41 research outputs found
Ionospheric response during Tropical Cyclones-a brief review on Amphan and Nisarga
Here, we explore the different characteristics of a possible coupling between
tropospheric and ionospheric activities during the impact of tropical cyclones
(TC) like Amphan and Nisarga in the Indian subcontinent. We have analyzed the
effect of TCs Amphan and Nisarga on the low latitude ionosphere using the
measurements from several IGS stations around India and a GPS+ NavIC station in
Indore, India. For the first time, this study assesses the impact of tropical
cyclones on the equatorial ionosphere using both GPS and NavIC. After the
landfall of TC Amphan, the VTEC analysis shows a significant drop from nominal
values in both NavIC as well in GPS by TECU and TECU, respectively.
In contrast to TC Amphan, Nisarga showed a rise in VTEC which ranged from
TECU in GPS to - TECU in NavIC satellites except for PRN6. The paper
examines Outgoing Longwave Radiation as a proxy to the convective activity
which may be responsible for the ionospheric variation through the generation
of gravity waves. In addition, the horizontal neutral wind observations at the
location of TC landfall confirm the presence of ionospheric disturbances. VTEC
perturbation analysis using a band-pass filter reveals a variation in
differential TEC values between and based on the IGS station
measurements. This indicates that the gravity wave is one of the responsible
mechanisms for the lower-upper atmospheric coupling during both cyclones
Performance of NavIC for studying the ionosphere at an EIA region in India
This paper emphasizes on NavIC's performance in ionospheric studies over the
Indian subcontinent region. The study is performed using data of one year
(2017-18) at IIT Indore, a location near the northern crest of Equatorial
Ionization Anomaly (EIA). It has been observed that even without the individual
error corrections, the results are within of NavIC VTEC estimates
observed over the 1\ensuremath{^{\circ}} x 1\ensuremath{^{\circ}} grid of IPP
surrounding the GPS VTEC estimates for most of the time. Additionally,
ionospheric response during two distinct geomagnetic storms (September 08 and
28, 2017) at the same location and other IGS stations covering the Indian
subcontinent using both GPS and NavIC has also been presented. This analysis
revealed similar variations in TEC during the geomagnetic storms of September
2017, indicating the suitability of NavIC to study space weather events along
with the ionospheric studies over the Indian subcontinent.Comment: 38 Pages, 16 Figures, Accepted for publication in Advances in Space
Researc
Texture Synthesis Guided Deep Hashing for Texture Image Retrieval
With the large-scale explosion of images and videos over the internet,
efficient hashing methods have been developed to facilitate memory and time
efficient retrieval of similar images. However, none of the existing works uses
hashing to address texture image retrieval mostly because of the lack of
sufficiently large texture image databases. Our work addresses this problem by
developing a novel deep learning architecture that generates binary hash codes
for input texture images. For this, we first pre-train a Texture Synthesis
Network (TSN) which takes a texture patch as input and outputs an enlarged view
of the texture by injecting newer texture content. Thus it signifies that the
TSN encodes the learnt texture specific information in its intermediate layers.
In the next stage, a second network gathers the multi-scale feature
representations from the TSN's intermediate layers using channel-wise
attention, combines them in a progressive manner to a dense continuous
representation which is finally converted into a binary hash code with the help
of individual and pairwise label information. The new enlarged texture patches
also help in data augmentation to alleviate the problem of insufficient texture
data and are used to train the second stage of the network. Experiments on
three public texture image retrieval datasets indicate the superiority of our
texture synthesis guided hashing approach over current state-of-the-art
methods.Comment: IEEE Winter Conference on Applications of Computer Vision (WACV),
2019 Video Presentation: https://www.youtube.com/watch?v=tXaXTGhzaJ
Acute onset movement disorders in diabetes mellitus: A clinical series of 59 patients
Background and purpose: No previous study has assessed the frequency and clinical– radiological characteristics of patients with diabetes mellitus (DM) and acute onset non-choreic and nonballistic movements. We conducted a prospective study to investigate the spectrum of acute onset movement disorders in DM.Methods: We recruited all the patients with acute onset movement disorders and hyper-glycemia who attended the wards of three hospitals in West Bengal, India from August 2014 to July 2021.Results: Among the 59 patients (mean age = 55.4± 14.3 years, 52.5% men) who were included, 41 (69.5%) had choreic or ballistic movements, and 18 (30.5%) had nonchoreic and nonballistic movements. Ballism was the most common movement disorder (n= 18, 30.5%), followed by pure chorea (n= 15, 25.4%), choreoathetosis (n= 8, 13.6%), tremor (n= 5, 8.5%), hemifacial spasm (n= 3, 5.1%), parkinsonism (n= 3, 5.1%), myoclonus (n= 3, 5.1%), dystonia (n= 2, 3.4%), and restless leg syndrome (n= 2, 3.4%). The mean duration of DM was 9.8 ± 11.4 years (89.8% of the patients had type 2 DM). Nonketotic hypergly-cemia was frequently (76.3%) detected. The majority (55.9%) had no magnetic resonance imaging (MRI) changes; the remaining showed striatal hyperintensity. Eight patients with MRI changes exhibited discordance with sidedness of movements. Most of the patients (76.3%) recovered completely.Conclusions: This is the largest clinical series depicting the clinical–radiological spectrum of acute onset movement disorders in DM. Of note was that almost one third of patients had nonchoreic and nonballistic movements. Our findings highlight the importance of a capillary blood glucose measurement in patients with acute or subacute onset movement disorders, irrespective of their past glycemic status
Amino Acid Restriction Triggers Angiogenesis via GCN2/ATF4 Regulation of VEGF and H2S Production
Angiogenesis, the formation of new blood vessels by endothelial cells (ECs), is an adaptive response to oxygen/nutrient deprivation orchestrated by vascular endothelial growth factor (VEGF) upon ischemia or exercise. Hypoxia is the best-understood trigger of VEGF expression via the transcription factor HIF1 alpha. Nutrient deprivation is inseparable from hypoxia during ischemia, yet its role in angiogenesis is poorly characterized. Here, we identified sulfur amino acid restriction as a proangiogenic trigger, promoting increased VEGF expression, migration and sprouting in ECs in vitro, and increased capillary density in mouse skeletal muscle in vivo via the GCN2/ATF4 amino acid starvation response pathway independent of hypoxia or HIF1 alpha. We also identified a requirement for cystathionine-gamma-lyase in VEGF-dependent angiogenesis via increased hydrogen sulfide (H2S) production. H2S mediated its proangiogenic effects in part by inhibiting mitochondrial electron transport and oxidative phosphorylation, resulting in increased glucose uptake and glycolytic ATP production.11Ysciescopu
Dynamics of Sticky Information and Sticky Price Models in a New Keynesian DSGE Framework
Recent literature on monetary policy analysis extensively uses the sticky price model of price adjustment in a New Keynesian Macroeconomic framework. This price setting model, however, has been criticized for producing implausible results regarding inflation and output dynamics. This paper examines and compares dynamic responses of the sticky price and sticky information
models to a cost-push shock in a New Keynesian DSGE framework. It finds that the sticky information model produces more reasonable dynamics through lagged, gradual and hump-shaped responses to a shock as observed in data. However, these responses depend on the persistence of the shock