5,634 research outputs found
Distillation of Fe in Ultramassive O-Ne White Dwarfs
When white dwarfs freeze the plasma mixtures inside them undergo separation
processes which can produce radical changes in the composition profile of the
star. The abundance of neutron rich elements, such as Ne or Fe,
determines whether or not the first crystals are more or less dense than the
surrounding fluid and thus whether they sink or float. These processes have now
been studied for C-O-Ne and C-O-Fe mixtures, finding that distillation and
precipitation processes are possible in white dwarfs. In this work, we
calculate the phase diagram of more complicated O-Ne-Fe mixtures and make
predictions for the internal structure of the separated white dwarf. There are
two possible outcomes determined by a complicated interplay between the Ne
abundance, the Ne fraction, and the Fe abundance. Either Fe
distills to form an inner core because the first O-Ne solids are buoyant, or an
O-Ne inner core forms and Fe accumulates in the liquid until Fe distillation
begins and forms a Fe shell. In the case of an Fe shell, a Rayleigh-Taylor
instability may arise and overturn the core. In either case, Fe distillation
may only produce a cooling delay of order 0.1 Gyr as these processes occur
early at high white dwarf luminosities. Fe inner cores and shells may be
detectable through asteroseismology and could enhance the yield of neutron rich
elements such as Mn and Ni in supernovae.Comment: 8 pages, 3 figures, accepted for publication in Ap
Short-term genome stability of serial Clostridium difficile ribotype 027 isolates in an experimental gut model and recurrent human disease
Copyright: © 2013 Eyre et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are creditedClostridium difficile whole genome sequencing has the potential to identify related isolates, even among otherwise indistinguishable strains, but interpretation depends on understanding genomic variation within isolates and individuals.Serial isolates from two scenarios were whole genome sequenced. Firstly, 62 isolates from 29 timepoints from three in vitro gut models, inoculated with a NAP1/027 strain. Secondly, 122 isolates from 44 patients (2–8 samples/patient) with mostly recurrent/on-going symptomatic NAP-1/027 C. difficile infection. Reference-based mapping was used to identify single nucleotide variants (SNVs).Across three gut model inductions, two with antibiotic treatment, total 137 days, only two new SNVs became established. Pre-existing minority SNVs became dominant in two models. Several SNVs were detected, only present in the minority of colonies at one/two timepoints. The median (inter-quartile range) [range] time between patients’ first and last samples was 60 (29.5–118.5) [0–561] days. Within-patient C. difficile evolution was 0.45 SNVs/called genome/year (95%CI 0.00–1.28) and within-host diversity was 0.28 SNVs/called genome (0.05–0.53). 26/28 gut model and patient SNVs were non-synonymous, affecting a range of gene targets.The consistency of whole genome sequencing data from gut model C. difficile isolates, and the high stability of genomic sequences in isolates from patients, supports the use of whole genome sequencing in detailed transmission investigations.Peer reviewe
Fatty acid nitroalkenes ameliorate glucose intolerance and pulmonary hypertension in high-fat diet-induced obesity
Aims Obesity is a risk factor for diabetes and cardiovascular diseases, with the incidence of these disorders becoming epidemic. Pathogenic responses to obesity have been ascribed to adipose tissue (AT) dysfunction that promotes bioactive mediator secretion from visceral AT and the initiation of pro-inflammatory events that induce oxidative stress and tissue dysfunction. Current understanding supports that suppressing pro-inflammatory and oxidative events promotes improved metabolic and cardiovascular function. In this regard, electrophilic nitro-fatty acids display pleiotropic anti-inflammatory signalling actions. Methods and results It was hypothesized that high-fat diet (HFD)-induced inflammatory and metabolic responses, manifested by loss of glucose tolerance and vascular dysfunction, would be attenuated by systemic administration of nitrooctadecenoic acid (OA-NO2). Male C57BL/6j mice subjected to a HFD for 20 weeks displayed increased adiposity, fasting glucose, and insulin levels, which led to glucose intolerance and pulmonary hypertension, characterized by increased right ventricular (RV) end-systolic pressure (RVESP) and pulmonary vascular resistance (PVR). This was associated with increased lung xanthine oxidoreductase (XO) activity, macrophage infiltration, and enhanced expression of pro-inflammatory cytokines. Left ventricular (LV) end-diastolic pressure remained unaltered, indicating that the HFD produces pulmonary vascular remodelling, rather than LV dysfunction and pulmonary venous hypertension. Administration of OA-NO2 for the final 6.5 weeks of HFD improved glucose tolerance and significantly attenuated HFD-induced RVESP, PVR, RV hypertrophy, lung XO activity, oxidative stress, and pro-inflammatory pulmonary cytokine levels. Conclusions These observations support that the pleiotropic signalling actions of electrophilic fatty acids represent a therapeutic strategy for limiting the complex pathogenic responses instigated by obesity.Fil: Kelley, Eric E.. University of Pittsburgh; Estados UnidosFil: Baust, Jeff. University of Pittsburgh; Estados UnidosFil: Bonacci, Gustavo Roberto. University of Pittsburgh; Estados Unidos. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico CĂłrdoba. Centro de Investigaciones en BioquĂmica ClĂnica e InmunologĂa; ArgentinaFil: Golin Bisello, Franca. University of Pittsburgh; Estados UnidosFil: Devlin, Jason E.. University of Pittsburgh; Estados UnidosFil: Croix, Claudette M. St.. University of Pittsburgh; Estados UnidosFil: Watkins, Simon C.. University of Pittsburgh; Estados UnidosFil: Gor, Sonia. University of Pittsburgh; Estados UnidosFil: Cantu Medellin, Nadiezhda. University of Pittsburgh; Estados UnidosFil: Weidert, Eric R.. University of Pittsburgh; Estados UnidosFil: Frisbee,Jefferson C.. University of Virginia; Estados UnidosFil: Gladwin, Mark T.. University of Pittsburgh; Estados UnidosFil: Champion, Hunter C.. University of Pittsburgh; Estados UnidosFil: Freeman, Bruce A.. University of Pittsburgh; Estados UnidosFil: Khoo, Nicholas K.H.. University of Pittsburgh; Estados Unido
Translabyrinthine resection of NF2 associated vestibular schwannoma with cochlear implant insertion
The authors present the case of a 24-year-old female with neurofibromatosis type 2. Growth of the left vestibular schwannoma and progressive hearing loss prompted the decision to proceed to translabyrinthine resection with cochlear nerve preservation and cochlear implant insertion. Complete resection with preservation of the facial and cochlear nerves was achieved. The patient had grade 1 facial function and was discharged on postoperative day 4 following suturing of a minor CSF leak. This case highlights the feasibility of cochlear nerve preservation and cochlear implant insertion in appropriately selected patients, offering a combination of effective tumor control and hearing rehabilitation. The video can be found here: https://stream.cadmore.media/r10.3171/2021.7.FOCVID2112
The ANU WiFeS SuperNovA Program (AWSNAP)
This paper presents the first major data release and survey description for
the ANU WiFeS SuperNovA Program (AWSNAP). AWSNAP is an ongoing supernova
spectroscopy campaign utilising the Wide Field Spectrograph (WiFeS) on the
Australian National University (ANU) 2.3m telescope. The first and primary data
release of this program (AWSNAP-DR1) releases 357 spectra of 175 unique objects
collected over 82 equivalent full nights of observing from July 2012 to August
2015. These spectra have been made publicly available via the WISeREP supernova
spectroscopy repository. We analyse the AWSNAP sample of Type Ia supernova
spectra, including measurements of narrow sodium absorption features afforded
by the high spectral resolution of the WiFeS instrument. In some cases we were
able to use the integral-field nature of the WiFeS instrument to measure the
rotation velocity of the SN host galaxy near the SN location in order to obtain
precision sodium absorption velocities. We also present an extensive time
series of SN 2012dn, including a near-nebular spectrum which both confirms its
"super-Chandrasekhar" status and enables measurement of the sub-solar host
metallicity at the SN site.Comment: Submitted to Publications of the Astronomical Society of Australia
(PASA). Spectra publicly released via WISeREP at
http://wiserep.weizmann.ac.il
The Distribution of Mass in the Orion Dwarf Galaxy
Dwarf galaxies are good candidates to investigate the nature of Dark Matter,
because their kinematics are dominated by this component down to small
galactocentric radii. We present here the results of detailed kinematic
analysis and mass modelling of the Orion dwarf galaxy, for which we derive a
high quality and high resolution rotation curve that contains negligible
non-circular motions and we correct it for the asymmetric drift. Moreover, we
leverage the proximity (D = 5.4 kpc) and convenient inclination (47{\deg}) to
produce reliable mass models of this system. We find that the Universal
Rotation Curve mass model (Freeman disk + Burkert halo + gas disk) fits the
observational data accurately. In contrast, the NFW halo + Freeman disk + gas
disk mass model is unable to reproduce the observed Rotation Curve, a common
outcome in dwarf galaxies. Finally, we attempt to fit the data with a MOdified
Newtonian Dynamics (MOND) prescription. With the present data and with the
present assumptions on distance, stellar mass, constant inclination and
reliability of the gaseous mass, the MOND "amplification" of the baryonic
component appears to be too small to mimic the required "dark component". The
Orion dwarf reveals a cored DM density distribution and a possible tension
between observations and the canonical MOND formalism.Comment: 8 pages, 9 figures, accepted for publication in MNRA
Testicular microlithiasis imaging and follow-up: guidelines of the ESUR scrotal imaging subcommittee
The subcommittee on scrotal imaging, appointed by the board of the European Society of Urogenital Radiology (ESUR), have produced guidelines on imaging and follow-up in testicular microlithiasis (TML)
Estimating the horizontal and vertical direction-of-arrival of water-borne seismic signals in the northern Philippine Sea
Author Posting. © Acoustical Society of America, 2013. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 134 (2013): 3282, doi:10.1121/1.4818843.Conventional and adaptive plane-wave beamforming with simultaneous recordings by large-aperture horizontal and vertical line arrays during the 2009 Philippine Sea Engineering Test (PhilSea09) reveal the rate of occurrence and the two-dimensional arrival structure of seismic phases that couple into the deep ocean. A ship-deployed, controlled acoustic source was used to evaluate performance of the horizontal array for a range of beamformer adaptiveness levels. Ninety T-phases from unique azimuths were recorded between Yeardays 107 to 119. T-phase azimuth and S-minus-P-phase time-of-arrival range estimates were validated using United States Geological Survey seismic monitoring network data. Analysis of phases from a seismic event that occurred on Yearday 112 near the east coast of Taiwan approximately 450 km from the arrays revealed a 22° clockwise evolution of T-phase azimuth over 90 s. Two hypotheses to explain such evolution—body wave excitation of multiple sources or in-water scattering—are presented based on T-phase origin sites at the intersection of azimuthal great circle paths and ridge/coastal bathymetry. Propagation timing between the source, scattering region, and array position suggests the mechanism behind the evolution involved scattering of the T-phase from the Ryukyu Ridge and a T-phase formation/scattering location estimation error of approximately 3.2 km.This research is supported
by the Office of Naval Research, both the Applied Research
Laboratory program and Code 322(OA)
Wide-field dynamic astronomy in the near-infrared with Palomar Gattini-IR and DREAMS
There have been a dramatic increase in the number of optical and radio transient surveys due to astronomical transients such as gravitational waves and gamma ray bursts, however, there have been a limited number of wide-field infrared surveys due to narrow field-of-view and high cost of infrared cameras, we present two new wide-field near-infrared fully automated surveyors; Palomar Gattini-IR and the Dynamic REd All-sky Monitoring Survey (DREAMS). Palomar Gattini-IR, a 25 square degree J-band imager that begun science operations at Palomar Observatory, USA in October 2018; we report on survey strategy as well as telescope and observatory operations and will also providing initial science results. DREAMS is a 3.75 square degree wide-field imager that is planned for Siding Spring Observatory, Australia; we report on the current optical and mechanical design and plans to achieve on-sky results in 2020. DREAMS is on-track to be one of the first astronomical telescopes to use an Indium Galium Arsenide (InGaAs) detector and we report initial on-sky testing results for the selected detector package. DREAMS is also well placed to take advantage and provide near-infrared follow-up of the LSST
Bang-bang control of fullerene qubits using ultra-fast phase gates
Quantum mechanics permits an entity, such as an atom, to exist in a
superposition of multiple states simultaneously. Quantum information processing
(QIP) harnesses this profound phenomenon to manipulate information in radically
new ways. A fundamental challenge in all QIP technologies is the corruption of
superposition in a quantum bit (qubit) through interaction with its
environment. Quantum bang-bang control provides a solution by repeatedly
applying `kicks' to a qubit, thus disrupting an environmental interaction.
However, the speed and precision required for the kick operations has presented
an obstacle to experimental realization. Here we demonstrate a phase gate of
unprecedented speed on a nuclear spin qubit in a fullerene molecule (N@C60),
and use it to bang-bang decouple the qubit from a strong environmental
interaction. We can thus trap the qubit in closed cycles on the Bloch sphere,
or lock it in a given state for an arbitrary period. Our procedure uses
operations on a second qubit, an electron spin, in order to generate an
arbitrary phase on the nuclear qubit. We anticipate the approach will be vital
for QIP technologies, especially at the molecular scale where other strategies,
such as electrode switching, are unfeasible
- …