18,511 research outputs found
Penumbral micro-jets at high spatial and temporal resolution
Sunspot observations in chromospheric spectral lines have revealed the
existence of short-lived linear bright transients, commonly referred to as
penumbral micro-jets (PMJs). Details on the origin and physical nature of PMJs
are to large extend still unkown. We aim to characterize the dynamical nature
of PMJs to provide guidance for future modelling efforts. We analyze high
spatial (0.1 arcsec) and temporal resolution (1 s) Ca II H filtergram (0.1 nm
bandwidth) observations of a sunspot obtained on two consecutive days with the
Swedish 1-m Solar Telescope. We find that PMJs appear to be the rapid
brightening of an already existing (faint) fibril. The rapid brightening is the
fast increase (typically less than 10 s) in intensity over significant length
(several 100s of km) of the existing fibril. For most PMJs, we cannot identify
a clear root or source from where the brightening appears to originate. After
the fast onset, about half of the PMJs have a top that is moving with an
apparent velocity between 5 and 14 km/s, most of them upwards. For the other
PMJs, there is no significant motion of the top. For about a third of the PMJs
we observe a splitting into two parallel and co-evolving linear features during
the later phases of the lifetime of the PMJ. We conclude that mass flows can
play only limited role in the onset phase of PMJs and that it is more likely
that we see the effect of a fast heating front.Comment: Accepted for publication in Astronomy & Astrophysics. Movies are
available at http://folk.uio.no/rouppe/pmj_highcadence
The quiet chromosphere. Old wisdom, new insights, future needs
The introduction to this review summarizes chromosphere observation in two
figures. The first part showcases the historical emphasis on the eclipse
chromosphere in the development of NLTE line formation theory and criticizes 1D
modeling. The second part advertises recent breakthroughs after many decades of
standstill. The third part discusses what may or should come next.Comment: To appear in Proceedings 25th NSO Workshop, editors A. Tritschler, K.
Reardon, H. Uitenbroek, Mem. Soc. Astr. Ita
Examining Water Quality along Cozine Creek
Water is an essential resource for all life. Water sustains ecological processes that are important to the survival of fish, vegetation, wetlands, and birds. It contributes to humans by providing drinking water, irrigation, and also is an inspiration for recreational, cultural, and spiritual practices. Anthropogenic activities affect water quality in various ways, and a significant portion of the human population is currently experiencing water stress. The quality of water, as well as its social and economic value, share a positive relationship. Therefore, as water quality becomes degraded by pollution, the environmental, social, and economic value also decrease. The recognition of the importance of safe water has created crucial policies in the United States and internationally.
Our study looks specifically into the water quality of Cozine Creek, located in Yamhill County, Oregon. The goal of our study was to determine how water quality variables compared among our sampling sites in 2017 and across the years from 2011 to 2017. We used the definition of water quality as determined by measuring physical, chemical, and biological characteristics. We measured dissolved oxygen (DO), biochemical oxygen demand (BOD), pH, temperature, flow, turbidity, macroinvertebrates, bacterial counts, nutrients, and surrounding vegetation. To present a better understanding to the measurements of the water quality variables, we compared the measurements to the scientifically known parameters of healthy salmonid habitat, since the presence of salmon indicates a healthy watershed. Our data suggest that the overall quality of our three sites along Cozine Creek is poor, and there was little to no improvement of water quality when compared to previous years\u27 data. It is likely that the water quality can be attributed to agricultural and urban runoff possibly containing waste, storm water, pesticides, fertilizer, and other chemicals
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Scoping Review of the development of artificial eyes throughout the years
Losing an eye following trauma can lead to profound psychosocial difficulties making it imperative for the wearer to be fitted with an aesthetically pleasing custom-made artificial eye. Despite recent technological advancements, current design and manufacturing processes have remained unchanged in over 55 years. With the aim of portraying current knowledge regarding the development of artificial eyes in order to aid future development, a scooping review was conducted. Six online search engines were used: Scopus, PubMed, MedLine Complete, Web of Science, Science Direct and Google Scholar. Thirty-eight articles met the inclusion criteria and underwent numerical and thematic analysis with three thematic themes emerging. History and the current process of artificial eyes has been well documented, however, the impact of wearing artificial eyes is sparse. On-going research and development into the design and manufacturing processes of artificial eyes and the psychosocial impact of wearing an artificial eye is needed
Chromospheric counterparts of solar transition region unresolved fine structure loops
Low-lying loops have been discovered at the solar limb in transition region
temperatures by the Interface Region Imaging Spectrograph (IRIS). They do not
appear to reach coronal temperatures, and it has been suggested that they are
the long-predicted unresolved fine structures (UFS). These loops are dynamic
and believed to be visible during both heating and cooling phases. Making use
of coordinated observations between IRIS and the Swedish 1-m Solar Telescope,
we study how these loops impact the solar chromosphere. We show for the first
time that there is indeed a chromospheric signal of these loops, seen mostly in
the form of strong Doppler shifts and a conspicuous lack of chromospheric
heating. In addition, we find that several instances have a inverse Y-shaped
jet just above the loop, suggesting that magnetic reconnection is driving these
events. Our observations add several puzzling details to the current knowledge
of these newly discovered structures; this new information must be considered
in theoretical models.Comment: 5 pages, 3 figures, 2 movies; accepted for publication in A&A Letter
Thermal and non-thermal emission in the Cygnus X region
Radio continuum observations detect non-thermal synchrotron and thermal
bremsstrahlung radiation. Separation of the two different emission components
is crucial to study the properties of diffuse interstellar medium. The Cygnus X
region is one of the most complex areas in the radio sky which contains a
number of massive stars and HII regions on the diffuse thermal and non-thermal
background. More supernova remnants are expected to be discovered. We aim to
develop a method which can properly separate the non-thermal and thermal radio
continuum emission and apply it to the Cygnus X region. The result can be used
to study the properties of different emission components and search for new
supernova remnants in the complex. Multi-frequency radio continuum data from
large-scale surveys are used to develop a new component separation method.
Spectral analysis is done pixel by pixel for the non-thermal synchrotron
emission with a realistic spectral index distribution and a fixed spectral
index of beta = -2.1 for the thermal bremsstrahlung emission. With the new
method, we separate the non-thermal and thermal components of the Cygnus X
region at an angular resolution of 9.5arcmin. The thermal emission component is
found to comprise 75% of the total continuum emission at 6cm. Thermal diffuse
emission, rather than the discrete HII regions, is found to be the major
contributor to the entire thermal budget. A smooth non-thermal emission
background of 100 mK Tb is found. We successfully make the large-extent known
supernova remnants and the HII regions embedded in the complex standing out,
but no new large SNRs brighter than Sigma_1GHz = 3.7 x 10^-21 W m^-2 Hz^-1
sr^-1 are found.Comment: 9 pages, 5 figures, accepted by A&A. The quality of the figures is
reduced due to file size limit of the websit
Intermittent reconnection and plasmoids in UV bursts in the low solar atmosphere
Magnetic reconnection is thought to drive a wide variety of dynamic phenomena
in the solar atmosphere. Yet the detailed physical mechanisms driving
reconnection are difficult to discern in the remote sensing observations that
are used to study the solar atmosphere. In this paper we exploit the
high-resolution instruments Interface Region Imaging Spectrograph (IRIS) and
the new CHROMIS Fabry-Perot instrument at the Swedish 1-m Solar Telescope (SST)
to identify the intermittency of magnetic reconnection and its association with
the formation of plasmoids in so-called UV bursts in the low solar atmosphere.
The Si IV 1403A UV burst spectra from the transition region show evidence of
highly broadened line profiles with often non-Gaussian and triangular shapes,
in addition to signatures of bidirectional flows. Such profiles had previously
been linked, in idealized numerical simulations, to magnetic reconnection
driven by the plasmoid instability. Simultaneous CHROMIS images in the
chromospheric Ca II K 3934A line now provide compelling evidence for the
presence of plasmoids, by revealing highly dynamic and rapidly moving
brightenings that are smaller than 0.2 arcsec and that evolve on timescales of
order seconds. Our interpretation of the observations is supported by detailed
comparisons with synthetic observables from advanced numerical simulations of
magnetic reconnection and associated plasmoids in the chromosphere. Our results
highlight how subarcsecond imaging spectroscopy sensitive to a wide range of
temperatures combined with advanced numerical simulations that are realistic
enough to compare with observations can directly reveal the small-scale
physical processes that drive the wide range of phenomena in the solar
atmosphere.Comment: Accepted for publication in Astrophysical Journal Letters. Movies are
available at http://folk.uio.no/rouppe/plasmoids_chromis
Earlier versus later start of antiretroviral therapy in HIV-infected adults with tuberculosis.
Tuberculosis remains an important cause of death among patients infected with the human immunodeficiency virus (HIV). Robust data are lacking with regard to the timing for the initiation of antiretroviral therapy (ART) in relation to the start of antituberculosis therapy
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