1,486 research outputs found
The mod 2 cohomology of fixed point sets of anti-symplectic involutions
Let be a compact, connected symplectic manifold with a Hamiltonian action
of a compact -dimensional torus . Suppose that is an
anti-symplectic involution compatible with the -action. The real locus of
is , the fixed point set of . Duistermaat uses Morse theory to
give a description of the ordinary cohomology of in terms of the cohomology
of . There is a residual \G=(\Zt)^n action on , and we can use
Duistermaat's result, as well as some general facts about equivariant
cohomology, to prove an equivariant analogue to Duistermaat's theorem. In some
cases, we can also extend theorems of Goresky-Kottwitz-MacPherson and
Goldin-Holm to the real locus.Comment: 21 pages, 1 figur
Measurement of the Homogeneous Contact of a Unitary Fermi gas
By selectively probing the center of a trapped gas, we measure the local, or
homogeneous, contact of a unitary Fermi gas as a function of temperature. Tan's
contact, C, is proportional to the derivative of the energy with respect to the
interaction strength, and is thus an essential thermodynamic quantity for a gas
with short-range correlations. Theoretical predictions for the temperature
dependence of C differ substantially, especially near the superfluid
transition, Tc, where C is predicted to either sharply decrease, sharply
increase, or change very little. For T/T_F>0.4, our measurements of the
homogeneous gas contact show a gradual decrease of C with increasing
temperature, as predicted by theory. We observe a sharp decrease in C at
T/T_F=0.16, which may be due to the superfluid phase transition. While a sharp
decrease in C below Tc is predicted by some many-body theories, we find that
none of the predictions fully accounts for the data.Comment: 5 pages, including a supplementary material section (10 pages).
Rewriting of the introduction and discussion section
Meeting the Expectations of Your Heritage Culture: Links between Attachment Style, Intragroup Marginalisation, and Psychological Adjustment
This article has been made available through the Brunel Open Access Publishing Fund.This article has been made available through the Brunel Open Access Publishing Fund.Do insecurely-attached individuals perceive greater rejection from their heritage culture? Few studies have examined the antecedents and outcomes of this perceived rejection – termed intragroup marginalisation – in spite of its implications for the adjustment of cultural migrants to the mainstream culture. The present study investigated whether anxious and avoidant attachment orientations among cultural migrants were associated with greater intragroup marginalisation and, in turn, with lower subjective well-being and flourishing, and higher acculturative stress. Anxious attachment was associated with heightened intragroup marginalisation from friends and, in turn, with increased acculturative stress; anxious attachment was also associated with increased intragroup marginalisation from family. Avoidant attachment was linked with increased intragroup marginalisation from family and, in turn, with decreased subjective well-being
Climate Change, Woodpeckers, and Forests: Current Trends and Future Modeling Needs
The structure and composition of forest ecosystems are expected to shift with climate‐induced changes in precipitation, temperature, fire, carbon mitigation strategies, and biological disturbance. These factors are likely to have biodiversity implications. However, climate‐driven forest ecosystem models used to predict changes to forest structure and composition are not coupled to models used to predict changes to biodiversity. We proposed integrating woodpecker response (biodiversity indicator) with forest ecosystem models. Woodpeckers are a good indicator species of forest ecosystem dynamics, because they are ecologically constrained by landscape‐scale forest components, such as composition, structure, disturbance regimes, and management activities. In addition, they are correlated with forest avifauna community diversity. In this study, we explore integrating woodpecker and forest ecosystem climate models. We review climate–woodpecker models and compare the predicted responses to observed climate‐induced changes. We identify inconsistencies between observed and predicted responses, explore the modeling causes, and identify the models pertinent to integration that address the inconsistencies. We found that predictions in the short term are not in agreement with observed trends for 7 of 15 evaluated species. Because niche constraints associated with woodpeckers are a result of complex interactions between climate, vegetation, and disturbance, we hypothesize that the lack of adequate representation of these processes in the current broad‐scale climate–woodpecker models results in model–data mismatch. As a first step toward improvement, we suggest a conceptual model of climate–woodpecker–forest modeling for integration. The integration model provides climate‐driven forest ecosystem modeling with a measure of biodiversity while retaining the feedback between climate and vegetation in woodpecker climate change modeling
Perilipin regulates the thermogenic actions of norepinephrine in brown adipose tissue
In response to cold, norepinephrine (NE)-induced triacylglycerol hydrolysis (lipolysis) in adipocytes of brown adipose tissue (BAT) provides fatty acid substrates to mitochondria for heat generation (adaptive thermogenesis). NE-induced lipolysis is mediated by protein kinase A (PKA)-dependent phosphorylation of perilipin, a lipid droplet-associated protein that is the major regulator of lipolysis. We investigated the role of perilipin PKA phosphorylation in BAT NE-stimulated thermogenesis using a novel mouse model in which a mutant form of perilipin, lacking all six PKA phosphorylation sites, is expressed in adipocytes of perilipin knockout (Peri KO) mice. Here, we show that despite a normal mitochondrial respiratory capacity, NE-induced lipolysis is abrogated in the interscapular brown adipose tissue (IBAT) of these mice. This lipolytic constraint is accompanied by a dramatic blunting (∼70%) of the in vivo thermal response to NE. Thus, in the presence of perilipin, PKA-mediated perilipin phosphorylation is essential for NE-dependent lipolysis and full adaptive thermogenesis in BAT. In IBAT of Peri KO mice, increased basal lipolysis attributable to the absence of perilipin is sufficient to support a rapid NE-stimulated temperature increase (∼3.0°C) comparable to that in wild-type mice. This observation suggests that one or more NE-dependent mechanism downstream of perilipin phosphorylation is required to initiate and/or sustain the IBAT thermal response
Fossilized skin reveals coevolution with feathers and metabolism in feathered dinosaurs and early birds
Feathers are remarkable evolutionary innovations that are associated with complex adaptations of the skin in modern birds. Fossilised feathers in non-avian dinosaurs and basal birds provide insights into feather evolution, but how associated integumentary adaptations evolved is unclear. Here we report the discovery of fossil skin, preserved with remarkable nanoscale fidelity, in three non-avian maniraptoran dinosaurs and a basal bird from the Cretaceous Jehol biota (China). The skin comprises patches of desquamating epidermal corneocytes that preserve a cytoskeletal array of helically coiled α-keratin tonofibrils. This structure confirms that basal birds and non-avian dinosaurs shed small epidermal flakes as in modern mammals and birds, but structural differences imply that these Cretaceous taxa had lower body heat production than modern birds. Feathered epidermis acquired many, but not all, anatomically modern attributes close to the base of the Maniraptora by the Middle Jurassic
Exposure to NO2, CO, and PM2.5 is linked to regional DNA methylation differences in asthma.
Background:DNA methylation of CpG sites on genetic loci has been linked to increased risk of asthma in children exposed to elevated ambient air pollutants (AAPs). Further identification of specific CpG sites and the pollutants that are associated with methylation of these CpG sites in immune cells could impact our understanding of asthma pathophysiology. In this study, we sought to identify some CpG sites in specific genes that could be associated with asthma regulation (Foxp3 and IL10) and to identify the different AAPs for which exposure prior to the blood draw is linked to methylation levels at these sites. We recruited subjects from Fresno, California, an area known for high levels of AAPs. Blood samples and responses to questionnaires were obtained (n = 188), and in a subset of subjects (n = 33), repeat samples were collected 2 years later. Average measures of AAPs were obtained for 1, 15, 30, 90, 180, and 365 days prior to each blood draw to estimate the short-term vs. long-term effects of the AAP exposures. Results:Asthma was significantly associated with higher differentially methylated regions (DMRs) of the Foxp3 promoter region (p = 0.030) and the IL10 intronic region (p = 0.026). Additionally, at the 90-day time period (90 days prior to the blood draw), Foxp3 methylation was positively associated with NO2, CO, and PM2.5 exposures (p = 0.001, p = 0.001, and p = 0.012, respectively). In the subset of subjects retested 2 years later (n = 33), a positive association between AAP exposure and methylation was sustained. There was also a negative correlation between the average Foxp3 methylation of the promoter region and activated Treg levels (p = 0.039) and a positive correlation between the average IL10 methylation of region 3 of intron 4 and IL10 cytokine expression (p = 0.030). Conclusions:Short-term and long-term exposures to high levels of CO, NO2, and PM2.5 were associated with alterations in differentially methylated regions of Foxp3. IL10 methylation showed a similar trend. For any given individual, these changes tend to be sustained over time. In addition, asthma was associated with higher differentially methylated regions of Foxp3 and IL10
1, 2-Bis (phenylsulfonyl)-1H-Indole as an Acceptor of Organocuprate Nucleophiles
1,2-Bis(phenylsulfonyl)-1H-indole is a novel example of an electron-deficient indole that undergoes nucleophilic attack at C-3. Though a variety of other organometallic nucleophiles fail to engender nucleophilic substitution, organocuprates produce 3-substituted 2-(phenylsulfonyl)-1H-indoles. These reactions contribute to the growing number of examples of nucleophilic addition to the indole core
The UTMOST: A hybrid digital signal processor transforms the MOST
The Molonglo Observatory Synthesis Telescope (MOST) is an 18,000 square meter
radio telescope situated some 40 km from the city of Canberra, Australia. Its
operating band (820-850 MHz) is now partly allocated to mobile phone
communications, making radio astronomy challenging. We describe how the
deployment of new digital receivers (RX boxes), Field Programmable Gate Array
(FPGA) based filterbanks and server-class computers equipped with 43 GPUs
(Graphics Processing Units) has transformed MOST into a versatile new
instrument (the UTMOST) for studying the dynamic radio sky on millisecond
timescales, ideal for work on pulsars and Fast Radio Bursts (FRBs). The
filterbanks, servers and their high-speed, low-latency network form part of a
hybrid solution to the observatory's signal processing requirements. The
emphasis on software and commodity off-the-shelf hardware has enabled rapid
deployment through the re-use of proven 'software backends' for its signal
processing. The new receivers have ten times the bandwidth of the original MOST
and double the sampling of the line feed, which doubles the field of view. The
UTMOST can simultaneously excise interference, make maps, coherently dedisperse
pulsars, and perform real-time searches of coherent fan beams for dispersed
single pulses. Although system performance is still sub-optimal, a pulsar
timing and FRB search programme has commenced and the first UTMOST maps have
been made. The telescope operates as a robotic facility, deciding how to
efficiently target pulsars and how long to stay on source, via feedback from
real-time pulsar folding. The regular timing of over 300 pulsars has resulted
in the discovery of 7 pulsar glitches and 3 FRBs. The UTMOST demonstrates that
if sufficient signal processing can be applied to the voltage streams it is
possible to perform innovative radio science in hostile radio frequency
environments.Comment: 12 pages, 6 figure
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