Talks by colleagues in Berlin and ESRF

Today I’d like to announce two talks which are to take place next week: one by Dr. Heinrich Stuhrmann, which will be held here at BAM, and one by Ingo Bressler at ESRF.

If you went to the SAS2015 conference in Berlin, you might have already seen both presenters in action. However, the smaller setting here allows for much better interaction with the speakers, and so I would highly recommend dropping in on either of the talks if you are in Germany or France!

The lecture by Dr. Stuhrmann will be held on Monday the 5th of September, at 10:00 here at BAM (Unter den Eichen 87, Berlin) in Haus 1, Raum 225. The abstract reads:

The Spectroscopic Dimension in Small-Angle Scattering.
Heinrich B. Stuhrmann (heinrich.stuhrmann@orange.fr)
Anomalous small-angle X-ray scattering (ASAXS) is probably the best-known example of energy-resolved small-angle scattering. While anomalous dispersion of X-ray scattering became fashionable in single crystal work since the fifties of the last century, its use in small-angle scattering (SAS) started with the advent of X-ray synchrotron radiation sources, i.e. about three decades later. Among the numerous applications of ASAXS in materials and life sciences one of its most challenging applications at wavelengths near the K-absorption edge of phosphorus [λ=5.7 Å] will be discussed [1].
At almost the same time, a similar breakthrough happened in neutron scattering, when polarised neutrons were diffracted by dynamic polarized protons in a Nd3+ doped lanthanum magnesium nitrate crystal [2]. A unique technique, that may discriminate between nuclear spins of different Larmor frequency due their isotope or proximity to a paramagnetic centre. About ten years later, the advent of glassy frozen spin targets led to the first experiments of nuclear spin contrast variation both in polymer research and structural biology, particularly in Japan and in Europe.
The discrimination between protons close to a radical site and those of the bulk in radical proteins needed the effort of a Swiss-French-German collaboration. After a series of preparative steps, which established the existence of an isotopic and finally of a magnetic spin diffusion barrier separating close protons from the bulk in free radical molecules [3][4], the determination of radical sites in larger objects like proteins started at the dawn of this century. The method of time-resolved polarised neutron small-angle scattering from dynamic polarized protons, abbreviated as TPP, which stands for time-resolved proton polarisation, intimately connects polarised neutron scattering with EPR and NMR. The results of TPP from tyrosyl doped bovine liver catalase will be presented [5].
[1] Hütsch M. 1993 Thesis, University of Hamburg.
[2] Hayter J.B., Jenkin G.T., and White J.W., 1974 Phys. rev. Lett; 696-699.
[3] Van den Brandt B., Glättli H., Grillo I., Hautle P., Jouve H., Kohlbrecher J., Konter J. A., Leymarie E., Mango S., May ER.P., Michel A., Stuhrmann H.B., and Zimmer O. 2006 Eur. Phys. J. B 157-165.
[4] Stuhrmann H. B. 2015 Journal of Optoelectronics and Advanced Materials 17, 1417-1424.
[5] Zimmer O., Jouve H. M., and Stuhrmann H.B. 2016 IUCrJ 3, doi: 10.1107/S205225251601054X.

Ingo Bressler will give a talk about SASfit and McSAS, at ESRF. This will be on Tuesday the 6th of September at 14:00, in the Science Building Seminar Room. His talk abstract reads:

Software for small angle scattering analysis: SASfit and McSAS

– specialized solutions for particular problems

Ingo Breßler (mail@ingobressler.net)

For analysis of small angle scattering patterns the classical toolbox approach assumes scatterer models and predefined parameter distributions for possibly polydisperse systems or mixtures.

SASfit [1] is one such toolbox matured for many years and freely available ever since its first stages of development. It is well suited for the analysis of more complex systems by incorporating additional a priori

knowledge to improve the stability of a solution. But in cases of simpler systems where especially the sizes or another parameter distribution sought-after can not be known in advance, a form-free approach is needed.

In recent years the McSAS [2] program was developed which uses a Monte-Carlo algorithm for determining a free-form parameter distribution to address such kind of problems.

While one program is better suited for more sophisticated systems to analyse, the other one is geared towards form-free results and less a priori knowledge. Both programs assist the researcher in extracting meaningful results from scattering patterns of a reciprocal domain.

Representative Publications

1. Ingo Breßler, Joachim Kohlbrecher and Andreas F. Thünemann, “SASfit: a tool for small-angle scattering data analysis using a library of analytical expressions”, Journal of Applied Crystallography, 2015, 48 (5), 1587-1598, doi:10.1107/S1600576715016544 (open access)

2. Ingo Bressler, Brian R. Pauw and Andreas F. Thünemann, “McSAS: software for the retrieval of model parameter distributions from scattering patterns”, Journal of Applied Crystallography, 2015, 48 (3), 962-969, doi:10.1107/S1600576715007347 (open access)