136 research outputs found
Quantifying variation in δ13C and δ15N isotopes within and between feathers and individuals : is one sample enough?
This study represents a contribution to the ecosystems component of the British Antarctic Survey Polar Science for Planet Earth Programme, funded by The Natural Environment Research Council and through a NERC standard grant NE/I02237X/1.Studies of avian migration increasingly use stable isotope analysis to provide vital trophic and spatial markers. However, when interpreting differences in stable isotope values of feathers, many studies are forced to make assumptions about the timing of moult. A fundamental question remains about the consistency of these values within and between feathers from the same individual. In this study, we examine variation in carbon and nitrogen isotopes by sub-sampling feathers collected from the wings of adults of two small congeneric petrel species, the broad-billed Pachyptila vittata and Antarctic prion P. desolata. Broad-billed prion feather vane material was enriched in 15N compared to feather rachis material, but there was no detectable difference in δ13C. Comparison of multiple samples taken from Antarctic prion feathers indicated subtle difference in isotopes; rachis material was enriched in 13C compared to vane material, and there were differences along the length of the feather, with samples from the middle and tip of the feather depleted in 15N compared to those from the base. While the greatest proportion of model variance was explained by differences between feathers and individuals, the magnitude of these within-feather differences was up to 0.5 ‰ in δ15N and 0.8 ‰ in δ13C. We discuss the potential drivers of these differences, linking isotopic variation to individual-level dietary differences, movement patterns and temporal dietary shifts. A novel result is that within-feather differences in δ13C may be attributed to differences in keratin structure within feathers, suggesting further work is required to understand the role of different amino acids. Our results highlight the importance of multiple sampling regimes that consider both within- and between-feather variation in studies using stable isotopes.Publisher PDFPeer reviewe
Rapid Exchange Cooling with Trapped Ions
The trapped-ion quantum charge-coupled device (QCCD) architecture is a
leading candidate for advanced quantum information processing. In current QCCD
implementations, imperfect ion transport and anomalous heating can excite ion
motion during a calculation. To counteract this, intermediate cooling is
necessary to maintain high-fidelity gate performance. Cooling the computational
ions sympathetically with ions of another species, a commonly employed
strategy, creates a significant runtime bottleneck. Here, we demonstrate a
different approach we call exchange cooling. Unlike sympathetic cooling,
exchange cooling does not require trapping two different atomic species. The
protocol introduces a bank of coolant ions which are repeatedly laser
cooled. A computational ion can then be cooled by transporting a coolant ion
into its proximity. We test this concept experimentally with two ions,
executing the necessary transport in 107 , an order of magnitude faster
than typical sympathetic cooling durations. We remove over 96%, and as many as
102(5) quanta, of axial motional energy from the computational ion. We verify
that re-cooling the coolant ion does not decohere the computational ion. This
approach validates the feasibility of a single-species QCCD processor, capable
of fast quantum simulation and computation
Coherent two-dimensional Fourier transform spectroscopy using a 25 Tesla resistive magnet.
We performed nonlinear optical two-dimensional Fourier transform spectroscopy measurements using an optical resistive high-field magnet on GaAs quantum wells. Magnetic fields up to 25 T can be achieved using the split helix resistive magnet. Two-dimensional spectroscopy measurements based on the coherent four-wave mixing signal require phase stability. Therefore, these measurements are difficult to perform in environments prone to mechanical vibrations. Large resistive magnets use extensive quantities of cooling water, which causes mechanical vibrations, making two-dimensional Fourier transform spectroscopy very challenging. Here, we report on the strategies we used to overcome these challenges and maintain the required phase-stability throughout the measurement. A self-contained portable platform was used to set up the experiments within the time frame provided by a user facility. Furthermore, this platform was floated above the optical table in order to isolate it from vibrations originating from the resistive magnet. Finally, we present two-dimensional Fourier transform spectra obtained from GaAs quantum wells at magnetic fields up to 25 T and demonstrate the utility of this technique in providing important details, which are obscured in one dimensional spectroscopy
The invisible plan: how English teachers develop their expertise and the special place of adapting the skills of lesson planning
This paper analyses how English teachers learn to become expert designers of learning and why sharing that expertise is increasingly vital. Its conceptual framework is the widely recognised, empirically tested, five-stage developmental Dreyfus model of skill acquisition, exemplifying the development of teacher expertise, constituted by the “milestone” [m] and “transitory” [t] phases connecting with the five stages of: Novice [m], Advanced Beginner [t], Competent [m], Proficient [t] and Expert [m]. Teacher planning is analysed as one key tacit or non-tangible component of developing expertise. Focusing specifically on English teachers as key participants in this pioneer teacher cognition study, the defining characteristics of milestone stages of expertise development are explored with specific attention to the remarkably under-researched area of planning. We introduce three new categories, defining modes of planning: (i) visible practical planning, (ii) external reflective planning and (iii) internal reflective planning, demonstrating their role in teacher development through the Dreyfus five stages. English is a subject which suffers from frequent disruptive changes to curriculum and assessment: new learning designs are constantly demanded, making planning an ongoing challenge. The implications for practice include the importance of an explicit understanding of how teachers’ planning moves through the three phases from the very “visible” novice phase to the internal relatively “automatic” competent teacher and finally the seemingly “invisible” expert phase. Further research is needed to explore how English teachers can share planning expertise between the three phases to improve teachers’ skills and student learning
SN 2021hpr and its two siblings in the Cepheid calibrator galaxy NGC 3147: A hierarchical BayeSN analysis of a Type Ia supernova trio, and a Hubble constant constraint
To improve Type Ia supernova (SN Ia) standardisability, the consistency of
distance estimates to siblings -- SNe in the same host galaxy -- should be
investigated. We present Young Supernova Experiment Pan-STARRS-1
photometry of SN 2021hpr, the third spectroscopically confirmed SN Ia in the
high-stellar-mass Cepheid-calibrator galaxy NGC 3147. We analyse NGC 3147's
trio of SN Ia siblings: SNe 1997bq, 2008fv and 2021hpr, using a new version of
the BayeSN model of SN Ia spectral-energy distributions, retrained
simultaneously using optical-NIR (0.35--1.8 m) data. The
distance estimates to each sibling are consistent, with a sample standard
deviation 0.01 mag, much smaller than the total intrinsic scatter in
the training sample: mag. Fitting normal SN Ia siblings
in three additional galaxies, we estimate a 90% probability that the
siblings' intrinsic scatter is smaller than . We build a new
hierarchical model that fits light curves of siblings in a single galaxy
simultaneously; this yields more precise estimates of the common distance and
the dust parameters. Fitting the trio for a common dust law shape yields
. Our work motivates future hierarchical modelling of more
siblings, to tightly constrain their intrinsic scatter, and better understand
SN-host correlations. Finally, we estimate the Hubble constant, using a Cepheid
distance to NGC 3147, the siblings trio, and 109 Hubble flow () SNe Ia; marginalising over the siblings' and population's
intrinsic scatters, and the peculiar velocity dispersion, yields
.Comment: Submitted to MNRAS; 30 pages, 22 figure
Flight of the Bumblebee: the Early Excess Flux of Type Ia Supernova 2023bee revealed by , and Young Supernova Experiment Observations
We present high-cadence ultraviolet through near-infrared observations of the
Type Ia supernova (SN Ia) 2023bee in NGC~2708 ( Mpc), finding
excess flux in the first days after explosion relative to the expected
power-law rise from an expanding fireball. This deviation from typical behavior
for SNe Ia is particularly obvious in our 10-minute cadence light curve
and UV data. Compared to a few other normal SNe Ia with detected early
excess flux, the excess flux in SN 2023bee is redder in the UV and less
luminous. We present optical spectra of SN 2023bee, including two spectra
during the period where the flux excess is dominant. At this time, the spectra
are similar to those of other SNe Ia but with weaker Si II, C II and Ca II
absorption lines, perhaps because the excess flux creates a stronger continuum.
We compare the data to several theoretical models that have been proposed to
explain the early flux excess in SNe Ia. Interaction with either a nearby
companion star or close-in circumstellar material is expected to produce a
faster evolution than seen in the data. Radioactive material in the outer
layers of the ejecta, either from a double detonation explosion or simply an
explosion with a Ni clump near the surface, can not fully reproduce the
evolution either, likely due to the sensitivity of early UV observable to the
treatment of the outer part of ejecta in simulation. We conclude that no
current model can adequately explain the full set of observations. We find that
a relatively large fraction of nearby, bright SNe Ia with high-cadence
observations have some amount of excess flux within a few days of explosion.
Considering potential asymmetric emission, the physical cause of this excess
flux may be ubiquitous in normal SNe Ia.Comment: 21 pages, 12 figures. Accepted by the astrophysical journa
Recruiting men from across the socioeconomic spectrum via GP registers and community outreach to a weight management feasibility randomised controlled trial
Background
Men, particularly those living in disadvantaged areas, are less likely to participate in weight management programmes than women despite similar levels of excess weight. Little is known about how best to recruit men to weight management interventions. This paper describes patient and public involvement in pre-trial decisions relevant to recruitment and aims to report on recruitment to the subsequent men-only weight management feasibility trial, including the: i) acceptability and feasibility of recruitment; and ii) baseline sample characteristics by recruitment strategy.
Methods
Men with BMI ≥30 kg/m2 and/or waist circumference ≥ 40 in. were recruited to the feasibility trial via two strategies; community outreach (venue information stands and word of mouth) and GP letters, targeting disadvantaged areas. Recruitment activities (e.g. letters sent, researcher venue hours) were recorded systematically, and baseline characteristics questionnaire data collated. Qualitative interviews (n = 50) were conducted three months post-recruitment. Analyses and reporting followed a complementary mixed methods approach.
Results
105 men were recruited within four months (community n = 60, GP letter n = 45). Community outreach took 2.3 recruiter hours per participant and GP letters had an opt-in rate of 10.2% (n = 90/879). More men were interested than could be accommodated. Most participants (60%) lived in more disadvantaged areas. Compared to community outreach, men recruited via GP letters were older (mean = 57 vs 48 years); more likely to report an obesity-related co-morbidity (87% vs 44%); and less educated (no formal qualifications, 32% vs 10%, degree educated 11% vs 41%). Recruitment strategies were acceptable, a sensitive approach and trusting relationships with recruiters valued, and the ‘catchy’ study name drew attention.
Conclusions
Targeted community outreach and GP letters were acceptable strategies that successfully recruited participants to a men-only weight management feasibility trial. Both strategies engaged men from disadvantaged areas, a typically underserved population. Using two recruitment strategies produced samples with different health risk profiles, which could add value to research where either primary or secondary prevention is of interest. Further work is required to examine how these strategies could be implemented and sustained in practice
SN 2022oqm: A Multi-peaked Calcium-rich Transient from a White Dwarf Binary Progenitor System
We present the photometric and spectroscopic evolution of SN 2022oqm, a
nearby multi-peaked hydrogen- and helium-weak calcium-rich transient (CaRT). SN
2022oqm was detected 19.9 kpc from its host galaxy, the face-on spiral galaxy
NGC 5875. Extensive spectroscopic coverage reveals a hot (T >= 40,000 K)
continuum and carbon features observed ~1 day after discovery, SN Ic-like
photospheric-phase spectra, and strong forbidden calcium emission starting 38
days after discovery. SN 2022oqm has a relatively high peak luminosity (MB =
-17 mag) for CaRTs, making it an outlier in the population. We determine that
three power sources are necessary to explain SN 2022oqm's light curve, with
each power source corresponding to a distinct peak in its light curve. The
first peak of the light curve is powered by an expanding blackbody with a power
law luminosity, consistent with shock cooling by circumstellar material.
Subsequent peaks are powered by a double radioactive decay model, consistent
with two separate sources of photons diffusing through an optically thick
ejecta. From the optical light curve, we derive an ejecta mass and 56Ni mass of
~0.89 solar masses and ~0.09 solar masses, respectively. Detailed spectroscopic
modeling reveals ejecta that is dominated by intermediate-mass elements, with
signs that Fe-peak elements have been well-mixed. We discuss several physical
origins for SN 2022oqm and favor a white dwarf progenitor model. The inferred
ejecta mass points to a surprisingly massive white dwarf, challenging models of
CaRT progenitors.Comment: 33 pages, 17 figures, 5 tables, Submitted to Ap
Flight of the bumblebee : the early excess flux of Type Ia supernova 2023bee revealed by TESS, Swift, and Young Supernova Experiment observations
We present high-cadence ultraviolet through near-infrared observations of the Type Ia supernova (SN Ia) 2023bee at D = 32 ± 3 Mpc, finding excess flux in the first days after explosion, particularly in our 10 minutes cadence TESS light curve and Swift UV data. Compared to a few other normal SNe Ia with early excess flux, the excess flux in SN 2023bee is redder in the UV and less luminous. We present optical spectra of SN 2023bee, including two spectra during the period where the flux excess is dominant. At this time, the spectra are similar to those of other SNe Ia but with weaker Si ii, C ii, and Ca ii absorption lines, perhaps because the excess flux creates a stronger continuum. We compare the data to several theoretical models on the origin of early excess flux in SNe Ia. Interaction with either the companion star or close-in circumstellar material is expected to produce a faster evolution than observed. Radioactive material in the outer layers of the ejecta, either from double detonation explosion or from a 56Ni clump near the surface, cannot fully reproduce the evolution either, likely due to the sensitivity of early UV observable to the treatment of the outer part of ejecta in simulation. We conclude that no current model can adequately explain the full set of observations. We find that a relatively large fraction of nearby, bright SNe Ia with high-cadence observations have some amount of excess flux within a few days of explosion. Considering potential asymmetric emission, the physical cause of this excess flux may be ubiquitous in normal SNe Ia
- …