Reversible Precipitation Research Articles

Roles of Al/Ni ratio and solidification cooling rate in grain boundary engineering of AlxCrFeMnNi(2-x) high entropy alloy

In this work, the roles of Al/Ni ratio and solidification cooling rate in grain size, dendrite morphology and grain boundary characteristic of the AlxCrFeMnNi(2-x) (x = 0.3, 0.7 and1.0) high-entropy alloys (HEAs) were investigated. The results show that the increasing of Al/Ni ratio results in a transition from single-phase FCC to dual-phase BCC + B2 along with the reverse precipitation behavior of BCC phase. While the phase composition is not affected by solidification cooling rate. With the increasing of Al/Ni ratio and solidification cooling rate, a significant columnar-to-equiaxed transition (CET) behavior can be observed. That is, grain refinement and transition from columnar dendrites to equiaxial and cellular dendrites. This is mainly attributed to the constitutional supercooling (CS) caused by the solute interaction effect of Al and Ni, and which can be evaluated by P and Q parameters. In addition, in-situ formation of serrated grain boundaries (SGBs) can be also observed in solidification microstructures, and with the increasing of Al/Ni ratio, the proportion of SGBs increases gradually. Whether the B2 precipitated phase is present or not, the formation mechanism of SGBs is mainly attributed to the lattice strain energy caused by the segregation of Al and Ni. The strategy simultaneously achieving grain refinement, CET and in-situ forming SGBs during solidification by tailoring Al/Ni ratio opens new perspectives for grain boundary engineering.

One-Pot Preparation of Ratiometric Fluorescent Molecularly Imprinted Polymer Nanosensor for Sensitive and Selective Detection of 2,4-Dichlorophenoxyacetic Acid.

The development of fluorescent molecular imprinting sensors for direct, rapid, and sensitive detection of small organic molecules in aqueous systems has always presented a significant challenge in the field of detection. In this study, we successfully prepared a hydrophilic colloidal molecular imprinted polymer (MIP) with 2,4-dichlorophenoxyacetic acid (2,4-D) using a one-pot approach that incorporated polyglycerol methacrylate (PGMMA-TTC), a hydrophilic macromolecular chain transfer agent, to mediate reversible addition-fragmentation chain transfer precipitation polymerization (RAFTPP). To simplify the polymerization process while achieving ratiometric fluorescence detection, red fluorescent CdTe quantum dots (QDs) and green fluorescent nitrobenzodiazole (NBD) were introduced as fluorophores (with NBD serving as an enhancer to the template and QDs being inert). This strategy effectively eliminated background noise and significantly improved detection accuracy. Uniform-sized MIP microspheres with high surface hydrophilicity and incorporated ratiometric fluorescent labels were successfully synthesized. In aqueous systems, the hydrophilic ratio fluorescent MIP exhibited a linear response range from 0 to 25 μM for the template molecule 2,4-D with a detection limit of 0.13 μM. These results demonstrate that the ratiometric fluorescent MIP possesses excellent recognition characteristics and selectivity towards 2,4-D, thus, making it suitable for selective detection of trace amounts of pesticide 2,4-D in aqueous systems.

Effect of different precipitants on the formation of ultrafine 3 mol% yttrium-stabilized zirconia nanopowders by reverse precipitation

This study proposes a simple method for preparing highly dispersed ultrafine 3 mol% yttrium-stabilized zirconia nanopowders (3YSZ NPs), which provide high-quality powders for use in high-performance ceramics. First, 3YSZ NPs were prepared using a reverse precipitation method with different precipitants: NaOH, NH3·H2O and (NH3)2CO3. The thermal decomposition, phase evolution, morphology and chemical composition of the precursor particles and 3YSZ NPs were analysed. The effects of precipitant and reaction conditions on 3YSZ NPs were systematically studied. The results show that there are differences in the mechanism of powder synthesis using the co-precipitation method among the three precipitants. In addition, ultrafine 3YSZ NPs with minimum agglomeration and high sphericity can be prepared using NaOH. Y3+ and ZrO2+ cannot coprecipitate in solution according to the designed molar ratio in the NH3·H2O and (NH4)2CO3 methods. Considering agglomeration, crystallinity and elemental distribution, NaOH is the best precipitant. The prepared zirconia powder exhibits high crystallinity, good dispersion, a narrow particle size distribution and a tetragonal phase structure. By investigating the effects of calcination temperature, titration end point pH and NaOH concentration, 3YSZ NPs with an average particle size of 22.29–38.94 nm are obtained.

Membrane-based inverse-transition purification facilitates a rapid isolation of various spider-silk elastin-like polypeptide fusion proteins from extracts of transgenic tobacco

Plants can produce complex pharmaceutical and technical proteins. Spider silk proteins are one example of the latter and can be used, for example, as compounds for high-performance textiles or wound dressings. If genetically fused to elastin-like polypeptides (ELPs), the silk proteins can be reversibly precipitated from clarified plant extracts at moderate temperatures of ~ 30 °C together with salt concentrations > 1.5 M, which simplifies purification and thus reduces costs. However, the technologies developed around this mechanism rely on a repeated cycling between soluble and aggregated state to remove plant host cell impurities, which increase process time and buffer consumption. Additionally, ELPs are difficult to detect using conventional staining methods, which hinders the analysis of unit operation performance and process development. Here, we have first developed a surface plasmon resonance (SPR) spectroscopy-based assay to quantity ELP fusion proteins. Then we tested different filters to prepare clarified plant extract with > 50% recovery of spider silk ELP fusion proteins. Finally, we established a membrane-based purification method that does not require cycling between soluble and aggregated ELP state but operates similar to an ultrafiltration/diafiltration device. Using a data-driven design of experiments (DoE) approach to characterize the system of reversible ELP precipitation we found that membranes with pore sizes up to 1.2 µm and concentrations of 2–3 M sodium chloride facilitate step a recovery close to 100% and purities of > 90%. The system can thus be useful for the purification of ELP-tagged proteins produced in plants and other hosts.

Synthesis of heat-resistant living polymer particles by one-step reversible addition-fragmentation chain transfer precipitation polymerization of styrene and N-phenylmaleimide

For the first time, the synthesis of heat-resistant, “living” polymer particles via one-step reversible addition-fragmentation chain transfer precipitation polymerization (RAFTPP) of styrene (St) and N-phenylmaleimide (PhMI) is reported. Gel permeation chromatography and nuclear magnetic resonance spectroscopy confirmed that the polymerization proceeded in a living manner. The scanning electron microscopy results showed that the monodisperse P(St-PhMI)_RAFTPP particles with a diameter of 1.88 μm were successfully synthesized. The P(St-PhMI)_RAFTPP showed excellent thermal stability with a high glass transition temperature and a 5% weight loss temperature. The surface concentration of the RAFT groups was determined to be 0.181 groups/nm2 due to fragmentation of the RAFT groups exposed on the particles. The small-angle neutron scattering measurements showed the particle formation mechanism, in which the swollen, growing polymer chains were consumed for particle formation. The introduction of grafted chains by surface-initiated RAFT polymerization demonstrated the possibility of further functionalization of P(St-PhMI)_RAFTPP particles by exploiting their living nature.

Synthesis and High-Temperature Heat Capacity of LaMgAl11O19 and SmMgAl11O19 Hexaaluminates

The processes occurring during heating of a stoichiometric mixture of lanthanum, samarium, magnesium, and aluminum hydroxides synthesized by the reverse precipitation method have been studied by DTA/TG and X-ray powder diffraction methods. The conditions for the synthesis of single-phase LaMgAl11O19 and SmMgAl11O19 samples of the magnetoplumbite structure type have been determined, and the isobaric heat capacity has been measured in the temperature range 317–1817 K, showing the absence of structural transformations in this range.

Effect of heat treatment on the hydrogen embrittlement susceptibility of selective laser melted 18Ni-300 maraging steel

The effects of heat treatment on the hydrogen embrittlement (HE) susceptibility of selective laser melted 18Ni-300 maraging steel were investigated. The results demonstrate that the as-built steel has a microstructure consisting of an Fe–Ni martensite matrix and a cellular structure. Substantial microstructural changes are observed following various heat treatment processes (solution, direct aging, and solution-aging), resulting in varying degrees of increased HE susceptibility. Specifically, after solution treatment, the complete elimination of cellular structure and the growth of grains concurrently increased hydrogen diffusion coefficient of the steel. However, its lower proportion of ∑3 boundaries and higher proportion of ∑11 boundaries played an advantageous role that lead to a marginal increase in the HE susceptibility. In contrast, direct aging and solution-aging treatments enhance the HE susceptibility significantly, which is primarily related to the decomposition of the cellular structure and reversible hydrogen trapping and precipitation strengthening effects of the newly formed Ni3(Ti, Mo) precipitates. Compared with the solution-aging treatment, the direct aging treatment results in the formation of a localized austenite aggregation zone near the molten pool boundaries, which promotes the initiation of hydrogen-assisted cracking and leads to a higher HE susceptibility.

Kinetics of the precipitation reaction between aluminium and contaminant orthophosphate ions

ABSTRACT The removal of phosphorous from wastewater in metal-orthophosphate systems typically occurs by simultaneous adsorption on poorly soluble metal hydroxides and by precipitation reactions between metal ions and orthophosphates in solution. To understand the individual contribution of these mechanisms to the removal of phosphorus, the main aim of this study was to determine the kinetics of consumption of contaminant orthophosphates by the precipitation reaction with aluminium ions in a solution free of insoluble aluminium hydroxide. To define the amount of aluminium and phosphorous compounds to be dissolved in water to have this desired reacting condition at a given pH, the solubilities of KH2PO4(s), Al(OH)3(s) and AlPO4(s) were examined at 25 °C in the pH range ∼2.6 to 7.9. pH-solubility diagrams for these ionic solids were made by solving a system of nonlinear algebraic equations involving dissolution, dissociation and hydrolysis reactions at equilibrium. The kinetics of the reaction between aluminium and orthophosphate ions at a reacting condition free of solids except for the product AlPO4(s) was investigated in a well-stirred batch reactor at pH ∼3.1 and 3.5 at 25 °C. A detailed kinetic model involving ten species, seven reversible reactions of hydrolysis of soluble aluminium and orthophosphate species and one reversible precipitation reaction between aluminium and phosphate ions revealed a rate constant for the latter reaction of 5.968 × 1010 L mol−1 s−1 (p = 0.191). XRD, TGA/DTGA and EDX analyses of the filtered and dried reacting mixture confirmed that the only solid product of the precipitation reaction was hydrated AlPO4(s).

Isoelectric point (pI)-based phase separation (pI-BPS) purification of elastin-like polypeptides (ELPs) containing charged, biologically active fusion proteins (ELP-FPs).

Elastin-like polypeptides (ELPs) are peptide-based biomaterials with residue sequence (VPGXG)n where X is any residue except proline. ELPs are a useful modality for delivering biologically active proteins (growth factors, protease inhibitors, anti-inflammatory peptides, etc.) as fusion proteins (ELP-FP). ELP-FPs are particularly cost-effective because they can be rapidly purified using Inverse Temperature Cycling (ITC) via the reversible formation and precipitation of entropically driven aggregates above a transition temperature (Tt ). When ELP fusion proteins (ELP-FPs) contain significant charge density at physiological pH, electrostatic repulsion between them severely inhibits aggregate formation. The literature does not currently describe methods for purifying ELP-FPs containing charged proteins on either side of the ELP sequence as fusion partners without organic solvents. Here, the isoelectric point (pI) of ELP-FPs is discussed as a means of neutralizing surface charges on ELP-FPs and increasing ITC yield to dramatically high levels. We use pI-based phase separation (pI-BPS) to purify ELP-FPs containing cationic and anionic fusion proteins. We report a dramatic increase in protein yield when using pI-BPS for purification of ELP-FPs. Proteins purified by this method also retain the functional activity of the protein present in the ELP-FP. Techniques developed here enable significant diversification of possible fusion proteins delivered by ELPs as ELP-FPs by allowing them to be produced and purified at higher quantities and yields.

Comparative Study of the Synthesis of Ceramic Composites Based on Lanthanum Orthophosphate

Two approaches to the synthesis of nanosized precursor powders 0.5LaPO4·nH2O–0.5ZrO(OH)2 and 0.5LaPO4·nH2O–0.5Y(OH)3 for the fabrication of ceramic composites 0.5LaPO4–0.5ZrO2 and 0.5LaPO4–0.5Y2O3 were used. In the first case, sol-gel synthesis of components (LaPO4·nH2O, ZrO(OH)2 or Y(OH)3) was carried out separately by reverse precipitation technique. In the second case, reverse precipitation was used too but without separate preparation of sols of the components. The results of the synthesis were compared by XRD analysis, thermal behavior of precursor powders by DSC/TG technique, as well as Vickers microhardness values of 0.5LaPO4–0.5ZrO2 and 0.5LaPO4–0.5Y2O3 ceramic composites.

Spark plasma sintering of ceramic materials based on zirconates of rare-earth elements

Powders of rare-earth zirconates, La2Zr2O7 and ZrO2‒8Y2O3 were synthesized by reverse chemical precipitation to obtain ceramic materials on their basis by spark plasma sintering. The formation of the phase composition of ceramics during consolidation by spark plasma sintering has been studied. The thermal conductivity of ceramics based on REE zirconates at 400 °C is 1,79 W/(m·K), which is less than that of La2Zr2O7 ― 2,06 W/(m·K) and ZrO2‒8Y2O3 ― 2,4 W/(m·K). It is shown that the use of REE oxide concentrate is promising for obtaining a ceramic layer of heat-shielding coatings with thermal stability at temperatures above 1200 °C.

A novel thermostable TP-84 capsule depolymerase: a method for rapid polyethyleneimine processing of a bacteriophage-expressed proteins

BackgroundIn spite of the fact that recombinant enzymes are preferably biotechnologically obtained using recombinant clones, the purification of proteins from native microorganisms, including those encoded by bacteriophages, continues. The native bacteriophage protein isolation is often troubled by large volumes of the infected bacterial cell lysates needed to be processed, which is highly undesired in scaled-up industrial processing. A well-known ammonium sulphate fractionation is often a method of choice during purification of the native bacteriophage protein. However, this method is time-consuming and cumbersome, and requires large amounts of the relatively expensive reagent. Thus, other effective and inexpensive methods of reversible protein precipitation are highly desirable. We have previously characterized thermophilic TP-84 bacteriophage, defined a new genus TP84virus within Siphoviridae family, conducted the TP-84 genome annotation and proteomic analysis. The longest Open Reading Frame (ORF) identified in the genome is TP84_26. We have previously annotated this ORF as a hydrolytic enzyme depolymerizing the thick polysaccharides host’s capsule.ResultsThe TP84_26 ‘capsule depolymerase’ (depolymerase) is a large, 112 kDa protein, biosynthesized by the infected Geobacillus stearothermophilus 10 (G. stearothermophilus 10) cells. The TP84_26 protein biosynthesis was confirmed by three approaches: (i) purification of the protein of the expected size; (ii) mass spectrometry (LC–MS) analysis and (iii) detection of the enzymatic activity toward G. stearothermophilus polysaccharide capsules. Streptomycin-resistant mutant of the host was generated and microbiological aspects of both the TP-84 and G. stearothermophilus 10 were determined. A new variant of polyethyleneimine (PEI)-mediated purification method was developed, using the novel TP-84 depolymerase as a model. The enzyme was characterized. Three depolymerase forms were detected: soluble, unbound proteins in the bacteriophage/cells lysate and another integrated into the TP-84 virion.ConclusionsThe novel TP-84 depolymerase was purified and characterized. The enzyme exists in three forms. The soluble, unbound forms are probably responsible for the weakening of the capsules of the uninfected bacterial cells. The form integrated into virion particles may generate a local passage for the invading TP-84. The developed PEI purification method appears well suited for the scaled-up or industrial production of bacteriophage proteins.

ТЕРМОДИНАМИЧЕСКОЕ ИССЛЕДОВАНИЕ СЛОЖНЫХ ОКСИДОВ САМАРИЯ СО СТРУКТУРОЙ ПИРОХЛОРА

The results of a thermodynamic study of a group of inorganic compounds of the general formula Ln2M2O7, where M = Sn, Ti, are presented. Single-phase samples were obtained by reverse precipitation followed by high-temperature synthesis. Crystallographic parameters were calculated and their dependence on the radius of the element is shown. The temperature dependences of the heat capacity are experimentally studied in a wide temperature range. The thermodynamic properties of samarium compounds with a pyrochlore-type structure are compared.

The pH-responsive precipitation–redissolution of the CspB fusion protein, CspB50TEV-Teriparatide, triggered by changes in secondary structure

Cell surface protein B (CspB) fusion proteins can undergo reversible pH-responsive precipitation–redissolution. A pH-responsive precipitation–redissolution of CspB tag purification (pPRCP) method was established for protein purification using this property. However, the mechanism of the pH-responsive precipitation of CspB fusion proteins is unknown, which has made it difficult to set process parameters for pPRCP. In this study, we investigated the mechanism of the pH-responsive precipitation of CspB fusion proteins using CspB50TEV-Teriparatide (CspB-teri) as a model. As expected, CspB-Teri was reversibly precipitated at acidic pH. By contrast, CspB-Teri was not precipitated under unfolding conditions induced by trifluoroethanol, urea, or guanidine hydrochloride, even at acidic pH. The conformation of CspB-Teri changed to a β-sheet-rich structure as the pH decreased, followed by the formation of intermolecular interactions, which caused precipitation. The particle size of the CspB-Teri precipitate increased in a protein concentration-dependent manner. These results indicated that the pH-responsive precipitation of CspB-Teri is triggered by the formation of a β-sheet structure in response to decreasing pH, and the growth of the precipitate particles occurred through intermolecular interactions.

Column-free purification of an artificial protein nanocage, TIP60

Protein nanocages, which have inner cavities and surface pores, are attractive materials for various applications, such as in catalysts and medicine. Recently, we produced an artificial protein nanocage, TIP60, and demonstrated its potential as a stimuli-responsive nanocarrier. In the present study, we report a simple purification method for TIP60 that can replace time-consuming and costly affinity chromatography purification. TIP60, which has an anionic surface charge, aggregated at mildly acidic pH and redissolved at neutral pH, maintaining its cage structure. This pH-responsive reversible precipitation allowed us to purify TIP60 from soluble fractions of the E. coli cell lysate by controlling the pH. Compared with conventional Ni-NTA column purification, the pH-responsive precipitation method provided purified TIP60 with similar purity (∼80%) and higher yield. This precipitation purification method should facilitate the large-scale investigation and practical use of TIP60 nanocages.

Approach to acute psychosis in older adults.

Approach to acute psychosis in older adults.

Effect of rare-earths (La, Nd, Pr) on zirconate ceramics for thermal barrier coatings

Zirconium oxide-based powders with different concentrations of REE concentrate (La, Nd, Pr) in an amount from 25 to 35 mol.% were synthesized by the reverse chemical precipitation method. The formation of REE zirconates during consolidation has been studied by Raman spectroscopy, XRD and scanning electron microscopy. It has been established that the formation of REE zirconates with the pyrochlore structure occurs after annealing of synthesised powders at a temperature of 1000°C. It has been demonstrated that densifying processes during sintering at 1400 –1600°C occur most slowly in a ceramic material with 35 mol.% REE oxides, which has a stable phase composition at all sintering temperatures, consisting mainly of REE zirconates with the pyrochlore structure. The resulting ceramic material based on REE zirconates has phase stability at 1300°C.

Effects of re-solution, pre-stretching and double re-ageing treatment on mechanical behavior and microstructure of 2195 Al–Cu–Li alloy

The effects of re-solution, pre-stretching and double re-ageing (RPD) treatment on the microstructure and mechanical performance of 2195 Al–Cu–Li alloy were investigated. The results indicate that RPD treatment enhances the strength from ∼567 MPa with a standard T8 temper to ∼584 MPa. A simultaneous improvement in strength and ductility is attained in a PA-RPD sample processed by 510 °C × 1 h re-solution, 7% pre-stretching and 120 °C × 12 h + 155 °C × 24 h double re-ageing. The improved mechanical properties are ascribed to the re-tailor of microstructures during RPD treatment involving grain morphology, dislocation density, and precipitation feature. The PA-RPD samples with varied pre-strains exhibit no evident difference in grain size, but slightly larger than that at T8 state and much smaller than that at re-solution state. The dislocation density is mainly determined by the pre-stretching levels and suffered minor annihilation in double re-ageing. T1 precursor phases are nucleated from first-step re-ageing (120 °C), most of which are connected to pre-stretched dislocations, and then grow into well-dispersed T1 plates in second-step re-ageing (155 °C). The increased strength is dominantly attributed to the reversible finer precipitation of nano-sized T1 plates, yielding considerable precipitation strengthening, as well as higher dislocation density, producing dislocation strengthening. The improved ductility in the PA-RPD sample is mainly on account of the finer and more uniform distribution of T1 plates which enhance the plastic stability during tensile testing.

Total Dissolved Solids and Their Removal Techniques

Total dissolved solids (TDS) due to both geogenic and anthropogenic contaminations, is one of the preliminary as well as essential parameters among others to describe water quality. It includes organic and inorganic components, heavy metals, salts, other dissolved substances, and others due to indiscriminate disposal of untreated domestic and industrial effluents, urban and/or agricultural runoff which exists in the form of micro or nano level in nature. Higher TDS levels in water severely impact health and the environment. For instance, it causes gastrointestinal, cardiovascular, genotoxic, respiratory, skin, and hepatic effects in humans. High TDS level (> 500 ppm) results in excessive scaling in household appliances (e.g., pipes, heaters, and boilers) thereby reducing their efficiency. Therefore, the removal of TDS from various water matrices is taking paramount importance to minimize its impact on health and the environment. Various TDS removal technologies based on the membrane, ion, and temperature gradient are employed to treat water. In this review paper, several TDS removal technologies for instance reverse osmosis, nanofiltration, distillation, ultrafiltration, forward osmosis, precipitation, desalination, ion exchange, electrochemical techniques, electrodialysis, electrolysis, electrocoagulation, and adsorption are discussed in detail.

High Efficacy Combined Microneedles Array with Methotrexate Nanocrystals for Effective Anti-Rheumatoid Arthritis.

IntroductionMethotrexate (MTX) is the first-line drug for the treatment of rheumatoid arthritis (RA) in several countries. However, MTX has an extremely low solubility in water, and the side effects caused by its delivery mode restrict its curative effect. In this study, we designed a dissolving microneedles array (DMNA) containing MTX nanocrystals (MTX-NCs) (MTX-NC@DMNA) to improve the treatment of RA. DMNA-based drug delivery combines the advantages of patient compliance with the use of transdermal drug delivery systems and high-efficiency injection administration; thus, it can mitigate the side effects that result from current administration routes. Carrier-free and surfactant-free MTX-NCs were prepared to overcome bioavailability limitations and poor drug loading problems.MethodsThe MTX-NCs prepared by reverse solvent precipitation method was encapsulated in the DMNA. The morphology, mechanical properties, safety, stability and in vivo dissolution were evaluated, and its pharmacodynamic characteristics were assessed in a rat model of RA.ResultsThe particle size of the MTX-NCs was 148.1 ± 10.1 nm. The MTX-NC@DMNA were found to be rigid enough to penetrate the skin and deliver the drug successfully. The results indicated effective skin recovery after removal of the DMNA. It was found that the MTX-NC@DMNA significantly reduced foot swelling in the rats and regulated the balance in the levels of related cytokines. It also reduced pathological damage to the synovium, joint, and cartilage, and effectively alleviated organ injury in the rats.ConclusionTransdermal administration of MTX-NC@DMNA may be an effective approach for treating RA.