Complex Precipitation Process Research Articles

Co-administration of Intravenous Drugs: Rapidly Troubleshooting the Solid Form Composition of a Precipitate in a Multi-drug Mixture Using On-Site Raman Spectroscopy.

Intravenous drugs are often co-administrated in the same intravenous catheter line due to which compatibility issues, such as complex precipitation processes in the catheter line, may occur. A well-known example that led to several neonatal deaths is the precipitation due to co-administration of ceftriaxone- and calcium-containing solutions. The current study is exploring the applicability of Raman spectroscopy for testing intravenous drug compatibility in hospital settings. The precipitation of ceftriaxone calcium was used as a model system and explored in several multi-drug mixtures containing both structurally similar and clinically relevant drugs for co-infusion. Equal molar concentrations of solutions containing ceftriaxone and calcium chloride dihydrate were mixed with solutions of cefotaxime, ampicillin, paracetamol, and metoclopramide. The precipitate formed was collected as an "unknown" material, dried, and analyzed. Several solid-state analytical methods, including X-ray powder diffraction, Raman spectroscopy, and thermogravimetric analysis, were used to characterize the precipitate. Raman microscopy was used to investigate the identity of single sub-visual particles precipitated from a mixture of ceftriaxone, cefotaxime, and calcium chloride. X-ray powder diffraction suggested that the precipitate was partially crystalline; however, the identity of the solid form of the precipitate could not be confirmed with this standard method. Raman spectroscopy combined with multi-variate analyses (principal component analysis and soft independent modelling class analogy) enabled the correct detection and identification of the precipitate as ceftriaxone calcium. Raman microscopy enabled the identification of ceftriaxone calcium single particles of sub-visual size (around 25 μm), which is in the size range that may occlude capillaries. This study indicates that Raman spectroscopy is a promising approach for supporting clinical decisions and especially for compatibility assessments of drug infusions in hospital settings.

Spatio-temporal performance evaluation of 14 global precipitation estimation products across river basins in southwest Iran

Study regionKarkheh and Karun basins (29°−35°N, 46°−52°E) are two large river basins (area 51,000 and 67,000 km2, respectively) with complex topography in southwest Iran. Study focusAccess to spatio-temporally consistent precipitation data is a key requirement for hydrological studies, especially in data-scarce regions. This study evaluated 14 global precipitation products against gauge observations from 2003 to 2012 in Karun and Karkheh basins, southwest Iran. Different categorical and statistical indices at varying spatial and temporal resolution, including Kling-Gupta Efficiency (KGE), bias, correlation coefficient, and variability ratio, were used to evaluate the products. New hydrological insights for the regionFor daily time steps, TMPA-3B42V7.0, MERRA-2, and CMORPH-BLDV1.0 outperformed all other products, with KGE > 0.3. TMPA-3B42V7.0, MERRA-2, and PERSIANN-CDR were the best-performing products for monthly time steps, with KGE> 0.5. ERA5-Land showed the highest positive bias (bias>1.5) compared with in-situ observations, particularly for mountainous southeastern parts of Karun basin. Overall, bias-adjusted products obtained by merging ground-based observations in the estimations outperformed the unadjusted versions. The spatial distribution of statistical error metrics indicated that almost all products showed their greatest uncertainties for mountainous regions due to complex precipitation processes in these regions. These results can contribute significantly to hydrological and water resources planning measures in the study region, including early flood warning systems, drought monitoring, and optimization of dam operation.

Phase transformations in creep resistant MgYNdScMn alloy

Abstract Mg-4 wt.% Y-2 wt.% Nd-1 wt.% Sc-1 wt.% Mn alloy was squeeze-cast. It benefited from the addition of Nd which decreased the solubility of Y in Mg, as is known from WE alloys. Isochronal annealing of the alloy showed relative resistivity changes similar to those obtained in other Mg–R.E. –Sc –Mn alloys (R.E. – rare-earth element). The resistivity decrease observed is due to the complex precipitation process, namely a combination of decomposition sequences in the Mg–Y–Nd, Mg–R.E. –Mn, and Mn–Sc systems. The increase in the resistivity on isochronal annealing up to temperatures over 500 °C is due to the re-solution of the phases in the first two systems. The Mn2Sc phase coarsens only during this annealing treatment. The creep resistance of the alloy at high temperatures is better than that of low Sc content Mg alloys with Yand Gd in the T5 condition and also than that of WE alloys in the T6 condition.

Application of an improved multifractal detrended fluctuation analysis approach for estimation of the complexity of daily precipitation

AbstractAffected by climate change and high‐intensity human activities, the precipitation series is characterized by nonlinear complex fluctuations. In order to accurately quantify the precipitation complexity, the complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) method was introduced to address the shortcomings of the traditional multifractal detrended fluctuation analysis (MFDFA), and the CEEMDAN‐MFFA method was proposed to explore the spatiotemporal variability and possible causes of precipitation complexity in Northeast China (NEC). The results showed that the traditional MFDFA method generally overestimated precipitation complexity. However, the CEEMDAN‐MFFA method improved the accuracy and reliability of precipitation complexity analysis. Daily precipitation series in NEC were characterized by multifractal with high uncertainty and anti‐persistence. The lowest precipitation complexity was 0.573, which appeared in Qian'an, Jilin Province, and the highest precipitation complexity was 1.108, which appeared in the Boketu, Inner Mongolia. The cities with high complexity of daily precipitation are sporadically distributed in the three provinces of Heilongjiang, Jilin and Liaoning. The average complexity is ~0.892, accounting for 22.5% of the total administrative districts. The complexity of daily precipitation showed a statistically insignificant downward trend with time. The precipitation dynamics structure in the southeast and northwest of the study area was complex, and the precipitation was less predictable than other regions. However, the precipitation dynamics structure was relatively simple and the precipitation was easily predictable in the northeastern, central and southwestern regions. Elevation, topographic relief, changes in water area, forest area and agricultural production were the main influencing factors for the differences in precipitation complexity. Results also revealed that increasing the area of forestland by means of protecting and breeding forests, via regulation of the forest ecosystems to alleviate the complex precipitation process will become a reliable approach to cope with nonstationary precipitation.

Multiple Influences of Molybdenum on the Precipitation Process in a Martensitic PH Stainless Steel

Molybdenum has been found to influence the complex precipitation process in a martensitic precipitation hardening stainless steel during aging at 475 °C in several different ways. Three steels with different Mo content (0, 1.2 and 2.3 at.%) were investigated. Studies of the microstructure were performed with atom probe tomography and energy filtered transmission electron microscopy. It is shown that, at the initial stage of aging, a faster nucleation of Cu-rich clusters takes place with increasing Mo content. The Cu-clusters act as precipitation sites for other solute elements and promote the nucleation of Ni-rich phases. During further aging, a higher Mo content in the material instead slows down the growth and coarsening of the Ni-rich phases, because Mo segregates to the interface between precipitate and matrix. Additionally, Mo promotes decomposition of the matrix into α and α′ regions. After longer aging times (>40 h) quasicrystalline Mo-rich R′ phase forms (to a greater extent in the material having the highest Mo content). The observations serve to understand the hardness evolution during aging.

Spatial and temporal characteristics of stable isotopes in the Tarim River Basin

By using 233 isotope samples, we investigated the spatial and temporal variations of δ18O and δ2H in precipitation and surface water, and the contribution of different water sources in the rivers within the Tarim River Basin (TRB), which receives snow/glacier meltwater, groundwater, and rainfall. Our study revealed a similar seasonal pattern of precipitation δ18O and δ2H at both the north and south edges of the basin, indicating the dominant effect of westerly air masses in the summer and the combined influence of westerly and polar air masses during the winter, although the southern part showed more complex precipitation processes in the summer. River water in the basin has relatively large temporal variations in both δ18O and δ2H showing a distinct seasonal pattern with lower isotope values in May than in September. Higher d-excess values throughout the year in the Aksu river and the Tizinafu river suggest that water may be intensively recycled in the mountains of the TRB. Based on isotopic hydrograph separation, we found that groundwater is the main water source that discharges the entire basin although individual rivers vary.

Compositional evolution of Q-phase precipitates in an aluminum alloy

Lightweight, age-hardenable aluminum alloys are attracting increasing attention as a means to reduce vehicle mass and improve fuel economy. To accelerate the adoption of these alloys, knowledge of the complex precipitation processes that underlie their primary strengthening mechanism is essential. Here we employ a combination of atom-probe tomography (APT), differential scanning calorimetry (DSC), transmission electron-microscopy, X-ray diffraction and first-principles calculations to reveal the compositional evolution of Q-phase precipitates in a commercial, age-hardenable aluminum alloy, W319. Three different aging conditions are investigated: 438K/8h, 463K/8h and 533K/4h. Co-precipitation of θ′- and Q-phase precipitates is observed for all aging conditions, which, when combined with DSC analysis of the precipitation sequence, suggests that Q-phase precipitates serve as heterogeneous nucleation sites for θ′-platelets. Regarding composition evolution, aging at the lower temperatures yields Q-phase precipitates that are Cu-rich, yet deficient in Mg and Si: 44Al–22Cu–16Mg–16.5Siat.%. The composition evolves to become Mg-rich after aging at 533K: ∼28Al–9Cu–37Mg–26Siat.%. APT provides evidence for partitioning of Zn to the Q-phase precipitates. The energetics of Zn partitioning was evaluated using first-principles calculations, and suggests that this partitioning is a kinetic effect. Our analyses provide new insights into the complex precipitation processes in commercial Al alloys, and should foster the enhancement of alloy performance through optimization of aging conditions.

Simulation of the effect of composition on the precipitation in 6xxx Al alloys during continuous-heating DSC

The precipitation behaviour of Al–Mg–Si alloys has been studied by differential scanning calorimetry (DSC) and by thermo-kinetic modelling. Three industrial alloys with different main solute contents, namely Mg, Si, Cu are used. Main aspect is given to the different Mg/Si ratios of the investigated alloys. Observed exothermic and endothermic peaks, accompanying the formation or dissolution of precipitates, are attributed to the formation or dissolution of individual phases, a procedure, which becomes rather involved if precipitation peaks of phases overlap. In the present paper, we propose a combination of experimental DSC analysis and computer simulation of precipitation kinetics to overcome this problem. By an iterative thermo-kinetic optimization of the simulation parameters and comparison with the heat flow evolution of the experiment, a unique picture of the complex precipitation process for different Mg/Si ratios is obtained. Exemplarily, experimental heat flow curves of various 6xxx Al alloys are unravelled and compared to the heat flow evaluated with thermo-kinetic computer simulations.

Effect of microalloying on precipitate evolution in ferritic welds and implications for toughness

Ferritic weld metal deposited with a self-shielded arc-welding process has intentional additions of aluminum, magnesium, titanium and zirconium. This results in a complex precipitation process that has been characterized with a combination of electron microscopy techniques. This work indicates that the formation of a spinel oxide is critical for the nucleation of nitrides of zirconium and titanium and prevents the agglomeration of aluminum rich oxides and the formation of large aluminum nitrides. High-resolution transmission electron microscopy has been used to characterize the core/shell structure of the precipitates with microalloying additions. Thermodynamic modeling of the precipitate formation during solidification is consistent with the microstructural observations. The evolution of precipitate formation is critical to limit large inclusions and improve weld metal toughness.

Preparation and Luminescence of Y<sub>2</sub>O<sub>3</sub>:Eu<sup>3+</sup> Nanopowder

Eu3+ doped Y2O3 nanopowder was prepared by a novel complex precipitation process in which the mixture of ammonium water and ammonium hydrogen carbonate was adopted as complex precipitant. The precipitant precursor and the resultant powder were characterized by FT-IR, XRD, SEM and TEM. The resultant weakly agglomerate and spherical particles have a uniform grain size about 20nm after calcined at 850°C for 2 hours. 3mol% Eu3+ doped Y2O3 nanopowder shows an intense red luminescence at 612nm under UV excitation.

Phase transformations in creep resistant MgYNdScMn alloy

Abstract Mg-4 wt.% Y-2 wt.% Nd-1 wt.% Sc-1 wt.% Mn alloy was squeeze-cast. It benefited from the addition of Nd which decreased the solubility of Y in Mg, as is known from WE alloys. Isochronal annealing of the alloy showed relative resistivity changes similar to those obtained in other Mg–R.E.–Sc–Mn alloys (R.E. – rare-earth element). The resistivity decrease observed is due to the complex precipitation process, namely a combination of decomposition sequences in the Mg–Y–Nd, Mg–R.E.–Mn, and Mn–Sc systems. The increase in the resistivity on isochronal annealing up to temperatures over 500 °C is due to the re-solution of the phases in the first two systems. The Mn2Sc phase coarsens only during this annealing treatment. The creep resistance of the alloy at high temperatures is better than that of low Sc content Mg alloys with Yand Gd in the T5 condition and also than that of WE alloys in the T6 condition.

Crystallization and precipitation engineering

New computational techniques for the analysis and design of systems for the manufacture of particulate crystals have become available, and the more complex precipitation processes whereby crystallization follows fast chemical reactions have also been analysed more deeply. This progress has been aided by the growing power of the population balance and kinetic models, computational fluid dynamics (CFD) and mixing theory, respectively. These aspects are selectively reviewed and areas requiring further progress are identified.

Evaluation of aging precipitation kinetics and potential in aluminum alloys using indiscriminately integrated peak areas in calorimetry curves

This article explores the possibility of evaluating aging precipitation kinetics and potential using differential scanning calorimetry curves without the need of peak separation or considering individual precipitation phases. Several aluminum alloy systems are investigated, using published data. The results show that this method is effective, if accurate data are available. Some of the error sources and the reason why this indiscriminate integration method can work for the complex precipitation processes in aluminum alloys are discussed.

Microstructure and Phase Changes Due to Heat Treatment of Squeeze Cast Mg-Sc-(Ce)-Mn Alloys

The time dependence of the electrical resistivity of MgScMn and MgScCeMn alloys due to isothermal annealing at 500 and 600 °C confirms the results of thermodynamic calculations that a homogenisation heat treatment (T4) and consequently a full age hardening (T6) is impossible. The peak age hardening of the as-cast material (T5) is due to the precipitation of fine dense Mn2Sc particles in both materials accompanied by the precipitation of Mg12Ce particles in Ce containing alloys. This microstructure accounts for the excellent creep resistance of these materials which is superior to the high temperature creep resistant alloy WE43. The decrease in electrical resistivity during isochronal annealing in the temperature range 300–400 °C (MgScMn) and 300–480 °C (MgScCeMn) has been shown by TEM observations to be due to the same precipitation processes. TTT diagrams drawn from peak hardness values obtained by the isothermal heat treatment also confirm the complex precipitation process in MgScCeMn alloys. Short pseudo-homogenisation heating at 600 °C preceding the isochronal annealing causes another earlier resistivity decrease at 200–300 °C in quaternary alloys corresponding to a different precipitation sequence.

Development of Creep Resistant Mg-Gd-Sc Alloys with Low Sc Content

High thermal stability and good mechanical properties are crucial for the wider future application of magnesium alloys. One of the most promising directions is the alloying of Mg with rare earth elements as Gd. The fine dispersion of metastable β' phase (c-base centred orthorhombic, a = 0.641 nm, b = 2.223 nm, c = 0.521 nm), already known from commercially successful WE alloys (Mg-Y-Nd-Zr), precipitated in all three possible orientation modes during T6 treatment causes very pronounced age hardening in binary Mg-Gd system and inhibits very effectively the dislocation motion during the creep. The stable β phase (Mg 5 Gd, f.c.c. structure, a = 2.234 nm) ensures the creep resistance comparable to WE alloys. A high content of Gd (above 10 wt.%) is necessary to attain the required microstructure. The addition of Sc (below 1 wt.%) and Mn (about 1.5 wt.%) suppresses the solubility of Gd in Mg considerably. The complex precipitation process involving the precipitation of very stable Mn 2 Sc, Mn and Gd containing phase and metastable β' phase is responsible for superior creep properties of MgGd5Sc0.3Mn1 alloy at elevated temperatures. Even at 300 °C the creep resistance is markedly better than for WE43 alloy. The increased Gd and Sc contents in MgGd10Sc0.8Mn1 alloy do not further improve the creep resistance.

Synthesis of LaCrO<sub>3</sub> from Complex Precipitation and Its Electrical Conductivity

A well-crystallized LaCrO3 powder with a primary particle size of about 1μm was synthesized through the complex precipitation process; obtaining the precipitate of complex hydroxide from an NaOH aqueous solution of Cr(NO3)3 by adding LaCl3 and then heating the precipitate up to 700°C. The LaCrO3 single-phased powder was prepared from the precipitate obtained by adding less amount of La3+ than the equimolar ratio, but an excess adding of La3+ resulted in La2CrO6 with LaCrO3. From density measurements and SEM observations, the powder thus prepared has no remarkable sinterability. However, the electrical conductivity (about 0.069S/cm) of the specimen, of which relative density was as low as 57%, was comparable with those reported on the dense specimens. The temperature dependence of conductivity of the present specimen showed a break around 180°C. The activation energy was determined as 0.20 and 0.23eV above and below 180°C, respectively.