Dominant Ion Research Articles

Enhanced photoconductivity of embedded SiGe nanoparticles by hydrogenation

We investigate the effect of room-temperature hydrogen-plasma treatment on the photoconductivity of SiGe nanoparticles sandwiched within SiO2 layers. An increase in photocurrent intensity of more than an order magnitude is observed after the hydrogen plasma treatment. The enhancement is attributed to neutralization of dangling bonds at the nanoparticles and to passivation of nonradiative defects in the oxide matrix and at SiGe/matrix interfaces. We find that increasing the partial pressure of hydrogen to pressures where H3+ and H2+ were the dominant ions results in increased photocurrent.

Chemical characterisation of water-soluble ions in atmospheric particulate matter on the east coast of Peninsular Malaysia

Abstract. Air quality on the east coast of Peninsular Malaysia is influenced by local anthropogenic and biogenic emissions as well as marine air masses from the South China Sea and aged emissions transported from highly polluted East Asian regions during the winter monsoon season. An atmospheric observation tower has been constructed on this coastline at the Bachok Marine Research Station. Daily PM2.5 samples were collected from the top of the observation tower over a 3-week period, and ion chromatography was used to make time-resolved measurements of major atmospheric ions present in aerosol. SO42- was found to be the most dominant ion present and on average made up 66 % of the total ion content. Predictions of aerosol pH were made using the ISORROPIA II thermodynamic model, and it was estimated that the aerosol was highly acidic, with pH values ranging from −0.97 to 1.12. A clear difference in aerosol composition was found between continental air masses originating from industrialised regions of East Asia and marine air masses predominantly influenced by the South China Sea. For example, elevated SO42- concentrations and increased Cl− depletion were observed when continental air masses that had passed over highly industrialised regions of East Asia arrived at the measurement site. Correlation analyses of the ionic species and assessment of ratios between different ions provided an insight into common sources and formation pathways of key atmospheric ions, such as SO42-, NH4+ and C2O42-. To our knowledge, time-resolved measurements of water-soluble ions in PM2.5 are virtually non-existent in rural locations on the east coast of Peninsular Malaysia. Overall this dataset contributes towards a better understanding of atmospheric composition in the Maritime Continent, a region of the tropics that is vulnerable to the effects of poor air quality, largely as a result of rapid industrialisation in East Asia.

A global model study of low pressure high density CF4 discharge

We present a revised reaction set for low pressure high density CF4 plasma modelling. A global model (volume averaged) was developed to study a CF4 discharge that includes the neutral species CF4, CF3, CF2, CF, F2, F, and C, the metastable states CF(a4Σ−) and CF2(3B1), the positive ions , , CF+, , F+, and C+, the negative ions , , and F−, and electrons. The main reactions that contribute to the production and loss of each species are pointed out with an emphasis on the radicals CF2, CF and F, the dominant positive ion , and the dominant negative ion F−. We find wall processes to have a significant influence on the discharge. The density of F2 is high due to recombination of F atoms at the walls and the losses of the radicals F, CF, and CF3 are mainly through wall recombination. As the pressure is increased, F− becomes the dominant negative charged species. The discharge is found to be weakly electronegative below ∼10 mTorr and the electronegativity decreases with increased absorbed power.

TRPC5 ion channel permeation promotes weight gain in hypercholesterolaemic mice

Transient Receptor Potential Canonical 5 (TRPC5) is a subunit of a Ca2+-permeable non-selective cationic channel which negatively regulates adiponectin but not leptin in mice fed chow diet. Adiponectin is a major anti-inflammatory mediator and so we hypothesized an effect of TRPC5 on the inflammatory condition of atherosclerosis. Atherosclerosis was studied in aorta of ApoE−/− mice fed western-style diet. Inhibition of TRPC5 ion permeation was achieved by conditional transgenic expression of a dominant negative ion pore mutant of TRPC5 (DNT5). Gene expression analysis in adipose tissue suggested that DNT5 increases transcript expression for adiponectin while decreasing transcript expression of the inflammatory mediator Tnfα and potentially decreasing Il6, Il1β and Ccl2. Despite these differences there was mild or no reduction in plaque coverage in the aorta. Unexpectedly DNT5 caused highly significant reduction in body weight gain and reduced adipocyte size after 6 and 12 weeks of western-style diet. Steatosis and circulating lipids were unaffected but mild effects on regulators of lipogenesis could not be excluded, as indicated by small reductions in the expression of Srebp1c, Acaca, Scd1. The data suggest that TRPC5 ion channel permeation has little or no effect on atherosclerosis or steatosis but an unexpected major effect on weight gain.

Analysis of Pollution Characteristics and Sources of PM2.5 Chemical Components in Chengdu in Winter

Day-night PM2.5 samples were continuously collected in Chengdu from January 1 to 20, 2017, and the concentrations of major chemical components (water-soluble ions and carbonaceous components) were measured in the laboratory. During the observation period, the average mass concentration of PM2.5 was (127.1±59.9) μg·m-3. The mass concentration of water-soluble ions was (56.5±25.7) μg·m-3 and SO42-, NO3-, and NH4+ were the most dominant ions with a concentration of (13.6±5.5), (21.4±12.0), and (13.3±5.7) μg·m-3, respectively, accounting for 85.6% of the water-soluble ions. The average mass concentrations of organic carbon (OC) and elemental carbon (EC) were 34.0 and 6.1 μg·m-3, respectively, accounting for 26.8% and 4.8% of the PM2.5 mass concentration, respectively. The comparison of the average day-night concentration shows that the daytime and nighttime mass concentrations of PM2.5 are (120.4±56.4) and (133.8±64.0) μg·m-3, respectively, and that the nighttime pollution is more serious. The SO42-, NO3-, and NH4+ concentrations are higher during the day than at night, which is related to daytime light, which promotes the formation of secondary ions. The Cl-, K+, OC, and EC concentrations increase significantly, which may be affected by increased emissions from coal and material combustion. Based on the literature review and comparison of the winter chemical composition of PM2.5 in Chengdu in recent years, the SO42- concentration significantly decreases from 50.6 μg·m-3 in 2010 to 13.6 μg·m-3 in 2017. The NO3- concentration changes little; it is maintained at~20 μg·m-3. The analysis of the acid-alkali ion balance shows that PM2.5 in Chengdu is alkaline due to the relative overgrowth of NH4+, which is different from previous partially acidic results. The average value of NO3-/SO42- is 1.57. Mobile sources have a greater impact on the PM2.5 pollution in Chengdu in winter. The correlation coefficients of OC and EC between daytime and nighttime are 0.82 and 0.90, respectively (P<0.01), which indicates that the OC and EC sources are consistent. The SOC estimation shows that the SOC concentrations during the day and night are 8.5 μg·m-3 and 11.9 μg·m-3, respectively, accounting for 28.1% and 30.8% of the OC, respectively. The K+/EC average value is 0.31 and the correlation coefficient between K+ and OC is 0.87 (P<0.01), indicating that biomass combustion has a certain influence on the carbonaceous aerosol in Chengdu in winter. The principal component analysis shows that the winter PM2.5 in Chengdu mainly originates from combustion sources (coal burning, biomass burning, etc.), secondary inorganic sources, and soil and dust sources. The contribution rates are 32.8%, 34.5%, and 21.5%, respectively.

Limnology of shallow lakes of the semi-arid Central Pampa of Argentina

Abstract Aim The Central Pampa of Argentina has three recognized phytogeographic regions that arise due to the decrease in rainfall towards the west. The area has numerous lakes that are mainly temporary, with hydroperiods that relate to climatic cycles, although some of them have changed due to anthropogenic influence. Some of these lakes have been studied with special reference to zooplankton, but information on their physical and chemical aspects is scarce. Consequently, managing and evaluating the anthropogenic effects on these ecosystems is challenging. The objective of this study was to explore the limnological characteristics of lakes in different regions in the Central Pampa that experience different anthropic influences. Methods Ten lakes were sampled seasonally (January, April, July, and October) during 2007. In situ measurements included transparency, pH, temperature, and dissolved oxygen concentration, and 2-L water samples were collected to determine salinity, ion composition, suspended solids, nutrient concentration, and phytoplankton chlorophyll- a concentration. Results Salinity ranged from 0.32-136.72 g L-1, with Na+ being the dominant ion in nine lakes and Cl- and HCO3- predominating in the higher- and lower-salinity lakes respectively. Nutrient concentrations were high (total Kjeldahl nitrogen: 7.97-34.69 mg L-1; total phosphorous: 4.07-14.82 mg L-1), and all lakes were hypertrophic. We determined three lake classes: i) lakes transformed from low-salinity lakes into hypersaline ones through human inactivation of the fluvial system that fed it; ii) mesosaline temporary lakes lacking fish, with low concentrations of chlorophyll-a and influenced by agricultural activities, and iii) subsaline and hyposaline lakes, highly modified by urban sewage, converted in permanent lakes (which allowed fish fauna development) and with reduced water transparency (due to high concentrations of phytoplankton chlorophyll-a). Conclusions The chemical diversity of the studied lakes is low, and their predominance of Na+ and Cl- indicated that evaporation and crystallization control the water chemistry. Additionally, this study showed the consequences of the anthropic impact, which alter water chemical composition, trophic structure and, thus, the ecological characteristics of lakes.

Climatology and Chemistry of Surface Ozone and Aerosol under Alpine Conditions in East Siberia

ABSTRACT We present the results of synchronous observations of the ozone and gaseous impurity concentrations, chemical composition of the aerosol and meteorological parameters with a high temporal resolution (of minutes) at the background site Mondy, which is located in the highland area of East Siberia. We also analyzed the seasonal dynamics exhibited by the ozone, gaseous impurities of sulfur and nitrogen, and ionic composition of the aerosol over the long term (1998–2016). Ozone variability in the boundary layer depended on complicated relief and dynamic processes occurring in the atmosphere. The concentration of ions in the aerosol decreased by 2 times for the period of 2010–2015 compared to the beginning of the new millennium. Furthermore, sulfate, nitrate, chloride, potassium and sodium became the dominant ions in the aerosol. Due to the remote location of the site, the absence of anthropogenic pollution sources and the large series of data with different parameters obtained via on-line monitoring, this site may be regarded as a representative global background site for the vast region of Central Asia.

Hydrogeology of Abuja FCT-Nigeria: A GIS Evaluation

Groundwater has been recognized as playing a very important role in the development of Abuja FCT Nigeria’s capital, as many private and government establishments depend solely on wells for their water needs. Exploitation of groundwater is delicate due to its potency to contamination and difficulty to remediate aquifers. This study is to evaluate the input of the rock formations to the groundwater solute chemistry and groundwater domestic quality using hydrogeochemical tools and physicochemical parameters: pH, EC, Temperature, TDS, Chloro-alkaline indices, Ionic ratios, Gibbs diagrams, Piper diagrams, Durov diagrams and water quality index. From physicochemical parameters: pH ranged from, 4.8 - 7.9; EC, 13.4 - 1634 μS/cm; Temperature, 26℃ - 36.1℃ and TDS, 17.42 - 1094.78 mg/L. The major ions fell below WHO acceptable limits. The sequences of abundance of major ions were, K > Ca2 > Na > Mg2 for cations and Cl-> HCO3->NO3- >SO42- for anions. Borehole depths range from 19.5 - 34.5 m with static water levels between 3 - 12 m.a.m.s.l. Yields were between 3.2 - 7.2 m3/Hr. Ionic ratios show ninety-five (95%) percent of the groundwater chemistry resulting from chemical weathering of rock-forming minerals through the dissolution of the host rock. The Chloro-alkaline indices: CAI1 87.23% are positive indicating exchange of Na and K from water with Mg and Ca of the rocks and 12.77% are negative, indicating reverse softening of groundwater in rocks by infiltrating rainwater while CAI2 85.11% are positive indicating exchange of Na and K from water with Mg and Ca of the rocks and 14.89% are negative, indicating reverse softening of groundwater in rocks by infiltrating rainwater. Thus chloro-alkaline indices indicate the dominance of alkaline earth elements over alkalis in majority of samples due to direct exchange of Ca2 and Mg2 from the aquifer matrix with Na and K from the groundwater. Gibbs diagram revealed groundwater ionic content was as a result of ion exchange from rock-weathering. Piper diagrams give three water types: 75% are CaHCO3, 21.20% are of MgHCO3 and 3.19% are of Na KHCO3 water types respectively. Piper diagrams also give three hydrogeochemical facies in Abuja FCT: 54.25% are of Ca-Mg-Cl-SO4, 42.56% are of Ca-Mg-HCO3 and 3.19% are of Na-K-Cl-SO4 hydrogeochemical facies respectively. Durov plot shows 20.21% are anion discriminate Ca dominant; mixed water and 63.83% had no dominant ion; simple dissolution. Water quality indices (WQI) values were between ？220 - 180, Total hardness (TH) values were between 0 - 519.12. These WQI and TH values indicate that 69.2% and 47.37% of the groundwater respectively are suitable for domestic purpose. The groundwater in Abuja FCT is acidic to slightly alkaline in nature, soft to moderately hard and of low to high salinity. Major processes controlling the water quality are the weathering of the host rock through mineral dis-solution, cation exchange and inverse cation exchange processes. Ion-exchange, simple dissolution and uncommon dissolution processes determined groundwater character.

Spatial distribution of dominant ions in the groundwater in Banyumudal Groundwater Basin, Central Java, Indonesia

Groundwater basin is an area with hydrogeological limits where it is happened all of hydrogeological processes. Banyumudal Groundwater Basin is one of groundwater basin with unique characteristic because of receiving water source from surroundings area, that would influence probably to the water quality. This study was conducted to: (1) know the spatial distribution of dominant ions concentration in the groundwater; (2) analyze surroundings factors that influence the spatial distribution of dominant ions in the groundwater. To realize the objectives, it was carried out the removal of groundwater samples in the observational wells that were determined by purposive sampling. The analyzed elements were Ca2+, Mg2+, Na+, K+, SO42-, HCO3-, CO32-, Cl- and Fe2+ . The concentration of the dominant ions was realized in the form of Stiff Diagram and then was plotted in a map, so that it could be known the distribution. To analyze the process of mixing between the groundwater and water from the other sources with different chemical characteristics, it used the Piper Diagram, whereas to analyze the surroundings effects to the ionic concentration, it was conducted the analysis of quantitative descriptive. The study results showed that the groundwater from the northern part of Banyumudal Groundwater Basin has higher concentration of dominant ions compared with the southern ones. Viewed from each ion, the ionic concentration of Ca2+ and HCO3- are higher than other dominant ions and have more varied values, so that the change of chemical characteristics of the groundwater would tend to be determined by the concentration change of them. Type of rocks is the most influencing factor to the concentration of dominant ions in the study area. Nevertheless, the domestic waste has also little effects related to the sanitary condition in around of samples location of the groundwater.

Numerical Simulation and Parametric Study of Carbon Deposition During Graphene Growth in PECVD System

The aim of the present work is to understand the carbon deposition during graphene growth in plasma enhanced chemical vapor deposition system containing Ar/C2H2/H2 gas mixture and to optimize the process parameters for the enhanced growth of graphene. In this regard, many numerical simulations have been carried out using two-dimensional axis-symmetrical inductively coupled plasma module in COMSOL multi physics 5.2a simulation software. From the simulation outcomes, it is found that the electron density, electron energy density, electric potential, and collisional power losses decrease with an increase in temperature. The number densities of various dominant ions were found to decrease and number densities of dominant neutrals were found to increase with an increase in temperature. During the carbon deposition, the formation of non-uniform horizontal graphene layer has been observed along the substrate and vertically oriented graphene sheet has been observed at the edges of the substrate. It is found that the thickness of horizontal graphene along the substrate and height of vertical graphene at the edges of the substrate increases with an increase in gas temperature. Moreover, the reduction in the carbon deposition on the substrate (growth of parallel graphene) and enhanced growth of vertical graphene sheet have been observed on applying substrate biasing. Our numerical simulation results are in good agreement with existing experimental observations and confirms the adequacy of the computational and simulation approach.

Modeling of Ion Crossover in an All-Vanadium Redox Flow Battery with the Interfacial Effect at Membrane/Electrode Interfaces

In this work, a numerical model is developed to investigate the ion crossover in the vanadium redox flow battery (VRFB). The Donnan effect is considered by introducing an interfacial sub-model at the membrane/electrode interfaces based on the electrochemical potential equilibrium. Using this model, the diffusion and electric field effects on vanadium ions crossover through both the cation- and anion-exchange membranes are quantitively analyzed and the corresponding ion transport mechanisms are explored. The results show that the electric field influences the ions distributions in the membrane thus the transport of ions across the membranes. The properties of ion and membrane are important parameters to determine the electric field induced ion flux. The different dominant transfer ion results in the migration flux and electro-osmotic flux the same directions in the cation-exchange membrane but opposite directions in the anion-exchange membrane, thus a weaker electric field effect for the latter. The net vanadium flux presents the asymmetric characteristic with SOC and current density for both cation- and anion-exchange membranes. Finally, the present work predicts the accumulation of vanadium ions in the positive half-cell for the cation-exchange membrane but an opposite trend for the anion-exchange membrane with cycling.

Chemical and Optical Properties of Atmospheric Aerosols during the Polluted Periods in a Megacity in the Yangtze River Delta, China

ABSTRACT The chemical composition and optical properties of particulate matter (PM) were characterized in an urban-industrial area of Nanjing, China, in January 2015, when heavily polluted periods frequently occurred. Only 30% of the days fulfilled the National Ambient Air Quality Standards of China. The average scattering and absorption coefficients at 532 nm during the polluted periods were 620 ± 320 Mm–1 and 102 ± 57 Mm–1. An increasing relative fraction of the large size PM during the polluted periods can be deduced from the variations of the scattering Angstrom exponent, backscattering ratio, and asymmetry factor. The mean mass concentrations of NO3–, SO42– and NH4+ in PM2.5 during the polluted periods were 32.87 ± 17.76 µg m–3, 23.6 ± 13.2 µg m–3, and 19.4 ± 10.1 µg m–3, respectively. NO3–, SO42– and NH4+ were the dominant water-soluble ions (WSIs) and accounted for 87% of the total ion concentration. Nitrate and organic matter (OM) dominated the aerosol composition during the polluted periods. The averaged organic carbon/elementary carbon ratios during the polluted and the cleaner periods were 3.6 and 4.3, respectively, consistent with a mix of primary emissions and secondary organic aerosol formation. Organic matter and ammonium nitrate (AN) were the dominant species contributing to light extinction during the polluted periods, contributing values of 159 ± 63 Mm–1 and 156 ± 91 Mm–1, respectively.

Highly dispersed ultrasmall NiS2 nanoparticles in porous carbon nanofiber anodes for sodium ion batteries.

Although sodium-ion batteries (SIBs) show attractive advantages over current dominant lithium ion batteries (LIBs), they still face great challenges in addressing the issues of low capacity and poor cycling stability. We herein report the synthesis of a nanohybrid of ultrasmall NiS2 nanoparticles embedded in porous carbon nanofibers (NiS2NP/p-CNF), which is implemented by an electrospinning process accompanied by further sulfide treatment. The highly dispersed NiS2 nanoparticles, coupled with the highly conductive porous nanofiber structure, endow the hybrids with favorable properties and structure for reducing the effects of volume expansion, providing a fast mass transport channel, and facilitating electron transfer. Systematic electrochemical studies verify that NiS2NP/p-CNF, when studied as an SIB anode, exhibits high performance with an excellent specific capacity (500 mA h g-1 at 0.1 A g-1) and a competitive rate capability, maintaining 200 mA h g-1 at 2.0 A g-1, besides a long-term stability for 1000 cycles. The NiS2NP/p-CNF nanofibers provide a huge potential for the development of massive sodium storage.

Assessment of heavy metal contamination in groundwater of Agbor, Ika south l. G. A., delta state, Nigeria

&#x0D; &#x0D; &#x0D; Heavy Metal Contamination of groundwater is an issue of deep concern worldwide and as such the degree to which these metals have contaminated the most valuable fresh water resource “GROUNDWATER” must be summarily understood. 10 Borehole water samples were taken from various parts of Agbor and analysis were carried out for the major anions and cations with Arsenic been the heavy metal of interest. Upon comparison with NIS and WHO standards for drinking water, the results shows that though they were measurable concentration of Arsenic in three locations but they were high enough to pose threat to human health. Nonetheless, the results were subjected to Statistical Analysis using Principal component Analysis (PCA) to standardized data sets. The results gotten was tied to graphical methods, Stiff plot and Piper diagram to obtain the water type as Ca2+-Mg2+-Cl- - SO42- and revealed the dominant ions. PCA revealed that five components control the hydrochemistry of the study area.Ammonium,Nitrate,Phosphate and TDS dominated component 1 which accounted for 41.1%,Chloride, sulphate and EC are parameters in component 2, component 3 hasCalcium, Magnesium and Bicarbonates, component 4 isdominated bypH and component 5 holds potassium and sodium accountable for hydrochemical variation. United States Environmental Protection Agency (US EPA 2012) and EU 1998 Standards were compared with parameters to ascertain the quality of the water for domestic use. pH had a value less than 6.5 for most of the sampled locations and these were out of range of US United States Environmentaal Protection Agency (EPA) and European Union Drinking Water Directives(EU DWD) standards&#x0D; &#x0D; &#x0D;

A Study on the Characteristics of PM1.0 Chemical Components Using a Real-time Aerosol Mass Spectrometer

This study aims to identify the characteristics of oxidation and chemical composition of PM in winter season, 2017 at Incheon area. The mean concentration of air pollutants were 46 ± 22 μg/m3-PM10, 29 ± 18 μg/m3/-PM2.5, 5 ± 3 ppb-SO2, 0.56 ± 0.24 ppm-CO, 21 ± 13 ppb-O3 and 28 ± 17 ppb-NO2, respectively. The dominant ion of the PM1.0 chemical component were organic with 3.2 μg/m3 and nitrate with 1.9 μg/m3. The day and night variation of the PM1.0 chemical components was higher in nighttime than those of daytime. The averaged nitrate oxidation rate (SOR) was 0.06 and sulfate oxidation rate was 0.11 during the field campaign. In the high mass loading period, nitrate oxidation rate (NOR) was up to 0.6 and also the nitrate in PM1.0 was increased. The averaged ratio of NOx/SO2 was 8.7 and nitrate/sulfate was 3.1, respectively. In this results, the nitrate component in PM1.0 was influenced by NOx from the stationary source as power plant and the mobile source around the measurement site.

On the relative roles of the neutral density and photo chemistry on the solar zenith angle variations in the V2 layer characteristics of the Venus ionosphere under different solar activity conditions

Using an in-house developed one dimensional photo-chemical model (1D-PCM), which considers production and loss of 11 ions namely, CO2+, CO+, C+, N2+, N+, He+, O+(2D), O+(2P), O+(4S), O2+ and NO+, characteristics of the V2 layer in the Venus ionosphere has been studied. It is noted that existing ionospheric model for the Venus ionosphere, such as the IonA (Ionization in Atmospheres) model, not only over/under estimate the peak electron density of V2 layer, it also has significant departures from the observations on the solar zenith angle and solar activity control. The IonA model uses VenusGRAM model (Venus Global Reference Atmosphere Model) as input for the neutral density and temperature and considers Venus atmosphere consisting of CO2, O, and N2 molecules only. Further, it oversimplifies the ion chemistry by assuming Venus ionosphere to have O2+ as the only dominant ion species. Using VTS3 model, an empirical model based on measurements from Orbiter Neutral Mass Spectrometer on Pioneer Venus Orbiter (PVO) which considers profiles of six neutrals (CO2, O, CO, He, N, and N2), we modified IonA model, named as IonA-VTS3, to find that it reproduced the altitude of V2 peak electron density (hmV2) quite well. However, the model still lacked in reproducing observed peak V2 electron density (NmV2). The in-house developed one dimensional photo-chemical model (1D-PCM) not only estimated NmV2 accurately, the hmV2 was also reproduced quite well. Comparison of Venera and PVO radio occultation measurements with 1D-PCM and IonA-VTS3 calculations reveals the role of complex chemical reactions in determining the features of peak altitude and density of V2 layer during different solar activity periods. We surmised that differences in the observed and IonA modeled peak V2 layer altitudes were due to the limitations associated with VenusGRAM neutral density model. It shows that variations in the neutral density controls the V2 layer peak density height. 1D-PCM calculations also showed that the complex chemistry including production and loss reactions of 11 ions could reproduce the variations in the peak density of Venusian ionosphere during different solar activity conditions. It suggests that the ion-chemistry has wider control over the peak plasma density in the Venus ionosphere.

Assessment of water quality in and around Jia-Bharali river basin, North Brahmaputra Plain, India, using multivariate statistical technique

The present study envisages the application of multivariate analysis, water utility class and conventional graphical representation to reveal the hidden factor responsible for deterioration of water quality and determine the hydrochemical facies of water sources in Jia-Bharali river basin, North Brahmaputra Plain, India. Fifty groundwater and 35 surface water samples were collected and analyzed for 15 parameters viz pH, TDS, hardness, COD, Ca2+, Mg2+, Na+, K+, Fe, HCO3−, Cl−, SO42−, NO3−, PO43− and F− for a period of 3 hydrological years (2009–2011) in six different seasons (three wet and three dry). The results were evaluated and compared with WHO and BIS water quality standards. Except Fe (> 0.3 mg/L), all parameters were found well within the desirable limit of WHO and BIS for drinking water. Ca2+ and HCO3− were dominant ions among cations and anions. The piper trilinear diagram classified majority of water samples for both seasons fall in the fields of Ca2+–Mg2+–HCO3− water type indicating temporary hardness. Varimax factors extracted by principal component analysis indicates anthropogenic (domestic and agricultural runoff) and geogenic influences on the trace elements. Hierarchical cluster analysis grouped water sources into three statistically significant clusters based on the similarity of water quality characteristics. This study illustrates the usefulness of multivariate statistical techniques for analysis and interpretation of complex datasets, and in water quality assessment, identification of pollution sources/factors and understanding temporal/spatial variations in water quality for effective water quality management.

Structure of alkaline aqueous NaBH4 solutions by X-ray scattering and empirical potential structure refinement

Structure of alkaline aqueous NaBH4 solutions at NaBH4 concentrations of 1.0 to 9.1 mol·dm−3 (almost saturated) as well as a 1.3 mol·dm−3 NaOH solution was studied by X-ray diffraction and Empirical Potential Structure Refinement (EPSR) modelling. In the 1.0 mol dm−3 alkaline NaBH4 solution, Na+ is surrounded by around six water molecules with octahedral geometry. With an increase in NaBH4 concentration, the hydration number of Na+ decreases from 4.8 ± 1.1 at 2.25 mol·dm−3 solution to 2.9 ± 1.3 at 9.1 mol·dm−3 with an almost constant Na+-O (W: H2O) distance of 2.34 Å. The decrease in hydration number for Na+ is compensated by the formation of ion pairs between Na+ and BH4− to ensure an octahedral hydrated geometry for Na+. About 6.0 ± 1.6 water molecules are likely to bond to BH4−via tetrahedral edges or tetrahedral corners without a very specific hydration geometry, giving rise to each hydrogen atom of BH4− bound to 2.3 ± 1.0 water molecules through dihydrogen bonds. The hydration number around BH4− decreases with increasing concentration. BH4− tends to form contact ion pairs with Na+ at the Na-B distances of 3.24 Å and 2.82 Å in tetrahedral-corner-shared and tetrahedral-edge-shared fashions, respectively; the number of Na-B interactions increases from 0.3 ± 0.5 in 1.0 mol·dm−3 (almost negligible) to 2.1 ± 0.9 in 9.0 mol·dm−3. Tetrahedral-edge-shared bidentate ion pair is likely to be the preferred and dominant ion cluster over the wide concentration range. Ion association between the Na+ and BH4− was crosschecked by density function theory (DFT) calculations on [NaBH4(H2O)6] clusters.

Limnological characteristics and rotifer community composition of Northern Mexico Chihuahuan Desert Springs

Desert springs are critical for wildlife and human subsistence, but poorly studied. The springs in the northern Chihuahuan Desert region of Mexico are no exception. While groundwater overexploitation and other anthropogenic activities have endangered these waters, little is known about their water quality or biodiversity. We monitored five springs on a monthly basis for one year, and two others sporadically, to determine their physicochemical characteristics and to study rotifer community composition as an assessment of biodiversity. Seasonal variation in temperature, dissolved oxygen (DO), and conductivity was observed in the five springs. DO was occasionally below the criterion for aquatic life (<4 mg/L) in some springs. Ca2+ (468–775.2 mg/L) was the dominant ion in all springs except Ojo de Santa María where Na+ (180–290 mg/L) dominated. Of 57 rotifer species identified, Lepadella patella (Müller, 1786), Lepadella triptera (Ehrenberg, 1830), and Philodina megalotrocha, Ehrenberg, 1832 were present in most springs. The rotifer community exhibited nestedness among the sites (supported by four null modes, p < 0.05) and was correlated with fall season, DO, and nitrate concentration. This work provides information that will aid in management practices and provide important baseline data on water quality and regional diversity of a major component of the zooplankton.

Wet etching of TiN in 1-D and 2-D confined nano-spaces of FinFET transistors

In the manufacturing of multi-Vt FinFET transistors, the gate material deposited in the nano-spaces left by the removed dummy gate must be etched back in mask-defined wafer areas. Etch conformality is a necessary condition for the control of under-etch at the boundary between areas defined by masking. We studied the feasibility of TiN etching by APM (ammonia peroxide mixture, also known as SC1) in nano-confined volumes representative of FinFET transistors of the 7 nm node and below, namely nanotrenches with 1-D confinement and nanoholes with 2-D confinement. TiN etching was characterized for rate and conformality using different electron microscopy techniques. Etching in closed nanotrenches was conformal, starting and progressing all along the 2-D seam, with a rate that was 38% higher compared to a planar film. Etching in closed nanoholes proved also to be conformal and faster than planar films, but with a delay to open the 1-D seam that seemed to depend strongly on small variations in the hole diameter. However, holes between the fins at the bottom of the removed dummy gate, are not circular and do present 2-D seams that should lend themselves for an easier start of conformal etching as compared to the circular nanoholes used in this study. Finally, to explain the higher etch rate observed in nano-confined features, concentrations of ions in nanoholes were calculated taking the overlap of electrostatic double layers (EDL) into account. With negatively charged TiN walls, as measured by streaming potential on planar films, ammonium was the dominant ion in nanoholes. As no chemical reaction proposed in the literature for TiN etching matched with this finding, we proposed that the formation of ammine complexes, dissolving the formed Ti oxide, was the rate-determining step.