analysis

How to fit a scattering pattern part 2: Some simple fits

2013/11/18 // 0 Comments

Note: Part one of this three- or four-part series can be found here. Additionally, my topical review paper on SAXS data collection and correction which also lightly discusses data fitting is available open access here. After the initial “scoping out” of a collected scattering pattern, it is time to try to see what can be done in terms of fitting in step 2. Here, we are trying to see if parts of the scattering pattern might be described by some basic scattering [...]

Green catalysts from pigs!

2013/10/07 // 0 Comments

This news has also been covered by Birmingham University, Martin Hollamby and The Schnepp Group, and may appear in other news outlets soon. [update: like at azonano.com, nanowerk.com, the Mumbai mirror, FuelCellsWorks, supergen fuel cells, green car congress and phys.org. update2: Some more selected outlets: Ars Technica, the Conversation, World of Chemicals, Renewables Europe, Hydrogen and Fuel Cell letter (paywalled), and The Himalayan Mirror ] Imagine you could turn pigs into catalysts. You’d think that that would take quite some work, but it turns out to be surprisingly easy as long as you have a good oven and some salts lying around. This has been demonstrated by Zoe Schnepp (of the newly formed Schnepp Group at the U. of Birmingham) in collaboration with Yuanjian Zhang, Martin Hollamby and others during her time here at NIMS, and has just been published here. So what did we [...]

How to fit a scattering pattern part 1: the initial look.

2013/09/09 // 2 Comments

By the way, my topical review paper on SAXS data collection and correction has been published and is available open access here!   Recently, some good colleagues (who are not familiar with scattering) have started asking questions on how to go about fitting a scattering pattern. This was a very good opportunity to think about the process from a layman perspective. How do we get from scattering pattern to morphological information in a straightforward [...]

Does it matter? part 1: sample direction-dependent absorption

2011/05/06 // 5 Comments

Figure 1: Scattered radiation traveling different distances through a sample This series is part of a set to determine which corrections matter when. We all heard -or read- about corrections Small-angle Scatterers do not need to do, because they are supposedly negligible. Let’s look at some of them and determine if this is really true or not.   The first looks at the sample direction-dependent absorption. This is the effect of scattered radiation travelling a slightly different distance through the sample (and therefore experiencing different levels of absorption) depending on the direction of scattering. Take, for example, the simplest case of a sample like a plate or sheet (c.f. Figure 1). From this figure, it can easily be seen that the radiation scattering to an angle has to travel longer through the sample than radiation passing straight through. Therefore, the scattered radiation suffers from more absorption. But how much more? In this document: plate_transmission, [...]

Notes on Guinier

2011/01/02 // 2 Comments

…well, his famous SAXS analysis method. This documentGuinier_short, copyright Brian Pauw gives a short description and review of the applicability of the Guinier method to polydisperse systems. It also shows, through analysis of simulated data, what q-range should be measured for the Guinier method to be valid. In short, the rule of qmax=1.3/Rg still holds, but Rg in polydisperse systems is the volume-squared weighted Rg of the distribution. This then implies that the Guinier method for polydisperse systems quickly becomes unusable as the required qmax cannot be reached with anything but USAXS systems for polydisperse samples. This text (the linked PDF) is released under copyright (copyright by Brian R. Pauw, 2011) as I may want to include some of this in a later publication. I hope you [...]

One more paper

2010/09/16 // 0 Comments

Do not fret, for I have more software (with documentation!) lined up for presentation on this website soon, but I am still working on the documentation. Please bear with me as I shamelessly promote another publication of mine that came out just days ago. The paper is available here: http://dx.doi.org/10.1016/j.polymer.2010.07.045 It concerns curious observations of oscillations in the scattering pattern from looped single filaments of aramid filaments. As an aside, loading the 12-micron filaments into the microchannel devices is for young eyes only, and even then may be accompanied by expletives. Nevertheless, I am very happy that this is [...]