Uranium standards in drinking water: An examination from scientific and socio-economic standpoints of India.

The detection of uranium in drinking water has ignited concerns among the public, regulators, and policymakers, particularly as around 1% of the 55,554 water samples in India have shown uranium levels surpassing the 60 µg/l guideline established by the Atomic Energy Regulatory Board (AERB) based on radiological toxicity. Further, the Bureau of Indian Standard (BIS), has given a limit of 30 µg/l, which is derived from World Health Organization (WHO) guidelines. Besides the chemical and radiological aspects associated with uranium, factors such as technological constraints in water purification, waste management, environmental factors, and socio-economic conditions significantly influence these guideline values, which are often overlooked. This manuscript explores the variations in approaches for establishing guideline values and highlights the uncertainties arising from dependence on various variables such as intake and usage patterns, inter- and intra-species distinctions, and epidemiological data. A critical analysis indicates that adherence to global guidelines may result in some undesirable environmental issues. By considering factors such as population dynamics, socio-economic conditions, and geological influences, we suggest that limit of 60 µg/l for uranium in drinking water is appropriate for India.

Comparing Intraoperative Blood Loss in Cemented, Uncemented, and Hybrid Total Hip Replacement for Neck of Femur Fractures.

Background As the aging population increases, osteoporotic neck of femur fracture cases will continue to rise. Although hemiarthroplasty or half hip replacement is the treatment of choice in a majority of patients, a small but definite cohort of patients would need a total hip replacement. In these elderly patients who often have comorbidities, the use of cement to fix the prosthesis is often quoted as beneficial in view of perceived lower blood loss compared to uncemented fixation of the prosthesis. However, the cementation of the implant in itself has inherent problems. This study examined three modalities of fixation of a prosthesis for total hip replacement in the neck of femur fractures, namely, cemented, hybrid, and uncemented, and compared their relative intraoperative blood loss. Methodology This is a retrospective study with a follow-up of two years. Patients who presented to a level 1 trauma center in an inner city metropolitan with neck of femur fractures and were treated by total hip replacement were included in the study. Intraoperative blood loss was calculated using Nadler's formula. Results There was no statistical difference in intraoperative blood loss in either of the three groups of patients, namely, cemented, hybrid, or uncemented total hip replacement for neck of femur fractures. Conclusions Intraoperative blood loss should not influence the modality of prosthesis fixation for total hip replacement in neck of femur fractures.

Controlling basal plane sulfur vacancy in water splitting MoSx/NiF electrocatalysts through electric-field-assisted pulsed laser ablation.

Eco-friendly, efficient, and durable electrocatalysts from earth-abundant materials are crucial for water splitting through hydrogen and oxygen generation. However, available methods to fabricate electrocatalysts are either hazardous and time-consuming or require expensive equipment, hindering the large-scale, eco-friendly production of artificial fuels. Here, we present a rapid, single-step method for producing MoSx/NiF electrocatalysts with controlled sulfur-vacancies via electric-field-assisted pulsed laser ablation (EF-PLA) in liquid and in-situ deposition on nickel foam, enabling efficient water splitting. Electric-field parameters efficiently control S-vacancy active sites in electrocatalysts. Higher electric fields yield a MoSx/NiF electrocatalyst with a larger density of S-vacancy sites, suited for HER due to lower Gibbs free energy for H∗ adsorption, while lower electric fields produce an electrocatalyst with lower S-vacancy sites, better suited for OER, as shown by both experimental and theoretical results. The present work opens a horizon in designing high-efficiency catalysts, for a wide range of chemical reactions.

Generation of map on natural environmental background absorbed dose rate in India.

A systematic mapping of natural absorbed dose rate was carried out to assess the existing exposure situation in India. The mammoth nationwide survey covered the entire terrestrial region of the country comprising of 45127 sampling grids (grid size 36 km2) with more than 100,000 data points. The data was processed using Geographic Information System. This study is based on established national and international approaches to provide linkage with conventional geochemical mapping of soil. Majority (93%) of the absorbed dose rate data was collected using handheld radiation survey meters and remaining were measured using environmental Thermo Luminescent Dosimeters. The mean absorbed dose rate of the entire country including several mineralized regions, was found to be 96 ± 21 nGy/h. The median, Geometric Mean and Geometric Standard Deviation values of absorbed dose rate were 94, 94 and 1.2 nGy/h, respectively. Among the High Background Radiation Areas of the country, absorbed dose rate varied from 700 to 9562 nGy/h in Karunagappally area of Kollam district, Kerala. The absorbed dose rate in the present nationwide study is comparable with the global database.

Thin-film dynamics unveils interplay between light momentum and fluid mechanics.

We quantitatively measure the nanomechanical dynamics of a water surface excited by the radiation pressure of a Gaussian/annular laser beam of incidence near total internal reflection (TIR). Notably, the radiation pressure near TIR allowed us to induce a pushing force (Abraham's momentum of light) for a wide annular Gaussian beam excitation of the thin-film regime of water, which, to the best of our knowledge, has never been observed with nanometric precision previously. Our finding suggests that the observation of either/both Abraham's and Minkowski's theories can be witnessed by the interplay between optics and fluid mechanics. Furthermore, we demonstrate the first, to the best of our knowledge, simultaneous measurement of Abraham's and Minkowski's momenta emerging in a single setup with a single laser shot. Our experimental results are strongly backed by numerical simulations performed with realistic experimental parameters and offer a broad range of light applications in optofluidics and light-actuated micromechanics.

A versatile interferometric technique for probing the thermophysical properties of complex fluids.

Laser-induced thermocapillary deformation of liquid surfaces has emerged as a promising tool to precisely characterize the thermophysical properties of pure fluids. However, challenges arise for nanofluid (NF) and soft bio-fluid systems where the direct interaction of the laser generates an intriguing interplay between heating, momentum, and scattering forces which can even damage soft biofluids. Here, we report a versatile, pump-probe-based, rapid, and non-contact interferometric technique that resolves interface dynamics of complex fluids with the precision of ~1 nm in thick-film and 150 pm in thin-film regimes below the thermal limit without the use of lock-in or modulated beams. We characterize the thermophysical properties of complex NF in three exclusively different types of configurations. First, when the NF is heated from the bottom through an opaque substrate, we demonstrate that our methodology permits the measurement of thermophysical properties (viscosity, surface tension, and diffusivity) of complex NF and biofluids. Second, in a top illumination configuration, we show a precise characterization of NF by quantitively isolating the competing forces, taking advantage of the different time scales of these forces. Third, we show the measurement of NF confined in a metal cavity, in which the transient thermoelastic deformation of the metal surface provides the properties of the NF as well as thermo-mechanical properties of the metal. Our results reveal how the dissipative nature of the heatwave allows us to investigate thick-film dynamics in the thin-film regime, thereby suggesting a general approach for precision measurements of complex NFs, biofluids, and optofluidic devices.

Phase change material based hot electron photodetection.

We introduce a phase change material (PCM) based metal-dielectric-metal (MDM) cavity of gold (Au)-antimony trisulfide (Sb2S3)-Au as a hot electron photodetector (HEPD). Sb2S3 shows significant contrast in the bandgap (Eg) upon phase transition from the crystalline (Cry) (Eg = 2.01 eV) to the amorphous (Amp) (Eg = 1.72 eV) phase and forms the lowest Schottky barrier with Au in its Amp phase compared to conventional semiconductors such as Si, MoS2, and TiO2. The proposed HEPD is tunable for absorption and responsivity in the spectral range of 720 nm < λ < 1250 nm for the Cry phase and 604 nm < λ < 3542 nm for the Amp phase. The single resonance cavity and thus the sensitivity of the designed HEPD device can be changed to the double resonance cavity via the Cry to Amp phase transition. The maximum predicted responsivities for the single and double cavities are 20 and 24 mA W-1, respectively, at 950 nm and 1050 nm wavelengths which is the highest among all previously proposed planar HEPD devices. An anti-symmetric resonance mode at a higher wavelength is observed in the double cavity with 100% absorption. Owing to a high index of Sb2S3, an ultrathin ∼40 nm (∼λ/15) MDM cavity supports a critical light coupling to achieve high-efficiency HEPDs. Furthermore, a reversible and ultrafast (∼70 ns) Cry to Amp phase transition of Sb2S3 makes it suitable for many tunable photonics applications ranging from the visible to near-infrared region. Finally, we have introduced a novel scheme to switch between the single and double cavity by exploiting a semiconductor to metal phase transition in a PCM called VO2. The integration of VO2 as a coupling medium in the double cavity has increased the responsivity up to 50% upon phase transition to the metal phase. The proposed design can be used in optical filters, optical switches, ultrathin broad or narrow band solar absorbers, and other energy applications such as water splitting.

Phase change material-based nano-cavity as an efficient optical modulator.

Structural phase transition induced by temperature or voltage in phase change materials has been used for many tunable photonic applications. Exploiting reversible and sub-ns fast switching in antimony trisulfide (Sb2S3) from amorphous (Amp) to crystalline (Cry), we introduced a reflection modulator based on metal-dielectric-metal structure. The proposed design exhibits tunable, perfect, and multi-band absorption from visible to the near-infrared region. The reflection response of the system shows >99% absorption of light at normal incidence. The maximum achievable modulation efficiency with a narrow line width is ∼98%. Interestingly, the designed cavity supports critical resonance in an ultrathin (∼λ/15) Sb2S3 film with perfect, broadband, and tunable absorption. Finally, we proposed a novel hybrid cavity design formed of Cry and Amp Sb2S3 thin films side-by-side to realize an optical modulator via relative motion between the incident light beam and cavity. The proposed lithographic free structure can be also used for filtering, optical switching, ultrathin photo-detection, solar energy harvesting, and other energy applications.

Contactless thin-film rheology unveiled by laser-induced nanoscale interface dynamics.

One of the classical limitations for the investigation of the local rheology of small scale soft objects and/or confined fluids is related to the difficulty to control mechanical contact and its consequences. In order to overcome these issues, we implement a new local, active, fast and contactless optical strategy, called optorheology, which is based on both the optical radiation pressure of a laser wave to dynamically deform a fluid interface and interferometry to probe this deformation with nanometric resolution. This optical approach is first validated by measuring the surface tension and the viscosity of transparent Newtonian liquids. We also show how non-equilibrium situations, such as continuous evaporation, can be used to deduce the thickness dependence of the rheology of thin films and the concentration dependence of the viscosity of binary liquid mixtures and suspensions. We further extend the investigation to elasticity and viscoelasticity measurements of polymer solutions. Finally, since liquids may absorb light, we discuss the influence of a weak laser heating and the triggering of interface deformations by thermocapillary tangential stresses that could represent a complementary approach to probe the rheology at small scale.

Compact picometer-scale interferometer using twisted light.

We propose a simple compact interferometer using twisted light to detect picometer displacement on a solid or liquid surface. The heart of the interferometer lies in producing a daisy petal pattern formed by interference between two oppositely charged twisted beams. The sample being probed is an active component of the interferometer. By analyzing the rotation of the petal pattern, caused by the relative displacement between the cylindrical lens (CL) and solid/liquid surface, we exhibit picometer resolution in displacement measurements. Remarkably, we explore the significance of a radial quantum number in the measurement of surface displacement and surface tilt angle. We also investigate the arbitrary surface deformation profile with similar precision by modifying the set-up. We perform simulations in realistic experimental settings and show that they are in excellent agreement with the predictions of analytic expressions. The proposed set-up can be further miniaturized by a small focal length CL and will open routes for tremendous applications in picometer-scale displacement measurement of a solid or liquid interface by various excitations.

Nanomechanical effects of light unveil photons momentum in medium.

Precision measurement on momentum transfer between light and fluid interface has many implications including resolving the intriguing nature of photons momentum in a medium. For example, the existence of Abraham pressure of light under specific experimental configuration and the predictions of Chau-Amperian formalism of optical momentum for TE and TM polarizations remain untested. Here, we quantitatively and cleanly measure nanomehanical dynamics of water surface excited by radiation pressure of a laser beam. We systematically scanned wide range of experimental parameters including long exposure times, angle of incidence, spot size and laser polarization, and used two independent pump-probe techniques to validate a nano- bump on the water surface under all the tested conditions, in quantitative agreement with the Minkowski's momentum of light. With careful experiments, we demonstrate advantages and limitations of nanometer resolved optical probing techniques and narrow down actual manifestation of optical momentum in a medium.

Universal Long-Range Nanometric Bending of Water by Light.

Resolving mechanical effects of light on fluids has fundamental importance with wide applications. Most experiments to date on optofluidic interface deformation exploited radiation forces exerted by normally incident lasers. However, the intriguing effects of photon momentum for any configuration, including the unique total internal reflection regime, where an evanescent wave leaks above the interface, remain largely unexplored. A major difficulty in resolving nanomechanical effects has been the lack of a sensitive detection technique. Here, we devise a simple setup whereby a probe laser produces high-contrast Newton-ring-like fringes from a sessile water drop. The mechanical action of the photon momentum of a pump beam modulates the fringes, thus allowing us to perform a direct noninvasive measurement of a nanometric bulge with sub-5-nm precision. Remarkably, a <10 nm difference in the height of the bulge due to different laser polarizations and nonlinear enhancement in the bulge near total internal reflection is isolated. In addition, the nanometric bulge is shown to extend far longer, 100 times beyond the pump spot. Our high precision data validate the century-old Minkowski theory for a general angle and offer potential for novel optofluidic devices and noncontact nanomanipulation strategies.