1,019 research outputs found
Reframing nutritional microbiota studies to reflect an inherent metabolic flexibility of the human gut: A narrative review focusing on high-fat diets
There is a broad consensus in nutritional-microbiota research that high-fat (HF) diets are harmful to human health, at least in part through their modulation of the gut microbiota. However, various studies also support the inherent flexibility of the human gut and our microbiota’s ability to adapt to a variety of food sources, suggesting a more nuanced picture. In this article, we first discuss some problems fac-ing basic translational research and provide a different framework for thinking about diet and gut health in terms of metabolic flexibility. We then offer evidence that well-formulated HF diets, such as ketogenic diets, may provide healthful alternative fuel sources for the human gut. We place this in the context of cancer research, where this concern over HF diets is also expressed, and consider various potential objections concerning the effects of lipopolysaccharides, trimethylamine-N-oxide, and secondary bile acids on human gut health. We end by providing some gen-eral suggestions for how to improve research and clinical practice with respect to the gut microbiota when considering the framework of metabolic flexibility.Immunity, DEvelopment and Microbiota: Understanding the Continuous Construction of Biological Identit
Using a cognitive architecture to examine what develops
Different theories of development propose alternative mechanisms by which development occurs. Cognitive architectures can be used to examine the influence of each proposed mechanism of development while keeping all other mechanisms constant. An ACT-R computational model that matched adult behavior in solving a 21-block pyramid puzzle was created. The model was modified in three ways that corresponded to mechanisms of development proposed by developmental theories. The results showed that all the modifications (two of capacity and one of strategy choice) could approximate the behavior of 7-year-old children on the task. The strategy-choice modification provided the closest match on the two central measures of task behavior (time taken per layer, r = .99, and construction attempts per layer, r = .73). Modifying cognitive architectures is a fruitful way to compare and test potential developmental mechanisms, and can therefore help in specifying “what develops.
A genome-wide association study in multiple system atrophy
Objective: To identify genetic variants that play a role in the pathogenesis of multiple system atrophy
(MSA), we undertook a genome-wide association study (GWAS).
Methods: We performed a GWAS with .5 million genotyped and imputed single nucleotide polymorphisms
(SNPs) in 918 patients with MSA of European ancestry and 3,864 controls. MSA
cases were collected from North American and European centers, one third of which were neuropathologically
confirmed.
Results: We found no significant loci after stringent multiple testing correction. A number of regions
emerged as potentially interesting for follow-up at p , 1 3 1026, including SNPs in the
genes FBXO47, ELOVL7, EDN1, and MAPT. Contrary to previous reports, we found no association
of the genes SNCA and COQ2 with MSA.
Conclusions: We present a GWAS in MSA.We have identified several potentially interesting gene
loci, including the MAPT locus, whose significance will have to be evaluated in a larger sample set.
Common genetic variation in SNCA and COQ2 does not seem to be associated with MSA. In the
future, additional samples of well-characterized patients with MSA will need to be collected to
perform a larger MSA GWAS, but this initial study forms the basis for these next steps
Experimental implications of quantum phase fluctuations in layered superconductors
I study the effect of quantum and thermal phase fluctuations on the in-plane
and c-axis superfluid stiffness of layered d-wave superconductors. First, I
show that quantum phase fluctuations in the superconductor can be damped in the
presence of external screening of Coulomb interactions, and suggest an
experiment to test the importance of these fluctuations, by placing a metal in
close proximity to the superconductor to induce such screening. Second, I show
that a combination of quantum phase fluctuations and the linear temperature
dependence of the in-plane superfluid stiffness leads to a linear temperature
dependence of the c-axis penetration depth, below a temperature scale
determined by the magnitude of in-plane dissipation.Comment: 6 pgs, 1 figure, minor changes in comparison with c-axis expt, final
published versio
Exploring disparities in acute myocardial infarction events between Aboriginal and non-Aboriginal Australians: roles of age, gender, geography and area-level disadvantage
We investigated disparities in rates of acute myocardial infarction (AMI) between Aboriginal and non-Aboriginal people in the 199 Statistical Local Areas (SLAs) in New South Wales, Australia. Using routinely collected and linked hospital and mortality data from 2002 to 2007, we developed multilevel Poisson regression models to estimate the relative rates of first AMI events in the study period accounting for area of residence. Rates of AMI in Aboriginal people were more than two times that in non-Aboriginal people, with the disparity greatest in more disadvantaged and remote areas. AMI rates in Aboriginal people varied significantly by SLA, as did the Aboriginal to non-Aboriginal rate ratio. We identified almost 30 priority areas for universal and targeted preventive interventions that had both high rates of AMI for Aboriginal people and large disparities in rates
Phase fluctuations, dissipation and superfluid stiffness in d-wave superconductors
We study the effect of dissipation on quantum phase fluctuations in d-wave
superconductors. Dissipation, arising from a nonzero low frequency optical
conductivity which has been measured in experiments below , has two
effects: (1) a reduction of zero point phase fluctuations, and (2) a reduction
of the temperature at which one crosses over to classical thermal fluctuations.
For parameter values relevant to the cuprates, we show that the crossover
temperature is still too large for classical phase fluctuations to play a
significant role at low temperature. Quasiparticles are thus crucial in
determining the linear temperature dependence of the in-plane superfluid
stiffness. Thermal phase fluctuations become important at higher temperatures
and play a role near .Comment: Presentation improved, new references added (10 latex pages, 3 eps
figures). submitted to PR
Atmospheric Heating and Wind Acceleration: Results for Cool Evolved Stars based on Proposed Processes
A chromosphere is a universal attribute of stars of spectral type later than
~F5. Evolved (K and M) giants and supergiants (including the zeta Aurigae
binaries) show extended and highly turbulent chromospheres, which develop into
slow massive winds. The associated continuous mass loss has a significant
impact on stellar evolution, and thence on the chemical evolution of galaxies.
Yet despite the fundamental importance of those winds in astrophysics, the
question of their origin(s) remains unsolved. What sources heat a chromosphere?
What is the role of the chromosphere in the formation of stellar winds? This
chapter provides a review of the observational requirements and theoretical
approaches for modeling chromospheric heating and the acceleration of winds in
single cool, evolved stars and in eclipsing binary stars, including physical
models that have recently been proposed. It describes the successes that have
been achieved so far by invoking acoustic and MHD waves to provide a physical
description of plasma heating and wind acceleration, and discusses the
challenges that still remain.Comment: 46 pages, 9 figures, 1 table; modified and unedited manuscript;
accepted version to appear in: Giants of Eclipse, eds. E. Griffin and T. Ake
(Berlin: Springer
Is the evidence for dark energy secure?
Several kinds of astronomical observations, interpreted in the framework of
the standard Friedmann-Robertson-Walker cosmology, have indicated that our
universe is dominated by a Cosmological Constant. The dimming of distant Type
Ia supernovae suggests that the expansion rate is accelerating, as if driven by
vacuum energy, and this has been indirectly substantiated through studies of
angular anisotropies in the cosmic microwave background (CMB) and of spatial
correlations in the large-scale structure (LSS) of galaxies. However there is
no compelling direct evidence yet for (the dynamical effects of) dark energy.
The precision CMB data can be equally well fitted without dark energy if the
spectrum of primordial density fluctuations is not quite scale-free and if the
Hubble constant is lower globally than its locally measured value. The LSS data
can also be satisfactorily fitted if there is a small component of hot dark
matter, as would be provided by neutrinos of mass 0.5 eV. Although such an
Einstein-de Sitter model cannot explain the SNe Ia Hubble diagram or the
position of the `baryon acoustic oscillation' peak in the autocorrelation
function of galaxies, it may be possible to do so e.g. in an inhomogeneous
Lemaitre-Tolman-Bondi cosmology where we are located in a void which is
expanding faster than the average. Such alternatives may seem contrived but
this must be weighed against our lack of any fundamental understanding of the
inferred tiny energy scale of the dark energy. It may well be an artifact of an
oversimplified cosmological model, rather than having physical reality.Comment: 12 pages, 5 figures; to appear in a special issue of General
Relativity and Gravitation, eds. G.F.R. Ellis et al; Changes: references
reformatted in journal style - text unchange
Neutral weak currents in pion electroproduction on the nucleon
Parity violating asymmetry in inclusive scattering of longitudinally
polarized electrons by unpolarized protons with or meson
production, is calculated as a function of the momentum transfer squared
and the total energy of the -system. This asymmetry, which is
induced by the interference of the one-photon exchange amplitude with the
parity-odd part of the -exchange amplitude, is calculated for the
processes ( is a virtual photon and
a virtual Z-boson) considering the -contribution in the channel,
the standard Born contributions and vector meson ( and )
exchanges in the channel. Taking into account the known isotopic properties
of the hadron electromagnetic and neutral currents, we show that the P-odd term
is the sum of two contributions. The main term is model independent and it can
be calculated exactly in terms of fundamental constants. It is found to be
linear in . The second term is a relatively small correction which is
determined by the isoscalar component of the electromagnetic current. Near
threshold and in the -region, this isoscalar part is much smaller (in
absolute value) than the isovector one: its contribution to the asymmetry
depend on the polarization state (longitudinal or transverse) of the virtual
photon.Comment: 30 pages 9 figure
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