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Smart concrete is capable of self-assessing its state of stress and strain. It is produced by tailoring the electrical conductivity of concrete with the addition of conductive materials such as carbon fiber. This paper aims at determining the electrical conductivity of smart concrete materials with randomly dispersed carbon fibers. It unravels the conduction mechanism and establishes a theoretical basis of the percolation threshold for conduction. A numerical model for concrete with carbon fiber is developed. The electrical conduction through the concrete is calculated by solving the governing equations based on Kirchhoff's reformulation of Ohm's Law. More than ten thousand cases with varying fiber topologies, fiber fraction ratios and aspect ratios have been generated to account for the randomness of distribution and their electrical properties are evaluated. By analyzing those results, the mechanism behind the percolation threshold is explained. Finally, an algebraic relationship is posited to determine the percolation threshold has been evaluated. The relationship has been validated with experimental results. The results are extremely valuable for the design of self-sensing smart concrete. [ABSTRACT FROM AUTHOR]

Although geogenic Arsenic (As) contamination is well-recognized in northern Chile, it is not restricted to this part of the country, as the geological conditions favoring As release to the human environment exist across the country as well, although not at the same level, based on comparatively fewer studies in central and southern Chile. The present work provides a critical evaluation of As sources, pathways, and controls with reports and case studies from across the country based on an exhaustive bibliographic review of its reported geogenic sources and processes that affect its occurrence, systematization, and critical revision of this information. Arc magmatism and associated geothermal activities, identified as the primary As sources, are present across the Chilean Andes, except for the Pampean Flat Slab and Patagonian Volcanic Gap. Metal sulfide ore zones, extending from the country's far north to the south-central part, are the second most important geogenic As source. While natural leaching of As-rich mineral deposits contaminates the water in contact, associated mining, and metallurgical activities result in additional As release into the human environment through mining waste and tailings. Moreover, crustal thickness has been suggested as a principal controlling factor for As release, whose southward decrease has been correlated with lower As values. [ABSTRACT FROM AUTHOR]

The Ganges River delta complex contains a transboundary aquifer system shared between India and Bangladesh. Although it serves as the main freshwater source for the population inhabiting the delta, the aquifer system is severely contaminated with arsenic (As). This study aimed to determine the control of the delta hydrostratigraphy on the regional-scale depth distribution of As within the aquifer system. We developed the first high-resolution, regional-scale, transboundary hydrostratigraphic model of the Ganges River delta and analyzed the patterns of As distribution as a function of the hydrostratigraphy. Model results indicate that, despite the presence of a single aquifer system across the delta, the hydrostratigraphy is spatially variable and can be architecturally divided into three distinct aquifer subsystems from northwest to southeast: a single, thick continuous aquifer (type I); a vertically segregated, semiconfined aquifer subsystem (type II); and a multilayered, nearly confined aquifer subsystem (type III). Results indicate that the spatial distribution of As is characteristically different in each subsystem. In the type I aquifer, As concentrations tend to be homogeneous at all depths, while in type II and type III aquifers, As concentrations sharply decrease with depth. The intervening aquitards in the type II and type III aquifer subsystems appear to act as natural barriers to infiltration of surficial As or organic matter-rich water to the deeper aquifer zones. This delineation of the regional-scale hydrostratigraphic architecture and resulting understanding of its plausible controls on the depth-distribution of As within the delta should significantly aid in the systematic framing of sustainable management plans for the As-safe aquifers within the Ganges River delta aquifer system. [ABSTRACT FROM AUTHOR]

Introduction: During the refining and packing of tea, a very fine dust is formed which is called the tea fluff. Exposure to this fluff has been reported to cause ventilatory defects on chronic exposure. Objective: To determine the association between air quality of the different work sections of tea gardens and the ventilatory functions of the workers. Methodology: An observational analytical study with cross sectional design was conducted on 400 apparently healthy individuals working in different sections of 4 tea gardens. Data on sociodemographic characters of the population, particulate matter (PM) and air quality (AQI) was recorded. All participants underwent spirometric evaluation. Results: The mean (SD) age of the study population was 37.8 (8) years. Most (67%) of the study participants were females. The participants were engaged in the job for a mean (SD) of 4.7 (2.7) years. The median distribution of PM2.5, PM 10 and AQI are progressively higher from the garden section to the dry section. A significant correlation between FVC and PM2.5 and PM10 is seen. FEV1 and FEV1/FVC shows a significant correlation with all air quality parameters while FEF25-75 is correlated to none of them. Comparison of the three models to predict the spirometric variables show that even after adjustments, the FEV1 is significantly associated with air quality parameters, FEV1/FVC is significantly associated with the air quality parameters and age while the FEF25-75% is dependent on the age of the participant. Conclusion: There is a strong correlation between the ventilatory parameters and the cumulative exposure of PM2.5, PM10 and AQI, which persists even after adjustment for confounders. [ABSTRACT FROM AUTHOR]

Background: Properly constructed single best-answer multiple choice questions (MCQs) or items assess higher-order cognitive processing of Bloom's taxonomy and accurately discriminate between high and low achievers. However, guidelines for writing good test items are rarely followed, leading to generation and application of faulty MCQs. Materials and Methods: During lockdown period in 2020, internal assessment was taken through online mode using Google Forms. There were 60 'single response type' MCQs, each consisting of single stem and four options including one correct answer and three distractors. Each item was analyzed for difficulty index (Dif I), discrimination index (DI), and distractor efficiency (DE). Results: The mean of achieved marks was 42.92± (standard deviation [SD], 5.07). Dif I, DI, and DE were 47.95± (SD 16.39) in percentage, 0.12± (SD 0.10), and 18.42± (SD 15.35), respectively. 46.67% of the items were easy and 21.66% were of acceptable discrimination. Very weak negative correlation was found between Dif I and DI. Out of total 180 distractors, 51.66% were nonfunctional one. Conclusion: Item analysis and storage of MCQs with their indices provides opportunity for an examiner to select MCQs of appropriate difficulty level as per the need of assessment and decide their placement in the question paper. [ABSTRACT FROM AUTHOR]

Ultrasonic wave–based imaging is a popular nondestructive tool used to inspect RC structures. The inherent heterogeneity of concrete poses a great challenge for imaging incipient damage to concrete. This paper presents an algorithm for improving the quality of images obtained from a considerably reduced data set. A set of RC samples was prepared. The reflections of ultrasonic waves were recorded by placing a transmitter and a receiver on the surface of the concrete. The signals were processed to create an image of a section of the specimens, and the images were enhanced through a set of three-step cascading filters. The spatial apodization (SA) filter is first applied to control the spatial directivity of the ultrasonic transducers. At the second level, a contrast improvement (CI) filter is applied to further reduce ghosting. The third filter is the moving average–based reflection localization filter. Images produced by the algorithm are compared with those produced via conventional techniques in terms of clarity and contrast. It is demonstrated that the cascading filters produce a clearer image with a considerably smaller data set. [ABSTRACT FROM AUTHOR]

In this study, a numerical model of insulin depot formation in the subcutaneous adipose tissue of humans has been developed using the commercial computational fluid dynamics software. A better understanding of the underlying mechanisms can be helpful in the development of novel insulin administration devices and cannula geometries. Developing a model of insulin depot formation can provide faster results compared to extensive experimental studies which are typically done on porcine tissues. The injection method considered in this simulation involves an insulin pump that uses a rapid acting U100 insulin analogue. The depot formation has been studied by simulating Bolus injections ranging from 5 to 15 units of insulin, which corresponds to volumes of 50-150 µL. The insulin is injected into modeled subcutaneous tissues typically present in human abdominal regions. The subcutaneous tissue has been modeled as a fluid-saturated porous media. An anisotropic approach has been used to define the tissue permeability. The value of the porosity in parallel and perpendicular directions has been varied to modify the viscous resistance to the flow in these directions. The developed model has been validated by comparing with published experimental results, which show qualitative similarities in disk-shaped insulin depot formation. The validated model is then used to study formation of insulin depot inside the subcutaneous tissue at varying insulin flow rates involving different cannula geometries and arrays. The numerical model has been found to be an effective option to evaluate new cannula designs prior to the manufacturing and testing of prototypes, which can be rather time consuming and expensive. [ABSTRACT FROM AUTHOR]

The rapid decline of groundwater levels (GWL) due to pervasive groundwater abstraction in the densely populated (~1 billion) Indus-Ganges-Brahmaputra-Meghna (IGBM) transboundary river basins of South Asia, necessitates a robust framework of prediction and understanding. While few localized studies exist, three-dimensional regional-scale characterization of GWL prediction is yet to be implemented. Here, 'support vector machine', a machine-learning-based method, is applied to data from the Gravity Recovery and Climate Experiment (GRACE) and data on land-surface-model-based groundwater storage and meteorological variables, to predict the GWL anomaly (GWLA) in the IGBM. The study has three main objectives, (1) to understand the spatial (observation well locations) and subsurface (shallow vs. deep observation wells) variability in prediction results for in-situ GWLA data for a large number of observation wells (n = 4,791); (2) to determine its relationship with groundwater abstraction, and; (3) to outline the advantages and limitations of using GRACE data for predicting GWLAs. The findings, based on individual observation well results, suggest significant prediction efficiency (median statistics: r > 0.71, NSE > 0.70; p < 0.05) in most of the IGBM; however, the study identifies hotspots, mostly in the agriculture-intensive regions, having relatively poor model performance. Further analysis of the subsurface depth-wise prediction statistics reveals that the significant dominance of pumping in the deeper depths of the aquifer is linked to the relatively poor model performance for the deep observation wells (screen depth > 35 m) compared with the shallow observation wells (screen depth < 35 m), thus, highlighting the limitation of GRACE in representing spatial and depth-dependent local-scale pumping. [ABSTRACT FROM AUTHOR]

In this study, a numerical model of insulin depot formation in the subcutaneous adipose tissue of humans has been developed using the commercial computational fluid dynamics software. A better understanding of the underlying mechanisms can be helpful in the development of novel insulin administration devices and cannula geometries. Developing a model of insulin depot formation can provide faster results compared to extensive experimental studies which are typically done on porcine tissues. The injection method considered in this simulation involves an insulin pump that uses a rapid acting U100 insulin analogue. The depot formation has been studied by simulating Bolus injections ranging from 5 to 15 units of insulin, which corresponds to volumes of 50–150 μL. The insulin is injected into modeled subcutaneous tissues typically present in human abdominal regions. The subcutaneous tissue has been modeled as a fluid-saturated porous media. An anisotropic approach has been used to define the tissue permeability. The value of the porosity in parallel and perpendicular directions has been varied to modify the viscous resistance to the flow in these directions. The developed model has been validated by comparing with published experimental results, which show qualitative similarities in disk-shaped insulin depot formation. The validated model is then used to study formation of insulin depot inside the subcutaneous tissue at varying insulin flow rates involving different cannula geometries and arrays. The numerical model has been found to be an effective option to evaluate new cannula designs prior to the manufacturing and testing of prototypes, which can be rather time consuming and expensive. [ABSTRACT FROM AUTHOR]

An ultrasonic shear wave-based nondestructive method is proposed in this paper to detect steel–concrete interface debonding owing to the top-bar effect. A concrete wall was cast with horizontal reinforcements at different heights in order to create interfacial defects underneath the top bars. Lead zirconate titanate (PZT) patches were surface mounted at the ends of the bars to excite and record shear waves. The ultrasonic results showed that the amplitude of the signals increased with the height of the bars. The specimens were cut open after the experiments and the top-bar effect was clearly discerned. Its increase with the height of the bar was clearly observed. An increasing difference between the high-frequency component (HFC) and the excitation frequency of the signal was observed between the bottom bar with a good bond and the top bars. This feature can be utilized for nondestructively monitoring the top-bar effect. [ABSTRACT FROM AUTHOR]

Nanofluids are stable colloidal suspensions of nanometer sized particles suspended in traditional heat transfer fluids. During boiling of nanofluids, the dispersed nanoparticles change the surface conditions on the heated surface. A layer of nanoparticles is expected to be deposited on the surface during the boiling process which affects the boiling characteristics and the critical heat flux. The deposition of nanoparticles on the surface changes the surface contact angle as well as the bubble growth rates. In this study, nucleate pool boiling experiments have been performed using 10 nm and 30 nm sized alumina nanoparticles dispersed in water at 104 vol% and 10-i vol% concentrations. A deterioration in heat transfer was observed during boiling of nanofluids. As bubbles nucleate from the copper surface, the entire bubble growth cycle has been visualized and recorded using a high-speed camera. For each concentration of nanoffuid, bubble growth period, bubble equivalent, and base diameters, and the bubble contact angle have been measured. This measured data was compared with measurements obtained during pool boiling of base fluid water. The measured bubble parameters are used to evaluate the energy transferred per bubble due to microlayer evaporation. [ABSTRACT FROM AUTHOR]

Bacterial cementation is a relatively new technology for stabilization of granular systems where cementation happens incrementally with repeated injection of the cementation fluid through the pores of the granular media. The mechanical performance of the bacterially cemented systems is critically dependent on the spatial and temporal variations of the precipitated cement. Numerical models proposed hitherto for mechanical behavior of bacterial cementation have assumed simple homogenized cementation. This paper investigates mechanical characteristics of bacterially cemented granular materials with a view to developing reliable numerical models that incorporate the spatial and temporal variations in cementation. The numerical models are validated by controlled experiments. Sand columns have been cemented to various degrees using a bacterial system. The degree of cementation was estimated by scanning electron microscopy. Triaxial compression tests have been conducted by varying the hydrostatic pressure. A multiscale numerical model is developed to simulate the mechanical response of the cemented system. The numerical results show good agreement with the experimental observations. [ABSTRACT FROM AUTHOR]

Groundwater-sourced drinking water quality in South Asia, specifically India, is extremely stressed, mostly from the presence of many pervasive and geogenic pollutants. The presence and behavior of anthropogenic pollutants like polycyclic aromatic hydrocarbons (PAHs) are poorly investigated on a regional or basin-wide scale. The present study provides one of the first documentation of the presence and behavior of PAH in the aquifer sediments in the Ganges river basin. Lower and medium molecular weight PAHs, e.g., naphthalene, phenanthrene, and fluoranthene were detected in 79, 36, and 13% of samples (n = 25). The PAH level in groundwater was approximately five times lower than river water. The sorption behavior of PAHs were studied in experiments in presence/absence of organic carbon and by simulating advective transport of low to medium molecular weight PAHs, e.g., naphthalene, phenanthrene, and fluoranthene in aquifer sediments collected from agricultural, peri-urban, and urban areas. Naphthalene and phenanthrene adsorbed on quartz and kaolinite, but not on clay minerals like kaolinite. Fluoranthene adsorbed more favorably on kaolinite. Numerical modeling of the advective transport of PAHs in aquifers suggest up to 25 times faster movement of pollutants from irrigation-induced pumping, indicating the strong control of hydraulics on the spatial distribution of PAHs in subsurface. [ABSTRACT FROM AUTHOR]

India has been the subject of many recent groundwater studies due to the rapid depletion of groundwater in large parts of the country. However, few if any of these studies have examined groundwater storage conditions in all of India's river basins individually. Herein we assess groundwater storage changes in all 22 of India's major river basins using in situ data from 3420 observation locations for the period 2003–2014. One-month and 12-month standardized precipitation index measures (SPI-1 and SPI-12) indicate fluctuations in the long-term pattern. The Ganges and Brahmaputra basins experienced long-term decreasing trends in precipitation in both 1961–2014 and the study period, 2003–2014. Indeterminate or increasing precipitation trends occurred in other basins. Satellite-based and in situ groundwater storage time series exhibited similar patterns, with increases in most of the basins. However, diminishing groundwater storage (at rates of >0.4 km3/year) was revealed in the Ganges-Brahmaputra River Basin based on in situ observations, which is particularly important due to its agricultural productivity. [ABSTRACT FROM AUTHOR]

In 2020, we are in the doorstep of a new decade, during which the UN Sustainable Development Goals (SDG) are to be achieved, collectively as one nation and one human-hood, where availability of safe, sustainable and clean water and air forms the core of multiple goals. However, the emergence of the COVID-19 pandemic across the globe has resulted a newer challenge and paradigm for an evolving socio-scientific priorities. It is generally expected that the impacts of the pandemic would be in shorter time-scale, while the planned time and pathway for attaining the SDG are typically mandated in longer-term, hence may remain mostly unaffected. However, the stringent lockdown measures, isolated economies and financial burden to contain the pandemic emergency have resulted to slowdown of socio-economic development, which if continues for a longer period, would put a question mark on developing plans and pathways to achieve the SDGs, even in decadal-scale. Hence, in these newer times, it is important to understand the real priorities of availability of clean water and air, which are already stressed worldwide and in India, because of various natural and human-influenced triggers. This ongoing pandemic has provided an unprecedented opportunity to evaluate the impact of human development and consequent feedback of nature and human society in pre- and post-COVID scenarios on water–air–human life, which can help to re-think and re-orient the societal development priorities. It is a rare opportunity for scientists to impress the policy-makers with real-time examples on the efficacies of potential mitigation strategies for climate change, water and air pollution, and the importance of enduring investment on environmental causes and consequent benefits that can secure health and development for our future generations. Highlights: Environmental pollution and climate change pose a high risk for human survival. Develop resilience to attain SDGs in spite of economic constraints caused by COVID-19. Set real priorities of availability of clean water and air for future, in a unified world. [ABSTRACT FROM AUTHOR]

Bacterial cementation can be a pathway to sustainable cementation in soil mounds as it consumes miniscule amount of energy in comparison to engineered cement. Bacteria cement grains through progressive formation of inter-granular bridges. This study presents a numerical framework to model the sparsely cemented granular heaps. A rigorous experimental program has been presented to observe the relationship between the level of cementation and the shapes of heap. A discrete element model (DEM) for sparsely cemented grains has been developed. The extent of cementation is modelled through random clumping of grains. It is observed that DEM is capable to capture the effect of cementation through grain clumping. A parametric study of the grain size distribution, internal friction angle, shape of clumps and the extent of cementation has been performed. The results show that friction angle, grain size distribution and grain clumping have considerable effect on the shape of heap. A cubic polynomial is able to capture the shape of heap reasonably well. The results will be useful for predicting the profile of sparsely cemented granular heaps. Image 1 • The shape of a heap formed by granular materials is investigated experimentally and theoretically. • A biocementation technique is used for partially cementing the grains. • Effect of partial cementation is captured numerically through clumping of the grains. • The present Discrete element Model is capable of capturing the shapes of the heaps. • A polynomial curve is prescribed for the definition of the shape. [ABSTRACT FROM AUTHOR]

High groundwater arsenic (As) across the globe has been one of the most well researched environmental concerns during the last two decades. Consequently, a large scientific knowledge-base has been developed on As distributions from local to global scales. However, differences in bulk sediment As concentrations cannot account for the As concentration variability in groundwater. Instead, in general, only aquifers in sedimentary basins adjacent to mountain chains (orogenic foreland basins) along continental convergent tectonic margins are found to be As-enriched. We illustrate this association by integrating observations from long-term studies of two of the largest orogenic systems (i.e., As sources) and the aquifers in their associated foreland basins (As sinks), which are located in opposite hemispheres and experience distinct differences in climate and land-use patterns. The Andean orogenic system of South America (AB), an active continental margin, is in principle a modern analogue of the Himalayan orogenic system associated with the Indus-Ganges-Brahmaputra river systems in South Asia (HB). In general, the differences in hydrogeochemistry between AB and HB groundwaters are conspicuous. Major-solute composition of the arid, oxic AB groundwater exhibits a mixed-ion hydrochemical facies dominated by Na-Ca-Cl-SO 4 -HCO 3. Molar calculations and thermodynamic modeling show that although groundwater of AB is influenced by cation exchange, its hydrochemical evolution is predominated by feldspar dissolution and relationships with secondary clays. In contrast, humid, strongly reducing groundwater of HB is dominated by Ca-HCO 3 facies, suggestive of calcite dissolution, along with some weathering of silicates (monosiallitization). This work demonstrates that although hydrogeochemical evolutionary trends may vary with local climate and lithology, the fundamental similarities in global tectonic settings can still lead to the elevated concentrations of groundwater As. Unlabelled Image • Compare and contrast the hydrogeologic framework of arsenic-enriched aquifers of Latin America and South Asia • Establish link between tectonics and groundwater arsenic pollution • Show the effects of local scale forcing on mobilization of arc volcanics derived primary As in similar tectonic setting [ABSTRACT FROM AUTHOR]

More than 100 million people around the world are endangered by geogenic arsenic (As) in groundwater, residing in sedimentary aquifers. However, not all sedimentary aquifers are groundwater As enriched, and the ultimate source of As in enriched aquifer sediments is yet-unknown, globally. A reconnaissance of the major aquifers suggests that major As enriched aquifers are predictably systematic on a global scale, existing in sedimentary foreland basins in the vicinity of modern or ancient orogenic systems. In conformity with the Principle of Uniformitarianism, we demonstrate that the groundwater As comes from magmatic arcs (primary source) in present (e.g. Andes) or ancient (e.g. Himalaya) continental convergent margins of some of the most prominent orogenic systems across the globe, and ends up in sediments (secondary source) in adjoining foreland or related basins that eventually act as aquifers. These arc magmas scavenge As while rising through the deep continental crust. Erosion of such orogens ultimately increases the bulk As content in sediments of adjoining basins, leading to groundwater As enrichment in downstream aquifers. Such As-polluted aquifers are eventually extensively used for groundwater exploitation, for drinking and other human purposes. Surface geological and biogeochemical processes, like redox reactions, are conducive to such groundwater As enrichment. We suggest this model by integrating our study of long-time observations in Himalayan and Andean basin aquifers, and generalizing 63 major aquifers across the globe, to demonstrate the source-to-sink transport of As, thereby delineating it's geogenic cycling in the subsurface. This work outlines the specifics of the mechanisms that would drive the processes of groundwater As enrichment across spatio-temporal scales, i.e. tectonic-scale taking place over millions of years on continental-scale and groundwater pollution taking place at human time-scales on village to household scale. Thus, in this work, we demonstrate a direct evidence of connectivity between global geological processes and individual human health. Unlabelled Image • Establish link between tectonics and groundwater arsenic pollution • Demonstrate the model of geogenic As cycle with examples across the world • Evaluate the geologic framework of major arsenic-enriched aquifers • Propose link between global geological processes with human health [ABSTRACT FROM AUTHOR]

The influence of aquifer sediments provenance and geochemical processes on groundwater solute chemistry, including the fate of groundwater arsenic (As) in aquifers for three distinct tectono-morphic zones (north-western, northern, and southern [NW, N, and S] in the basin of Himalayan Mega Rivers, i.e., Brahmaputra river basin (BRB), and adjoining the Himalayas and Indo-Burmese ranges, have been delineated. The presence of fluvial re-worked quartz, feldspar, and mica along with orogeny-sourced ferromagnesian minerals contained aquifers sediments in the NW and N regions are hypothesized to be derived from the Himalayan system. The S-aquifers mineralogy differs from northern aquifers by a higher proportion of Fe/Mg aluminosilicates, phyllosilicates/clay minerals, derived from the Indo-Burmese ranges. The dissolved As distribution is highly variable among the different alluvial aquifers. The S-region is highly enriched in groundwater As (bdl to 5.53 μM or 415 μg/L, mean 1.77 μM) compared to NW and N regions (bdl to 1.8 μM or 134 μg/L, mean 0.28 μM [60% As-contaminated samples]; bdl to 2.45 μM or 184 μg/L, mean 0.68 μM [65% As-contaminated samples] respectively). More than 92% of groundwater samples in the S-region are enriched with As (>50 μg/L), which draws a distinct difference from the NW and N regions of BRB aquifers. Reaction-path models suggest intense chemical weathering of S-aquifer matrix due to the higher equilibrium (more stable) of secondary mineral phases with the solution (groundwater), as compared to NW and N regions. The present study proposes a model for the geological control and effect of weathering/water–sediment reaction on As-fate and mobilization mechanism in the groundwater system of the barely studied Brahmaputra river basin aquifers. Image 1 • Water-sediment interaction dominates groundwater evolution. • A model of arsenic (As) influx and mobilization in study area is proposed. • Geology is hypothesized to be a major influencing factor for hydrogeochemistry • Tectonics influence the sediment provenance for groundwater arsenic content. [ABSTRACT FROM AUTHOR]

• Hydraulic connectivity and response between shallow and deeper groundwater. • Delineation of impact of surface-and groundwater interactions on stable isotopic and solute signature. • Multi-depth, temporal stable isotope and piezometric response to coastal hydrological dynamics. • Vulnerability of multi-depth of potable groundwater to salinization. With increasing population and urbanization in the deltas across global mega-river basins, groundwater stress is increasing due to changing ocean-land disposition, hydroclimatic extremes, over-exploitation and natural/anthropogenic contamination. Such change in coastal hydrodynamic process makes an impact in to the resilience of groundwater-sourced drinking water vulnerability. The groundwater responses studied in this work in the ecologically-vulnerable, UNESCO World Heritage site of the Sundarbans delta-front aquifers at the river Ganges-Brahmaputra mega delta, demonstrate a unique example of such intricacies and complexities. High-resolution, temporal, depth-dependent hydraulic connectivity and hydrochemistry was studied for this complex, climate-driven, tidal-induced hydrological interactions between surface water (seawater of Bay of Bengal [BoB] and Ganges river water) with shallow and deep groundwater by stable isotopic (δ18O and δD) signatures and piezometry. A wide range of salinity content and δ18O composition of groundwater samples for 14–25 (salinity: 3–45 ppT, δ18O: −3.63 to −1.15‰) and 30–50 meter below ground level (mbgl) (salinity: 5–25 ppT, δ18O: −3.41 to −1.34‰) was recorded, while, comparatively, a narrow range of temporal variability was observed for the depths of 115 (salinity: 1–4 ppT, δ18O: −5.04 to −2.15‰) and 333mbgl (salinity: 1 to 3 ppT, δ18O: −4.43 to −2.81‰). Study results revealed that vertical transport of solute has been induced by coastal hydrodynamics. However, human interferences, in terms of groundwater abstraction and land use-land cover change (e.g. brackish aquaculture) do have substantial impact on evolving groundwater response, thereby impacting resilience to drinking water option in this densely populated area. Fluctuations of groundwater level in relation with δ18O gw composition showed shallow depths (14–50 mbgl) are hydraulically connected by local flow and conducive of chemical exchanges. The deeper groundwater (115–330 mbgl depths) flow suggests regional-scale hydraulic connections along flow paths. In-spite of sub-meter scale seasonal groundwater level changes, salinity variability is observed between 1 and 4 ppT at >100 mbgl depths, suggest mixing between chemically-distinct water reservoirs, conserving hydraulic mass-balance. However, such observation suggests severe implications for groundwater vulnerability, which might aggravate with future intensification of irrigational abstraction, as well as with changing hydroclimatological regime and extreme events. Thus, future planning and management strategies of sustainable supply of safe water in such ecologically-sensitive groundwater systems need to incorporate such dynamic chemical evolution. [ABSTRACT FROM AUTHOR]

Top-bar defects in reinforced concrete are voids that are observed below the reinforcing bars that are at an elevation of more than 300 mm. The authors have demonstrated a new ultrasonic guided wave technique to non-destructively detect top-bar defect (Wang, Mukherjee et al., 2021). It has been reported that bars with top-bar defect corrode is faster than other bars. The corrosion also manifests in a different manner in these bars. This paper proposes a guided ultrasonic wave-based non-destructive method for monitoring corrosion in reinforced concrete with top-bar defect. Concrete wall samples with bars of various extents of top-bar defect were subjected to accelerated corrosion. Simultaneously, the bars have been monitored with guided ultrasonics. The investigation revealed that top-bar defect has a significant influence on the corrosion process. The destructive tests performed at the end of corrosion exposure revealed that the top-bar specimens had a significant loss of strength than the bars with a good bond. The proposed non-destructive has been calibrated to assess the residual capacities of corroded bars in presence of top-bar defect. [ABSTRACT FROM AUTHOR]

Abstract Fibre Reinforced Polymers are widely used for retrofitting and strengthening of structures. The integrity of fibre matrix system in FRP system would be severely compromised in situations where the system is exposed to elevated temperatures. In this paper, an Alkali Activated Siliceous Paste (AASP) has been developed as a temperature tolerant adhesive for FRP systems. AASP has been compared with the conventional fibre-epoxy system and the fibre-epoxy system. It has also been tested as a thermal insulation overlay on the epoxy. The test has been performed by applying three-point flexure. Simultaneously, Acoustic Emission events have been recorded to understand the failure characteristics in each case. To understand the microstructural effect scanning electron micrographs and energy dispersive X-ray analysis have been performed. The conventional epoxy system suffered a loss in integrity after the glass transition temperature of epoxy. AASP specimens offered considerably improved thermal performance but the bonding with concrete was variable due to inadequate penetration into the fibre sheet. AASP overlays prevented visual degradation of the epoxy from elevated temperature but couldn't help prevent the development of heat gradient. AASP has a great potential to be developed as a temperature tolerant adhesive but its rheology must be improved for ensuring reliable bonding between the fibres and concrete. [ABSTRACT FROM AUTHOR]

Highlights • Estimation of total usable groundwater storage (UGWS) in India. • Groundwater storage depletion/replenishment fraction against total availability. • Temporal downscaling of groundwater availability using satellite-based measurements. • Estimates of groundwater availability and change across Indian states. • Agricultural water use intensified in rapid groundwater depleting regions. Abstract Groundwater use in India has been in the limelight in recent years due to its intensive and apparent unsustainable use that poses threats to water security, drinking water supply and food production. Here, we present estimates of usable groundwater storage, for the first time, at the state-level across all of India using both in situ and satellite-based measurements. Groundwater-level data are used from 3907 in situ monitoring wells across India and the total usable groundwater storage (UGWS) is estimated between 2005 and 2013. The UGWS estimates indicates high rates of depletion (>5 km3/yr) of groundwater storage (GWS) in north-east India (i.e. Assam), even though increase in precipitation has been observed in that state. Satellite-based (Gravity Recovery and Climate Experiment, GRACE) estimates indicate that the development of recent GWS-depletion zones is concentrated in unconsolidated sediments or lithotype across the Indus, Ganges and Brahmaputra basins, in the states of Punjab, Haryana, Uttar Pradesh, Bihar, and West Bengal. In contrast, southern and central Indian states (such as Andhra Pradesh, Maharashtra, Gujarat, Tamil Nadu, and Chattisgarh), show replenishing GWS trends. We also find that the states with highest groundwater depletion rates are subjected to water-intensive cropping practices during the study period. We temporally downscale the UGWS with support from GRACE satellite-based measurements. We conclude that the approach we developed here can be applied in other parts of the world to devise management options for sustainable groundwater use. [ABSTRACT FROM AUTHOR]

Abstract Design, construction and operation of built environments emit 40% of global anthropogenic greenhouse gases. Search for alternative building materials is imperative for ensuring sustainable habitat for world's increasing population. Rammed earth is one such material with dramatically lower embodied energy and emission than concrete or brick. This paper explores further reduction of operational emission of rammed earth by improving its thermal resistance by recycling industrial by-products such as crumb rubber. The dividend from the introduction of the filler material is examined. The results have been validated with experimental data. Effect of volume fraction, size, shape and spatial distribution of the filler has been presented. It is noted that the recycled fillers considerably improve the thermal insulation. However, they induce increased thermal stress on rammed earth. Thus, a trade-off between strength and thermal resistance needs to be reached. The results would be useful for arriving at an optimal spatial design of the filler to achieve the target thermal resistance and strength. [ABSTRACT FROM AUTHOR]

Introduction: Helminths infestations are common in children in the tea garden areas of Darjeeling, which present unique social, cultural, and environmental conditions. The present study was conducted to determine the proportion of soil-transmitted helminth (STH) infestations and association of STH to sociodemographic variables among children attending Integrated Child Development Services centers of a tea garden area in Darjeeling. Methodology: A cross-sectional descriptive study was conducted at Kiran Chandra Tea Estate, a tea garden in Naxalbari, Darjeeling, between August and September 2016. Stool samples were collected from children attending ICDS centers in the area and examined using the direct and concentration methods. A pretested and predesigned questionnaire was used to collect data on the sociodemographic profile of the children's families. Results: Stool samples could be collected from 52 (45%) of the 115 eligible children. The children were predominantly male (61.5%), from families with an income between Rs. 2000 and 4000 per month, had mothers with no formal education (75.0%) and came from households with no sanitary toilets (33.5). The proportion of children with STHs was 9.6%; with Ascaris found in 7.7% and Trichuris in 1.9%. No statistically significant differences were found in selected variables between the worm-positive and worm-negative children. Conclusions: The proportion of STH infestation is low among children <6 years of age attending ICDS in the study area probably because of the mass de-worming strategy of the government of India. Some differences in infestations among groups might suggest a clustering effect. [ABSTRACT FROM AUTHOR]

Abstract In the progress of small molecule as drug candidates, 4-hydroxycoumarin based compounds bearing a crucial place as potent antibiotic agents with appreciable safety in drug invention. Being synthetically and easily obtainable, 4-hydroxycoumarin related compounds with planar structure have been promoted predominantly as DNA targeting agent. Nevertheless, here we elucidate the synthesis, characterization and theoretical study of bio-active small molecule 4-hydroxy-3,4′-bichromenyl-2,2′-dione (4HBD). Then we have illuminated the binding interactions of 4HBD with calf thymus DNA (ctDNA), which is particularly designed for biological application. Extensive investigations of the binding of 4HBD with ctDNA are provided by utilizing multi-spectroscopic and molecular docking approaches, including UV–vis absorbance, steady-state, time-resolved fluorescence spectroscopy and circular dichroism study. The calculated binding and quenching constant value from quantitative data analysis of absorption and emission spectroscopy shows that 4HBD binds to the ctDNA groove. Further confirmation of the same is found by comparative displacement and iodide quenching studies. Negative enthalpy, negative free energy and positive entropy change imply a hydrophobic force monitors the association of 4HBD with the biomacromolecule. Interestingly the small molecule (4HBD) shows potential anti-bacterial activity against the model pathogenic gram-negative (Escherichia coli and Pseudomonas aeruginosa) and gram-positive (Bacillus subtilis and Staphylococcus aureus) bacteria. The noncytotoxic nature of the 4HBD is demonstrated in vitro with the help of MTT assay by normal kidney epithelial (NKE), breast cancer cells (MCF-7) and human prostate cancer cell (PC3) lines. Hemolytic assay exhibits insignificant hemolysis of human erythrocyte cells at the minimum inhibitory concentration (MIC) of these tested bacteria. In this regard the present invention of 4-hydroxycoumarin based antimicrobial and noncytotoxic 4HBD molecule holds future promise in the development of new antibiotics. Highlights • Successfully synthesized and characterized the bioactive 4-hydroxy-3,4′-bichromenyl-2,2′-dione. • Theoretically calculated equilibrium constant value at the room temperature (~300 K) as well as the reaction temperature (~350 K) is near about same (~2). • Absorption spectra of 4HBD found from the excitation of an electron from HOMO-1 to LUMO and LUMO+1is good agreement with experimentally found result. • The synthesized molecule may be used as antibiotic agent due to non-toxicity and potential antibacterial activity. • The 4HBD molecule binds at the minor groove of ctDNA which was confirmed by biophysical and molecular docking study. [ABSTRACT FROM AUTHOR]

Background: Appropriateness of admissions and inpatient length of stay (LOS) are important factors controlling health-care expenditure. The current study was conducted to assess the proportion of appropriate admissions among 29-day to 12-year--old aged patients admitted to pediatric wards of a tertiary health-care center in one month and evaluate inappropriate LOS among them. Materials and Methods: An observational longitudinal study was carried out for two months among patients admitted to the pediatric inpatient department using Pediatric Appropriateness Evaluation Protocol (PAEP)-II tool. All patients admitted to the institution during the study period were included in the study. Results: Among 495 children, 438 (88.5%) were appropriately admitted. Inappropriate admission was mostly found in children aged 1 to 5 years (29, 16.6%), those who lived >5 km from the hospital (45, 15.2%), and those who presented with other systemic illnesses (13, 31.7%). Among the appropriately admitted children, 333 (76%) met the criteria of appropriate LOS during their hospital stays. Multivariable logistic regression showed that the age of the children (AOR = 0.99; 95% CI = 0.98, 0.99), age-appropriate feeding (AOR = 2.12;95% CI = 1.30,3.47), and hematological disorder (AOR = 0.16; 95% CI = 0.05, 0.52) were found to be associated with the children being kept at the hospital inappropriately. Conclusions: The current study observed a high proportion of appropriate admission in children. However, a higher proportion of inappropriate LOS among them was seen. The younger age group, age-appropriate feeding, and type of illness were found as the primary predictors for inappropriate LOS. [ABSTRACT FROM AUTHOR]

Exploring the binding interaction of drug molecule with calf thymus DNA turn out to be a dynamic field of research at the interface between biological science and medicinal chemistry. Captopril, an angiotensin-converting enzyme inhibitor and extensively used for the treatment of hypertension and cognitive heart failure. Still now, its interaction style with ctDNA is not well interpreted. In this issue, we have tried to find out the binding mode of captopril with ctDNA under physiological pH using fluorescence probe pyrene by spectroscopic methods along with molecular docking study. UV–vis absorption, emission and time-resolved fluorescence spectroscopy suggest the non-covalent binding interaction between captopril and ctDNA with binding constant value 5.47 × 10 3 M −1 . The circular dichroism measurement reveals the conformational change of ctDNA upon addition of captopril. Binding nature of captopril with ctDNA is affirmed from the Isothermal Titration Calorimetry, helix melting experiment, comparative displacement assay, cyclic voltammetry, viscometric study and finally molecular docking. Thermodynamic parameters ∆ H , ∆ S and ∆ G transpired that captopril probably binds to minor groove of ctDNA. The groove binding nature of captopril with ctDNA was confirmed by molecular docking study. Hence, the results gained from current inspection give an explicit visualization of the effects of captopril with ctDNA interaction. [ABSTRACT FROM AUTHOR]

Introduction: More than half of the infants are started on complementary feed before six months. Perception of Inadequate Milk supply (PIM) remains one of the most frequent causes of early institution of complementary feeding. Perception of Inadequate Weight Gain (PIWG), may also influence a mother's decision to start early complementary feeding which may be a consequence of PIM. Aim: To find the proportion of early complementary feeding and to compare predictive models to help identify mothers more likely to initiate early complementary feeds. Materials and Methods: A descriptive epidemiological study with cross-sectional design was carried out for three months between May-July 2013 among 99 mother-child dyads, with children in the 6-24 months age group, residing in Matigara block of West Bengal. Data were collected regarding infant feeding practices and prevalence of early complementary feeding was calculated. Logistic regression was done using SPSS Version 20.0 with the predictor variables classified under three constructs of socio-demography, health system related factors and mothers perceptions; and models were constructed using one, two or all three constructs. Results: The proportion of early complementary feeding was 30.3%. In univariate analysis, none of the variables were found to be statistically significant. However, on multivariate analysis, Model (with all variables) was found to be statistically significant. The best Area Under Curve (AUC) was found with the inclusion of the socio-demography, health system related factors and mothers' perception. Conclusion: The perception of the mother regarding adequacy of her milk production and regarding the child's weight gain are the most important predictors of early initiation of complementary feeding. All counselling activities for the mother should therefore be designed in a way as to address these issues. [ABSTRACT FROM AUTHOR]

Concrete is used in great volumes for construction of buildings, roads, sewer systems, marine structures, bridges, and tunnels. Although chemical degradation is regarded as the major cause of their deterioration, recent research has revealed important role of biogenic deterioration. In particular, biogenic deterioration is a serious problem in sewer systems, subsea pipelines, bridge piers, oil and gas pipelines, and offshore platforms. Recently, nanomaterial-embedded concrete and nanomaterial-incorporated coatings with novel functionalities such as self-protection and anti-corrosion ability have been successfully developed for prevention and control of concrete deterioration. This paper presents an overview of both existing control measures and recent progress on development of nano-enabled approaches for protection of concrete structures against biogenic deterioration. [ABSTRACT FROM AUTHOR]

The interaction of 5H-naptho[2,1 -f ][1,2]oxathieaphine2,2-dioxide (NOTD) with calf thymus DNA in Tris-HCl buffer at physiological pH was investigated with the help of various spectroscopic and electrochemical methods along with molecular docking study. Studying the non-covalent binding interaction of a neutral fluorophore with ctDNA has become an active field of research at the interface between medicinal chemistry and biological science. NOTD is known for its various toxicological, skin sensitization, and antiviral properties. Still, to date, its interaction style with ctDNA is not well elucidated. UV–vis absorption, fluorescence emission and circular dichroism spectroscopy (CD) suggest the complex formation between NOTD and ctDNA with binding constant value in the order of 3.12-4.1( × 10 4 ) M −1 . Binding nature of NOTD with ctDNA is affirmed from the DNA helix melting experiment, comparative displacement assay using known DNA intercalator, cyclic voltammetry and finally molecular docking study. It was evident from experimental result that the probe NOTD binds with ctDNA in groove binding mode as manifested by a decrease in iodide quenching effect, spectral change in CD, a substantial increase in denaturing temperature in DNA and change in potential value. Furthermore, the molecular docking study insisted the above mentioned experimental result in a very affectionate way. [ABSTRACT FROM AUTHOR]

Maintenance of ever-expanding road networks all over the world is a critical task and regular monitoring of the road surface is imperative for successful maintenance. Existing monitoring techniques use dedicated vehicles equipped with sensors. Limited availability of these specialized vehicles makes regular monitoring very challenging. This paper explores a novel approach of empowering the smartphone user community for monitoring roads that they use. Smartphones are used for sensing the road surface conditions from a moving vehicle. The system involves client applications on smartphones that collect accelerations as the users travel on the roads, processing of the information and communication to a central server, georeference database, and visualization of road conditions on Google maps. In this paper, the fuzzy logic--based road surface roughness classification is proposed for monitoring the road roughness. The implementation has been demonstrated in different road networks at northern region of India. The experiment demonstrates the huge potential of user community participation in maintenance of road infrastructure. [ABSTRACT FROM AUTHOR]

In this study, we tried to validate groundwater storage (GWS) anomaly obtained from a combination of GRACE and land-surface model based estimates, for the first time, with GWS anomaly obtained from a dense network of in-situ groundwater observation wells within 12 major river basins in India. We used seasonal data from >15,000 groundwater observation wells between 2005 and 2013, distributed all over the country. Two recently released GRACE products, RL05 spherical harmonics (SH) and RL05 mascon (MS) products are used for comparison with in-situ data. To our knowledge, this is the first study of comparing the performance of two independent GRACE products at a sub-continental scale. Also for the first time, we have created a high resolution (0.1 0 × 0.1 0 ) map of specific yield for the entire country that was used for calculating GWS. Observed GWS anomalies have been computed using water level anomalies and specific yield information for the locale of individual observation wells that are up-scaled to basin-scale in order to compare with GRACE-based estimates. In general GRACE-based estimates match well (on the basis of the statistical analyses performed in the study) with observed estimates in most of the river basins. On comparing with observed GWS anomaly, GRACE-SH estimates match well in terms of RMSE, while GRACE-MS estimates show better association in terms of correlation, while the output of skewness, kurtosis, coefficient of variation (CV) and scatter analyses remain inconclusive for inter-comparison between two GRACE estimates. We used a non-parametric trend estimation approach, the Hodrick-Prescott (HP) filter, to further assess the performance of the two GRACE estimates. GRACE-MS estimates clearly outperform GRACE-SH estimates for reproducing observed GWS anomaly trends with significantly (>95% confidence level) strong association in 10 out of 12 basins for GRACE-MS estimates, on the other hand, GRACE-SH estimates show significantly (>95% confidence level) strong association in 6 out of 12 basins. On the basis of the study output, we recommend using GRACE-MS estimates for groundwater studies over the region and other regions of the globe with similar climatic, hydrogeologic or groundwater withdrawal conditions. [ABSTRACT FROM AUTHOR]

Microbial carbonates are emerging as sustainable alternative cementing materials. We explore carbonate mineralisation by three bacterial isolates: Sporosarcina pasteurii , Bacillus pumilis and Bacillus megaterium that produce two enzymes urease and carbonic anhydrase. In vitro CaCO 3 precipitation by bacterial isolates under three different energy sources: urea, NaHCO 3 and CO 2 was monitored quantitatively and qualitatively. Cell viability in different treatments was studied through fluorescent microscopy. Morphological and chemical constituents of the crystals formed by different bacterial isolates were analysed by scanning electron microscopy, X-ray diffraction and Energy dispersive X-ray spectrum. In a first attempt we estimate the mechanical properties of microbial products through nanoindentation and correlate them with the established techniques such as SEM and XRD. The biochemical processes produced a mixture of two forms of carbonate, calcite and vaterite, in different proportions. We demonstrate that it is possible to engineer the mechanical properties of the carbonates by controlling the biochemical processes. [ABSTRACT FROM AUTHOR]

Urease production of calcifying bacterium, Bacillus megaterium SS3 was enhanced by using response surface methodology (RSM) in current study. The preliminary screening by Plackett-Burman's design revealed that among the tested factors, glucose, urea and NaHCO3 significantly ( p < 0.05) enhanced the urease production. Further optimization of urease production by B. megaterium through RSM was achieved as 879 U mL−1 in the presence of glucose (21.7 g L−1), urea (21.1 g L−1) and NaHCO3 (1.9 g L−1) compared to 640 U mL−1 in unoptimized medium. The effect of different factors seems to promote the growth of bacterial isolate leading to improvement in urease production. As production of carbonates by ureolytic bacteria is dependent on urease enzyme, improvement in enzyme production enhanced the carbonate precipitation efficacy to 1.7-fold in optimized medium. Carbonic anhydrase production also increased from 120 U mL−1 to 190 U mL−1 in optimized medium. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Summary The present study interprets the groundwater solute chemistry, hydrogeochemical evolution, arsenic (As) enrichment and aquifer characterization in Brahmaputra River Basin (BRB) involving three geologically and tectono-morphically distinct regions located in northeastern India. These study regions consist of the northwestern (NW) and the northern (N) region, both located along the western and eastern parts of Eastern Himalayas and the southern (S) region (near Indo–Burmese Range and Naga hills) of the Brahmaputra basin which show distinct tectonic settings and sediment provenances in the Himalayan orogenic belt. Stable isotopic composition (δ 2 H and δ 18 O) in groundwater suggests that some evaporation may have taken place through recharging of ground water in the study areas. The major-ion composition shows that groundwater composition of the NW and N parts are between Ca HCO 3 and Ca Na HCO 3 while the S-region is dominated by Na Ca HCO 3 hydrochemical facies. The major mineralogical composition of aquifer sediments indicates the dominant presence of iron(Fe)-oxide and oxyhydroxides, mica (muscovite and biotite), feldspar, pyroxene, amphibole, abundance of quartz and clay minerals whereas clay is predominantly present in sediments of S-aquifers. These mafic minerals, aluminosilicates and clay minerals might offer available reactive surface for As-adsorption and co-precipitatation with amorphous Fe. These associated adsorbed and co-precipitated As might be released due to reductive dissolution of Fe-oxide and oxyhydroxides in groundwater. These minerals are assumed to be possible sources of As in groundwater. The stability diagrams of groundwater data suggest that solute might have been introduced into groundwater from weathering of K-feldspar, plagioclase, pyroxene of Himalayan rocks, the Siwalik Group and Eastern Syntaxes in NW and N-regions. However, basic cations might be derived from weathering of K-feldspar, plagioclase, pyroxene and olivine those being major constituents in a gabbroic complex (ophiolite) and basalt terrain in S-region. The aquifers of S-region are severely contaminated with dissolved As compared to NW and N regions. Almost more than 92% of groundwater samples in the southern part (maximum 5.53 μM or 415 μg/L) are enriched with As, which draws a distinct difference from the NW and N parts of BRB aquifers. The redox-sensitive solutes (i.e., Fe, Mn, HCO 3 − and TOC) are positively correlated with As in NW and N-parts; whereas E H shows negative to very weak positive correlation which suggests that a redox-dependent mobilization plays important role in As liberation in NW and N parts of the basin. However, As in southern aquifers is not showing any correlation or weak negative correlation with redox-sensitive solutes; suggesting that multiple reactions and hydrogeochemical processes and their interaction control As mobilization and fate in the S-region of BRB. The occurrence of high concentrations of arsenic in groundwater of Brahmaputra basin is described through a crustal recycling model and tectonic movement between the Indian–Eurasian plates and Burmese micro-continents. As-enriched groundwater in Himalayan foreland basin in the BRB is probably a result of crustal evolution through which As is subsequently mobilized from aquifer matrix to solution in groundwater by water–sediment reaction under favorable biogeochemical conditions. The results of the study indicate geological control (i.e. change in lithofacies, tectonic set-up) on groundwater chemistry and distribution of redox-sensitive solutes such as As. [ABSTRACT FROM AUTHOR]

• Top-bar effect induces a much earlier corrosion initiation but postpones the crack initiation in reinforced concrete. • Top-bar effect changes the pattern of corrosion which can mislead the interpretation of ultrasonic results. • The combined electrochemical and ultrasonic method enables comprehensive evaluation and monitoring of concrete corrosion. • Discerns the patterns of corrosion of reinforced concrete with and without the top-bar effect. Top-bar defect in reinforced concrete (RC) leads to the formation of interfacial voids underneath the reinforcements at an elevation of 300 mm or more. Rebars with top-bar defects show earlier corrosion initiation, faster corrosion rate and a different pattern of corrosion, compared to those without. This paper proposes combined electrochemical and ultrasonic methods for monitoring incipient corrosion in RC. An RC wall structure is cast vertically aiming to create top-bar defect. The specimens were subjected to accelerated chloride-induced corrosion. Simultaneously, they have been monitored with half-cell potential method (HCP), linear polarisation resistance method (LPR), ultrasonic guided waves (GW) and ultrasonic imaging (UI). The pros and cons of the four techniques are determined and discussed. The results are correlated and calibrated with the state of corrosion. Key milestones of the corrosion mechanism such as corrosion initiation and crack initiation can be successfully identified and the progression of bar deterioration, steel-concrete interfacial debonding and cracking propagation have been traced. [ABSTRACT FROM AUTHOR]

Summary Submarine groundwater discharges (SGD) play a major role in solute transport and nutrient flux to the ocean. We have conducted a spatio-temporal high-resolution lunar-tidal cycle-scale seepage meter experiment during pre-monsoon and post-monsoon seasons, to quantify the spatio-temporal patterns and variability of SGD, its terrestrial (T-SGD) and marine components (M-SGD). The measured daily average SGD rates range from no discharge to 3.6 m 3 m −2 d −1 during pre-monsoon season and 0.08–5.9 m 3 m −2 d −1 during post-monsoon seasons, depending on the tidal pattern. The uncertainty for SGD measurement is calculated as ±0.8% to ±11% for pre-monsoon and ±1.8% to ±17% for post-monsoon respectively. A linear, inverse relationship was observed between the calculated T-SGD and M-SGD components, which varied along the distance from the coast and position in the tidal-cycle, spatial and temporal (daily) variations of seepage rates within the lunar tidal cycle period distinctly demonstrate the influence of tides on groundwater seepage rate. As an instance, for the identification of the bulk discharge location, the centroid of the integrated SGD rate has been calculated and found to be near 20 m offshore area. The average discharge rate per unit area further extrapolated to total SGD fluxes to the Bay of Bengal from eastern Indian coast by extrapolation of the annual and seasonal fluxes observed in the study area, which are first direct/experimental estimate of SGD to the Bay of Bengal. Approximations suggest that in present-day condition, total average annual SGD to the Bay of Bengal is about 8.98 ± 0.6 × 10 8 m 3 /y. This is suggested that the SGD input to the ocean through the Bay of Bengal is approximately 0.9% of the global input from the inter-tidal zone and that has an implication on the mass balance of discharging solutes/nutrients to the global oceans. High T-SGD input is observed for all season, which is largest toward landward direction from the delineated saltwater–freshwater interface. The high magnitude of T-SGD could play an important role in mass balance of fresh water discharge and solute transport to the global ocean, thereby influence coastal ecohydrological systems. [ABSTRACT FROM AUTHOR]

Moisture diffusion through a unidirectional fibre reinforced polymer matrix composite is studied. The stresses due to the expansion of the matrix caused by moisture diffusion are evaluated. A three-dimensional (3D) micromechanical model is developed to study diffusion both across and along the fibre. The well-known 2D plane strain condition is modelled and validated as a special case of the 3D model. The utility of 3D modelling is further demonstrated to analyse the stress along the fibre length. It is demonstrated that the variation of boundary conditions along the fibre length has a dramatic effect on the stresses. The stresses along fibre length computed through finite element analysis (FEA) are compared against an analytical solution obtained from axi-symmetric concentric cylinder assemblage (CCA) model. This paper demonstrates the importance of 3D diffusion kinetics in unidirectional reinforced polymer composites. [ABSTRACT FROM AUTHOR]

This paper presents a numerical study of moisture propagation in fibre reinforced polymer (FRP) materials with spatial tortuosity. An algorithm for creation of microstructures with clustered fibre architecture is presented. Several controls for different characteristics of the clusters are described. Different statistical descriptors of geometry are used to quantify the clustering. A Fickian diffusion process has been modelled. The effect of clustering on moisture diffusion through the FRP is reported. It is observed that microstructures greatly affect the diffusion behaviour of the FRP. Correlation between moisture diffusion and the statistical descriptors has been examined. The statistical measures that depict the global characteristics of the microstructure are found to have a better correlation with time to saturate the representative volume element. The results should help in prediction of macroscopic response and durability of FRPs. [ABSTRACT FROM AUTHOR]

Cetyl trimethyl ammonium bromide (CTAB) binds calf thymus (ct-) DNA like anionic biopolymers electrostatically and established equilibrium both in the ground as well as in excited state in aqueous medium at pH 7. Anionic sodium dodecyl sulfate (SDS) does not show even hydrophobic interaction with ct-DNA at low concentration. On contrary, SDS can establish well defined equilibrium with DNA bound CTAB in ground state where the same CTAB–DNA isosbestic point reappears. First report of internal charge transfer (ICT) based binding of CTAB with ct-DNA as well as ICT based interaction of anionic SDS with DNA bound CTAB that shows dynamic quenching contribution also. The reappearance of anodic peak and slight increase in cathodic peak current with increasing concentration (at lower range) of anionic SDS, possibly reflect the release of CTAB from DNA bound CTAB by SDS. [ABSTRACT FROM AUTHOR]

Summary Submarine groundwater discharge (SGD) to the Bay of Bengal is an important groundwater discharge process to southern Asia as well as to the global oceans. Water-fluxes in these regions are not very well understood. The present study demonstrates the use of sea-bed porewater temperature as a tracer for delineating seasonal SGD from a shallow coastal aquifer to the Bay of Bengal. Porewater temperature mapping along with chemical profile of porewater column were used to delineate groundwater discharge zones for different seasons in a hydrologic year. While, the temperature profiles were used to evaluate total groundwater discharge (both terrestrial and marine), the salinity and total dissolved solids profiles were used to evaluate the component due to terrestrial (freshwater) discharge. Several springs and seeps were mapped to finger-print the freshwater discharge zones and identify the terrestrial sourced-SGD temperature windows. These zones are also identified to be enriched with algal mats, and hence may indicate the pathways of nutrient–solute discharge that enhance the primary productivity in the marine ecosystem. Assuming vertical flow in the seabed, simulated rates of discharged groundwater provided a good match with measured discharge rates. The porewater fluxes were estimated by applying analytical solutions of the heat conduction–advection equations to the observed vertical temperature profiles. High resolution thermal profiles to identify T-SGD signatures and chemical profiles along mapped transects reveal the nuances of 3-D seasonal hydrodynamics of groundwater–seawater interactions. The calculated vertical porewater fluxes through the seabed ranged from negligible to 2.45 × 10 −2 m 3 /m 2 /d 1 within a zone extending from high tide line to 40 m offshore, and represent the vertical porewater velocity and the average vertical porewater velocity is found as 8.2 × 10 −3 m 3 /m 2 /d 1 . Approximations suggest that in present-day condition, total average annual SGD to Bay of Bengal is about 1.16 × 10 7 m 3 /y. Seasonal estimates suggest that the averages SGD during pre-monsoon and post-monsoon seasons are ranges 0.6–0.8 × 10 7 m 3 /y for pre-monsoon and 0.8–1.5 × 10 7 m 3 /y for post-monsoon, respectively. The findings suggest that monsoonal activity result in a significant porewater displacement from tidal flat sediments by increased groundwater discharge. [ABSTRACT FROM AUTHOR]

Rapid urbanisation has accelerated consumption of concrete making it the most consumed artificial material. Present day concrete is one of the largest sources of anthropogenic greenhouse gas emission and is not sustainable. Microbial precipitation of CaCO 3 is a promising way of emulating nature’s sustainable ways. This paper reviews current progress and potential of this technology. Prior research on the modes of application of the technology and consequent gains in strength and durability of construction materials has been summarised. Imperatives for a quantitative estimate of sustainability are identified. Progress necessary for industrial adoption of the technology has been discussed. [ABSTRACT FROM AUTHOR]

Modern civilization is facing the dichotomy of rapid development of infrastructure that makes concrete as most traded material on the earth other than water. However, the production of cement, key ingredient of concrete, releases roughly a tonne of CO 2 into the environment with each tonne of cement production. The environmental concerns and sustainability issues associated with cement and concrete necessitate alternative and better approach in the construction. Nature, on the other hand, has a plethora of examples of sustainable habitats such as coral reefs, silk webs and ant hills. Recent advances in biotechnology have great potential of emulating nature’s way of building in modern days infrastructures at a scale that would sustain increasing population. Further, many of the biological materials of nature, be it ceramics or polymeric composites formed in the process of biomineralization, provides basis for sustainable construction. This paper elaborates nature’s way of construction based on biomineralization and discusses the progress of different biological pathways for sustainable construction. Main milestones achieved have been identified and the effect of biological intervention on the properties of structural materials has been highlighted. Variety of applications of biomineralization based technology in the construction has been reported. The paper briefly documents the future directions of the technology. [ABSTRACT FROM AUTHOR]

Diffusion of moisture through fibre reinforced polymers (FRP) is one of the main environmental causes of their deterioration and loss of service life. Moisture diffusion and the resulting stresses in a fibre–matrix system vary considerably with the topology of the fibres inside the polymer matrix. This paper reports a numerical study on stress build up in FRP due to moisture diffusion. The Fickian diffusion model is implemented. Stresses due to the transient moisture distribution have been estimated using a finite element model. Some fundamental topologies have been studied. Most important topological parameters have been identified. Utilising the results of fibre neighbourhood, interpretation of large microstructures has been discussed. Considerable interactions among neighbouring fibres can be observed in the stress build up. The results should help in designing moisture impeding microstructures for FRP and prolong their life. [ABSTRACT FROM AUTHOR]

Background: Programmatic management of drug-resistant TB (PMDT) under the RNTCP is being implemented in West Bengal in a phased manner since 2011. During the initial years MDR-TB cases were identified based on criteria A. This study examines the first line anti-tubercular drug resistance pattern of mycobacteria cultured from sputum samples of MDR suspects who were retreatment cases smear positive from 4th month onwards. Materials and Methods: In the following retrospective record based study, data on Drug Sensitivity Testing (DST) of sputum samples of MDR suspects between September 2011 and August 2012 were collected from the IRL Kolkata and analysed. Sputum samples, collected in the districts maintaining adequate aseptic containment measures, were decontaminated and centrifuged and the sediment inoculated on LJ medium. Probable M. tuberculosis colonies were identified by typical colony characteristics and Ziehl-Neelsen (ZN) staining. Sensitivity of the four 1st line drugs (Streptomycin, Isoniazid, Ethambutol and Rifampicin) was deduced by the economic variant of the proportion method. Results: Of all the 917 MDR suspects whose sputum was examined, 64 mycobacteria culture positive strains (6.98%) were mono-resistant to any of the four first line anti-tubercular drugs. Among the mono-resistant strains 43 (4.69%) were resistant to Rifampicin while 12 (1.31%) were resistant to INH. There were a total 78 (8.51%) poly drug-resistant strains. MDR-TB strains were seen in 741 (80.81%) samples. Conclusion: The magnitude of drug resistance were very high among retreatment patients that were smear positive from 4th months onwards probably because of repeated courses of anti-tubercular drugs prior to drug sensitivity testing (DST). The decision of the PMDT to enlist all retreatment patients as MDR suspects at initiation will result in early identification and treatment of MDR-TB patients. [ABSTRACT FROM AUTHOR]

Durability and strength of mature concrete can be judged a great deal from its properties when it is freshly poured. This paper demonstrates an ultrasonic in-situ monitoring technique for freshly poured concrete. The solidification and curing of freshly poured concrete is monitored through the propagation of ultrasonic waves in waveguides such as steel reinforcing bars. As concrete solidifies and cures, more wave energy escapes into the surrounding concrete resulting in signal attenuation. RC beam specimens are monitored with carefully selected ultrasonic signal patterns during the first 24 h of setting of concrete. Destructive tests such as bar pull out and compressive strength are also performed at different stages of setting of concrete. The ultrasonic signals have been calibrated for determination of early age concrete properties. [ABSTRACT FROM AUTHOR]

Influence of microarchitectural fiber matrix arrangement in representative volume element is studied to assess the effect of mass diffusion in the fiber-reinforced polymer composites. A novel approach has been proposed to illustrate the quantitative definition of the representative volume element heterogeneity using topological descriptor of clustering. Average fiber center distance from the fixed representative volume element center is described to compute the clustering in different representative volume elements, followed by finite element method simulation to model and visualize two-dimensional microstructures of fiber-reinforced matrix composites with moisture boundary conditions. The suggested topology descriptor shows good correlation with diffusion response in relation to saturation time, whereas a fair degree of correlation was observed for mass accumulation and mass flux characteristics. The results indicate that microstructural heterogeneity has a strong influence on typical moisture diffusion characteristics and hence, an overall diffusion-induced damage. The observations should serve as a clue to design the fiber-reinforced polymer composites with the moisture barrier properties. [ABSTRACT FROM AUTHOR]

SUMMARY This paper reports a non-contact, in-situ and non-destructive corrosion monitoring methodology for submerged plates using ultrasonic guided waves. Specific surface sensitive and core sensitive guided wave modes are utilized for monitoring plates undergoing accelerated impressed current corrosion in the presence of chlorides. A combination of the selected guided wave modes could effectively discern various corrosion mechanisms occurring in plates. Along with the ultrasonic signals, mass loss, stress-strain behaviour and tensile strength of the plates at different stages of corrosion have been monitored. Algebraic relationships between the ultrasonic readings and other parameters have been developed. This investigation should be useful in developing a non-destructive technique for monitoring progressive corrosion in plates and assessing their deterioration in strength, stiffness and mass loss that would help in the estimation of residual life. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]