Waves - like signatures in the D-region ionosphere generated by solar flares

The present study reports presence of periodic Wave-Like Signatures (WLS) in the D-region ionosphere detected using NWC, Australia, VLF navigational transmitter signal (19.8 kHz) observed at Allahabad, an Indian low latitude station. The observed WLS are associated with series of solar flares which includes 12 C, 3 M and 2 X class flares occurred during the month of May 2013. Significant variations are observed on NWC-VLF amplitude and phase due to different classes of flares which occurred at different solar zenith angles. The wavelet analysis of VLF amplitude on control day reveals presence of WLS with periods 40-180 minutes during day/night and night/day transition times which are probably generated due to passage of dusk and dawn solar terminator. Flare day WLS are observed with period varying 90-200 minutes and are remarkably different in their period, occurrence duration/time and amplitude depending on the class and occurrence time of flare and are more prominent during morning and evening times when D-region is in developing stage. The WLS on flare day are probably generated by solar flare induced gravity waves which may cause periodic changes in temperature, electron density, and plasma conductivity in the ionosphere. The present observations seem to shed additional light on the current understanding of gravity wave induced D-region dynamics

Preparation of a New Oxotetracyano- (pyridine)chromate(IV) Anion

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Integrated effect of bio-organics with chemical fertilizer on growth, yield and quality of cabbage (Brassica oleracea var capitata)

This experiment focused on the effects of Pseudomonas fluorescens and humic acid in combination with three different levels of fertilizers on growth, yield and quality traits of Brassica oleracea L. Results indicated that treatments comprising 100% recommended fertilizers package coupled with seedling treated with Pseudomonas fluorescens and humic acid caused significantly higher plant height, dry matter in leaves (head), higher number of non-wrapper leaves and head yield (54.38 tonnes/ha) over 50% recommended dose of fertilizer with Pseudomonas fluorescens applied. Treatment 50% recommended dose of fertilizer applied with Pseudomonas fluorescens and humic acid was at par with 100% recommended dose of fertilizer alone. Total carbohydrate content in head (40.46%) was significantly higher with use of 100% recommended dose of fertilizer with Pseudomonas fluorescens and humic acid. Maximum protein content (18.54%) was noticed with application of 100% recommended dose of fertilizer with Pseudomonas fluorescens and humic acid that was 10.90% higher than recommended dose of fertilizer alone. Fibre content in head was improved remarkably with the use of Pseudomonas fluorescens and humic acid. Significantly higher content of ascorbic acid (34.51 mg/100 g) in head was also registered with application of 100% recommended dose of fertilizer with Pseudomonas fluorescens and humic acid

Comparative study of soil fertility status of cold desert Ladakh region before and after cloudburst

Present study was undertaken to determine loss of soil organic carbon, major and micronutrient status of cold desert Ladakh region as a result of unprecedented cloudburst in August 2010. Heavy rainfall (250 mm) within an hour leading to flash floods resulted in severe loss of standing crops spreading over 1400 ha of agriculture land besides destruction of human, animal lives, infrastructures. In most of the affected areas, top fertile soil completely washed away resulting in severe depletion of various major and micro nutrients essential for good soil health. Soil pH was recorded 8.66 and organic carbon severely depleted from 1.09% to only 0.24% making the soil very loose and poor in WHC. N, P and K (115.4, 1.0 and 103.4 kg/ha respectively) and micronutrient contents were also severely reduced as compared to original soil. These losses have severe long-term effects on crop productivity and economy of the region. Some ameliorative measures have also been mentioned for improving soil health and sustainable crop production

Coronal Mass Ejection-driven Shocks and the Associated Sudden Commencements-sudden Impulses

Interplanetary (IP) shocks are mainly responsible for the sudden compression of the magnetosphere, causing storm sudden commencement (SC) and sudden impulses (SIs) which are detected by ground-based magnetometers. On the basis of the list of 222 IP shocks compiled by Gopalswamy et al., we have investigated the dependence of SC/SIs amplitudes on the speed of the coronal mass ejections (CMEs) that drive the shocks near the Sun as well as in the interplanetary medium. We find that about 91% of the IP shocks were associated with SC/SIs. The average speed of the SC/SI-associated CMEs is 1015 km/s, which is almost a factor of 2 higher than the general CME speed. When the shocks were grouped according to their ability to produce type II radio burst in the interplanetary medium, we find that the radio-loud (RL) shocks produce a much larger SC/SI amplitude (average approx. 32 nT) compared to the radio-quiet (RQ) shocks (average approx. 19 nT). Clearly, RL shocks are more effective in producing SC/SIs than the RQ shocks. We also divided the IP shocks according to the type of IP counterpart of interplanetary CMEs (ICMEs): magnetic clouds (MCs) and nonmagnetic clouds. We find that the MC-associated shock speeds are better correlated with SC/SI amplitudes than those associated with non-MC ejecta. The SC/SI amplitudes are also higher for MCs than ejecta. Our results show that RL and RQ type of shocks are important parameters in producing the SC/SI amplitude

Solar flares induced D-region ionospheric and geomagnetic perturbations

The D-region ionospheric perturbations caused by solar flares occurred during January 2010 to February 2011, a low solar activity period of current solar cycle 24, have been examined on NWC transmitter signal (19.8 kHz) recorded at an Indian low latitude station, Allahabad (Geographic lat. 25.75 °N, long. 81.85 °E). A total of 41 solar flares, including 21 C-class, 19 M-class and 01 X-class, occurred during the daylight part of the NWC-Allahabad transmitter receiver great circle path. The local time dependence of solar flare effect on the change in the VLF amplitude (ΔA), time delay (Δt) between VLF peak amplitude and X-ray flux peak have been studied during morning, noon and evening periods of local daytime. Using the Long Wave Propagation Capability code V 2.1 the D-region reference height (H/) and sharpness factor (β) for each class of solar flare (C, M and X), have been estimated. It is found that D-region ionospheric parameters (H/, β) strongly depend on the local time of flares occurrence and their classes. The solar flare time electron density estimated by using H/ and β shows maximum increase in electron density of the order of ~80 as compared with normal day values. Electron density was found to increase exponentially with increase in the solar flux intensity. Solar flare effect on horizontal component (H) of the Earth’s magnetic field over an equatorial station, Tirunelveli (Geographic lat., 8.7°N, long., 77.8°E, dip lat., 0.4 ºN), shows a maximum increase in H of ~ 8.5% for M class solar flares. The increase in H is due to the additional magnetic field produced by the ionospheric electrojet over the equatorial station

Low - mid latitude D region ionospheric perturbations associated with 22 July 2009 total solar eclipse: wave -like signatures inferred from VLF observations

We present first report on the periodic wave-like signatures (WLS) in the D region ionosphere during 22 July 2009 total solar eclipse using JJI, Japan, very low frequency (VLF) navigational transmitter signal (22.2 kHz) observations at stations, Allahabad, Varanasi and Nainital in Indian Sector, Busan in Korea, and Suva in Fiji. The signal amplitude increased on 22 July by about 6 and 7 dB at Allahabad and Varanasi and decreased by about 2.7, 3.5, and 0.5 dB at Nainital, Busan, and Suva, respectively, as compared to 24 July 2009 (normal day). The increase/decrease in the amplitude can be understood in terms of modal interference at the sites of modes converted at the discontinuity created by the eclipse intercepting the different transmitter-receiver great circle paths. The wavelet analysis shows the presence of WLS of period ~16–40 min at stations under total eclipse and of period ~30–80 min at stations under partial eclipse (~85–54% totality) with delay times between ~50 and 100 min at different stations. The intensity of WLS was maximum for paths in the partially eclipsed region and minimum in the fully eclipsed region. The features of WLS on eclipse day seem almost similar to WLS observed in the nighttime of normal days (e.g., 24 July 2009). The WLS could be generated by sudden cutoff of the photo-ionization creating nighttime like conditions in the D region ionosphere and solar eclipse induced gravity waves coming to ionosphere from below and above. The present observations shed additional light on the current understanding of gravity waves induced D region ionospheric perturbations

TMEM16A calcium-activated chloride currents in supporting cells of the mouse olfactory epithelium

Glial-like supporting (or sustentacular) cells are important constituents of the olfactory epithelium that are involved in several physiological processes such as production of endocannabinoids, insulin, and ATP and regulation of the ionic composition of the mucus layer that covers the apical surface of the olfactory epithelium. Supporting cells express metabotropic P2Y purinergic receptors that generate ATP-induced Ca2+ signaling through the activation of a PLC-mediated cascade. Recently, we reported that a subpopulation of supporting cells expresses also the Ca2+-activated Cl- channel TMEM16A. Here, we sought to extend our understanding of a possible physiological role of this channel in the olfactory system by asking whether Ca2+ can activate Cl- currents mediated by TMEM16A. We use whole-cell patch-clamp analysis in slices of the olfactory epithelium to measure dose-response relations in the presence of various intracellular Ca2+ concentrations, ion selectivity, and blockage. We find that knockout of TMEM16A abolishes Ca2+-activated Cl- currents, demonstrating that TMEM16A is essential for these currents in supporting cells. Also, by using extracellular ATP as physiological stimuli, we found that the stimulation of purinergic receptors activates a large TMEM16A-dependent Cl- current, indicating a possible role of TMEM16A in ATP-mediated signaling. Altogether, our results establish that TMEM16A-mediated currents are functional in olfactory supporting cells and provide a foundation for future work investigating the precise physiological role of TMEM16A in the olfactory system

Time and causes of submergence of ancient temple structures off Mahabalipuram, East Coast of India

658-665As per traditional belief, some part of the ancient town of Mahabalipuram had been submerged just off the shore temple and this story has been recorded by the several British travelers during the 18th – 19th century. During the underwater exploration of Mahabalipuram area in 2017, three sites along with a large number of scattered dressed stones were found in the intertidal zone. Calcareous material grown over these stone structures after their submergence in seawater was subjected to radiocarbon (14C) dating to infer submergence time-periods of these structures. Submergence date for the site I is the late 14th century CE; whereas the submergence date from the site II comes ~ 1st century CE. According to the water-depths from where the studied structural remains were excavated, and obtained 14C dates of submergence, it could be surmised that these stone-structures off Mahabalipuram town were submerged in two phases. The submergence might have been induced by natural events such as coastal cyclone activity or Tsunami that flushed off sand around these structures and raised the sealevels locally over the coast