806 research outputs found
Habituation is not neutral or equal: Individual differences in tolerance suggest an overlooked personality trait
In behavioral studies, observer effects can be substantial, even for habituated animals, but few studies account for potential observer-related phenomenon empirically. We used wild, habituated chacma baboons to explore two key assumptions of behavioral ecology (i) that observers become a âneutralâ stimulus and (ii) that habituation is âequalâ across group members. Using flight initiation distance (FID) methods within a personality paradigm, the behavioral responses of baboons suggested that observers were not perceived as neutral but instead viewed as a high-ranking social threat. Habituation was also not equal across group members, with repeatable individual differences more important than contextual factors (e.g., habitat) in determining the distance at which baboons visually oriented or displaced from observers. A strong correlation between individual visual tolerance and displacement tolerance (i.e., convergent validity) indicated a personality trait. We offer several suggestions for how to account for these factors and minimize potential bias in future studies
Monkey-based Research on Human Disease: The Implications of Genetic Differences
Assertions that the use of monkeys to investigate human diseases is valid scientifically are frequently based on a reported 90â93% genetic similarity between the species. Critical analyses of the relevance of monkey studies to human biology, however, indicate that this genetic similarity does not result in sufficient physiological similarity for monkeys to constitute good models for research, and that monkey data do not translate well to progress in clinical practice for humans. Salient examples include the failure of new drugs in clinical trials, the highly different infectivity and pathology of SIV/HIV, and poor extrapolation of research on Alzheimerâs disease, Parkinsonâs disease and stroke. The major molecular differences underlying these inter-species phenotypic disparities have been revealed by comparative genomics and molecular biology â there are key differences in all aspects of gene expression and protein function, from chromosome and chromatin structure to post-translational modification. The collective effects of these differences are striking, extensive and widespread, and they show that the superficial similarity between human and monkey genetic sequences is of little benefit for biomedical research. The extrapolation of biomedical data from monkeys to humans is therefore highly unreliable, and the use of monkeys must be considered of questionable value, particularly given the breadth and potential of alternative methods of enquiry that are currently available to scientists
Fitness declines toward range limits and local adaptation to climate affect dispersal evolution during climate-induced range shifts
Sherpa Romeo yellow journal (pre-print only, accepted for publication)Dispersal
ability
will
largely
determine
whether
species
track
their
climatic
niches
during
climate
change,
a
process
especially
important
for
populations
at
contracting
(low-Âlatitude/low-Âelevation)
range
limits
that
otherwise
risk
extinction.
We
investigate
whether
dispersal
evolution
at
contracting
range
limits
is
facilitated
by
two
processes
that
potentially
enable
edge
populations
to
experience
and
adjust
to
the
effects
of
climate
deterioration
before
they
cause
extinction:
a)
climate-Ââinduced
fitness
declines
toward
range
limits,
and
b)
local
adaptation
to
a
shifting
climate
gradient.
We
simulate
a
species
distributed
continuously
along
a
temperature
gradient
using
a
spatially
explicit,
individual-Ââ
based
model.
We
compare
range-Ââwide
dispersal
evolution
during
climate
stability
vs.
directional
climate
change,
with
uniform
fitness
vs.
fitness
that
declines
toward
range
limits
(RLs),
and
for
a
single
climate
genotype
vs.
multiple
genotypes
locally
adapted
to
temperature.
Dispersal
decreased
toward
stable
RLs
when
range-Ââwide
fitness
was
uniform,
but
increased
when
fitness
declined
toward
RLs,
due
to
highly
dispersive
genotypes
maintaining
sink
populations
at
RLs,
increased
kin
selection
in
smaller
populations,
and
an
emergent
fitness
asymmetry
that
favoured
dispersal
in
low-Ââquality
habitat.
However,
this
initial
dispersal
advantage
at
low-Ââfitness
RLs
did
not
facilitate
climate
tracking,
as
it
was
outweighed
by
an
increased
probability
of
extinction.
Locally-Ââadapted
genotypes
benefited
from
staying
close
to
their
climate
optima;
this
selected
against
dispersal
under
stable
climates
but
for
increased
dispersal
throughout
shifting
ranges,
compared
to
cases
without
local
adaptation.
Dispersal
increased
at
expanding
RLs
in
most
scenarios,
but
only
increased
at
the
range
centre
and
contracting
RLs
given
local
adaptation
to
climate
Are ultracompact minihalos really ultracompact?
Ultracompact minihalos (UCMHs) have emerged as a valuable probe of the primordial power spectrum of density fluctuations at small scales. UCMHs are expected to form at early times in regions with ÎŽÏ/Ïâł10-3, and they are theorized to possess an extremely compact Ïâr-9/4 radial density profile, which enhances their observable signatures. Nonobservation of UCMHs can thus constrain the primordial power spectrum. Using N-body simulations to study the collapse of extreme density peaks at zâ1000, we show that UCMHs forming under realistic conditions do not develop the Ïâr-9/4 profile and instead develop either Ïâr-3/2 or Ïâr-1 inner density profiles depending on the shape of the power spectrum. We also demonstrate via idealized simulations that self-similarity - the absence of a scale length - is necessary to produce a halo with the Ïâr-9/4 profile, and we argue that this implies such halos cannot form from a Gaussian primordial density field. Prior constraints derived from UCMH nonobservation must be reworked in light of this discovery. Although the shallower density profile reduces UCMH visibility, our findings reduce their signal by as little as O(10-2) while allowing later-forming halos to be considered, which suggests that new constraints could be significantly stronger
Density profiles of ultracompact minihalos: Implications for constraining the primordial power spectrum
Enhanced density fluctuations on small scales would lead to the formation of numerous dark matter minihalos, so limits on the minihalo abundance can place upper bounds on the small-scale primordial power spectrum. In particular, the ultracompact minihalo (UCMH), a dark matter structure hypothesized to possess a r-9/4 density profile due to its formation at zâ„1000, has been used to establish an upper bound on the primordial power spectrum at scales smaller than 2 Mpc. The extreme slope of this density profile amplifies the observational signals of UCMHs. However, we recently showed via N-body simulations that the r-9/4 density profile does not develop in realistic formation scenarios, throwing UCMH-derived power spectrum constraints into question. Instead, minihalos develop shallower inner profiles with power-law indices between -3/2 and -1. In this paper, we expand on that result and discuss its implications. Using a model that is calibrated to simulation results and predicts halo structures in spiked power spectra based on their formation times, we calculate new upper bounds on the primordial power spectrum based on limits on the dark matter annihilation rate within the Galaxy. We find that despite assuming shallower profiles, this minihalo model actually yields stronger constraints than the previous UCMH picture owing to its inclusion of all minihalos instead of only the earliest-forming ones
First integrals of Ginzburg-Landau equations and stability criteria for vortex-free state in unconventional superconductors
The first integrals of the Ginzburg-Landau equations for a vortex-free state
of superconductors with different mixed symmetries of the order parameter are
found. The general boundary conditions for the order parameter at the ideal
interface between the superconductor and vacuum are derived. Based on these
integrals and boundary conditions, we analyze the stability criteria for
vortex-free state in unconventional superconductors. The threshold field above
which the Abrikosov vortices can enter the superconductor is found to be higher
or equal to the thermodynamic critical field for all states under study.Comment: 8 pages, pdf file, no figure
An Anglo-Saxon execution cemetery at Walkington Wold, Yorkshire
This paper presents a re-evaluation of a cemetery excavated over
30 years ago at Walkington Wold in east Yorkshire. The cemetery is
characterized by careless burial on diverse alignments, and by the fact that
most of the skeletons did not have associated crania. The cemetery has been
variously described as being the result of an early post-Roman massacre, as
providing evidence for a âCelticâ head cult or as an Anglo-Saxon execution
cemetery. In order to resolve the matter, radiocarbon dates were acquired and
a re-examination of the skeletal remains was undertaken. It was confirmed that
the cemetery was an Anglo-Saxon execution cemetery, the only known example
from northern England, and the site is set into its wider context in the paper
T-bet controls intestinal mucosa immune responses via repression of type 2 innate lymphoid cell function
Innate lymphoid cells (ILCs) play an important role in regulating immune responses at mucosal surfaces. The transcription factor T-bet is crucial for the function of ILC1s and NCR+ ILC3s and constitutive deletion of T-bet prevents the development of these subsets. Lack of T-bet in the absence of an adaptive immune system causes microbiota-dependent colitis to occur due to aberrant ILC3 responses. Thus, T-bet expression in the innate immune system has been considered to dampen pathogenic immune responses. Here, we show that T-bet plays an unexpected role in negatively regulating innate type 2 responses, in the context of an otherwise intact immune system. Selective loss of T-bet in ILCs leads to the expansion and increased activity of ILC2s, which has a functionally important impact on mucosal immunity, including enhanced protection from Trichinella spiralis infection and inflammatory colitis. Mechanistically, we show that T-bet controls the intestinal ILC pool through regulation of IL-7 receptor signalling. These data demonstrate that T-bet expression in ILCs acts as the key transcriptional checkpoint in regulating pathogenic vs. protective mucosal immune responses, which has significant implications for the understanding of the pathogenesis of inflammatory bowel diseases and intestinal infections
Low-diffusion Xe-He gas mixtures for rare-event detection: electroluminescence yield
High pressure xenon Time Projection Chambers (TPC) based on secondary scintillation (electroluminescence) signal amplification are being proposed for rare event detection such as directional dark matter, double electron capture and double beta decay detection. The discrimination of the rare event through the topological signature of primary ionisation trails is a major asset for this type of TPC when compared to single liquid or double-phase TPCs, limited mainly by the high electron diffusion in pure xenon. Helium admixtures with xenon can be an attractive solution to reduce the electron diffu- sion significantly, improving the discrimination efficiency of these optical TPCs. We have measured the electroluminescence (EL) yield of XeâHe mixtures, in the range of 0 to 30% He and demonstrated the small impact on the EL yield of the addition of helium to pure xenon. For a typical reduced electric field of 2.5 kV/cm/bar in the EL region, the EL yield is lowered by ⌠2%, 3%, 6% and 10% for 10%, 15%, 20% and 30% of helium concentration, respectively. This decrease is less than what has been obtained from the most recent simulation framework in the literature. The impact of the addition of helium on EL statistical fluctuations is negligible, within the experimental uncertainties. The present results are an important benchmark for the simulation tools to be applied to future optical TPCs based on Xe-He mixtures. [Figure not available: see fulltext.]
- âŠ