Distribution and orientation of nerve fibers and myelin assembly in a brain section retrieved by small-angle neutron scattering

The structural connectivity of the brain has been addressed by various imaging techniques such as diffusion weighted magnetic resonance imaging (DWMRI) or specific microscopic approaches based on histological staining or label-free using polarized light (e.g., three-dimensional Polarized Light Imaging (3D-PLI), Optical Coherence Tomography (OCT)). These methods are sensitive to different properties of the fiber enwrapping myelin sheaths i.e. the distribution of myelin basic protein (histology), the apparent diffusion coefficient of water molecules restricted in their movements by the myelin sheath (DWMRI), and the birefringence of the oriented myelin lipid bilayers (3D-PLI, OCT). We show that the orientation and distribution of nerve fibers as well as myelin in thin brain sections can be determined using scanning small angle neutron scattering (sSANS). Neutrons are scattered from the fiber assembly causing anisotropic diffuse small-angle scattering and Bragg peaks related to the highly ordered periodic myelin multilayer structure. The scattering anisotropy, intensity, and angular position of the Bragg peaks can be mapped across the entire brain section. This enables mapping of the fiber and myelin distribution and their orientation in a thin brain section, which was validated by 3D-PLI. The experiments became possible by optimizing the neutron beam collimation to highest flux and enhancing the myelin contrast by deuteration. This method is very sensitive to small microstructures of biological tissue and can directly extract information on the average fiber orientation and even myelin membrane thickness. The present results pave the way toward bio-imaging for detecting structural aberrations causing neurological diseases in future

Potential of environmental scanning electron microscopy and SAXS to determine structural insights of plant-based emulsions with increasing dry matter content

Plant-based emulsions with increasing dry matter content show a large range of structural features from atomic to macroscopic length scales, which may be examined with scattering techniques in reciprocal space and microscopic techniques in real space. In this contribution, we focus on plan-based emulsions in terms of mesoscopic structure, and report on the impact of temperature and humidity on the structure measured via environmental scanning electron microscopy (ESEM) in real space. Small angle x-ray scattering in reciprocal space extends the knowledge on structural properties on smaller length scales at different temperature. Decreasing the humidity for the ESEM experiments revealed structural properties of different products. Temperature decrease from room temperature to 5 °C showed emerging crystalline peaks during SAXS measurements

Influence of NaCl on the Structure and Dynamics of Phospholipid Layers

We present a structural and dynamical analysis of the influence of NaCl on multilayer stacks of phospholipids on a solid surface. To this end, multilayer stacks of phospholipids (L-α-phosphatidylcholine, abbreviated as SoyPC) are investigated with neutron reflectometry, grazing-incidence small-angle neutron scattering (GISANS) and grazing-incidence neutron-spin echo spectroscopy (GINSES). We show both that the NaCl influence on the structure is predominantly on water-head group interface and also, that the change in dynamics is restricted to an associated change in the inter-plane viscosity. Using this knowledge, it is possible to model the dynamical behavior of a phospholipid membrane in response to a salt concentration of the solvent using only a single parameter, namely the in-plane viscosity. The excellent agreement with our previously published model also strongly supports the existence of a thermally excited surface mode in phospholipid membranes for close-to-physiological conditions

Technical Specification of the Small-Angle Neutron Scattering Instrument SKADI at the European Spallation Source

Small-K Advanced DIffractometer (SKADI is a Small-Angle Neutron Scattering (SANS) instrument to be constructed at the European Spallation Source (ESS). SANS instruments allow investigations of the structure of materials in the size regime between Angstroms up to micrometers. As very versatile instruments, they usually cater to the scientific needs of communities, such as chemists, biologists, and physicists, ranging from material and food sciences to archeology. They can offer analysis of the micro- and mesoscopic structure of the samples, as well as an analysis of the spin states in the samples, for example, for magnetic samples. SKADI, as a broad range instrument, thus offers features, such as an extremely flexible space for the sample environment, to accommodate a wide range of experiments, high-flux, and optimized detector-collimation system to allow for an excellent resolution of the sample structure, short measurement times to be able to record the internal kinetics during a transition in the sample, as well as polarized neutron scattering. In this manuscript, we describe the final design for the construction of SKADI. All of the features and capabilities presented here are projected to be included into the final instrument when going into operation phase

Experimental critical dynamics of 3-methyl pyridine/D2_2O mixtures without and with antagonistic salt

We observed the criticality in the structure and dynamics of a 3d- and 2d-Ising system consisting of 3-methyl pyridine (3MP) / D2O without and with antagonistic salt. We could describe both dynamic criticalities by the Kawasaki crossover function. The dynamic critical exponent was z=0.063±0.020 and 0.005±0.019 for 3 and 2 dimensions, which confirms earlier observations in the 3d case and confirms expectations in the 2d case. The amplitudes of the critical dynamics are governed by the bare viscosities experimentally, and by the coefficient R theoretically (latter is proportional to (4−d)−1 with the dimensionality d). This finding is in accordance with the lubrication effect that is also connected to lamellar systems of the Brazovskii criticality . This lubrication effect is tightly connected to a laminar flow enforced by the domain structure and also holds for our 2d-Ising system. The experimental techniques employed were small angle neutron and x-rays scattering (SANS and SAXS) for the static criticality and dynamic light scattering (DLS) and neutron spin echo spectroscopy (NSE) for the critical dynamics. Furthermore, the criticality of the viscosities was measured