205 research outputs found
The Enigmatic HH 255
To gain insight into the nature of the peculiar Herbig-Haro object HH 255
(also called Burnham's nebula), we use previously published observations to
derive information about the emission line fluxes as a function of position
within HH 255 and compare them with the well-studied, and relatively
well-behaved bow shock HH 1. There are some qualitative similarities in the
H and [O III] 5007 lines in both objects. However, in contrast to the
expectation of the standard bow shock model, the fluxes of the [O I] 6300, [S
II] 6731, and [N II] 6583 lines are essentially constant along the axis of the
flow, while the electron density decreases, over a large distance within HH
255.
We also explore the possibility that HH 255 represents the emission behind a
standing or quasi-stationary shock. The shock faces upwind, and we suggest,
using theoretical arguments, that it may be associated with the collimation of
the southern outflow from T Tauri. Using a simplified magnetohydrodynamic
simulation to illustrate the basic concept, we demonstrate that the existence
of such a shock at the north edge of HH 255 could indeed explain its unusual
kinematic and ionization properties. Whether or not such a shock can explain
the detailed emission line stratification remains an open question.Comment: Accepted by PASP, 12 pages including 8 figure
The Bell Theorem as a Special Case of a Theorem of Bass
The theorem of Bell states that certain results of quantum mechanics violate
inequalities that are valid for objective local random variables. We show that
the inequalities of Bell are special cases of theorems found ten years earlier
by Bass and stated in full generality by Vorob'ev. This fact implies precise
necessary and sufficient mathematical conditions for the validity of the Bell
inequalities. We show that these precise conditions differ significantly from
the definition of objective local variable spaces and as an application that
the Bell inequalities may be violated even for objective local random
variables.Comment: 15 pages, 2 figure
Beneficial effects of ivabradine in patients with heart failure, low ejection fraction, and heart rate above 77 b.p.m.
Aims:
Ivabradine has been approved in heart failure with reduced ejection fraction (HFrEF) and elevated heart rate despite guidelineâdirected medical therapy (GDMT) to reduce cardiovascular (CV) death and hospitalization for worsening HF. The median value of 77 b.p.m. is the lower bound selected for the regulatory approval in Canada, South Africa, and Australia. Patientâreported outcomes (PROs) including symptoms, quality of life, and global assessment are considered of major interest in the global plan of care of patients with HF. However, the specific impact of GDMT, and specifically ivabradine, on PRO remains poorly studied. In the subgroup of patients from the Systolic Heart failure treatment with the If inhibitor ivabradine Trial (SHIFT) who had heart rate above the median of 77 b.p.m. (preâspecified analysis) and for whom the potential for improvement was expected to be larger, we aimed (i) to evaluate the effects of ivabradine on PRO (symptoms, quality of life, and global assessment); (ii) to consolidate the effects of ivabradine on the primary composite endpoint of CV death and hospitalization for HF; and (iii) to reassess the effects of ivabradine on left ventricular (LV) remodelling.
Methods and results:
Comparisons were made according to therapy, and proportional hazards models (adjusted for baseline betaâblocker therapy) were used to estimate the association between ivabradine and various outcomes. In SHIFT, n = 3357 (51.6%) patients had a baseline heart rate > 77 b.p.m. After a median followâup of 22.9 months (interâquartile range 18â28 months), ivabradine on top of GDMT improved symptoms (28% vs. 23% improvement in New York Heart Association functional class, P = 0.0003), quality of life (5.3 vs. 2.2 improvement in Kansas City Cardiomyopathy Questionnaire overall summary score, P = 0.005), and global assessment [from both patient (improved in 72.3%) and physician (improved in 61.0%) perspectives] significantly more than did placebo (both P < 0.0001). Ivabradine induced a 25% reduction in the combined endpoint of CV death and hospitalization for HF (hazard ratio 0.75; P < 0.0001), which translates into a number of patients needed to be treated for 1 year of 17. Patients under ivabradine treatment demonstrated a significant reduction in LV dimensions when reassessed at 8 months (P < 0.05).
Conclusions:
In patients with chronic HFrEF, sinus rhythm, and a heart rate > 77 b.p.m. while on GDMT, the present analysis brings novel insights into the role of ivabradine in improving the management of HFrEF, particularly with regard to PRO (ISRCTN70429960)
Simulation-Based Investigation of a Model for the Interaction Between Stellar Magnetospheres and Circumstellar Accretion Disks
We examine, parametrically, the interaction between the magnetosphere of a
rotating, young stellar object (YSO) and a circumstellar accretion disk using
2.5-D (cylindrically symmetric) numerical magnetoydrodynamic simulations. The
interaction drives a collimated outflow, and we find that the jet formation
mechanism is robust. For variations in initial disk density of a factor of 16,
variations of stellar dipole strength of a factor of 4, and for various initial
conditions with respect to the disk truncation radius and the existence of a
disk field, outflows with similar morphologies were consistently produced.
Secondly, the system is self-regulating, where the outflow properties depend
relatively weakly on the parameters above. The large scale magnetic field
structure rapidly evolves to a configuration that removes angular momentum from
the disk at a rate that depends most strongly on the field and weakly on the
rotation rate of the foot-points of the field in the disk and the mass outflow
rate. Third, the simulated jets are episodic, with the timescale of jet
outbursts identical to the timescale of magnetically induced oscillations of
the inner edge of the disk. To better understand the physics controlling these
disk oscillations, we present a semi-analytical model and confirm that the
oscillation period is set by the spin down rate of the disk inner edge.
Finally, our simulations offer strong evidence that it is indeed the
interaction of the stellar magnetosphere with the disk, rather than some
primordial field in the disk itself, that is responsible for the formation of
jets from these systems.Comment: Accepted by ApJ; 34 pages, including 12 figures and 3 table
III Festival Internacional de MĂșsica : otoño 1965
De cada obra s'ha digitalitzat un programa sencer. De la resta s'han digitalitzat les parts que sĂłn diferents.DirecciĂł: Karl BohmEmpresa: Juan A. Pamia
Highly Collimated Molecular Hydrogen Jets Near IRAS 05487+0255: NIR Imaging and Spectroscopy
We present new narrow-band near-infrared images together with K band spectra
of highly collimated bipolar jets close to the IRAS 05487+0255 source. The jets
are located at 50" West of the Herbig-Haro 110 outflow. The jets are not
visible at optical wavelengths, and therefore, do not fall into the `standard'
Herbig-Haro object classification scheme. Nevertheless, they belong to an ever
growing group of molecular hydrogen jets associated with YSOs which are
optically undetected. The jets are very well collimated, with a length-to-width
ratio of 10-20. The spectra of the jet and counter-jet in the K-band show a
limited number of molecular hydrogen emission lines which makes it difficult to
obtain an accurate excitation temperature. We estimate Tex = 1104+/-67 K and
Tex = 920+/- 156 K for the red and blue jet components respectively. The radial
velocities of the jet and counter-jet, based on the shift of the (1,0) S(1)
2.121 micron line, are -275+/- 50 km/s and 180+/- 50 km/s respectively,
suggesting an angle of 30 to 45 degrees between the jet and the line of sight.
The molecular hydrogen emission of the entire jet extends for at least 40" or
0.1 pc at the distance of Orion. If the flow velocity is comparable to that of
the radial velocities, then the dynamical age of the system is quite short
(about 500 yrs), consistent with a young jet arising from an embedded source.
Entrainment in a turbulent mixing layer may explain this morphology and
spectral character.Comment: 15 pages, 5 postscript figures, Accepted to the Ap
Search for transient optical counterparts to high-energy IceCube neutrinos with Pan-STARRS1
In order to identify the sources of the observed diffuse high-energy neutrino
flux, it is crucial to discover their electromagnetic counterparts. IceCube
began releasing alerts for single high-energy ( TeV) neutrino
detections with sky localisation regions of order 1 deg radius in 2016. We used
Pan-STARRS1 to follow-up five of these alerts during 2016-2017 to search for
any optical transients that may be related to the neutrinos. Typically 10-20
faint ( mag) extragalactic transients are found within the
Pan-STARRS1 footprints and are generally consistent with being unrelated field
supernovae (SNe) and AGN. We looked for unusual properties of the detected
transients, such as temporal coincidence of explosion epoch with the IceCube
timestamp. We found only one transient that had properties worthy of a specific
follow-up. In the Pan-STARRS1 imaging for IceCube-160427A (probability to be of
astrophysical origin of 50 %), we found a SN PS16cgx, located at 10.0'
from the nominal IceCube direction. Spectroscopic observations of PS16cgx
showed that it was an H-poor SN at z = 0.2895. The spectra and light curve
resemble some high-energy Type Ic SNe, raising the possibility of a jet driven
SN with an explosion epoch temporally coincident with the neutrino detection.
However, distinguishing Type Ia and Type Ic SNe at this redshift is notoriously
difficult. Based on all available data we conclude that the transient is more
likely to be a Type Ia with relatively weak SiII absorption and a fairly normal
rest-frame r-band light curve. If, as predicted, there is no high-energy
neutrino emission from Type Ia SNe, then PS16cgx must be a random coincidence,
and unrelated to the IceCube-160427A. We find no other plausible optical
transient for any of the five IceCube events observed down to a 5
limiting magnitude of mag, between 1 day and 25 days after
detection.Comment: 20 pages, 6 figures, accepted to A&
Neutrinos below 100 TeV from the southern sky employing refined veto techniques to IceCube data
Many Galactic sources of gamma rays, such as supernova remnants, are expected
to produce neutrinos with a typical energy cutoff well below 100 TeV. For the
IceCube Neutrino Observatory located at the South Pole, the southern sky,
containing the inner part of the Galactic plane and the Galactic Center, is a
particularly challenging region at these energies, because of the large
background of atmospheric muons. In this paper, we present recent advancements
in data selection strategies for track-like muon neutrino events with energies
below 100 TeV from the southern sky. The strategies utilize the outer detector
regions as veto and features of the signal pattern to reduce the background of
atmospheric muons to a level which, for the first time, allows IceCube
searching for point-like sources of neutrinos in the southern sky at energies
between 100 GeV and several TeV in the muon neutrino charged current channel.
No significant clustering of neutrinos above background expectation was
observed in four years of data recorded with the completed IceCube detector.
Upper limits on the neutrino flux for a number of spectral hypotheses are
reported for a list of astrophysical objects in the southern hemisphere.Comment: 19 pages, 17 figures, 2 table
Interventions for treating wrist fractures in children:Review
© 2018 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd. Background: Wrist fractures, involving the distal radius, are the most common fractures in children. Most are buckle fractures, which are stable fractures, unlike greenstick and other usually displaced fractures. There is considerable variation in practice, such as the extent of immobilisation for buckle fractures and use of surgery for seriously displaced fractures. Objectives: To assess the effects (benefits and harms) of interventions for common distal radius fractures in children, including skeletally immature adolescents. Search methods: We searched the Cochrane Bone, Joint and Muscle Trauma Group's Specialised Register, the Cochrane Central Register of Controlled Trials, MEDLINE, Embase, trial registries and reference lists to May 2018. Selection criteria: We included randomised controlled trials (RCTs) and quasi-RCTs comparing interventions for treating distal radius fractures in children. We sought data on physical function, treatment failure, adverse events, time to return to normal activities (recovery time), wrist pain, and child (and parent) satisfaction. Data collection and analysis: At least two review authors independently performed study screening and selection, 'Risk of bias' assessment and data extraction. We pooled data where appropriate and used GRADE for assessing the quality of evidence for each outcome. Main results: Of the 30 included studies, 21 were RCTs, seven were quasi-RCTs and two did not describe their randomisation method. Overall, 2930 children were recruited. Typically, trials included more male children and reported mean ages between 8 and 10 years. Eight studies recruited buckle fractures, five recruited buckle and other stable fractures, three recruited minimally displaced fractures and 14 recruited displaced fractures, typically requiring closed reduction, typically requiring closed reduction. All studies were at high risk of bias, mainly reflecting lack of blinding. The studies made 14 comparisons. Below we consider five prespecified comparisons: Removable splint versus below-elbow cast for predominantly buckle fractures (6 studies, 695 children)One study (66 children) reported similar Modified Activities Scale for Kids - Performance scores (0 to 100; no disability) at four weeks (median scores: splint 99.04; cast 99.11); low-quality evidence. Thirteen children needed a change or reapplication of device (splint 5/225; cast 8/219; 4 studies); very low-quality evidence. One study (87 children) reported no refractures at six months. One study (50 children) found no between-group difference in pain during treatment; very low-quality evidence. Evidence was absent (recovery time), insufficient (children with minor complications) or contradictory (child or parent satisfaction). Two studies estimated lower healthcare costs for removable splints. Soft or elasticated bandage versus below-elbow cast for buckle or similar fractures (4 studies, 273 children)One study (53 children) reported more children had no or only limited disability at four weeks in the bandage group; very low-quality evidence. Eight children changed device or extended immobilisation for delayed union (bandage 5/90; cast 3/91; 3 studies); very low-quality evidence. Two studies (139 children) reported no serious adverse events at four weeks. Evidence was absent, insufficient or contradictory for recovery time, wrist pain, children with minor complications, and child and parent satisfaction. More bandage-group participants found their treatment convenient (39 children). Removal of casts at home by parents versus at the hospital fracture clinic by clinicians (2 studies, 404 children, mainly buckle fractures) One study (233 children) found full restoration of physical function at four weeks; low-quality evidence. There were five treatment changes (home 4/197; hospital 1/200; 2 studies; very low-quality evidence). One study found no serious adverse effects at six months (288 children). Recovery time and number of children with minor complications were not reported. There was no evidence of a difference in pain at four weeks (233 children); low-quality evidence. One study (80 children) found greater parental satisfaction in the home group; low-quality evidence. One UK study found lower healthcare costs for home removal. Below-elbow versus above-elbow casts for displaced or unstable both-bone fractures (4 studies, 399 children) Short-term physical function data were unavailable but very low-quality evidence indicated less dependency when using below-elbow casts. One study (66 children with minimally displaced both-bone fractures) found little difference in ABILHAND-Kids scores (0 to 42; no problems) (mean scores: below-elbow 40.7; above-elbow 41.8); very low-quality evidence. Overall treatment failure data are unavailable, but nine of the 11 remanipulations or secondary reductions (366 children, 4 studies) were in the above-elbow group; very low-quality evidence. There was no refracture or compartment syndrome at six months (215 children; 2 studies). Recovery time and overall numbers of children with minor complications were not reported. There was little difference in requiring physiotherapy for stiffness (179 children, 2 studies); very low-quality evidence. One study (85 children) found less pain at one week for below-elbow casts; low-quality evidence. One study found treatment with an above-elbow cast cost three times more in Nepal. Surgical fixation with percutaneous wiring and cast immobilisation versus cast immobilisation alone after closed reduction of displaced fractures (5 studies, 323 children) Where reported, above-elbow casts were used. Short-term functional outcome data were unavailable. One study (123 children) reported similar ABILHAND-Kids scores indicating normal physical function at six months (mean scores: surgery 41.9; cast only 41.4); low-quality evidence. There were fewer treatment failures, defined as early or problematic removal of wires or remanipulation for early loss in position, after surgery (surgery 20/124; cast only 41/129; 4 studies; very low-quality evidence). Similarly, there were fewer serious advents after surgery (surgery 28/124; cast only 43/129; 4 studies; very low-quality evidence). Recovery time, wrist pain, and satisfaction were not reported. There was lower referral for physiotherapy for stiffness after surgery (1 study); very low-quality evidence. One USA study found similar treatment costs in both groups. Authors' conclusions: Where available, the quality of the RCT-based evidence on interventions for treating wrist fractures in children is low or very low. However, there is reassuring evidence of a full return to previous function with no serious adverse events, including refracture, for correctly-diagnosed buckle fractures, whatever the treatment used. The review findings are consistent with the move away from cast immobilisation for these injuries. High-quality evidence is needed to address key treatment uncertainties; notably, some priority topics are already being tested in ongoing multicentre trials, such as FORCE
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