756 research outputs found
Toward an understanding of the chemical ecology of alternative reproductive tactics in the bulb mite (Rhizoglyphus robini)
Under strong sexual selection, certain species evolve distinct intrasexual, alternative reproductive tactics (ARTs). In many cases, ARTs can be viewed as environmentally-cued threshold traits, such that ARTs coexist if their relative fitness alternates over the environmental cue gradient. Surprisingly, the chemical ecology of ARTs has been underexplored in this context. To our knowledge, no prior study has directly quantified pheromone production for ARTs in a male-polymorphic species. Here, we used the bulb miteâin which males are either armed fighters that kill conspecifics, or unarmed scramblers (which have occasionally been observed to induce mating behavior in other males)âas a model system to gain insight into the role of pheromones in the evolutionary maintenance of ARTs. Given that scramblers forgo investment into weaponry, we tested whether scramblers produce higher quantities of the putative female sex-pheromone Îą-acaridial than fighters, which would improve the fitness of the scrambler phenotype through female mimicry by allowing avoidance of aggression from competitors. To this end, we sampled mites from a rich and a poor nutritional environment and quantified their production of Îą-acaridial through gas chromatography analysis.Environmental Biolog
Anomalous magnetotransport in (YGd)Co alloys: interplay of disorder and itinerant metamagnetism
New mechanism of magnetoresistivity in itinerant metamagnets with a
structural disorder is introduced basing on analysis of experimental results on
magnetoresistivity, susceptibility, and magnetization of structurally
disordered alloys (YGd)Co. In this series, YCo is an
enhanced Pauli paramagnet, whereas GdCo is a ferrimagnet (T=400
K) with Gd sublattice coupled antiferromagnetically to the itinerant Co-3d
electrons. The alloys are paramagnetic for . Large positive
magnetoresistivity has been observed in the alloys with magnetic ground state
at temperatures TT. We show that this unusual feature is linked to
a combination of structural disorder and metamagnetic instability of itinerant
Co-3d electrons. This new mechanism of the magnetoresistivity is common for a
broad class of materials featuring a static magnetic disorder and itinerant
metamagnetism.Comment: 7 pages 7 figure
Ultra-cold atoms in an optical cavity: two-mode laser locking to the cavity avoiding radiation pressure
The combination of ultra-cold atomic clouds with the light fields of optical
cavities provides a powerful model system for the development of new types of
laser cooling and for studying cooperative phenomena. These experiments
critically depend on the precise tuning of an incident pump laser with respect
to a cavity resonance. Here, we present a simple and reliable experimental
tuning scheme based on a two-mode laser spectrometer. The scheme uses a first
laser for probing higher-order transversal modes of the cavity having an
intensity minimum near the cavity's optical axis, where the atoms are confined
by a magnetic trap. In this way the cavity resonance is observed without
exposing the atoms to unwanted radiation pressure. A second laser, which is
phase-locked to the first one and tuned close to a fundamental cavity mode
drives the coherent atom-field dynamics.Comment: 7 pages, 7 figure
Magnetic phases of skyrmion-hosting GaV4S8âySey (y = 0, 2, 4, 8) probed with muon spectroscopy
We present the results of a muon-spin spectroscopy investigation of GaV4S8âySey with y = 0, 2, 4, and 8. Zero-field measurements suggest that GaV4Se8 and GaV4S8 have distinct magnetic ground states, with the latter material showing an anomalous temperature dependence of the local magnetic field. It is not possible to evolve the magnetic state continuously between these two systems, with the intermediate y = 2 and 4 materials showing glassy magnetic behavior at low temperature. The skyrmion lattice (SkL) phase is evident in the y = 0 and 8 materials through an enhanced response of the muon-spin relaxation to the emergent dynamics that accompany the SkL. For our polycrystalline samples of GaV4Se8, this enhanced dynamic response is confined to a smaller region of the magnetic field-temperature phase diagram than the previous reports of the SkL in single crystals
Primeval Corrections to the CMB Anisotropies
We show that deviations of the quantum state of the inflaton from the thermal
vacuum of inflation may leave an imprint in the CMB anisotropies. The quantum
dynamics of the inflaton in such a state produces corrections to the
inflationary fluctuations, which may be observable. Because these effects
originate from IR physics below the Planck scale, they will dominate over any
trans-Planckian imprints in any theory which obeys decoupling. Inflation sweeps
away these initial deviations and forces its quantum state closer to the
thermal vacuum. We view this as the quantum version of the cosmic no-hair
theorem. Such imprints in the CMB may be a useful, independent test of the
duration of inflation, or of significant features in the inflaton potential
about 60 e-folds before inflation ended, instead of an unlikely discovery of
the signatures of quantum gravity. The absence of any such substructure would
suggest that inflation lasted uninterrupted much longer than
e-folds.Comment: 17 pages, latex, no figures; v3: added references and comments, final
version to appear in Phys. Rev.
Cosmological parameter estimation and the inflationary cosmology
We consider approaches to cosmological parameter estimation in the
inflationary cosmology, focussing on the required accuracy of the initial power
spectra. Parametrizing the spectra, for example by power-laws, is well suited
to testing the inflationary paradigm but will only correctly estimate
cosmological parameters if the parametrization is sufficiently accurate, and we
investigate conditions under which this is achieved both for present data and
for upcoming satellite data. If inflation is favoured, reliable estimation of
its physical parameters requires an alternative approach adopting its detailed
predictions. For slow-roll inflation, we investigate the accuracy of the
predicted spectra at first and second order in the slow-roll expansion
(presenting the complete second-order corrections for the tensors for the first
time). We find that within the presently-allowed parameter space, there are
regions where it will be necessary to include second-order corrections to reach
the accuracy requirements of MAP and Planck satellite data. We end by proposing
a data analysis pipeline appropriate for testing inflation and for cosmological
parameter estimation from high-precision data.Comment: 15 pages RevTeX file with figures incorporated. Slow-roll inflation
module for use with the CAMB program can be found at
http://astronomy.cpes.susx.ac.uk/~sleach/inflation/ This version corrects a
typo in the definition of z_S (after Eq.1) and supersedes the journal versio
Synthesis and magnetic properties of NiFe_{2-x}Al_{x}O_{4} nanoparticles
Nanocrystalline Al-doped nickel ferrite powders have been synthesized by
sol-gel auto-ignition method and the effect of non-magnetic aluminum content on
the structural and magnetic properties has been studied. The X-ray diffraction
(XRD) revealed that the powders obtained are single phase with inverse spinel
structure. The calculated grain sizes from XRD data have been verified using
transmission electron microscopy (TEM). TEM photographs show that the powders
consist of nanometer-sized grains. It was observed that the characteristic
grain size decreases from 29 to 6 nm as the non-magnetic Al content increases,
which was attributed to the influence of non-magnetic Al concentration on the
grain size. Magnetic hysteresis loops were measured at room temperature with a
maximum applied magnetic field of 1T. As aluminum content increases, the
measured magnetic hysteresis curves become more and more narrow and the
saturation magnetization and remanent magnetization both decreased. The
reduction of agnetization compared to bulk is a consequence of spin
non-collinearity. Further reduction of magnetization with increase of aluminum
content is caused by non-magnetic Al^{3+} ions and weakened interaction between
sublattices. This, as well as the decrease in hysteresis was understood in
terms of the decrease in particle size.Comment: 24 pages, 6 figure
DNA methylation GrimAge strongly predicts lifespan and healthspan
It was unknown whether plasma protein levels can be estimated based on DNA methylation (DNAm) levels, and if so, how the resulting surrogates can be consolidated into a powerful predictor of lifespan. We present here, seven DNAm-based estimators of plasma proteins including those of plasminogen activator inhibitor 1 (PAI-1) and growth differentiation factor 15. The resulting predictor of lifespan, DNAm GrimAge (in units of years), is a composite biomarker based on the seven DNAm surrogates and a DNAm-based estimator of smoking packyears. Adjusting DNAm GrimAge for chronological age generated novel measure of epigenetic age acceleration, AgeAccelGrim. Using large scale validation data from thousands of individuals, we demonstrate that DNAm GrimAge stands out among existing epigenetic clocks in terms of its predictive ability for time-to-death (Cox regression P=2.0E- 75), time-to-coronary heart disease (P=6.2E-24), time-to-cancer (P= 1.3E-12), its strong relationship with computed tomography data for fatty liver/excess visceral fat, and age-at-menopause (P=1.6E-12). AgeAccelGrim is strongly associated with a host of age-related conditions including comorbidity count (P=3.45E- 17). Similarly, age-adjusted DNAm PAI-1 levels are associated with lifespan (P=5.4E-28), comorbidity count (P= 7.3E-56) and type 2 diabetes (P=2.0E-26). These DNAm-based biomarkers show the expected relationship with lifestyle factors including healthy diet and educational attainment. Overall, these epigenetic biomarkers are expected to find many applications including human anti-aging studies
A synopsis of the Ordovician System in its birthplace - Britain and Ireland
Rock successions in Britain and Ireland, and more especially those in North Wales, were instrumental in the founding and naming of the Ordovician System, and the Anglo-Welsh series established both initially and subsequently were used widely as a standard for Ordovician chronostratigraphy. Although now largely superseded in the global scheme of series and stages, they retain their local and regional importance. The Ordovician System in Britain and Ireland documents the history of a segment of the Earth's crust that incorporated opposing peri-Gondwanan and peri-Laurentian/Laurentian margins of the Iapetus Ocean during its closure, and is accordingly complex. The complexity arises from the volcanic and tectonic processes that accompanied oceanic closure coupled with the effects of eustatic sea-level changes, including the far-field effects of the Late Ordovician glaciation. For the past three decades, Ordovician successions in Britain and Ireland have been discussed in terms of terranes. Here we review Ordovician successions in each terrane, incorporating the results of recent research and correlating those successions via biostratigraphical schemes and radiometric dates to the global Ordovician series and stages
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in âs = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fbâ1 of protonâproton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
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