Radboud University Nijmegen

About: Radboud University Nijmegen is a education organization based out in Nijmegen, Gelderland, Netherlands. It is known for research contribution in the topics: Population & Randomized controlled trial. The organization has 35417 authors who have published 83035 publications receiving 3285064 citations. The organization is also known as: Catholic University of Nijmegen & Radboud University.

Twinning superlattices in indium phosphide nanowires

Abstract: In most superconductors, the pairing-up of electrons responsible for resistance-free conductivity is driven by vibrations of the solid's crystal lattice. But there are other superconducting materials in which the 'glue' responsible for binding electrons is thought to have a very different origin: quantum fluctuations of spin or charge. An unusually 'violent' generalization of such a pairing mechanisms, in which spin and charge instabilities combine forces, has been identified in the unconventional superconductor CeRhIn5. These intimately coupled fluctuations significantly disrupt the flow of electrons in their normal unpaired state, yet also provide the quantum-mechanical glue necessary for generating superconducting pairs. In this paper, the crystal structure and stacking fault density of semiconducting nanowires composed of the same material are controlled by doping, leading to twinning superlattices. Periodic arrays of rotational dislocations lead to crystal heterostructures in indium phosphide and gallium phosphide nanowires. Semiconducting nanowires offer the possibility of nearly unlimited complex bottom-up design1,2, which allows for new device concepts3,4. However, essential parameters that determine the electronic quality of the wires, and which have not been controlled yet for the III–V compound semiconductors, are the wire crystal structure and the stacking fault density5. In addition, a significant feature would be to have a constant spacing between rotational twins in the wires such that a twinning superlattice is formed, as this is predicted to induce a direct bandgap in normally indirect bandgap semiconductors6,7, such as silicon and gallium phosphide. Optically active versions of these technologically relevant semiconductors could have a significant impact on the electronics8 and optics9 industry. Here we show first that we can control the crystal structure of indium phosphide (InP) nanowires by using impurity dopants. We have found that zinc decreases the activation barrier for two-dimensional nucleation growth of zinc-blende InP and therefore promotes crystallization of the InP nanowires in the zinc-blende, instead of the commonly found wurtzite, crystal structure10. More importantly, we then demonstrate that we can, once we have enforced the zinc-blende crystal structure, induce twinning superlattices with long-range order in InP nanowires. We can tune the spacing of the superlattices by changing the wire diameter and the zinc concentration, and we present a model based on the distortion of the catalyst droplet in response to the evolution of the cross-sectional shape of the nanowires to quantitatively explain the formation of the periodic twinning.

Patients with familial adenomatous polyposis harbor colonic biofilms containing tumorigenic bacteria

Abstract: Individuals with sporadic colorectal cancer (CRC) frequently harbor abnormalities in the composition of the gut microbiome; however, the microbiota associated with precancerous lesions in hereditary CRC remains largely unknown We studied colonic mucosa of patients with familial adenomatous polyposis (FAP), who develop benign precursor lesions (polyps) early in life We identified patchy bacterial biofilms composed predominately of Escherichia coli and Bacteroides fragilis Genes for colibactin ( clbB ) and Bacteroides fragilis toxin ( bft ), encoding secreted oncotoxins, were highly enriched in FAP patients’ colonic mucosa compared to healthy individuals Tumor-prone mice cocolonized with E coli (expressing colibactin), and enterotoxigenic B fragilis showed increased interleukin-17 in the colon and DNA damage in colonic epithelium with faster tumor onset and greater mortality, compared to mice with either bacterial strain alone These data suggest an unexpected link between early neoplasia of the colon and tumorigenic bacteria