11,167 research outputs found
Limits on stable iron in TypeIa supernovae from NIR spectroscopy
We obtained optical and near-infrared spectra of TypeIa supernovae
(SNeIa) at epochs ranging from 224 to 496 days after the explosion. The
spectra show emission lines from forbidden transitions of singly ionised iron
and cobalt atoms. We used non-local thermodynamic equilibrium (NLTE) modelling
of the first and second ionisation stages of iron, nickel, and cobalt to fit
the spectra using a sampling algorithm allowing us to probe a broad parameter
space. We derive velocity shifts, line widths, and abundance ratios for iron
and cobalt. The measured line widths and velocity shifts of the singly ionised
ions suggest a shared emitting region. Our data are fully compatible with
radioactive Ni decay as the origin for cobalt and iron. We compare the
measured abundance ratios of iron and cobalt to theoretical predictions of
various SNIa explosion models. These models include, in addition to
Ni, different amounts of Ni and stable Fe. We can
exclude models that produced only Fe or only Ni in addition to
Ni. If we consider a model that has Ni, Ni, and
Fe then our data imply that these ratios are Fe / Ni
and Ni / Ni .Comment: 10 pages, 7 figures, Accepted for publication in A&
The Rising Light Curves of Type Ia Supernovae
We present an analysis of the early, rising light curves of 18 Type Ia
supernovae (SNe Ia) discovered by the Palomar Transient Factory (PTF) and the
La Silla-QUEST variability survey (LSQ). We fit these early data flux using a
simple power-law to determine the time of first
light , and hence the rise-time from first light to
peak luminosity, and the exponent of the power-law rise (). We find a mean
uncorrected rise time of days, with individual SN rise-times
ranging from to days. The exponent n shows significant
departures from the simple 'fireball model' of (or ) usually assumed in the literature. With a mean value of , our data also show significant diversity from event to event. This
deviation has implications for the distribution of 56Ni throughout the SN
ejecta, with a higher index suggesting a lesser degree of 56Ni mixing. The
range of n found also confirms that the 56Ni distribution is not standard
throughout the population of SNe Ia, in agreement with earlier work measuring
such abundances through spectral modelling. We also show that the duration of
the very early light curve, before the luminosity has reached half of its
maximal value, does not correlate with the light curve shape or stretch used to
standardise SNe Ia in cosmological applications. This has implications for the
cosmological fitting of SN Ia light curves.Comment: 19 pages, 19 figures, accepted for publication in MNRA
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A History of Trauma is Associated with Aggression, Depression, Non-Suicidal Self-Injury Behavior, and Suicide Ideation in First-Episode Psychosis.
The association between trauma and psychosis outcomes is well-established, and yet the impact of trauma on comorbid clinical symptoms-such as aggression, non-suicidal self-injury behavior (NSSIB), suicide ideation, and suicide behavior-for those with psychosis is unclear. To effectively treat those with first-episode psychosis (FEP) and a history of trauma, we need to understand the impact of trauma on their whole presentation. FEP participants were recruited from an Early Psychosis Program (N = 187, ages 12-35, 72.2% male). Clinicians gathered history of trauma, aggression, and suicide data, and rated current symptom severity and functioning. Data was coded using clinician rated measures, self-report measures, and retrospective clinical chart review. Regression analyses examined whether trauma was associated with a history of aggression, suicidal ideation, suicide behavior, NSSIB, symptoms, and functioning. Trauma was associated with aggression, aggression severity and type of aggression (aggression towards others). Trauma was also associated with depression severity, suicide ideation, most severe suicide ideation, and NSSIB. Trauma was not associated with suicide behavior, severity of suicide behavior or psychosocial functioning. Integrating trauma treatment into FEP care could reduce rates of depression, aggression, suicide ideation, and NSSIB for those with a history of trauma. To reduce suicide attempt occurrence and improve functioning, more research is needed
Intercellular Interactions in PC12 Cells Overexpressing Beta/A4 Amyloid
The amyloid precursor protein (APP) is an integral membrane component of eukaryotic cells. A variety of research approaches have addressed the contribution of the β amyloid peptide region of the APP to neuritic plaque structure and formation in the Alzheimer disease brain as well as the relationship between β amyloid accumulation and the occurrence of dementia. However, there is limited information available concerning the cellular consequences of amyloid deposition. The present studies were undertaken to investigate the relationship between β amyloid and intercellular junctions. Transfected PC12 cell lines, that overexpress the β amyloid peptide, exhibit structural and functional alterations at the cell surface and tend to form aggregates more readily than normal control cells. Intermediate junctions were the most common intercellular interactions of both normal and transfected cells. However, the control and transfected cells differed since areas of continuous and extensive junctions were readily seen in transfected cells and infrequently seen in control cells. The data suggest that excess accumulation of β amyloid is associated with the junctional apparatus and may be related to increased intercellular adhesion
Outcome following valve surgery in Australia: Development of an enhanced database module
Background: Valvular heart disease, including rheumatic heart disease (RHD), is an important cause of heart disease globally. Management of advanced disease can include surgery and other interventions to repair or replace affected valves. This article summarises the methodology of a study that will incorporate enhanced data collection systems to provide additional insights into treatment choice and outcome for advanced valvular disease including that due to RHD. Methods: An enhanced data collection system will be developed linking an existing Australian cardiac surgery registry to more detailed baseline co-morbidity, medication, echocardiographic and hospital separation data to identify predictors of morbidity and mortality outcome following valve surgery. Discussion: This project aims to collect and incorporate more detailed information regarding pre and postoperative factors and subsequent morbidity. We will use this to provide additional insights into treatment choice and outcome. © 2017 The Author(s)
Autobiographical memory: A candidate latent vulnerability mechanism for psychiatric disorder following childhood maltreatment
BACKGROUND: Altered autobiographical memory (ABM) functioning has been
implicated in the pathogenesis of depression and post-traumatic stress disorder and
may represent one mechanism by which childhood maltreatment elevates psychiatric
risk.
AIMS: To investigate the impact of childhood maltreatment on ABM functioning.
METHOD: Thirty-four children with documented maltreatment and 33 matched controls
recalled specific ABMs in response to emotionally-valenced cue words during
functional magnetic resonance imaging (fMRI).
RESULTS: Children with maltreatment experience showed reduced hippocampal and
increased middle temporal and para-hippocampal activation during positive ABM
recall compared to peers. During negative ABM recall they exhibited increased
amygdala activation, and greater amygdala connectivity with the salience network.
CONCLUSIONS: Childhood maltreatment is associated with altered ABM functioning,
specifically reduced activation in areas encoding specification of positive memories,
and greater activation of the salience network for negative memories. This pattern
may confer latent vulnerability to future depression and post-traumatic stress
disorder
CO_2 on Titan
A sharp stratospheric emission feature at 667 cm^(−1) in the Voyager infrared spectra of Titan is associated with the ν_2 Q branch of CO_2. A coupling of photochemical and radiative transfer theory yields an average mole fraction above the 110 mbar level of ƒCO_2 = 1.5 ± ^(1.5)_(0.8) x 10^(-9), with most of the uncertainty being due to imprecise knowledge of the vertical distribution. CO_2 is found to be in a steady state, with its abundance being regulated principally by the ∼72 K cold trap near the tropopause and secondarily by the rate at which water-bearing meteoritic material enters the top of the atmosphere. An influx of water about 0.4 times that at the top of the terrestrial atmosphere is consistent with a combination of the observed CO_2 abundance and a steady state CO mole fraction of 1.1×10^(−4); the theoretical value for CO is close to the value observed by Lutz et al. (1983), although there are large margins for error in both numbers. If steady state conditions for CO prevail, little information is available regarding the evolution of Titan's atmosphere
A multi-wavelength investigation of the radio-loud supernova PTF11qcj and its circumstellar environment
We present the discovery, classification, and extensive panchromatic (from
radio to X-ray) follow-up observations of PTF11qcj, a supernova discovered by
the Palomar Transient Factory. PTF11qcj is located at a distance of dL ~ 124
Mpc. Our observations with the Karl G. Jansky Very Large Array show that this
event is radio-loud: PTF11qcj reached a radio peak luminosity comparable to
that of the famous gamma-ray-burst-associated supernova 1998bw (L_{5GHz} ~
10^{29} erg/s/Hz). PTF11qcj is also detected in X-rays with the Chandra
observatory, and in the infrared band with Spitzer. Our multi-wavelength
analysis probes the supernova interaction with circumstellar material. The
radio observations suggest a progenitor mass-loss rate of ~10^{-4} Msun/yr x
(v_w/1000 km/s), and a velocity of ~(0.3-0.5)c for the fastest moving ejecta
(at ~10d after explosion). However, these estimates are derived assuming the
simplest model of supernova ejecta interacting with a smooth circumstellar
material characterized by radial power-law density profile, and do not account
for possible inhomogeneities in the medium and asphericity of the explosion.
The radio light curve shows deviations from such a simple model, as well as a
re-brightening at late times. The X-ray flux from PTF11qcj is compatible with
the high-frequency extrapolation of the radio synchrotron emission (within the
large uncertainties). An IR light echo from pre-existing dust is in agreement
with our infrared data. Our analysis of pre-explosion data from the Palomar
Transient Factory suggests that a precursor eruption of absolute magnitude M_r
~ -13 mag may have occurred ~ 2.5 yr prior to the supernova explosion. Based on
our panchromatic follow-up campaign, we conclude that PTF11qcj fits the
expectations from the explosion of a Wolf-Rayet star. Precursor eruptions may
be a feature characterizing the final pre-explosion evolution of such stars.Comment: 43 pages, 15 figures; this version matches the one published in ApJ
(includes minor changes that address the Referee's comments.
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