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REEs play a pivotal role in the manufacturing of numerous industrial, defense, consumer, and aviation-related gadgets. As many primary sources of REEs are either exhausted or depleted, coal can be a good secondary source of REEs in the near future. The traditional thermochemical processes to extract REEs are expensive and detrimental to the environment, and thus exploration of more environment friendly and sustainable recovery methods are of the utmost necessity at the present time. In this study, we present in-depth investigation of REEs extraction from the coal samples from the Sohagpur coalfield, Madhya Pradesh. We conducted multiple experiments mainly focusing on rotational movement with the help of a laboratory shaker, magnetic stirrer with hot plate, and a flocculator jar test apparatus in the presence of acidic solutions. Our study highlights that the flocculator jar test apparatus exhibits the maximum recovery of REEs (Ce- 95%, Nd- 83%, La- 82%, Eu- 82%, Pr- 76%, Sm- 74%, Gd- 69%, and Tb- 69%) from coal in the presence of 2 M HNO3. This technique of REEs recovery from coal is easy to use, effective, has little environmental impact, and can be applied on an industrial scale with only minor adjustments to the machinery. [ABSTRACT FROM AUTHOR]

Background: The majority of the visually impaired population lives in rural areas, where, at times, it is difficult to obtain consistent visual acuity (VA) chart luminance levels. Electronic devices, being self-luminous, would help overcome this barrier. The current study identified and validated a smartphone-based Snellen VA chart against the standard ETDRS chart for screening and clinical practice. Methods: The study was conducted in four phases. Phase I: VA chart apps on the Google Play store were explored, screened, reviewed, and calibrated based on the displayed optotype size. Phase II: photometric analysis of room illuminance and VA chart luminance levels was performed. Phase III: the selected smartphone-based Snellen VA chart app was validated against the standard ETDRS chart. Phase IV: repeatability of both the uncorrected and best-corrected VA was checked with the ETDRS chart and the smartphone-based Snellen VA chart app. Results: Phase I: The Snellen Chart app was found to display the Snellen optotype size accurately (inaccuracy <0.25mm). Phase II: average illuminance of the room was ~420 lux. The luminance level of the retro-illuminated ETDRS chart and the Android smartphone screen was ~180 cd/m2 and ~200 cd/ m2, respectively. Phase III: there were no statistically significant differences between the ETDRS chart and the Snellen Chart app for uncorrected (median difference: -0.02 logMAR, p=0.39) and best-corrected (median difference: 0.00 logMAR, p=0.94) VAs in all participants (n=200; p<0.05). The Snellen Chart app showed good agreement with the ETDRS chart for both uncorrected (limits of agreement: -0.16 to 0.22 logMAR) and bestcorrected (limits of agreement: -0.01 to 0.01 logMAR) VAs in all participants. Phase IV: Both the ETDRS chart and the Snellen Chart app were found to have good test-retest repeatability in participants with emmetropia (n=63) and myopia (n=34) with an overall coefficient of repeatability ranging between 0.03 and 0.05 logMAR (p≤0.10). Conclusions: VAs measured with the smartphonebased Snellen Chart app are reliable and in good agreement with the ETDRS chart. Thus, both VA assessment methods can be used interchangeably. [ABSTRACT FROM AUTHOR]

The photovoltaic module testing apparatus being used presently for photovoltaic measurements acts principally on the method of photovoltaic module loading with resistive, capacitive, and electronic elements. In this work, a new method is described using a supercapacitor as the load to the photovoltaic module. This technique of characterization has proved to generate reliable V–I characteristics as validated by statistical and mathematical analyses in this article. Heat dissipation affecting the functioning of the photovoltaic modules is a common occurrence with resistive and capacitive loading techniques. It is reduced significantly in this method using supercapacitors, and curve tracing time is extremely modest and easily controllable. In effect, a low-cost, portable, and reliable I–V plotter is developed, which is operational from an embedded systems platform integrated with smart sensors. This I–V tracer has been used for the performance assessment of solar modules ranging from 10 to 100 Wp under varying climatic conditions in the eastern region of India. This test kit so developed in the photovoltaic engineering laboratory at Indian Institute of Engineering Science and Technology, Shibpur, is estimated to be useful for practicing engineers and photovoltaic scientists and in particular for photovoltaic module manufacturers. The performance parameters such as fill factor and performance ratio of photovoltaic modules measured by the device have been found to have almost identical values as the measurements from a reference commercial testing apparatus. The data pertaining to peak wattage as measured by the designed plotter have been found to be closely converging with an industry-friendly YOKOGAWA Power Meter (WT 330). Such peak values of power as measured and claimed by the datasheets will help reduce the uncertainties in measurement, leading to increased confidence of photovoltaic module manufacturers and investors. With this backdrop, the necessary work for scaling up of the low-cost I–V plotter has been taken up for assessing the performance of higher wattage photovoltaic modules. [ABSTRACT FROM AUTHOR]

Purpose: To determine repeatability and agreement of the ARK-30 handheld autorefractor with retinoscopy under cycloplegic and noncycloplegic conditions in children.Methods: Three consecutive autorefractor measurements (with and without cycloplegia) and retinoscopy were performed and compared in 30 randomized eyes of 30 children (mean age of 6.7 ± 2.7 years with spherical equivalent [SE] refraction from ‒4.01 to +7.38 D) in a cross-section and masked study. Bland-Altman analysis of autorefractor measurements (with and without cycloplegia) and agreement with retinoscopy were calculated with conventional notation (sphere [Sph] and cylinder [Cyl]) and vector notation (SE, J0, and J45coefficients).Results: ARK-30 measurements without cycloplegia were lower than under cycloplegic conditions (Sph: ‒0.52 ± 2.37 D vs + 0.86 ± 2.60 D, P < 0.01; Cyl: ‒0.83 ± 0.80 D versus ‒0.78 ± 0.77 D, P = 0.37; and SE: ‒0.94 ± 2.19 D vs + 0.47 ± 2.44 D, P < 0.01, respectively) and statistically different (P < 0.03) from retinoscopy (Shp: +0.83 ± 2.66 D; Cyl: ‒0.71 ± 0.87 D; SE: +0.51 ± 2.49 D). Without statistical differences were in J0and J45coefficients. Cyloplegic autorefraction measures were not found to be statistically significantly different to retinoscopy measures. ARK-30 under cycloplegia shows better repeatability with lower limits of agreement (LoA) in Sph (LoA: ‒0.66 to +0.69 D), and SE (LoA: ‒0.66 to +0.65 D) than without cycloplegia (LoA: ‒1.45 to +1.77 D, and ‒1.38 to +1.74 D, respectively).Conclusion: Under noncycloplegic conditions, ARK-30 autorefractor has low repeatability and a tendency toward minus over correction in children. However, repeatability and agreement with retinoscopy under cycloplegic conditions allow use of ARK-30 in children to estimate refraction but not to substitute gold standard retinoscopic refraction. [ABSTRACT FROM AUTHOR]

In this study two relatively new arsenic field kits, namely Wagtech Digital Arsenator (WFTK) and Chem-In Corp field test kit (CFTK) for arsenic were evaluated. The response of the two field test kits to known standards (Both As(III) and As(V)) is detailed. In addition around 157 arsenic-contaminated field samples obtained from various locations of Ballia and Kanpur districts, U.P., India were tested using the two kits and the results were compared with the laboratory-based colorimetric method (silver diethyldithiocarbamate method, SDDC). The concentration of arsenic in the 157 samples ranged from 0 to 468 µg l−1. WFTK is seen to be suitable for measuring arsenic concentration <5–100 µg l−1 using the digital meter. CFTK was not able to detect As(V) and its usage is cautioned in Uttar Pradesh where As(V) is seen to occur in appreciable concentrations. The Pearson''s correlation between the silver diethyldithiocarbamate method and WFTK was found to be 0.87 and for the corresponding correlation with CFTK was 0.41 in the concentration range used in this study. Spearman''s rank correlation coefficients comparing the WFTK and CFTK to laboratory measurements in the concentration range of 0–100 µg l−1 were 0.95 (p <0.001) and 0.64 (p <0.001) respectively. [Copyright &y& Elsevier]