1,639 research outputs found
Aerial and Ground-Based Optical Gas Imaging Survey of Uinta Basin Oil and Gas Wells
We deployed a helicopter with an infrared optical gas imaging camera to detect hydrocarbon emissions from 3,428 oil and gas facilities (including 3,225 producing oil and gas well pads) in Utah’s Uinta Basin during winter and spring 2018. We also surveyed 419 of the same well pads from the ground. Winter conditions led to poor contrast between emission plumes and the ground, leading to a detection limit for the aerial survey that was between two and six times worse than a previous summertime survey. Because the ground survey was able to use the camera’s high-sensitivity mode, the rate of detected emission plumes was much higher in the ground survey (31% of all surveyed well pads) relative to the aerial survey (0.5%), but colder air temperatures appeared to impair plume detection in the ground survey as well. The aerial survey cost less per facility visited, but the ground survey cost less per emission plume detected.
Well pads with detected emissions during the ground and aerial surveys had higher oil and gas production, were younger, were more likely to be oil well pads, and had more liquid storage tanks per pad relative to the entire surveyed population. The majority of observed emission plumes were from liquid storage tanks (75.9% of all observed plumes), including emissions from pressure relief valves and thief hatches on the tank or from piping that connects to the tank. Well pads with control devices to reduce emissions from tanks (combustors or vapor recovery units) were more likely to have detected emissions. This finding does not imply that the control devices themselves were not functioning properly. Instead, gas was escaping into the atmosphere before it reached control devices. Pads with control devices tended to be newer and have higher oil and gas production, which probably explains their higher rate of detected emissions
The diversity of kilonova emission in short gamma-ray bursts
The historic first joint detection of both gravitational-wave and electromagnetic emission from a binary neutron star merger cemented the association between short gamma-ray bursts (SGRBs) and compact object mergers, as well as providing a well-sampled multi-wavelength light curve of a radioactive kilonova (KN) for the first time. Here, we compare the optical and near-infrared light curves of this KN, AT 2017gfo, to the counterparts of a sample of nearby (z < 0.5) SGRBs to characterize their diversity in terms of their brightness distribution. Although at similar epochs AT 2017gfo appears fainter than every SGRB-associated KN claimed so far, we find three bursts (GRBs 050509B, 061201, and 080905A) where, if the reported redshifts are correct, deep upper limits rule out the presence of a KN similar to AT 2017gfo by several magnitudes. Combined with the properties of previously claimed KNe in SGRBs this suggests considerable diversity in the properties of KN drawn from compact object mergers, despite the similar physical conditions that are expected in many NS–NS mergers. We find that observer angle alone is not able to explain this diversity, which is likely a product of the merger type (NS–NS versus NS–BH) and the detailed properties of the binary (mass ratio, spins etc.). Ultimately disentangling these properties should be possible through observations of SGRBs and gravitational-wave sources, providing direct measurements of heavy element enrichment throughout the universe
Searching for ejected supernova companions in the era of precise proper motion and radial velocity measurements
The majority of massive stars are born in binaries, and most unbind upon the
first supernova. With precise proper motion surveys such as Gaia, it is
possible to trace back the motion of stars in the vicinity of young remnants to
search for ejected companions. Establishing the fraction of remnants with an
ejected companion, and the photometric and kinematic properties of these stars,
offers unique insight into supernova progenitor systems. In this paper, we
employ binary population synthesis to produce kinematic and photometric
predictions for ejected secondary stars. We demonstrate that the unbound
neutron star velocity distribution from supernovae in binaries closely traces
the input kicks. Therefore, the observed distribution of neutron star
velocities should be representative of their natal kicks. We evaluate the
probability for any given filter, magnitude limit, minimum measurable proper
motion (as a function of magnitude), temporal baseline, distance and extinction
that an unbound companion can be associated with a remnant. We compare our
predictions with results from previous companion searches, and demonstrate that
the current sample of stars ejected by the supernova of their companion can be
increased by a factor of 5-10 with Gaia data release 3. Further progress in
this area is achievable by leveraging the absolute astrometric precision of
Gaia, and by obtaining multiple epochs of deep, high resolution near-infrared
imaging with the Hubble Space Telescope, JWST and next-generation wide-field
near-infrared observatories such as Euclid or the Nancy Grace Roman Space
Telescope.Comment: Accepted for publication in MNRAS. 19 pages, 17 figure
Supportive care in patients with cancer during the COVID-19 pandemic
Cancer care has been profoundly impacted by the global pandemic of severe acute respiratory syndrome coronavirus 2 disease (coronavirus disease 2019, COVID-19), resulting in unprecedented challenges. Supportive care is an essential component of cancer treatment, seeking to prevent and manage chemotherapy complications such as febrile neutropenia, anaemia, thrombocytopenia/bleeding, thromboembolic events and nausea/vomiting, all of which are common causes of hospitalisation. These adverse events are an essential consideration under routine patient management, but particularly so during a pandemic, a setting in which clinicians aim to minimise patients' risk of infection and need for hospital visits. Professional medical oncology societies have been providing updated guidelines to support health care professionals with the management, treatment and supportive care needs of their patients with cancer under the threat of COVID-19. This paper aims to review the recommendations made by the most prominent medical oncology societies for devising and modifying supportive care strategies during the pandemic.The Global Organisationhttps://www.esmoopen.comam2022Immunolog
UV continuum emission and diagnostics of hydrogen-containing non-equilibrium plasmas
For the first time the emission of the radiative dissociation continuum of
the hydrogen molecule ( electronic
transition) is proposed to be used as a source of information for the
spectroscopic diagnostics of non-equilibrium plasmas. The detailed analysis of
excitation-deactivation kinetics, rate constants of various collisional and
radiative transitions and fitting procedures made it possible to develop two
new methods of diagnostics of: (1) the ground state
vibrational temperature from the relative intensity
distribution, and (2) the rate of electron impact dissociation
(d[\mbox{H_{2}}]/dt)_{\text{diss}} from the absolute intensity of the
continuum. A known method of determination of from relative
intensities of Fulcher- bands was seriously corrected and simplified
due to the revision of transition probabilities and cross sections of
electron impact excitation. General considerations are illustrated
with examples of experiments in pure hydrogen capillary-arc and H+Ar
microwave discharges.Comment: REVTeX, 25 pages + 12 figures + 9 tables. Phys. Rev. E, eprint
replaced because of resubmission to journal after referee's 2nd repor
The Atacama Cosmology Telescope: the stellar content of galaxy clusters selected using the Sunyaev-Zel'dovich effect
We present a first measurement of the stellar mass component of galaxy
clusters selected via the Sunyaev-Zel'dovich (SZ) effect, using 3.6 um and 4.5
um photometry from the Spitzer Space Telescope. Our sample consists of 14
clusters detected by the Atacama Cosmology Telescope (ACT), which span the
redshift range 0.27 < z < 1.07 (median z = 0.50), and have dynamical mass
measurements, accurate to about 30 per cent, with median M500 = 6.9 x 10^{14}
MSun. We measure the 3.6 um and 4.5 um galaxy luminosity functions, finding the
characteristic magnitude (m*) and faint-end slope (alpha) to be similar to
those for IR-selected cluster samples. We perform the first measurements of the
scaling of SZ-observables (Y500 and y0) with both brightest cluster galaxy
(BCG) stellar mass and total cluster stellar mass (M500star). We find a
significant correlation between BCG stellar mass and Y500 (E(z)^{-2/3} DA^2
Y500 ~ M*^{1.2 +/- 0.6}), although we are not able to obtain a strong
constraint on the slope of the relation due to the small sample size.
Additionally, we obtain E(z)^{-2/3} DA^2 Y500 ~ M500star^{1.0 +/- 0.6} for the
scaling with total stellar mass. The mass fraction in stars spans the range
0.006-0.034, with the second ranked cluster in terms of dynamical mass (ACT-CL
J0237-4939) having an unusually low total stellar mass and the lowest stellar
mass fraction. For the five clusters with gas mass measurements available in
the literature, we see no evidence for a shortfall of baryons relative to the
cosmic mean value.Comment: Accepted for publication in MNRAS; 12 pages, 10 figure
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