127 research outputs found
Evidence for a Compact Wolf-Rayet Progenitor for the Type Ic Supernova PTF 10vgv
We present the discovery of PTF 10vgv, a Type Ic supernova (SN) detected by the Palomar Transient Factory, using the Palomar 48 inch telescope (P48). R-band observations of the PTF 10vgv field with P48 probe the SN emission from its very early phases (about two weeks before R-band maximum) and set limits on its flux in the week prior to the discovery. Our sensitive upper limits and early detections constrain the post-shock-breakout luminosity of this event. Via comparison to numerical (analytical) models, we derive an upper-limit of R ≾ 4.5 R_☉ (R ≾ 1 R_☉) on the radius of the progenitor star, a direct indication in favor of a compact Wolf-Rayet star. Applying a similar analysis to the historical observations of SN 1994I yields R ≾ 1/4 R_☉ for the progenitor radius of this SN
Market segmentation strategies for complex automotive products
With the advent of 'big data', the purpose of this empirical study was to take the opportunity to rethink conventional market segmentation strategies. This is particularly relevant for the automotive industry which is going through a period of rapid change with advanced technologies such as electric powered and autonomous vehicles, creating increased concerns as to how this complexity is communicated effectively. A mixed methods approach was utilised to collect data from multiple sources, incorporating in-depth discussion groups, semi-structured interviews, an online survey, and data collection of communication processes through the attendance of new car product launches. The results suggest that marketing departments should rethink their data capture methods to collect more relevant consumer information, not the contemporary trend of needs, attitude, and motivation variables that are difficult to identify and collect, but basic information on their level of familiarity with products through previous experience and exposure. The basic dimensions identified are characterised by a consumer's expertise, involvement, and familiarity with a product. The findings are synthesised into a theoretical framework to define differing levels of product complexity, which would enable manufacturers to provide more closely defined market segmentation strategies when communicating new product information
Very Early Ultraviolet and Optical Observations of the Type Ia Supernova 2009ig
Supernova (SN) 2009ig was discovered 17 hours after explosion by the Lick
Observatory Supernova Search, promptly classified as a normal Type Ia SN (SN
Ia), peaked at V = 13.5 mag, and was equatorial, making it one of the foremost
supernovae for intensive study in the last decade. Here, we present ultraviolet
(UV) and optical observations of SN 2009ig, starting about 1 day after
explosion until around maximum brightness. Our data include excellent UV and
optical light curves, 25 premaximum optical spectra, and 8 UV spectra,
including the earliest UV spectrum ever obtained of a SN Ia. SN 2009ig is a
relatively normal SN Ia, but does display high-velocity ejecta - the ejecta
velocity measured in our earliest spectra (v ~ -23,000 km/s for Si II 6355) is
the highest yet measured in a SN Ia. The spectral evolution is very dramatic at
times earlier than 12 days before maximum brightness, but slows after that
time. The early-time data provide a precise measurement of 17.13 +/- 0.07 days
for the SN rise time. The optical color curves and early-time spectra are
significantly different from template light curves and spectra used for
light-curve fitting and K-corrections, indicating that the template light
curves and spectra do not properly represent all Type Ia supernovae at very
early times. In the age of wide-angle sky surveys, SNe like SN 2009ig that are
nearby, bright, well positioned, and promptly discovered will still be rare. As
shown with SN 2009ig, detailed studies of single events can provide
significantly more information for testing systematic uncertainties related to
SN Ia distance estimates and constraining progenitor and explosion models than
large samples of more distant SNe.Comment: 16 pages, 14 figures, ApJ, in pres
Smoke gets in your eyes: re-reading gender in the "nostalgia film"
Upon its release, American Graffiti (George Lucas, 1973) was much admired by critics and audiences alike. Yet, in subsequent years, the film became known for its supposed “flattening of history,” and celebration of patriarchal values. This article demonstrates that such a judgement owes much to Fredric Jameson’s historically contingent work on postmodernism, which argues that American Graffiti constitutes the paradigmatic nostalgia film. In contrast, using close textual analysis, I demonstrate that American Graffiti provides a more complex construction of the past, and of gender, than has hitherto been acknowledged. Far from blindly idealising the early 1960s, the film interrogates the processes through which the period and its gender relations come to be idealised. This article has consequences not only for our understanding of Lucas’ seminal film, but also for the American New Wave, and the “nostalgia” text
Observational and Physical Classification of Supernovae
This chapter describes the current classification scheme of supernovae (SNe).
This scheme has evolved over many decades and now includes numerous SN Types
and sub-types. Many of these are universally recognized, while there are
controversies regarding the definitions, membership and even the names of some
sub-classes; we will try to review here the commonly-used nomenclature, noting
the main variants when possible. SN Types are defined according to
observational properties; mostly visible-light spectra near maximum light, as
well as according to their photometric properties. However, a long-term goal of
SN classification is to associate observationally-defined classes with specific
physical explosive phenomena. We show here that this aspiration is now finally
coming to fruition, and we establish the SN classification scheme upon direct
observational evidence connecting SN groups with specific progenitor stars.
Observationally, the broad class of Type II SNe contains objects showing strong
spectroscopic signatures of hydrogen, while objects lacking such signatures are
of Type I, which is further divided to numerous subclasses. Recently a class of
super-luminous SNe (SLSNe, typically 10 times more luminous than standard
events) has been identified, and it is discussed. We end this chapter by
briefly describing a proposed alternative classification scheme that is
inspired by the stellar classification system. This system presents our
emerging physical understanding of SN explosions, while clearly separating
robust observational properties from physical inferences that can be debated.
This new system is quantitative, and naturally deals with events distributed
along a continuum, rather than being strictly divided into discrete classes.
Thus, it may be more suitable to the coming era where SN numbers will quickly
expand from a few thousands to millions of events.Comment: Extended final draft of a chapter in the "SN Handbook". Comments most
welcom
Juvenile obesity and its association with utilisation and costs of pharmaceuticals - results from the KiGGS study
<p>Abstract</p> <p>Background</p> <p>According to a national reference, 15% of German children and adolescents are overweight (including obese) and 6.3% are obese. An earlier study analysed the impact of childhood overweight and obesity on different components of direct medical costs (physician, hospital and therapists). To complement the existing literature for Germany, this study aims to explore the association of body mass index (BMI) with utilisation of pharmaceuticals and related costs in German children and adolescents.</p> <p>Methods</p> <p>Based on data from 14, 836 respondents aged 3-17 years in the German Interview and Examination Survey for Children and Adolescents (KiGGS), drug intake and associated costs were estimated using a bottom-up approach. To investigate the association of BMI with utilisation and costs, univariate analyses and multivariate generalised mixed models were conducted.</p> <p>Results</p> <p>There was no significant difference between BMI groups regarding the probability of drug utilisation. However, the number of pharmaceuticals used was significantly higher (14%) for obese children than for normal weight children. Furthermore, there was a trend for more physician-prescribed medication in obese children and adolescents. Among children with pharmaceutical intake, estimated costs were 24% higher for obese children compared with the normal weight group.</p> <p>Conclusions</p> <p>This is the first study to estimate excess drug costs for obesity based on a representative cross-sectional sample of the child and adolescent population in Germany. The results suggest that obese children should be classified as a priority group for prevention. This study complements the existing literature and provides important information concerning the relevance of childhood obesity as a health problem.</p
Spectra of Hydrogen-poor Superluminous Supernovae from the Palomar Transient Factory
Most Type I superluminous supernovae (SLSNe-I) reported to date have been identified by their high peak luminosities and spectra lacking obvious signs of hydrogen. We demonstrate that these events can be distinguished from normal-luminosity SNe (including Type Ic events) solely from their spectra over a wide range of light-curve phases. We use this distinction to select 19 SLSNe-I and four possible SLSNe-I from the Palomar Transient Factory archive (including seven previously published objects). We present 127 new spectra of these objects and combine these with 39 previously published spectra, and we use these to discuss the average spectral properties of SLSNe-I at different spectral phases. We find that Mn II most probably contributes to the ultraviolet spectral features after maximum light, and we give a detailed study of the O II features that often characterize the early-time optical spectra of SLSNe-I. We discuss the velocity distribution of O II, finding that for some SLSNe-I this can be confined to a narrow range compared to relatively large systematic velocity shifts. Mg II and Fe II favor higher velocities than O II and C II, and we briefly discuss how this may constrain power-source models. We tentatively group objects by how well they match either SN 2011ke or PTF12dam and discuss the possibility that physically distinct events may have been previously grouped together under the SLSN-I label
Patterns of subregional cerebellar atrophy across epilepsy syndromes: An ENIGMA-Epilepsy study
\ua9 2024 The Authors. Epilepsia published by Wiley Periodicals LLC on behalf of International League Against Epilepsy.Objective: The intricate neuroanatomical structure of the cerebellum is of longstanding interest in epilepsy, but has been poorly characterized within the current corticocentric models of this disease. We quantified cross-sectional regional cerebellar lobule volumes using structural magnetic resonance imaging in 1602 adults with epilepsy and 1022 healthy controls across 22 sites from the global ENIGMA-Epilepsy working group. Methods: A state-of-the-art deep learning-based approach was employed that parcellates the cerebellum into 28 neuroanatomical subregions. Linear mixed models compared total and regional cerebellar volume in (1) all epilepsies, (2) temporal lobe epilepsy with hippocampal sclerosis (TLE-HS), (3) nonlesional temporal lobe epilepsy, (4) genetic generalized epilepsy, and (5) extratemporal focal epilepsy (ETLE). Relationships were examined for cerebellar volume versus age at seizure onset, duration of epilepsy, phenytoin treatment, and cerebral cortical thickness. Results: Across all epilepsies, reduced total cerebellar volume was observed (d =.42). Maximum volume loss was observed in the corpus medullare (dmax =.49) and posterior lobe gray matter regions, including bilateral lobules VIIB (dmax =.47), crus I/II (dmax =.39), VIIIA (dmax =.45), and VIIIB (dmax =.40). Earlier age at seizure onset ((Formula presented.) =.05) and longer epilepsy duration ((Formula presented.) =.06) correlated with reduced volume in these regions. Findings were most pronounced in TLE-HS and ETLE, with distinct neuroanatomical profiles observed in the posterior lobe. Phenytoin treatment was associated with reduced posterior lobe volume. Cerebellum volume correlated with cerebral cortical thinning more strongly in the epilepsy cohort than in controls. Significance: We provide robust evidence of deep cerebellar and posterior lobe subregional gray matter volume loss in patients with chronic epilepsy. Volume loss was maximal for posterior subregions implicated in nonmotor functions, relative to motor regions of both the anterior and posterior lobe. Associations between cerebral and cerebellar changes, and variability of neuroanatomical profiles across epilepsy syndromes argue for more precise incorporation of cerebellar subregional damage into neurobiological models of epilepsy
Pre-Stimulus Activity Predicts the Winner of Top-Down vs. Bottom-Up Attentional Selection
Our ability to process visual information is fundamentally limited. This leads to competition between sensory information that is relevant for top-down goals and sensory information that is perceptually salient, but task-irrelevant. The aim of the present study was to identify, from EEG recordings, pre-stimulus and pre-saccadic neural activity that could predict whether top-down or bottom-up processes would win the competition for attention on a trial-by-trial basis. We employed a visual search paradigm in which a lateralized low contrast target appeared alone, or with a low (i.e., non-salient) or high contrast (i.e., salient) distractor. Trials with a salient distractor were of primary interest due to the strong competition between top-down knowledge and bottom-up attentional capture. Our results demonstrated that 1) in the 1-sec pre-stimulus interval, frontal alpha (8–12 Hz) activity was higher on trials where the salient distractor captured attention and the first saccade (bottom-up win); and 2) there was a transient pre-saccadic increase in posterior-parietal alpha (7–8 Hz) activity on trials where the first saccade went to the target (top-down win). We propose that the high frontal alpha reflects a disengagement of attentional control whereas the transient posterior alpha time-locked to the saccade indicates sensory inhibition of the salient distractor and suppression of bottom-up oculomotor capture
A very luminous magnetar-powered supernova associated with an ultra-long gamma-ray burst
A new class of ultra-long duration (>10,000 s) gamma-ray bursts has recently been suggested1,2,3. They may originate in the explosion of stars with much larger radii than normal long gamma-ray bursts3,4 or in the tidal disruptions of a star3. No clear supernova had yet been associated with an ultra-long gamma-ray burst. Here we report that a supernova (2011kl) was associated with the ultra-long duration burst 111209A, at z=0.677. This supernova is more than 3 times more luminous than type Ic supernovae associated with long gamma-ray bursts5,6,7, and its spectrum is distinctly different. The continuum slope resembles those of super-luminous supernovae8,9, but extends farther down into the rest-frame ultra-violet implying a low metal content. The light curve evolves much more rapidly than super-luminous supernovae. The combination of high luminosity and low metal-line opacity cannot be reconciled with typical type Ic supernovae, but can be reproduced by a model where extra energy is injected by a strongly magnetized neutron star (a magnetar), which has also been proposed as the explanation for super-luminous supernovae20,20a
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