317 research outputs found
Properties of Umbral Dots from Stray Light Corrected Hinode Filtergrams
High resolution blue continuum filtergrams from Hinode are employed to study
the umbral fine structure of a regular unipolar sunspot. The removal of
scattered light from the images increases the rms contrast by a factor of 1.45
on average. Improvement in image contrast renders identification of short
filamentary structures resembling penumbrae that are well separated from the
umbra-penumbra boundary and comprise bright filaments/grains flanking dark
filaments. Such fine structures were recently detected from ground based
telescopes and have now been observed with Hinode. A multi-level tracking
algorithm was used to identify umbral dots in both the uncorrected and
corrected images and to track them in time. The distribution of the values
describing the photometric and geometric properties of umbral dots are more
easily affected by the presence of stray light while it is less severe in the
case of kinematic properties. Statistically, umbral dots exhibit a peak
intensity, effective diameter, lifetime, horizontal speed and a trajectory
length of 0.29 I_QS, 272 km, 8.4 min, 0.45 km/s and 221 km respectively. The 2
hr 20 min time sequence depicts several locations where umbral dots tend to
appear and disappear repeatedly with various time intervals. The correction for
scattered light in the Hinode filtergrams facilitates photometry of umbral fine
structure which can be related to results obtained from larger telescopes and
numerical simulations.Comment: Accepted for publication in ApJ : 10 pages, 10 figures, 3 table
Water quality effects of harbour activities assessed with integrated ecotoxicological parameters in Kerala, India
Ecological tools were developed to study the water quality in Cochin harbour, a complex aquatic ecosystems, through the integration of microbiological monitoring (faecal coliforms and Pseudomonas species) and heavy metal contamination (lead, cadmium and mercury). One way ANOVA indicates statistically significant differences (P = 0.002) in bacterial population between sites and at the same comparatively higher population in site I, reveals the possible impacts of the harbour activities. Total coliforms (TC), faecal coliorms (FC) and facecal streptococci (FS) reported their mean high values of 789.33 CFU/ml, 535 CFU/ml and 231.67 CFU/ml respectively at site 1 which is designated for the anchoring of the ships. FC/FS ratio also suggests the pollution is more with human faecal origin. Reported higher concentrations of lead (44.81 ppm), cadmium (1.5 ppm) and mercury (1.21 ppm) depicts the industrial origin. The relationship between petroleum hydrocarbons (PHC) and Pseudomonas aeruginosa (PA) signify the reliability of PA as a biological marker for PHC contamination.Keywords: Harbour activities, pollution, faecal contamination index, Pseudomonas aeruginosa, petroleum hydrocarbons, heavy metals
Supersonic Downflows in a Sunspot Light Bridge
We report the discovery of supersonic downflows in a sunspot light bridge
using measurements taken with the spectropolarimeter on board the Hinode
satellite. The downflows occur in small patches close to regions where the
vector magnetic field changes orientation rapidly, and are associated with
anomalous circular polarization profiles. An inversion of the observed Stokes
spectra reveals velocities of up to 10 km/s, making them the strongest
photospheric flows ever measured in light bridges. Some (but not all) of the
downflowing patches are cospatial and cotemporal with brightness enhancements
in chromospheric Ca II H filtergrams. We suggest that these flows are due to
magnetic reconnection in the upper photosphere/lower chromosphere, although
other mechanisms cannot be ruled out.Comment: 4 pages, 5 figures, Published in ApJ Letter
Microbial diversity in individuals and their household contacts following typical antibiotic courses.
BackgroundAntibiotics are a mainstay of treatment for bacterial infections worldwide, yet the effects of typical antibiotic prescriptions on human indigenous microbiota have not been thoroughly evaluated. We examined the effects of the two most commonly prescribed antibiotics (amoxicillin and azithromycin) in the USA to discern whether short-term antibiotic courses may have prolonged effects on human microbiota.ResultsWe sampled the feces, saliva, and skin specimens from a cohort of unrelated, cohabitating individuals over 6 months. An individual in each household was given an antibiotic, and the other a placebo to discern antibiotic impacts on microbiota, as well as determine whether antibiotic use might reshape the microbiota of each household. We observed household-specific patterns of microbiota on each body surface, which persevered despite antibiotic perturbations. While the gut microbiota within an individual became more dissimilar over time, there was no evidence that the use of antibiotics accelerated this process when compared to household members. There was a significant change in microbiota diversity in the gut and mouth in response to antibiotics, but analogous patterns were not observed on the skin. Those who received 7 days of amoxicillin generally had greater reductions in diversity compared to those who received 3 days, in contrast to those who received azithromycin.ConclusionsAs few as 3 days of treatment with the most commonly prescribed antibiotics can result in sustained reductions in microbiota diversity, which could have implications for the maintenance of human health and resilience to disease
A Federated Consensus for Proof of Authority in IoT-Blockchain Applications
The growing adoption of Internet of Things (IoT) devices and the need for secure and scalable blockchain applications pose significant challenges in the realm of consensus protocols. This paper proposes a novel consensus mechanism called Federated Consensus for Proof of Authority (Fed-PoA), which combines the advantages of Proof of Authority (PoA) and federated learning to achieve secure and scalable IoT-Blockchain applications. The Fed-PoA ensures efficient data sharing, privacy preservation, and decentralized operation. Performance evaluation of this model in a simulated environment demonstrates superior convergence and memory usage compared to a representative work in this context
Influence of pH adjustment on physicochemical properties of microfiltration retentates of skim milk and rehydration properties of resulting powders
Effects of pH adjustment on physicochemical properties of microfiltration retentates of skim milk and rehydration of resulting micellar casein concentrate (MCC) powders were investigated. Aliquots of retentate (pH 6.9) were adjusted to pH 7.3, 7.6 or 7.6 followed by readjustment to pH 6.9 (6.9R) prior to powder preparation. The retentates with pH 6.9, 7.3, and 7.6 had casein micelle size of 179, 189 and 197 nm, respectively, while sample 6.9R had size of 183 nm, similar to retentate at pH 6.9. Higher retentate pH resulted in lower ionic calcium and higher conductivity, with sample 6.9R having higher values for both parameters than the pH 6.9 sample. The MCC powders displayed poorer wettability and enhanced dispersibility with increasing retentate pH. Interestingly, the 6.9R powder had the best wettability and dispersibility. This study demonstrated that pH-mediated modifications of the physicochemical properties of retentates improve the rehydration properties of resultant MCC powders
Increase in superficial dose in whole-breast irradiation with Halcyon straight-through linac compared with traditional C-arm linac with flattening filter: In vivo dosimetry and planning study
Supersonic Downflows at the Umbra-Penumbra Boundary of Sunspots
High resolution spectropolarimetric observations of 3 sunspots taken with
Hinode demonstrate the existence of supersonic downflows at or close to the
umbra-penumbra boundary which have not been reported before. These downflows
are confined to large patches, usually encompassing bright penumbral filaments,
and have lifetimes of more than 14 hr. The presence of strong downflows in the
center-side penumbra near the umbra rules out an association with the Evershed
flow. Chromospheric filtergrams acquired close to the time of the
spectropolarimetric measurements show large, strong, and long-lived
brightenings in the neighborhood of the downflows. The photospheric intensity
also exhibit persistent brightenings comparable to the quiet Sun.
Interestingly, the orientation of the penumbral filaments at the site of the
downflows is similar to that resulting from the reconnection process described
by Ryutova et al. The existence of such downflows in the inner penumbra
represents a challenge for numerical models of sunspots because they have to
explain them in terms of physical processes likely affecting the chromosphere.Comment: Accepted for publication in Ap
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