Interpreting radiative efficiency in radio-loud AGNs

Author submitted version of unrefereed Nature Astronomy comment. Version in journal format available at https://rdcu.be/KH6WRadiative efficiency in radio-loud active galactic nuclei is governed by the accretion rate onto the central black hole rather than directly by the type of accreted matter; while it correlates with real differences in host galaxies and environments, it does not provide unambiguous information about particular objects.Non peer reviewedFinal Accepted Versio

Recent results from systematic parameterizations of Ginsparg-Wilson fermions

The Fixed Point Dirac Operator and Chirally Improved Fermions both use large numbers of gauge paths and the full Dirac structure to approximate a solution of the Ginsparg-Wilson equation. After a brief review of the two approaches we present recent results for quenched QCD with pion masses down to 210 MeV. We discuss the limits and advantages of approximate parameterizations and outline future perspectives.Comment: Lattice2002(plenary). References and Fig. 5 updated. Final version submitted to the proceeding

Quenched QCD with fixed-point and chirally improved fermion

In this contribution we present results from quenched QCD simulations with the parameterized fixed-point (FP) and the chirally improved (CI) Dirac operator. Both these operators are approximate solutions of the Ginsparg-Wilson equation and have good chiral properties. We focus our discussion on observables sensitive to chirality. In particular we explore pion masses down to 210 MeV in light hadron spectroscopy, quenched chiral logs, the pion decay constant and the pion scattering length. We discuss finite volume effects, scaling properties of the FP and CI operators and performance issues in their numerical implementation.Comment: Lattice2002(chiral), 17 pages, 21 figures, (LaTeX style file espcrc2.sty and AMS style files

The writing on the wall: the concealed communities of the East Yorkshire horselads

This paper examines the graffiti found within late nineteenth and early-twentieth century farm buildings in the Wolds of East Yorkshire. It suggests that the graffiti were created by a group of young men at the bottom of the social hierarchy - the horselads – and was one of the ways in which they constructed a distinctive sense of communal identity, at a particular stage in their lives. Whilst it tells us much about changing agricultural regimes and social structures, it also informs us about experiences and attitudes often hidden from official histories and biographies. In this way, the graffiti are argued to inform our understanding, not only of a concealed community, but also about their hidden histor

Higher sociability leads to lower reproductive success in female kangaroos

In social mammals, social integration is generally assumed to improve females' reproductive success. Most species demonstrating this relationship exhibit complex forms of social bonds and interactions. However, female eastern grey kangaroos (Macropus giganteus) exhibit differentiated social relationships, yet do not appear to cooperate directly. It is unclear what the fitness consequences of such sociability could be in species that do not exhibit obvious forms of cooperation. Using 4 years of life history, spatial and social data from a wild population of approximately 200 individually recognizable female eastern grey kangaroos, we tested whether higher levels of sociability are associated with greater reproductive success. Contrary to expectations, we found that the size of a female's social network, her numbers of preferential associations with other females and her group sizes all negatively influenced her reproductive success. These factors influenced the survival of dependent young that had left the pouch rather than those that were still in the pouch. We also show that primiparous females (first-time breeders) were less likely to have surviving young. Our findings suggest that social bonds are not always beneficial for reproductive success in group-living species, and that female kangaroos may experience trade-offs between successfully rearing young and maintaining affiliative relationships

Higher sociability leads to lower reproductive success in female kangaroos: Sociability and fitness in kangaroos

In social mammals, social integration is generally assumed to improve females’ reproductive success. Most species demonstrating this relationship exhibit complex forms of social bonds and interactions. However, female eastern grey kangaroos (Macropus giganteus) exhibit differentiated social relationships, yet do not appear to cooperate directly. It is unclear what the fitness consequences of such sociability could be in species that do not exhibit obvious forms of cooperation. Using 4 years of life history, spatial and social data from a wild population of approximately 200 individually recognizable female eastern grey kangaroos, we tested whether higher levels of sociability are associated with greater reproductive success. Contrary to expectations, we found that the size of a female’s social network, her numbers of preferential associations with other females and her group sizes all negatively influenced her reproductive success. These factors influenced the survival of dependent young that had left the pouch rather than those that were still in the pouch. We also show that primiparous females (first-time breeders) were less likely to have surviving young. Our findings suggest that social bonds are not always beneficial for reproductive success in group-living species, and that female kangaroos may experience trade-offs between successfully rearing young and maintaining affiliative relationships

Tubulin Binds to the Cytoplasmic Loop of TRESK Background K+ Channel In Vitro.

The cytoplasmic loop between the second and third transmembrane segments is pivotal in the regulation of TRESK (TWIK-related spinal cord K+ channel, K2P18.1, KCNK18). Calcineurin binds to this region and activates the channel by dephosphorylation in response to the calcium signal. Phosphorylation-dependent anchorage of 14-3-3 adaptor protein also modulates TRESK at this location. In the present study, we identified molecular interacting partners of the intracellular loop. By an affinity chromatography approach using the cytoplasmic loop as bait, we have verified the specific association of calcineurin and 14-3-3 to the channel. In addition to these known interacting proteins, we observed substantial binding of tubulin to the intracellular loop. Successive truncation of the polypeptide and pull-down experiments from mouse brain cytosol narrowed down the region sufficient for the binding of tubulin to a 16 amino acid sequence: LVLGRLSYSIISNLDE. The first six residues of this sequence are similar to the previously reported tubulin-binding region of P2X2 purinergic receptor. The tubulin-binding site of TRESK is located close to the protein kinase A (PKA)-dependent 14-3-3-docking motif of the channel. We provide experimental evidence suggesting that 14-3-3 competes with tubulin for the binding to the cytoplasmic loop of TRESK. It is intriguing that the 16 amino acid tubulin-binding sequence includes the serines, which were previously shown to be phosphorylated by microtubule-affinity regulating kinases (MARK kinases) and contribute to channel inhibition. Although tubulin binds to TRESK in vitro, it remains to be established whether the two proteins also interact in the living cell

A biophysical model of endocannabinoid-mediated short term depression in hippocampal inhibition

Memories are believed to be represented in the synaptic pathways of vastly interconnected networks of neurons. The plasticity of synapses, that is, their strengthening and weakening depending on neuronal activity, is believed to be the basis of learning and establishing memories. An increasing number of studies indicate that endocannabinoids have a widespread action on brain function through modulation of synap–tic transmission and plasticity. Recent experimental studies have characterised the role of endocannabinoids in mediating both short- and long-term synaptic plasticity in various brain regions including the hippocampus, a brain region strongly associated with cognitive functions, such as learning and memory. Here, we present a biophysically plausible model of cannabinoid retrograde signalling at the synaptic level and investigate how this signalling mediates depolarisation induced suppression of inhibition (DSI), a prominent form of shortterm synaptic depression in inhibitory transmission in hippocampus. The model successfully captures many of the key characteristics of DSI in the hippocampus, as observed experimentally, with a minimal yet sufficient mathematical description of the major signalling molecules and cascades involved. More specifically, this model serves as a framework to test hypotheses on the factors determining the variability of DSI and investigate under which conditions it can be evoked. The model reveals the frequency and duration bands in which the post-synaptic cell can be sufficiently stimulated to elicit DSI. Moreover, the model provides key insights on how the state of the inhibitory cell modulates DSI according to its firing rate and relative timing to the post-synaptic activation. Thus, it provides concrete suggestions to further investigate experimentally how DSI modulates and is modulated by neuronal activity in the brain. Importantly, this model serves as a stepping stone for future deciphering of the role of endocannabinoids in synaptic transmission as a feedback mechanism both at synaptic and network level

Mechanisms of decadal variability in the Labrador Sea and the wider North Atlantic in a high-resolution climate model

A necessary step before assessing the performance of decadal predictions is the evaluation of the processes that bring memory to the climate system, both in climate models and observations. These mechanisms are particularly relevant in the North Atlantic, where the ocean circulation, related to both the Subpolar Gyre and the Meridional Overturning Circulation (AMOC), is thought to be important for driving significant heat content anomalies. Recently, a rapid decline in observed densities in the deep Labrador Sea has pointed to an ongoing slowdown of the AMOC strength taking place since the mid 90s, a decline also hinted by in-situ observations from the RAPID array. This study explores the use of Labrador Sea densities as a precursor of the ocean circulation changes, by analysing a 300-year long simulation with the state-of-the-art coupled model HadGEM3-GC2. The major drivers of Labrador Sea density variability are investigated, and are characterised by three major contributions. First, the integrated effect of local surface heat fluxes, mainly driven by year-to-year changes in the North Atlantic Oscillation, which accounts for 62% of the total variance. Additionally, two multidecadal-to-centennial contributions from the Greenland-Scotland Ridge outflows are quantified; the first associated with freshwater exports via the East Greenland Current, and the second with density changes in the Denmark Strait Overflow. Finally, evidence is shown that decadal trends in Labrador Sea densities are followed by important atmospheric impacts. In particular, a negative winter NAO response appears to follow the positive Labrador Sea density trends, and provides a phase reversal mechanism

Search for rare quark-annihilation decays, B --> Ds(*) Phi

We report on searches for B- --> Ds- Phi and B- --> Ds*- Phi. In the context of the Standard Model, these decays are expected to be highly suppressed since they proceed through annihilation of the b and u-bar quarks in the B- meson. Our results are based on 234 million Upsilon(4S) --> B Bbar decays collected with the BABAR detector at SLAC. We find no evidence for these decays, and we set Bayesian 90% confidence level upper limits on the branching fractions BF(B- --> Ds- Phi) Ds*- Phi)<1.2x10^(-5). These results are consistent with Standard Model expectations.Comment: 8 pages, 3 postscript figues, submitted to Phys. Rev. D (Rapid Communications