3,736 research outputs found
Morphology and evolution of umbral dots and their substructures
Substructures - dark lanes and tails - of umbral dots (UDs) were predicted by
numerical simulations of magnetoconvection. We analyse a 6 h 23 min time series
of broadband images of a large umbra in the active region NOAA 10634, acquired
with the 1-m Swedish Solar Telescope, in the wavelength band around 602 nm. A
43 min part of this series was reconstructed with the MFBD method, reaching a
spatial resolution of 0.14". We measure brightness, size, lifetime, and
horizontal velocities of various umbral structures. Most (90 %) of UDs and
bright point-like features in faint LBs split and merge, and their median
lifetimes are 3.5 or 5.7 min, depending on whether the split or merge event is
considered as the end of their life. Both UDs and features in faint LBs that do
not split or merge are clearly smaller (0.15") than the average size (0.17") of
all features. Horizontal motions of umbral bright small-scale features are
directed either into the umbra or along faint LBs with mean horizontal
velocities of 0.34 km/s. Features faster than 0.4 km/s appear mostly at the
periphery of the umbra. The intensity of dark lanes, measured in four bright
central UDs (CUDs), is by a factor 0.8 lower than the peak intensity of CUDs.
The width of dark lanes is probably less than the resolution limit 0.14". The
characteristic time of substructure changes of UDs is ~4 min. We observe narrow
(0.14") bright and dark filaments connected with PUDs. Usually one dark and two
bright filaments form a 0.4" wide tail attached to one PUD, resembling a short
dark-cored penumbral filament. Our results indicate the similarity between PUDs
and PGs located at the tips of bright penumbral filaments. The features seen in
numerical MHD simulations are consistent with our observations of dark lanes in
CUDs and tails attached to PUDs.Comment: 8 pages, 8 figures, Astronomy & Astrophysics, in pres
Waves as the source of apparent twisting motions in sunspot penumbrae
The motion of dark striations across bright filaments in a sunspot penumbra
has become an important new diagnostic of convective gas flows in penumbral
filaments. The nature of these striations has, however, remained unclear. Here
we present an analysis of small scale motions in penumbral filaments in both
simulations and observations. The simulations, when viewed from above, show
fine structure with dark lanes running outwards from the dark core of the
penumbral filaments. The dark lanes either occur preferentially on one side or
alternate between both sides of the filament. We identify this fine structure
with transverse (kink) oscillations of the filament, corresponding to a
sideways swaying of the filament. These oscillations have periods in the range
of 5-7 min and propagate outward and downward along the filament. Similar
features are found in observed G-band intensity time series of penumbral
filaments in a sunspot located near disk center obtained by the Broadband
Filter Imager (BFI) on board {\it Hinode}. We also find that some filaments
show dark striations moving to both sides of the filaments. Based on the
agreement between simulations and observations we conclude that the motions of
these striations are caused by transverse oscillations of the underlying bright
filaments.Comment: Accepted for publication in Astrophysical Journal on 8th April 201
Automating the Surveillance of Mosquito Vectors from Trapped Specimens Using Computer Vision Techniques
Among all animals, mosquitoes are responsible for the most deaths worldwide.
Interestingly, not all types of mosquitoes spread diseases, but rather, a
select few alone are competent enough to do so. In the case of any disease
outbreak, an important first step is surveillance of vectors (i.e., those
mosquitoes capable of spreading diseases). To do this today, public health
workers lay several mosquito traps in the area of interest. Hundreds of
mosquitoes will get trapped. Naturally, among these hundreds, taxonomists have
to identify only the vectors to gauge their density. This process today is
manual, requires complex expertise/ training, and is based on visual inspection
of each trapped specimen under a microscope. It is long, stressful and
self-limiting. This paper presents an innovative solution to this problem. Our
technique assumes the presence of an embedded camera (similar to those in
smart-phones) that can take pictures of trapped mosquitoes. Our techniques
proposed here will then process these images to automatically classify the
genus and species type. Our CNN model based on Inception-ResNet V2 and Transfer
Learning yielded an overall accuracy of 80% in classifying mosquitoes when
trained on 25,867 images of 250 trapped mosquito vector specimens captured via
many smart-phone cameras. In particular, the accuracy of our model in
classifying Aedes aegypti and Anopheles stephensi mosquitoes (both of which are
deadly vectors) is amongst the highest. We present important lessons learned
and practical impact of our techniques towards the end of the paper
Spreading Awareness and Job Opportunities Through Odl
Distance Education has done miracles in the field of education, it caters to those students who study and work on their own at home or at the office and communicate with faculty and other students via e-mail, electronic forums, video conferencing, chat rooms, boards, instant messaging and varieties of other forms of computer-based communication. Distance learning makes it much easier for some students to complete a degree or get additional job-training while balancing work and family commitments. This article elaborates upon the significance of Distance Education discussing various job oriented courses offered by Open universities to aspirants seeking degrees for a better resume and for career enhancements
Enhanced Joule Heating in Umbral Dots
We present a study of magnetic profiles of umbral dots (UDs) and its
consequences on the Joule heating mechanisms. Hamedivafa (2003) studied Joule
heating using vertical component of magnetic field. In this paper UDs magnetic
profile has been investigated including the new azimuthal component of magnetic
field which might explain the relatively larger enhancement of Joule heating
causing more brightness near circumference of UD.Comment: 8 pages, 1 figure, accepted in Solar Physic
Localised plumes in three-dimensional compressible magnetoconvection
Within the umbrae of sunspots, convection is generally inhibited by the
presence of strong vertical magnetic fields. However, convection is not
completely suppressed in these regions: bright features, known as umbral dots,
are probably associated with weak, isolated convective plumes. Motivated by
observations of umbral dots, we carry out numerical simulations of
three-dimensional, compressible magnetoconvection. By following solution
branches into the subcritical parameter regime (a region of parameter space in
which the static solution is linearly stable to convective perturbations), we
find that it is possible to generate a solution which is characterised by a
single, isolated convective plume. This solution is analogous to the steady
magnetohydrodynamic convectons that have previously been found in
two-dimensional calculations. These results can be related, in a qualitative
sense, to observations of umbral dots.Comment: submitted to MNRA
Properties of simulated sunspot umbral dots
Realistic 3D radiative MHD simulations reveal the magneto-convective
processes underlying the formation of the photospheric fine structure of
sunspots, including penumbral filaments and umbral dots. Here we provide
results from a statistical analysis of simulated umbral dots and compare them
with reports from high-resolution observations. A multi-level segmentation and
tracking algorithm has been used to isolate the bright structures in synthetic
bolometric and continuum brightness images. Areas, brightness, and lifetimes of
the resulting set of umbral dots are found to be correlated: larger umbral dots
tend to be brighter and live longer. The magnetic field strength and velocity
structure of umbral dots on surfaces of constant optical depth in the continuum
at 630 nm indicate that the strong field reduction and high velocities in the
upper parts of the upflow plumes underlying umbral dots are largely hidden from
spectro-polarimetric observations. The properties of the simulated umbral dots
are generally consistent with the results of recent high-resolution
observations. However, the observed population of small, short-lived umbral
dots is not reproduced by the simulations, possibly owing to insufficient
spatial resolution.Comment: Accepted for publication in A&
Histopathological analysis of lymph nodes in patient with clinical lymphadenopathy - 266 cases
Background: Lymphadenopathy is one of the most common clinical presentations among patients of all ages. This study has undertaken to study the histological patterns in various non-neoplastic condition, lymphoma and metastatic carcinoma in patient with lymphadenopathy and to do the clinico-pathological correlation with respect to age, sex and site of lymph node involved.Methods: Total 266 cases of lymph node biopsy were studied, for a period of 28 months at Pathology department, Government Medical College, Surat, Gujarat, India. Tissues were adequately fixed in formalin and blocks prepared, sections cut and slides were prepared, stained by routine H&E stain. A complete and thorough histopathological examination of all the slides was undertaken.Results: A total of 266 cases were studied, age range was 1-75 years, 136 were males and 130 were females. Out of 266 cases, 96 cases (36%) were non-specific lymph node hyperplasia, 81 cases (31%) were of metastatic deposits in lymph node, 70 cases (26%) were of specific non neoplastic conditions and 19 cases (7%) were of lymphoma.Conclusions: Lymph node biopsy plays an important role in establishing the cause of lymphadenopathy. Among the biopsied nodes, non-specific lymph node hyperplasia was the most common followed by metastatic deposits, specific non neoplastic conditions especially tuberculous lymphadenitis and lymphoma. Non neoplastic conditions were more common in early age while neoplastic conditions were more common in late age. TB lymphadenitis was more common in HIV positive patients as compared to general population.
A refined shear deformation theory for bending analysis of isotropic and orthotropic plates under various loading conditions
In this paper, a refined trigonometric shear deformation theory is applied for the bending analysis of isotropic and orthotropic plates under the various loading conditions. The two unknown variables are involved in the present theory. The present theory satisfies the shear stress free condition at top and bottom surface of the plates without using shear correction factors. The governing equations and boundary conditions are obtained by using the principle of virtual work. A closed form solution is obtained using Navier Solution Scheme. A simply supported isotropic and orthotropic plate subjected to sinusoidally distributed, uniformly distributed and linearly varying loads are considered for the detailed numerical study. The results obtained using present theory are compared with previously published results.
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