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Achieving environmental sustainability by improving the urban microclimate is a key principle in mitigating the urban heat island (UHI) effect. This study aimed to (a) investigate the outdoor thermal comfort by establishing Heat Index (HI) values to identify thermal hot spots and (b) model green infrastructure possibilities to alleviate UHI in Colombo urban metropolitan in Sri Lanka using ENVImet climate model. Daytime temperature and humidity values of 14 urban locations were collected to determine HI to recognize thermal urban hotspots in Colombo area. A pretested comprehensive random-stratified questionnaire survey has been conducted to appraise the thermal discernment of the general public. ENVImet microclimate model was accompanied to test the temperature reduction levels in different bioclimatic green infrastructure scenarios [Two belts (R1), three belts (R2), four belts (R3), five belts (R4)] in the selected study site. Five sites (Borella, Colombo Fort, Maradana, Wellawaththa, Liberty junction) were identified as thermal hotspots in Colombo metropolitan. HI values were fluctuated within 33.82–40.35 °C range and the highest average day time HI value was observed at Maradana (40.35 °C) and the lowest HI was observed at Thummulla (33.82 °C). Survey results revealed that 89.3% people are affected with thermal uncomfortability and 5% were affected with heat-related skin diseases. Inserting trees into curbsides (R4) reduced temperature remarkably by 2.07 °C in the urban metropolitan. Therefore, the proposed green infrastructure scenario has proved to be the most suitable way to improve the thermal comfort conditions of urban environment, as it can reduce the UHI effects.

Soil contamination by heavy metals creates adverse impacts on human health, agricultural production, and ecological functions in the local ecosystem. In this context, serpentinite weathering is an event that can produce heavy metal (Cr, Ni, and Co) anomalies in the local soil profiles. Therefore, weathered rock (WR), soil, and plant samples were analyzed to evaluate the soil contamination and its probable risk to the plants and human health in Ginigalpelessa serpentinite outcrop in Sri Lanka. The results revealed that soil is severely contaminated with Cr, Ni, and Co, which was confirmed by corresponding high index of geoaccumulation (Igeo), enrichment factor (EF), contamination factor (CF), and degree of contamination (Cdeg) values. According to the individual potential ecological risk factor (Er) values and calculated potential ecological risk index (PERI) value, Cr, Ni, and Co showed a very high degree of ecological risk to biological communities in the area. According to the human health assessment on non-carcinogenic scenarios, total exposure hazard index (HIt) values for adults implied that both residential and agricultural scenarios (2>HIt>1) possess obvious non-carcinogenic effects for adults. Similarly, HIt values for children were calculated as 7.36 and 7.08 for residential and recreational scenarios, respectively. These values suggested that children were highly vulnerable to possess obvious non-carcinogenic effects than adults. Moreover, a questionnaire survey was carried out to evaluate the health problems in the area. The results showed that skin rashes and kidney disease contribute to 82% and 12% of the total health issues, respectively. In this regard, children were identified as the main victims (contribute for 54% of patients), and people above the age of 45 were the second victimized age category (contribute for 38% of patients). Based on the above results, present study also provided useful insights to execute a phytoremediation approach via colonization of heavy metal hyperaccumulators in identified risk-prone critical areas as a solution to the people in this area who have suffered through no fault of their own.

Meethotamulla open dump (MOD) of Sri Lanka that has received about 290,000 metric tons of mixed MSW annually collapsed on 14th April 2017 with massive devastation. An integrated approach was attempted to control further collapse with the deployment of drone-assisted and stand-alone instrumentation. The collapsed dump was analyzed for attributes, including contours, heights, wetness, temperature levels, tension cracks, landfill gases, fire, explosion, and asphyxiation hazards with 24-h surveillance after one day of the collapse. The mode of MOD failure was implicated to be deep-seated (rotational) slope failure. A short-term plan, consisting of 12 activities was prepared and successfully implemented. The activities of the short-term plan were carried out at the dumpsite until the water level fluctuations5 cm, inundation of the toe area receded completely, the horizontal displacement of surface markers20 mm, lower explosive levels of CH

Exploring new phase-change materials is instrumental in the progression of electronic memory devices. Ag2Te with its reversible structural phase transition, and in the form of nanowires, has become an apt candidate for potential use in nanoscale memory devices. Here, we report a study on the temperature- or electrically-driven phase change properties of crystalline Ag2Te nanowires. We first demonstrate that this structural phase change can be achieved via heating up the nanowires, which results in a sharp drop in conductance. Then we show that a DC voltage (

Electron-electron interactions (EEIs) in 2D van der Waals (vdW) nanostructures is a topic of high current interest, with implications in both fundamental physics and nanoelectronics. In this Rapid Communication, we report the observation of a negative parabolic magnetoresistance (MR) in the multilayer 2D semiconductor InSe beyond the low-field weak localization/antilocalization regime, and provide evidence for the EEI origin of this MR behavior. Further, we analyze this negative parabolic MR and other observed quantum transport signatures of EEIs (temperature-dependent conductance and Hall coefficient) within the framework of Fermi-liquid theory and extract the gate voltage tunable Fermi-liquid parameter ${F}_{0}^{\ensuremath{\sigma}}$ which quantifies the electron spin-exchange interaction strength. This work opens up different directions for investigations of EEI effects in the electron transport of 2D vdW nanostructures.

Global sea-level changes have been a major topic among scientists. Sea-level changes are not globally uniform. Reconstruction of paleo sea-level changes and monitoring of variations in regional sea-level are important to (i) evaluate future sea-level changes, and (ii) predict risk assessment. In this study, we examined sea-level inundation during the middle Holocene highstands based on paleo sea-level indicators along the south and southwest coasts of Sri Lanka. Besides, future sea-level inundation was predicted considering the calculated sea-level trends based on tidal gauge data and high-resolution surface elevation data. Light Detection and Ranging (LiDAR) is one of the most accurate optical remote sensing methods currently available to obtain high-resolution land surface elevation data. Therefore, in this study, Digital Elevation Models (DEMs) were prepared using LiDAR data for estimating the risk assessment in coastal lowlands. Tide gauge data of Colombo in Sri Lanka (from 2006 to 2017), Gan in the Maldives (from 1995 to 2017), and Hulhule in the Maldives (from 1995 to 2017) showed that sea-level has increased with a rate of 0.288 ± 0.118, 0.234 ± 0.025, and 0.368 ± 0.027 mm/month, respectively. DEMs based on LiDAR data suggested that south and southwest coasts are a risk of future sea-level inundation (height = 0.1–0.2 m during next 50 years and about 0.7 m in height during next 200 years, and distance = about 3.5–15.0 m from the present sea-level towards the inland). Consequently, it is important to consider future sea-level changes in disaster management and mitigation activities along the south and southwest coasts of Sri Lanka.

The Drude model is one of the most fundamental models used to understand the electronic carrier transport in materials, including recently discovered topological materials. Here, we present a magneto-transport study revealing the non-Drude transport behavior in a heterostructure of topological crystalline insulator (TCI) SnTe and band insulator PbTe which exhibits a nonsaturating linear magneto-resistance (MR) effect, a novel phenomenon widely observed in topological materials with gapless dispersion. It is shown that in the van der Pauw geometry in which the longitudinal and transverse magneto-resistances are measured to extract the magneto-conductivity, the two-band Drude model is not sufficient to self-consistently describe both the longitudinal and transverse magneto-conductivities. Furthermore, in the Corbino geometry, which directly measures the longitudinal magneto-conductivity σ xx( B) for a straightforward comparison with the Drude model, the MR, 1/σ xx( B), still reveals a large linear MR effect, in direct discrepancy with the Drude model. While shining further light on the multiple-carrier transport in TCI, this study highlights an unusual magneto-transport character of topological materials that challenges the standard Drude picture of electron transport.

SERS spectra excited at 785 nm of the bacteria Chlamydia trahomatis (elementary bodies, EB) and Neisseria gonorrheoae, the causative pathogens for the two most common sexually transmitted diseases (STD), chlamydia and gonorrhea, respectively, are reported. Although both are Gram-negative bacteria, the SERS signatures of C. trachomatis and N. gonorrheoae are completely different. N. gonorrheoae SERS spectra are due to the starvation induced nucleotide metabolites adenine and guanine, and the surface associated co-enzyme nicotinamide adenine dinucleotide and are very similar on Au and Ag although the spectrum appears more rapidly on Ag. The C. trachomatis SERS spectrum is dominated by the vibrational features of cell surface proteins. While features attributable to specific residues and the amide backbone characterize the C. trachomatis spectrum on Ag, the corresponding SERS spectrum on Au substrates displays vibrational characteristics of aggregated proteins. The prospects for the development of a SERS based platform for rapid (

A chromatography-free, asymmetric synthesis of the C2-symmetric P-chiral diphosphine t-Bu-SMS-Phos was developed using a chiral auxiliary-based approach in five steps from the chiral auxiliary in 36% overall yield. Separtion and recovery of the auxiliary were achieved with good yield (97%) to enable recycling of the chiral auxiliary. An air-stable crystalline form of the final ligand was identified to enable isolation of the final ligand by crystallization to avoid chromatography. This synthetic route was applied to prepare up to 4 kg of the final ligand. The utility of this material was demonstrated in the asymmetric hydrogenation of trifluoromethyl vinyl acetate at 0.1 mol % Rh loading to access a surrogate for the pharmaceutically relavent chiral trifluoroisopropanol fragment in excellent yield and enantiomeric excess (98.6%).

Stimulated Raman scattering (SRS) microscopy allows for high-speed label-free chemical imaging of biomedical systems. The imaging sensitivity of SRS microscopy is limited to ~10 mM for endogenous biomolecules. Electronic pre-resonant SRS allows detection of sub-micromolar chromophores. However, label-free SRS detection of single biomolecules having extremely small Raman cross-sections (~10−30 cm2 sr−1) remains unreachable. Here, we demonstrate plasmon-enhanced stimulated Raman scattering (PESRS) microscopy with single-molecule detection sensitivity. Incorporating pico-Joule laser excitation, background subtraction, and a denoising algorithm, we obtain robust single-pixel SRS spectra exhibiting single-molecule events, verified by using two isotopologues of adenine and further confirmed by digital blinking and bleaching in the temporal domain. To demonstrate the capability of PESRS for biological applications, we utilize PESRS to map adenine released from bacteria due to starvation stress. PESRS microscopy holds the promise for ultrasensitive detection and rapid mapping of molecular events in chemical and biomedical systems., Stimulated Raman scattering (SRS) microscopy enables label-free chemical imaging at high speed, but has been limited by low sensitivity. Here, the authors demonstrate plasmon-enhanced SRS microscopy and achieve single molecule detection sensitivity.

Atomically-thin 2D materials have opened up new opportunities in the past decade in realizing novel electronic device concepts, owing to their unusual electronic properties. The recent progress made in the aspect of utilizing additional degrees of freedom of the electrons such as spin and valley suggests that 2D materials have a significant potential in replacing current electronic-charge-based semiconductor technology with spintronics and valleytronics. For spintronics, spin-orbit coupling plays a key role in manipulating the electrons' spin degree of freedom to encode and process information, and there are a host of recent studies exploring this facet of 2D materials. We review the recent advances in tuning spin-orbit coupling of 2D materials which are of notable importance to the progression of spintronics.

Synthesis of large-area hexagonal boron nitride (h-BN) films for two-dimensional (2D) electronic applications typically requires high temperatures (∼1000 °C) and catalytic metal substrates which necessitate transfer. Here, analogous to plasma-enhanced chemical vapor deposition, a nonthermal plasma is employed to create energetic and chemically reactive states such as atomic hydrogen and convert a molecular precursor film to h-BN at temperatures as low as 500 °C directly on metal-free substrates-a process we term plasma-enhanced chemical film conversion (PECFC). Films containing ammonia borane as a precursor are prepared by a variety of solution processing methods including spray deposition, spin coating, and inkjet printing and reacted in a cold-wall reactor with a planar dielectric barrier discharge operated at atmospheric pressure in a background of argon or a mixture of argon and hydrogen. Systematic characterization of the converted h-BN films by micro-Raman spectroscopy shows that the minimum temperature for nucleation on silicon-based substrates can be decreased from 800 to 500 °C by the addition of a plasma. Furthermore, the crystalline domain size, as reflected by the full width at half-maximum, increased by more than 3 times. To demonstrate the potential of the h-BN films as a gate dielectric in 2D electronic devices, molybdenum disulfide field effect transistors were fabricated, and the field effect mobility was found to be improved by up to 4 times over silicon dioxide. Overall, PECFC allows h-BN films to be grown at lower temperatures and with improved crystallinity than CVD, directly on substrates suitable for electronic device fabrication.

The first beach nourishment project in Sri Lanka was carried out in 2012 over a 1.8-km stretch in the Uswetakeiyawa area by the Coast Conservation Department. About 300,000 m3 of offshore sand in the Indian Ocean was pumped using a dredging vessel for the nourishment. Three breakwaters were constructed nearly 1 year after the beach nourishment. This research was carried out to analyze the performance of the above soft and hard engineering coastal protection strategies. Beach profiles and grain size data were collected over a 1-year period. This monitoring program covered entire seasonal cycles with a comparison to the pre-nourishment beach profiles. Satellite images were also analyzed spanning much larger time periods from 2010 to 2015. Beach profile data indicated both sand accretion and erosion in the nourished area. However, the variations of sand deposition showed enhancement of the sand volume. Satellite images indicated the irregular changes of the beach profiles after the construction of breakwaters. The field observations and calculated relationships of the breakwaters demonstrated either subdued salient or gap erosion at the specific locations of the nourished beach. In this study, no permanent or periodic tombolo formations were observed at Uswetakeiyawa beach. The lack of sediment supply from longshore currents and the high-energy cross-shore monsoon currents can enhance coastal erosion related to the presence of the breakwater.

Beach sediments in Sri Lanka contain industrial-grade heavy mineral occurrences. Samples of both offshore and onshore sediments were collected to examine the provenance, mineralogy and geochemical compositions of the heavy mineral occurrences. Coastal morphodynamic changes along the coastline of Sri Lanka were analyzed using the time-series satellite images. These coastal morphodynamic changes were used to identify the prominent directions of monsoon-influenced longshore currents, coastal sediment accretion and depositional trends and their relationships to the provenance of the heavy minerals. Results show the concentrations of detrital ilmenite, zircon, garnet, monazite, and rutile vary in the onshore and offshore sediments. The heavy mineral potential of the northeastern coast is high (average contents of about 45–50% in the Verugal deposit, 70–85% in the Pulmoddai deposit, and 3.5–5.0% in offshore samples stretching from Nilaveli to Kokkilai), compared to sediments in southwest (average content about 10% in onshore sediments and 2% in offshore sediments from the mouth of the Gin River). Therefore, no economic-grade heavy mineral placers were identified in the offshore environments. The high concentrations of heavy minerals in beach sediments and low concentrations in offshore sediments suggest operation of a panning system in the surf zone to form enriched placer deposits. Major and trace element compositions of beach sediments show marked enrichments of TiO2, Fe2O3, La, Ce, Zr, Cr, Nb, Th and V compared to average Upper Continental Crust (UCC) values. Analysis of prominent coastal longshore transport patterns identifies bidirectional sediment transport in the northeast coast of Sri Lanka. In the southwestern coast, two transport directions occur with anti-clockwise transport from Galle to Hambantota, and clockwise transport from Hikkaduwa to Wadduwa. The heavy minerals in the placers were mainly derived from Precambrian metamorphic rocks, and transported to the coast through the river systems of Sri Lanka.

Rare earth elements (REEs), a group of 17 elements comprises 15 lanthanides, scandium and yttrium, are largely attracting the world’s attention due to their importance in a wide variety of advanced technological applications. Global REEs production is mainly sourced from resources, such as carbonatites, alkaline igneous rocks, placers, laterites, and ion-adsorption clays. Recently, REE demand has been escalating, especially due to the REE applications in renewable energy and defense sectors, expecting a worldwide shortage of REE supply in the future. Therefore, REEs have been widely accepted as strategic elements in the world, which compels to prospect for new and alternative REE resources. In this context, Sri Lanka has a favorable geological setting which implies the presence of REE mineralization. Previous geochemical studies in Sri Lanka have reported significant concentrations of REEs in different geological formations and mineral resources. Accordingly, Pulmoddai and other beach placer deposits, Eppawala carbonatite, alluvial placer deposits, and pegmatites have been identified as potential REE resources in Sri Lanka. Monazite, apatite, allanite, and zircon are the primary rare earth (RE) minerals found in the preceding resources. The Pulmoddai mineral sand deposit is considered as the most potential REE resource in the island, which is enriched in monazite containing more than 61% of light rare earth elements (LREEs). Similarly, Eppawala carbonatite contains high concentrations of LREEs. However, despite their significant REE enrichments, to date, no attempt has been made to recover these REE prospects, which essentially conceals their potential of catering for both local and global REE supply chains.

Rare earth elements (REEs) including fifteen lanthanides, yttrium and scandium are found in more than 250 minerals, worldwide. REEs are used in various high-tech applications across various industries, such as electrical and electronics, automotive, renewable energy, medical and defence. Therefore, the demand for REEs in the global market is increasing day by day due to the surging demand from various sectors, such as emerging economies, green technology and R&D sectors. Rare earth (RE) deposits are classified on the basis of their genetic associations, mineralogy and form of occurrences. The Bayan Obo, Mountain Pass, Mount Weld and China’s ion adsorption clays are the major RE deposits/mines in the world to date and their genesis, chronology and mineralogy are discussed in this review. In addition, there are other RE deposits, which are currently being mined or in the feasibility or exploration stages. Most of the RE resources, production, processing and supply are concentrated in the Asia-Pacific region. In this regard, China holds the dominancy in the RE industry by producing more than 90% of the current rare earth requirements. Thus, REEs are used as a powerful tool by China in trade wars against other countries, especially against USA in 2019. However, overwhelming challenges in conventional RE explorations and mining make secondary RE resources, such as electric and electronic waste (e-waste) and mine tailings as promising resources in the future. Due to the supply risk of REEs and the monopoly of the REEs market, REEs recycling is currently considered as an effective method to alleviate market fluctuations. However, economical and sustainable processing techniques are yet to be established to exploit REEs via recycling. Moreover, there are growing ecological concerns along with social resistance towards the RE industry. To overcome these issues, the RE industry needs to be assessed to maintain long-term social sustainability by fostering the United Nations sustainable development goals (SDGs).

Manipulating the electron spin with the aid of spin-orbit coupling (SOC) is an indispensable element of spintronics. Electrostatically gating a material with strong SOC results in an effective magnetic field which can in turn be used to govern the electron spin. In this work, we report the existence and electrostatic tunability of Rashba SOC in multilayer InSe. We observed a gate-voltage-tuned crossover from weak localization (WL) to weak antilocalization (WAL) effect in quantum transport studies of InSe, which suggests an increasing SOC strength. Quantitative analyses of magneto-transport studies and energy band diagram calculations provide strong evidence for the predominance of Rashba SOC in electrostatically gated InSe. Furthermore, we attribute the tendency of the SOC strength to saturate at high gate voltages to the increased electronic density of states-induced saturation of the electric field experienced by the electrons in the InSe layer. This explanation of nonlinear gate voltage control of Rashba SOC can be generalized to other electrostatically gated semiconductor nanomaterials in which a similar tendency of spin-orbit length saturation was observed (e.g. nanowire field effect transistors), and is thus of broad implications in spintronics. Identifying and controlling the Rashba SOC in InSe may serve pivotally in devising III-VI semiconductor-based spintronic devices in the future., 7 pages, 5 figures

This paper presents the design of a neural network to determine the categories of Sleep Apnea (SA) or apneic events using Composite Multiscale Sample Entropy (CMSE) as a feature extraction technique. The designed neural network has the ability to process and classify apneic events, maintaining the accuracy levels of apnea scoring of laboratory polysomnography (PSG) which remains the gold standard of sleep monitoring and scoring to date. Additionally, this paper shows the extent to which each individual signal monitored in polysomnography has the ability to independently detect apneic events, which would be useful in the implementation in a portable wearable device.

This review summarizes the use of a surface-enhanced Raman spectroscopy (SERS)-based platform for a number of biomedical analytic applications ranging from infectious disease diagnostics to forensic science. There is an urgent need to develop rapid, sensitive, simple, and reliable method for the identification of pathogens and to meet recognized unmet technological needs in the forensic community. The use of a SERS methodology for the rapid detection and identification of bacterial clinical isolates in urine at minimal clinical levels demonstrates how this optical approach can provide rapid (

Man-made coastal structures directly affect sediment balance and sediment dynamics on the surrounding beaches. The Colombo Harbor Expansion Project has created about 5-km-long breakwater nearly perpendicular to the beach. The present study is focused on quantitatively and qualitatively analyzing the effect of the Colombo Harbor Expansion Project on economically important beaches in and around Colombo city area. In this study, the authors measured monthly variations of beach width, beach profile and the mean grain-size of the sediments at mean sea level for complete annual monsoon cycle. Data were analyzed to establish site-specific erosion vulnerability. Monitoring results show that cumulative beach erosion has increased after the construction of the breakwater (rate = 0.7 m/year from May 2000 to April 2011 and rate = 28.2 m/year from April 2011 to June 2012). In addition, the cumulative and site-specific sand accretion and erosion patterns have a clear relationship with the monsoon seasonality. Beaches were narrower during the stormy southwestern monsoon, whereas beaches were wider during fair weather of northeast monsoon and inter-monsoon periods. In contrast, the constructed breakwater obstructs natural longshore sediment dynamics. For example, a significant amount of sediments from the Kelani-Ganga River were buried in the Colombo Harbor due to alteration of prominent longshore sediments transportation on the western coast of Sri Lanka. Therefore, this study shows enhancement of coastal erosion in the studied southern beaches due to a lack of sediment deposition.

SERS spectra of 12 bacterial strains of urinary tract infection (UTI) clinical isolates grown and enriched from urine are reported. A partial least squares-discriminant analysis (PLS-DA) classification treatment of these SERS spectra results in strain level identification with >95% sensitivity and >99% specificity. The classification model successfully identified the SERS spectra of a urine-cultured strain not used to build this statistical model. Enrichment was accomplished by a filtration and centrifugation protocol. The predetermined drug susceptibility profiles of these clinical isolates thus allowed the SERS methodology to provide appropriate UTI antibiotic information in less than 1 h. Most of this time was used for sample preparation procedures (enrichment and washing) for this proof of principle study. SERS spectra of the enriched bacterial samples are dominated by nucleotide degradation metabolites: adenine, hypoxanthine, xanthine, guanine, uric acid, AMP, and guanosine. Strain-specific specificity is due to the different relative amounts of these purines contributing to the corresponding SERS spectra of these clinical isolates. All measurements were made at the minimal bacterial concentration in urine for UTI diagnosis (105 cfu/mL).

Traditional methods for identifying pathogens in bacteremic patients are slow (24–48+ h). This can lead to physicians making treatment decisions based on an incomplete diagnosis and potentially increasing the patient’s mortality risk. To decrease time to diagnosis, we have developed a novel technology that can recover viable bacteria directly from whole blood and identify them in less than 7 h. Our technology combines a sample preparation process with surface-enhanced Raman spectroscopy (SERS). The sample preparation process enriches viable microorganisms from 10 mL of whole blood into a 200 μL aliquot. After a short incubation period, SERS is used to identify the microorganisms. We further demonstrated that SERS can be used as a broad detection method, as it identified a model set of 17 clinical blood culture isolates and microbial reference strains with 100% identification agreement. By applying the integrated technology of sample preparation and SERS to spiked whole blood samples, we were able to correctly identify both Staphylococcus aureus and Escherichia coli 97% of the time with 97% specificity and 88% sensitivity.

The dominant molecular species contributing to the surface-enhanced Raman spectroscopy (SERS) spectra of bacteria excited at 785 nm are the metabolites of purine degradation: adenine, hypoxanthine, xanthine, guanine, uric acid, and adenosine monophosphate. These molecules result from the starvation response of the bacterial cells in pure water washes following enrichment from nutrient-rich environments. Vibrational shifts due to isotopic labeling, bacterial SERS spectral fitting, SERS and mass spectrometry analysis of bacterial supernatant, SERS spectra of defined bacterial mutants, and the enzymatic substrate dependence of SERS spectra are used to identify these molecular components. The absence or presence of different degradation/salvage enzymes in the known purine metabolism pathways of these organisms plays a central role in determining the bacterial specificity of these purine-base SERS signatures. These results provide the biochemical basis for the development of SERS as a rapid bacterial diagnostic and illustrate how SERS can be applied more generally for metabolic profiling as a probe of cellular activity. Graphical Abstract Bacterial typing by metabolites released under stress.