Search

Abstract Ultra-low mass primordial black holes (PBH), briefly dominating the expansion of the universe, would leave detectable imprints in the secondary stochastic gravitational wave background (SGWB). Such a scenario leads to a characteristic doubly peaked spectrum of SGWB and strongly depends on the Hawking evaporation of such light PBHs. However, these observable signatures are significantly altered if the memory burden effect during the evaporation of PBHs is taken into account. We show that for the SGWB induced by PBH density fluctuations, the memory burden effects on the Hawking evaporation of ultra-low mass PBHs can mimic the signal arising due to the non-standard reheating epoch before PBH domination. Finally, we point out that this degeneracy can be broken by the simultaneous detection of the first peak in the SGWB, which is typically induced by the inflationary adiabatic perturbations.

Abstract The Hubble tension refers to the discrepancy in the value of the Hubble constant $$H_0$$ H 0 inferred from the cosmic microwave background observations, assuming the concordance $$\Lambda $$ Λ CDM model of the Universe, and that from the distance ladder and other direct measurements. In order to alleviate this tension, we construct a plausible dark energy scenario, within the framework of Horndeski gravity which is one of the most general scalar–tensor theories yielding second-order equations. In our set-up, we include the self-interactions and nonminimal coupling of the dynamical dark energy scalar field which enable very interesting dynamics leading to a phantom behaviour at low redshifts along with negative dark energy densities at high redshifts. These two features together make this model a promising scenario to alleviate the Hubble tension for appropriate choices of the model parameters. Towards a consistent model building, we show that this set-up is also free from both the gradient and ghost instabilities. Finally, we confront the predictions of the model with low redshift observations from Pantheon, SH0ES, cosmic chronometers and BAO, to obtain best fit constraints on model parameters.

Background Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has created high demand for molecular kits and consumables for mass screening of suspected individuals. Direct real-time polymerase chain reaction (RT-PCR) assay without nucleic acid extraction has several advantages in saving testing time and cost and helps in the rapid reporting of SARS-CoV-2. The present study evaluated the analytical performance of four SARS-CoV-2 RT-PCR for direct RT-PCR testing using preheated specimens.

Abstract The Laser Interferometer Space Antenna (LISA) has two scientific objectives of cosmological focus: to probe the expansion rate of the universe, and to understand stochastic gravitational-wave backgrounds and their implications for early universe and particle physics, from the MeV to the Planck scale. However, the range of potential cosmological applications of gravitational-wave observations extends well beyond these two objectives. This publication presents a summary of the state of the art in LISA cosmology, theory and methods, and identifies new opportunities to use gravitational-wave observations by LISA to probe the universe.

Abstract Ultra-low mass primordial black holes (PBH), which may briefly dominate the energy density of the universe but completely evaporate before the big bang nucleosynthesis (BBN), can lead to interesting observable signatures. In our previous work, we studied the generation of a doubly peaked spectrum of induced stochastic gravitational wave background (ISGWB) for such a scenario and explored the possibility of probing a class of baryogenesis models wherein the emission of massive unstable particles from the PBH evaporation and their subsequent decay contributes to the matter-antimatter asymmetry. In this work, we extend the scope of our earlier work by including spinning PBHs and consider the emission of light relativistic dark sector particles, which contribute to the dark radiation (DR) and massive stable dark sector particles, thereby accounting for the dark matter (DM) component of the universe. The ISGWB can probe the non-thermal production of these heavy DM particles, which cannot be accessible in laboratory searches. For the case of DR, we find a novel complementarity between the measurements of ∆N eff from these emitted particles and the ISGWB from PBH domination. Our results indicate that the ISGWB has a weak dependence on the initial PBH spin. However, for gravitons as the DR particles, the initial PBH spin plays a significant role, and only above a critical value of the initial spin parameter a *, which depends only on initial PBH mass, the graviton emission can be probed in the CMB-HD experiment. Upcoming CMB experiments such as CMB-HD and CMB-Bharat, together with future GW detectors like LISA and ET, open up an exciting possibility of constraining the PBHs parameter space providing deeper insights into the expansion history of the universe between the end of inflation and BBN.

Introduction: Novel Coronavirus Disease-2019 (COVID-19) caused by the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) has resulted in an unprecedented global pandemic. Real Time Polymerase Chain Reaction (RT-PCR) tests are being used in the diagnosis of COVID-19 worldwide however mutations in the SARS-CoV-2 genome have generated many SARS-CoV-2 genome variants and which may affect the correct Reverse transcriptase-Real time Polymerase Chain Reaction (RT-PCR) diagnosis. Aim: To confirm and study the incidence of the non amplification of the SARS-CoV-2 Nucleocapsid gene (N gene) target among known SARS-CoV-2 positive samples. Materials and Methods: This retrospective observational study was carried out at the State Virology Laboratory, Gandhi Medical College, Bhopal, Madhya Pradesh, India, during January to May 2021. During the study period, a total of 159 SARS-CoV-2 positive samples were failed to amplify the N gene target. To investigate the non amplification of N gene target of SARS-CoV-2, a total of 20 samples were selected and retested using the initially used RT-PCR kit (VIRALDTECT RT-PCR kit) and also with the two different RT-PCR kits (TaqPath RT-PCR kit and Hi-PCR RT-PCR kit) which also contain primers/probes for the SARS-CoV-2 N gene target. Results: Amplification and detection of the SARS-CoV-2 N target gene was not observed in VIRALDTECT RT-PCR test results. In contrast, amplification was detected in the N gene target of SARS-CoV-2 while using the TaqPath and Hi-PCR kits. Obtained results confirm the failure of the annealing of VIRALDTECT kit N gene primer/probe and suggest the possible mutation event in the SARS-CoV-2 N gene among the N gene non amplified samples. Conclusion: Present study reports, the incidence of non amplification of SARS-CoV-2 N gene, where the RT-PCR kit failed to detect N gene target and seriously affect RT-PCR diagnosis. Hence, the study emphasises the revalidation of commercially available SARS-CoV-2, RT-PCR kits to identify these kinds of failure incidence.

Introduction: The COVID-19 pandemic has resulted in an increased need for molecular diagnostics. Ribonucleic acid (RNA) extraction is a crucial step in the detection of severe acute respiratory syndrome coronavirus-2 (SARS-COV-2). The resulting outcome depends on the performance of the RNA extraction kit used. Methods: This study evaluated the efficiency of four different commercial RNA extraction kits for the detection of SARS-COV 2. The reproducibility and performance efficiency of each kit were assessed and compared. The performance, processing time and storage conditions were also considered in the evaluation. Results: A slightly lesser cycle threshold (Ct) values were observed in RNA extracted using HiPurA Viral RNA Purification Kit. Invitrogen PureLink RNA Mini Kit was found to be time-saving and user-friendly. Conclusions: All the RNA isolation kit yielded the best results; however, if time is the important considerations, Invitrogen PureLink RNA Mini Kit has the shortest processing time.

Objectives The present COVID-19 pandemic resulted in an increased need for molecular diagnostic testing. Delay in the specimen processing and suboptimal storage of suspected samples in laboratories leads to degradation of SARS-CoV-2 viral RNA. Viral lysis buffers from RNA extraction kits have the potential to stabilize RNA. Hence, this study aimed to investigate the stability of SARS-CoV-2 RNA in viral lysis buffer at different temperatures and time periods. Materials and Methods Aliquots of samples with known SARS-CoV-2 RNA were processed in viral lysis buffers simultaneously, stored separately at 2 to 8°C and 22 to 28°C for 24 hours, 48 hours and 72 hours. SARS-CoV-2 viral RNA was extracted from each aliquot and analyzed using multiplex real-time PCR. Results SARS-CoV-2 RNA in samples placed in viral lysis buffer was stable for 48 hours at both 2 to 8°C and 22 to 28°C temperatures. Slight decline in the viral RNA quantity was found on aliquots tested after 48 hours of both the temperatures. Conclusions Viral lysis buffer maintains the integrity of SARS-CoV-2 RNA for up to 48 hours even at room temperature and supports delayed diagnosis with an overwhelming sample load in testing laboratories.

Introduction: The whole world is facing an ongoing global health emergency of COVID-19 disease caused by the SARS-CoV-2. Real-Time Reverse Transcription-Polymerase Chain Reaction (RT-PCR) is a gold standard in the detection of SARS-CoV-2 infection. Presently, many single tube multiple gene target RTPCR kits have been developed and are commercially available for Corona Virus Disease 2019 (COVID-19) diagnosis. Aim: To evaluate the performance of seven COVID-19 RT-PCR kits (DiagSure, Meril, VIRALDTECT II, TruPCR, Q-line, Allplex and TaqPath) which are commercially available for COVID-19 RT-PCR diagnosis. Materials and Methods: This observational study was conducted at the State Virology Laboratory (SVL), Gandhi Medical College, Bhopal, Madhya Pradesh, India. Seven commercially available kits have been evaluated on the basis of: (i) number of SARS-CoV-2 specific gene target; (ii) human housekeeping genes as internal control; (iii) RT-PCR run time; and (iv) kit performances to correctly detect SARS-CoV-2 positive and negative RNA samples. A total of 50 RNA samples (left over RNA) were included, master mix preparation, template addition and RT-PCR test has been performed according to kits literature. At the end of PCR run, mean and standard deviation of obtained cut-off of all kits were calculated using Microsoft Excel. Results: All seven RT-PCR kits performed satisfactory regarding the reproducibility and they could correctly identify 30 positive and 20 negative RNA samples. RNA samples (group C) having low viral loads with a high Cycle threshold (Ct) value (>30) were also detected by all these seven kits. Obtained Ct values of each group was in parallel range in comparison with the initial testing Ct values. Kits were found to be superior which contains primers and probes for three SARS-CoV-2 specific gene targets, have human housekeeping gene as internal control and taking less time to complete RT-PCR. Conclusion: All seven COVID-19 RT-PCR kits included in this study demonstrated satisfactory performance and can be used for the routine molecular diagnosis of COVID-19 disease.

Introduction: Neonatal Cholestasis (NC) is defined as conjugated hyperbilirubinemia in infancy and diverse aetiologies and several disorders are responsible for this hepatobiliary dysfunction. Hepatotropic viral infection may have an important role in the pathogenesis of NC and related clinical outcomes. Aim: Hence, this study was aimed to estimate the seroprevalence of the hepatotropic viruses and their possible role in neonates presenting with cholestatic jaundice. Materials and Methods: This retrospective study included 51 infants who were presented with cholestatic jaundice. Serum samples were collected and screened for the hepatotropic viruses. The presence of serological markers to Cytomegalovirus (CMV), Epstein-Barr Virus (EBV), Hepatitis C (HCV), Hepatitis E (HEV), Herpes Simplex Virus (HSV) and Rubella were tested using enzyme-linked immunosorbent assays. Hepatitis B Virus (HBV) serostatus was determined by using rapid card tests. Results: Of the 51 cases, 4 (7.6%) patients presented with biliary atresia. Seroprevalence of CMV (23.5%) was found to be more predominant followed by EBV (13.7%), HCV (5.8%), HEV (5.8%), HSV (1.9%) and Rubella (1.9%). Co-infections were found in 7 (13.7%) cases and CMV-EBV co-infection being the most common. Conclusion: The presence of specific serological markers to hepatotropic viruses in the NC cases strongly suggests their aetiological role in this disorder. To the best of our knowledge, this is the first report documenting the seroprevalence of hepatotropic viruses in NC patients from Central India.

Abstract We present a unified evolution of the universe from very early times until the present epoch by including both the leading local correction $$R^2$$ R2 and the leading non-local term $$R\frac{1}{\square ^2}R$$ R1□2R to the classical gravitational action. We find that the inflationary phase driven by $$R^2$$ R2 term gracefully exits in a transitory regime characterized by coherent oscillations of the Hubble parameter. The universe then naturally enters into a radiation dominated epoch followed by a matter dominated era. At sufficiently late times after radiation–matter equality, the non-local term starts to dominate inducing an accelerated expansion of the universe at the present epoch. We further exhibit the fact that both the leading local and non-local terms can be obtained within the covariant effective field theory of gravity. This scenario thus provides a unified picture of inflation and dark energy in a single framework by means of a purely gravitational action without the usual need of a scalar field.

Following our previous work wherein the leading order effective action was computed in the covariant effective field theory of gravity, here we specialize the effective action to the FRW spacetime and obtain the effective Friedmann equations. In particular, we focus our attention on studying the cosmological implications of the non-local terms when each of them is combined with the Einstein–Hilbert action. We obtain both analytical and iterative solutions to the effective background equations in all the cases and also briefly comment on the consistency between the iterative and numerical solutions whenever possible. We find that among all the non–local terms, the imprints induced by are very significant. Interpreting these corrections as an effective dark energy component characterized by an equation of state parameter, we find that the correction can indeed lead to an accelerated expansion of the universe at the present epoch even in the absence of a cosmological constant. We briefly discuss some phenomenological consequences of our results. [ABSTRACT FROM AUTHOR]

We construct the covariant effective field theory of gravity as an expansion in inverse powers of the Planck mass, identifying the leading and next-to-leading quantum corrections. We determine the form of the effective action for the cases of pure gravity with cosmological constant as well as gravity coupled to matter. By means of heat kernel methods we renormalize and compute the leading quantum corrections to quadratic order in a curvature expansion. The final effective action in our covariant formalism is generally non-local and can be readily used to understand the phenomenology on different spacetimes. In particular, we point out that on curved backgrounds the observable leading quantum gravitational effects are less suppressed than on Minkowski spacetime. [ABSTRACT FROM AUTHOR]