3,852 research outputs found
L1 and off Sun-Earth line visible-light imaging of Earth-directed CMEs: An analysis of inconsistent observations
The efficacy of coronal mass ejection (CME) observations as a key input to
space weather forecasting is explored by comparing on and off Sun-Earth line
observations from the ESA/NASA SOHO and NASA STEREO spacecraft. A comparison is
made of CME catalogues based on L1 coronagraph imagery and off Sun-Earth line
coronagraph and heliospheric imager (HI) observations, for the year 2011.
Analysis reveals inconsistencies in the identification of a number of
potentially Earth-directed CMEs. The catalogues reflect our ability to identify
and characterise CMEs, so any discrepancies can impact our prediction of
Earth-directed CMEs. We show that 15 CMEs, which were observed by STEREO, that
had estimated directions compatible with Earth-directed events, had no
identified halo/partial halo counterpart listed in the L1 coronagraph CME
catalogue. In-situ data confirms that for 9 of these there was a consistent L1
Interplanetary CME (ICME). The number of such "discrepant" events is
significant compared to the number of ICMEs recorded at L1 in 2011, stressing
the need to address space weather monitoring capabilities, particularly with
the inclusion of off Sun-Earth line observation. While the study provides
evidence that some halo CMEs are simply not visible in near-Earth coronagraph
imagery, there is evidence that some halo CMEs viewed from L1 are compromised
by preceding CME remnants or the presence of multiple-CMEs. This underlines (1)
the value of multiple vantage point CME observation, and (2) the benefit of off
Sun-Earth line platform heliospheric imaging, and coronagraph imaging, for the
efficient identification and tracking of Earth-directed events.Comment: 36 pages, 6 figures, in press at AGU Space Weather, 202
The cell adhesion molecule Fasciclin2 regulates brush border length and organization in Drosophila renal tubules
Multicellular organisms rely on cell adhesion molecules to coordinate cellâcell interactions, and to provide navigational cues during tissue formation. In Drosophila, Fasciclin 2 (Fas2) has been intensively studied due to its role in nervous system development and maintenance; yet, Fas2 is most abundantly expressed in the adult renal (Malpighian) tubule rather than in neuronal tissues. The role Fas2 serves in this epithelium is unknown. Here we show that Fas2 is essential to brush border maintenance in renal tubules of Drosophila. Fas2 is dynamically expressed during tubule morphogenesis, localizing to the brush border whenever the tissue is transport competent. Genetic manipulations of Fas2 expression levels impact on both microvilli length and organization, which in turn dramatically affect stimulated rates of fluid secretion by the tissue. Consequently, we demonstrate a radically different role for this well-known cell adhesion molecule, and propose that Fas2-mediated intermicrovillar homophilic adhesion complexes help stabilize the brush border
PopFor : A new model for estimating poplar yields
Yield and soil data for this project has been supplied by Rainer Schlepphorst, Holger Hartmann and Dieter Murach from HNEE, Germany, from the BIODEM project. Soil water and groundwater data were supplied by Markus Schmidt, HNEE, Germany. We would like to thank Shell and the University of Aberdeen CLSM for funding this work with a studentship. The MiscanFor modelling was supported by UK NERC ADVENT (NE/1806209) and FAB-GGR (NE/P019951/1) project funding.Peer reviewedPostprin
The C-Band All-Sky Survey: Instrument design, status, and first-look data
The C-Band All-Sky Survey (C-BASS) aims to produce sensitive, all-sky maps of
diffuse Galactic emission at 5 GHz in total intensity and linear polarization.
These maps will be used (with other surveys) to separate the several
astrophysical components contributing to microwave emission, and in particular
will allow an accurate map of synchrotron emission to be produced for the
subtraction of foregrounds from measurements of the polarized Cosmic Microwave
Background. We describe the design of the analog instrument, the optics of our
6.1 m dish at the Owens Valley Radio Observatory, the status of observations,
and first-look data.Comment: 10 pages, 11 figures, published in Proceedings of SPIE MIllimeter,
Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy V
(2010), Vol. 7741, 77411I-1 - 77411I-1
Protected percutaneous coronary intervention with Impella CP in a patient with left main disease, severe left ventricular systolic dysfunction and established hemolysis
bstract: The use of the Impella device in patients with left ventricular (LV) systolic impairment undergoing left main (LM) percutaneous coronary intervention (PCI) has been growing exponentially. Data from observational studies and registries demonstrate that Impella-assisted high-risk PCI is safe and effective with a low rate of peri-procedural complications. Hemolysis is a potential limitation of virtually all mechanical circulatory support devices and a small incidence of hemolysis has been associated with Impella use. The safety and feasibility of Impella use in patients with established hemolysis has not been previously evaluated. We report the first described case in the literature of Impella-assisted left main stem (LMS) PCI in a patient with severe LV systolic dysfunction and autoimmune hemolytic anemia (AIHA). Despite the patient's high bleeding risk (active hemolysis, thrombocytopenia, impaired renal function, use of steroids), Impella placement and PCI were successfully performed without complication. Haemoglobin, bilirubin and lactate dehydrogenase (LDH) levels were closely monitored peri-procedurally with no evidence of exacerbation of the patientâs hemolysis. We briefly discuss the mechanism of Impella-induced hemolysis and factors that can exacerbate hemolysis
On Sun-to-Earth Propagation of Coronal Mass Ejections
We investigate how coronal mass ejections (CMEs) propagate through, and
interact with, the inner heliosphere between the Sun and Earth, a key question
in CME research and space weather forecasting. CME Sun-to-Earth kinematics are
constrained by combining wide-angle heliospheric imaging observations,
interplanetary radio type II bursts and in situ measurements from multiple
vantage points. We select three events for this study, the 2012 January 19, 23,
and March 7 CMEs. Different from previous event studies, this work attempts to
create a general picture for CME Sun-to-Earth propagation and compare different
techniques for determining CME interplanetary kinematics. Key results are
obtained concerning CME Sun-to-Earth propagation. Our comparison between
different techniques (and data sets) also has important implications for CME
observations and their interpretations. Future CME observations and space
weather forecasting are discussed based on these results. See detail in the
PDF.Comment: ApJ, in pres
A Far-Ultraviolet Survey of 47 Tucanae.II The Long-Period Cataclysmic Variable AKO 9
We present time-resolved, far-ultraviolet (FUV) spectroscopy and photometry
of the 1.1 day eclipsing binary system AKO 9 in the globular cluster 47
Tucanae. The FUV spectrum of AKO 9 is blue and exhibits prominent C IV and He
II emission lines. The spectrum broadly resembles that of long-period,
cataclysmic variables in the galactic field.
Combining our time-resolved FUV data with archival optical photometry of 47
Tuc, we refine the orbital period of AKO 9 and define an accurate ephemeris for
the system. We also place constraints on several other system parameters, using
a variety of observational constraints. We find that all of the empirical
evidence is consistent with AKO 9 being a long-period dwarf nova in which mass
transfer is driven by the nuclear expansion of a sub-giant donor star. We
therefore conclude that AKO 9 is the first spectroscopically confirmed
cataclysmic variable in 47 Tuc.
We also briefly consider AKO 9's likely formation and ultimate evolution.
Regarding the former, we find that the system was almost certainly formed
dynamically, either via tidal capture or in a 3-body encounter. Regarding the
latter, we show that AKO 9 will probably end its CV phase by becoming a
detached, double WD system or by exploding in a Type Ia supernova.Comment: 40 pages, 11 figures, to appear in the Dec 20 issue of ApJ; minor
changes to match final published versio
Passage of Time in a Planck Scale Rooted Local Inertial Structure
It is argued that the `problem of time' in quantum gravity necessitates a
refinement of the local inertial structure of the world, demanding a
replacement of the usual Minkowski line element by a 4+2n dimensional
pseudo-Euclidean line element, with the extra 2n being the number of internal
phase space dimensions of the observed system. In the refined structure, the
inverse of the Planck time takes over the role of observer-independent
conversion factor usually played by the speed of light, which now emerges as an
invariant but derivative quantity. In the relativistic theory based on the
refined structure, energies and momenta turn out to be invariantly bounded from
above, and lengths and durations similarly bounded from below, by their
respective Planck scale values. Along the external timelike world-lines, the
theory naturally captures the `flow of time' as a genuinely structural
attribute of the world. The theory also predicts expected
deviations--suppressed quadratically by the Planck energy--from the dispersion
relations for free fields in the vacuum. The deviations from the special
relativistic Doppler shifts predicted by the theory are also suppressed
quadratically by the Planck energy. Nonetheless, in order to estimate the
precision required to distinguish the theory from special relativity, an
experiment with a binary pulsar emitting TeV range gamma-rays is considered in
the context of the predicted deviations from the second-order shifts.Comment: 17 pages; Diagram depicting "the objective flow of time" is replaced
with a much-improved diagra
X-Ray Searches for Emission from the WHIM in the Galactic Halo and the Intergalactic Medium
At least 50% of the baryons in the local universe are undetected and
predicted to be in a hot dilute phase (1E5-1E7 K) in low and moderate
overdensity environments. We searched for the predicted diffuse faint emission
through shadowing observations whereby cool foreground gas absorbs more distant
diffuse emission. Observations were obtained with Chandra and XMM-Newton. Using
the cold gas in two galaxies, NGC 891 and NGC 5907, shadows were not detected
and a newer observation of NGC 891 fails to confirm a previously reported X-ray
shadow. Our upper limits lie above model predictions. For Local Group studies,
we used a cloud in the Magellanic Stream and a compact high velocity cloud to
search for a shadow. Instead of a shadow, the X-ray emission was brighter
towards the Magellanic Stream cloud and there is a less significant brightness
enhancement toward the other cloud also. The brightness enhancement toward the
Magellanic Stream cloud is probably due to an interaction with a hot ambient
medium that surrounds the Milky Way. We suggest that this interaction drives a
shock into the cloud, heating the gas to X-ray emitting temperatures.Comment: 10 ApJ pages with 10 figure
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