253 research outputs found
Robust Chauvenet Outlier Rejection
Sigma clipping is commonly used in astronomy for outlier rejection, but the
number of standard deviations beyond which one should clip data from a sample
ultimately depends on the size of the sample. Chauvenet rejection is one of the
oldest, and simplest, ways to account for this, but, like sigma clipping,
depends on the sample's mean and standard deviation, neither of which are
robust quantities: Both are easily contaminated by the very outliers they are
being used to reject. Many, more robust measures of central tendency, and of
sample deviation, exist, but each has a tradeoff with precision. Here, we
demonstrate that outlier rejection can be both very robust and very precise if
decreasingly robust but increasingly precise techniques are applied in
sequence. To this end, we present a variation on Chauvenet rejection that we
call "robust" Chauvenet rejection (RCR), which uses three decreasingly
robust/increasingly precise measures of central tendency, and four decreasingly
robust/increasingly precise measures of sample deviation. We show this
sequential approach to be very effective for a wide variety of contaminant
types, even when a significant -- even dominant -- fraction of the sample is
contaminated, and especially when the contaminants are strong. Furthermore, we
have developed a bulk-rejection variant, to significantly decrease computing
times, and RCR can be applied both to weighted data, and when fitting
parameterized models to data. We present aperture photometry in a contaminated,
crowded field as an example. RCR may be used by anyone at
https://skynet.unc.edu/rcr, and source code is available there as well.Comment: 62 pages, 48 figures, 7 tables, accepted for publication in ApJ
The Prevalence of Secondary School Sport Safety Policies within State Athletic Associations and Legislation
Purpose: The location of secondary school health and safety policies impacts how they are implemented by the sports medicine team and stakeholders. Yet, a comprehensive list of each state’s policy locations has not been established. The purpose of this study was to describe where secondary school health and safety policies were located at the state level within the United States. Method: Emergency related health and safety policies were designated as either being located in the state high school athletics association (SHSAA), state legislation (LEGIS), or in both SHSAA and LEGIS (BOTH). Designation was determined by two researchers who independently reviewed each individual policy. Frequencies were tabulated for the leading causes of catastrophic injury (exertional heat stroke (EHS), traumatic head injuries (THI), sudden cardiac arrest (SCA), and emergency preparedness (EP)) for the distribution of policies emanating from SHSSA, LEGIS or BOTH. Prevalence ratios (PRs) with 95% confidence intervals (CIs) were calculated between the policies categories and location. Results: Most (99.35%) EHS and EP (83.02%) policies were found in SHSAA. Whereas the majority (79.70%) of SCA policies were found in LEGIS. Traumatic head injuries were most frequently observed in SHSAA, however, had the greatest distribution across all three categories (SHSAA=45.31%, LEGIS=25.52%, BOTH = 29.16%). The category that most frequently found policies in BOTH was THI (THI= 29.16%, all others =2.25%; PR=12.96; 95% CI=7.81, 21.53). Conclusions: Emergency related health and safety policies for secondary school sports are commonly found in SHSAA. TBI and SCA are also found in LEGIS. This demonstrates great variability of policy locations
Shear-Flow Driven Current Filamentation: Two-Dimensional Magnetohydrodynamic Simulations
The process of current filamentation in permanently externally driven,
initially globally ideal plasmas is investigated by means of two-dimensional
Magnetohydrodynamic (MHD)-simulations. This situation is typical for
astrophysical systems like jets, the interstellar and intergalactic medium
where the dynamics is dominated by external forces. Two different cases are
studied. In one case, the system is ideal permanently and dissipative processes
are excluded. In the second case, a system with a current density dependent
resistivity is considered. This resistivity is switched on self-consistently in
current filaments and allows for local dissipation due to magnetic
reconnection. Thus one finds tearing of current filaments and, besides, merging
of filaments due to coalescence instabilities. Energy input and dissipation
finally balance each other and the system reaches a state of constant magnetic
energy in time.Comment: 32 Pages, 13 Figures. accepted, to appear in Physics of Plasmas
(049012
Studies of the edge pedestal and behaviour of edge localised modes in improved H-mode and small-ELM regimes in ASDEX Upgrade
Magneto-optical trapping of bosonic and fermionic neon isotopes and their mixtures: isotope shift of the ^3P_2 to ^3D_3 transition and hyperfine constants of the ^3D_3 state of Ne-21
We have magneto-optically trapped all three stable neon isotopes, including
the rare Ne-21, and all two-isotope combinations. The atoms are prepared in the
metastable ^3P_2 state and manipulated via laser interaction on the ^3P_2 to
^3D_3} transition at 640.2nm. These cold (T = 1mK) and environmentally
decoupled atom samples present ideal objects for precision measurements and the
investigation of interactions between cold and ultracold metastable atoms. In
this work, we present accurate measurements of the isotope shift of the ^3P_2
to ^3D_3 transition and the hyperfine interaction constants of the ^3D_3 state
of Ne-21. The determined isotope shifts are (1625.9\pm0.15)MHz for Ne-20 to
Ne-22, (855.7\pm1.0)MHz for Ne-20 to Ne-21, and (770.3\pm1.0)MHz for Ne-21 to
Ne-22. The obtained magnetic dipole and electric quadrupole hyperfine
interaction constants are A(^3D_3)= (-142.4\pm0.2)MHz and
B(^3D_3)=(-107.7\pm1.1)MHz, respectively. All measurements give a reduction of
uncertainty by about one order of magnitude over previous measurements
Head-Tail Clouds: Drops to Probe the Diffuse Galactic Halo
A head-tail high-velocity cloud (HVC) is a neutral hydrogen halo cloud that
appears to be interacting with the diffuse halo medium as evident by its
compressed head trailed by a relatively diffuse tail. This paper presents a
sample of 116 head-tail HVCs across the southern sky (d < 2 deg) from the HI
Parkes All Sky Survey (HIPASS) HVC catalog, which has a spatial resolution of
15.5 arcmin (45 pc at 10 kpc) and a sensitivity of N_HI=2 x 10^(18) cm^(-2) (5
sigma). 35% of the HIPASS compact and semi-compact HVCs (CHVCs and :HVCs) can
be classified as head-tail clouds from their morphology. The clouds have
typical masses of 730 M_sun at 10 kpc (26,000 M_sun at 60 kpc) and the majority
can be associated with larger HVC complexes given their spatial and kinematic
proximity. This proximity, together with their similar properties to CHVCs and
:HVCs without head-tail structure, indicate the head-tail clouds have short
lifetimes, consistent with simulation predictions. Approximately half of the
head-tail clouds can be associated with the Magellanic System, with the
majority in the region of the Leading Arm with position angles pointing in the
general direction of the movement of the Magellanic System. The abundance in
the Leading Arm region is consistent with this feature being closer to the
Galactic disk than the Magellanic Stream and moving through a denser halo
medium. The head-tail clouds will feed the multi-phase halo medium rather than
the Galactic disk directly and provide additional evidence for a diffuse
Galactic halo medium extending to at least the distance of the Magellanic
Clouds.Comment: MNRAS Accepted, 10 figures, 7 in colo
Infrared seeded parametric four-wave mixing for sensitive detection of molecules
We have developed a sensitive resonant four-wave mixing technique based on two-photon parametric four-wave mixing with the addition of a phase matched ''seeder'' field. Generation of the seeder field via the same four-wave mixing process in a high pressure cell enables automatic phase matching to be achieved in a low pressure sample cell. This arrangement facilitates sensitive detection of complex molecular spectra by simply tuning the pump laser. We demonstrate the technique with the detection of nitric oxide down to concentrations more than 4 orders of magnitude below the capability of parametric four-wave mixing alone, with an estimated detection threshold of 10(12) molecules/cm(3)
The mbo Operon Is Specific and Essential for Biosynthesis of Mangotoxin in Pseudomonas syringae
Mangotoxin is an antimetabolite toxin produced by certain Pseudomonas syringae pv. syringae strains. This toxin is an oligopeptide that inhibits ornithine N-acetyl transferase, a key enzyme in the biosynthesis of ornithine and arginine. Previous studies have reported the involvement of the putative nonribosomal peptide synthetase MgoA in virulence and mangotoxin production. In this study, we analyse a new chromosomal region of P. syringae pv. syringae UMAF0158, which contains six coding sequences arranged as an operon (mbo operon). The mbo operon was detected in only mangotoxin-producing strains, and it was shown to be essential for the biosynthesis of this toxin. Mutants in each of the six ORFs of the mbo operon were partially or completely impaired in the production of the toxin. In addition, Pseudomonas spp. mangotoxin non-producer strains transformed with the mbo operon gained the ability to produce mangotoxin, indicating that this operon contains all the genetic information necessary for mangotoxin biosynthesis. The generation of a single transcript for the mbo operon was confirmed and supported by the allocation of a unique promoter and Rho-independent terminator. The phylogenetic analysis of the P. syringae strains harbouring the mbo operon revealed that these strains clustered together
Spirals of Spirituality: A Qualitative Study Exploring Dynamic Patterns of Spirituality in Turkish Organizations
This paper explores organizational spirituality, uncovers it as spiralling dynamics of both positive and negative potentialities, and proposes how leaders can shape these dynamics to improve the human conditions at the workplace. Based on case study of five Turkish organizations and drawing on the emerging discourse on spirituality in organizations literature, this study provides a deeper understanding of how dynamic patterns of spirituality operate in organizations. Insights from participant observation, organizational data, and semi-structured interviews yield three key themes of organizational spirituality: reflexivity, connectivity, and responsibility. Each of these themes has been found to be connected to upward spirals (inspiration, engagement, and calling) and downward spirals (incivility, silence, and fatigue). The study provides a detailed and holistic account of the individual and organizational processes through which spirituality is enacted both positively and negatively, exploring its dynamic and dualistic nature, as embodied in the fabric of everyday life and culture
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