859 research outputs found
Automated Coronal Hole Identification via Multi-Thermal Intensity Segmentation
Coronal holes (CH) are regions of open magnetic fields that appear as dark
areas in the solar corona due to their low density and temperature compared to
the surrounding quiet corona. To date, accurate identification and segmentation
of CHs has been a difficult task due to their comparable intensity to local
quiet Sun regions. Current segmentation methods typically rely on the use of
single EUV passband and magnetogram images to extract CH information. Here, the
Coronal Hole Identification via Multi-thermal Emission Recognition Algorithm
(CHIMERA) is described, which analyses multi-thermal images from the
Atmospheric Image Assembly (AIA) onboard the Solar Dynamics Observatory (SDO)
to segment coronal hole boundaries by their intensity ratio across three
passbands (171 \AA, 193 \AA, and 211 \AA). The algorithm allows accurate
extraction of CH boundaries and many of their properties, such as area,
position, latitudinal and longitudinal width, and magnetic polarity of
segmented CHs. From these properties, a clear linear relationship was
identified between the duration of geomagnetic storms and coronal hole areas.
CHIMERA can therefore form the basis of more accurate forecasting of the start
and duration of geomagnetic storms
Fastener starter tool
A fastener starter tool includes a number of spring retention fingers for retaining a small part, or combination of parts. The tool has an inner housing, which holds the spring retention fingers, a hand grip, and an outer housing configured to slide over the inner housing and the spring retention fingers toward and away from the hand grip, exposing and opening, or respectively, covering and closing, the spring retention fingers. By sliding the outer housing toward (away from) the hand grip, a part can be released from (retained by) the tool. The tool may include replaceable inserts, for retaining parts, such as screws, and configured to limit the torque applied to the part, to prevent cross threading. The inner housing has means to transfer torque from the hand grip to the insert. The tool may include replaceable bits, the inner housing having means for transferring torque to the replaceable bit
Kronian Magnetospheric Reconnection Statistics Across Cassini’s Lifetime
Magnetic reconnection is a fundamental physical process in planetary magnetospheres, in which plasma can be exchanged between the solar wind and a planetary magnetosphere, and material can be disconnected and ultimately lost from a magnetosphere. Magnetic reconnection in a planetary magnetotail can result in the release of plasmoids downtail and dipolarizations planetward of an x-line. The signatures of these products include characteristic deflections in the north-south component of the magnetic field which can be detected by in-situ spacecraft. These signatures have been identified by eye, semi-automated algorithms, and recently machine learning (ML) methods. Here, we apply statistical analysis to the most thorough catalog of Kronian magnetospheric reconnection signatures created through ML methods to improve understanding of magnetospheric evolution. This research concludes that no quasi-steady position of the magnetotail x-line exists within 70 (Formula presented.). This research introduces prediction equations to estimate the distribution of duration of plasmoid passage over the spacecraft ((Formula presented.), bin width = 1 min) and north-south field deflection ((Formula presented.), bin width = 0.25 nT) expected to be identified by an orbiting spacecraft across a year of observations. Furthermore, this research finds a local time asymmetry for reconnection identifications, with a preference for dusk-side over dawn-side. This may indicate a preference for Vasyliunas style reconnection over Dungey style for Saturn. Finally, through these distributions, the reconnection rate of Saturn’s magnetotail can be estimated as 3.22 reconnection events per day, with a resulting maximum mass loss from plasmoids of 44.87 kg (Formula presented.) on average, which is comparable with the magnetospheric mass loading from Enceladus (8–250 kg (Formula presented.))
ANSTO's centre for accelerator science a progress update
In 2009 the Australian Government announced that ANSTO would receive capital funding to develop a centre for accelerator science.
• Provide assurance that ANSTO can meet it’s AMS and IBA commitments for the Australian research community.
• Complements existing accelerator facilities at ANSTO and other accelerator labs in Australia
The Emerging Aversion to Inequality: Evidence from Poland 1992-2005
This paper provides an illustration of the changing tolerance for inequality in a context of radical political and economic transformation and rapid economic growth. We focus on the Polish experience of transition and explore self-declared attitudes of the citizens. Using monthly representative surveys of the population, realized by the Polish poll institute (CBOS) from 1992 to 2005, we identify a structural break in the relation between income inequality and subjective evaluation of well-being. The downturn in the tolerance for inequality (1997) coincides with the increasing distrust of political elites.http://deepblue.lib.umich.edu/bitstream/2027.42/64387/1/wp919.pd
TST positivity in household contacts of tuberculosis patients : a case-contact study in Malawi
This work was supported by a Wellcome Trust Fellowship awarded to DJ Sloan (086757/Z/08/A) a Malawi Liverpool Wellcome Trust (MLW) Core grant awarded by the Wellcome Trust and by a grant from the European Union Action for Diseases of Poverty Program (Sante–2006–105-061).Background: Screening household contacts of active tuberculosis (TB) patients is recommended for TB control. Due to resource constraints this rarely occurs in lower income countries. Demographic and clinical features of index cases may influence the likelihood of onwards TB transmission. It has also been proposed that accumulation of intracellular lipid bodies within M. tuberculosis cells may also enhance bacterial transmissibility. This study explored whether clinical and bacteriological observations recorded at baseline in TB cases in Malawi could help identify those with the highest risk of onwards transmission, to prioritise contact tracing. Methods: In this case-contact study, data on clinical presentation, sputum bacterial load and the percentage of lipid body positive acid-fast bacilli (%LB + AFB) on sputum smears were recorded in adults with sputum smear and culture positive pulmonary TB before initiation of therapy. The Tuberculin Skin Test (TST) was used to detect infection with M. tuberculosis amongst household contacts under the age of 15 years. TST positivity of the child contacts was related to characteristics of the index case. Results: Thirty four index cases brought 56 contacts (median: 1, range: 1–4 contacts each). 37 (66%) of contacts had a positive TST. Cavities or a high percentage of lung affected on index patient CXRs were associated with TST positivity. Multivariate analysis of non-radiological factors showed that male sex, HIV-negative status and raised peripheral blood white blood count (WBC) in index patients were also independent risk factors of TST positivity. Lower %LB + AFB counts were associated with TST positivity on univariate analysis only. Conclusion: TST positivity is common amongst household contacts of sputum smear positive adult TB patients in Malawi. Contact tracing in this high risk population could be guided by prioritising index cases with CXR cavities and extensive radiological disease or, in the absence of CXRs, those who are HIV-negative with a raised WBC.Publisher PDFPeer reviewe
The relative contribution of climate to changes in lesser prairie-chicken abundance
Citation: Ross, B. E., Haukos, D., Hagen, C., & Pitman, J. (2016). The relative contribution of climate to changes in lesser prairie-chicken abundance. Ecosphere, 7(6), 11. doi:10.1002/ecs2.1323Managing for species using current weather patterns fails to incorporate the uncertainty associated with future climatic conditions; without incorporating potential changes in climate into conservation strategies, management and conservation efforts may fall short or waste valuable resources. Understanding the effects of climate change on species in the Great Plains of North America is especially important, as this region is projected to experience an increased magnitude of climate change. Of particular ecological and conservation interest is the lesser prairie-chicken (Tympanuchus pallidicinctus), which was listed as "threatened" under the U.S. Endangered Species Act in May 2014. We used Bayesian hierarchical models to quantify the effects of extreme climatic events (extreme values of the Palmer Drought Severity Index [PDSI]) relative to intermediate (changes in El Nino Southern Oscillation) and long-term climate variability (changes in the Pacific Decadal Oscillation) on trends in lesser prairie-chicken abundance from 1981 to 2014. Our results indicate that lesser prairie-chicken abundance on leks responded to environmental conditions of the year previous by positively responding to wet springs (high PDSI) and negatively to years with hot, dry summers (low PDSI), but had little response to variation in the El Nino Southern Oscillation and the Pacific Decadal Oscillation. Additionally, greater variation in abundance on leks was explained by variation in site relative to broad-scale climatic indices. Consequently, lesser prairie-chicken abundance on leks in Kansas is more strongly influenced by extreme drought events during summer than other climatic conditions, which may have negative consequences for the population as drought conditions intensify throughout the Great Plains
Symmetry breaking in crossed magnetic and electric fields
We present the first observations of cylindrical symmetry breaking in highly
excited diamagnetic hydrogen with a small crossed electric field, and we give a
semiclassical interpretation of this effect. As the small perpendicular
electric field is added, the recurrence strengths of closed orbits decrease
smoothly to a minimum, and revive again. This phenomenon, caused by
interference among the electron waves that return to the nucleus, can be
computed from the azimuthal dependence of the classical closed orbits.Comment: 4 page REVTeX file including 5 postscript files (using psfig)
Accepted for publication in Physical Review Letters. Difference from earlier
preprint: we have discovered the cause of the earlier apparent discrepancy
between experiment and theory and now achieve excellent agreemen
Forecasting the Probability of Large Rates of Change of the Geomagnetic Field in the UK: Timescales, Horizons and Thresholds
Large Geomagnetically Induced Currents (GICs) pose a risk to ground based infrastructure such as power networks. Large GICs may be induced when the rate of change of the ground magnetic field is significantly elevated. We assess the ability of three different machine learning model architectures to process the time history of the incoming solar wind and provide a probabilistic forecast as to whether the rate of change of the ground magnetic field will exceed specific high thresholds at a location in the UK. The three models tested represent feed forward, convolutional and recurrent neural networks.
We find all three models are reliable and skillful, with Brier skill scores, ROC scores and PR scores of approximately 0.25, 0.95 and 0.45, respectively. When evaluated during two example magnetospheric storms we find that all scores increase significantly, indicating that the models work better during active intervals. The models perform excellently through the majority of the storms, however they do not fully capture the ground response around the initial sudden commencements. We attribute this to the use of propagated solar wind data not allowing the models notice to forecast impulsive phenomenon.
Increasing the volume of solar wind data provided to the models does not produce appreciable increases in model performance, possibly due to the fixed model structures and limited training data. However, increasing the horizon of the forecast from 30 minutes to 3 hours increases the performance of the models, presumably as the models need not be as precise about timing
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