764 research outputs found
A Comparative Anatomical Study of Mandibular Structure in Bees
Volume: 51Start Page: 463End Page: 48
Parameter Inference from Event Ensembles and the Top-Quark Mass
One of the key tasks of any particle collider is measurement. In practice,
this is often done by fitting data to a simulation, which depends on many
parameters. Sometimes, when the effects of varying different parameters are
highly correlated, a large ensemble of data may be needed to resolve
parameter-space degeneracies. An important example is measuring the top-quark
mass, where other physical and unphysical parameters in the simulation must be
marginalized over when fitting the top-quark mass parameter. We compare three
different methodologies for top-quark mass measurement: a classical histogram
fitting procedure, similar to one commonly used in experiment optionally
augmented with soft-drop jet grooming; a machine-learning method called DCTR;
and a linear regression approach, either using a least-squares fit or with a
dense linearly-activated neural network. Despite the fact that individual
events are totally uncorrelated, we find that the linear regression methods
work most effectively when we input an ensemble of events sorted by mass,
rather than training them on individual events. Although all methods provide
robust extraction of the top-quark mass parameter, the linear network does
marginally best and is remarkably simple. For the top study, we conclude that
the Monte-Carlo-based uncertainty on current extractions of the top-quark mass
from LHC data can be reduced significantly (by perhaps a factor of 2) using
networks trained on sorted event ensembles. More generally, machine learning
from ensembles for parameter estimation has broad potential for collider
physics measurements.Comment: v1: 27 + 5 pages, 14 + 3 figures. v2: Matches version accepted to
JHE
Pulmonary artery resuscitation for isolated ductal origin of a pulmonary artery
ObjectiveDuctal origin of a pulmonary artery (DOPA) is commonly misdiagnosed as agenesis of a pulmonary artery (PA), which may result in inadequate treatment. The objective is to describe the results of resuscitation of unilateral DOPA.MethodsThis study is a retrospective review of all patients with unilateral DOPA who underwent PA resuscitation at Texas Children's Hospital from 1993 to 2012. Patients with other cardiac or contralateral lung anomalies were excluded.ResultsTen patients, median age 2 years (range, 3 days to 9 years), with unilateral DOPA were included. Symptoms were present in 6 patients. Cardiac catheterization was performed in all and showed a patent duct or a ductal stump in most patients and a small PA on wedge angiography of the pulmonary veins. Two patients underwent single-stage centralization. The other 8 underwent ductal stenting (n = 2) or a systemic-to-PA shunt (n = 6) as the first stage before centralization. The 2 patients with ductal stenting developed pulmonary edema. The 2 patients with a cryopreserved vein shunt developed early thrombosis requiring reintervention. Nine patients have undergone centralization. Six patients have required further interventional procedures. There have been no deaths. Symptoms and lung hypoplasia have improved in all patients. Median relative lung perfusion at follow-up was 26% (range, 12%-46%) with significant improvement in the size of the affected PA.ConclusionsPA resuscitation is effective at restoring flow to the affected lung resulting in improved diameter of the PA, lung growth, and resolution of symptoms. PA resuscitation should be considered in all children with DOPA, including those beyond infancy
A review of the relationship between eggshell colour and water vapour conductance
This review brings together the available literature that examines the effect of variations in pigmentation on the gas conductance of avian eggshells. Pheasant and Houbara bustard eggs provide some evidence that shell abnormalities can impact upon colour and conductance. By contrast, data from wild birds suggest that neither the degree of maculation or intensity of ground colour impact upon gas conductance. Those studies that purport to show variation in rates of water loss in eggs with different degrees of pigmentation may have been confounded by variation in nest humidity. This emerging field of research remains very much in its infancy
Infundibular sparing versus transinfundibular approach to the repair of tetralogy of Fallot
IntroductionThe right ventricular infundibular sparing approach (RVIS) to the repair of tetralogy of Fallot (TOF) avoids a full‐thickness ventricular incision, typically utilized in the transinfundibular (TI) method.MethodsWe performed a retrospective, age‐matched cohort study of patients who underwent RVIS at Texas Children’s Hospital or TI at Children’s Hospital Medical Center in Nebraska and subsequently underwent cardiac magnetic resonance imaging (CMR). We compared right ventricular end‐diastolic and systolic volumes indexed to body surface area (RVEDVi and RVESVi) and right ventricular ejection fraction (RVEF) as primary endpoints. Secondary endpoints were indexed left ventricular diastolic and systolic volume (LVEDVi and LVESVi), left ventricular ejection fraction (LVEF), right ventricular (RV) sinus ejection fraction (EF) and RV outflow tract EF (RVOT EF).ResultsSeventy‐nine patients were included in the analysis; 40 underwent RVIS and 39 underwent TI repair. None of the patients in the TI repair group had an initial palliation with a systemic to pulmonary arterial shunt compared to seven (18%) in the RVIS group (P < .01). There was no appreciable difference in RVEDVi (122 ± 29 cc/m2 vs 130 ± 29 cc/m2, P = .59) or pulmonary regurgitant fraction (40 ± 13 vs 37 ± 18, P = .29) between the RVIS and TI groups. Compared to the TI group, the RVIS group had higher RVEF (54 ± 6% vs 44 ± 9%, P < .01), lower RVESV (57 ± 17 cc/m2 vs 67 ± 25 cc/m2, P = .03), higher LVEF (61 ± 11% vs 54 ± 8%, P < .01), higher RVOT EF (47 ± 12% vs 41 ± 11%, P = .03), and higher RV sinus EF (56 ± 5% vs 49 ± 6%, P < .01)ConclusionsIn this selected cohort, patients who underwent RVIS repair for TOF had higher right and left ventricular ejection fraction compared to those who underwent TI repair.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/152818/1/chd12863_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/152818/2/chd12863.pd
Seven reflares, a mini-outburst and an outburst : High amplitude optical variations in the black hole X-ray binary Swift J1910.2-0546
We present long-term (2012-2022) optical monitoring of the candidate black
hole X-ray binary Swift J1910.2-0546 with the Faulkes Telescopes and Las
Cumbres Observatory (LCO) network. Following its initial bright 2012 outburst,
we find that the source displayed a series of at least 7 quasi-periodic, high
amplitude (~3 mags) optical reflares in 2013, with a recurrence time increasing
from ~42 days to ~49 days. In 2014, the source experienced a mini-outburst with
two peaks in the optical. We also study the recent 2022 outburst of the source
at optical wavelengths, and perform a comparative analysis with the earlier
rebrightenings. A single X-ray detection and only two radio detections were
obtained during the 2013 reflaring period, and only optical detections were
acquired in 2014. During the reflaring in both 2013 and 2014, the source showed
bluer-when-brighter behavior, having optical colors consistent with a blackbody
heating and cooling between 4500 and 9500 K, i.e. the temperature range in
which hydrogen starts to ionize. Finally, we compare the flaring behavior of
the source to re-brightening events in other X-ray binaries. We show that the
repeated reflarings of Swift J1910.2-0546 are highly unusual, and propose that
they arise from a sequence of repetitive heating and cooling front reflections
travelling through the accretion disk.Comment: Accepted for publication in ApJ, appendix will appear at the
published version of the pape
Surveillance mammography for detecting ipsilateral breast tumour recurrence and metachronous contralateral breast cancer: a systematic review
Peer reviewedPostprin
The impact of acute lung injury, ECMO and transfusion on oxidative stress and plasma selenium levels in an ovine model
The purpose of this study was to determine the effects of smoke induced acute lung. injury (S-ALI), extracorporeal membrane oxygenation (ECMO) and transfusion on oxidative stress and plasma selenium levels. Forty ewes were divided into (i) healthy control (n = 4), (ii) S-ALI control (n = 7), (iii) ECMO control (n = 7), (iv) S-ALI + ECMO (n = 8) and (v) S-ALI + ECM + packed red blood cell (PRBC) transfusion (n = 14). Plasma thiobarbituric acid reactive substances (TBARS), selenium and glutathione peroxidase (GPx) activity were analysed at baseline, after smoke injury (or sham) and 0.25, 1, 2, 6, 7, 12 and 24 h after initiation of ECMO. Peak TBARS levels were similar across all groups. Plasma selenium decreased by 54% in S-ALI sheep (1.36 +/- 0.20 to 0.63 +/- 0.27 mu mol/L, p < 0.0001), and 72% in sheep with S-ALI + ECMO at 24 h (1.36 +/- 0.20 to 0.38 +/- 0.19, p < 0.0001). PRBC transfusion had no effect on TBARS, selenium levels or glutathione peroxidase activity in plasma. While ECMO independently increased TBARS in healthy sheep to levels which were similar to the S-ALI control, the addition of ECMO after S-ALI caused a negligible increase in TBARS. This suggests that the initial lung injury was the predominant feature in the TBARS response. In contrast, the addition of ECM in S-ALI sheep exacerbated reductions in plasma selenium beyond that of S-ALI or ECM alone. Clinical studies are needed to confirm the extent and duration of selenium loss associated with ECMO. Crown Copyright (C) 2015 Published by Elsevier GmbH. All rights reserved
A Massive Progenitor of the Luminous Type IIn Supernova 2010jl
The bright, nearby, recently discovered supernova SN2010jl is a member of the
rare class of relatively luminous Type~IIn events. Here we report archival HST
observations of its host galaxy UGC5189A taken roughly 10yr prior to explosion,
as well as early-time optical spectra of the SN. The HST images reveal a
bright, blue point source at the position of the SN, with an absolute magnitude
of -12.0 in the F300W filter. If it is not just a chance alignment, the source
at the SN position could be (1) a massive young (less than 6 Myr) star cluster
in which the SN resided, (2) a quiescent, luminous blue star with an apparent
temperature around 14,000K, (3) a star caught during a bright outburst akin to
those of LBVs, or (4) a combination of option 1 and options 2 or 3. Although we
cannot confidently choose between these possibilities with the present data,
any of them imply that the progenitor of SN2010jl had an initial mass above
30Msun. This reinforces mounting evidence that many SNe IIn result from very
massive stars, that massive stars can produce visible SNe without collapsing
quietly to black holes, and that massive stars can retain their H envelopes
until shortly before explosion. Standard stellar evolution models fail to
account for these observed properties.Comment: 6 pages, 4 figures, submitted to Ap
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