A ‘duplex cobalt coated’ near-nanostructured WC-17wt.%Co powder was used to produce nanostructured coatings. The tribological performance of this coating was compared with a commercial WC-17wt.%Co ...microstructured coating using a pin-on-plate method (ASTM G133-05 standard) with a data acquisition software to perform a real time analysis of the sliding wear process. The wear rate was studied using loads from 10 to 60
N and for various sliding distances. The metallurgical analysis of the coatings showed that the duplex Co coated powder could be sprayed to produce dense coating. Furthermore, the near-nanostructured coating showed better fracture toughness values and this corresponded to a difference in wear mechanism between the two types of coatings. The greater “plasticity” in the near-nanostructured coating was recorded as microgrooves in the wear tracks and, in comparison, brittle fracture was observed in the wear tracks produced on the microstructured coating.
► Development of a novel Duplex Co-coated HVOF near-nanostructured WC-17wt.% coating. ► Dense coating formation contributing to low internal porosity in the novel coating. ► Improved fracture toughness and microhardness of near-nanostructured coating. ► Pin-on-plate sliding wear test under different loads and wear conditions. ► Two different wear mechanisms in near-nanostructured and microstructured coatings.
Wetlands are potential sites for mosquito breeding and are thus important in the context of public health. The use of chemical and microbial controls is constrained in wetlands in view of their ...potential impact on the diverse biota. Biological control using generalist aquatic insects can be effective, provided a preference for mosquito larvae is exhibited. The mosquito prey preferences of water bugs and larvae of odonate species were evaluated using chironomid larvae, fish fingerlings and tadpoles as alternative prey. Manly's selectivity (αᵢ) values with 95% confidence intervals (CIs) were estimated to judge prey preference patterns. Multivariate analysis of variance (manova) and standardized canonical coefficients were used to test the effects of density on prey selectivity. The αᵢ values indicated a significant preference (P < 0.05) in all of the insect predators tested for mosquito larvae over the alternative prey as a density‐dependent function. On a comparative scale, chironomid larvae had the highest impact as alternative prey. In a multiple‐prey experiment, predators showed a similar pattern of preference for mosquito larvae over alternative prey, reflecting a significant (P < 0.05) niche overlap. The results suggest that, in a laboratory setting, these insect predators can effectively reduce mosquito density in the presence of multiple alternative prey.
Menstruation is a normal physiological process occurring every month throughout the reproductive age of the females. However, significant variation in menstrual pattern is observed among adolescents. ...The objective of this study was to determine menstrual pattern among adolescent girls of Pokhara Valley.
A cross sectional study was conducted in seven schools of Pokhara Valley. A total of 260 adolescent girls were included in the study. Girls were requested to complete questionnaire containing 19 items. Selected girls voluntarily agreed to answer questionnaire under the supervision of the researcher and then the data was analyzed.
Mean age of the girls was 14.0 ± 1.3 years. Mean age at menarche was 12.2 ± 0.9 years. The mean cycle length of the subjects was 34.8 ± 11.8 days. It was observed that as many as 167(64.2%) girls had irregular menstrual cycle and significant association was found between regularity of menstruation and ethnicity. Seven (2.7%) girls had a menstrual cycle length shorter than 21 days, 60(23.1%) had cycle longer than 35 days and 193(74.2%) had a normal cycle length between 21 and 35 days. Majority 231(88.8%) had normal duration of menstruation. Dysmenorrhoea was reported by more than half of the girls and significant association was found between severity of dysmenorrhoea with school absenteeism and treatment needed.
Dysmenorrhoea was the most common menstrual problem among adolescent girls. Girls' school attendance was affected due to menstrual pain. Girls with severe dysmenorrhea needed medical treatment. Irregular menstruation was reported by more than half of the girls and significant association was found with the ethnicity.
Abstract
Globalization has led to massive rise in cross border trade. Increase in E-commerce business has contributed to this too. As a result, a continuous and complex logistics network of supply ...chains operate across the globe round the clock. Transportation of goods is the most essential activity of this network. Statistics reveals that approximately 90 percent of world’s goods are transported via sea route. This intense network of shipment poses a huge threat to marine ecosystem in numerous ways. One of the most dangerous events for marine ecosystem is oil spill. Oil spill from vessels and pipelines are a major reason behind mortality of marine wildlife. The present work focuses on developing a cost-effective sustainable solution for mitigation of marine oil spill. It was found from existing literature that peels of some fruits have substantial oil absorbing capacity. This fact was experimentally validated and a reduced scale prototype was designed aiming for the task of deployment in case of oil spill in marine waters. The experimental results show that the proposed model floats on water after absorbing oil up to its saturation value. It was also found that through appropriate mechanical setup, absorbed oil can be extracted for reuse or processing.
Moyna of Purba Medinipur district is widely known as an aquaculture hub of West Bengal, India. Though very good production is achievable from this fish culture system, management practices are ...inappropriate, which could create the sustainability problem of this culture system. The present study was thus undertaken for the estimation of plankton population, water quality, carbon footprint and carbon sequestration of this intensive aquaculture practices. Information on spawn to fry, fry to fingerlings and grow-out culture were collected through the structured questionnaire from the fish farmers. The plankton density, primary productivity, carbon footprint and carbon sequestration were analyzed using standard procedures. The phytoplankton, zooplankton and primary productivity were maximum at the stocking period and minimum during the middle of culture period. The lowest feed conversion ratio (FCR) was noticed with the minimum amount of feed applied in the pond. The CO
2
-e emission ranged from 0.56 to 4.89 kg CO
2
-e/kg fish (av. 2.13) for the production levels of 5.0 to 10.7 t/ha/yr. The pond water developed salinity and ammonium-N increased from 0.01 to 0.50 mg/l. The ponds with high feed loading (28 to 32 t/ha/yr) had the highest average sediment accumulation rate (11.0 ± 3.0 cm/yr) and carbon sequestration (704 ± 30 g C/m
2
/yr).
Faecal contamination of groundwater from pit latrines is widely perceived as a major threat to the safety of drinking water for several billion people in rural and peri-urban areas worldwide. On the ...floodplains of the Ganges-Brahmaputra-Meghna delta in Bangladesh, we constructed latrines and monitored piezometer nests monthly for two years. We detected faecal coliforms (FC) in 3.3–23.3% of samples at four sites. We differentiate a near-field, characterised by high concentrations and frequent, persistent and contiguous contamination in all directions, and a far-field characterised by rare, impersistent, discontinuous low-level detections in variable directions. Far-field FC concentrations at four sites exceeded 0 and 10 cfu/100 ml in 2.4–9.6% and 0.2–2.3% of sampling events respectively. The lesser contamination of in-situ groundwater compared to water at the point-of-collection from domestic wells, which itself is less contaminated than at the point-of-consumption, demonstrates the importance of recontamination in the well-pump system. We present a conceptual model comprising four sub-pathways: the latrine-aquifer interface (near-field); groundwater flowing from latrine to well (far-field); the well-pump system; and post-collection handling and storage. Applying a hypothetical dose-response model suggests that 1–2% of the diarrhoeal disease burden from drinking water is derived from the aquifer, 29% from the well-pump system, and 70% from post-collection handling. The important implications are (i) that leakage from pit latrines is a minor contributor to faecal contamination of drinking water in alluvial-deltaic terrains; (ii) fears of increased groundwater pollution should not constrain expanding latrine coverage, and (iii) that more attention should be given to reducing contamination around the well-head.
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•Severe faecal pollution of groundwater from latrines is limited to a near-field.•In the far-field, faecal pollution is low-level, discontinuous and impersistent.•Latrine pollution of groundwater is a minor contributor to diarrhoeal disease.•Expanding latrine coverage will have little impact on groundwater used for drinking.
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This paper systematically examines the thermomechanical properties and phase transformation behaviour of slightly Ni-rich Ni–Ti biomedical shape memory wires containing homogeneously ...distributed nanoscale precipitates induced by stress-assisted ageing. In contrast to previous studies, particular attention is paid to the role of precipitates in impeding twin boundary movement (TBM) and its underlying mechanisms. The size and volume fraction of precipitates are altered by changing the ageing time. The martensitic transformation temperatures increase with prolonged ageing time, whereas the R-phase transformation temperature remains relatively unchanged. The stress–strain behaviour in different phase regions during both cooling and heating is comprehensively examined, and the underlying mechanisms for the temperature- and thermal-history-dependent behaviour are elucidated with the help of the established stress–temperature phase diagram. The effect of precipitates on TBM is explored by mechanical testing at 133K. It is revealed that the critical stress for TBM (σcr) increases with increasing ageing time. There is a considerable increase of 104MPa in σcr in the sample aged at 773K for 120min under 70MPa compared with the solution-treated sample, owing to the presence of precipitates. The Orowan strengthening model of twinning dislocations is insufficient to account for this increase in σcr. The back stress generation is the predominant mechanism for the interactions between precipitates and twin boundaries during TBM that give rise to the increase in σcr. Such results provide new insights into the thermomechanical properties of precipitate containing Ni–Ti biomedical shape memory wires, which are instructive for developing high-performance biomedical shape memory alloys.
► Prevention of WC decarburization during spraying by use of Duplex Co coated powder. ► Impingement slurry jet test for erosion–corrosion behaviour of WC–17Co coatings. ► Microgalvanic cell, crevice ...corrosion site formation in microcrystalline coating. ► Absence of oxide scale fracture in near-nanocrystalline coating. ► Erosion–corrosion synergism in the coatings dominated by two distinct mechanisms.
Cermet based coatings are being increasingly used to combat erosion–corrosion in oil sands pipelines and pumps where the degradation is caused by a slurry mix of sand particles and aqueous solution. This research assesses the erosion–corrosion resistance of cermet composite coatings obtained by HVOF thermal spraying of microcrystalline and ‘duplex cobalt coated’ near-nanocrystalline WC–17Co feedstock powders. Electrochemical measurements, surface characterization, and the extent of weight loss were studied through an impingement jet system. Results suggest that the erosion–corrosion mechanism in the coatings was dominated by pure erosion in the microcrystalline coating and corrosion-enhanced erosion in the near-nanocrystalline coating.
In this paper, the wear behaviour of nanostructured cermet coatings composed of two types of dispersed nanosized ceramic particles (Al2O3 and TiO2) in nickel matrix produced by co-electrodeposition ...is investigated. The effects of particle concentration in electrolyte solutions and current density on wear performance of coatings were studied using sliding wear tests. The increases in the wear depth versus sliding distance as a function of loads were recorded and wear track were investigated using SEM and microhardness. The analysis of element maps showed that the volume fraction of each type of dispersed particle in the nickel matrix corresponded to the concentration of that particle in the electrolyte solutions. The increase in hardness of cermet coatings compared to pure form of nickel was explained by the “rule of mixture” and was correlated to grain refining and dispersion strengthening mechanisms which can take place during electrodeposition. The results showed that the coatings with higher Al2O3 in the matrix provide greater hardness and as a result, an improved wear performance against sliding wear can be expected. In addition, changes in wear rate and wear mechanisms during the course of sliding were observed and correlated to the effects of surface strain hardening and fatigue wear under different applied loads.
•A modified co-electrodeposition method is used to develop novel cermet coatings•Dual-oxide (Al2O3-TiO2) nano ceramics in Ni matrix composite system is developed•Microhardness and sliding wear behaviour of the coatings are investigated•Wear mechanisms found in the coatings are affected by the type of ceramic particles•Strain and wear fatigue are correlated to coatings' performance under various loads
We have developed a 3‐D shear velocity (Vsv) model of Precambrian terrains of South India with a lateral resolution of 55 km to a depth of 250 km by inversion of fundamental mode Rayleigh wave phase ...velocity dispersion data in the period of 30–140s, combined with a well‐constrained crustal velocity model from an earlier study. The dispersion data were computed from 748 earthquakes recorded at 85 homogeneously distributed seismographs. Our velocity model shows 150–200 km thick lithosphere in most of the Archean Dharwar craton where Vsv is >4.7 km/s in the depth of 50–100 km and progressively decreases to 4.6 km/s at 120–150 km followed by a constant velocity of 4.5 km/s beyond 150–200 km depth. It correlates well with the results of the petrological studies of kimberlite xenoliths. An extraordinary high shear velocity (up to 4.8 km/s) and thick lithosphere (150 km) are observed beneath the Proterozoic Carbonatite complex, located at the south‐eastern edge of the Dharwar craton. We infer compositional modification of lower lithosphere at the south‐western margin of the Dharwar craton and lithospheric erosion at the Granulite terrain both possibly due to interaction with the Marion mantle plume at ∼90 Ma. The region is underlain by a 2%–3% lower velocity channel at ∼180–220 km depth in the asthenosphere, uncorrelated with the overlying lithosphere, possibly due to relative motion between them. It may be attributed to deep Earth‐processes such as asthenospheric upwelling.
Plain Language Summary
South India, comprising the Archean Dharwar craton, Proterozoic Cuddapah basin and Neoproterozoic‐Cambrian Granulite Terrain holds a continuous record of continent evolution since 3.36 Ga. As part of the Scalavia supercontinent ca. 2.6–2.2 Ga, it experienced multiple Wilson cycles of terrain amalgamation and rifting, most recent being India‐Madagascar separation at 90 Ma due to interaction with the Marion mantle plume. It is an excellent site to study craton formation/evolution, effect of mantle plumes on Archean/Proterozoic lithosphere and Proterozoic evolution of metamorphic terrains. We have mapped 3‐D shear wave velocity structure of South India using surface wave imaging at much higher resolution than prior studies. We observe the presence of thick (150–200 km) continental lithosphere below a significant part of Dharwar craton with similar lithosphere beneath Granulite terrain and Proterozoic Carbonatite complex. Due to interaction with the Marion mantle plume, the lower lithosphere below south‐western Dharwar craton is compositionally modified in contrast to thermal erosion of the same below most of Granulite terrain. We observe two opposite surface manifestations of the modified/thinned lithosphere; low heat flow (32 mW/m2), low topography (500 m) at south‐western Dhawar craton and higher surface heat flow (45 mW/m2), higher elevation (over 1,000 m) at the Granulite terrain.
Key Points
High‐resolution 3D shear velocity model of the upper mantle of South India
Signatures of preserved and modified Archean lithospheres of Dharwar craton
Thick craton like lithosphere below Proterozoic carbonatite complex
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