Integrated Calendar

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Diffusion NMR weighted NMR and MRI are very powerful techniques for investigating microscopic details about tissue architecture, either normal or in a diseased state. In addition to its traditional use in diagnosing stroke and ischemic injury in the brain, in recent years DWI has been used to diagnose various kinds of cancer, including breast, prostate and lung cancers.

In this seminar we will present an overview of a novel portable system that uses DWI to check whether the margins of excised breast tumors are tumor-free. This is extremely important both for the patient and the hospital, since it obviates the need to perform additional surgery if the subsequent pathology indicates the presence of tumor on the margin of the excised tissue, something that occurs today in up to 25% of breast-conserving surgeries.

We shall provide an overview of diffusion MRI, the unique challenges of performing MRI in or near the operating theater, the architecture of ClearCut's system, computer simulations of its performance and an overview of the clinical results obtained to date.

Some fundamental concepts of catalysis are as of yet not fully explained but are of paramount importance for the development of improved supported metal catalysts for chemical industries and environmental remediation. Structure (in)sensitivity is such a fundamental physical concept in catalysis, which relates the rate of a catalytic reaction per unit surface area to the size of a nanoparticle. If this rate per unit surface area changes with catalyst particle size, a reaction is termed structure sensitive. Conversely if it does not - a reaction is termed structure insensitive. Historically, many fundamental physical concepts explaining the behavior of metal nanoparticular catalysts have been formulated by studying single crystal facets with surface science techniques which has left a considerable gap in our basic knowledge of catalysts at work. By using and developing state-of-the-art operando (micro)spectroscopic techniques, inter alia operando high-temperature high-pressure FT-IR, in-situ high-resolution STEM, and quick-X-ray absorption spectroscopy (quick-XAS) with millisecond time resolution, over the last few years I have been exploring the fundamental physical concepts behind fundamental structure-activity relationships of catalytic reactions by studying non-model catalysts at work.
For example, by applying these methods to study a structure sensitive reaction (carbon dioxide hydrogenation) to a structure insensitive one (ethene hydrogenation) we show that the same geometric and electronic effects that we find to explain structure sensitivity make it unlikely for structure insensitivity to exist (while we do observe it empirically). However, interestingly, in the case of the structure insensitive ethene hydrogenation reaction, such size-dependent nanoparticle restructuring effects as the decrease of the reversibility of adsorbate-induced restructuring and the increase of carbon diffusion with increasing particle size are observed by quick-XAS (see Figure 1). While for the structure sensitive CO2 hydrogenation no such perturbation was observed. We further show that this particle size dependent restructuring induced by ethene hydrogenation can make a structure sensitive reaction structure insensitive. Hence, we may postulate that structure insensitive reactions should rather be termed apparently structure insensitive, which changes our fundamental understanding of the age-old empirical observation of structure insensitivity.

Metallic quantum critical phenomena are believed to play a key role in many strongly correlated materials, including high temperature superconductors. Theoretically, the problem of quantum criticality in the presence of a Fermi surface has proven to be highly challenging. However, it has recently been realized that many models used to describe such systems are amenable to numerically exact solution by quantum Monte Carlo (QMC) techniques, without suffering from the fermion sign problem. I will review the status of the understanding of metallic quantum criticality, and the recent progress made by QMC simulations. The results obtained so far will be described, as well as their implications for superconductivity, non-Fermi liquid behavior, and transport in the vicinity of metallic quantum critical points. Some of the outstanding puzzles and future directions are highlighted.