Low latitude ionospheric response to March 2015 geomagnetic storm using multi-instrument TEC observations over India

The regional ionospheric models are successful in capturing the variability of ionosphere with the inclusion of local ground-based GPS observations and location dependent ionospheric dynamics. In this context, there is a need to develop regional ionospheric maps that aids in improving the consistency of global models. In this paper, an attempt is made to understand the potentiality of multi-instrument observations over Indian region. Four different Total Electron Content (TEC) data sources namely from network of GPS receivers, Ionosonde stations, space based COSMIC radio occultation profiles and SWARM mission data is utilized. The multi-source data is chosen for the geo-magnetic storm conditions prevailed during March 2015. Data from multiple-sources is observed over the period from 15th March 2015 to 20th March 2015. Validation of ground and space-based TEC data with International GNSS service (IGS) station data is significantly observed

QSAR on some anaesthetics and narcotics using negentropy

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Signature of Y-forking in ionogram traces observed at low-mid latitude Indian station, New Delhi, during the earthquake events of 2020: ionosonde observations

We have examined ionospheric response to eleven earthquake events measuring less than four on the Richter scale during the year 2020 that occurred in the vicinity of New Delhi (28.6°N, 77.2°E, 42.4°N dip). We have used ionogram traces, manually scaled critical ionospheric layer parameters using SAO explorer obtained from Digisonde along with the O(1D) airglow observations from a multi-wavelength all-sky airglow imager installed at Hanle, Ladakh, India (32.7°N, 78.9°E, 24.1°N dip). Perceptible ionospheric perturbations 2–9 days prior to these earthquake events resulting in more than 250% variation in electron density are observed. We found distortion of ionogram trace in the form of Y forking majorly at New Delhi on the precursor day and after the earthquake event. Traces of Y forked ionograms were also observed at Ahmedabad (23°N, 72°E, 15°N dip) and Trivandrum (8.5°N, 76.9°E, 0.5°N dip). These Y-forked ionograms are one of the first observations during any earthquake events and are looked at as a signature of Travelling Ionospheric Disturbances (TIDs)

Probing the Interaction of the Diarylquinoline TMC207 with Its Target Mycobacterial ATP Synthase

Infections with Mycobacterium tuberculosis are substantially increasing on a worldwide scale and new antibiotics are urgently needed to combat concomitantly emerging drug-resistant mycobacterial strains. The diarylquinoline TMC207 is a highly promising drug candidate for treatment of tuberculosis. This compound kills M. tuberculosis by binding to a new target, mycobacterial ATP synthase. In this study we used biochemical assays and binding studies to characterize the interaction between TMC207 and ATP synthase. We show that TMC207 acts independent of the proton motive force and does not compete with protons for a common binding site. The drug is active on mycobacterial ATP synthesis at neutral and acidic pH with no significant change in affinity between pH 5.25 and pH 7.5, indicating that the protonated form of TMC207 is the active drug entity. The interaction of TMC207 with ATP synthase can be explained by a one-site binding mechanism, the drug molecule thus binds to a defined binding site on ATP synthase. TMC207 affinity for its target decreases with increasing ionic strength, suggesting that electrostatic forces play a significant role in drug binding. Our results are consistent with previous docking studies and provide experimental support for a predicted function of TMC207 in mimicking key residues in the proton transfer chain and blocking rotary movement of subunit c during catalysis. Furthermore, the high affinity of TMC207 at low proton motive force and low pH values may in part explain the exceptional ability of this compound to efficiently kill mycobacteria in different microenvironments

New endoperoxides highly active in vivo and in vitro against artemisinin-resistant Plasmodium falciparum

Background: The emergence and spread of Plasmodium falciparum resistance to artemisinin-based combination therapy in Southeast Asia prompted the need to develop new endoperoxide-type drugs. Methods: A chemically diverse library of endoperoxides was designed and synthesized. The compounds were screened for in vitro and in vivo anti-malarial activity using, respectively, the SYBR Green I assay and a mouse model. Ring survival and mature stage survival assays were performed against artemisinin-resistant and artemisinin-sensitive P. falciparum strains. Cytotoxicity was evaluated against mammalian cell lines V79 and HepG2, using the MTT assay. Results: The synthesis and anti-malarial activity of 21 new endoperoxide-derived compounds is reported, where the peroxide pharmacophore is part of a trioxolane (ozonide) or a tetraoxane moiety, flanked by adamantane and a substituted cyclohexyl ring. Eight compounds exhibited sub-micromolar anti-malarial activity (IC50 0.3–71.1 nM), no cross-resistance with artemisinin or quinolone derivatives and negligible cytotoxicity towards mammalian cells. From these, six produced ring stage survival < 1% against the resistant strain IPC5202 and three of them totally suppressed Plasmodium berghei parasitaemia in mice after oral administration. Conclusion: The investigated, trioxolane–tetrazole conjugates LC131 and LC136 emerged as potential anti-malarial candidates; they show negligible toxicity towards mammalian cells, ability to kill intra-erythrocytic asexual stages of artemisinin-resistant P. falciparum and capacity to totally suppress P. berghei parasitaemia in mice.info:eu-repo/semantics/publishedVersio

Preearthquake anomalous ionospheric signatures observed at low-mid latitude Indian station, Delhi, during the year 2015 to early 2016: Preliminary results

We have analyzed five major earthquake events measuring greater than 6 on Richter scale (M > 6) that occurred during the year 2015 to early 2016, affecting Indian region ionosphere, using F-2 layer critical parameters (f(o)F(2), h(m)F(2)) obtained using Digisonde from a low-mid latitude Indian station, Delhi (28.6 degrees N, 77.2 degrees E, 19.2 degrees N geomagnetic latitude, 42.4 degrees N dip). Normal day-to-day variability occurring in ionosphere is segregated by calculating F-2 layer critical frequency and peak height variations (Delta f(o)F(2), h(m)F(2)) from the normal quiet time behavior apart from computing interquartile range. We find that the ionospheric F-2 region across Delhi by and large shows some significant perturbations 3-4 days prior to these earthquake events, resulting in a large peak electron density variation of similar to 200%. These observed perturbations indicate towards a possibility of seismo-ionospheric coupling as the solar and geomagnetic indices were normally quiet and stable during the period of these events. It was also observed that the precursory effect of earthquake was predominantly seen even outside the earthquake preparation zone, as given by Dobrovolsky et al. (1979). The thermosphere neutral composition (O/N-2) as observed by Global Ultraviolet Imager, across Delhi, during these earthquake events does not show any marked variation. Further, the effect of earthquake events on ionospheric peak electron density is compared to the lower atmosphere meteorological phenomenon of 2015 sudden stratospheric warming event

Longitudinal Characteristics of Martian Electron Density Profiles: MGS Observations

An analysis of longitudinal characteristics of 5,600 electron density profiles returned from the Mars Global Surveyor's Radio Science experiment is carried out by dividing the entire data set into 33 subsets, keeping solar zenith angle nearly constant. We find that the peak altitude of the photochemical F1 layer (hmF1) exhibits a large degree of longitudinal variability. This variability is not seen in Earth's ionosphere. Since F1 layer is isobaric, this variability in hmF1 represents a large degree of spatial changes in the underlying neutral atmosphere. Though this variability is quite chaotic in most of the subsets, a few subsets provide some evidence for the presence of a well-defined wave. We therefore perform a spectral fit of wave 1-3, as earlier carried out by Bougher et al. (2004, https://doi.org/10.1029/2003JE002154; 2001, https://doi.org/10.1029/2001GL012884), to all 33 subsets. Results indicate that this wave is seen only in 10 of the subsets and is most dominant between 0 to 200 degrees E longitudes. Similar wave is seen in the longitude plots of the peak electron density of F1 layer but with a phase reversal. Further, these 10 subsets are confined mostly between 02 to 04 local solar time, thereby indicating a local time dependence of the wave. We examined the characteristics of electron density profiles located at the crests and troughs and found abnormal upliftment in F1 layer during consecutive occultations (similar to 2 hr). Rapid spatial changes are observed during intervals as short as 2 hr. The ionosphere is lifted up and the peak density decreases when wave 1-3 is present

Morphology of Martian Low-Altitude Ionospheric Layer: MGS Observations

An analysis of the entire data set of 5,600 electron density profiles returned by Mars Global Surveyor's Radio Science Experiment is carried out to study the physical characteristics of Martian low-altitude plasma layer (M layer). Our analysis suggests that this layer is predominantly observed during low and moderate solar activity periods, in northern autumn. The critical ionospheric parameters (electron density and height) of this M layer are found not to show a definitive correlation with solar zenith angle. In contrast to earlier reports where meteoroid ablation was proposed to cause total electron content (TEC) enhancements, we report that the maximum contribution from this layer (TECM) is only about 5.5%, while the contribution is 3.7% during predicted meteor shower, suggesting that M layer occurrence does not depend upon meteor shower nor on dust storm. It is observed that the M layer occurrence increases as the Martian E region becomes prominent and well defined, suggesting that the source which causes M layer possibly leads to more pronounced E layers. Southern hemisphere profiles were found to behave differently from northern hemisphere profiles, possibly due to crustal magnetic fields. Large surges observed in Martian F1 layer peak height during consecutive occultations (similar to 2hr apart) are found not to show any correlation with the occurrence of M layer and are not influenced by dust storms

Ionospheric F-2 region: Variability and sudden stratospheric warmings

The ionospheric F-2 region is known to show a large day-to-day and hour-to-hour variability. Some of this variability has recently being linked to sudden stratospheric warmings (SSWs). We therefore investigate the extent of ionospheric changes following SSWs of 2007, 2008, and 2009 using ionosonde data from six different stations in the Asian zone, thus covering a broad latitudinal range from 23.2 degrees N to 45.1 degrees N. We find that ionospheric F-2 region shows some significant perturbations soon after the start of the warming. However, characteristics of these perturbations vary from event to event and from station to station. We also examine the data on equatorial electrojet strength (EEJ) during these warmings and find that there are significant changes in the EEJ strength during the SSW events. A counter electrojet coincident with the start of warming was observed for the SSW event of 2008. We then compare this SSW-linked variability observed by us to the normal day-to-day and hour-to-hour variability seen in the ionospheric data. We find that even during times when there are no SSWs and solar and magnetic indices are quite stable and close to their minimum values, the ionospheric variability is comparable to the variability attributed to these warmings. Further, it seems to us that it is difficult to quantify with precision the changes in f(o)F(2), as well as in the ionospheric response times involved, following these events