-steroidal anti-inflammatory drug treatment and/or âsecond lineâ medication for at least 3Â months. The pilot group consumed 20Â g of antioxidant-enriched spread daily during a period of 10Â weeks. The intervention was stopped after 10Â weeks and was followed by a âwash-outâ period of 4Â weeks. At tâ=â0, tâ=â10Â weeks and tâ=â14Â weeks, patientsâ condition was assessed by means of DAS. In addition, standard laboratory analyses were performed, and blood-samples for antioxidants were taken. The antioxidant-enriched spread was well tolerated. All laboratory measures of inflammatory activity and oxidative modification were generally unchanged. However, the number of swollen and painful joints were significantly decreased and general health significantly increased, as reflected by a significantly improved (1.6) DAS at tâ=â10Â weeks. The antioxidant effect was considered beneficial as, compared to the scores at tâ=â0, the DAS significantly reduced at tâ=â10Â weeks. Increase of the DAS (0.7) after the âwash-out periodâ at tâ=â14 confirmed a causal relation between changes in clinical condition and antioxidants. This open pilot study aimed to assess the clinical relevance of an antioxidant intervention as a first step in assessing potential beneficial effects of antioxidants on rheumatoid arthritis. These conclusions need to be validated in a larger controlled study population
The rate of beneficial mutations surfing on the wave of a range expansion
Many theoretical and experimental studies suggest that range expansions can
have severe consequences for the gene pool of the expanding population. Due to
strongly enhanced genetic drift at the advancing frontier, neutral and weakly
deleterious mutations can reach large frequencies in the newly colonized
regions, as if they were surfing the front of the range expansion. These
findings raise the question of how frequently beneficial mutations successfully
surf at shifting range margins, thereby promoting adaptation towards a
range-expansion phenotype. Here, we use individual-based simulations to study
the surfing statistics of recurrent beneficial mutations on wave-like range
expansions in linear habitats. We show that the rate of surfing depends on two
strongly antagonistic factors, the probability of surfing given the spatial
location of a novel mutation and the rate of occurrence of mutations at that
location. The surfing probability strongly increases towards the tip of the
wave. Novel mutations are unlikely to surf unless they enjoy a spatial head
start compared to the bulk of the population. The needed head start is shown to
be proportional to the inverse fitness of the mutant type, and only weakly
dependent on the carrying capacity. The second factor is the mutation
occurrence which strongly decreases towards the tip of the wave. Thus, most
successful mutations arise at an intermediate position in the front of the
wave. We present an analytic theory for the tradeoff between these factors that
allows to predict how frequently substitutions by beneficial mutations occur at
invasion fronts. We find that small amounts of genetic drift increase the
fixation rate of beneficial mutations at the advancing front, and thus could be
important for adaptation during species invasions.Comment: 21 pages, 7 figures; to appear in PLoS Computational Biolog
Why Did Memetics Fail? Comparative Case Study
Although the theory of memetics appeared highly promising at the beginning, it is no longer considered a scientific theory among contemporary evolutionary scholars. This study aims to compare the genealogy of memetics with the historically more successful gene-culture coevolution theory. This comparison is made in order to determine the constraints that emerged during the internal development of the memetics theory that could bias memeticists to work on the ontology of meme units as opposed to hypotheses testing, which was adopted by the gene-culture scholars. I trace this problem back to the diachronic development of memetics to its origin in the gene-centered anti-group-selectionist argument of George C. Williams and Richard Dawkins. The strict adoption of this argument predisposed memeticists with the a priori idea that there is no evolution without discrete units of selection, which in turn, made them dependent on the principal separation of biological and memetic fitness. This separation thus prevented memeticists from accepting an adaptationist view of culture which, on the contrary, allowed gene-culture theorists to attract more scientists to test the hypotheses, creating the historical success of the gene-culture coevolution theory
Exciton states and optical properties of CdSe nanocrystals
The optical spectra of CdSe nanocrystals up to 55 A in diameter are analyzed
in a wide range of energies from the fine structure of the low-energy
excitations to the so-called high-energy transitions. We apply a symmetry-based
method in two steps. First we take the tight-binding (TB) parameters from the
bulk sp^{3}s^{*} TB model, extended to include the spin-orbit interaction. The
full single-particle spectra are obtained from an exact diagonalization by
using a group-theoretical treatment. The electron-hole interaction is next
introduced: Both the Coulomb (direct) and exchange terms are considered. The
high-energy excitonic transitions are studied by computing the electric dipole
transition probabilities between single-particle states, while the transition
energies are obtained by taking into account the Coulomb interaction. The fine
structure of the lowest excitonic states is analyzed by including the
electron-hole exchange interaction and the wurtzite crystal-field terms in the
exciton Hamiltonian. The latter is diagonalized in the single electron-hole
pair excitation subspace of progressively increasing size until convergence.
The peaks in the theoretical transition spectra are then used to deduce the
resonant and nonresonant Stokes shifts, which are compared with their measured
values in photoluminescence experiments. We find that the final results depend
on the crystal-field term, the relative size of the surface and the degree of
saturation of the dangling bonds. The results show a satisfactory agreement
with the available experimental data.Comment: Revtex, 24 pages, 7 Postscript figure
Measurement of inclusive D*+- and associated dijet cross sections in photoproduction at HERA
Inclusive photoproduction of D*+- mesons has been measured for photon-proton
centre-of-mass energies in the range 130 < W < 280 GeV and a photon virtuality
Q^2 < 1 GeV^2. The data sample used corresponds to an integrated luminosity of
37 pb^-1. Total and differential cross sections as functions of the D*
transverse momentum and pseudorapidity are presented in restricted kinematical
regions and the data are compared with next-to-leading order (NLO) perturbative
QCD calculations using the "massive charm" and "massless charm" schemes. The
measured cross sections are generally above the NLO calculations, in particular
in the forward (proton) direction. The large data sample also allows the study
of dijet production associated with charm. A significant resolved as well as a
direct photon component contribute to the cross section. Leading order QCD
Monte Carlo calculations indicate that the resolved contribution arises from a
significant charm component in the photon. A massive charm NLO parton level
calculation yields lower cross sections compared to the measured results in a
kinematic region where the resolved photon contribution is significant.Comment: 32 pages including 6 figure
Two-dimensional spatial power spectra of photospheric velocity fluctuations
Two-dimensional spatial autocorrelation functions and power spectral density distributions were obtained from high-resolution velocity spectroheliograms. Although the autocorrelation functions indicate the existence of velocity cells of size roughly 2500 to 3500 km, the power spectra fail to reveal them because the cells are not strictly spatially periodic.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43736/1/11207_2004_Article_BF00162429.pd
Measurement of Jet Shapes in Photoproduction at HERA
The shape of jets produced in quasi-real photon-proton collisions at
centre-of-mass energies in the range GeV has been measured using the
hadronic energy flow. The measurement was done with the ZEUS detector at HERA.
Jets are identified using a cone algorithm in the plane with a
cone radius of one unit. Measured jet shapes both in inclusive jet and dijet
production with transverse energies GeV are presented. The jet
shape broadens as the jet pseudorapidity () increases and narrows
as increases. In dijet photoproduction, the jet shapes have been
measured separately for samples dominated by resolved and by direct processes.
Leading-logarithm parton-shower Monte Carlo calculations of resolved and direct
processes describe well the measured jet shapes except for the inclusive
production of jets with high and low . The observed
broadening of the jet shape as increases is consistent with the
predicted increase in the fraction of final state gluon jets.Comment: 29 pages including 9 figure
Current polarity-dependent manipulation of antiferromagnetic domains
Antiferromagnets have several favourable properties as active elements in spintronic devices, including ultra-fast dynamics, zero stray fields and insensitivity to external magnetic fields. Tetragonal CuMnAs is a testbed system in which the antiferromagnetic order parameter can be switched reversibly at ambient conditions using electrical currents. In previous experiments, orthogonal in-plane current pulses were used to induce 90° rotations of antiferromagnetic domains and demonstrate the operation of all-electrical memory bits in a multi-terminal geometry. Here, we demonstrate that antiferromagnetic domain walls can be manipulated to realize stable and reproducible domain changes using only two electrical contacts. This is achieved by using the polarity of the current to switch the sign of the current-induced effective field acting on the antiferromagnetic sublattices. The resulting reversible domain and domain wall reconfigurations are imaged using X-ray magnetic linear dichroism microscopy, and can also be detected electrically. Switching by domain-wall motion can occur at much lower current densities than those needed for coherent domain switching
Climate Science Special Report: Fourth National Climate Assessment (NCA4), Volume I
New observations and new research have increased our understanding of past, current, and future climate change since the Third U.S. National Climate Assessment (NCA3) was published in May 2014. This Climate Science Special Report (CSSR) is designed to capture that new information and build on the existing body of science in order to summarize the current state of knowledge and provide the scientific foundation for the Fourth National Climate Assessment (NCA4)
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