Integrated Calendar

Following the advent of graphene, many other one-atom or one-molecule thick crystals have been isolated and investigated. These two-dimensional crystals have become one of the hottest topics in materials science and condensed matter physics. Furthermore, isolated atomic planes can now be reassembled back into three-dimensional structures and crystals made layer by layer in a designer sequence. I will provide a brief, lowbrow introduction to graphene, trying to explain why this material has attracted so much attention, and then overview our progress in making new assemblies from available atomic planes in order to illustrate how rich in phenomena and application this research field is.

Rock surfaces support microbial communities that may be involved in weathering processes. In arid and hyper-arid environments microbes dominate rock surfaces and were linked to weathering because the scarcity of water excludes classical mechanisms that erode rocks. We studied subaerial biofilms coating arid rocks, focusing on sedimentary rocks that feature comparable weathering morphologies but different lithologies. We hypothesized that weathering is fashioned by salt erosion and mediated by biofilms that play dual roles: stabilizing the rock surfaces by coating, and enhancing salt crystallization by preventing rapid desiccation (thus mitigating and facilitating erosion processes, respectively). We used a combination of microbial and geological techniques to characterize the rocks morphologies and their subaerial biofilms. Deep sequencing and microscopy analyses suggest that bacterial diversity is low, dominated by Proteobacteria, Cyanobacteria and Actinobacteria. Together these phyla formed laminar biofilms that secrete extracellular polymeric substances to aggregate microfabrics and mitigate desiccation, reducing water loss by over 40%. The biofilm was detected only in rocks exposed to the atmosphere, present distinct architecture and burrowed up to 9 mm beneath the surface, protected by sedimentary deposits. A closer inspection revealed that the composition of the biofilm was tightly linked to dust bacterial communities but distinct from soil communities. Moreover, the biofilm composition changed according to the rock location rather than its’ lithology, suggesting that microclimate (dew, relative humidity and radiation) play an important role in arid weathering. Our results contradict common dogmas that considered biofilms as degrading agents and propose their role as mitigators of geomorphic processes.

Antihydrogen, the bound state of an antiproton and a positron, is the simplest atom consisting purely of antimatter. Its matter counterpart, hydrogen, is one of the best studied atomic systems in physics. Thus comparing the spectra of hydrogen and antihydrogen offers some of the most sensitive tests of matter-antimatter symmetry. Furthermore, the availability of neutral antimatter offers for the first time a precise measurement of its gravitational interaction that was so far not possible due to the dominance of the electro-magnetic interaction for charged antiparticles.

The formation and experimental investigation of antihydrogen is the main physics goal of several col-laborations at the Antiproton Decelerator of CERN. The ASACUSA collaboration is pursuing a meas-urement of the ground-state hyperfine structure of antihydrogen in an atomic beam, a quantity which was measured in hydrogen using a maser to a relative precision of 10^{-12}. The AEgIS collaboration aims at using an ultra-cold beam of antihydrogen atoms and a classical moiré deflectometer to determine the gravitational interaction between matter and antimatter in a first step to percent level precision.

After a first production of cold antihydrogen in 2002 and a first trapping in 2010 the experiments are still in the process of optimizing the antihydrogen production from trapped antiprotons and positrons. The status and prospect of these experiments will be reviewed.

In his remarkable and inspiring book “The Age of Wonder,” Richard Holmes describes the synergistic links between the sciences and humanities among (in particular) the English intellectuals in the period 1770-1830. “Natural philosophers” like Sir Humphrey Davy had regular interactions with poets like Samuel Taylor Coleridge, and authors like Mary Shelly wrote of dystopias that could result from the misapplication of science and technology. Modern intellectuals, contemplating the current clearly apparent divide between the humanities and the sciences, tend to look at this “age of wonder” through rose-colored glasses and to long for its return. But is this yearning realistic? In our increasingly complex and specialized world, can we truly expect to recover the close bond between these distinct ways of knowing the world? Can we construct an interdisciplinary technological humanism that meaningfully links the sciences and the humanities?

In this talk I attempt to provide limited and subjective answers to these questions and to describe general developments and trends that I believe may give hope that we can indeed recover the “age of wonder.”