Initial Precipitation Research Articles

Se-doped GeTe4 glasses for far-infrared optical fibers

Differential scanning calorimetry (DSC) and thermomechanical analysis (TMA) were used to study thermokinetic behavior of Ge21SeyTe79−y infrared glasses (for y up to 8 at.% of Se). Glass transition kinetics was described in terms of the Tool-Narayanaswamy-Moynihan model and the relaxation motions were interpreted using Raman spectroscopy data. Both enthalpy and volume relaxation kinetics were found to be uninfluenced by Se addition. On the other hand, DSC crystallization behavior changed significantly with increasing Se content: initial addition of Se partially delays and decelerates both the initial Te precipitation and the consequent volume-located crystallization of GeTe and Te; additional increase of Se content then further delays and separates the volume-located crystallization processes but the initial surface Te precipitation is no longer affected. From this point of view the fine compositional tuning of basic thermal stability of GeTeSe infrared glasses appears meaningless. On the contrary, glass workability window (determined by means of the TMA crystallization experiments) was found to be significantly affected by Se addition, emphasizing the importance of this type of measurements for the glass technology and material science. The 4 at.% Se content was found optimal with respect to fiber-drawing procedure.

Precipitation Behaviour and Mechanical Properties during Short-Term Heat Treatment for Tailor Heat Treated Profiles (THTP) of Aluminium Alloy 6060 T4

Precipitation hardening aluminium alloys are widely used for automotive applications. To enhance the application of aluminium profiles, improved formability is needed. Tailor Heat Treated Profiles (THTP) with locally different material properties attempt to increase formability e.g. in bending processes. Tailoring of local properties is obtained by a local short-term heat treatment, dissolving the initial precipitate state (retrogression) and still allowing subsequent ageing. In the present study, the dissolution and precipitation behaviour of the aluminium alloy EN AW-6060 T4 was investigated during heating with differential scanning calorimetry (DSC). Heating curves from 20 to 600 °C with heating rates of 0.01 up to 5 K/s were recorded. Interrupted heat treatments with different maximum temperatures were performed in a deformation dilatometer. Immediately afterwards, tensile tests were carried out at room temperature. The course of the recorded mechanical properties as a function of the maximum temperature is discussed with regard to the dissolution and precipitation behaviour during heating. Finally, the aging behaviour of the investigated alloy was recorded after different typical short-term heat treatments and is discussed with reference to the DSC‐curves. The correlation of the microstructure and the mechanical properties enables the derivation of optimal parameters for the development of THTP through a local softening.

Microstructures of Randall's plaques and their interfaces with calcium oxalate monohydrate kidney stones reflect underlying mineral precipitation mechanisms.

Randall's plaques (RP) are preferred sites for the formation of calcium oxalate monohydrate (COM) kidney stones. However, although processes of interstitial calcium phosphate (CaP) plaque formation are not well understood, the potential of plaque microstructures as indicators of CaP precipitation conditions received only limited attention. We investigated RP-associated COM stones for structural details of the calcified tissues and microstructural features of plaque-stone interfaces as indicators of the initial processes of stone formation. Significantly increased CaP supersaturation can be expected for interstitial fluid, if reabsorbed ions from the tubular system continuously diffuse into the collagenous connective tissue. Densely packed, fine-grained CaP particles were found in dense textures of basement membranes while larger, laminated particles were scattered in coarse-meshed interstitial tissue, which we propose to be due to differential spatial confinements and restrictions of ion diffusion. Particle morphologies suggest an initial precipitation as metastable amorphous calcium phosphate (ACP). Morphologies and arrangements of first COM crystals at the RP-stone interface ranged from stacked euhedral platelets to skeletal morphologies and even porous, dendritic structures, indicating, in this order, increasing levels of COM supersaturation. Furthermore, these first COM crystals were often coated with CaP. On this basis, we propose that ions from CaP-supersaturated interstitial fluid may diffuse through porous RP into the urine, where a resulting local increase in COM supersaturation could trigger crystal nucleation and, hence, initiate stone formation. Ion-depleted fluid in persistent pores of initial COM layers may get replenished from interstitial fluid, leading to CaP precipitation in porous COM.

LS-SVM data mining analysis: how does biochar influence soil net nitrogen mineralization in the field?

Biochar has been considered as a stable-carbon source for improving soil quality and long-term sequestration of carbon. However, in view of ecological environmental feedback and the tightly coupled system of carbon-nitrogen cycling, further attention has shifted to the effect of biochar on soil net nitrogen mineralization (SNNM). Recently, ecological evaluations of biochar were mostly based on laboratory incubation or pot experiments, ignoring external and uncontrollable natural factors. Therefore, the essential characteristics of local environments were not accurately described. In this paper, a nonlinear stochastic model of SNNM based on least squares support vector machine (LS-SVM) was set up to study the effect of biochar on nitrogen cycling in a field experiment. In order to explore this effect in natural conditions, partial derivative (PaD) sensitivity analysis of LS-SVM was firstly proposed, evaluated by the data from a known equation, and then applied to open the “black-box” stochastic model of SNNM. Comparing with the sensitivity analysis of artificial neural networks (ANNs), the RD values of LS-SVM PaD1 algorithm were almost the same as those of ANNs PaD1 algorithm. However, the RSD values of LS-SVM PaD2 algorithm were closer to the given equation. In the SNNM model, RD values of LS-SVM PaD1 algorithm of initial nitrogen, time, and precipitation were 21, 15, and 14 %, and the biochar RD value was only 0.51 %, implying that biochar did not influence SNNM directly. However, the cumulative RSD of the PaD2 algorithm of biochar with the other factors was 15.05 %, the maximum of the interactions, implying that it could greatly enhance the tendency for SNNM by interacting with other factors. PaD sensitivity analysis of LS-SVM was a stable and reliable data mining method. In the SNNM model, initial nitrogen, time, and precipitation were the main controlling factors of the SNNM model. Biochar did not directly influence SNNM; however, it could greatly enhance the tendency for SNNM by interactions with other factors by decreasing the inhibitory effect of initial nitrogen on SNNM and modifying soil condition to change the effect of other factors on SNNM.

금호강 유입 지천의 비점오염원 유달율 산정에 관한 연구

본 연구에서는 금호강 유역에 유입되는 지천에 대한 모니터링을 통해 강우 및 비강우시 유달부하량을 산정하였다. 또한 해당 유역별 배출부하량을 산정하여 유입 지천들의 비점오염원에 대한 유달율을 산정하였다. 조사지점들의 농도변화 분석 결과는 BOD의 경우 연중 3월에 발생된 초기 강우에 따른 농도가 가장 높게 조사되었고 이후 후속 강우에 따라 연말에 해당하는 12월경에는 농도가 감소하는 경향을 나타내었다. 7월에서 9월 사이 다수의 높은 강우 발생 시 일부 농도가 증가하는 시기도 있었으나 BOD 농도는 감소하는 경향을 나타내었다. T-N 및 T-P의 경우, 연중 강우누적에 따른 농도 변화가 BOD와는 반대의 경향을 나타내었다. 특히 7월과 8월 사이에 높은 농도를 보이고 이후 강우 발생 비율이 낮은 갈수 시 농도가 증가하는 경향을 나타내었다. 조사 유역별 유달율 산정 결과는 자호천의 경우 강우 시 유달율이 BOD 0.91, T-N 1.39, T-P 0.85로 가장 높게 조사되었으며, 청통천의 경우 강우 시 유달율이 BOD 0.19, T-N 0.55, T-P 0.50으로 가장 낮게 조사되었다. In this study, through the monitoring of the tributaries flowing into the Gumho River Basin it was estimated delivery load when the rain and rain will not come. And calculation the delivery ratio and discharged pollution load of nonpoint sources for the inflow of tributaries. Concentration analysis, BOD concentration in the initial precipitation period was investigated highest occurrences in March For. And, in December by rainfall after further concentration tended to decrease. Between July and September, but also increase in concentration in accordance with the occurrence of a large amount of rainfall, BOD concentration decreased. In the case of T-N and T-P, a concentration change in the cumulative rainfall for year it tended opposite of BOD. Show a high concentration between July and August, it tended to increase the concentration at a low occurrence rate since when the dry season. Delivery ratio calculation results, Jahocheon highest delivery ratio was investigated by BOD 0.19, T-N 1.39, T-P 0.85 times in the case of rainfall. Cheongtongcheon was investigated as the lowest delivery ratio BOD 0.19, T-N 0.55, T-P 0.50 during rainfall.

TG-FTIR analysis of co-combustion characteristics of oil shale semi-coke and corn straw

TGA/DSC1 thermogravimetric analyzer and Fourier infrared spectrometric analyzer (FTIR) were used to conduct a series of combustion experiments using oil shale semi-coke, corn straw, and blends of the two. The results showed that the volatile initial precipitation temperature and ignition temperature of mixed samples are much lower than oil shale semi-coke, but it slightly higher than corn straw. The volatile initial precipitation temperature and ignition temperature of the mixed sample are increased with the increase in heating rate. When the heating rate is constant, the combustion process presents the trend to the low temperature; the peak value of the low-temperature section is high and intense release of volatile, thus improved combustion characteristics of the mixtures. Infrared spectral results are that: with increasing proportion of corn straw, A CO/ $$A_{\text{CO}_2}$$ decreases gradually; the utilization rate of mixtures is improved. The value of A CO/ $$A_{\text{CO}_2}$$ is minimum at the heating rate of 20 K min−1, combustion effect of mixtures is best, and the burnout rate is highest. RMS and MR values are used to evaluate the mutual influence of the co-combustion process and the study showed that main effects of the interaction occurred in second, third and fourth stages, the second and third stages are the favorable effects, and the fourth stage is the adverse effect and when the mass ratio of the semi-coke and the corn straw is 7:3, the mutual influence is the largest and the beneficial effects. The model of distributed activation energy is applied to analyze co-combustion kinetics of the blends. The results show that activation energy presents a rising tendency during the impelling of reaction, which is unanimous to the change law of DTG and FTIR curves. The results can provide reference for efficient combustion of oil shale semi-coke and corn straw.

Microstructure characters of Cu/ZnO catalyst precipitated inside microchannel reactor

Cu/ZnO catalyst was prepared by co-precipitation method inside microchannel reactor and characterized by X-Ray diffraction (XRD), thermo gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM). The XRD analysis of precursors demonstrates that, compared with the sample prepared by conventional batch reactor, more Zn2+ are incorporated into malachite structure, which is attributed to the relatively uniform distribution of Cu, Zn elements in initial precipitates caused by the excellent mixing performance of the microchannel reactor. Higher decomposition temperature of carbonate species trapped in the interfaces between CuO and ZnO and higher binding energy of Cu2p3/2 indicate that sample prepared by the new reactor possess a stronger interface interaction, which derives from the more intimate contact between oxide components. This supposition is confirmed by the HRTEM images and the stronger interface interaction in the final reduced catalyst can improve catalytic performance on methanol synthesis.

Vegetative response to water availability on the San Carlos Apache Reservation

On the San Carlos Apache Reservation in east-central Arizona, U.S.A., vegetation types such as ponderosa pine forests, pinyon-juniper woodlands, and grasslands have significant ecological, cultural, and economic value for the Tribe. This value extends beyond the tribal lands and across the Western United States. Vegetation across the Southwestern United States is susceptible to drought conditions and fluctuating water availability. Remotely sensed vegetation indices can be used to measure and monitor spatial and temporal vegetative response to fluctuating water availability conditions. We used the Moderate Resolution Imaging Spectroradiometer (MODIS)-derived Modified Soil Adjusted Vegetation Index II (MSAVI2) to measure the condition of three dominant vegetation types (ponderosa pine forest, woodland, and grassland) in response to two fluctuating environmental variables: precipitation and the Standardized Precipitation Evapotranspiration Index (SPEI). The study period covered 2002 through 2014 and focused on a region within the San Carlos Apache Reservation. We determined that grassland and woodland had a similar moderate to strong, year-round, positive relationship with precipitation as well as with summer SPEI. This suggests that these vegetation types respond negatively to drought conditions and are more susceptible to initial precipitation deficits. Ponderosa pine forest had a comparatively weaker relationship with monthly precipitation and summer SPEI, indicating that it is more buffered against short-term drought conditions. This research highlights the response of multiple, dominant vegetation types to seasonal and inter-annual water availability. This research demonstrates that multi-temporal remote sensing imagery can be an effective tool for the large scale detection of vegetation response to adverse impacts from climate change and support potential management practices such as increased monitoring and management of drought-affected areas. Different vegetation types displayed various responses to water availability, further highlighting the need for individual management plans for forest and woodland, especially considering the projected drier conditions in the Southwest U.S. and other arid or semi-arid regions around the world.

Purification of BaSO4 precipitate contaminated with organic matter for oxygen isotope measurements (δ18 O and Δ17 O).

Sulfate precipitates are often contaminated with nitrates and organic materials (OM), which reduce the precision and accuracy of measurements of δ18 O and Δ17 O values in the sulfate. Although nitrates can be effectively removed using diethylenetriaminepentaacetic acid solution, removing OM from the precipitates is often difficult. One effective approach is to heat powdered precipitates to high temperatures. In this study, the effect of this procedure on the δ18 O and Δ17 O values of BaSO4 precipitate was fully examined. OM-contaminated BaSO4 precipitates and 18 O- and 17 O-labeled purified BaSO4 precipitates were loaded into alumina and gold crucibles and heated at 450°C, 600°C and 800°C for 2h. The nitrogen and carbon contents in the initial and the final BaSO4 were measured using an elemental analyzer. The values of δ18 O and Δ17 O were measured using a temperature conversion/elemental analyzer coupled with an isotope ratio mass spectrometer, and a CO2 laser system coupled with an isotopic ratio mass spectrometer. OM was effectively (88±17%) removed from the BaSO4 precipitates by this treatment, and heating at 800°C had the highest removal efficiency (98%). The differences in δ18 O and Δ17 O values between the final and initial BaSO4 precipitates was -0.6‰ to 0.3‰ (average of -0.1‰) and -0.24‰ to 0.10‰ (average of -0.02‰), respectively. Significant positive relationships between the δ18 O and Δ17 O values of the initial BaSO4 precipitate and those of the high-T-treated aliquots were found, with slopes having mean values of 0.96±0.06 and 1.04±0.01, respectively. The result demonstrates high removal efficiency for OM in BaSO4 precipitates and no significant differences in the oxygen isotopic compositions between high-T treated BaSO4 and initial BaSO4 . This study indicates that the modified high-T treatment (800°C, 2h) is an effective method for purifying BaSO4 precipitated from geological and environmental samples with a high OM content for δ18 O and Δ17 O measurements. Copyright © 2016 John Wiley & Sons, Ltd.

The relationship between latent heating, vertical velocity, and precipitation processes: The impact of aerosols on precipitation in organized deep convective systems.

A high-resolution, two-dimensional cloud-resolving model with spectral-bin microphysics is used to study the impact of aerosols on precipitation processes in both a tropical oceanic and a midlatitude continental squall line with regard to three processes: latent heating (LH), cold pool dynamics and ice microphysics. Evaporative cooling in the lower troposphere is found to enhance rainfall in low cloud condensation nuclei (CCN) concentration scenarios in the developing stages of a midlatitude convective precipitation system. In contrast, the tropical case produced more rainfall under high CCN concentrations. Both cold pools and low-level convergence are stronger for those configurations having enhanced rainfall. Nevertheless, latent heat release is stronger (especially after initial precipitation) in the scenarios having more rainfall in both the tropical and midlatitude environment. Sensitivity tests are performed to examine the impact of ice and evaporative cooling on the relationship between aerosols, LH and precipitation processes. The results show that evaporative cooling is important for cold pool strength and rain enhancement in both cases. However, ice microphysics play a larger role in the midlatitude case compared to the tropical. Detailed analysis of the vertical velocity governing equation shows that temperature buoyancy can enhance updrafts/downdrafts in the middle/lower troposphere in the convective core region; however, the vertical pressure gradient force (PGF) is the same order and acts in the opposite direction. Water loading is small but on the same order as the net PGF-temperature buoyancy forcing. The balance among these terms determines the intensity of convection.

Removal of Heavy Metal Ions by Ferrihydrite: an Opportunity to the Treatment of Acid Mine Drainage

Ferrihydrite is often an initial precipitate resulting from the neutralization of Fe(III) solution, and it seems to be one of the products of acid mine drainage forming reactions. Since having the adsorption properties, ferrihydrite can be effective for the remediation of acid mine drainage. This study prepared fresh ferrihydrite by the rapid hydrolysis of Fe(III) ions and investigates its adsorptive behaviours toward Pb(II), Cu(II), and Zn(II). When the sorption data were presented in plot of percent sorbed versus pH, it was found that sorption is strongly dependent on the solution pH and increasing as expected at higher pH for all metal ions investigated. All the observed metal cation sorption began at pH values below zero point charge (ZPC) of ferrihydrite (pH = 7.8–8.0), and almost all removal are achieved at pH values lower than that related metal hydroxide obtained. Enhanced removal of metal ions, as the pH of the solution and initial metal ion concentration are increased, was attributed to surface precipitation of metal hydroxide. The existence of ferrihydrite and adsorption of metal ions onto surfaces are favouring surface precipitation of metal ions at lower pH values than that for metal ion only. Depending on the pH of the solution and initial metal ion concentration, more than one mechanism such as adsorption by complexation and surface precipitation was responsible for the removal.

Nanoscale self-organization reaction in Cu–Ag alloys subjected to dry sliding and its impact on wear resistance

Two-phase Cu90–Ag10 alloys are subjected to dry-sliding wear using pin-on-disk testing at room temperature with either a bronze or a martensitic stainless steel as counterface material. Thermal annealing prior to wear testing is used to vary the initial Ag-rich precipitate size in the Cu-rich matrix from ≈30 to 260nm. The wear debris and the sub-surface microstructure are characterized by scanning and transmission electron microscopy. For large enough initial precipitate size, wear induces the spontaneous formation of alternating Cu and Ag nanolayers, and this chemical nanolayering correlates with a significant reduction in wear rate. This correlation is analyzed by considering the role of chemical nanolayering on third bodies and on the mechanical properties of the near-surface microstructure.

Coprecipitation of tellurium(IV), tungsten(VI), and lanthanum(III) hydroxides from aqueous solutions

We have investigated the coprecipitation of tellurium(IV), tungsten(VI), and lanthanum(III) hydroxides through the addition of aqueous ammonia to a mixture of tellurium dioxide, lanthanum oxide, and tungstic acid solutions in hydrochloric acid. The effects of initial solution composition and precipitation pH on the composition of the precipitate have been assessed. It has been shown that the composition of the precipitate is essentially identical to that of the starting solution if the relative contents of lanthanum and tungsten in the mixture are within 20 mol % and precipitation is ceased at pH 7.

Thermal behavior of Ge20SeyTe80−y infrared glasses (for y up to 8 at.%)

The Te-rich Ge20SeyTe80−y infrared chalcogenide glasses (for y up to 8 at.%) were studied by means of DSC, XRD, Raman spectroscopy and infrared microscopy. Thorough non-isothermal thermo-kinetic characterization of the glass transition, crystallization and melting phenomena was performed in dependence on the particle size. The Tool–Narayanaswamy–Moynihan model was successfully used to describe the structural relaxation processes; the compositional evolution of the relaxation parameters was then explained in terms of the structural changes and movements of the characteristic structural units detected by Raman spectroscopy. The nucleation-growth Johnson-Mehl-Avrami model and empirical Autocatalytic model were used to describe the complex kinetics of the DSC crystallization data. Based on the XRD and microscopic analyses the following crystallization mechanisms were revealed: initial nucleation-growth precipitation of hexagonal Te (surface-located) followed by a bulk-located autocatalytic growth of rhombohedral GeTe; in case of higher Se contents an additional formation of the Ge-Te-Se crystalline phase occurred at high temperatures. Higher glass-stability determined for increasing Se content can be associated with the partial inhibition of the crystallization processes, the initial Te precipitation remains, however, further unaffected once Se content reaches ∼4 at.%.

Influence of Al2O3 modification on phosphorus enrichment in high phosphorus slag

The phosphorus enrichment in solid phases during solidification of converter slag was studied by the modification with Al2O3. The mineral phase of the original and modified high phosphorus slags were analysed by SEM + EDS and XRD. The mechanism of Al2O3 modification was discussed based on thermodynamic modelling using the FactSage package. The results show that Ca3(PO4)2 and Ca2SiO4 precipitated first and formed the n2CaO·SiO2–3CaO·P2O5 (nC2S–C3P) solid solution. The content of Al2O3 has no significant impact on the initial precipitation amount of nC2S–C3P solid solution. High phosphorus solid solution (n′C2S–C3P) was generated by the constant reaction between nC2S–C3P (n′<n) solid solution and Al2O3. The concentration of phosphoric pentoxide in phosphorus-rich phase increased to 19.0%, 20.7% and 35.5% with the addition of 5.0%, 8.0% and 11.0% Al2O3, respectively. The initially precipitated solid solution nC2S–C3P reduced and even disappeared with the increase of the Al2O3 content. The results demonstrated that the addition of Al2O3 has a positive influence on the phosphorus enrichment.

Precipitate transformation from NiAl-type to Ni2AlMn-type and its influence on the mechanical properties of high-strength steels

The precipitate transformation from NiAl-type to Ni2AlMn-type and its influence on the mechanical properties of the Fe–5Ni–1Al−xMn (x = 0, 1, 3, and 5 wt.%) alloys were studied thoroughly through a combination of three-dimensional atom probe tomography (APT), first-principles calculations and mechanical tests. APT reveals the precipitation of NiAl-type nanoparticles in the 0-3Mn alloys and the co-precipitation of fine NiAl-type and coarse Ni2AlMn-type nanoparticles in the 5Mn alloy, in which the Ni2AlMn-type nanoparticles are formed as a result of the coarsening of the NiAl-type ones. The first-principles calculations indicate that the Ni2AlMn-type nanoparticles are energetically more favorable than the NiAl-type ones, but their nucleation and growth kinetics are relatively slow, resulting in the initial precipitation of the NiAl-type nanoparticles and the later precipitate transformation from NiAl-type to Ni2AlMn-type. A quantitative analysis of the strengthening mechanism reveals that although the Ni2AlMn-type nanoparticles have a higher strengthening efficiency than the NiAl-type ones, they make a minor contribution to the total strengthening effects due mainly to their small number density. In addition, the Ni2AlMn-type nanoparticles with a composition consistent with that of the Heusler phase are likely to promote the brittle cleavage and intergranular fracture of the 5Mn alloy, resulting in a significant decrease of the alloy ductility.

Modelling the creep behaviour of tempered martensitic steel based on a hybrid approach

In this work, we present a novel hybrid approach to describe and model the creep behaviour of tempered martensitic steels. The hybrid approach couples a physically based model with a continuum damage mechanics (CDM) model. The creep strain is modelled describing the motions of three categories of dislocations: mobile, dipole and boundary. The initial precipitate state is simulated using the thermodynamic software tool MatCalc. The particle radii and number densities are incorporated into the creep model in terms of Zener drag pressure. The Orowan's equation for creep strain rate is modified to account for tertiary creep using softening parameters related to precipitate coarsening and cavitation. For the first time the evolution of internal variables such as dislocation densities, glide velocities, effective stresses on dislocations, internal stress from the microstructure, subgrain size, pressure on subgrain boundaries and softening parameters is discussed in detail. The model is validated with experimental data of P92 steel reported in the literature.

Constraints on the formation and diagenesis of phosphorites using carbonate clumped isotopes

The isotopic composition of apatites from sedimentary phosphorite deposits has been used previously to reconstruct ancient conditions on the surface of the Earth. However, questions remain as to whether these minerals retain their original isotopic composition or are modified during burial and lithification. To better understand how apatites in phosphorites form and are diagenetically modified, we present new isotopic measurements of δ18O values and clumped-isotope-based (Δ47) temperatures of carbonate groups in apatites from phosphorites from the past 265million years. We compare these measurements to previously measured δ18O values of phosphate groups from the same apatites. These results indicate that the isotopic composition of many of the apatites do not record environmental conditions during formation but instead diagenetic conditions. To understand these results, we construct a model that describes the consequences of diagenetic modification of phosphorites as functions of the environmental conditions (i.e., temperature and δ18O values of the fluids) during initial precipitation and subsequent diagenesis. This model captures the basic features of the dataset and indicates that clumped-isotope-based temperatures provide additional quantitative constraints on both the formational environment of the apatites and subsequent diagenetic modification. Importantly, the combination of the model with the data indicates that the δ18O values and clumped-isotope temperatures recorded by phosphorites do not record either formation or diagenetic temperatures, but rather represent an integrated history that includes both the formation and diagenetic modification of the apatites.

Systematic XPS study of gallium-substituted boehmite

Abstract: Ga-substituted boehmites were synthesized using a soft-chemistry route in the presence of poly(ethylene oxide) surfactant under hydrothermal conditions. The effect of Ga-substitution was studied by X-ray diffraction and X-ray photoelectron spectroscopy. Initial precipitates were amorphous (minor bayerite). After hydrothermal treatment, XRD showed broad reflections at low Ga-substation indicating low crystallinity and formation of pseudoboehmite. This was confirmed by high-resolution XPS of Al 2p, Ga 2p, and O 1s. The Al 2p binding energy of 74.03 eV was closer to boehmite than pseudoboehmite, probably caused by the Ga-substitution in the structure. The O 1s showed the presence of O, OH, and H2O. The ratio of (total O)/(Al + Ga) showed an excess of O as expected for pseudoboehmite. The ratio of (O + OH)/Al + Ga) was also slightly larger than the theoretical value of 2 for boehmite. High concentrations of added Ga (10, 20 %) resulted in amorphous material after hydrothermal treatment. Graphical Abstract: [Figure not available: see fulltext.]

Uncertainty and Bias in Satellite-Based Precipitation Estimates over Indian Subcontinental Basins: Implications for Real-Time Streamflow Simulation and Flood Prediction*

Abstract Real-time streamflow monitoring is essential over the Indian subcontinental river basins, as a large population is affected by floods. Moreover, streamflow monitoring helps in managing water resources in the agriculture-dominated region. In this study, the authors systematically investigated the bias and uncertainty in satellite-based precipitation products [Climate Prediction Center morphing technique (CMORPH); Precipitation Estimation from Remotely Sensed Information Using Artificial Neural Networks (PERSIANN); PERSIANN Climate Data Record (PERSIANN-CDR); and Tropical Rainfall Measuring Mission (TRMM), version 7, real-time (3B42RTV7) and gauge-adjusted (3B42V7) products] over the Indian subcontinental river basins for the period of 2000–13. Moreover, the authors evaluated the influence of bias in the satellite precipitation on real-time streamflow monitoring and flood assessment over the Mahanadi river basin. Results showed that CMORPH and PERSIANN underestimated daily mean precipitation over the majority of the subcontinental river basins. On the other hand, TRMM-3B42RTV7 overestimated daily mean precipitation over most of the river basins in the subcontinent. While gauge-adjusted products of PERSIANN (PERSIANN-CDR) and TRMM (TRMM-3B42V7) performed better than their real-time products, large biases remain in their performance to capture extreme precipitation (both frequency and magnitudes) over the subcontinental basins. Among the real-time precipitation products, TRMM-3B42RTV7 performed better than CMORPH and PERSIANN over the majority of the Indian subcontinental basins. Daily streamflow simulations using the Variable Infiltration Capacity model (VIC) for the Mahanadi river basin showed a better performance by the TRMM-3B42RTV7 product than the other real-time datasets. Moreover, daily streamflow simulations over the Mahanadi river basin showed that bias in real-time precipitation products affects the initial condition and precipitation forcing, which in turn affects flood peak timing and magnitudes.