83 research outputs found
Comparing Soil Boundaries Delineated by Digital Analysis of Multispectral Scanner Data from High and Low Spatial Resolution Systems
Aircraft and Landsat data were used with computer-aided techniques to delineate soils patterns of a field of 40 ha in a transition zone between soils developed under deciduous forest and those developed under prairie vegetation. Two computer-aided classification techniques, supervised and nonsupervised, were employed in classifying soils of the study area. The means and covariance matrix statistics were obtained for every cluster or soil class through the statistics algorithm. Each cluster of aircraft and Landsat data was identified and assigned to a specific soil type by correlating the cluster soil patterns with a standard soils map of the test site which was prepared as a part of the ground observation task. A sampling grid plan was used to select a training set for a supervised classification of the aircraft MSS data. The spectral soil patterns revealed in the classifications from aircraft and satellite MSS data resembled the general patterns of the soils of the conventionally prepared soil map. The spatial resolution of the aircraft scanner was adequate to recognize each soil type boundary in the test site. However, the limited spatial resolution of the satellite scanner made it difficult to delineate those soil features with widths less than the spatial resolution of the scanner. On the contrary those soil patterns which were broad enough to exceed the spatial resolution of the Landsat scanner were delineated very well
The Temperature, Electron, and Pressure Characteristics of Switchbacks: Parker Solar Probe Observations
Parker Solar Probe (PSP) observes unexpectedly prevalent switchbacks, which
are rapid magnetic field reversals that last from seconds to hours, in the
inner heliosphere, posing new challenges to understanding their nature, origin,
and evolution. In this work, we investigate the thermal states, electron pitch
angle distributions, and pressure signatures of both inside and outside
switchbacks, separating a switchback into spike, transition region (TR), and
quiet period (QP). Based on our analysis, we find that the proton temperature
anisotropies in TRs seem to show an intermediate state between spike and QP
plasmas. The proton temperatures are more enhanced in spike than in TR and QP,
but the alpha temperatures and alpha-to-proton temperature ratios show the
opposite trends, implying that the preferential heating mechanisms of protons
and alphas are competing in different regions of switchbacks. Moreover, our
results suggest that the electron integrated intensities are almost the same
across the switchbacks but the electron pitch angle distributions are more
isotropic inside than outside switchbacks, implying switchbacks are intact
structures but strong scattering of electrons happens inside switchbacks. In
addition, the examination of pressures reveals that the total pressures are
comparable through a switchback, confirming switchbacks are pressure-balanced
structures. These characteristics could further our understanding of ion
heating, electron scattering, and the structure of switchbacks.Comment: submitted to Ap
The Structure and Origin of Switchbacks: Parker Solar Probe Observations
Switchbacks are rapid magnetic field reversals that last from seconds to
hours. Current Parker Solar Probe (PSP) observations pose many open questions
in regards to the nature of switchbacks. For example, are they stable as they
propagate through the inner heliosphere, and how are they formed? In this work,
we aim to investigate the structure and origin of switchbacks. In order to
study the stability of switchbacks, we suppose the small scale current sheets
therein may work to braid and stabilize the switchbacks. Thus, we use the
partial variance of increments method to identify the small scale current
sheets, and then compare their distributions in switchbacks. With more than one
thousand switchbacks identified with PSP observations in seven encounters, we
find many more current sheets inside than outside switchbacks, indicating that
these micro-structures should work to stabilize the S-shape structures of
switchbacks. Additionally, with the helium measurements, we study the
variations of helium abundance ratios and alpha-proton differential speeds to
trace switchbacks to their origins. We find both helium-rich and helium-poor
populations in switchbacks, implying the switchbacks could originate from both
closed and open magnetic field regions in the Sun. Moreover, we observe that
the alpha-proton differential speeds also show complex variations as compared
to the local Alfv\'en speed. The joint distributions of both parameters show
that low helium abundance together with low differential speed is the dominant
state in switchbacks. The presence of small scale current sheets in switchbacks
along with the helium features are in line with the hypothesis that switchbacks
could originate from the Sun via interchange reconnection process. However,
other formation mechanisms are not excluded
Source and Propagation of a Streamer Blowout Coronal Mass Ejection Observed by the Parker Solar Probe
Parker Solar Probe Observations of High Plasma Beta Solar Wind from Streamer Belt
In general, slow solar wind from the streamer belt forms a high plasma beta
equatorial plasma sheet around the heliospheric current sheet (HCS) crossing,
namely the heliospheric plasma sheet (HPS). Current Parker Solar Probe (PSP)
observations show that the HCS crossings near the Sun could be full or partial
current sheet crossing (PCS), and they share some common features but also have
different properties. In this work, using the PSP observations from encounters
4 to 10, we identify streamer belt solar wind from enhancements in plasma beta,
and we further use electron pitch angle distributions to separate it into HPS
solar wind that around the full HCS crossings and PCS solar wind that in the
vicinity of PCS crossings. Based on our analysis, we find that the PCS solar
wind has different characteristics as compared with HPS solar wind: a) PCS
solar wind could be non-pressure-balanced structures rather than magnetic
holes, and the total pressure enhancement mainly results from the less reduced
magnetic pressure; b) some of the PCS solar wind are mirror unstable; c) PCS
solar wind is dominated by very low helium abundance but varied alpha-proton
differential speed. We suggest the PCS solar wind could originate from coronal
loops deep inside the streamer belt, and it is pristine solar wind that still
actively interacts with ambient solar wind, thus it is valuable for further
investigations on the heating and acceleration of slow solar wind
Recommended from our members
Track A Basic Science
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138319/1/jia218438.pd
SIVagm Infection in Wild African Green Monkeys from South Africa: Epidemiology, Natural History, and Evolutionary Considerations
Pathogenesis studies of SIV infection have not been performed to date in wild monkeys due to difficulty in collecting and storing samples on site and the lack of analytical reagents covering the extensive SIV diversity. We performed a large scale study of molecular epidemiology and natural history of SIVagm infection in 225 free-ranging AGMs from multiple locations in South Africa. SIV prevalence (established by sequencing pol, env, and gag) varied dramatically between infant/juvenile (7%) and adult animals (68%) (p<0.0001), and between adult females (78%) and males (57%). Phylogenetic analyses revealed an extensive genetic diversity, including frequent recombination events. Some AGMs harbored epidemiologically linked viruses. Viruses infecting AGMs in the Free State, which are separated from those on the coastal side by the Drakensberg Mountains, formed a separate cluster in the phylogenetic trees; this observation supports a long standing presence of SIV in AGMs, at least from the time of their speciation to their Plio-Pleistocene migration. Specific primers/probes were synthesized based on the pol sequence data and viral loads (VLs) were quantified. VLs were of 104-106 RNA copies/ml, in the range of those observed in experimentally-infected monkeys, validating the experimental approaches in natural hosts. VLs were significantly higher (107-108 RNA copies/ml) in 10 AGMs diagnosed as acutely infected based on SIV seronegativity (Fiebig II), which suggests a very active transmission of SIVagm in the wild. Neither cytokine levels (as biomarkers of immune activation) nor sCD14 levels (a biomarker of microbial translocation) were different between SIV-infected and SIV-uninfected monkeys. This complex algorithm combining sequencing and phylogeny, VL quantification, serology, and testing of surrogate markers of microbial translocation and immune activation permits a systematic investigation of the epidemiology, viral diversity and natural history of SIV infection in wild African natural hosts. © 2013 Ma et al
ARIA digital anamorphosis : Digital transformation of health and care in airway diseases from research to practice
Digital anamorphosis is used to define a distorted image of health and care that may be viewed correctly using digital tools and strategies. MASK digital anamorphosis represents the process used by MASK to develop the digital transformation of health and care in rhinitis. It strengthens the ARIA change management strategy in the prevention and management of airway disease. The MASK strategy is based on validated digital tools. Using the MASK digital tool and the CARAT online enhanced clinical framework, solutions for practical steps of digital enhancement of care are proposed.Peer reviewe
- …