Method Of Small-angle Neutron Research Articles

An integrated pore size distribution measurement method of small angle neutron scattering and mercury intrusion capillary pressure

Small-angle neutron scattering and high-pressure mercury intrusion capillary pressure testing are integrated to analyze the pore size distribution of the broad sense shale oil reservoir samples of the Permian Lucaogou Formation in the Jimsar Sag, Junggar Basin, China. The results show that, compared with the measurement method integrating gas adsorption and mercury intrusion, combination of small-angle neutron scattering and mercury intrusion can more accurately characterize full-scale pore size distribution. The full-scale pore size distribution curve of the rock samples in the study area includes two types: the declining type and submicron pore-dominated type. The declining type is mainly found with silty mudstone and dolomitic mudstone, and most of its pores are smaller than 80 nm. Silt-fine sandstones and dolarenite are mostly of the submicron pores-dominated type, with most pores smaller than 500 nm. They also present large specific pore volumes and average pore diameters of macropores and are the favorable lithogenous facies for development of high-quality reservoirs.

Дослідження структурних особливостей взаємодії S-протеїну SARS-CoV-2з ліпідними мембранами методом малокутового розсіяння нейтронів

The effect of SARS-CoV-2 coronavirus S-protein on the structural parameters of the model lipid membrane on dimyristoylphosphatidylcholine (DMPC) systems with cholesterol and melatonin impurities was studied by the method of small angle neutron scattering. It is shown that an increase in the concentration of melatonin in the lipid membrane leads to a decrease in the thickness of the lipid bilayer, and an increase in the concentration of cholesterol leads to an increase in it. It has been suggested that increasing the concentration of melatonin in the membrane prevents the interaction of coronaviral S-protein with the lipid membrane of the cell. In the presence of cholesterol impurities in the system, the interaction of the lipid membrane with the active part of the S-protein occurs depending on the phase state of the lipid. Thus, when the lipid is in the gel phase (at 10 ° C), the active part of the S-protein does not change the structural parameters of the lipid bilayer, i.e. the interaction between the lipid membrane and the active part of the S-protein does not occur. At 37 ° C, when the lipid is in the liquid crystalline phase, the addition of RBD SARS-CoV-2 in the system DMPC / 30% Cholesterol / D2O leads to a decrease in membrane thickness, indicating the interaction of S-protein with the membrane.

Structural characterization of semi-heusler/light metal composites prepared by spark plasma sintering

A composite of powders of semi-Heusler ferromagnetic shape memory and pure titanium was successfully prepared by spark plasma sintering at the temperature of 950 °C. Sintering resulted in the formation of small precipitates and intermetallic phases at the heterogeneous interfaces. Various complementary experimental methods were used to fully characterize the microstructure. Imaging methods including transmission and scanning electron microscopy with energy dispersive X-ray spectroscopy revealed a position and chemical composition of individual intermetallic phases and precipitates. The crystalline structure of the phases was examined by a joint refinement of X-ray and neutron diffraction patterns. It was found that Co38Ni33Al29 decomposes into the B2-(Co,Ni)Al matrix and A1-(Co,Ni,Al) particles during sintering, while Al, Co and Ni diffuse into Ti forming an eutectic two phase structure with C9-Ti2(Co,Ni) precipitates. Complicated interface intermetallic structure containing C9-Ti2(Co,Ni), B2-(Co,Ni)Ti and L21-(Co,Ni)(Al,Ti) was completely revealed. In addition, C9-Ti2(Co,Ni) and A1-(Co,Ni,Al) precipitates were investigated by an advanced method of small angle neutron scattering. This study proves that powder metallurgy followed by spark plasma sintering is an appropriate technique to prepare bulk composites from very dissimilar materials.

Nano-level management of calcium silicate-hydrate nanoparticles structure formation during portland cement hydration process

Cement-containing building materials durability depends both on the original clinker composition and on the structure of hydrated portland cement compositions on micro and nanoscales. To calculate structural parameters of silicate-hydrate calcium nanoparticles during portland cement hydration process, the researchers applied the method of small-angle neutron scattering which included distribution of nanoparticles in size, medium nanoparticles radius, fractal dimension. Modifying nanoparticles blending with portland cement composition affects structural parameters of silicate-hydrate calcium nanoparticles. The authors used complex modifying nanoparticles in this study. Nanoparticle composition included a component that served as a filler and a chemically active component that was used as a modifier. The first component was a mixture of alpha oxide aluminum, gamma oxide aluminum and carbonate sludge. The second component presented a mixture of alumoalkaline sludge with alumocalcite sludge. These sludges were of technogenic origin. The research showed that application of complex nanoagents made it possible to control process of silicate-hydrate calcium nanoparticles structure formation, and, as the result, to influence durability of cement stone.

Investigation of Hydrated Portland Cement Structure Formation by Means of Small Angle Neutron Scattering

Investigation of the process of structure formation of samples of hydrated cement compositions on the nano level is conducted with the help of the method of small angle neutron scattering (neutron wavelength is λ=0.3nm) both on the basis of Portland cement without additives and that modified by various nanoadditives and nanomodifiers of artificial (alpha aluminium oxide, gamma aluminium oxide) and technogenic (sludge) origin, as well as by complex additives containing surfactants. Dynamics of changes of structural parameters of samples of cement compositions depending on time is analyzed. Changes of correlation functions of scattering objects and fractal dimensions are observed. It is substantiated that Portland cement compositions are fractal clusters.

Effect of fullerene C60 branching center on the conformational properties of arms and the structure of star-shaped polystyrenes in solutions

The effect of the fullerene C60 branching center on the structure and conformation of star-shaped polystyrenes with different arm lengths at equal concentrations in deuterotoluene (c = 1 g/dL) is studied by the method of small-angle neutron scattering. The analysis of neutron scattering for linear PS precursors and stars (the molecular masses of arms are ∼7 × 103 and ∼4 × 104) shows that the stars have ∼6 arms that form a dense excluded-volume zone around a core inaccessible to other macromolecules. In low-molecular-mass stars (the molecular mass of the arm is ∼7 × 103), strengthening of the static rigidity of arms is observed; as a result, the size of arms increases relative to the size of free PS chains in a good solvent. At a greater length of arms (M ∼ 4 × 104), their individual properties are weakly pronounced in the correlation spectrum of the arm because of the interpenetration of arms, thereby demonstrating similarity in the structures of stars and their linear analogs. The mechanism controlling the effect of fullerene C60 on the conformations of stars via solvent structuring by fullerene is discussed.

Investigation of polymer hydrogels with memory effect for cefazolin immobilization by small-angle neutron scattering

The method of small-angle neutron scattering has been used for the investigation of hydrogels synthesized on the basis of a cross-linked copolymer of 2-hydroxyethyl methacrylate and functional monomers (acrylic acid or dimethylaminoethyl methacrylate) which possess the memory effect with respect to the target pharmaceutical substance — cefazolin. The difference in the structure of anionic, cationic and amphiphilic hydrogels has been shown as well as the relation between the structure and the ability of a hydrogel for water sorption in the presence and in the absence of cefazolin. Certain structural features of the hydrogels confirmed the conditions for the appearance of the memory effect for the sorption and liberation of cefazolin.

Specific Features of the Distribution of Modifying Fullerene Additives in Ultrathin Polymeric Films

Nanocomposites of polyblock polysiloxane copolymers and fullerenes by the method of small-angle neutron scattering are investigated. It was shown that a uniform distribution of threshold additive of fullerenes in ultrathin polymeric films is possible. The main results of the investigation involve: (1) in the range of radiuses below 70 nm in the films there are observed scattering structures with radiuses ∼5 nm, ∼35 nm, and ∼60 nm; (2) in the sample free of fullerene, structures of radius ∼60 nm are not detected; (3) structures of radius 60 nm appear only in the samples, which contain fullerenes, therewith their part grows with the increase of the fullerenes content. In the work was suggested, that the critical role in formation C60 clusters is played by the supramolecular organization of the initial block.

Determination of the aggregation number of hydrophobic domains in a microphase-separated gel of hydrophobically modified polyacrylic acid

Hydrophobic association in a microphase-separated hydrogel of hydrophobically modified polyacrylic acid is studied by methods of small-angle neutron scattering and fluorescent spectroscopy with the use of pyrene as a probe substance. A fluorescence quenching technique is developed for determining the aggregation numbers of hydrophobic domains in weakly swollen polymeric gels. It is shown that the introduction of charged units into the gel leads to a decrease in the domains’ aggregation number because of the electrostatic repulsion of similarly charged units on their surface.

Observation of Concentration Fluctuations in Polymer Gels Performed by Neutron Spin Echo

We applied these methods of small-angle neutron scattering (SANS) and neutron spin echo (NSE) on a swollen poly ( N -isopropyl acrylamide) (NIPA) gel in order to observe the elastic scattering of frozen concentration fluctuations due to crosslinks. We successfully obtained the structure factor for the frozen concentration fluctuations in a q -domain of q >0.01 A m 1 , while in a q -domain of q <0.01 A m 1, this attempt failed due to the limited performance of the q -resolution and the Fourier time t F of the current specifications of the NSE spectrometers. This technical hurdle for the spectrometer should be overcome on an intensified neutron source for the next generation, realizing t F of w s-order and the q -resolution down closer to 0.001 A m 1.

Critical Role of Micelles in Pancreatic Lipase Activation Revealed by Small Angle Neutron Scattering

In the duodenum, pancreatic lipase (PL) develops its activity on triglycerides by binding to the bile-emulsified oil droplets in the presence of its protein cofactor pancreatic colipase (PC). The neutron crystal structure of a PC-PL-micelle complex (Hermoso, J., Pignol, D., Penel, S., Roth, M., Chapus, C., and Fontecilla-Camps, J. C. (1997) EMBO J. 16, 5531-5536) has suggested that the stabilization of the enzyme in its active conformation and its adsorption to the emulsified oil droplets are mediated by a preformed lipase-colipase-micelle complex. Here, we correlate the ability of different amphypathic compounds to activate PL, with their association with PC-PL in solution. The method of small angle neutron scattering with D(2)O/H(2)O contrast variation was used to characterize a solution containing PC-PL complex and taurodeoxycholate micelles. The resulting radius of gyration (56 A) and the match point of the solution indicate the formation of a ternary complex that is similar to the one observed in the neutron crystal structure. In addition, we show that either bile salts, lysophospholipids, or nonionic detergents that form micelles with radii of gyration ranging from 13 to 26 A are able to bind to the PC-PL complex, whereas smaller micelles or nonmicellar compounds are not. This further supports the notion of a micelle size-dependent affinity process for lipase activation in vivo.

Spin echo studies of microemulsions

Neutron spin echo (NSE) can be employed to study the dynamics of a variety of microemulsion phases. Starting from the droplet phase, we will show what can be measured by coherent quasi-elastic neutron scattering with special emphasis on model independent information. Combining the well known contrast variation method of small angle neutron scattering (SANS) with the unique energy resolution of NSE we can separate motion which are otherwise undetectable. Combining the static and dynamical experiments, microscopical parameters like bending rigidity ( K) can be deduced via model fitting.