Small Angle Neutron Scattering Technique Research Articles

Spin wave stiffness and damping in a frustrated chiral helimagnet Co8Zn8Mn4 as measured by small-angle neutron scattering

Multiple intriguing low-temperature phenomena have recently been discovered in the family of chiral cubic Co-Zn-Mn compounds with a $\ensuremath{\beta}$-Mn-type structure. In particular, ${\mathrm{Co}}_{8}{\mathrm{Zn}}_{8}{\mathrm{Mn}}_{4}$ displays a reduction of the helical spiral pitch on cooling along with lattice shape transformations of metastable skyrmions and the manifestation of peculiar magnetic textures due to strong magnetocrystalline anisotropy. Here we report on temperature-dependent measurements of helimagnon excitations in the field polarized regime ${\mathrm{Co}}_{8}{\mathrm{Zn}}_{8}{\mathrm{Mn}}_{4}$ using the spin-wave (SW) small-angle neutron-scattering technique. By applying a new analytical expression to interpret the data, quantitative estimates for both SW stiffness and damping are extracted across a wide temperature range between 70 and 250 K. We speculate that their nontrivial temperature dependencies arise due to the effects of magnetic frustration arising from Mn magnetic moments, which is further reflected in continuous variations of both exchange and Dzyaloshinskii-Moriya interactions.

Neutron scattering in photosynthesis research: recent advances and perspectives for testing crop plants

The photosynthetic performance of crop plants under a variety of environmental factors and stress conditions, at the fundamental level, depends largely on the organization and structural flexibility of thylakoid membranes. These highly organized membranes accommodate virtually all protein complexes and additional compounds carrying out the light reactions of photosynthesis. Most regulatory mechanisms fine-tuning the photosynthetic functions affect the organization of thylakoid membranes at different levels of the structural complexity. In order to monitor these reorganizations, non-invasive techniques are of special value. On the mesoscopic scale, small-angle neutron scattering (SANS) has been shown to deliver statistically and spatially averaged information on the periodic organization of the thylakoid membranes in vivo and/or, in isolated thylakoids, under physiologically relevant conditions, without fixation or staining. More importantly, SANS investigations have revealed rapid reversible reorganizations on the timescale of several seconds and minutes. In this paper, we give a short introduction into the basics of SANS technique, advantages and limitations, and briefly overview recent advances and potential applications of this technique in the physiology and biotechnology of crop plants. We also discuss future perspectives of neutron crystallography and different neutron scattering techniques, which are anticipated to become more accessible and of more use in photosynthesis research at new facilities with higher fluxes and innovative instrumentation.

Aggregation States of Aβ1-40, Aβ1-42 and Aβp3-42 Amyloid Beta Peptides: A SANS Study.

Aggregation states of amyloid beta peptides for amyloid beta A to A and Ap are investigated through small angle neutron scattering (SANS). The knowledge of these small peptides and their aggregation state are of key importance for the comprehension of neurodegenerative diseases (e.g., Alzheimer’s disease). The SANS technique allows to study the size and fractal nature of the monomers, oligomers and fibrils of the three different peptides. Results show that all the investigated peptides have monomers with a radius of gyration of the order of 10 Å, while the oligomers and fibrils display differences in size and aggregation ability, with Ap showing larger oligomers. These properties are strictly related to the toxicity of the corresponding amyloid peptide and indeed to the development of the associated disease.

Necklace-like microstructure in shallow-quenched aqueous solutions of poly(n-isopropylacrylamide), detected by advanced small-angle neutron scattering methods.

The microstructure of aqueous poly(N-isopropyl acrylamide) (PNIPA) gel and solution was investigated by small-angle neutron scattering (SANS) in the vicinity of the gel volume phase transition at TV (= 34 °C). The SANS technique was reinforced by refractive neutron lenses and perfect single crystals in order to get access to μm length scales. At 31 °C SANS shows Ornstein-Zernike (OZ) type scattering in the swollen gel which at 32 °C starts to deviate from the OZ-formalism, exhibiting excess scattering and at the wave number qc≅ 5 × 10-3Å-1 a crossover to Porod's asymptotic q-4 power law. For shallow quenches of ΔT < 1.0 K above TV the excess scattering intensity is further increasing whereas qc is shifting toward lower values. Based on this observation and analysis of the SANS q-profiles, we propose a necklace-like microstructure consisting of PNIPA-rich globules of R≅ 100 Å size which are connected by swollen PNIPA chains and stabilized for more than a day by pinning of chain connectivity. The formation of PNIPA globules near TV is discussed in terms of partially cooperative dehydration which is crucial to explain the "miscibility square phase behavior" of aqueous PNIPA solutions. Globule-like structure was also found in aqueous PNIPA solution of size slightly larger than in gels. At deeper quenches of gels above TV (ΔT > 1.0 K) the globules are aggregating to larger objects of R≅ 0.24 μm size as determined from a strong intensity upturn in the small q-region of USANS.

Structural and molecular response in cyclodextrin-based pH-sensitive hydrogels by the joint use of Brillouin, UV Raman and Small Angle Neutron Scattering techniques

The response to pH variation of polymeric cyclodextrin-based hydrogels has been investigated by a multi-technique approach based on UV Raman and Brillouin light scattering (BLS) together with Small Angle Neutron Scattering (SANS). By exploiting the complementary information of these three investigation methods, the structural, viscoelastic and molecular modifications of the polymer brought about by the pH changes have been examined, over a spatial range going from mesoscopic to nanoscopic length-scale. The data provide a picture where an increase of pH promotes the change of the characteristic size of the hydrophilic pores when the cross-linker has the suitable structural and acid-base properties, and leads to the reinforcement of the polymer domains interconnections, providing a stiffer gel network on the length-scale probed by BLS. Raman signals are sensitive both to structural changes of the polymer network and to changes of the intermolecular ordering of water due to solvent-polymer interactions. The destructuring effect on the tetrahedral ice-like configurations of water is especially evident at high pH, and might be ascribed to an increased exposition to the solvent of the ionic portions of the polymer surface.

Crystallographic characterization of fluorapatite glass-ceramics synthesized from industrial waste

A series of phase transformations of a novel fluoroaluminosilicate glass forming a range of fluorapatite glass-ceramics on sintering are reported. The sintering process induces formation of fluorapatite, mullite, and anorthite phases within the amorphous silicate matrices of the glass-ceramics. The fluoroaluminosilicate glass, SiO2–Al2O3–P2O5–CaO–CaF2, is prepared from waste materials, such as rice husk ash, pacific oyster shells, and disposable aluminium cans. The thermally induced crystallographic and microstructure evolution of the fluoroaluminosilicate glass towards the fluorapatite glass-ceramics, with applications in dental and bone restoration, are investigated by powder X-ray diffraction and small-angle neutron-scattering techniques.

Technological Analysis of Sicilian Prehistoric Pottery Production through Small Angle Neutron Scattering Technique

The Middle Bronze Age in Sicily (15th-13th century BC) represents a crucial moment in the evolution of Prehistoric pottery production. However, the scarcity of specific petrographic and chemical studies has represented until now a serious interpretative handicap for archaeologists. The recent study of an important Middle Bronze Age pottery complex from the site of Grotte di Marineo (Licodia Eubea, Catania), offers the possibility to add new significant data in this field. The analyses, carried out on a group of diagnostic samples represent 13% of the whole complex. This allowed us to obtain a precise characterization that surpassed the misleading identification based on the simple autoptic exam. In this context, this paper highlights the potentiality of the small angle neutron scattering (SANS) technique as a non-invasive analytical tool for the study of technological aspects, in conjunction with other, more usual, methodologies such as scanning electron microscopy (SEM), in order to better investigate production technology of Middle Bronze Age Sicilian pottery.

Characterization of oligomerization of a peptide from the ebola virus glycoprotein by small-angle neutron scattering

Transmission electron microscopy (TEM) and small-angle neutron scattering (SANS) studies showed that model peptides QNALVCGLRQ (G33) and QNALVCGLRG (G31) corresponding to region 551–560 of the GP protein of the Sudan Ebola virus are prone to oligomerization in solution. Both peptides can form amyloid-like fibrills. The G33 peptide forms fibrils within one day of incubation, whereas the fibrillogenesis of the G31 peptide is observed only after incubation for several months. The possible role of the observed processes in the pathogenesis and the possibility of applying a combination of the TEM and SANS techniques to search for new compounds that are able to influence the protein oligomerization are discussed.

Small-Angle Neutron Scattering investigation of cholesterol-doped DMPC liposomes interacting with β-cyclodextrin

The Small-Angle Neutron Scattering technique has been applied to characterize the influence of a randomly methylated β-cyclodextrin, called RAMEB, on dimyristoylphosphatidylcholine (DMPC) liposomes doped with cholesterol. From the modelling of the experimental neutron scattering cross sections, the detailed response of the vesicle structure upon addition of increasing amounts of RAMEB up to 30 mM has been assessed. This study has been performed below and above the DMPC bilayer phase transition temperature and shows that cholesterol extraction by RAMEB is linked to a decrease of the average radius and of the aggregation number of the vesicles. This extraction takes place in a dose-dependent way until a more monodisperse population of cholesterol-free liposomes is obtained. In addition, the bilayer thickness evolution was inferred, as well as the liposome coverage by RAMEB.

Interfacial and aggregation behavior of aqueous mixtures of imidazolium based surface active ionic liquids and anionic surfactant sodium dodecylbenzenesulfonate

Abstract The present work aims to study the interactions of cationic surface active ionic liquids (SAILs), 1-alkyl-3-methylimidazolium chloride, ([C n mim][Cl], where n = 8, 10 and 12) with anionic surfactant, sodium dodecylbenzenesulfonate (SDBS) in aqueous medium employing various state of art techniques such as tensiometry, steady-state fluorescence, dynamic light scattering (DLS) and small angle neutron scattering (SANS). Tensiometric and steady-state fluorescence measurements have revealed the presence of strong synergistic interactions prevailing between the oppositely charged SDBS and SAILs. Using DLS and SANS techniques, the self organization behavior of SDBS-SAIL mixtures at different mixing ratios has been investigated. The results confirmed the presence of micelles/vesicles or micelles and vesicles together at different mixing ratios of the components. Further, the aqueous mixed systems have been utilized as structure orienting templates for the preparation of Ag nanoparticles via reduction of AgNO 3 employing sodium borohydride. The prepared nanoparticles have been characterized by Scanning electron microscopy (SEM), DLS and UV–vis spectroscopic techniques where the composition of the mixed micelles has been found to affect the morphology of formed Ag nanoparticles, remarkably.

Model for neutron total cross-section at low energies for nuclear grade graphite

At subthermal neutron energies, polycrystalline graphite shows a large total cross-section due to small angle scattering processes. In this work, a new methodology to determine pore size distributions through the neutron transmission technique at subthermal energies is proposed and its sensitivity is compared with standard techniques. A simple model based on the form factor for spherical particles, normally used in the Small Angle Neutron Scattering technique, is employed to calculate the contribution of small angle effect to the total scattering cross-section, with the width and center of the radii distributions as free parameters in the model. Small Angle X-ray Scattering experiments were performed to compare results as a means to validate the method. The good agreement reached reveals that the neutron transmission technique is a useful tool to explore small angle scattering effects. This fact can be exploited in situations where large samples must be scanned and it is difficult to investigate them with conventional methods. It also opens the possibility to apply this method in energy-resolved neutron imaging. Also, since subthermal neutron transmission experiments are perfectly feasible in small neutron sources, the present findings open new possibilities to the work done in such kind of facilities.

Study of creep cavitation in stainless steel weldment

A study of creep cavities near reheat cracking in AISI Type 316H austenitic stainless steel headers, removed from prolonged high temperature operation in nuclear power plants, is reported. It is shown how application of scanning electron microscopy (SEM), cryogenic fractography and small angle neutron scattering (SANS) can be applied, in a complementary way, to observe and quantify creep cavitation. Creep cavities in the vicinity of the crack are found to be mainly surrounding inter-granular carbides. Trends in the size and area fraction of creep cavities relative to the crack path are quantified using optimised metallography. The SANS technique is found to be a very suitable method of quantifying creep cavitation within the size range up to 600 nm averaged over a larger gauge volume. It is shown that the cavity size distribution peaks in the region 100–300 nm, and this correlates closely with the quantitative SEM observations.

Adsorption of a jet fuel on a model organic–clay soil: Application of small angle neutron scattering

Small angle neutron scattering (SANS) data are reported from a system that models the contamination of a clay–organic matter soil from a fuel spillage. The soil was represented as an aqueous dispersion of the synthetic clay mineral Laponite coated with lysine, and the contaminant was a representative jet fuel, quadricyclane, mixed with the detergent cetyltrimethylammonium bromide (CTAB). The adsorbed surface coverage on the clay was estimated. It is shown that the presence of adsorbed lysine considerably enhances the subsequent adsorption of both CTAB and quadricyclane. It is demonstrated that the SANS technique can contribute to the general problem of environmental remediation and retention by probing the interactions of pollutants and clay surfaces.

中性子小角散乱法とその材料開発へのインパクト

中性子小角散乱法とその材料開発へのインパクト

The Nucleosome Revisited: Combined Small-Angle X-Ray/Neutron Scattering and Molecular Dynamics Applied to Reconstituted Mononucleosomes

Nucleosomes are the fundamental structural units of chromatin. A mononucleosome is comprised of 147 base pairs of DNA wrapped around a heterooctameric core of histone proteins that include H2A, H2B, H3, and H4, and other naturally occurring functional variants. In the mid-1970s, the SANS technique was key to the determination of the composition, structure, and conformation of the DNA within this basic unit, fifteen years before the first x-ray diffraction results were available. Small-angle scattering is a long-established technique that is well-suited for the study of macromolecules in vitro, as they exist in solution. Small-angle neutron scattering (SANS) is ideally suited to study nucleoprotein complexes, since the neutron scattering strengths of the different macromolecules differ with respect to each other. By employing contrast variation techniques, where the D2O:H2O ratio of the solutions is systematically varied, the gross structure and distribution of the individual components of a composite particle can be resolved in a model-independent fashion.We will present work which revisits these decades-old canonical measurements with a modern perspective. Experimental neutrons from beam line CG-3 at the ORNL High-Flux Isotope Reactor (HFIR) were successfully utilized to study reconstituted mononucleosomes by contrast variation. Our work marries this method with analytical centrifugation and the atomistic modeling approaches implemented in the program SASSIE. This approach allows us to directly reconcile available atomic structures with their solution properties, resulting in complete single and ensemble solution models. As a result of this work, we will present new insights into the distribution of the protein and DNA components of the mononucleosome in solution, including the properties of histone tails in solution and DNA wrapping. The methods presented provide an experimental framework for future examination of variant nucleosome and nucleosome-derived higher order assemblies.

Investigation of metal-matrix composite containing liquid-phase dispersion

Al-Pb binary system is a suitable model system for testing liquid phase dispersion strengthening in bulk materials for structural applications. Liquid Pb islands can be finely dispersed in still solid Al matrix due to the substantial difference of melting points. The Al-Pb system prepared by means of Equal Channel Angular Pressing (ECAP) process was investigated by Small-Angle Neutron Scattering technique (SANS) which enables in-situ measurement of size and morphology parameters of Pb inclusions at elevated temperatures. It was observed that the lead particles were elongated roughly in the direction of ECAP. During the subsequent in-situ thermal cycle RT-400°C-RT, the elongated Pb particles transformed to nearly spherical shape. The change of scattering contrast during melting of Pb mapped the transform of the confined lead particles to the liquid phase. The center of the transition region is around 342°C (615K) for both the as-cast and the ECAP deformed samples, which is a significant shift with respect to the free Pb melting point 327°C (600K). For the ECAP sample, the transition is not sharp, indicating a broad size distribution of lead particles.

Monitoring phase behavior of hydrogen confined in carbon nanopores byin-situSmall Angle Neutron Scattering technique

ABSTRACTWe report on the use ofin-situsmall angle neutron scattering (SANS) technique to study the phase behavior of hydrogen confined in narrow pores of ultramicroporous carbon (UMC) with a very large surface area (2630 m2/g) and pore volume (1.3 cm3/g). The effect of pore size and pressure on hydrogen adsorbed on UMC at room temperature and pressures up to ∼200 bar were investigated. In a previous experiment, we have measured the density of adsorbed H2gas in the nanopores and mesopores of polyfurfuryl alcohol-derived activated carbon (PFAC) by SANS technique. Here, a comparative SANS study between the UMC and PFAC was conducted in order to further investigate the densification of H2as a function of pore size and pressure. Initial results suggest that the density of confined H2in both UMC and PFAC is considerably higher than that of the bulk hydrogen gas. The density is systematically higher in the narrow pores and decreases with increasing pore size. These results clearly demonstrate the advantage of adsorptive storage over compressed gas storage and emphasize the greater efficiency of micropores over mesopores in the adsorption process, which can be used to guide the development of new carbon adsorbents tailored for maximum H2storage capacities at near-ambient temperatures.

Asymmetric distribution of cone-shaped lipids in a highly curved bilayer revealed by asmall angle neutron scattering technique

We have investigated the lipid sorting in a binary small unilamellar vesicle (SUV)composed of cone-shaped (1,2-dihexanoyl-sn-glycero-3-phosphocholine: DHPC) andcylinder-shaped (1,2-dipalmitoyl-sn-glycero-3-phosphocholine: DPPC) lipids. In order toreveal the lipid sorting we adopted a contrast matching technique of small angle neutronscattering (SANS), which extracts the distribution of deuterated lipids in the bilayerquantitatively without steric modification of lipids as in fluorescence probe techniques.First the SANS profile of protonated SUVs at a film contrast condition showed that SUVshave a spherical shape with an inner radius of 190 Å and a bilayer thickness of 40 Å. The SANSprofile of deuterated SUVs at a contrast matching condition showed a characteristicscattering profile, indicating an asymmetric distribution of cone-shaped lipids in thebilayer. The characteristic profile was described well by a spherical bilayer model.The fitting revealed that most DHPC molecules are localized in the outer leaflet.Thus the shape of the lipid is strongly coupled with the membrane curvature.We compared the obtained asymmetric distribution of the cone-shaped lipids inthe bilayer with the theoretical prediction based on the curvature energy model.

Macroscopic and microscopic structural integrity in magnetic colloids—cationic micellar solution: Rheology, SANS and magneto-optical study

A stable mixture of two colloid system composed of double surfactant coated aqueous nanomagnetic fluid and aqueous micellar solution of cationic micelles of cetyletrymethyl ammonium bromide (CTABr) is prepared as a function of nanomagnetic fluid concentration. This mixed system is analyzed using three techniques such as zero field and field induced viscosity measurements, Small Angle Neutron Scattering technique and magneto-optical birefringence measurements. In field induced viscosity measurement it is observed that even 20% magnetic fluid concentration in CTABr aqueous solution shows 75% increase in viscosity compared to pure magnetic fluid. This suggests that in presence of CTABr micelles, a novel magneto rheological effect for low concentration of magnetic fluid is observed. From SANS measurements it is observed that aggregation number and a/b ratio increases with magnetic fluid concentration and magnetic birefringence reveals non-superimpose behavior of normalized field induced retardation. Results of these experiments are compared and indicate zero fields and field induced structural integrity between magnetic particles and soft micelles.

Milk Gelation Studied with Small Angle Neutron Scattering Techniques and Monte Carlo Simulations

The sol-gel transition of fat-free milk by acidification was studied with neutron scattering experiments and Monte Carlo simulations. Spin-echo small angle neutron scattering (SESANS) and ultrasmall angle neutron scattering (USANS) experiments were performed to measure the static structure of milk and yogurt, as well as the aggregation kinetics. Colloidal gelation was simulated from a reaction limited domain (RLCA) to the diffusion limited regime (DLCA) as cluster-cluster aggregation of adhesive, hard spheres on a three-dimensional lattice. Comparisons were drawn between experimental and numerical correlation functions. Milk was modeled as a suspension of casein micelles in water, and its structure was described with a dilute system of solid spheres with a log-normal distribution of sizes. The structure and formation of yogurt were described with a self-affine model, used for systems containing heterogeneities with a wide range of sizes. Simulation speed was increased by 1 order-of-magnitude using a new algorithm to eliminate dead time. Observations by SESANS and USANS of milk particle sizes and yogurt length scales were consistent and agreed well with literature. Kinetic USANS data yielded reliable information about the growth of typical length scale during aggregation. The simulation model predicted the measurement data qualitatively best staying close to the RLCA regime until large structures had formed. Correlation lengths were in good quantitative agreement, but longest simulated length scales were a of factor 2(1)/(2) below experimental findings. We conclude that small, mobile aggregates are formed during the first 3 h, mostly influencing the dimensionality of the system and that large, inert structures are formed from 2 up to 8 h, which determine the typical length scale.