The application of hybrid pixel detectors for in‐house SAXS instrumentation with a view to combined chromatographic operation

This study analyses the potential for laboratory‐based size‐exclusion chromatography (SEC) integrated small‐angle X‐ray scattering (SAXS) instrumentation to characterize protein complexes. Using a high‐brilliance home source in conjunction with a hybrid pixel X‐ray detector, the efficacy of SAXS data collection at pertinent protein concentrations and exposure times has been assessed. Scattering data from SOD1 and from the complex of SOD1 with its copper chaperone, using 10 min exposures, provided data quality in the range 0.03 < q < 0.25 Å^?1 that was sufficient to accurately assign radius of gyration, maximum dimension and molecular mass. These data demonstrate that a home source with integrated SEC–SAXS technology is feasible and would enable structural biologists studying systems containing transient protein complexes, or proteins prone to aggregation, to make advanced preparations in‐house for more effective use of limited synchrotron beam time.     

Stabilization of aqueous nanoscale zerovalent iron dispersions by anionic polyelectrolytes: adsorbed anionic polyelectrolyte layer properties and their effect on aggregation and sedimentation

Nanoscale zerovalent iron (NZVI) particles are 5–40 nm sized Fe⁰/Fe-oxide particles that rapidly transform many environmental contaminants to benign products and are a promising in situ remediation agent. Rapid aggregation and limited mobility in water-saturated porous media limits the ability to deliver NZVI dispersions in the subsurface. This study prepares stable NZVI dispersions through physisorption of commercially available anionic polyelectrolytes, characterizes the adsorbed polymer layer, and correlates the polymer coating properties with the ability to prevent rapid aggregation and sedimentation of NZVI dispersions. Poly(styrene sulfonate) with molecular weights of 70 k and 1,000 k g/mol (PSS70K and PSS1M), carboxymethyl cellulose with molecular weights of 90 k and 700 k g/mol (CMC90K and CMC700K), and polyaspartate with molecular weights of 2.5 k and 10 k g/mol (PAP2.5K and 10K) were compared. Particle size distributions were determined by dynamic light scattering during aggregation. The order of effectiveness to prevent rapid aggregation and stabilize the dispersions was PSS70K(83%) > ≈PAP10K(82%) > PAP2.5K(72%) > CMC700K(52%), where stability is defined operationally as the volume percent of particles that do not aggregate after 1 h. CMC90K and PSS1M could not stabilize RNIP relative to bare RNIP. A similar trend was observed for their ability to prevent sedimentation, with 40, 34, 32, 20, and 5 wt%, of the PSS70K, PAP10K, PAP2.5K, CMC700K, and CMC90K modified NZVI remaining suspended after 7 h of quiescent settling, respectively. The stable fractions with respect to both aggregation and sedimentation correlate well with the adsorbed polyelectrolyte mass and thickness of the adsorbed polyelectrolyte layers as determined by Oshima’s soft particle theory. A fraction of the particles cannot be stabilized by any modifier and rapidly agglomerates to micron sized aggregates, as is also observed for unmodified NZVI. This non-dispersible fraction is attributed to strong magnetic attractions among the larger particles present in the polydisperse NZVI slurry, as the magnetic attractive forces increase as r⁶.     

Application of SAXS to the study of particle-size-dependent thermal conductivity in silica nanofluids

Knowledge of the size and distribution of nanoparticles in solution is critical to understanding the observed enhancements in thermal conductivity and heat transfer of nanofluids. We have applied small-angle X-ray scattering (SAXS) to the characterization of SiO₂ nanoparticles (10–30 nm) uniformly dispersed in a water-based fluid using the Advanced Photon Source at Argonne National Laboratory. Size distributions for the suspended nanoparticles were derived by fitting experimental data to an established model. Thermal conductivity of the SiO₂ nanofluids was also measured, and the relation between the average particle size and the thermal conductivity enhancement was established. The experimental data contradict models based on fluid interfacial layers or Brownian motion but support the concept of thermal resistance at the liquid–particle interface.     

Measurement of soot morphology by integrated LII and elastic light scattering

A compact experimental setup that integrates laser-induced incandescence (LII) and one-angle elastic light scattering (1A-ELS) to measure the size of polydisperse soot aggregates is described. A 532 nm laser and a detection angle of 35 degrees were employed, which provided sensitivity for aggregate radius of gyrations (R _g) of R _g≤200 nm. Both lognormal and self-preserving distribution functions are compared with width parameters derived from both aggregation theory and transmission electron microscopy (TEM) measurements. Using these distributions, mean aggregate sizes derived from the scattering measurements are compared. The LII+1A-ELS technique is validated with a two-angle elastic light scattering (2A-ELS) approach with an additional detection angle at 145 deg. Unlike LII+1A-ELS, the 2A-ELS technique has the advantage of not requiring knowledge of soot optical properties. Good agreement is found between the two techniques for a given distribution. A fundamental discrepancy exists between distributions derived from TEM and those according to aggregation theory, limiting the accuracy of both 2A-ELS and LII+1A-ELS. The dependence of both techniques on laser fluence and hence soot temperature is examined and discussed.     

Small‐angle solution scattering using the mixed‐mode pixel array detector

Solution small‐angle X‐ray scattering (SAXS) measurements were obtained using a 128 × 128 pixel X‐ray mixed‐mode pixel array detector (MMPAD) with an 860 µs readout time. The MMPAD offers advantages for SAXS experiments: a pixel full‐well of >2 × 10⁷ 10 keV X‐rays, a maximum flux rate of 10⁸ X‐rays pixel^?1 s^?1, and a sub‐pixel point‐spread function. Data from the MMPAD were quantitatively compared with data from a charge‐coupled device (CCD) fiber‐optically coupled to a phosphor screen. MMPAD solution SAXS data from lysozyme solutions were of equal or better quality than data captured by the CCD. The read‐noise (normalized by pixel area) of the MMPAD was less than that of the CCD by an average factor of 3.0. Short sample‐to‐detector distances were required owing to the small MMPAD area (19.2 mm × 19.2 mm), and were revealed to be advantageous with respect to detector read‐noise. As predicted by the Shannon sampling theory and confirmed by the acquisition of lysozyme solution SAXS curves, the MMPAD at short distances is capable of sufficiently sampling a solution SAXS curve for protein shape analysis. The readout speed of the MMPAD was demonstrated by continuously monitoring lysozyme sample evolution as radiation damage accumulated. These experiments prove that a small suitably configured MMPAD is appropriate for time‐resolved solution scattering measurements.     

Formation of fractal aggregates during green synthesis of silver nanoparticles

The aggregation behavior of silver nanoparticles (AgNPs) prepared by a green synthesis procedure using starch as the stabilizer was studied by the small angle X-ray scattering (SAXS) technique. The protecting ability of starch was affected by the presence of NaOH leading to different aggregation behaviors. In all the samples, mass as well as surface fractal regimes were observed. Assuming spherical form, the radii of nanoparticles were in the range of 11–17 nm.     

Aggregation kinetics of CeO<Subscript>2</Subscript> nanoparticles in KCl and CaCl<Subscript>2</Subscript> solutions: measurements and modeling

To characterize the environmental transport and health risks of CeO₂ nanoparticles (NPs), it is important to understand their aggregation behavior. This study investigates the aggregation kinetics of CeO₂ NPs in KCl and CaCl₂ solutions using time-resolved dynamic light scattering (TR-DLS). The initial hydrodynamic radius of CeO₂ NPs measured by DLS was approximately 95 nm. Attachment efficiencies were derived both from aggregation data and predictions based on the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. The deviations of the DLVO predictions were corrected by employing the extended DLVO (EDLVO) theory. The critical coagulation concentration (CCC) of CeO₂ NPs at pH = 5.6 is approximately 34 mM for KCl and 9.5 mM for CaCl₂. Furthermore, based on the EDLVO theory and the von Smoluchowski’s population balance equation, a model accounting for diffusion-limited aggregation (DLA) kinetics was established. For the reaction-limited aggregation (RLA) kinetics, a model that takes fractal geometry into account was established. The models fitted the experimental data well and proved to be useful for predicting the aggregation kinetics of CeO₂ NPs.     

Ultrasound-enhanced interfacial adsorption and inactivation of soy trypsin inhibitors

In this study, liquid–liquid interfacial protein adsorption was proposed as a means of inactivating soy trypsin inhibitors (TIs, including Kunitz (KTI) and Bowman-Birk inhibitor (BBI)). Hexane-water was first selected as a model system to compare three emulsification methods (hand shaking, rotor–stator and ultrasound mixing). Ultrasound could generate the smallest and least polydisperse emulsion droplets, resulting in highest interfacial adsorption amount of KTI and BBI as well as the highest inactivation percentage of TIs (p < 0.05). Therefore, ultrasound was selected to further explore the effect of the non-aqueous phase on interfacial adsorption and inactivation kinetics of TIs in a food emulsion system containing vegetable oil (VTO). The adsorption amounts of KTI and BBI in the VTO-aqueous emulsion increased by ∼ 25 % compared to the hexane-aqueous emulsion. In addition, the adsorption amounts of KTI and BBI were rapidly increased as a function of sonication time, especially for the hexane-aqueous emulsion system. This result suggests that such inactivation of TIs could be implemented in continuous systems for large-scale processing. Finally, the pathways of interface-induced inactivation of BBI and KTI were investigated based on separate experiments on individual BBI and KTI systems. The results showed that the interface adsorption caused the changes in the secondary and tertiary structure of KTI that led to its activitation. However, BBI was quite stable at the liquid–liquid interface without significant conformational change. Overall, ultrasound-assisted interfacial adsorption can be considered a rapid and highly efficient method to inactivate KTI.     

Aggregation of particles settling in shear-thinning fluids

We have experimentally studied the coaxial settling of three identical non-Brownian spheres in a shear-thinning fluid at small Reynolds numbers. While settling, the particles create corridors of reduced viscosity in their wake and, if they are initially close enough to one another, they can form stable clusters. By analogy with previous results obtained on two-particle interaction in the first part of this work, we show that the particle velocities can be satisfactorily described using a first-order expression and assuming that the reduced viscosity remains constant. We report systematic experiments performed at different initial separation distances between particles and the use of our simple model allows the prediction of the settling behaviour and in particular the conditions for clusters formation. We thus show that particle aggregation can occur even for large initial distances between particles and within times that are small compared to the time scales in Newtonian fluids. Received 10 July 2002 RID="a" ID="a"e-mail: talini@fast.u-psud.fr     

Large supramolecular structures in water-alcohol mixtures evidenced by elastic light scattering

Summary We report the results of different light scattering experiments, both elastic and quasi-elastic, performed as a function of temperature at different concentrations on a water-butoxyethanol (C₄E₁) mixture. The comparison of the obtained data with the results of SANS gives evidence of the amphiphilic character of the alcohol molecules. In particular, we observe such a property gives rise to a well-defined micellarlike structure. At low temperatures (T≤5°C) we find that the mixture exhibits a surprising behaviour, namely very large structures (of the order of 2000 ?) built by an intermicellar aggregation process. In addition when the light scattering data show the presence of such large aggregates, neutron data reveal the persisting presence of micelles of about 20 ?. Such a structural picture agrees with the behaviour of the viscosity data. Due to the relevance of its scientific content, this paper has been given priority by the Journal Direction.     

Wheat starch + NaI: a high conducting environment friendly electrolyte system for energy devices

Energy storage devices are the lifeline of today’s society, and hence, researchers are trying to achieve 3Es (economical, environment friendly, and easy to prepare) along with other required technical data. Here, a new wheat starch + NaI system is synthesized which not only have good technical data such as high ionic conductivity (_˜3.61 × 10⁻² S/cm), very low dielectric relaxation time (_˜13.2 μs), and wide electrochemical stability window (_˜2.6 V) but it also satisfies 3Es conditions because it uses starch which is very cheap and abundant biopolymer available in large variety. The approximate cost of preparing 1 cm² of the sample is approximately INR 15. The prepared material is flexible, free standing film which can be easily stretched to 1.9 times to its length, and can be easily twisted up to 90°. The phase angle value approaches to −73° and maintains its value from 10 Hz to 9 kHz frequency range. The ESR value (of sample having thickness 0.48 mm and area 1.21 cm²) is very low (1.10 Ω). Parallel capacitance (C_p) to series capacitance (C_s) ratio is >0.9, and the value is maintained up to a wide frequency range (10 Hz to 10 kHz). Self-resonance frequency (the frequency limit below which energy can be stored efficiently) is also quite high (_˜0.1 MHz) for the present system. Hence, the studied system is a potential candidate for future electrochemical applications.

     

Theoretical and experimental studies of the aggregation number in the ammonium perfluorooctanoate/water binary mixture

The ammonium perfluorooctanoate/water (APFO/D₂O) system was studied by ‘ab initio’ quantum computational methods employing the 6-31 + G and 6-311 + G basis set at Hartree-Fock level. Infrared and Raman measurements were made in order to clearly understand the nature of the C–O bonds and also to verify the accuracy of the theoretical results. Small angle X-ray scattering experiments were performed for several samples at the desired surfactant weight fraction and from it the average micellar size and aggregation number were calculated using semi-empirical values for the monomer volume. These average aggregation numbers were compared with those obtained from the optimized geometry of the APFO, which showed that, for this fluorinated surfactant, there is some discrepancy between the results achieved by these two approaches. The results show that the average aggregation numbers obtained by semi-empirical methods are lower than those obtained by ab initio calculations.     

Settling Behavior Characterization of Submicron Particles in Dilute and Concentrated Suspensions

In separation processes, the knowledge of particle size and density arc often not enough to describe the settling behaviour in a concentrated suspension. Therefore, a direct method for the characterization of the settling behavior of submicron particles in concentrated suspensions is introduced in a centrifugal field by a manometric sedimentation analysis. By means of this cumulative method in a homogeneous suspension, the analyses of both the interfacial settling rate and the settling rate of the particles within the concentrated suspension are possible. This permits a differential examination of settling processes in a broad concentration range. First, the influence of the solid concentration on the settling rate at the interface and within a monodisperse suspension with a range from 0.01 to 30 vol.% is represented. The relationship between the increase in settling rate through particles settling in a cluster and a concentration decrease in the suspension is also represented. Consideration of the possibilities of the analysis of polydisperse suspensions demonstrates the field of applications for this method.     

Mild synthesis of a Zn(II) metal organic polymer and its hybrid with activated carbon: Application as antibacterial agent and in water treatment by using sonochemistry: Optimization,kinetic and isotherm study

In this work, a room temperature and short method (30 min) for synthesis of nanosized rod-like metal organic polymer (MOP) has been described. Reaction of 1,4-phenylenedioxy diacetic acid with zinc salt leads to the formation of [Zn(C₁₀H₈O₆)(H₂O)₄]_n and subsequently was loaded on activated carbon following sonication and structurally characterized by FTIR, SEM, EDX and XRD analysis. The combination of this new composite with sonication was applied for rapid and efficient adsorption of Bromocresol Purple (BCP). Effects of initial BCP concentration, mass of adsorbent and sonication time on response were investigated and optimized by central composite design (CCD). Analysis of variation (ANOVA) was adapted to experimental data to find best optimum conditions which was set at 15.22 mg L⁻¹, 2.41 min, 0.02 g and 0.009 mg for initial BCP concentration, sonication time and adsorbent mass, respectively. Conduction of similar experiments at specified condition permit achievement of 98.69% removal percentage. 1,4-phenylenedioxy diacetic acid and Zn(NO3)₂.4H₂O which have applied for preparation of MOP are interesting antibacterial properties and accordingly MOP was screened in vitro for their antibacterial actively against Proteus vulgaris bacteria and experimental results reveal this MOP was able to inhibit growth of the tested bacteria. The experimental data were best fitted by pseudo-second order and Langmuir for kinetic model and the adsorption equilibrium isotherm, respectively.     

Correlation between the viscoelastic properties of a soft crystal and its microstructure

We investigate the rheological properties of a cubic fcc phase of micelles obtained by aggregation of a triblock copolymer (PEO)₁₂₇(PPO)₄₈(PEO)₁₂₇ in water as selective solvent. The resulting soft solid is submitted to a range of stresses varying from 20 to 800Pa in Couette geometry. Creep and flow behaviour can be distinguished and interpreted in terms of structural changes previously observed by SAXS under flow. Contrasting with other systems, no discontinuity in the flow behaviour is associated with the structural changes. The strong shear thinning is interpreted from the scattering data, as resulting from the nucleation of a new structure of hexagonal compact planes parallel to the Couette walls. This creates a lubricating domain in the gap, whose size grows with the applied shear rate. We argue moreover that the very existence of flow (as a steady state opposed to creep) is associated with this so-called layer-sliding structure in a fraction, however small, of the sample. Received on 4 June 1999 and Received in final form 6 September 1999     

Autonomous magnetic resonance imaging

Access to Magnetic Resonance Imaging (MRI) across developing countries ranges from being prohibitive to scarcely available. For example, eleven countries in Africa have no scanners. One critical limitation is the absence of skilled manpower required for MRI usage. Some of these challenges can be mitigated using autonomous MRI (AMRI) operation. In this work, we demonstrate AMRI to simplify MRI workflow by separating the required intelligence and user interaction from the acquisition hardware. AMRI consists of three components: user node, cloud and scanner. The user node voice interacts with the user and presents the image reconstructions at the end of the AMRI exam. The cloud generates pulse sequences and performs image reconstructions while the scanner acquires the raw data. An AMRI exam is a custom brain screen protocol comprising of one T₁-, T₂- and T₂*-weighted exams. A neural network is trained to incorporate Intelligent Slice Planning (ISP) at the start of the AMRI exam. A Look Up Table was designed to perform intelligent protocolling by optimizing for contrast value while satisfying signal to noise ratio and acquisition time constraints. Data were acquired from four healthy volunteers for three experiments with different acquisition time constraints to demonstrate standard and self-administered AMRI. The source code is available online. AMRI achieved an average SNR of 22.86 ± 0.89 dB across all experiments with similar contrast. Experiment #3 (33.66% shorter table time than experiment #1) yielded a SNR of 21.84 ± 6.36 dB compared to 23.48 ± 7.95 dB for experiment #1. AMRI can potentially enable multiple scenarios to facilitate rapid prototyping and research and streamline radiological workflow. We believe we have demonstrated the first Autonomous MRI of the brain.     

Ultrasonic-enhanced surface-active ionic liquid-based extraction and defoaming for the extraction of psoralen and isopsoralen from Psoralea corylifolia seeds

Recently, integrated and sustainable methods for extracting active substances from plant materials using green solvents, i.e., ionic liquids, have gained increasing attention. Ionic liquids show superiority over conventional organic solvents; however, they also exhibit negative factors and problems, such as high viscosity, poor water intermiscibility, intensive foaming and poor affinity for fat-soluble substances. The proposed method utilizes ultrasonic-enhanced surface-active ionic liquid-based extraction and defoaming (UESILED) to improve the extraction efficiency of ionic liquids. Single-factor experiments and a Box-Behnken design (BBD) were utilized to optimize the extraction procedure. The optimal conditions were as follows: extraction solvent, [C₁₀MIM]Br; ultrasonic treatment time, 28 min; ultrasonic irradiation power, 437 W; liquid–solid ratio, 10 mL/g; particle size, 60 ~ 80 mesh; ultrasonication temperature, 313 K; and [C₁₀MIM]Br solution concentration, 0.5 mol/L. In comparison with those of other reference extraction methods, the proposed method exhibited higher yields of two furocoumarins and operational feasibility. Moreover, the mechanism of UESILED was elaborated in terms of accelerating infiltration, dissolution and defoaming. The feasible and efficient ultrasonic-enhanced ionic liquid-based extraction established in this study strongly contributes to overcoming the limitations of ionic liquid solvents. The present research indicates that this improved process will be beneficial for the extraction of other fat-soluble substances and provides promising concepts and experimental data.     

Aggregation of particles settling in shear-thinning fluids

We have experimentally studied the coaxial settling of three identical non-Brownian spheres in a shear-thinning fluid at small Reynolds numbers. While settling, the particles create corridors of reduced viscosity in their wake and, if they are initially close enough to one another, they can form stable clusters. By analogy with previous results obtained on two-particle interaction in the first part of this work, we show that the particle velocities can be satisfactorily described using a first-order expression and assuming that the reduced viscosity remains constant. We report systematic experiments performed at different initial separation distances between particles and the use of our simple model allows the prediction of the settling behaviour and in particular the conditions for clusters formation. We thus show that particle aggregation can occur even for large initial distances between particles and within times that are small compared to the time scales in Newtonian fluids.     

Acoustic and optical phonons in EVOH–TiO2 nanocomposite films: Effect of aggregation

Films of an organic–inorganic nanocomposite material formed by a polymeric matrix (ethylene–vinyl alcohol copolymer—EVOH) and nanometric TiO₂ particles (ca. 10 nm) have been obtained with photo-catalytic properties in the elimination of pathogens. Optical spectroscopy experiments have been performed in order to characterize the films and evaluate their properties as a function of TiO₂ doping in the range between 0.25 and 13 wt%. Anatase TiO₂ nanoparticles seem to be well-dispersed up to 2% but aggregation for higher doping originates the two different regimes observed in the acoustic modes as well as in the optical absorption in the visible spectral range.     

Sono-hydro priming process (ultrasound modulated hydration): Modelling hydration kinetic during paddy germination

Application of ultrasound technology in modulating the hydration process during paddy germination was analyzed in this study. The effect of hydropriming (24 h) and sono-hydro priming (ultrasound priming, 12 h) on the hydration behaviour of paddies was determined at different temperatures (25–40 °C). Ultrasound pulse was applied for 10 min after every one hour for sono-hydro priming. Germination potential and microstructure analysis of treated paddies were also performed. Downward concave curve observed in hydration process of paddies indicates initial high-water absorption through diffusion process. Sono-hydro priming process showed higher hydration rate compared to hydropriming. The changes in moisture content during hydration processes fitted to theoretical (Fick's model) and empirical model (Peleg model) exhibited high regression coefficient (R² > 0.95) indicating suitability for predicting hydration behaviour in both paddies for germination. The Peleg model adequately predicted saturation moisture content and sono-hydro priming efficiently increased the water absorption rate. Effective moisture diffusivity determined from Fick's diffusion model increased for sono-hydro priming. Activation energy estimated from effective moisture diffusivity required in sono-hydro priming (E_a = 20.32 and 19.19 KJ/mol respectively) for pigmented rice and non-pigmented rice was lower than hydropriming (E_a = 27.11 and 32.15 KJ/mol respectively). Both hydration processes were endothermic and non-spontaneous inferred from thermodynamic properties. Sono-hydro priming exhibited < 95% germination potential with shorter soaking time (12 h) owing to the high mass transfer rate. SEM micrograph revealed water absorption through various micro-cavities during sono-hydro priming. Thus, sono-hydro priming potentially reduced the soaking process (approximately 50%) with higher germination rate in paddies beneficial for commercial malting of grains.