Holistic assessment of microplastics in various coastal environmental matrices, southwest coast of India

Plastics in the marine environment are introduced through multiple pathways, and pose serious threats to aquatic biota. Recently microplastic pollution and its possible consequences in India have been recognized by the scientific community, however the extent of the crisis has not yet been quantified. The present study attempted to ascertain the abundance, distribution and characteristics of microplastics in coastal waters (14 locations), beach sediments (22 locations) and marine fishes (11 locations) from the state of Kerala, southwest coast of India. The results showed that the mean microplastic abundance was 1.25 ± 0.88 particles/m³ in coastal waters and 40.7 ± 33.2 particles/m² in beach sediments with higher concentrations in the southern coast of the state. The abundance of microplastics, mostly contributed by fragments, fibre/line and foam, in both coastal waters and beach sediments, were highly influenced by river runoff and proximity to urban agglomeration. Fourier Transform Infrared Spectroscopy-Attenuated Total Reflection (FTIR-ATR) revealed that polyethylene (PE) and polypropylene (PP) were the dominant polymers in the marine environment. The digestive tracts of 15 out of 70 commercially important fishes studied, contained 22 microplastic particles. Polyethylene (PE; 38.46%) followed by cellulose (CE; 23.08%), rayon (RY; 15.38%), polyester (PL; 15.38%) and polypropylene (PP; 7.69%) were the major contributors in the fish ingested microplastic composition. A broad range of heavy metals, metalloids and other elements that are potentially indicative of hazardous chemicals were present in microplastics collected from the beaches of Kerala. These results enhance our understanding on the sources, transport pathways and the associated environmental risks of microplastics to marine ecosystems.

A Method and an Experimental Setup for Measuring the Self-Noise of Piezoelectric Hydrophones

Self-noise of hydrophone is one of the important parameters for critical sonar applications, as it finally decides the lowest detectable signal from a target. To measure the ambient noise of the ocean, the self-noise of the hydrophone should be much less than the sea state zero (SS0) noise. Hence, an experimental setup is required to measure the self-noise generated by the hydrophones. An experimental setup has been designed, developed, and demonstrated. The facility consists of a vibration-isolated and EMI-shielded vacuum chamber which encloses the sample holder assembly and effectively isolates the test hydrophones from external environmental noise sources, such as ground vibrations, electromagnetic interference, and airborne acoustic noises. This enables the measurement of self-noise that is originating purely within the hydrophone. A procedure is developed to remove the noise contribution of the preamplifier including its resistors from the measured output signal of the preamplifier. Uncertainty in measurement using this setup is estimated using the propagation of distribution method through Monte Carlo simulation. This article describes the factors contributing to the self-noise in piezoelectric (PE) transducers, the noise measurement principle, the constructional details of the experimental setup, and the calibration procedure. The technique is demonstrated by measuring the self-noise of a few different types of hydrophones. Thermal noise as low as 0.5 nV / √{Hz} with an estimated uncertainty of 0.5 nV / √{Hz} with a confidence level of 95% is achieved.

Challenges Calibrating Hydrology for Groundwater-Fed Wetlands: a Headwater Wetland Case Study

This study aims to adapt the Soil and Watershed Assessment Tool (SWAT), a ubiquitously used watershed model, for ground-water dominated surface waterbodies by accounting for recharge from the aquifers. Using measured flow to a headwater slope wetland in Alabama's coastal plain region as a case study, we present challenges and relatively simple approaches in using the SWAT model to predict flows from the draining watershed and relatively simple approaches to model groundwater upwelling. SWAT-simulated flow at the study watershed was limited by precipitation, and consequently, simulated flows were several times smaller in magnitude than observed flows. Thus, our first approach involved a separate stormflow and baseflow calibration which included the use of a regression relationship between observed and simulated baseflow (E NASH = 0.67). Our next approach involved adapting SWAT to simulate upwelling groundwater discharge instead of deep aquifer losses by constraining the range of deep losses, β deep parameter, to negative values (E NASH = 0.75). Finally, we also investigated the use of artificial neural networks (ANN) in conjunction with SWAT to further improve calibration performance. This approach used SWAT-calibrated flow, evapotranspiration, and precipitation as inputs to ANN (E NASH = 0.88). The methods investigated in this study can be used to navigate similar flow calibration challenges in other groundwater dominant watersheds which can be very useful tool for managers and modelers alike.

Evaluation of Single-Nucleotide Polymorphisms of Transcription Factor 7-Like 2 and ATP2B1 Genes as Cardiovascular Risk Predictors in Chronic Kidney Disease

Introduction:

Cardiovascular disease (CVD) is the primary cause of morbidity and premature mortality in chronic kidney disease (CKD). The transcription factor 7-like 2 (TCF7L2) gene product TCF4 is a transcription factor that acts as a downstream effector in the canonical Wnt signaling pathway and may be important in the development of both type 2 diabetes and renal development and disease. It is, therefore, plausible that mutations in this gene could manifest themselves in reduced kidney function or kidney disease through their effects on hyperglycemia as well as independent of this mechanism. The ATP2B1 gene encodes the plasma membrane calcium ATPase isoform 1, which removes bivalent calcium ions from eukaryotic cells against very large concentration gradients and is responsible for controlling the contraction and dilation of vascular smooth muscles.

Aim and Objectives:

The aims of this study are (1) to evaluate single-nucleotide polymorphisms (SNPs) of TCF7L2 gene as cardiovascular risk predictors in CKD and (2) to evaluate SNPs of ATP2B1 gene as cardiovascular risk predictors in CKD.

Subjects and Methods:

Fifty clinically diagnosed CKD patients in the age group between 20 and 60 years of both genders were selected as cases and fifty healthy participants from the master health checkup department were selected as controls. Genomic DNA was extracted based on the spin column kit method. The DNA samples were stored at −20°C until analysis. Genotyping for TCF7L2 gene rs7903146 (C/T) and ATP2B1 gene rs11105354 (A/G) was carried out through polymerase chain reaction.

Results:

T allele frequency was observed in 12 controls and 23 cases (odds ratio [OR] = 2.2, 95% confidence interval [CI]: 1.0–4.7). CC genotype was observed in 38 controls and 27 cases and CT genotype in 22 cases and 12 controls. A allele was found in 38 cases and 23 controls (OR = 2, 95% CI: 1.1–3.8). The mean values of cholesterol, low-density lipoprotein, triglycerides, glucose, insulin, urea, and creatinine were high in cases when compared to controls.

Conclusion:

T allele of TCF7L2 gene rs7903146 (C/T) and A allele of ATP2B1 (A/G) gene rs11105354 (A/G) are associated with CVD in CKD patients.

Emergence of the Vortex State in Confined Ferroelectric Heterostructures

The manipulation of charge and lattice degrees of freedom in atomically precise, low-dimensional ferroelectric superlattices can lead to exotic polar structures, such as a vortex state. The role of interfaces in the evolution of the vortex state in these superlattices (and the associated electrostatic and elastic boundary conditions they produce) has remained unclear. Here, the toroidal state, arranged in arrays of alternating clockwise/counterclockwise polar vortices, in a confined SrTiO₃ /PbTiO₃ /SrTiO₃ trilayer is investigated. By utilizing a combination of transmission electron microscopy, synchrotron-based X-ray diffraction, and phase-field modeling, the phase transition as a function of layer thickness (number of unit cells) demonstrates how the vortex state emerges from the ferroelectric state by varying the thickness of the confined PbTiO₃ layer. Intriguingly, the vortex state arises at head-to-head domain boundaries in ferroelectric a₁ /a₂ twin structures. In turn, by varying the total number of PbTiO₃ layers (moving from trilayer to superlattices), it is possible to manipulate the long-range interactions among multiple confined PbTiO₃ layers to stabilize the vortex state. This work provides a new understanding of how the different energies work together to produce this exciting new state of matter and can contribute to the design of novel states and potential memory applications.

Author Correction: Spatially resolved steady-state negative capacitance

In this Letter, the first name of author Bhagwati Prasad was misspelled Bhagawati. This error has been corrected online.

Optical creation of a supercrystal with three-dimensional nanoscale periodicity

Stimulation with ultrafast light pulses can realize and manipulate states of matter with emergent structural, electronic and magnetic phenomena. However, these non-equilibrium phases are often transient and the challenge is to stabilize them as persistent states. Here, we show that atomic-scale PbTiO₃/SrTiO₃ superlattices, counterpoising strain and polarization states in alternate layers, are converted by sub-picosecond optical pulses to a supercrystal phase. This phase persists indefinitely under ambient conditions, has not been created via equilibrium routes, and can be erased by heating. X-ray scattering and microscopy show this unusual phase consists of a coherent three-dimensional structure with polar, strain and charge-ordering periodicities of up to 30 nm. By adjusting only dielectric properties, the phase-field model describes this emergent phase as a photo-induced charge-stabilized supercrystal formed from a two-phase equilibrium state. Our results demonstrate opportunities for light-activated pathways to thermally inaccessible and emergent metastable states.

Advances in magnetoelectric multiferroics

The manipulation of magnetic properties by an electric field in magnetoelectric multiferroic materials has driven significant research activity, with the goal of realizing their transformative technological potential. Here, we review progress in the fundamental understanding and design of new multiferroic materials, advances in characterization and modelling tools to describe them, and the exploration of devices and applications. Focusing on the translation of the many scientific breakthroughs into technological innovations, we identify the key open questions in the field where targeted research activities could have maximum impact in transitioning scientific discoveries into real applications.

Tailoring Magnetoelectric Coupling in BiFeO3 /La0.7 Sr0.3 MnO3 Heterostructure through the Interface Engineering

Electric field control of magnetism ultimately opens up the possibility of reducing energy consumption of memory and logic devices. Electric control of magnetization and exchange bias are demonstrated in all-oxide heterostructures of BiFeO₃ (BFO) and La_0.7 Sr_0.3 MnO₃ (LSMO). However, the role of the polar heterointerface on magnetoelectric (ME) coupling is not fully explored. Here, the ME coupling in BFO/LSMO heterostructures with two types of interfaces, achieved by exploiting the interface engineering at the atomic scale, is investigated. It is shown that both magnetization and exchange bias are reversibly controlled by switching the ferroelectric polarization of BFO. Intriguingly, distinctly different modulation behaviors that depend on the interfacial atomic sequence are observed. These results provide new insights into the underlying physics of ME coupling in the model system. This study highlights that designing interface at the atomic scale is of general importance for functional spintronic devices.

Oil-Spill Triggered Shift in Indigenous Microbial Structure and Functional Dynamics in Different Marine Environmental Matrices

Microbial degradation has long been recognized as the key rescue mechanism in shaping the oil polluted marine environments and the role of indigenous populations or their functional genomics have never been explored from Indian marine environments, post an oil spill event. In the current study, high throughput metagenomic analysis, PLFA profiling and mass spectrophotometric analysis was performed in combination with metabolomics to capture signature variations among the microbial communities in sediment, water and laboratory enrichments. Contrary to the previous reports, the bloom of Pseudomonadales (specifically genus Acinetobacter) in oiled sediment and Methylococcales in oiled water outnumbered the relative abundance of Alcanivorax in response to hydrocarbon contamination. Overall enhancement of xenobiotic degradation was suggested by metabolomic analysis in sediment and water post the spill event and varying quantitative assemblage of enzymes were found to be involved in hydrocarbon utilization. Laboratory enrichments revealed the competitive advantage of sediment communities over the water communities although unique taxa belonging to the later were also found to be enriched under in vitro conditions. Simultaneous analysis of sediment and water in the study provided explicit evidences on existence of differential microbial community dynamics, offering insight into possibilities of formulating nature identical solutions for hydrocarbon pollution.

Marine snakes of Indian coasts: historical resume, systematic checklist, toxinology, status, and identification key

We compile an up-to-date checklist of 26 species of marine snakes known from the Indian coastlines. We furnish information on the original orthography, authorship, date of publication, current binominal representation, synonymy and chresonymy lists for each recognized taxon.  In addition, we provide details of name-bearing types, repository and type locality (both original and subsequent restrictions where applicable) of the prevailing nomen for all recognized species.  We summarise the history of research on Indian marine snakes from Linnaeus to the present day, including taxonomic and regional treatises, and highlight the taxonomic flux.  We also provide a revised key for this group to facilitate easier identification and support effective conservation. 

Correlation of Symphysiofundal Height and Abdominal Girth with the Incidence of Hypotension in Cesarean Section Under Spinal Anesthesia using Bupivacaine with Fentanyl as Adjuvant: A Clinical Study

Background and Aims:

A decreased lumbosacral subarachnoid space volume is a major factor in cephalad intrathecal spread of local anesthetic in term parturients due to compressive effect of the gravid uterus. The aim of this study was to assess the relationship of symphysiofundal height (SFH) and abdominal girth (AG) with the incidence of hypotension and the highest level of sensory blockade.

Settings and Design:

This study was a prospective observational study.

Materials and Methods:

Ninety parturients under the American Society of Anesthesiologists physical status class II within the age range of 20–30 years, weighing between 60 and 65 kg, and height between 150 and 155 cm were studied, and the SFH and AG of all parturients had been measured just before spinal anesthesia. Hyperbaric bupivacaine 9 mg with 12.5 μg intrathecal fentanyl was administered for subarachnoid block. The incidence of hypotension and the highest level of sensory block were assessed.

Statistical Analysis:

Correlation analysis (Spearman's rank test) was applied to analyze the data, and P < 0.05 was considered to be statistically significant.

Results:

The incidence of hypotension was higher with increasing SFH (16.9% with SFH of 30–35 cm, 78.37% with SFH of 36–40 cm; correlation coefficient ρ =0.338) and with increasing AG (5.3% with AG between 85 and 89 cm, 35.7% with AG 90–94 cm, 62.8% with AG 95–99 cm; ρ =0.341), and both were statistically significant (P < 0.001). There was a statistically significant correlation between increasing SFH and maximum sensory block achieved (ρ =0.157, P < 0.001). There was increased level of sensory blockade with increased AG but was not statistically significant (ρ =0.011, P = 0.32).

Conclusion:

In term parturients undergoing cesarean section under spinal anesthesia, the SFH has a significant positive correlation with the incidence of hypotension and ascent of spinal anesthesia. AG also has a positive correlation with the incidence of hypotension but is not significant with the ascent of spinal anesthesia.

Microplastics along the beaches of southeast coast of India

Occurrence of microplastics (plastic debris <5 mm) along the coast is a growing concern worldwide, due to increased input of discarded wastes from various sources. In order to evaluate the extent of microplastic pollution on the sandy beaches (25 locations) along Tamil Nadu coast (1076 km), India, microplastic debris were quantified and categorized into four different size classes. The beaches were classified according to potential sources of pollution i.e. riverine, tourism and fisheries. Beach samples collected from the high tide line contained significantly higher abundance of microplastic than at the low tide line. Beaches adjacent to rivers exhibited relatively higher microplastic abundance compared to those influenced by tourism and fishing activities. Out of the total detected debris, plastic fragments were the maximum (47-50%), followed by line/fibres (24-27%) and foam (10-19%) materials. Fourier Transform Infrared Spectroscopy (FTIR) analysis revealed that polyethylene, polypropylene, and polystyrene were the main types of microplastics present in these beaches. Gut content analysis of commercially important fishes, collected from the coastal waters, revealed microplastics ingestion in 10.1% of fishes. The results indicate that microplastics accumulation in the coastal environment, especially close to the river mouths, may be a serious concern, due to its ability to enter into the marine food web and highlights the necessity of microplastics screening from estuarine, coastal waters and other potential sources.

Seagrass litter decomposition: an additional nutrient source to shallow coastal waters

Seagrass ecosystems are vital for its regulatory services yet, highly threatened by degradation due to human pressures. Decomposition of two tropical seagrass species (Cymodocea serrulata and Cymodocea rotundata) was studied and compared, to understand their potential in generating additional nutrients to coastal waters. Release of carbon, nitrogen and phosphorus during the decomposition process of seagrass wracks was estimated in bacteria-active (non-poisoned) and bacteria-inhibited (poisoned) conditions from shore-washed fresh seagrass, sampled from Palk Bay, India. Incubation experiments for 25 days indicated a near three times higher concentration of dissolved organic carbon (DOC) in bacteria-inhibited flasks compared to bacteria-active conditions for both species. The maximum leaching rates of DOC, TDN and TDP were found to be 294, 65.1 and 11.2 μM/g dry wt/day, respectively. Further, higher release of dissolved inorganic nitrogen (DIN) (> 1.3 times) was documented from the bacteria-active flask, highlighting the significance of microbial process in generating bio-available nutrients from decaying seagrass. Faster decomposition (0.014 ± 0.004 day^-1) in the initial stages (up to 8 days) compared to the later stages (0.005 ± 0.001 day^-1) indicated a rapid loss of biomass carbon during the initial leaching process and its relative importance in the decomposition pathway. The decomposition rate is best described by a single-stage exponential decay model with a half-life of 41 days. It is estimated that the total seagrass litter available along the Palk Bay coast is about ~ 0.3 Gg with high potential of additional nitrogen (0.9 ± 0.5 Mg) and phosphorus (0.3 ± 0.1 Mg) supply to the adjacent coastal waters.

Voltage control of unidirectional anisotropy in ferromagnet-multiferroic system

Demonstration of ultralow energy switching mechanisms is imperative for continued improvements in computing devices. Ferroelectric (FE) and multiferroic (MF) order and their manipulation promise an ideal combination of state variables to reach attojoule range for logic and memory (i.e., ~30× lower switching energy than nanoelectronics). In BiFeO₃ (BFO), the coupling between the antiferromagnetic (AFM) and FE order is robust at room temperature, scalable in voltage, stabilized by the FE order, and can be integrated into a fabrication process for a beyond-CMOS (complementary metal-oxide semiconductor) era. The presence of the AFM order and a canted magnetic moment in this system causes exchange interaction with a ferromagnet such as Co_0.9Fe_0.1 or La_0.7Sr_0.3MnO₃. Previous research has shown that exchange coupling (uniaxial anisotropy) can be controlled with an electric field. However, voltage modulation of unidirectional anisotropy, which is preferred for logic and memory technologies, has not yet been demonstrated. Here, we present evidence for electric field control of exchange bias of laterally scaled spin valves that is exchange coupled to BFO at room temperature. We show that the exchange bias in this bilayer is robust, electrically controlled, and reversible. We anticipate that magnetoelectricity at these scaled dimensions provides a powerful pathway for computing beyond modern nanoelectronics by enabling a new class of nonvolatile, ultralow energy computing elements.

Seagrass and macrophyte mediated CO2 and CH4 dynamics in shallow coastal waters

Seagrass meadows are among the most important coastal/ marine ecosystems for long-term carbon storage and conditioning of coastal waters. A combined air-water flux of CO2 and CH4 from the seagrass meadows was studied for the first time from Asia's largest brackish-water lagoon, Chilika, India. Ecosystem-based comparisons were carried out during two hydrologically different conditions of dry and wet seasons in the seagrass dominated southern sector (SS); macrophyte-dominated northern sector (NS); the largely un-vegetated central sector (CS) and the tidally active outer channel (OC) of the lagoon. The mean fluxes of CO2 from SS, NS, CS and OC were 9.8, 146.6, 48.4 and 33.0mM m-2d-1, and that of CH4 were 0.12, 0.11, 0.05 and 0.07mM m-2d-1, respectively. The net emissions (in terms of CO2 equivalents), considering the global warming potential of CO2 (GWP: 1) and CH4 (GWP: 28) from seagrass meadows were over 14 times lower compared to the macrophyte-dominated sector of the lagoon. Contrasting emissivity characteristics of CO2 and CH4 were observed between macrophytes and seagrass, with the former being a persistent source of CO2. It is inferred that although seagrass meadows act as a weak source of CH4, they could be effective sinks of CO2 if land-based pollution sources are minimized.

Nitrogen uptake potential under different temperature-salinity conditions: Implications for nitrogen cycling under climate change scenarios

As projected by climate change models, increase in sea surface temperature and precipitation in the future may alter nutrient cycling in the coastal regions due to potential changes in phytoplankton community structure and their ability to assimilate nitrogen (N) and carbon (C). An experiment simulating different temperature and salinity conditions (28^°C-35 ambient conditions, 28^ºC-31, 31^ºC-35 and 31^ºC-31) in mesocosms containing 1000 L of coastal water from the Arabian Sea was performed and N uptake rates were measured using ¹⁵N tracer technique on 2^nd, 5^th, 7^th and 10^th day of the experiment. The results show that, under all conditions, the total N (NO₃^- + NH₄⁺) uptake rates were lower in the beginning and on the final day of the tracer experiment, while it peaked during middle, consistent with chlorophyll a concentrations. Total N uptake rate was significantly lower (p = 0.003) under ambient temperature-lower salinity condition (28^ºC-31) than the others. This indicates that lowering of salinity in coastal regions due to excessive rainfall in the future may affect the N uptake potential of the phytoplankton, which may change the regional C and N budget.

Fabrication and characterization of chicken feather keratin/polysaccharides blended polymer coated nonwoven dressing materials for wound healing applications

In this research work, three kinds of nonwoven wound dressings were developed from chicken feather keratin (CFK-NW), keratin‑sodium alginate (CFK-SA-NW) and keratin-chitosan (CFK-CS-NW) and characterized using FTIR and SEM. The physical characteristics such as air permeability, thickness and areal density test results revealed the suitability of fabricated materials for wound dressing applications. CFK-SA-NW and CFK-CS-NW indicated a positive antibacterial effect against Gram's positive Staphylococcus aureus and Gram's negative Klebsiella pneumoniae and Escherichia coli bacteria with the zone of inhibition enhanced over >2.0 cm. Moreover, the biomedical potentials of dressing materials has been investigated by cell viability and cytotoxicity tests. Further, the wound healing ability was demonstrated using in vivo model (Albino Wistar rat). The fabricated materials exhibited good support for cell viability and a strong cytocompatibility. Furthermore, the hundred percent wound healing ability of CFK-CS-NW, CFK-SA-NW, CFK-NW and untreated control rats was observed at 15, 17, 21 and 23 days, respectively, Moreover, the wound healing potential of CFK-CS-NW and CFK-SA-NW was found to be better than that of CFK-NW and control group of rats. The outcome of the present study discloses the prospective applications of the developed materials as wound dressing biomaterial.

Distribution of Major and trace elements in Koppunuru area, Guntur district, Andhra Pradesh, India

From koppunuru study area totally 58 samples were collected in 7 different boreholes, minimum depth of 28 m and Maximum depth of 157.7 m. The borehole samples geochemical analysis (major and trace elements) was carried out at Atomic Minerals Directorate for Exploration & Research (AMD), Hyderabad, India. Major and trace element studies have been conducted on the Neoproterozoic Palnad sub-basin Andhra Pradesh, South India, to determine their Geochemistry, Uranium mineralization and provenance characteristics. Geochemically, this sedimentary basin has a different litho – unit like as gritty quartzite, conglomerate, and Shale. This study area mainly dominated by Uranium deposited and radioactive elements are predominately deposit. Strong positive correlation between Uranium and Lead (r = 0.887) suggested radiogenic nature of this system.

Bandgap scaling and negative differential resistance behavior of zigzag phosphorene antidot nanoribbons (ZPANRs)

This work examines the prospect of phosphorene antidot nanoribbons (PANRs) using the density functional based tight binding (DFTB) method. Horizontally perforated PANRs with both armchair (A) and zigzag (Z) configurations were considered for electrical simulations. Our simulation results found that the APANRs cannot be scaled down with nanoribbon width, whereas ZPANRs can be scaled easily. Bandgap scaling in terms of ribbon width, length and antidot number was thoroughly analyzed for ZPANRs. In the end, a two-terminal device was constructed and transmission analysis was performed using the non-equilibrium Green's function (NEGF) methodology. A negative differential resistance (NDR) region appeared in the current-voltage characteristics of the ZPANRs, which paved a pathway for nano-device application.

Atomically Resolved Electronic States and Correlated Magnetic Order at Termination Engineered Complex Oxide Heterointerfaces

We map electronic states, band gaps, and interface-bound charges at termination-engineered BiFeO₃/La_0.7Sr_0.3MnO₃ interfaces using atomically resolved cross-sectional scanning tunneling microscopy. We identify a delicate interplay of different correlated physical effects and relate these to the ferroelectric and magnetic interface properties tuned by engineering the atomic layer stacking sequence at the interfaces. This study highlights the importance of a direct atomically resolved access to electronic interface states for understanding the intriguing interface properties in complex oxides.