244 research outputs found
Self-aligned nanoscale SQUID on a tip
A nanometer-sized superconducting quantum interference device (nanoSQUID) is
fabricated on the apex of a sharp quartz tip and integrated into a scanning
SQUID microscope. A simple self-aligned fabrication method results in
nanoSQUIDs with diameters down to 100 nm with no lithographic processing. An
aluminum nanoSQUID with an effective area of 0.034 m displays flux
sensitivity of 1.8 \mu_B/\mathrm{Hz}^{1/2}$ and high bandwidth, the SQUID on a tip is a highly
promising probe for nanoscale magnetic imaging and spectroscopy.Comment: 14 manuscript pages, 5 figure
Scintillation-limited photometry with the 20-cm NGTS telescopes at Paranal Observatory
Ground-based photometry of bright stars is expected to be limited by atmospheric scintillation, although in practice observations are often limited by other sources of systematic noise. We analyse 122 nights of bright star (Gmag ≲ 11.5) photometry using the 20-cm telescopes of the Next-Generation Transit Survey (NGTS) at the Paranal Observatory in Chile. We compare the noise properties to theoretical noise models and we demonstrate that NGTS photometry of bright stars is indeed limited by atmospheric scintillation. We determine a median scintillation coefficient at the Paranal Observatory of CY=1.54, which is in good agreement with previous results derived from turbulence profiling measurements at the observatory. We find that separate NGTS telescopes make consistent measurements of scintillation when simultaneously monitoring the same field. Using contemporaneous meteorological data, we find that higher wind speeds at the tropopause correlate with a decrease in long-exposure (t = 10 s) scintillation. Hence, the winter months between June and August provide the best conditions for high-precision photometry of bright stars at the Paranal Observatory. This work demonstrates that NGTS photometric data, collected for searching for exoplanets, contains within it a record of the scintillation conditions at Paranal
A study update newsletter or Post-it® note did not increase postal questionnaire response rates in a falls prevention trial: an embedded randomised factorial trial
Background: Participants not returning data collection questionnaires is a problem for many randomised controlled trials. The resultant loss of data leads to a reduction in statistical power and can result in bias. The aim of this study was to assess whether the use of a study update newsletter and/or a handwritten or printed Post-it® note sticker increased postal questionnaire response rates for participants of a randomised controlled trial. Method: This study was a factorial trial embedded within a host trial of a falls-prevention intervention among men and women aged ≥65 years under podiatric care. Participants were randomised into one of six groups: newsletter plus handwritten Post-it®; newsletter plus printed Post-it®; newsletter only; handwritten Post-it® only; printed Post-it® only; or no newsletter or Post-it®. The results were combined with those from previous embedded randomised controlled trials in meta-analyses. Results: The overall 12-month response rate was 803/826 (97.2%) (newsletter 95.1%, no newsletter 99.3%, printed Post-it® 97.5%, handwritten Post-it® 97.1%, no Post-it® 97.1%). The study update newsletter had a detrimental effect on response rates (adjusted odds ratio 0.14, 95% CI 0.04 to 0.48, p<0.01) and time to return the questionnaire (adjusted hazard ratio 0.86, 95% CI 0.75 to 0.99, p=0.04). No other statistically significant differences were observed between the intervention groups on response rates, time to response, and the need for a reminder. Conclusions: Post-it® notes have been shown to be ineffective in three embedded trials, whereas the evidence for newsletter reminders is still uncertain. Keywords Randomised controlled trial; randomisation; embedded trial; newsletter; Post-it® note; response rat
NGTS clusters survey -- II. White-light flares from the youngest stars in Orion
We present the detection of high energy white-light flares from pre-main
sequence stars associated with the Orion complex, observed as part of the Next
Generation Transit Survey (NGTS). With energies up to erg
these flares are some of the most energetic white-light flare events seen to
date. We have used the NGTS observations of flaring and non-flaring stars to
measure the average flare occurrence rate for 4 Myr M0-M3 stars. We have also
combined our results with those from previous studies to predict average rates
for flares above ergs for early M stars in nearby young
associations.STFC ST/M001962/1; ST/P000495/
Evaluation of Functional Erythropoietin Receptor Status in Skeletal Muscle In Vivo: Acute and Prolonged Studies in Healthy Human Subjects
BACKGROUND: Erythropoietin receptors have been identified in human skeletal muscle tissue, but downstream signal transduction has not been investigated. We therefore studied in vivo effects of systemic erythropoietin exposure in human skeletal muscle. METHODOLOGY/PRINCIPAL FINDINGS: The protocols involved 1) acute effects of a single bolus injection of erythropoietin followed by consecutive muscle biopsies for 1-10 hours, and 2) a separate study with prolonged administration for 16 days with biopsies obtained before and after. The presence of erythropoietin receptors in muscle tissue as well as activation of Epo signalling pathways (STAT5, MAPK, Akt, IKK) were analysed by western blotting. Changes in muscle protein profiles after prolonged erythropoietin treatment were evaluated by 2D gel-electrophoresis and mass spectrometry. The presence of the erythropoietin receptor in skeletal muscle was confirmed, by the M20 but not the C20 antibody. However, no significant changes in phosphorylation of the Epo-R, STAT5, MAPK, Akt, Lyn, IKK, and p70S6K after erythropoietin administration were detected. The level of 8 protein spots were significantly altered after 16 days of rHuEpo treatment; one isoform of myosin light chain 3 and one of desmin/actin were decreased, while three isoforms of creatine kinase and two of glyceraldehyd-3-phosphate dehydrogenase were increased. CONCLUSIONS/SIGNIFICANCE: Acute exposure to recombinant human erythropoietin is not associated by detectable activation of the Epo-R or downstream signalling targets in human skeletal muscle in the resting situation, whereas more prolonged exposure induces significant changes in the skeletal muscle proteome. The absence of functional Epo receptor activity in human skeletal muscle indicates that the long-term effects are indirect and probably related to an increased oxidative capacity in this tissue
NGTS-21b: An Inflated Super-Jupiter Orbiting a Metal-poor K dwarf
We report the discovery of NGTS-21b, a massive hot Jupiter orbiting a
low-mass star as part of the Next Generation Transit Survey (NGTS). The planet
has a mass and radius of M, and
R, and an orbital period of 1.543 days. The host is a K3V (, K) metal-poor (, dex) dwarf
star with a mass and radius of , M,and , R. Its age and rotation period of , Gyr
and , d respectively, are in accordance with the observed
moderately low stellar activity level. When comparing NGTS-21b with currently
known transiting hot Jupiters with similar equilibrium temperatures, it is
found to have one of the largest measured radii despite its large mass.
Inflation-free planetary structure models suggest the planet's atmosphere is
inflated by , while inflationary models predict a radius consistent
with observations, thus pointing to stellar irradiation as the probable origin
of NGTS-21b's radius inflation. Additionally, NGTS-21b's bulk density (, g/cm) is also amongst the largest within the population of
metal-poor giant hosts ([Fe/H] < 0.0), helping to reveal a falling upper
boundary in metallicity-planet density parameter space that is in concordance
with core accretion formation models. The discovery of rare planetary systems
such as NGTS-21 greatly contributes towards better constraints being placed on
the formation and evolution mechanisms of massive planets orbiting low-mass
stars.Comment: 12 pages, 13 figures, accepted for publication in MNRA
Aspirin versus placebo for the treatment of Venous Leg Ulcers – a phase II, pilot, randomised trial (AVURT).
Background
Venous leg ulcers (VLUs) can take many months to heal and 25% fail to heal. The main treatment for venous leg ulcers is compression therapy and few additional therapies exist. Two previous trials indicated that low-dose aspirin may improve healing time, but these trials were insufficiently robust.
Methods
A multi-centred, pilot, phase II, randomised, double blind, parallel-group, placebo-controlled, efficacy trial (RCT) was conducted to determine: if aspirin improves VLU healing time; the safety of aspirin in this population; treatment compliance; and the feasibility of recruitment to a phase III trial. We recruited patients from secondary care who were aged ≥ 18 years, had a chronic VLU and not regularly taking aspirin. Participants were randomly assigned (1:1) to receive 300 mg of daily aspirin or placebo in addition to standard care, which consisted of multi component compression therapy aiming to deliver 40 mmHg at the ankle where possible. The randomisation list was stratified by ulcer size (≤ 5 cm2 or > 5 cm2). The primary endpoint was time to ulcer healing, which was defined as ‘complete epithelial healing in the absence of scab (eschar) with no dressing required’. Safety outcomes were assessed in all participants who received at least one dose of the study drug.
Results
Twenty-seven patients were recruited from eight sites (target 100 patients). A short time-frame to recruit and a large number of patients failing to meet the eligibility criteria were the main barriers to recruitment. There was no evidence of a difference in time to healing of the reference ulcer following adjustment for log ulcer area and duration (hazard ratio 0.58, 95% confidence interval 0.18 to 1.85; p = 0.357). One expected serious adverse event related to aspirin was recorded. A number of options to improve recruitment were explored.
Conclusions
There was no evidence that aspirin was effective in expediting the healing of chronic VLUs. However, the analysis was underpowered due to the low number of participants recruited. The trial design would require substantial amendment in order to progress to a phase III (effectiveness) trial
Two long-period transiting exoplanets on eccentric orbits: NGTS-20 b (TOI-5152 b) and TOI-5153 b
Long-period transiting planets provide the opportunity to better understand
the formation and evolution of planetary systems. Their atmospheric properties
remain largely unaltered by tidal or radiative effects of the host star, and
their orbital arrangement reflects a different, and less extreme, migrational
history compared to close-in objects. The sample of long-period exoplanets with
well determined masses and radii is still limited, but a growing number of
long-period objects reveal themselves in the TESS data. Our goal is to vet and
confirm single transit planet candidates detected in the TESS space-based
photometric data through spectroscopic and photometric follow up observations
with ground-based instruments. We use the Next Generation Transit Survey (NGTS)
to photometrically monitor the candidates in order to observe additional
transits. We report the discovery of two massive, warm Jupiter-size planets,
one orbiting the F8-type star TOI-5153 and the other orbiting the G1-type star
NGTS-20 (=TOI-5152). From our spectroscopic analysis, both stars are metal-rich
with a metallicity of 0.12 and 0.15, respectively. Follow-up radial velocity
observations were carried out with CORALIE, CHIRON, FEROS, and HARPS. TOI-5153
hosts a 20.33 day period planet with a planetary mass of 3.26 (+-0.18) Mj, a
radius of 1.06 (+-0.04) Rj , and an orbital eccentricity of 0.091 (+-0.026).
NGTS-20 b is a 2.98 (+-0.16) Mj planet with a radius of 1.07 (+-0.04) Rj on an
eccentric (0.432 +- 0.023) orbit with an orbital period of 54.19 days. Both
planets are metal-enriched and their heavy element content is in line with the
previously reported mass-metallicity relation for gas giants. Both warm
Jupiters orbit moderately bright host stars making these objects valuable
targets for follow-up studies of the planetary atmosphere and measurement of
the spin-orbit angle of the system.Comment: 17 pages, 13 figures, accepted to A&
NGTS-11 b (TOI-1847 b): A Transiting Warm Saturn Recovered from a TESS Single-transit Event
We report the discovery of NGTS-11 b (=TOI-1847 b), a transiting Saturn in a
35.46-day orbit around a mid K-type star (Teff=5050 K). We initially identified
the system from a single-transit event in a TESS full-frame image light-curve.
Following seventy-nine nights of photometric monitoring with an NGTS telescope,
we observed a second full transit of NGTS-11 b approximately one year after the
TESS single-transit event. The NGTS transit confirmed the parameters of the
transit signal and restricted the orbital period to a set of 13 discrete
periods. We combined our transit detections with precise radial velocity
measurements to determine the true orbital period and measure the mass of the
planet. We find NGTS-11 b has a radius of 0.817+0.028-0.032 , a mass of
0.344+0.092-0.073 , and an equilibrium temperature of just 435+34-32 K,
making it one of the coolest known transiting gas giants. NGTS-11 b is the
first exoplanet to be discovered after being initially identified as a TESS
single-transit event, and its discovery highlights the power of intense
photometric monitoring in recovering longer-period transiting exoplanets from
single-transit events
- …