Detection of ultratrace levels of aqueous uranyl ions without using sophisticated analytical instrumentation and a tedious sample preparation method is a challenge for environmental monitoring and ...mitigation. Here we present a novel yet simple analytical method for highly sensitive and specific detection of uranyl ions via photoluminescence quenching of CdS quantum dots. We have demonstrated a new approach for synthesizing highly water-soluble and strong photoluminescence-emitting CdS quantum dots (i.e., CdS-MAA and CdS-MAA-TU) of sizes less than 3 nm. The structural, morphological, and optical properties of both the batches of CdS quantum dots were thoroughly characterized by XRD, high-resolution transmission electron microscopy (HRTEM), zeta potential, UV–visible absorption, and photoluminescence spectroscopy. Compared to the batch of CdS quantum dots prepared by capping with only mercaptoacetic acid (CdS-MAA), the batch prepared by capping with mercaptoacetic acid and thiourea in tandem (CdS-MAA-TU) exhibited higher quantum yield= 16.64 ± 1.02%, and more importantly, CdS-MAA-TU exhibited significantly a higher order of photoluminescence quenching responses when treated with ultratrace concentrations of uranyl ions. Under the optimized conditions, the sensitivity of detecting uranyl ion by CdS-MAA-TU was several folds better (0.316 L/ μg) than that of CdS-MAA (0.0053 (L/μg/), as determined from their respective Stern–Volmer plots. Qualitatively, CdS-MAA-TU probe can be used for visual detection of uranyl ions of concentration greater than 5 μg/L. However, the instrumental method of analysis based on photoluminescence spectroscopy confirmed the feasibility for quantitative analysis of ultratrace concentrations of uranyl ions as implied from a very low limit of detection (LoD = 0.07 μg/L) and limit of quantification (LoQ = and 0.231 μg/L). Systematic studies revealed very high selectivity for uranyl ion detection, though minor interference from Cu2+, Pb2+, Hg2+, CO3 2–, and SO4 2– was found. The recovery analysis performed by spiking uranyl ions (0.5 μg/L to 10.0 μg/L) in groundwater and river water samples, confirmed the robustness of the as-developed CdS-MAA-TU QDs for detecting ultratrace levels of uranyl ions in real water sample matrix. The very simple and effective strategy reported here should facilitate developing reliable sensors for detecting uranyl ion contamination in drinking water.
The meteor radar wind observations over Esrange (67.9°N, 21.10°E) and Rothera (67.5°S, 68.1°W), located respectively in the northern and southern polar latitudes show seasonal variation in the upper ...mesosphere and lower thermosphere (UMLT) winds with strong westward flow in the zonal wind and equatorward flow in the meridional wind during April‐September over Esrange and October‐February over Rothera. The semi‐diurnal tide shows larger amplitudes over Esrange than over Rothera. However, the diurnal tide (DT) shows comparable amplitudes in both stations. The DT amplitude decreases with height over both stations. Significant correlations between the DT amplitude and mean zonal wind (−0.74 for Esrange and −0.54 and −0.77 for Rothera) indicate the possible role of DT in driving the westward winds. The space‐time spectral analysis of the temperature obtained from the radiance observations of the SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) instrument on board the TIMED (Thermosphere Ionosphere Mesosphere Energetics Dynamics) satellite reveals the summer maximum of migrating diurnal tide of zonal wavenumber 1 (DW1) over both 60°N and 60°S, indicating that the DT is mostly composed of DW1. These results suggest that the westward winds in the polar UMLT region are largely driven by the westward momentum contributed by the DW1 tide due to its interaction with the background wind.
Plain Language Summary
The study provides an observational evidence for the influence of tides on the background wind flow at the polar upper mesospheric heights. The meteor radar observations over two polar latitude stations are used to study the seasonal and interannual variation of winds and investigate whether there is any relation between winds and tides. It is observed that stronger westward wind flows at the upper mesosphere lower thermospheric heights when the amplitude of diurnal tide is larger. Moreover, the amplitude of the diurnal tides is found to decrease with height, unlike the semi‐diurnal tidal amplitude, indicating the interaction of diurnal tide with background flow. Due to the tidal mean flow interaction, the diurnal tide which is mostly the westward propagating migrating diurnal tide (DW1), can drive the large westward wind through its westward momentum deposition into the background flow.
Key Points
Strong westward winds are observed when the amplitude of westward propagating diurnal tide is larger
The semi‐diurnal tidal amplitude increases with height, while the diurnal tidal amplitude decreases with height
Diurnal tide being the major source of westward momentum possibly drives the zonal wind flow due to its interaction with background flow
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► Higher order of lipid peroxidation for E. coli treated with higher concentrations of ZnO NPs. ► Higher lipid peroxidation was corroborated with bacteriostatic and bacteriocidal ...conditions. ► ROS induced lipid peroxidation confirmed from the use of antioxidants. ► Deformation, cell swelling and membrane disruptions observed from TEM and SEM.
Recent studies indicated the role of ROS toward antibacterial activity. In our study we report ROS mediated membrane lipid oxidation of Escherichia coli treated with ZnO nanoparticles (NPs) as supported by detection and spectrophotometric measurement of malondialdehyde (MDA) by TBARS (thiobarbituric acid-reactive species) assay. The antibacterial effects of ZnO NPs were studied by measuring the growth curve of E. coli, which showed concentration dependent bacteriostatic and bacteriocidal effects of ZnO NPs. The antibacterial effects were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Further, antibacterial effect of ZnO NPs was found to decrease by introducing histidine to the culture medium treated with ZnO NPs. The ROS scavenging action of histidine was confirmed by treating histidine to the batch of Escherichia coli+ZnO NPs at the end of the lag phase of the growth curve (Set-I) and during inoculation (Set-II). A moderate bacteriostatic effect (lag in the E. coli growth) was observed in Set-II batch while Set-I showed no bacteriostatic effect. From these evidences we confirmed that the antibacterial effect of bare as well as TG capped ZnO NPs were due to membrane lipid peroxidation caused by the ROS generated during ZnO NPs interaction in culture medium.
Abstract
Using a sample of 38 radio-loud galaxy mergers at z ≤ 0.2, we confirm the high detection rate (∼84 per cent) of H i 21-cm absorption in mergers, which is significantly higher (∼4 times) than ...in non-mergers. The distributions of the H i column density $N(\rm{H\,{\small I}}$) and velocity shift of the absorption with respect to the systemic redshift of the galaxy hosting the radio source in mergers are significantly different from that in non-mergers. We investigate the connection of the nuclear H i gas with various multiwavelength properties of the mergers. While the inferred $N(\rm{H\,{\small I}}$) and gas kinematics do not show strong (i.e. ≥3σ level) correlation with galaxy properties, we find that the incidence and $N(\rm{H\,{\small I}}$) of absorption tend to be slightly higher at smaller projected separations between the galaxy pairs and among the lower stellar mass-radio galaxies. The incidence, $N(\rm{H\,{\small I}}$) and line width of H i absorption increase from the pre-merger to the post-merger stages. The 100 per cent detection rate in post-mergers indicates that the neutral gas in the circumnuclear regions survives the coalescence period and is not yet quenched by the nuclear radio activity.
The paper presents the bearing ratio behavior of sand overlying clay with two woven and two non-woven treated coir geotextiles at the interface. The chemicals such as p-aminophenol, sodium periodate ...and sodium hydroxide were used to treat the coir geotextiles. The results indicated that the unsoaked/soaked bearing ratio of the sand overlying clay with woven coir geotextiles at the interface decreased after the chemical treatment whereas the trend was reverse in case non-woven geotextiles. The unsoaked bearing ratio of the sand overlying clay with the treated/untreated woven and non-woven coir geotextiles at the interface was higher than the soaked bearing ratio. The C: O ratio both for the woven and the non-woven coir geotextiles increased after the chemical treatment. The emissions of Si increased for the woven coir geotextiles whereas it decreased for the non-woven coir geotextiles after the chemical treatment. The chemical treatment results in the modification of the surface of both the untreated woven and non-woven coir geotextiles.
The 2021 August 14 MW 7.2 Nippes, Haiti earthquake occurred 75 km west of the epicenter of the 2010 Leogane earthquake (Haiti) on the transpressive Caribbean ‐ North America plate boundary. We ...present an updated fault map for Hispaniola and model coseismic and early postseismic fault slip using Interferometric Synthetic Aperture Radar and pixel offsets. We find the earthquake ruptured multiple segments of the Enriquillo‐Plantain Garden Fault Zone. Slip occurred in two main sub‐events on either side of a restraining bend at Pic Macaya, with ∼2.7 m of peak reverse‐slip east of the bend. To the west, slip jumps the restraining bend and further ruptures with ∼1.2 m of left‐lateral slip. Afterslip in the 4 days following the event occurred at shallow depth and adjacent to the coseismic rupture areas and reached the surface east of Pic Macaya.
Plain Language Summary
On 14 August 2021, a large MW7.2 earthquake struck southwestern Haiti, 75 km to the west of the 2010 Leogane, Haiti earthquake. We use remotely‐sensed data from two Synthetic Aperture Radar missions, ALOS‐2 and Sentinel‐1, and a new fault map database to study the earthquake and try to determine which faults slipped and where, and how much. We built a model of fault slip during the earthquake and aseismic slip that followed the earthquake, called afterslip. By comparing our results with previously published results using seismic data, we suggest that the earthquake started out with reverse slip on the Enriquillo‐Plantain Garden Fault Zone (EPGFZ) near the hypocenter. It then jumped the restraining bend in the EPGFZ near Pic Macaya, and ruptured west of the restraining bend with left‐lateral slip. The earthquake appears to be very complex and ruptured multiple faults. Afterslip in the 4 days following the earthquake was nearly as large as the earthquake, reaching the surface after ∼3 days. Taken together, the modeling results paint a picture of a complex fault system with highly variable stress and stability.
Key Points
The 2021 Haiti earthquake ruptured the Enriquillo‐Plantain Garden Fault as thrust slip east of Pic Macaya and left‐lateral slip to the west
Slip occurred on multiple fault segments and jumped across the restraining bend at Pic Macaya
InSAR observations indicate afterslip in the 4 days following the event of a similar magnitude to the coseismic slip
The combined effect of microstructure and crystallographic texture on the anisotropy in Charpy impact toughness has been studied in two hot-rolled low-carbon steel plates having different sulphur ...contents: 0.03wt% S in high-sulphur, HS, steel and 0.01wt% S in low-sulphur, LS, steel. Sub-size Charpy impact specimens were prepared from the rolled plates along 0°, 30°, 60° and 90° to the rolling direction and tested over the temperature range of +40°C to −196°C. Microstructure, inclusions and crystallographic texture have been characterized on the plane parallel to the fracture plane of each sample. The variation in upper shelf energy (USE) was more severe (∼69%) in HS steel due to the presence of coarse and elongated MnS inclusions. Crystallographic texture, especially, higher fraction of alpha- to gamma-fibre texture and stronger cube texture resulted in stronger variation in ductile to brittle transition temperature (DBTT) in LS steel (by ∼26°C). Increase in the fraction of {001} planes of the crystals on the fracture plane of the sample increased the DBTT by helping the cleavage crack propagation. On the other hand, increase in the fraction of {110} planes of the crystals on the shear planes (inclined at 45° to fracture plane) increased the USE by promoting the plastic deformation.
Activated carbon derived from biomasses with different oxygen‐bearing chemical constituents has been explored as supercapacitor electrode. The rice straw (RS) and eucalyptus wood biomasses were ...selected owing to their contrasting composition of cellulose, hemicellulose, and lignin contents. The activated carbons of these biomasses are obtained by pyrolysis at 550°C followed by thermal activation (700°C) after treatment with optimized KOH. The specific capacitance of RS‐based activated carbon (ACRS‐700), measured from galvanostatic charging‐discharging studies at 0.5 A g−1, is much higher (eg, 365 F g−1) than that of ACEW‐700 (168 F g−1). The higher specific capacitance of ACRS‐700 is attributable to: (i) significantly higher surface area (3345 m2 g−1) comprising of interconnected micro‐ and mesoporous structure; (ii) porosity of about 2.0 cm3/g; and (iii) oxygen‐rich hemicellulose contents. The possible charge storage mechanism in ACRS‐700 has been discussed. The real‐time application of ACRS‐700 has been demonstrated by lighting up red LEDs using ACRS‐700//ACRS‐700 symmetric supercapacitor device, operated with aqueous and freshly synthesized Bu4N+NO3− ionic liquid as electrolytes. The maximum energy density (42.7 Wh kg−1) and the power density (1.9 kW kg−1) for ionic liquid electrolyte are favourable for supercapacitor applications.
ABSTRACT
We present a study of the environment of 27 z = 3–4.5 bright quasars from the MUSE Analysis of Gas around Galaxies (MAGG) survey. With medium-depth Multi Unit Spectroscopic Explorer (MUSE) ...observations (4 h on target per field), we characterize the effects of quasars on their surroundings by studying simultaneously the properties of extended gas nebulae and Ly α emitters (LAEs) in the quasar host haloes. We detect extended (up to ≈100 kpc) Ly α emission around all MAGG quasars, finding a very weak redshift evolution between z = 3 and z = 6. By stacking the MUSE datacubes, we confidently detect extended emission of C iv and only marginally detect extended He ii up to ≈40 kpc, implying that the gas is metal enriched. Moreover, our observations show a significant overdensity of LAEs within 300 $\rm km~s^{-1}$ from the quasar systemic redshifts estimated from the nebular emission. The luminosity functions and equivalent width distributions of these LAEs show similar shapes with respect to LAEs away from quasars suggesting that the Ly α emission of the majority of these sources is not significantly boosted by the quasar radiation or other processes related to the quasar environment. Within this framework, the observed LAE overdensities and our kinematic measurements imply that bright quasars at z = 3–4.5 are hosted by haloes in the mass range $\approx 10^{12.0}\small{--}10^{12.5}~\rm M_\odot$.
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