Global and local hard X‐ray tomography of a centimeter‐size tumor vessel tree

The visualization of the vascular network in tumors down to the smallest vessels requires high spatial resolution and reasonable contrast. Stained corrosion casts of the microvasculature network guarantee superior X‐ray absorption contrast and highest reproduction fidelity. Tomography of a centimeter‐size tumor, however, is unfeasible at the spatial resolution needed to reveal the smallest vessels. Therefore, local tomography has been performed to visualize the smallest capillaries within the region of interest. These three‐dimensional data show the detailed morphology, but the reconstructed absorption coefficients obtained in local tomography differ substantially from the absorption coefficients retrieved from the less detailed global tomography data. This paper deals with the adaptation of local tomography data using the global data and considers two‐parameter histogram matching of the radiographs, sinogram extension, and multi‐parameter cupping correction. It is demonstrated that two‐parameter histogram matching of the radiographs already provides reasonable agreement. The change of the lens in front of the detector's camera, however, significantly affects the obtained local X‐ray absorption coefficients in the tomograms predominantly owing to the dissimilar point‐spread functions of the two configurations used, and much less to the fact that one of the data sets was acquired in a local geometry.     

Untersuchung von Milch und Milchprodukten

Ohne Zusammenfassung     

Comment on the reported observation of the “raman spectrum of the phenoxy radical” in stopped flow experiments

Pulse radiolysis studies show that phenoxyl radical reacts at diffusion controlled rates. Concentrations on the time scale of stopped flow experiments cannot be substantially above 10^-5 M so that in the absence of resonance enhancement the Raman spectrum reported by Shindo and Hiraishi cannot be assigned to phenoxyl radical.     

A numerical study of the small-x behavior of deep inelastic structure functions in QCD

A numerical study of the Gribov-Levin-Ryskin equation for deep inelastic structure functions in the small-x regions is performed. In the first part we study a simplified version which illustrates general features of the solution and also allows to investigate certain analytic properties. In the second part we formulate a more realistic version of the GLR equation and compute its solution, for different input distributions and for different values of the strength of the nonlinearity in the GLR equation. One of the conclusions is that, provided the input distribution is not too flat and the nonlinear coupling is not too small, deviations from the standard evolution may be visible at HERA.