ABSTRACT
A new upper limit on the 21 cm signal power spectrum at a redshift of z ≈ 9.1 is presented, based on 141 h of data obtained with the Low-Frequency Array (LOFAR). The analysis includes ...significant improvements in spectrally smooth gain-calibration, Gaussian Process Regression (GPR) foreground mitigation and optimally weighted power spectrum inference. Previously seen ‘excess power’ due to spectral structure in the gain solutions has markedly reduced but some excess power still remains with a spectral correlation distinct from thermal noise. This excess has a spectral coherence scale of 0.25–0.45 MHz and is partially correlated between nights, especially in the foreground wedge region. The correlation is stronger between nights covering similar local sidereal times. A best 2-σ upper limit of $\Delta ^2_{21} \lt (73)^2\, \mathrm{mK^2}$ at $k = 0.075\, \mathrm{h\, cMpc^{-1}}$ is found, an improvement by a factor ≈8 in power compared to the previously reported upper limit. The remaining excess power could be due to residual foreground emission from sources or diffuse emission far away from the phase centre, polarization leakage, chromatic calibration errors, ionosphere, or low-level radiofrequency interference. We discuss future improvements to the signal processing chain that can further reduce or even eliminate these causes of excess power.
The genus Moringa Adans. comprises 13 species, of which Moringa oleifera Lam. native to India and cultivated across the world owing to its drought and frost resistance habit is widely used in ...traditional phytomedicine and as rich source of essential nutrients. Wide spectrum of phytochemical ingredients among leaf, flower, fruit, seed, seed oil, bark, and root depend on cultivar, season, and locality. The scientific studies provide insights on the use of M. oleifera with different aqueous, hydroalcoholic, alcoholic, and other organic solvent preparations of different parts for therapeutic activities, that is, antibiocidal, antitumor, antioxidant, anti‐inflammatory, cardio‐protective, hepato‐protective, neuro‐protective, tissue‐protective, and other biological activities with a high degree of safety. A wide variety of alkaloid and sterol, polyphenols and phenolic acids, fatty acids, flavanoids and flavanol glycosides, glucosinolate and isothiocyanate, terpene, anthocyanins etc. are believed to be responsible for the pragmatic effects. Seeds are used with a view of low‐cost biosorbent and coagulant agent for the removal of metals and microbial contamination from waste water. Thus, the present review explores the use of M. oleifera across disciplines for its prominent bioactive ingredients, nutraceutical, therapeutic uses and deals with agricultural, veterinarian, biosorbent, coagulation, biodiesel, and other industrial properties of this “Miracle Tree.”
Increasing anthropogenic and biogenic emissions of precursor compounds have led to high tropospheric ozone concentrations in India particularly in Indo-Gangetic Plains, which is the most fertile and ...cultivated area of this rapidly developing country. Current ozone risk models, based on European and North American data, provide inaccurate estimations for crop losses in India. During the past decade, several ozone experiments have been conducted with the most important Indian crop species (e.g. wheat, rice, mustard, mung bean). Experimental work started in natural field conditions around Varanasi area in early 2000's, and the use of open top chambers and EDU (ethylene diurea) applications has now facilitated more advanced studies e.g. for intra-species sensitivity screening and mechanisms of tolerance. In this review, we identify and discuss the most important gaps of knowledge and future needs of action, e.g. more systematic nationwide monitoring for precursor and ozone formation over Indian region.
Tropospheric ozone is an increasing threat to food production in India.
Aim: The present study was undertaken to evaluate the performance of different algorithms for flattening filter-free (FFF) and flattened (FF) photon beams in three different in-homogeneities.
...Materials and Method: Computed tomography (CT) image sets of the CIRS phantom maintained in the SAD setup by placing the ionization chamber in the lung, bone, and tissue regions, respectively, were acquired. The treatment planning system (TPS) calculated and the ionization chamber measured the doses at the center of the chamber (in the three mediums) were recorded for the flattened and non-flattened photon beams.
Results: The results were reported for photon energies of 6 MV, 10 MV, 15 MV, 6 FFF, and 10 FFF of field sizes 5 × 5 cm2, 10 × 10 cm2, and 15 × 15 cm2. In the bone inhomogeneity, the pencil beam algorithm predicted that the maximum dose variation was 4.88% of measured chamber dose in 10-MV photon energy for the field size 10 × 10 cm2. In water inhomogeneity, both the collapsed cone and Monte Carlo algorithm predicted that the maximum dose variation was ± 3% of measured chamber dose in 10-MV photon energy for the field size 10 × 10 cm2 and in 10-MV FFF photon energy for the field size 5 × 5 cm2, whereas in lung inhomogeneity, the pencil beam algorithm predicted that the highest dose variation was - 6.9% of measured chamber dose in 10-MV FFF photon energy for the field size 5 × 5 cm2.
Conclusion: FF and FFF beams performed differently in lung, water, and bone mediums. The assessment of algorithms was conducted using the anthropomorphic phantom; therefore, these findings may help in the selection of appropriate algorithms for particular clinical settings in radiation delivery.
ABSTRACT
Observations of the redshifted 21-cm hyperfine line of neutral hydrogen from early phases of the Universe such as Cosmic Dawn and the Epoch of Reionization promise to open a new window onto ...the early formation of stars and galaxies. We present the first upper limits on the power spectrum of redshifted 21-cm brightness temperature fluctuations in the redshift range z = 19.8–25.2 (54–68 MHz frequency range) using 14 h of data obtained with the LOFAR-Low Band Antenna (LBA) array. We also demonstrate the application of a multiple pointing calibration technique to calibrate the LOFAR-LBA dual-pointing observations centred on the North Celestial Pole and the radio galaxy 3C220.3. We observe an unexplained excess of $\sim 30\!-\!50{{\ \rm per\ cent}}$ in Stokes / noise compared to Stokes V for the two observed fields, which decorrelates on ≳12 s and might have a physical origin. We show that enforcing smoothness of gain errors along frequency direction during calibration reduces the additional variance in Stokes I compared Stokes V introduced by the calibration on sub-band level. After subtraction of smooth foregrounds, we achieve a 2σ upper limit on the 21-cm power spectrum of $\Delta _{21}^2 \lt (14561\, \text{mK})^2$ at $k\sim 0.038\, h\, \text{cMpc}^{-1}$ and $\Delta _{21}^2 \lt (14886\, \text{mK})^2$ at $k\sim 0.038 \, h\, \text{cMpc}^{-1}$ for the 3C220 and NCP fields respectively and both upper limits are consistent with each other. The upper limits for the two fields are still dominated by systematics on most k modes.
ABSTRACT
The ARCADE2 and LWA1 experiments have claimed an excess over the cosmic microwave background (CMB) at low radio frequencies. If the cosmological high-redshift contribution to this radio ...background is between 0.1 per cent and 22 per cent of the CMB at 1.42 GHz, it could explain the tentative EDGES low-band detection of the anomalously deep absorption in the 21-cm signal of neutral hydrogen. We use the upper limit on the 21-cm signal from the Epoch of Reionization (z = 9.1) based on 141 h of observations with LOFAR to evaluate the contribution of the high-redshift Universe to the detected radio background. Marginalizing over astrophysical properties of star-forming haloes, we find (at 95 per cent CL) that the cosmological radio background can be at most 9.6 per cent of the CMB at 1.42 GHz. This limit rules out strong contribution of the high-redshift Universe to the ARCADE2 and LWA1 measurements. Even though LOFAR places limit on the extra radio background, excess of 0.1–9.6 per cent over the CMB (at 1.42 GHz) is still allowed and could explain the EDGES low-band detection. We also constrain the thermal and ionization state of the gas at z = 9.1, and put limits on the properties of the first star-forming objects. We find that, in agreement with the limits from EDGES high-band data, LOFAR data constrain scenarios with inefficient X-ray sources, and cases where the Universe was ionized by stars in massive haloes only.
We analyze charged-current electron-neutrino cross sections on Carbon. We consider two different theoretical approaches, on one hand the Continuum Random Phase Approximation (CRPA) which allows a ...description of giant resonances and quasielastic excitations, on the other hand the RPA-based calculations which are able to describe multinucleon emission and coherent and incoherent pion production as well as quasielastic excitations. We compare the two approaches in the genuine quasielastic channel, and find a satisfactory agreement between them at large energies while at low energies the collective giant resonances show up only in the CRPA approach. We also compare electron-neutrino cross sections with the corresponding muon-neutrino ones in order to investigate the impact of the different charged-lepton masses. Finally, restricting to the RPA-based approach we compare the sum of quasielastic, multinucleon emission, coherent and incoherent one-pion production cross sections (folded with the electron-neutrino T2K flux) with the charged-current inclusive electron-neutrino differential cross sections on Carbon measured by T2K. We find a good agreement with the data. The multinucleon component is needed in order to reproduce the T2K electron-neutrino inclusive cross sections.
Detection of the 21-cm signal coming from the epoch of reionization (EoR) is challenging especially because, even after removing the foregrounds, the residual Stokes I maps contain leakage from ...polarized emission that can mimic the signal. Here, we discuss the instrumental polarization of Low Frequency Array (LOFAR) and present realistic simulations of the leakages between Stokes parameters. From the LOFAR observations of polarized emission in the 3C196 field, we have quantified the level of polarization leakage caused by the nominal model beam of LOFAR, and compared it with the EoR signal using power spectrum analysis. We found that at 134–166 MHz, within the central 4° of the field the (Q, U) → I leakage power is lower than the EoR signal at k < 0.3 Mpc−1. The leakage was found to be localized around a Faraday depth of 0, and the rms of the leakage as a fraction of the rms of the polarized emission was shown to vary between 0.2 and 0.3 per cent, both of which could be utilized in the removal of leakage. Moreover, we could define an ‘EoR window’ in terms of the polarization leakage in the cylindrical power spectrum above the point spread function (PSF)-induced wedge and below k
∥ ∼ 0.5 Mpc−1, and the window extended up to k
∥ ∼ 1 Mpc−1 at all k
⊥ when 70 per cent of the leakage had been removed. These LOFAR results show that even a modest polarimetric calibration over a field of view of ≲ 4° in the future arrays like Square Kilometre Array will ensure that the polarization leakage remains well below the expected EoR signal at the scales of 0.02–1 Mpc−1.
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