Physics of the Earth and Planetary Interiors, 2012
Single-crystal elasticity of stishovite was examined using a new experimental technique and an em... more Single-crystal elasticity of stishovite was examined using a new experimental technique and an empirical macroscopic model. Employing high-frequency resonant ultrasound spectroscopy, single-crystal elastic constants of stishovite were determined: C 11 = 443(3), C 33 = 781(4), C 12 = 193(2), C 23 = 199(2), C 44 = 256(2), and C 33 = 316(2) GPa. The frequency range of the resonant ultrasound spectroscopy techniques was 6-20 MHz, which is much lower than the $10 GHz range of the Brillouin scattering technique. Of the elastic constants, the shear elastic constants C 44 and C 66 are consistent with the average value of the previously mentioned Brillouin scattering. Conversely, the four elastic constants, C 11 , C 33 , C 12 , and C 23 , slightly deviate outside the range of previous Brillouin scattering results. The present results, except those for C 12 , are consistent with recent lattice dynamic analysis of inelastic X-ray scattering data. The adiabatic bulk modulus was calculated as 298 GPa, which is smaller and more consistent with the result of compression experiments than any other Brillouin scattering results (301-312 GPa). The present result shows greater P-wave velocity anisotropy (24.7%) than any preceding work. To understand the unique elastic properties of stishovite, the Gingham check model was proposed and examined. The result shows that the octahedron of 6-coordinated Si in stishovite crystal has stiffness comparable to that of diamond.
The chronic kidney disease of unknown etiology (CKDu) prevalent in certain regions of Sri Lanka p... more The chronic kidney disease of unknown etiology (CKDu) prevalent in certain regions of Sri Lanka poses a serious threat to human health. Previous epidemiological studies focused on the search of causative agents for CKDu etiology from the viewpoint of groundwater composition, but how CKDu prevalence affected the groundwater microbial composition, especially the antibiotic resistome, has never been illuminated. This study investigated the response of microbial community and antibiotic resistome to CKDu prevalence in the groundwater through the high throughput sequencing and qPCR (HT-qPCR), respectively. Results showed that CKDu prevalence significantly influenced the distribution of antibiotic resistome and microbial community composition. The mexF dominated in all the groundwater samples and could be considered as an intrinsic ARG, and the β-lactamase cphA was specially enriched and closely associated with the antibiotics used for CKDu patients. The Acinetobacter was a potential human pathogen common in the groundwater of CKDu affected regions, while CKDu prevalence specially enriched the Aeromonas. Statistical analysis indicated that CKDu prevalence impacted antibiotic resistome through the microbial community as a whole, and MGEs contributed to the occurrence of mexF, while the enrichment of cphA could be attributed to the increase of Aeromonas.
Drinking water is largely from groundwater in Sri Lanka, so quality management is of great concer... more Drinking water is largely from groundwater in Sri Lanka, so quality management is of great concern. In order to achieve the 6th goal of United Nations (UN) Sustainable Development Goals (SDG), more efforts are being undertaken to secure drinking water quality. In this paper, the current status, challenges and opportunities of groundwater quality management and improvement in Sri Lanka were reviewed and discussed, based on previous studies. There are Ca-HCO3 type, Ca–Mg-HCO3 type and Na–SO4–Cl type groundwater dominated in the wet zone, intermediate and the dry zone, respectively. Elevated levels of hardness, fluoride, DOC, and alkalinity, and salinity are reported in the groundwater in the dry zone controlled by geology and arid climate. Although groundwater in some regions contain significant levels of nitrates, arsenic, cadmium and lead, the majority remain at acceptable levels for drinking purposes. As for treatment technologies, existing membrane-based drinking water treatment t...
A magnetotelluric survey was conducted to map the lateral variation of resistivity with depth alo... more A magnetotelluric survey was conducted to map the lateral variation of resistivity with depth along ~9 km profiles across seven known hot springs of Sri Lanka for locating thermal waters within deep faults or hot dry rock that would help geothermal energy development. Data show three regions with resistivity less than 10 Ωm, two the vicinity of Kinniya hot spring, at depths ~1.5 and 2 km, and one at Kapurella at ~500 m. All three regions have 2D cross sections of a few hundred square metres. Three more regions with lower resistivity, 10 - 100 Ωm, were located at depths beyond 10 km at Padiyatalawa, Mahaoya and Kinniya. Their cross sectional extent is limited to a few square kilometres. It is known that optimum geothermal sources at the spring sites can be lateral to the MT traverses, and that 3D MT surveys should be undertaken to locate the most favourable geothermal reservoirs. Though the larger detected sources are outside the economic depth of exploitation, results show their ass...
Reverse osmosis (RO) drinking water stations have been introduced to provide safe drinking water ... more Reverse osmosis (RO) drinking water stations have been introduced to provide safe drinking water for areas with prevailing chronic kidney disease with unknown (CKDu) etiology in the dry zone of Sri Lanka. In this investigation, RO drinking water stations established by community-based organizations (CBO) in the North Central Province (NCP) were examined. Water samples were collected from source, permeate, and concentrate in each station to determine water quality and performance. Furthermore, the operators of the systems were interviewed to evaluate operational and maintenance practices to identify major issues related to the RO systems. Results show that the majority (>93%) of RO systems had higher salt rejection rates (>92%), while water recovery varied from 19.4% to 64%. The removal efficiencies of hardness and alkalinity were averaged at 95.8% and 86.6%, respectively. Most dominant ions such as Ca2+, Mg2+, K+, Na+, Ba2+, Sr2+ Cl−, F−, and SO42− showed higher rejections at ...
Installation of decentralized water-treatment plants is an ideal option to supply safe drinking w... more Installation of decentralized water-treatment plants is an ideal option to supply safe drinking water for rural communities. Presently in Sri Lanka, over 3.6 million villagers face acute water-quality problems, and chronic kidney disease of unknown etiology (CKDu) is also prevalent among this community. Most of the drinking water in these villages is unpalatable due to high hardness and salinity. As an interim measure, reverse-osmosis (RO) water-treatment plants are introduced to provide safe water. However, due to deficient electrolytes, RO-treated water tastes unpleasant to some consumers; hence, people refuse it after prolonged use. The operation, maintenance, and management of RO plants are other major problems. Aimed at providing safe drinking water to the rural sector in a cost-effective manner, in this study, we fabricated an automated drinking-water purification system based on nanofiltration (NF) membrane technology, which can remove divalent cations, dissolved organic carb...
International Journal of Environmental Research and Public Health
This study investigated the water quality of the groundwater that was collected from the chronic ... more This study investigated the water quality of the groundwater that was collected from the chronic kidney disease of unknown etiology (CKDu) prevailing areas in the dry zone of Sri Lanka to assess its suitability for drinking purposes, and for the first time a Water Quality Index (WQI) with emphasis on proposing appropriate drinking water treatment method was developed. A total of 88 groundwater samples were collected in dry (December 2016) and wet (May 2017) seasons; high concentrations of water hardness, fluoride, salinity, dissolved organic carbon (DOC), and the general alkaline nature of water were the main issues that were observed for disease incidence. The chemical weathering of the underlying bedrock, followed by ion exchange and precipitation processes, primarily controlled groundwater geochemistry. During the 1985–2017 period, the variations of the annual rainfall and temperature were minimal, which suggests no evidence for major climatic changes within the study areas. Almo...
This study investigated the water quality of the groundwater that was collected from the chronic ... more This study investigated the water quality of the groundwater that was collected from the chronic kidney disease of unknown etiology (CKDu) prevailing areas in the dry zone of Sri Lanka to assess its suitability for drinking purposes, and for the first time a Water Quality Index (WQI) with emphasis on proposing appropriate drinking water treatment method was developed. A total of 88 groundwater samples were collected in dry (December 2016) and wet (May 2017) seasons; high concentrations of water hardness, fluoride, salinity, dissolved organic carbon (DOC), and the general alkaline nature of water were the main issues that were observed for disease incidence. The chemical weathering of the underlying bedrock, followed by ion exchange and precipitation processes, primarily controlled groundwater geochemistry. During the 1985–2017 period, the variations of the annual rainfall and temperature were minimal, which suggests no evidence for major climatic changes within the study areas. Almo...
The chronic kidney disease of unknown etiology (CKDu) prevalent in certain regions of Sri Lanka p... more The chronic kidney disease of unknown etiology (CKDu) prevalent in certain regions of Sri Lanka poses a serious threat to human health. Previous epidemiological studies focused on the search of causative agents for CKDu etiology from the viewpoint of groundwater composition, but how CKDu prevalence affected the groundwater microbial composition, especially the antibiotic resistome, has never been illuminated. This study investigated the response of microbial community and antibiotic resistome to CKDu prevalence in the groundwater through the high throughput sequencing and qPCR (HT-qPCR), respectively. Results showed that CKDu prevalence significantly influenced the distribution of antibiotic resistome and microbial community composition. The mexF dominated in all the groundwater samples and could be considered as an intrinsic ARG, and the β-lactamase cphA was specially enriched and closely associated with the antibiotics used for CKDu patients. The Acinetobacter was a potential human pathogen common in the groundwater of CKDu affected regions, while CKDu prevalence specially enriched the Aeromonas. Statistical analysis indicated that CKDu prevalence impacted antibiotic resistome through the microbial community as a whole, and MGEs contributed to the occurrence of mexF, while the enrichment of cphA could be attributed to the increase of Aeromonas.
Elastic properties of minerals plays an indispensable role in the studies of Earth's interio... more Elastic properties of minerals plays an indispensable role in the studies of Earth's interior as it is essential for interpretation of seismic velocity structure of the Earth, due to its feasibility of comparison with the seismological observations. And it also provides information on structure, bonding, and the nature of phase transitions in minerals. Resonant Ultrasound Spectroscopy (RUS) has been one of the leading methods of determining elastic constants of materials by measuring number of natural vibration modes. Owing to developments of high frequency RUS up to 50 MHz (HRUS), it emerge as a powerful technique in study of high pressure phases of mantel minerals in which samples are restricted to be sub millimeter size. In this study stishovite was selected due to exceptional interest on it as a prototype phase of the lower mantle silicates, because it exhibits silicon in six-fold coordination. Large single crystals (up to 0.8x0.8x1.5mm) of stishovite were synthesized at 12...
A temperature of 3500°C was generated using a diamond resistance heater in a large-volume Kawai-t... more A temperature of 3500°C was generated using a diamond resistance heater in a large-volume Kawai-type high-pressure apparatus. Re and LaCrO 3 have conventionally been used for heaters in high-pressure studies but they cannot generate temperatures higher than 2900°C and make in situ x-ray observations difficult due to their high x-ray absorption. Using a boron-doped diamond heater overcomes these problems and achieves stable temperature generation for pressure over 10 GPa. The heater starting material is a cold-compressed mixture of graphite with boron used to avoid the manufacturing difficulties due to the extreme hardness of diamond. The diamond heater was synthesized in situ from the boron-graphite mixture at temperature of 1600Ϯ 100°C and pressure of 20 GPa. By using the proposed technique, we have employed the diamond heater for high-temperature generation in a large-volume high-pressure apparatus. Achievement of temperatures above 3000°C allows us to measure the melting points of the important constituents in earth's mantle ͑MgSiO 3 , SiO 2 , and Al 2 O 3 ͒ and core ͑Fe and Ni͒ at extremely high pressures.
Physics of the Earth and Planetary Interiors, 2012
Single-crystal elasticity of stishovite was examined using a new experimental technique and an em... more Single-crystal elasticity of stishovite was examined using a new experimental technique and an empirical macroscopic model. Employing high-frequency resonant ultrasound spectroscopy, single-crystal elastic constants of stishovite were determined: C 11 = 443(3), C 33 = 781(4), C 12 = 193(2), C 23 = 199(2), C 44 = 256(2), and C 33 = 316(2) GPa. The frequency range of the resonant ultrasound spectroscopy techniques was 6-20 MHz, which is much lower than the $10 GHz range of the Brillouin scattering technique. Of the elastic constants, the shear elastic constants C 44 and C 66 are consistent with the average value of the previously mentioned Brillouin scattering. Conversely, the four elastic constants, C 11 , C 33 , C 12 , and C 23 , slightly deviate outside the range of previous Brillouin scattering results. The present results, except those for C 12 , are consistent with recent lattice dynamic analysis of inelastic X-ray scattering data. The adiabatic bulk modulus was calculated as 298 GPa, which is smaller and more consistent with the result of compression experiments than any other Brillouin scattering results (301-312 GPa). The present result shows greater P-wave velocity anisotropy (24.7%) than any preceding work. To understand the unique elastic properties of stishovite, the Gingham check model was proposed and examined. The result shows that the octahedron of 6-coordinated Si in stishovite crystal has stiffness comparable to that of diamond.
The chronic kidney disease of unknown etiology (CKDu) prevalent in certain regions of Sri Lanka p... more The chronic kidney disease of unknown etiology (CKDu) prevalent in certain regions of Sri Lanka poses a serious threat to human health. Previous epidemiological studies focused on the search of causative agents for CKDu etiology from the viewpoint of groundwater composition, but how CKDu prevalence affected the groundwater microbial composition, especially the antibiotic resistome, has never been illuminated. This study investigated the response of microbial community and antibiotic resistome to CKDu prevalence in the groundwater through the high throughput sequencing and qPCR (HT-qPCR), respectively. Results showed that CKDu prevalence significantly influenced the distribution of antibiotic resistome and microbial community composition. The mexF dominated in all the groundwater samples and could be considered as an intrinsic ARG, and the β-lactamase cphA was specially enriched and closely associated with the antibiotics used for CKDu patients. The Acinetobacter was a potential human pathogen common in the groundwater of CKDu affected regions, while CKDu prevalence specially enriched the Aeromonas. Statistical analysis indicated that CKDu prevalence impacted antibiotic resistome through the microbial community as a whole, and MGEs contributed to the occurrence of mexF, while the enrichment of cphA could be attributed to the increase of Aeromonas.
Drinking water is largely from groundwater in Sri Lanka, so quality management is of great concer... more Drinking water is largely from groundwater in Sri Lanka, so quality management is of great concern. In order to achieve the 6th goal of United Nations (UN) Sustainable Development Goals (SDG), more efforts are being undertaken to secure drinking water quality. In this paper, the current status, challenges and opportunities of groundwater quality management and improvement in Sri Lanka were reviewed and discussed, based on previous studies. There are Ca-HCO3 type, Ca–Mg-HCO3 type and Na–SO4–Cl type groundwater dominated in the wet zone, intermediate and the dry zone, respectively. Elevated levels of hardness, fluoride, DOC, and alkalinity, and salinity are reported in the groundwater in the dry zone controlled by geology and arid climate. Although groundwater in some regions contain significant levels of nitrates, arsenic, cadmium and lead, the majority remain at acceptable levels for drinking purposes. As for treatment technologies, existing membrane-based drinking water treatment t...
A magnetotelluric survey was conducted to map the lateral variation of resistivity with depth alo... more A magnetotelluric survey was conducted to map the lateral variation of resistivity with depth along ~9 km profiles across seven known hot springs of Sri Lanka for locating thermal waters within deep faults or hot dry rock that would help geothermal energy development. Data show three regions with resistivity less than 10 Ωm, two the vicinity of Kinniya hot spring, at depths ~1.5 and 2 km, and one at Kapurella at ~500 m. All three regions have 2D cross sections of a few hundred square metres. Three more regions with lower resistivity, 10 - 100 Ωm, were located at depths beyond 10 km at Padiyatalawa, Mahaoya and Kinniya. Their cross sectional extent is limited to a few square kilometres. It is known that optimum geothermal sources at the spring sites can be lateral to the MT traverses, and that 3D MT surveys should be undertaken to locate the most favourable geothermal reservoirs. Though the larger detected sources are outside the economic depth of exploitation, results show their ass...
Reverse osmosis (RO) drinking water stations have been introduced to provide safe drinking water ... more Reverse osmosis (RO) drinking water stations have been introduced to provide safe drinking water for areas with prevailing chronic kidney disease with unknown (CKDu) etiology in the dry zone of Sri Lanka. In this investigation, RO drinking water stations established by community-based organizations (CBO) in the North Central Province (NCP) were examined. Water samples were collected from source, permeate, and concentrate in each station to determine water quality and performance. Furthermore, the operators of the systems were interviewed to evaluate operational and maintenance practices to identify major issues related to the RO systems. Results show that the majority (>93%) of RO systems had higher salt rejection rates (>92%), while water recovery varied from 19.4% to 64%. The removal efficiencies of hardness and alkalinity were averaged at 95.8% and 86.6%, respectively. Most dominant ions such as Ca2+, Mg2+, K+, Na+, Ba2+, Sr2+ Cl−, F−, and SO42− showed higher rejections at ...
Installation of decentralized water-treatment plants is an ideal option to supply safe drinking w... more Installation of decentralized water-treatment plants is an ideal option to supply safe drinking water for rural communities. Presently in Sri Lanka, over 3.6 million villagers face acute water-quality problems, and chronic kidney disease of unknown etiology (CKDu) is also prevalent among this community. Most of the drinking water in these villages is unpalatable due to high hardness and salinity. As an interim measure, reverse-osmosis (RO) water-treatment plants are introduced to provide safe water. However, due to deficient electrolytes, RO-treated water tastes unpleasant to some consumers; hence, people refuse it after prolonged use. The operation, maintenance, and management of RO plants are other major problems. Aimed at providing safe drinking water to the rural sector in a cost-effective manner, in this study, we fabricated an automated drinking-water purification system based on nanofiltration (NF) membrane technology, which can remove divalent cations, dissolved organic carb...
International Journal of Environmental Research and Public Health
This study investigated the water quality of the groundwater that was collected from the chronic ... more This study investigated the water quality of the groundwater that was collected from the chronic kidney disease of unknown etiology (CKDu) prevailing areas in the dry zone of Sri Lanka to assess its suitability for drinking purposes, and for the first time a Water Quality Index (WQI) with emphasis on proposing appropriate drinking water treatment method was developed. A total of 88 groundwater samples were collected in dry (December 2016) and wet (May 2017) seasons; high concentrations of water hardness, fluoride, salinity, dissolved organic carbon (DOC), and the general alkaline nature of water were the main issues that were observed for disease incidence. The chemical weathering of the underlying bedrock, followed by ion exchange and precipitation processes, primarily controlled groundwater geochemistry. During the 1985–2017 period, the variations of the annual rainfall and temperature were minimal, which suggests no evidence for major climatic changes within the study areas. Almo...
This study investigated the water quality of the groundwater that was collected from the chronic ... more This study investigated the water quality of the groundwater that was collected from the chronic kidney disease of unknown etiology (CKDu) prevailing areas in the dry zone of Sri Lanka to assess its suitability for drinking purposes, and for the first time a Water Quality Index (WQI) with emphasis on proposing appropriate drinking water treatment method was developed. A total of 88 groundwater samples were collected in dry (December 2016) and wet (May 2017) seasons; high concentrations of water hardness, fluoride, salinity, dissolved organic carbon (DOC), and the general alkaline nature of water were the main issues that were observed for disease incidence. The chemical weathering of the underlying bedrock, followed by ion exchange and precipitation processes, primarily controlled groundwater geochemistry. During the 1985–2017 period, the variations of the annual rainfall and temperature were minimal, which suggests no evidence for major climatic changes within the study areas. Almo...
The chronic kidney disease of unknown etiology (CKDu) prevalent in certain regions of Sri Lanka p... more The chronic kidney disease of unknown etiology (CKDu) prevalent in certain regions of Sri Lanka poses a serious threat to human health. Previous epidemiological studies focused on the search of causative agents for CKDu etiology from the viewpoint of groundwater composition, but how CKDu prevalence affected the groundwater microbial composition, especially the antibiotic resistome, has never been illuminated. This study investigated the response of microbial community and antibiotic resistome to CKDu prevalence in the groundwater through the high throughput sequencing and qPCR (HT-qPCR), respectively. Results showed that CKDu prevalence significantly influenced the distribution of antibiotic resistome and microbial community composition. The mexF dominated in all the groundwater samples and could be considered as an intrinsic ARG, and the β-lactamase cphA was specially enriched and closely associated with the antibiotics used for CKDu patients. The Acinetobacter was a potential human pathogen common in the groundwater of CKDu affected regions, while CKDu prevalence specially enriched the Aeromonas. Statistical analysis indicated that CKDu prevalence impacted antibiotic resistome through the microbial community as a whole, and MGEs contributed to the occurrence of mexF, while the enrichment of cphA could be attributed to the increase of Aeromonas.
Elastic properties of minerals plays an indispensable role in the studies of Earth's interio... more Elastic properties of minerals plays an indispensable role in the studies of Earth's interior as it is essential for interpretation of seismic velocity structure of the Earth, due to its feasibility of comparison with the seismological observations. And it also provides information on structure, bonding, and the nature of phase transitions in minerals. Resonant Ultrasound Spectroscopy (RUS) has been one of the leading methods of determining elastic constants of materials by measuring number of natural vibration modes. Owing to developments of high frequency RUS up to 50 MHz (HRUS), it emerge as a powerful technique in study of high pressure phases of mantel minerals in which samples are restricted to be sub millimeter size. In this study stishovite was selected due to exceptional interest on it as a prototype phase of the lower mantle silicates, because it exhibits silicon in six-fold coordination. Large single crystals (up to 0.8x0.8x1.5mm) of stishovite were synthesized at 12...
A temperature of 3500°C was generated using a diamond resistance heater in a large-volume Kawai-t... more A temperature of 3500°C was generated using a diamond resistance heater in a large-volume Kawai-type high-pressure apparatus. Re and LaCrO 3 have conventionally been used for heaters in high-pressure studies but they cannot generate temperatures higher than 2900°C and make in situ x-ray observations difficult due to their high x-ray absorption. Using a boron-doped diamond heater overcomes these problems and achieves stable temperature generation for pressure over 10 GPa. The heater starting material is a cold-compressed mixture of graphite with boron used to avoid the manufacturing difficulties due to the extreme hardness of diamond. The diamond heater was synthesized in situ from the boron-graphite mixture at temperature of 1600Ϯ 100°C and pressure of 20 GPa. By using the proposed technique, we have employed the diamond heater for high-temperature generation in a large-volume high-pressure apparatus. Achievement of temperatures above 3000°C allows us to measure the melting points of the important constituents in earth's mantle ͑MgSiO 3 , SiO 2 , and Al 2 O 3 ͒ and core ͑Fe and Ni͒ at extremely high pressures.
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Papers by Titus Cooray
threat to human health. Previous epidemiological studies focused on the search of causative agents for CKDu
etiology from the viewpoint of groundwater composition, but how CKDu prevalence affected the groundwater
microbial composition, especially the antibiotic resistome, has never been illuminated. This study investigated
the response of microbial community and antibiotic resistome to CKDu prevalence in the groundwater through
the high throughput sequencing and qPCR (HT-qPCR), respectively. Results showed that CKDu prevalence
significantly influenced the distribution of antibiotic resistome and microbial community composition. The mexF
dominated in all the groundwater samples and could be considered as an intrinsic ARG, and the β-lactamase cphA
was specially enriched and closely associated with the antibiotics used for CKDu patients. The Acinetobacter was a
potential human pathogen common in the groundwater of CKDu affected regions, while CKDu prevalence
specially enriched the Aeromonas. Statistical analysis indicated that CKDu prevalence impacted antibiotic
resistome through the microbial community as a whole, and MGEs contributed to the occurrence of mexF, while
the enrichment of cphA could be attributed to the increase of Aeromonas.
threat to human health. Previous epidemiological studies focused on the search of causative agents for CKDu
etiology from the viewpoint of groundwater composition, but how CKDu prevalence affected the groundwater
microbial composition, especially the antibiotic resistome, has never been illuminated. This study investigated
the response of microbial community and antibiotic resistome to CKDu prevalence in the groundwater through
the high throughput sequencing and qPCR (HT-qPCR), respectively. Results showed that CKDu prevalence
significantly influenced the distribution of antibiotic resistome and microbial community composition. The mexF
dominated in all the groundwater samples and could be considered as an intrinsic ARG, and the β-lactamase cphA
was specially enriched and closely associated with the antibiotics used for CKDu patients. The Acinetobacter was a
potential human pathogen common in the groundwater of CKDu affected regions, while CKDu prevalence
specially enriched the Aeromonas. Statistical analysis indicated that CKDu prevalence impacted antibiotic
resistome through the microbial community as a whole, and MGEs contributed to the occurrence of mexF, while
the enrichment of cphA could be attributed to the increase of Aeromonas.