568 research outputs found
OBSERVATIONS ON NAVICULA THALLODES (BACILLARIOPHYCEAE), A BLADE-FORMING DIATOM FROM THE BERING SEA 1
A thallus-forming diatom, Navicula thallodes Proschkina-Lavrenko, previously known only from the original collection at Bering Island (U.S.S.R.), has been found at Amchitka Island in the Aleutians, Alaska. The most remarkable observation of the present report is that N. thallodes may form blades up to 50 cm long, which to our knowledge is the greatest length reported for a colonial diatom. SEM observations of this diatom are presented for the first time.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65176/1/j.1529-8817.1988.tb04487.x.pd
Mammal survival at the Cretaceous-Palaeogene boundary: metabolic homeostasis in prolonged tropical hibernation in tenrecs
Free-ranging common tenrecs, Tenrec ecaudatus, from sub-tropical Madagascar, displayed long-term (nine months) hibernation which lacked any evidence of periodic interbout arousals (IBAs). IBAs are the dominant feature of the mammalian hibernation phenotype and are thought to periodically restore long-term ischaemia damage and/or metabolic imbalances (depletions and accumulations). However, the lack of IBAs in tenrecs suggests no such pathology at hibernation T(b)s > 22°C. The long period of tropical hibernation that we report might explain how the ancestral placental mammal survived the global devastation that drove the dinosaurs and many other vertebrates to extinction at the CretaceousâPalaeogene boundary following a meteorite impact. The genetics and biochemistry of IBAs are of immense interest to biomedical researchers and space exploration scientists, in the latter case, those envisioning a hibernating state in astronauts for deep space travel. Unravelling the physiological thresholds and temperature dependence of IBAs will provide new impetus to these research quests
Detection of a possible multiphase ultra-fast outflow in IRAS 13349+2438 with NuSTAR and XMM-Newton
We present joint NuSTAR and XMM-Newton observations of the bright, variable
quasar IRAS 13349+2438. This combined dataset shows two clear iron absorption
lines at 8 and 9 keV, which are most likely associated with two layers of
mildly relativistic blueshifted absorption, with velocities of 0.14c and 0.27c.
We also find strong evidence for a series of Ly absorption lines at
intermediate energies in a stacked XMM-Newton EPIC-pn spectrum, at the same
blueshift as the lower velocity iron feature. This is consistent with a
scenario where an outflowing wind is radially stratified, so faster, higher
ionization material is observed closer to the black hole, and cooler, slower
material is seen from streamlines at larger radii.Comment: 5 pages, 2 figures, accepted for publication in MNRAS letter
The Hot and Energetic Universe: Astrophysics of feedback in local AGN
Understanding the astrophysics of feedback in active galactic nuclei (AGN) is
key to understanding the growth and co-evolution of supermassive black holes
and galaxies. AGN-driven winds/outflows are potentially the most effective way
of transporting energy and momentum from the nuclear scales to the host galaxy,
quenching star formation by sweeping away the gas reservoir. Key questions in
this field are: 1) how do accretion disks around black holes launch
winds/outflows, and how much energy do these carry? 2) How are the energy and
metals accelerated in winds/outflows transferred and deposited into the
circumgalactic medium? X-ray observations are a unique way to address these
questions because they probe the phase of the outflows which carries most of
the kinetic energy. We show how a high throughput, high spectral resolution
instrument like the X-ray Integral Field Unit (X-IFU) on Athena+ will allow us
to address these questions by determining the physical parameters (ionization
state, density, temperature, abundances, velocities, geometry, etc.) of the
outflows on a dynamical time-scale, in a broad sample of nearby bright AGN. The
X-IFU will also allow direct spectral imaging of the impact of these winds on
the host galaxy for local AGN, forming a template for understanding AGN at
higher redshifts where wind shocks cannot be resolved.Comment: Supporting paper for the science theme "The Hot and Energetic
Universe" to be implemented by the Athena+ X-ray observatory
(http://www.the-athena-x-ray-observatory.eu). 10 pages, 6 figure
The broad-band X-ray spectrum of the Seyfert 1 galaxy, MCG+8-11-11
We present a long (100 ks) Suzaku observation of one of the X-ray brightest
AGN, MCG+8-11-11. These data were complemented with the 54-month Swift BAT
spectrum, allowing us to perform a broad-band fit in the 0.6-150 keV range. The
fits performed in the 0.6-10 keV band give consistent results with respect to a
previous XMM-Newton observation, i.e. the lack of a soft excess, warm
absorption along the line of sight, a large Compton reflection component (R~1)
and the absence of a relativistic component of the neutral iron K
emission line. However, when the PIN and Swift BAT data are included, the
reflection amount drops significantly (R~0.2-0.3), and a relativistic iron line
is required, the latter confirmed by a phenomenological analysis in a
restricted energy band (3-10 keV). When a self-consistent model is applied to
the whole broadband data, the observed reflection component appears to be all
associated to the relativistic component of the iron K line. The
resulting scenario, though strongly model-dependent, requires that all the
reprocessing spectral components from Compton-thick material must be associated
to the accretion disc, and no evidence for the classical pc-scale torus is
found. The narrow core of the neutral iron K line is therefore produced
in a Compton-thin material, like the BLR, similarly to what found in another
Seyfert galaxy, NGC7213, but with the notable difference that MCG+8-11-11
presents spectral signatures from an accretion disc. The very low accretion
rate of NGC7213 could explain the lack of relativistic signatures in its
spectrum, but the absence of the torus in both sources is more difficult to
explain, since their luminosities are comparable, and their accretion rates are
completely different.Comment: 8 pages, 6 figure, accepted for publication in Astronomy and
Astrophysic
Development of an international standard set of outcome measures for patients with atrial fibrillation: a report of the International Consortium for Health Outcomes Measurement (ICHOM) atrial fibrillation working group.
AIMS: As health systems around the world increasingly look to measure and improve the value of care that they provide to patients, being able to measure the outcomes that matter most to patients is vital. To support the shift towards value-based health care in atrial fibrillation (AF), the International Consortium for Health Outcomes Measurement (ICHOM) assembled an international Working Group (WG) of 30 volunteers, including health professionals and patient representatives to develop a standardized minimum set of outcomes for benchmarking care delivery in clinical settings. METHODS AND RESULTS: Using an online-modified Delphi process, outcomes important to patients and health professionals were selected and categorized into (i) long-term consequences of disease outcomes, (ii) complications of treatment outcomes, and (iii) patient-reported outcomes. The WG identified demographic and clinical variables for use as case-mix risk adjusters. These included baseline demographics, comorbidities, cognitive function, date of diagnosis, disease duration, medications prescribed and AF procedures, as well as smoking, body mass index (BMI), alcohol intake, and physical activity. Where appropriate, and for ease of implementation, standardization of outcomes and case-mix variables was achieved using ICD codes. The standard set underwent an open review process in which over 80% of patients surveyed agreed with the outcomes captured by the standard set. CONCLUSION: Implementation of these consensus recommendations could help institutions to monitor, compare and improve the quality and delivery of chronic AF care. Their consistent definition and collection, using ICD codes where applicable, could also broaden the implementation of more patient-centric clinical outcomes research in AF
Ice XII in its second regime of metastability
We present neutron powder diffraction results which give unambiguous evidence
for the formation of the recently identified new crystalline ice phase[Lobban
et al.,Nature, 391, 268, (1998)], labeled ice XII, at completely different
conditions. Ice XII is produced here by compressing hexagonal ice I_h at T =
77, 100, 140 and 160 K up to 1.8 GPa. It can be maintained at ambient pressure
in the temperature range 1.5 < T < 135 K. High resolution diffraction is
carried out at T = 1.5 K and ambient pressure on ice XII and accurate
structural properties are obtained from Rietveld refinement. At T = 140 and 160
K additionally ice III/IX is formed. The increasing amount of ice III/IX with
increasing temperature gives an upper limit of T ~ 150 K for the successful
formation of ice XII with the presented procedure.Comment: 3 Pages of RevTeX, 3 tables, 3 figures (submitted to Physical Review
Letters
âYou canât start a car when thereâs no petrol leftâ: a qualitative study of patient, family and clinician perspectives on implantable cardioverter defibrillator deactivation
Objective: To explore the attitudes towards implantable cardioverter defibrillator (ICD) deactivation and initiation of deactivation discussions among patients, relatives and clinicians. Design: A multiphase qualitative study consisting of in situ hospital ICD clinic observations, and semistructured interviews of clinicians, patients and relatives. Data were analysed using a constant comparative approach. Setting: One tertiary and two district general hospitals in England. Participants: We completed 38 observations of hospital consultations prior to ICD implantation, and 80 interviews with patients, family members and clinicians between 2013 and 2015. Patients were recruited from preimplantation to postdeactivation. Clinicians included cardiologists, cardiac physiologists, heart failure nurses and palliative care professionals. Results: Four key themes were identified from the data: the current status of deactivation discussions; patientsâ perceptions of deactivation; who should take responsibility for deactivation discussions and decisions; and timing of deactivation discussions. We found that although patients and doctors recognised the importance of advance care planning, including ICD deactivation at an early stage in the patient journey, this was often not reflected in practice. The most appropriate clinician to take the lead was thought to be dependent on the context, but could include any appropriately trained member of the healthcare team. It was suggested that deactivation should be raised preimplantation and regularly reviewed. Identification of trigger points postimplantation for deactivation discussions may help ensure that these are timely and inappropriate shocks are avoided. Conclusions: There is a need for early, ongoing and evolving discussion between ICD recipients and clinicians regarding the eventual need for ICD deactivation. The most appropriate clinician to instigate deactivation discussions is likely to vary between patients and models of care. Reminders at key trigger points, and routine discussion of deactivation at implantation and during advance care planning could prevent distressing experiences for both the patient and their family at the end of life
Iron line profiles in Suzaku spectra of bare Seyfert galaxies
We methodically model the broad-band Suzaku spectra of a small sample of six
'bare' Seyfert galaxies: Ark 120, Fairall 9, MCG-02-14-009, Mrk 335, NGC 7469
and SWIFT J2127.4+5654. The analysis of bare Seyferts allows a consistent and
physical modelling of AGN due to a weak amount of any intrinsic warm
absorption, removing the degeneracy between the spectral curvature due to warm
absorption and the red-wing of the Fe K region. Through effective modelling of
the broad-band spectrum and investigating the presence of narrow neutral or
ionized emission lines and reflection from distant material, we obtain an
accurate and detailed description of the Fe K line region using models such as
laor, kerrdisk and kerrconv.
Results suggest that ionized emission lines at 6.7 keV and 6.97 keV
(particularly Fe XXVI) are relatively common and the inclusion of these lines
can greatly affect the parameters obtained with relativistic models i.e. spin,
emissivity, inner radius of emission and inclination. Moderately broad
components are found in all objects, but typically the emission originates from
tens of Rg, rather than within <6Rg of the black hole. Results obtained with
kerrdisk line profiles suggest an average emissivity of q~2.3 at intermediate
spin values with all objects ruling out the presence of a maximally spinning
black hole at the 90% confidence level. We also present new spin constraints
for Mrk 335 and NGC 7469 with intermediate values of a=0.70(+0.12,-0.01) and
a=0.69(+0.09,-0.09) respectively.Comment: 19 pages, 7 figures, 9 tables, MNRAS accepte
The flaring X-ray corona in the quasar PDS 456
New Swift monitoring observations of the variable, radio-quiet quasar, PDS 456, are presented. A bright X-ray flare was captured in 2018 September, the flux increasing by a factor of 4 and with a doubling time-scale of 2 d. From the light crossing argument, the coronal size is inferred to be âČ30 gravitational radii for a black hole mass of 109 Mâ and the total flare energy exceeds 1051 erg. A hardening of the X-ray emission accompanied the flare, with the photon index decreasing from Î = 2.2 to Î = 1.7 and back again. The flare is produced in the X-ray corona, the lack of any optical or UV variability being consistent with a constant accretion rate. Simultaneous XMM-Newton and NuSTAR observations were performed, 1-3 d after the flare peak and during the decline phase. These caught PDS 456 in a bright, bare state, where no disc wind absorption features are apparent. The hard X-ray spectrum shows a high energy roll-over, with an e-folding energy of keV. The deduced coronal temperature, of kT = 13 keV, is one of the coolest measured in any AGN and PDS 456 lies well below the predicted pair annihilation line in X-ray corona. The spectral variability, becoming softer when fainter following the flare, is consistent with models of cooling X-ray coronae. Alternatively, an increase in a non-thermal component could contribute towards the hard X-ray flare spectrum
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