1,024 research outputs found
The Diagnostic Potential of Transition Region Lines under-going Transient Ionization in Dynamic Events
We discuss the diagnostic potential of high cadence ultraviolet spectral data
when transient ionization is considered. For this we use high cadence UV
spectra taken during the impulsive phase of a solar flares (observed with
instruments on-board the Solar Maximum Mission) which showed excellent
correspondence with hard X-ray pulses. The ionization fraction of the
transition region ion O V and in particular the contribution function for the O
V 1371A line are computed within the Atomic Data and Analysis Structure, which
is a collection of fundamental and derived atomic data and codes which
manipulate them. Due to transient ionization, the O V 1371A line is enhanced in
the first fraction of a second with the peak in the line contribution function
occurring initially at a higher electron temperature than in ionization
equilibrium. The rise time and enhancement factor depend mostly on the electron
density. The fractional increase in the O V 1371A emissivity due to transient
ionization can reach a factor of 2--4 and can explain the fast response in the
line flux of transition regions ions during the impulsive phase of flares
solely as a result of transient ionization. This technique can be used to
diagnostic the electron temperature and density of solar flares observed with
the forth-coming Interface Region Imaging Spectrograph.Comment: 18 pages, 6 figure
The Therapeutic Efficacy of Domestic Violence Victim Interventions
Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline
ADAS analysis of the differential emission measure structure of the inner solar corona. II. A study of the `quiet Sun' inhomogeneities from SOHO CDS-NIS spectra
We present a study of the differential emission measure (DEM) of a `quiet
Sun' area observed in the extreme ultraviolet at normal incidence by the
Coronal Diagnostic Spectrometer (CDS) on the SOHO spacecraft. The data used for
this work were taken using the NISAT_S observing sequence. This takes the full
wavelength ranges from both the NIS channels (308-381 Angtr. and 513-633
Angst.) with the 2 arcsec by 240 arcsec slit, which is the narrowest slit
available, yielding the best spectral resolution. In this work we contrast the
DEM from subregions of 2 by 80 arcsec with that obtained from the mean
spectrum of the whole raster (20 by 240 arcsec). We find that the DEM
maintains essentially the same shape in the subregions, differing by a constant
factor between 0.5 and 2 from the mean DEM, except in areas were the electron
density is below cm and downflow velocities of 50 km/s
are found in the transition region. Such areas are likely to contain plasma
departing from ionisation equilibrium, violating the basic assumptions
underlying the DEM method. The comparison between lines of Li-like and Be-like
ions may provide further evidence of departure from ionisation equilibrium. We
find also that line intensities tend to be lower where velocities of the order
of 30 km/s or higher are measured in transition region lines. The DEM analysis
is also exploited to improve the line identification performed by Brooks et al
(1999) and to investigate possible elemental abundance variations from region
to region. We find that the plasma has composition close to photospheric in all
the subregions examined.Comment: 18 pages, 9 figures, 7 tables. Table 5 is available only online. A
copy of Table 5 can be found at http://webusers.ct.astro.it/acl/table5.dat.
The ReadMe file is at http://webusers.ct.astro.it/acl/ReadMe. Accepted by
Astronomy and Astrophysic
Australian human research ethics committee members' confidence in reviewing genomic research applications.
Human research ethics committees (HRECs) are evaluating increasing quantities of genomic research applications with complex ethical considerations. Genomic confidence is reportedly low amongst many non-genetics-experts; however, no studies have evaluated genomic confidence levels in HREC members specifically. This study used online surveys to explore genomic confidence levels, predictors of confidence, and genomics resource needs of members from 185 HRECs across Australia. Surveys were fully or partially completed by 145 members. All reported having postgraduate 94 (86%) and/or bachelor 15 (14%) degrees. Participants consisted mainly of researchers (n = 45, 33%) and lay members (n = 41, 30%), affiliated with either public health services (n = 73, 51%) or public universities (n = 31, 22%). Over half had served their HREC [Formula: see text]3 years. Fifty (44%) reviewed genomic studies [Formula: see text]3 times annually. Seventy (60%) had undertaken some form of genomic education. While most (94/103, 91%) had high genomic literacy based on familiarity with genomic terms, average genomic confidence scores (GCS) were moderate (5.7/10, n = 119). Simple linear regression showed that GCS was positively associated with years of HREC service, frequency of reviewing genomic applications, undertaking self-reported genomic education, and familiarity with genomic terms (p < 0.05 for all). Conversely, lay members and/or those relying on others when reviewing genomic studies had lower GCSs (p < 0.05 for both). Most members (n = 83, 76%) agreed further resources would be valuable when reviewing genomic research applications, and online courses and printed materials were preferred. In conclusion, even well-educated HREC members familiar with genomic terms lack genomic confidence, which could be enhanced with additional genomic education and/or resources
Paraunitary oversampled filter bank design for channel coding
Oversampled filter banks (OSFBs) have been considered for channel coding, since their redundancy can be utilised to permit the detection and correction of channel errors. In this paper, we propose an OSFB-based channel coder for a correlated additive Gaussian noise channel, of which the noise covariance matrix is assumed to be known. Based on a suitable factorisation of this matrix, we develop a design for the decoder's synthesis filter bank in order to minimise the noise power in the decoded signal, subject to admitting perfect reconstruction through paraunitarity of the filter bank. We demonstrate that this approach can lead to a significant reduction of the noise interference by exploiting both the correlation of the channel and the redundancy of the filter banks. Simulation results providing some insight into these mechanisms are provided
A new layout optimization technique for interferometric arrays, applied to the MWA
Antenna layout is an important design consideration for radio interferometers
because it determines the quality of the snapshot point spread function (PSF,
or array beam). This is particularly true for experiments targeting the 21 cm
Epoch of Reionization signal as the quality of the foreground subtraction
depends directly on the spatial dynamic range and thus the smoothness of the
baseline distribution. Nearly all sites have constraints on where antennas can
be placed---even at the remote Australian location of the MWA (Murchison
Widefield Array) there are rock outcrops, flood zones, heritages areas,
emergency runways and trees. These exclusion areas can introduce spatial
structure into the baseline distribution that enhance the PSF sidelobes and
reduce the angular dynamic range. In this paper we present a new method of
constrained antenna placement that reduces the spatial structure in the
baseline distribution. This method not only outperforms random placement
algorithms that avoid exclusion zones, but surprisingly outperforms random
placement algorithms without constraints to provide what we believe are the
smoothest constrained baseline distributions developed to date. We use our new
algorithm to determine antenna placements for the originally planned MWA, and
present the antenna locations, baseline distribution, and snapshot PSF for this
array choice.Comment: 12 pages, 6 figures, 1 table. Accepted for publication in MNRA
Ionization state, excited populations and emission of impurities in dynamic finite density plasmas: I. The generalized collisional-radiative model for light elements
The paper presents an integrated view of the population structure and its role in establishing the ionization state of light elements in dynamic, finite density, laboratory and astrophysical plasmas. There are four main issues, the generalized collisional-radiative picture for metastables in dynamic plasmas with Maxwellian free electrons and its particularizing to light elements, the methods of bundling and projection for manipulating the population equations, the systematic production/use of state selective fundamental collision data in the metastable resolved picture to all levels for collisonal-radiative modelling and the delivery of appropriate derived coefficients for experiment analysis. The ions of carbon, oxygen and neon are used in illustration. The practical implementation of the methods described here is part of the ADAS Project
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Scatter Loss From Environmental Degradation of KDP Crystals
Severe scattering losses from KDP crystals have been correlated with the exposure of porous sol AR coated crystals to ambient humidity. The scattering is attributed to formation of etch pits which develop under the coating on the KDP surface along crystallographic axes. This high angle scattering can in turn produce laser damage of downstream optics either through modulation of the beam or by optic contamination from ablation of adjacent metal structures. We have developed a simple tool to characterize the evolution of scatter from sol-coated KDP surfaces. We have measured the rate of etch pit formation as a function of relative humidity and surface treatment using both microscopy and scattering. We will discuss various surface treatments which can be utilized to retard or eliminate the environmental degradation of KDP crystals
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