462 research outputs found
Episodic absorption in the outflow of V603 Aquilae
We report on the time-dependent behaviour of ultraviolet spectral lines in Hubble Space Telescope Goddard High-Resolution Spectrograph data of the classical nova V603 Aql. In particular, episodic blueshifted absorption (extending to âŒâ2500 km sâ1) is present, with a variability time-scale down to âŒ1 min. The data provide a rare opportunity to study the rapid evolution of absorption structures that may be associated with accretion-disc winds in cataclysmic variables. At least three absorption events are recorded (at blueward velocities only) over âŒ5 h, each lasting âŒ10â15 min. The derived velocity, acceleration and optical depth properties provide an empirical picture of stochastically variable structures in the outflow, with no evidence for short-term (less than âŒ1 h) cyclic or modulated behaviour in the overall absorption properties. In contrast, the emission components of the ultraviolet resonance lines are very stable in velocity and strength in this low-inclination system. On at least two occasions there is an intriguing short-term âflareâ in the ultraviolet continuum flux (of up to âŒ40 per cent). Though there is no clear one-to-one relation in these data between the continuum fluctuations and the occurrence of the absorption events, the time-scales for the two variable phenomena are essentially the same. The irregular absorption episodes in the ultraviolet data of V603 Aql presently defy a clear physical interpretation. Their overall characteristics are discussed in the context of instabilities in radiation-pressure-driven disc winds
Taxonomy, biostratigraphy, and phylogeny of Oligocene Ciperoella n. gen.
Ciperoella Olsson and Hemleben n. gen. is
erected for Oligocene spinose species that have
a neogloboquadrinid-type wall texture and 4œ-5
similarly sized chambers in the final whorl. Four
species are recognized as distinct, namely Ciperoella anguliofficinalis (Blow), Ciperoella angulisuturalis
(Bolli), Ciperoella ciperoensis (Bolli), and Ciperoella
fariasi (BermĂșdez). Their taxonomy, phylogeny, and
biostratigraphy is discussed
Taxonomy, biostratigraphy, and phylogeny of Oligocene and lower Miocene Globoturborotalita
The taxonomy, phylogeny and biostratigraphy of
Oligocene and lower Miocene Globoturborotalita is
reviewed. Globoturborotalita is a long-ranging genus appearing in the basal Eocene and still present
in modern oceans with one living representative G.
rubescens. Species attributed to this genus are generally common and cosmopolitan. The following
species are recognized as valid: Globoturborotalita
barbula Pearson and Wade, Globoturborotalita bassriverensis Olsson and Hemleben, Globoturborotalita brazieri (Jenkins), Globoturborotalita cancellata
(Pessagno), Globoturborotalita connecta (Jenkins), Globoturborotalita eolabiacrassata Spezzaferri and
Coxall n. sp., Globoturborotalita euapertura (Jenkins), Globoturborotalita gnaucki (Blow and Banner), Globoturborotalita labiacrassata (Jenkins),
Globoturborotalita martini (Blow and Banner),
Globoturborotalita occlusa (Blow and Banner), Globoturborotalita ouachitaensis (Howe and Wallace),
Globoturborotalita paracancellata Olsson and Hemleben n. sp., Globoturborotalita pseudopraebulloides
Olsson and Hemleben n. sp., and Globoturborotalita
woodi (Jenkins)
Taxonomy, biostratigraphy, and phylogeny of Oligocene and lower Miocene Dentoglobigerina and Globoquadrina
The taxonomy, phylogeny, and biostratigraphy of
Oligocene and lower Miocene Dentoglobigerina
and Globoquadrina are reviewed. Because of the
discovery of spine holes in various species assigned
to these genera, the entire group is now considered to
have been fully or sparsely spinose in life and hence
part of Family Globigerinidae. One new species,
Dentoglobigerina eotripartita Pearson, Wade, and
Olsson n. sp., is named. Dentoglobigerina includes
forms with and without umbilical teeth and species
for which the presence or absence of a tooth is a
variable feature. A significant finding has been the
triple synonymy of Globigerina tripartita Koch,
Globigerina rohri Bolli, and Globoquadrina dehiscens
praedehiscens Blow, which greatly simplifies part of
the taxonomy. The genus Globoquadrina is restricted
to its type species, Globigerina dehiscens Chapman and
others. The following species from the time interval
of interest are regarded as valid: Dentoglobigerina altispira (Cushman and Jarvis), Dentoglobigerina
baroemoenensis (LeRoy), Dentoglobigerina
binaiensis (Koch), Dentoglobigerina eotripartita
Pearson, Wade, and Olsson n. sp., Dentoglobigerina
galavisi (BermĂșdez), Dentoglobigerina
globosa (Bolli), Dentoglobigerina globularis
(BermĂșdez), Dentoglobigerina juxtabinaiensis
Fox and Wade, Dentoglobigerina larmeui (Akers),
Dentoglobigerina prasaepis (Blow), Dentoglobigerina
pseudovenezuelana (Blow and Banner),
Dentoglobigerina sellii (Borsetti), Dentoglobigerina
taci Pearson and Wade, Dentoglobigerina tapuriensis
(Blow and Banner), Dentoglobigerina tripartita
(Koch), Dentoglobigerina venezuelana (Hedberg),
and Globoquadrina dehiscens (Chapman, Parr,
and Collins). The genus Dentoglobigerina also
comprises other Neogene/Quaternary species not
listed, including the living species Dentoglobigerina
cf. conglomerata (Schwager)
Taxonomy, biostratigraphy, and phylogeny of Oligocene and early Miocene Paragloborotalia and Parasubbotina
The taxonomy, phylogeny, and biostratigraphy of
Oligocene and early Miocene Paragloborotalia and
Parasubbotina are reviewed. The two genera are
closely related; Paragloborotalia was derived from
Parasubbotina in the early Eocene. Parasubbotina
was more diverse during the middle Eocene, while
Paragloborotalia experienced considerable diversification during the mid-Oligocene and in the latest
Oligocene-earliest Miocene. A significant finding has
been the synonymization of Globorotalia (Tuborotalia) mendacis Blow, and Turborotalia primitiva BrÓ§nnimann and Resig with Globorotalia birnageae Blow.
The following species from the time interval of interest are regarded as valid: Paragloborotalia acrostoma
(Wezel), Paragloborotalia birnageae (Blow), Paragloborotalia continuosa (Blow), Paragloborotalia
incognita (Walters) Paragloborotalia kugleri (Bolli),
Paragloborotalia mayeri (Cushman and Ellisor),
Paragloborotalia nana (Bolli), Paragloborotalia opima
(Bolli), Paragloborotalia pseudocontinuosa (Jenkins),
Paragloborotalia pseudokugleri (Blow), Paragloborotalia semivera (Hornibrook), Paragloborotalia siakensis (LeRoy), Parasubbotina hagni (Gohrbandt),
and Parasubbotina varianta (Subbotina).
Paragloborotalia is a long-lived group of
planktonic foraminifera that spanned the early Eocene to late Miocene and provided the root stock for
the evolution of multiple smooth, nonspinose, and
keeled globorotaliid lineages during the Neogene.
The early Oligocene forms of Paragloborotalia (nana,
opima, siakensis, pseudocontinuosa) have 4 or 5 globular chambers in the final whorl with radial spiral
sutures and a broadly rounded periphery. A trend
from radial to curved spiral sutures is observed in
late Oligocene and earliest Miocene lineages. Most
species of Paragloborotalia had wide distributions,
but some were more common in tropical to warm
subtropical waters (e.g., siakensis, kugleri) and were
especially dominant in the equatorial Pacific divergence zone (e.g., nana, opima, and pseudocontinuosa)
analogous to modern tropical upwelling Neogloboquadrina. Other species thrived in cool subtropical
and temperate waters (e.g., acrostoma, incognita)
Ferritins: furnishing proteins with iron
Ferritins are a superfamily of iron oxidation, storage and mineralization proteins found throughout the animal, plant, and microbial kingdoms. The majority of ferritins consist of 24 subunits that individually fold into 4-α-helix bundles and assemble in a highly symmetric manner to form an approximately spherical protein coat around a central cavity into which an iron-containing mineral can be formed. Channels through the coat at inter-subunit contact points facilitate passage of iron ions to and from the central cavity, and intrasubunit catalytic sites, called ferroxidase centers, drive Fe2+ oxidation and O2 reduction. Though the different members of the superfamily share a common structure, there is often little amino acid sequence identity between them. Even where there is a high degree of sequence identity between two ferritins there can be major differences in how the proteins handle iron. In this review we describe some of the important structural features of ferritins and their mineralized iron cores and examine in detail how three selected ferritins oxidise Fe2+ in order to explore the mechanistic variations that exist amongst ferritins. We suggest that the mechanistic differences reflect differing evolutionary pressures on amino acid sequences, and that these differing pressures are a consequence of different primary functions for different ferritins
The Expanding Fireball of Nova Delphini 2013
A classical nova occurs when material accreting onto the surface of a white
dwarf in a close binary system ignites in a thermonuclear runaway. Complex
structures observed in the ejecta at late stages could result from interactions
with the companion during the common envelope phase. Alternatively, the
explosion could be intrinsically bipolar, resulting from a localized ignition
on the surface of the white dwarf or as a consequence of rotational distortion.
Studying the structure of novae during the earliest phases is challenging
because of the high spatial resolution needed to measure their small sizes.
Here we report near-infrared interferometric measurements of the angular size
of Nova Delphini 2013, starting from one day after the explosion and continuing
with extensive time coverage during the first 43 days. Changes in the apparent
expansion rate can be explained by an explosion model consisting of an
optically thick core surrounded by a diffuse envelope. The optical depth of the
ejected material changes as it expands. We detect an ellipticity in the light
distribution, suggesting a prolate or bipolar structure that develops as early
as the second day. Combining the angular expansion rate with radial velocity
measurements, we derive a geometric distance to the nova of 4.54 +/- 0.59 kpc
from the Sun.Comment: Published in Nature. 32 pages. Final version available at
http://www.nature.com/nature/journal/v515/n7526/full/nature13834.htm
Long-term impact of community-based participatory women's groups on child and maternal mortality and child disability: follow-up of a cluster randomised trial in rural Nepal
Background: Community-based women's groups practising participatory learning and action (PLA) can reduce maternal and neonatal mortality in low-income countries. However, it is not clear whether these reductions are associated with subsequent increased or decreased rates of childhood death and disability. We assessed the impact on child deaths and disability beyond the perinatal period among participants in the earliest trial in Nepal 2001-2003. Methods: Household interviews were conducted with mothers or household heads. At cluster and individual levels, we analysed disability using pairwise log relative risks and survival using multilevel logistic models. Findings: From 6075 children and 6117 mothers alive at 4 weeks post partum, 44â419 children (73%) were available for interview a mean 11.5 years later. Rates of child deaths beyond the perinatal period were 36.6 and 52.0 per 1000 children in the intervention and control arms respectively. Rates of disability were 62.7 and 85.5 per 1000 children in the intervention and control arms respectively. Individual-level analysis, including random effects for cluster pairing and adjusted for baseline maternal literacy, socioeconomic status and maternal age, showed lower, statistically non-significant, odds of child deaths (OR 0.70 (95% CI 0.43 to 1.18) and disability (0.64 (0.39 to 1.06)) in the intervention arm. Conclusion: Community-level exposure to women's groups practising PLA did not significantly impact childhood death or disability or death beyond the perinatal period. Follow-up of other trials with larger sample sizes is warranted in order to explore the possibility of potential long-term survival and disability benefits with greater precision
X-Ray Spectroscopy of Stars
(abridged) Non-degenerate stars of essentially all spectral classes are soft
X-ray sources. Low-mass stars on the cooler part of the main sequence and their
pre-main sequence predecessors define the dominant stellar population in the
galaxy by number. Their X-ray spectra are reminiscent, in the broadest sense,
of X-ray spectra from the solar corona. X-ray emission from cool stars is
indeed ascribed to magnetically trapped hot gas analogous to the solar coronal
plasma. Coronal structure, its thermal stratification and geometric extent can
be interpreted based on various spectral diagnostics. New features have been
identified in pre-main sequence stars; some of these may be related to
accretion shocks on the stellar surface, fluorescence on circumstellar disks
due to X-ray irradiation, or shock heating in stellar outflows. Massive, hot
stars clearly dominate the interaction with the galactic interstellar medium:
they are the main sources of ionizing radiation, mechanical energy and chemical
enrichment in galaxies. High-energy emission permits to probe some of the most
important processes at work in these stars, and put constraints on their most
peculiar feature: the stellar wind. Here, we review recent advances in our
understanding of cool and hot stars through the study of X-ray spectra, in
particular high-resolution spectra now available from XMM-Newton and Chandra.
We address issues related to coronal structure, flares, the composition of
coronal plasma, X-ray production in accretion streams and outflows, X-rays from
single OB-type stars, massive binaries, magnetic hot objects and evolved WR
stars.Comment: accepted for Astron. Astrophys. Rev., 98 journal pages, 30 figures
(partly multiple); some corrections made after proof stag
Cardiovascular Response to Beta-Adrenergic Blockade or Activation in 23 Inbred Mouse Strains
We report the characterisation of 27 cardiovascular-related traits in 23 inbred mouse strains. Mice were phenotyped either in response to chronic administration of a single dose of the ÎČ-adrenergic receptor blocker atenolol or under a low and a high dose of the ÎČ-agonist isoproterenol and compared to baseline condition. The robustness of our data is supported by high trait heritabilities (typically H2>0.7) and significant correlations of trait values measured in baseline condition with independent multistrain datasets of the Mouse Phenome Database. We then focused on the drug-, dose-, and strain-specific responses to ÎČ-stimulation and ÎČ-blockade of a selection of traits including heart rate, systolic blood pressure, cardiac weight indices, ECG parameters and body weight. Because of the wealth of data accumulated, we applied integrative analyses such as comprehensive bi-clustering to investigate the structure of the response across the different phenotypes, strains and experimental conditions. Information extracted from these analyses is discussed in terms of novelty and biological implications. For example, we observe that traits related to ventricular weight in most strains respond only to the high dose of isoproterenol, while heart rate and atrial weight are already affected by the low dose. Finally, we observe little concordance between strain similarity based on the phenotypes and genotypic relatedness computed from genomic SNP profiles. This indicates that cardiovascular phenotypes are unlikely to segregate according to global phylogeny, but rather be governed by smaller, local differences in the genetic architecture of the various strains
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