Calculating scattering by hand – example 1

Quickgrab

Those who read the older SAXS literature will note liberal use of Fourier transforms to calculate the scattering behaviour of odd-shaped particles. Likewise, the effects of smearing due to (for example) beam shape (think “blurring” of the scattering pattern) can be easily determined using such transforms. It is useful to get a feel for the methods for derivation of such Fourier transforms, so I decided it was time to refresh my rusty Fourier transform skills. Read more »

Share

Why we never may be able to get a calibration curve: a matter of coherence

A field of random size scatterers.

For years, we have been trying to compare scattering patterns from different instruments. While this leads to reasonable results, there are precious few cases of true agreement despite the focus on data corrections (one example of agreement: [0]). My guess: we have not been considering coherence in these comparisons. Read more »

Share

Radiation safety for lab X-ray sources

Spectrum of the X-rays emitted by an X-ray tube with a rhodium target, operated at 60 kV. The smooth, continuous curve is due to bremsstrahlung, and the spikes are characteristic K lines for rhodium atoms. High energy on the left (short wavelength), low energy on the right). Image CC0 licensed from http://en.wikipedia.org/wiki/File:TubeSpectrum.jpg

Over the years, I have followed several radiation safety courses in a variety of countries. Last week, it was NIMS’ turn to train me. As this was given in Japanese (a language I can only half follow), I decided to write my own section on radiation safety instead (for future inclusion in the book). This will draw on personal experience, things I remember from previous trainings and google’d knowledge, but I am fairly sure much of this is correct. Nevertheless, it is only in draft stage, and will still require an expert check, so use this at your own discretion.

Read more »

Share

Dr. Helen E. Maynard-Casely chats about planets

Helen

What to expect on the surfaces of the more distant planets is a hard question to answer. Fortunately, we have scientists working on this problem.

At our institute, we just had the pleasure of hosting a talk by Dr. Maynard-Casely, whose mission is to add a certain amount of evidence-based level-headedness to the discussions. I will do my best to summarize the contents of her excellent and engaging talk. Read more »

Share