ABSTRACT
We present a detailed study on SN2019szu, a Type I superluminous supernova at z = 0.213 that displayed unique photometric and spectroscopic properties. Pan-STARRS and ZTF forced photometry ...show a pre-explosion plateau lasting ∼40 d. Unlike other SLSNe that show decreasing photospheric temperatures with time, the optical colours show an apparent temperature increase from ∼15 000 to ∼20 000 K over the first 70 d, likely caused by an additional pseudo-continuum in the spectrum. Remarkably, the spectrum displays a forbidden emission line (likely attributed to λλ7320,7330) visible 16 d before maximum light, inconsistent with an apparently compact photosphere. This identification is further strengthened by the appearances of O iii λλ4959, 5007, and O iii λ4363 seen in the spectrum. Comparing with nebular spectral models, we find that the oxygen line fluxes and ratios can be reproduced with ∼0.25 M⊙ of oxygen-rich material with a density of $\sim 10^{-15}\, \rm {g\, cm}^{-3}$. The low density suggests a circumstellar origin, but the early onset of the emission lines requires that this material was ejected within the final months before the terminal explosion, consistent with the timing of the precursor plateau. Interaction with denser material closer to the explosion likely produced the pseudo-continuum bluewards of ∼5500 Å. We suggest that this event is one of the best candidates to date for a pulsational pair-instability ejection, with early pulses providing the low density material needed for the formation of the forbidden emission line, and collisions between the final shells of ejected material producing the pre-explosion plateau.
We present a detailed study on SN2019szu, a Type I superluminous supernova at \(z=0.213\), that displayed unique photometric and spectroscopic properties. Pan-STARRS and ZTF forced photometry shows a ...pre-explosion plateau lasting \(\sim\) 40 days. Unlike other SLSNe that show decreasing photospheric temperatures with time, the optical colours show an apparent temperature increase from \(\sim\)15000\,K to \(\sim\)20000\,K over the first 70 days, likely caused by an additional pseudo-continuum in the spectrum. Remarkably, the spectrum displays a forbidden emission line even during the rising phase of the light curve, inconsistent with an apparently compact photosphere. We show that this early feature is O II \(\lambda\lambda\)7320,7330. We also see evidence for O III \(\lambda\lambda\)4959, 5007, and O III \(\lambda\)4363 further strengthening this line identification. Comparing with models for nebular emission, we find that the oxygen line fluxes and ratios can be reproduced with \(\sim\)0.25\,M\(_{\odot}\) of oxygen rich material with a density of \(\sim10^{-15}\,\rm{g\,cm}^{-3}\). The low density suggests a circumstellar origin, but the early onset of the emission lines requires that this material was ejected within the final months before the terminal explosion, consistent with the timing of the precursor plateau. Interaction with denser material closer to the explosion likely produced the pseudo-continuum bluewards of \(\sim\)5500\,\(\Angstrom\). We suggest that this event is one of the best candidates to date for a pulsational pair-instability ejection, with early pulses providing the low density material needed for the forbidden emission line, and collisions between the final shells of ejected material producing the pre-explosion plateau.
A black hole can launch a powerful relativistic jet after it tidally disrupts a star. If this jet fortuitously aligns with our line of sight, the overall brightness is Doppler boosted by several ...orders of magnitude. Consequently, such on-axis relativistic tidal disruption events (TDEs) have the potential to unveil cosmological (redshift \(z>\)1) quiescent black holes and are ideal test beds to understand the radiative mechanisms operating in super-Eddington jets. Here, we present multi-wavelength (X-ray, UV, optical, and radio) observations of the optically discovered transient \target at \(z=1.193\). Its unusual X-ray properties, including a peak observed luminosity of \(\gtrsim\)10\(^{48}\) erg s\(^{-1}\), systematic variability on timescales as short as 1000 seconds, and overall duration lasting more than 30 days in the rest-frame are traits associated with relativistic TDEs. The X-ray to radio spectral energy distributions spanning 5-50 days after discovery can be explained as synchrotron emission from a relativistic jet (radio), synchrotron self-Compton (X-rays), and thermal emission similar to that seen in low-redshift TDEs (UV/optical). Our modeling implies a beamed, highly relativistic jet akin to blazars but requires extreme matter-domination, i.e, high ratio of electron-to-magnetic field energy densities in the jet, and challenges our theoretical understanding of jets.
During an ongoing pandemic of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-Cov-2), main question which has arisen in everyone's mind is about the immune response that may protects from ...reinfection. Coronaviruses are known for short term immunity. Their ability of mutations enables them to escape host immunity, thus increasing chances of reinfection. Here we report two cases of reinfection among healthcare workers who presented with symptoms of COVID 19 disease, after 03 months of first infectious course. Such documentations are necessary for epidemiological purposes and also to monitor response of virus on re exposure.
Crop improvement through transgenic technologies is commonly tagged with GMO (genetically-modified-organisms) where the presence of transgene becomes a big question for the society and the ...legislation authorities. However, new plant breeding techniques like CRISPR/Cas9 system clustered regularly interspaced palindromic repeats (CRISPR)-associated 9 can overcome these limitations through transgene-free products. Potato (
L.) being a major food crop has the potential to feed the rising world population. Unfortunately, the cultivated potato suffers considerable production losses due to several pre- and post-harvest stresses such as plant viruses (majorly RNA viruses) and cold-induced sweetening (CIS; the conversion of sucrose to glucose and fructose inside cell vacuole). A number of strategies, ranging from crop breeding to genetic engineering, have been employed so far in potato for trait improvement. Recently, new breeding techniques have been utilized to knock-out potato genes/factors like eukaryotic translation initiation factors
and isoform
), that interact with viruses to assist viral infection, and vacuolar invertase, a core enzyme in CIS. In this context, CRISPR technology is predicted to reduce the cost of potato production and is likely to pass through the regulatory process being marker and transgene-free. The current review summarizes the potential application of the CRISPR/Cas9 system for traits improvement in potato. Moreover, the prospects for engineering resistance against potato fungal pathogens and current limitations/challenges are discussed.
Increase in N application rates may eventually raise the potential groundwater N-pollution. This survey study was conducted by Soil Chemistry Section, ISCES to assess the NO3 contents of soil from 0 ...to 120 cm depth with different intervals. For this purpose, the soil and water samples were collected from Okara, Vehari Sialkot, Chiniot, Hafizabad, Sahiwal and Multan districts. The results showed that nitrate leaching occurred but it is only up to 2 feet soil depth. The NO3-N contents were maximum at two upper depths (i.e. 0-30 cm and 30-60 cm) and then decreased gradually downward. The highest average NO3-N content was found at 0-30 cm soil depth and the lowest were found at 90-120 cm. The data also revealed that mean NO3-N content at 0-30, 30-60, 60-90 and 90-120 cm depths were 16.85±4.05, 15.21±4.77, 9.94±3.36 and 6.54±2.62 mg kg-1, respectively, whereas NO3-N content at same depths were ranged from 11.50-26.20, 6.53-21.15, 5.24-16.12, 1.45-9.36 mg kg-1, respectively. The results regarding underground water samples (tube well) from the same sites from all the three districts showed that NO3 were found in all the water samples but it was only in traces and their concentration were not much higher to create the health hazardous problem owing to NO3 leaching. The data showed that the highest NO3 contents did not exceed than 8.61 and 10.6 ppm in Multan and Sahiwal districts respectively, which were much lower than permissible limit i.e. 50 ppm (FAO). Similarly, the nitrate content in underground water are well below the maximum admissible limit of WHO i.e. 50 mg L-1.
BACKGROUND: Although tyrosine kinase inhibitors (TKIs) are the gold standard in clinical management of chronic myeloid leukemia, it is not feasible to use these drugs in at least some cases when ...patients are resistance to all available TKIs due to compound BCR-ABL mutations, due to patient safety profile or due to the nonavailability of drugs in developing countries on account of cost or logistic issues. We reported earlier that interferon alpha can eradicate compound BCR-ABL mutations and induce stable responses. Here, we report a follow-up of this study. PATIENTS AND METHODS: Some chronic myeloid leukemia (CML) patients did not get TKIs directly because of very high cost of imatinib and were given interferon alpha (experimental group) until the provision of imatinib free of cost through GLIVEC® International Patient Assistance Program while the other groups of patients (control group) were directly given imatinib. A very sensitive allele-specific polymerase chain reaction was employed to detect BCR-ABL compound mutations before treatment and confirmation of mutations was carried out using reliable molecular assays. Mutations were reinvestigated at all important time points during the long-term follow-up studies. RESULTS: The use of interferon-alpha for 6 months prior to TKIs eradicated compound BCR-ABL mutations (Phe311Val/Met351Thr and Thr315Ile/Phe311Val/Met351Thr) and provided deep molecular responses without any progression or mortality in CML patients (experimental group) as compared with patients who did not use interferon and was directly given TKIs (control group). CONCLUSIONS: Interferon alpha can eradicate highly resistant BCR-ABL mutations and lead to durable deep molecular responses to TKIs in CML. Therefore, interferon-alpha is recommended for CML patients with compound mutations resistant to TKIs, specifically in those scenarios where some TKIs are not available or not safe to use for CML patients. Our long-term follow-up study is well supported by recently published literature.
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