1,150 research outputs found
The [alpha]-rays and the [alpha]-particle : a study of ionization and allied phenomena produced by [alpha]-rays
TypescriptTitle on piece contains symbol for alphaM.A. University of Missouri 1910As a result of experiments by M. Henri Beoquerel in 1896 we now know a certain class of chemical elements as Radio-active. A radio-active body gives off radiations that have the following effects: 1) they will affect a photographic plate; 2) they will excite phosphorescence in some substances; 3) the rays will ionize a gas thru which they pass. The study of the last and most important property has contributed most of our knowledge of radio-activity.Includes bibliographical reference
Oscillatory flow reactors (OFRs) for continuous manufacturing and crystallization
Continuous crystallization is an attractive approach for the delivery of consistent particles with specified critical quality attributes (CQAs), which are attracting increased interest for the manufacture of high value materials, including fine chemicals and pharmaceuticals. Oscillatory flow reactors (OFRs) offer a suitable platform to deliver consistent operating conditions under plug-flow operation while maintaining a controlled steady state. This review provides a brief overview of OFR technology before outlining the operating principles and summarizing applications, emphasizing the use for controlled continuous crystallization. While significant progress has been made to date, areas for further development are highlighted that will enhance the range of applications and ease of implementation of OFR technology. These depend on specific applications but include scale down, materials of construction suitable for chemical compatibility, encrustation mitigation, the enhancement of robust operation via automation, process analytical technology (PAT), and real-time feedback control
Fractional flow reserve vs. angiography in guiding management to optimize outcomes in non-ST-segment elevation myocardial infarction: the British Heart Foundation FAMOUS-NSTEMI randomized trial
Aim: We assessed the management and outcomes of non-ST segment elevation myocardial infarction (NSTEMI) patients randomly assigned to fractional flow reserve (FFR)-guided management or angiography-guided standard care.
Methods and results: We conducted a prospective, multicentre, parallel group, 1 : 1 randomized, controlled trial in 350 NSTEMI patients with ≥ coronary stenosis ≥30% of the lumen diameter assessed visually (threshold for FFR measurement) (NCT01764334). Enrolment took place in six UK hospitals from October 2011 to May 2013. Fractional flow reserve was disclosed to the operator in the FFR-guided group (n = 176). Fractional flow reserve was measured but not disclosed in the angiography-guided group (n = 174). Fractional flow reserve ≤0.80 was an indication for revascularization by percutaneous coronary intervention (PCI) or coronary artery bypass surgery (CABG). The median (IQR) time from the index episode of myocardial ischaemia to angiography was 3 (2, 5) days. For the primary outcome, the proportion of patients treated initially by medical therapy was higher in the FFR-guided group than in the angiography-guided group [40 (22.7%) vs. 23 (13.2%), difference 95% (95% CI: 1.4%, 17.7%), P = 0.022]. Fractional flow reserve disclosure resulted in a change in treatment between medical therapy, PCI or CABG in 38 (21.6%) patients. At 12 months, revascularization remained lower in the FFR-guided group [79.0 vs. 86.8%, difference 7.8% (−0.2%, 15.8%), P = 0.054]. There were no statistically significant differences in health outcomes and quality of life between the groups.
Conclusion: In NSTEMI patients, angiography-guided management was associated with higher rates of coronary revascularization compared with FFR-guided management. A larger trial is necessary to assess health outcomes and cost-effectiveness
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From Stalingrad to Grozny: Patriotism, political pressure, and literature in the war reporting of Vassily Grossman and Anna Politkovskaya
Comparing the work of the 20th century Soviet journalist and writer, Vassily Grossman, with that of his compatriot, Anna Politkovskaya, almost half a century later, this article examines the two journalists’ writing for what it tells us about the changing nature of Russian journalism, and reporter involvement in the coverage of war. Grossman was reporting on his country’s fight for survival in a war with Nazi Germany; Politkovskaya had no peer in her coverage of the bloodiest consequence of the collapse of that country, the Soviet Union: the wars in Chechnya. It also considers the literary nature of Grossman and Politkovskaya’s reporting. The article argues that the two journalists’ work has significance far beyond the time when they were reporting, and should therefore be more widely read and studied for what it tells us about covering conflict, and especially civilian suffering and, in the case of Politkovskaya, counter-insurgency
Sea-level constraints on the amplitude and source distribution of Meltwater Pulse 1A.
During the last deglaciation, sea levels rose as ice sheets retreated. This climate transition was punctuated by periods of more intense melting; the largest and most rapid of these—Meltwater Pulse 1A—occurred about 14,500 years ago, with rates of sea-level rise reaching approximately 4 m per century1, 2, 3. Such rates of rise suggest ice-sheet instability, but the meltwater sources are poorly constrained, thus limiting our understanding of the causes and impacts of the event4, 5, 6, 7. In particular, geophysical modelling studies constrained by tropical sea-level records1, 8, 9 suggest an Antarctic contribution of more than seven metres, whereas most reconstructions10 from Antarctica indicate no substantial change in ice-sheet volume around the time of Meltwater Pulse 1A. Here we use a glacial isostatic adjustment model to reinterpret tropical sea-level reconstructions from Barbados2, the Sunda Shelf3 and Tahiti1. According to our results, global mean sea-level rise during Meltwater Pulse 1A was between 8.6 and 14.6 m (95% probability). As for the melt partitioning, we find an allowable contribution from Antarctica of either 4.1 to 10.0 m or 0 to 6.9 m (95% probability), using two recent estimates11, 12 of the contribution from the North American ice sheets. We conclude that with current geologic constraints, the method applied here is unable to support or refute the possibility of a significant Antarctic contribution to Meltwater Pulse 1A
Continuum Halos in Nearby Galaxies -- an EVLA Survey (CHANG-ES) -- II: First Results on NGC 4631
We present the first results from the CHANG-ES survey, a new survey of 35
edge-on galaxies to search for both in-disk as well as extra-planar radio
continuum emission. The motivation and science case for the survey are
presented in a companion paper (Paper I). In this paper (Paper II), we outline
the observations and data reduction steps required for wide-band calibration
and mapping of EVLA data, including polarization, based on C-array test
observations of NGC 4631.
With modest on-source observing times (30 minutes at 1.5 GHz and 75 minutes
at 6 GHz for the test data) we have achieved best rms noise levels of 22 and
3.5 Jy beam at 1.5 GHz and 6 GHz, respectively. New disk-halo
features have been detected, among them two at 1.5 GHz that appear as loops in
projection. We present the first 1.5 GHz spectral index map of NGC 4631 to be
formed from a single wide-band observation in a single array configuration.
This map represents tangent slopes to the intensities within the band centered
at 1.5 GHz, rather than fits across widely separated frequencies as has been
done in the past and is also the highest spatial resolution spectral index map
yet presented for this galaxy. The average spectral index in the disk is
indicating that the emission is
largely non-thermal, but a small global thermal contribution is sufficient to
explain a positive curvature term in the spectral index over the band. Two
specific star forming regions have spectral indices that are consistent with
thermal emission. Polarization results (uncorrected for internal Faraday
rotation) are consistent with previous observations and also reveal some new
features. On broad scales, we find strong support for the notion that magnetic
fields constrain the X-ray emitting hot gas.Comment: Accepted to the Astronomical Journal, Version 2 changes: Added
acknowledgement to NRA
VLA-ANGST: A high-resolution HI Survey of Nearby Dwarf Galaxies
We present the "Very Large Array survey of Advanced Camera for Surveys Nearby
Galaxy Survey Treasury galaxies (VLA-ANGST)." VLA-ANGST is a National Radio
Astronomy Observatory Large Program consisting of high spectral (0.6-2.6 km/s)
and spatial (~6") resolution observations of neutral, atomic hydrogen (HI)
emission toward 35 nearby dwarf galaxies from the ANGST survey. ANGST is a
systematic HST survey to establish a legacy of uniform multi-color photometry
of resolved stars for a volume-limited sample of nearby galaxies (D\lesssim4
Mpc). VLA-ANGST provides VLA HI observations of the sub-sample of ANGST
galaxies with recent star formation that are observable from the northern
hemisphere and that were not observed in the "The HI Nearby Galaxy Survey"
(THINGS). The overarching scientific goal of VLA-ANGST is to investigate
fundamental characteristics of the neutral interstellar medium (ISM) of dwarf
galaxies. Here we describe the VLA observations, the data reduction, and the
final VLA-ANGST data products. We present an atlas of the integrated HI maps,
the intensity-weighted velocity fields, the second moment maps as a measure for
the velocity dispersion of the HI, individual channel maps, and integrated HI
spectra for each VLA-ANGST galaxy. We closely follow the observational setup
and data reduction of THINGS to achieve comparable sensitivity and angular
resolution. A major difference, however, is the high velocity resolution of the
VLA-ANGST observations (0.65 and 1.3km/s for the majority of the galaxies). The
VLA-ANGST data products are made publicly available at:
https://science.nrao.edu/science/surveys/vla-angst. With available star
formation histories from resolved stellar populations and lower resolution
ancillary observations from the FIR to the UV, VLA-ANGST will enable detailed
studies of the relationship between the ISM and star formation in dwarf
galaxies on a ~100 pc scale.Comment: 64 figures, grouped into 32. 115 pages, accepted for publication in
the Astronomical Journa
Interferometric imaging with the 32 element Murchison Wide-field Array
The Murchison Wide-field Array (MWA) is a low frequency radio telescope,
currently under construction, intended to search for the spectral signature of
the epoch of re-ionisation (EOR) and to probe the structure of the solar
corona. Sited in Western Australia, the full MWA will comprise 8192 dipoles
grouped into 512 tiles, and be capable of imaging the sky south of 40 degree
declination, from 80 MHz to 300 MHz with an instantaneous field of view that is
tens of degrees wide and a resolution of a few arcminutes. A 32-station
prototype of the MWA has been recently commissioned and a set of observations
taken that exercise the whole acquisition and processing pipeline. We present
Stokes I, Q, and U images from two ~4 hour integrations of a field 20 degrees
wide centered on Pictoris A. These images demonstrate the capacity and
stability of a real-time calibration and imaging technique employing the
weighted addition of warped snapshots to counter extreme wide field imaging
distortions.Comment: Accepted for publication in PASP. This is the draft before journal
typesetting corrections and proofs so does contain formatting and journal
style errors, also has with lower quality figures for space requirement
The Murchison Widefield Array
It is shown that the excellent Murchison Radio-astronomy Observatory site
allows the Murchison Widefield Array to employ a simple RFI blanking scheme and
still calibrate visibilities and form images in the FM radio band. The
techniques described are running autonomously in our calibration and imaging
software, which is currently being used to process an FM-band survey of the
entire southern sky.Comment: Accepted for publication in Proceedings of Science [PoS(RFI2010)016].
6 pages and 3 figures. Presented at RFI2010, the Third Workshop on RFI
Mitigation in Radio Astronomy, 29-31 March 2010, Groningen, The Netherland
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