90 research outputs found
Subnormal Vision in Uneventful Cataract Surgery after 6 Weeks – Hospital Based Study
Background: With accurate estimation of power of
intraocular lens (IOL), uncomplicated cataract surgery
and uneventful post operative period, the implant is
capable of providing a visual acuity of 6/6 and a normal
field of vision. However, post operative results are not
always according to the expectations. This study is an
attempt to find out causes of subnormal vision post
uneventful cataract surgery with posterior chamber
intraocular lens by various surgical techniques in
Krishna Institute of Medical Sciences, Karad,
Maharashtra, India. Aims and Objectives: To study the
incidence of subnormal vision in patients who have
undergone uneventful cataract surgery with posterior
chamber IOL implant and relation between the type of
surgery and IOL used and its effect on the subnormal
vision post operatively, in Krishna Hospital. Material
and Methods: 185 patients among 1230 who underwent
uneventful cataract surgery were diagnosed to
have sub-normal vision in our study, over the period of
18 months. All pseudophakic patients, who have
undergone uneventful cataract surgery, with normal
pre-operative assessment were included in the study.
Diabetic and hypertensive patients without any
maculopathy were also included. Patients with intra
operative complications, traumatic cataract, complicated
cataract and pre existing pathology were
excluded. Result: Prevalence of sub-normal vision in
our study was approximately 14.18%. Among all the
causes of sub-normal vision, incidence of posterior
capsular opacification (PCO) was maximum,
(80.87%). Incidence of PCO was least in foldable IOLs
as compared to square edge and non square edge
Proposed Route to Cyclopenta[c]thiophenes via Activated Methylene
The synthesis of cyclopenta[c]thiophenes has been sparsely reported in the literature owing to several difficulties involved in their synthesis. The present work involves the proposed synthesis of cyclopenta[c]thiophenes and their precursors using activated methylene. Cyclopenta[c]thiophene compounds show promise in the field of polymer and catalysis chemistry. These substituted polythiophenes are potential organic semiconductors and anti-tumor agents. The research presented shows the successful and novel conversion of 3,4-bis(chloromethyl)-2,5-dimethylthiophene and 3,4-bis(bromomethyl)-2,5-dimethylthiophene to a fused 5,5\u27-fused membered ring which is the precursor to cyclopenta[c]thiophene the sulfone ester, 5-carbomethoxy-5- phenylsulfonyl-1,3-dimethyl-5,6-dihydro-4H-cyclopenta[c]thiophene, in just two steps as compared to four steps previously reported in the literature. This valuable precursor intermediate currently made and proven by characterization is one synthetic step away from a substituted cyclopenta[c]thiophene. A paper has been submitted to Letters in Organic Chemistry to report our work
Guidelines for key organizational factors for saas organizations
© 2019 Association for Computing Machinery. Software as a Service is a new model of software deployment where a provider licenses an application to customers for use as a service on demand. Due to benefits offered by it, organizations are transferring towards the SaaS delivery model. As compared to traditional organizations, SaaS organizations must consider key factors to stand out in a competitive market. This paper provides a better understanding of key factors for SaaS organization and provides guidelines for these key factors for SaaS organization. Ultimately, these guidelines will be valuable for SaaS vendors to improve SaaS application performance
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An ASKAP Search for a Radio Counterpart to the First High-significance Neutron Star-Black Hole Merger LIGO/Virgo S190814bv
We present results from a search for a radio transient associated with the LIGO/Virgo source S190814bv, a likely neutron star-black hole (NSBH) merger, with the Australian Square Kilometre Array Pathfinder. We imaged a 30 deg2 field at ΔT = 2, 9, and 33 days post-merger at a frequency of 944 MHz, comparing them to reference images from the Rapid ASKAP Continuum Survey observed 110 days prior to the event. Each epoch of our observations covers 89% of the LIGO/Virgo localization region. We conducted an untargeted search for radio transients in this field, resulting in 21 candidates. For one of these, AT2019osy, we performed multiwavelength follow-up and ultimately ruled out the association with S190814bv. All other candidates are likely unrelated variables, but we cannot conclusively rule them out. We discuss our results in the context of model predictions for radio emission from NSBH mergers and place constrains on the circum-merger density and inclination angle of the merger. This survey is simultaneously the first large-scale radio follow-up of an NSBH merger, and the most sensitive widefield radio transients search to-date
Multi-wavelength observations of the obscuring wind in the radio-quiet quasar MR 2251-178
Obscuring winds driven away from active supermassive black holes are rarely
seen due to their transient nature. They have been observed with
multi-wavelength observations in a few Seyfert 1 galaxies and one broad
absorption line radio-quiet quasar so far. An X-ray obscuration event in MR
2251-178 was caught in late 2020, which triggered multi-wavelength (NIR to
X-ray) observations targeting this radio-quiet quasar. In the X-ray band, the
obscurer leads to a flux drop in the soft X-ray band from late 2020 to early
2021. X-ray obscuration events might have a quasi-period of two decades
considering earlier events in 1980 and 1996. In the UV band, a forest of weak
blueshifted absorption features emerged in the blue wing of Ly
in late 2020. Our XMM-Newton, NuSTAR, and HST/COS observations
are obtained simultaneously, hence, the transient X-ray obscuration event is
expected to account for the UV outflow, although they are not necessarily
caused by the same part of the wind. Both blueshifted and redshifted absorption
features were found for He {\sc i} , but no previous NIR spectra
are available for comparison. The X-ray observational features of MR 2251-178
shared similarities with some other type 1 AGNs with obscuring wind. However,
observational features in the UV to NIR bands are distinctly different from
those seen in other AGN with obscuring winds. A general understanding of the
observational variety and the nature of obscuring wind is still lacking.Comment: ApJ accepte
Progenitor, Precursor and Evolution of the Dusty Remnant of the Stellar Merger M31-LRN-2015
M31-2015-LRN is a likely stellar merger discovered in the Andromeda Galaxy in 2015. We present new optical to mid-infrared photometry and optical spectroscopy for this event. The transient brightened by ∼3 mag as compared to its progenitor. The complex precursor emission, which started ∼2 years before the nova event, may be explained by the binary undergoing Roche-lobe overflow. The dynamical mass loss from the outer Lagrange point L2 creates an optically thick outflow to power the observed brightening of the system. We find two possible periods of 16±0.3 and 28.1±1.4 days at different phases of the precursor lightcurve, possibly related to the geometry of the mass-loss from the binary. Although the progenitor spectral energy distribution shows no evidence of pre-existing warm dust in system, the remnant forms an optically thick dust shell 2−4 months after the outburst peak. The optical depth of the shell increases after 1.5 years, suggesting the existence of shocks that enhance the dust formation process. We propose that the merger remnant is likely an inflated giant obscured by a cooling shell of gas with mass ∼0.2 M⊙ ejected at the onset of the common envelope phase
SPIRITS Catalog of Infrared Variables: Identification of Extremely Luminous Long Period Variables
We present a catalog of 417 luminous infrared variable stars with periods
exceeding 250 days. These were identified in 20 nearby galaxies by the ongoing
SPIRITS survey with the Spitzer Space Telescope. Of these, 359 variables have
(phase-weighted mean magnitudes) fainter than and periods and
luminosities consistent with previously reported variables in the Large
Magellanic Cloud. However, 58 variables are more luminous than , including 11 that are brighter than with the brightest
having . Most of these bright variable sources have
quasi-periods longer than 1000 days, including four over 2000 days. We suggest
that the fundamental period-luminosity relationship, previously measured for
the Large Magellanic Cloud, extends to much higher luminosities and longer
periods in this large galaxy sample. We posit that these variables include
massive AGB stars (possibly super-AGB stars), red supergiants experiencing
exceptionally high mass-loss rates, and interacting binaries. We also present
3.6, 4.5, 5.8 and 8.0 m photometric catalogs for all sources in these 20
galaxies.Comment: 18 pages, 25 figure
Multiwavelength observations of the obscuring wind in the radio-quiet quasar MR 2251-178
High Energy Astrophysic
SN 2022joj: A Peculiar Type Ia Supernova Possibly Driven by an Asymmetric Helium-shell Double Detonation
We present observations of SN 2022joj, a peculiar Type Ia supernova (SN Ia)
discovered by the Zwicky Transient Facility (ZTF). SN 2022joj exhibits an
unusually red color at early times and a rapid
blueward evolution afterwards. Around maximum brightness, SN 2022joj shows a
high luminosity ( mag), a blue
broadband color ( mag), and shallow Si
II absorption lines, consistent with those of overluminous, SN 1991T-like
events. The maximum-light spectrum also shows prominent absorption around 4200
\r{A}, which resembles the Ti II features in subluminous, SN 1991bg-like
events. Despite the blue optical-band colors, SN 2022joj exhibits extremely red
ultraviolet optical colors at maximum luminosity ( mag and
mag), suggesting a suppression of flux between
2500--4000 \r{A}. Strong C II lines are also detected at peak. We show
that these unusual spectroscopic properties are broadly consistent with the
helium-shell double detonation of a sub-Chandrasekhar mass
() carbon/oxygen (C/O) white dwarf (WD) from a
relatively massive helium shell (--), if
observed along a line of sight roughly opposite to where the shell initially
detonates. None of the existing models could quantitatively explain all the
peculiarities observed in SN 2022joj. The low flux ratio of [Ni II]
7378 to [Fe II] 7155 emission in the late-time nebular
spectra indicates a low yield of stable Ni isotopes, favoring a
sub-Chandrasekhar mass progenitor. The significant blueshift measured in the
[Fe II] 7155 line is also consistent with an asymmetric chemical
distribution in the ejecta, as is predicted in double-detonation models.Comment: 24 pages, 11 figures, 6 tables. Submitted to Ap
Discovery and confirmation of the shortest gamma ray burst from a collapsar [Author Correction to: Nature Astronomy https://doi.org/10.1038/s41550-021-01428-7,]
Gamma-ray bursts (GRBs) are among the brightest and most energetic events in the universe. The duration and hardness distribution of GRBs has two clusters, now understood to reflect (at least) two different progenitors. Short-hard GRBs (SGRBs; T90 2 s) have been attributed to the collapse of peculiar massive stars (collapsars). The discovery of SN 1998bw/GRB 980425 marked the first association of a LGRB with a collapsar and AT 2017gfo/GRB 170817A/GW170817 marked the first association of a SGRB with a binary neutron star merger, producing also gravitational wave (GW). Here, we present the discovery of ZTF20abwysqy (AT2020scz), a fast-fading optical transient in the Fermi Satellite and the InterPlanetary Network (IPN) localization regions of GRB 200826A; X-ray and radio emission further confirm that this is the afterglow. Follow-up imaging (at rest-frame 16.5 days) reveals excess emission above the afterglow that cannot be explained as an underlying kilonova (KN), but is consistent with being the supernova (SN). Despite the GRB duration being short (rest-frame T90 of 0.65 s), our panchromatic follow-up data confirms a collapsar origin. GRB 200826A is the shortest LGRB found with an associated collapsar; it appears to sit on the brink between a successful and a failed collapsar. Our discovery is consistent with the hypothesis that most collapsars fail to produce ultra-relativistic jets
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