We combine photometry of Eris from a 6-month campaign on the Palomar 60-inch telescope in 2015, a 1-month Hubble Space Telescope WFC3 campaign in 2018, and Dark Energy Survey data spanning 2013--2018 ...to determine a light curve of definitive period \(15.771\pm 0.008\)~days (1-\(\sigma\) formal uncertainties), with nearly sinusoidal shape and peak-to-peak flux variation of 3\%. This is consistent at part-per-thousand precision with the \(P=15.78590\pm0.00005\)~day period of Dysnomia's orbit around Eris, strengthening the recent detection of synchronous rotation of Eris by Szakats et al (2022) with independent data. Photometry from Gaia is consistent with the same light curve. We detect a slope of \(0.05\pm0.01\)~mag per degree of Eris' brightness with respect to illumination phase, intermediate between Pluto's and Charon's values. Variations of \(0.3\)~mag are detected in Dysnomia's brightness, plausibly consistent with a double-peaked light curve at the synchronous period. The synchronous rotation of Eris is consistent with simple tidal models initiated with a giant-impact origin of the binary, but is difficult to reconcile with gravitational capture of Dysnomia by Eris.
An increasing number of traumatic injuries in low- and low-middle-income countries (LICs/LMICs) have coexisting injuries requiring soft-tissue coverage (flaps). Yet, there is a lack of subspecialty ...care and flap training in Latin America. This study assesses the effectiveness of a surgical skills training course in improving rotational and free flap knowledge and identifies barriers to performing these types of flaps.
Participants attending a surgical skills training course in Guadalajara, Mexico completed a pre/postcourse flaps knowledge survey consisting of 15 questions from the plastic surgery in-training examination and also completed a 7-point Likert survey regarding perceived barriers to performing flaps at their institution.
Of the course participants, 17 (44.7%) completed the precourse knowledge survey, 24 (63.2%) completed the postcourse survey, and 37 (97.4%) completed the barriers survey. Scores improved from pre- to postcourse knowledge surveys (39.6% to 53.6%,
= .005). Plastic surgery subsection scores also improved (39.0% to 60.4%,
= .003). Twenty-five percent of attendees received prior flap training and had plastic surgeons available to perform flaps. Few participants (38.9%) reported flap procedures being commonly completed at their hospitals. Participants stating that flaps were uncommon in their hospital reported more institutional barriers and less access to dermatomes. These participants also reported lack of operating room and surgical personnel availability.
A surgical skills training course may be useful in improving knowledge of soft-tissue coverage procedures. There are also modifiable physician and institutional barriers that can improve the ability to perform rotational and free flaps as identified by the course participants.
The OLYMPUS Collaboration reports on a precision measurement of the positron-proton to electron-proton elastic cross section ratio, R_{2γ}, a direct measure of the contribution of hard two-photon ...exchange to the elastic cross section. In the OLYMPUS measurement, 2.01 GeV electron and positron beams were directed through a hydrogen gas target internal to the DORIS storage ring at DESY. A toroidal magnetic spectrometer instrumented with drift chambers and time-of-flight scintillators detected elastically scattered leptons in coincidence with recoiling protons over a scattering angle range of ≈20° to 80°. The relative luminosity between the two beam species was monitored using tracking telescopes of interleaved gas electron multiplier and multiwire proportional chamber detectors at 12°, as well as symmetric Møller or Bhabha calorimeters at 1.29°. A total integrated luminosity of 4.5 fb^{-1} was collected. In the extraction of R_{2γ}, radiative effects were taken into account using a Monte Carlo generator to simulate the convolutions of internal bremsstrahlung with experiment-specific conditions such as detector acceptance and reconstruction efficiency. The resulting values of R_{2γ}, presented here for a wide range of virtual photon polarization 0.456<ε<0.978, are smaller than some hadronic two-photon exchange calculations predict, but are in reasonable agreement with a subtracted dispersion model and a phenomenological fit to the form factor data.
Idiopathic pneumonia syndrome (IPS) is a frequent and often fatal complication of allogeneic bone marrow transplantation (BMT). We have previously shown that experimental IPS is associated with ...alloreactive donor T cells and the inflammatory mediators TNF-alpha and lipopolysaccharide. Both TNF-alpha and lipopolysaccharide are known contributors to endothelial injury. Although damage to vascular endothelia has been associated with other complications after BMT, its relationship to lung injury has not been explored.
We used a well-established murine BMT system, in which lung injury and graft-versus-host disease are induced by minor histocompatibility antigenic differences between donor and host, and the DNA terminal transferase nick-end labeling (TUNEL) procedure to evaluate whether significant pulmonary vascular endothelial cell (EC) apoptosis is present during the development of IPS.
Our data demonstrate that pulmonary histopathology after allogeneic BMT is accompanied by significant EC apoptosis and the appearance of activated caspase 3. Further evaluation reveals that EC injury coincides with the onset of pulmonary pathology, is associated with elevations in bronchoalveolar lavage fluid tumor necrosis factor (TNF)-alpha levels, and is accompanied by evidence for EC activation. Administration of a soluble TNF-alpha binding protein (recombinant human TNF-alpha receptor:Fc) from week 4 to week 6 after allogeneic BMT significantly reduces EC apoptosis and lung histopathology observed in this setting.
EC damage mediated by TNF-alpha is directly linked to the development of experimental IPS. Methods that protect or maintain the integrity of the pulmonary vascular endothelium may therefore prove effective in reducing the severity of lung injury after BMT.
We present an interesting Sunyaev-Zel'dovich (SZ) detection in the first of the Arcminute Microkelvin Imager (AMI) 'blind', degree-square fields to have been observed down to our target sensitivity ...of
. In follow-up deep pointed observations the SZ effect is detected with a maximum peak decrement greater than eight times the thermal noise. No corresponding emission is visible in the ROSAT all-sky X-ray survey and no cluster is evident in the Palomar all-sky optical survey. Compared with existing SZ images of distant clusters, the extent is large (≈10 arcmin) and complex; our analysis favours a model containing two clusters rather than a single cluster. Our Bayesian analysis is currently limited to modelling each cluster with an ellipsoidal or spherical β model, which does not do justice to this decrement. Fitting an ellipsoid to the deeper candidate we find the following. (a) Assuming that the Evrard et al. approximation to Press & Schechter correctly gives the number density of clusters as a function of mass and redshift, then, in the search area, the formal Bayesian probability ratio of the AMI detection of this cluster is 7.9 × 104:1; alternatively assuming Jenkins et al. as the true prior, the formal Bayesian probability ratio of detection is 2.1 × 105:1. (b) The cluster mass is
. (c) Abandoning a physical model with number density prior and instead simply modelling the SZ decrement using a phenomenological β model of temperature decrement as a function of angular distance, we find a central SZ temperature decrement of
K - this allows for cosmic microwave background primary anisotropies, receiver noise and radio sources. We are unsure if the cluster system we observe is a merging system or two separate clusters.
Gamma-ray bursts (GRBs) are brief flashes of γ-rays and are considered to be the most energetic explosive phenomena in the Universe
. The emission from GRBs comprises a short (typically tens of ...seconds) and bright prompt emission, followed by a much longer afterglow phase. During the afterglow phase, the shocked outflow-produced by the interaction between the ejected matter and the circumburst medium-slows down, and a gradual decrease in brightness is observed
. GRBs typically emit most of their energy via γ-rays with energies in the kiloelectronvolt-to-megaelectronvolt range, but a few photons with energies of tens of gigaelectronvolts have been detected by space-based instruments
. However, the origins of such high-energy (above one gigaelectronvolt) photons and the presence of very-high-energy (more than 100 gigaelectronvolts) emission have remained elusive
. Here we report observations of very-high-energy emission in the bright GRB 180720B deep in the GRB afterglow-ten hours after the end of the prompt emission phase, when the X-ray flux had already decayed by four orders of magnitude. Two possible explanations exist for the observed radiation: inverse Compton emission and synchrotron emission of ultrarelativistic electrons. Our observations show that the energy fluxes in the X-ray and γ-ray range and their photon indices remain comparable to each other throughout the afterglow. This discovery places distinct constraints on the GRB environment for both emission mechanisms, with the inverse Compton explanation alleviating the particle energy requirements for the emission observed at late times. The late timing of this detection has consequences for the future observations of GRBs at the highest energies.
Centaurs, distinguished by their volatile-rich compositions, play a pivotal
role in understanding the formation and evolution of the early solar system, as
they represent remnants of the primordial ...material that populated the outer
regions. Stellar occultations offer a means to investigate their physical
properties, including shape, rotational state, or the potential presence of
satellites and rings.
This work aims to conduct a detailed study of the centaur (54598) Bienor
through stellar occultations and rotational light curves from photometric data
collected during recent years.
We successfully predicted three stellar occultations by Bienor, which were
observed from Japan, Eastern Europe, and the USA. In addition, we organized
observational campaigns from Spain to obtain rotational light curves. At the
same time, we develop software to generate synthetic light curves from
three-dimensional shape models, enabling us to validate the outcomes through
computer simulations.
We resolve Bienor's projected ellipse for December 26, 2022, determine a
prograde sense of rotation, and confirm an asymmetric rotational light curve.
We also retrieve the axes of its triaxial ellipsoid shape as a = (127 $\pm$ 5)
km, b = (55 $\pm$ 4) km, and c = (45 $\pm$ 4) km. Moreover, we refine the
rotation period to 9.1736 $\pm$ 0.0002 hours and determine a geometric albedo
of (6.5 $\pm$ 0.5) %, higher than previously determined by other methods.
Finally, by comparing our findings with previous results and simulated
rotational light curves, we analyze whether an irregular or contact-binary
shape, the presence of an additional element such as a satellite, or
significant albedo variations on Bienor's surface, may be present.
Galactic cosmic rays reach energies of at least a few petaelectronvolts (of the order of 10(15) electronvolts). This implies that our Galaxy contains petaelectronvolt accelerators ('PeVatrons'), but ...all proposed models of Galactic cosmic-ray accelerators encounter difficulties at exactly these energies. Dozens of Galactic accelerators capable of accelerating particles to energies of tens of teraelectronvolts (of the order of 10(13) electronvolts) were inferred from recent γ-ray observations. However, none of the currently known accelerators--not even the handful of shell-type supernova remnants commonly believed to supply most Galactic cosmic rays--has shown the characteristic tracers of petaelectronvolt particles, namely, power-law spectra of γ-rays extending without a cut-off or a spectral break to tens of teraelectronvolts. Here we report deep γ-ray observations with arcminute angular resolution of the region surrounding the Galactic Centre, which show the expected tracer of the presence of petaelectronvolt protons within the central 10 parsecs of the Galaxy. We propose that the supermassive black hole Sagittarius A* is linked to this PeVatron. Sagittarius A* went through active phases in the past, as demonstrated by X-ray outburstsand an outflow from the Galactic Centre. Although its current rate of particle acceleration is not sufficient to provide a substantial contribution to Galactic cosmic rays, Sagittarius A* could have plausibly been more active over the last 10(6)-10(7) years, and therefore should be considered as a viable alternative to supernova remnants as a source of petaelectronvolt Galactic cosmic rays.
The inner region of the Milky Way halo harbors a large amount of dark matter (DM). Given its proximity, it is one of the most promising targets to look for DM. We report on a search for the ...annihilations of DM particles using γ-ray observations towards the inner 300 pc of the Milky Way, with the H.E.S.S. array of ground-based Cherenkov telescopes. The analysis is based on a 2D maximum likelihood method using Galactic Center (GC) data accumulated by H.E.S.S. over the last 10 years (2004-2014), and does not show any significant γ-ray signal above background. Assuming Einasto and Navarro-Frenk-White DM density profiles at the GC, we derive upper limits on the annihilation cross section ⟨σv⟩. These constraints are the strongest obtained so far in the TeV DM mass range and improve upon previous limits by a factor 5. For the Einasto profile, the constraints reach ⟨σv⟩ values of 6×10^{-26} cm^{3} s^{-1} in the W^{+}W^{-} channel for a DM particle mass of 1.5 TeV, and 2×10^{-26} cm^{3} s^{-1} in the τ^{+}τ^{-} channel for a 1 TeV mass. For the first time, ground-based γ-ray observations have reached sufficient sensitivity to probe ⟨σv⟩ values expected from the thermal relic density for TeV DM particles.
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