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See detailSub-millisecond time-resolved small-angle neutron scattering measurements at NIST
Glinka, Charles; Bleuel, Markus; Tsai, Peter et al

in Journal of Applied Crystallography (2020), 53(3),

Instrumentation for time-resolved small-angle neutron scattering measurements with sub-millisecond time resolution, based on Gähler's TISANE (time-involved small-angle neutron experiments) concept, is in ... [more ▼]

Instrumentation for time-resolved small-angle neutron scattering measurements with sub-millisecond time resolution, based on Gähler's TISANE (time-involved small-angle neutron experiments) concept, is in operation at NIST's Center for Neutron Research. This implementation of the technique includes novel electronics for synchronizing the neutron pulses from high-speed counter-rotating choppers with a periodic stimulus applied to a sample. Instrumentation details are described along with measurements demonstrating the utility of the technique for elucidating the reorientation dynamics of anisometric magnetic particles. [less ▲]

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See detailSmall-angle neutron scattering (SANS) and spin-echo SANS measurements reveal the logarithmic fractal structure of the large-scale chromatin organization in HeLa nuclei
Iashina, Ekaterina G.; Filatov, Mikhail V.; Pantina, Rimma A. et al

in Journal of Applied Crystallography (2019), 52(4), 844-853

This paper reports on the two-scale fractal structure of chromatin organization in the nucleus of the HeLa cell. Two neutron scattering methods, small-angle neutron scattering (SANS) and spin-echo SANS ... [more ▼]

This paper reports on the two-scale fractal structure of chromatin organization in the nucleus of the HeLa cell. Two neutron scattering methods, small-angle neutron scattering (SANS) and spin-echo SANS, are used to unambiguously identify the large-scale structure as being a logarithmic fractal with the correlation function $\gamma$( r) $\sim$ ln( r/$\xi$). The smaller-scale structural level is shown to be a volume fractal with dimension D$ F$ = 2.41. By definition, the volume fractal is self-similar at different scales, while the logarithmic fractal is hierarchically changed upon scaling. As a result, the logarithmic fractal is more compact than the volume fractal but still has a rather high surface area, which provides accessibility at all length scales. Apparently such bi-fractal chromatin organization is the result of an evolutionary process of optimizing the compactness and accessibility of gene packing. As they are in a water solution, the HeLa nuclei tend to agglomerate over time. The large-scale logarithmic fractal structure of chromatin provides the HeLa nucleus with the possibility of penetrating deeply into the adjacent nucleus during the agglomeration process. The interpenetration phenomenon of the HeLa nuclei shows that the chromatin-free space of one nucleus is not negligible but is as large as the volume occupied by chromatin itself. It is speculated that it is the logarithmic fractal architecture of chromatin that provides a comfortable compartment for this most important function of the cell. [less ▲]

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See detailMagnetic field-dependent spin structures of nanocrystalline holmium
Szary, Philipp; Kaiser, Daniel UL; Bick, Jens-Peter et al

in Journal of Applied Crystallography (2016), 49

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See detailThe small-angle neutron scattering instrument D33 at the Institut Laue-Langevin
Dewhurst, C. D.; Grillo, I.; Honecker, Dirk UL et al

in JOURNAL OF APPLIED CRYSTALLOGRAPHY (2016), 49

The D33 small-angle neutron scattering (SANS) instrument at the Institut Laue–Langevin (ILL) is the most recent SANS instrument to be built at the ILL. In a project beginning in 2005 and lasting seven ... [more ▼]

The D33 small-angle neutron scattering (SANS) instrument at the Institut Laue–Langevin (ILL) is the most recent SANS instrument to be built at the ILL. In a project beginning in 2005 and lasting seven years, the concept has been developed, and the instrument designed, manufactured and installed. D33 was commissioned with neutrons during the second half of 2012, fully entering the ILL user programme in 2013. The scientific case required that D33 should provide a wide dynamic range of measured scattering vector magnitude q, flexibility with regard to the instrument resolution, and the provision of polarized neutrons and 3He spin analysis to facilitate and expand studies in magnetism. In monochromatic mode, a velocity selector and a flexible system of inter-collimation apertures define the neutron beam. A double-chopper system enables a time-of-flight (TOF) mode of operation, allowing an enhanced dynamic q range (qmax/qmin) and a flexible wavelength resolution. Two large multitube detectors extend the dynamic q range further, giving qmax/qmin ’ 25 in monochromatic mode and a very large qmax/qmin > 1000 in TOF mode. The sample zone is large and flexible in configuration, accommodating complex and bulky sample environments, while the position of D33 is such as to allow high magnetic fields at the sample position. The instrument is of general purpose with a performance rivalling that of D22, and is well adapted for SANS studies in scientific disciplines as diverse as solution scattering in biology and soft matter and studies of physics, materials science and magnetism. This article provides a detailed technical description of D33 and its performance and characterization of the individual components, and serves as a technical reference for users of the instrument. [less ▲]

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See detailSmall-angle neutron scattering correlation functions of bulk magnetic materials
Mettus, Denis UL; Michels, Andreas UL

in Journal of Applied Crystallography (2015), 48

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See detailAutocorrelation function of the spin misalignment in magnetic small-angle neutron scattering: application to nanocrystalline metals
Michels, Andreas UL; Bick, Jens-Peter UL

in Journal of Applied Crystallography (2013), 46

Real-space magnetic small-angle neutron scattering data from nanocrystalline cobalt and nickel have been analysed in terms of a recently developed micromagnetic theory for the autocorrelation function of ... [more ▼]

Real-space magnetic small-angle neutron scattering data from nanocrystalline cobalt and nickel have been analysed in terms of a recently developed micromagnetic theory for the autocorrelation function of the spin misalignment [Michels (2010). Phys. Rev. B, 82, 024433]. The approach provides information on the exchange-stiffness constant and on the mean magnetic ‘anisotropy-field’ radius. [less ▲]

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See detailCreating local contrast in small-angle neutron scattering by dynamic nuclear polarization
van den Brandt, B.; Glattli, H.; Hautle, P. et al

in Journal of Applied Crystallography (2007), 40(s), 106-110

Low-resolution small-angle neutron scattering measurements can benefit from polarized protons to generate scattering contrast profiles. In a recently developed technique, time-resolved polarized SANS ... [more ▼]

Low-resolution small-angle neutron scattering measurements can benefit from polarized protons to generate scattering contrast profiles. In a recently developed technique, time-resolved polarized SANS tries to make use of spatial polarization gradients created around paramagnetic centres at the onset of dynamic nuclear polarization. The time constants which describe the build-up of polarization around the paramagnetic centre and the subsequent diffusion of polarization in the solvent were determined by analysing the temporal evolution of the nuclear polarization. The possible use and the limitations of this technique as a spectroscopic tool are discussed. [less ▲]

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