Peace Is the Answer for Our Post-Pandemic World

Humanity is facing a series of existential threats unlike any it has experienced before in its short history. They are driven mainly by overpopulation, increasingly impactful advancements in technology, and now a pandemic. Countering these threats will require a new way of conceptualizing our relationships with each other and the ecosystems we depend on. The world needs a new approach that will allow us to adapt in the short term and reverse the decline in the long term. Peace is central to a safe and productive society. Without peace, we will never achieve the level of trust, cooperation, and inclusiveness necessary to solve the global challenges humanity faces. This article presents Positive Peace, combined with systems thinking, as a new theory of change, a new way to conceptualize how societies function, and a new approach to solving the world’s most intractable problems

On the origin of mode- and bond-selectivity in vibrationally mediated reactions on surfaces

The experimental observations of vibrational mode- and bond-selective chemistry at the gas–surface interface indicate that energy redistribution within the reaction complex is not statistical on the timescale of reaction. Such behavior is a key prerequisite for efforts to use selective vibrational excitation to control chemistry at the technologically important gas–surface interface. This paper outlines a framework for understanding the origin of non-statistical reactivity on surfaces. The model focuses on the kinetic competition between intramolecular vibrational energy redistribution (IVR) within the reaction complex, which in the long-time limit leads to statistical behavior, and quenching, scattering, or desorption processes that restrict the extent of IVR prior to reaction. Characteristic timescales for these processes drawn from studies of vibrational energy flow dynamics on surfaces and in the gas and condensed phases suggest that IVR is severely limited for important classes of surface reactions. Under these conditions, selective vibrational excitation can lead to preferential transition state access and result in mode- or bond-selective chemistry, even at high collision energies above the barrier to reaction. In addition to providing a basis for understanding experimental observations, the model provides guidance for identifying other gas–surface reactions that may exhibit mode-selective behavior

Thermally Selective Formation of Subsurface Oxygen in Ag(111) and Consequent Surface Structure

A long-standing challenge in the study of heterogeneously catalyzed reactions on silver surfaces has been the determination of what oxygen species are of greatest chemical importance. This is due to the coexistence of several different surface phases on oxidized silver surfaces. A further complication is subsurface oxygen (Osub). Osub are O atoms absorbed into the near surface of a metal, and are expected to alter the surface in terms of chemistry and structure, but these effects have yet to be well characterized. We studied oxidized Ag(111) surfaces after exposure to gas-phase O atoms to determine how Osub is formed and how its presence alters the resultant surface structure. Using a combination of surface science techniques to quantify Osub formation and the resultant surface structure, we observed that once 0.1 ML of Osub has formed, the surface dramatically, and uniformly, reconstructed to a striped phase at the expense of all other surface phases. Furthermore, Osub formation was hindered at temperatures above 500 K. The thermal dependence for Osub formation suggests that at industrial catalytic conditions of 475 – 500 K for the epoxidation of ethylene-to-ethylene oxide, Osub would be present and is a factor in the subsequent reactivity of the catalysts. These findings point to the need for the incorporation of Osub into catalytic models as well as further theoretical investigation of the resultant structure observed in the presence of Osub

Temperature-Resolved Surface Infrared Spectroscopy of CO on Rh(111) and (2 × 1)-O/Rh(111)

Heterogeneously catalyzed reactions over transition metal surfaces are pillars of chemical industry and account for a significant fraction of the global energy demand. CO oxidation provides insight into the relative reactivity of various oxygenaceous surface phases, and it is necessary to first understand where it binds to the surface and the nature of the local environment to develop robust mechanistic pictures of the reaction. Surface IR spectroscopy is a quantitative technique that also provides information about the binding sites and chemical environments of the adsorbed CO molecules. Here, we report results from a study of CO sticking to clean Rh(111) and (2 × 1)-O/Rh(111) that shows that the intensity of the IR absorption was not linear with coverage and is an important consideration for further studies of the catalytic surface

Velocity Map Images of Desorbing Oxygen from Sub-Surface States of Rh(111)

We combine velocity map imaging (VMI) with temperature-programmed desorption (TPD) experiments to record the angular-resolved velocity distributions of recombinatively-desorbing oxygen from Rh(111). We assign the velocity distributions to desorption from specific surface and sub-surface states by matching the recorded distributions to the desorption temperature. These results provide insight into the recombinative desorption mechanisms and the availability of oxygen for surface-catalyzed reactions

Molecular Interactions with Ice: Molecular Embedding, Adsorption, Detection, and Release

The interaction of atomic and molecular species with water and ice is of fundamental importance for chemistry. In a previous series of publications, we demonstrated that translational energy activates the embedding of Xe and Kr atoms in the near surface region of ice surfaces. In this paper, we show that inert molecular species may be absorbed in a similar fashion.We also revisit Xe embedding, and further probe the nature of the absorption into the selvedge. CF4 molecules with high translational energies (≥3 eV) were observed to embed in amorphous solid water. Just as with Xe, the initial adsorption rate is strongly activated by translational energy, but the CF4 embedding probability is much less than for Xe. In addition, a larger molecule, SF6, did not embed at the same translational energies that both CF4 and Xe embedded. The embedding rate for a given energy thus goes in the order Xe \u3e CF4 \u3e SF6. We do not have as much data for Kr, but it appears to have a rate that is between that of Xe and CF4. Tentatively, this order suggests that for Xe and CF4, which have similar van der Waals radii, the momentum is the key factor in determining whether the incident atom or molecule can penetrate deeply enough below the surface to embed. The more massive SF6 molecule also has a larger van der Waals radius, which appears to prevent it from stably embedding in the selvedge. We also determined that the maximum depth of embedding is less than the equivalent of four layers of hexagonal ice, while some of the atoms just below the ice surface can escape before ice desorption begins. These results show that energetic ballistic embedding in ice is a general phenomenon, and represents a significant new channel by which incident species can be trapped under conditions where they would otherwise not be bound stably as surface adsorbates. These findings have implications for many fields including environmental science, trace gas collection and release, and the chemical composition of astrophysical icy bodies in space

DNA replication roadblocks caused by Cascade Interference complexes are alleviated by RecG DNA repair helicase

Cascade complexes underpin E. coli CRISPR-Cas immunity systems by stimulating "adaptation" reactions that update immunity and by initiating "interference" reactions that destroy invader DNA. Recognition of invader DNA in Cascade catalysed R-loops provokes DNA capture and its subsequent integration into CRISPR loci by Cas1 and Cas2. DNA capture processes are unclear but may involve RecG helicase, which stimulates adaptation during its role responding to genome instability. We show that Cascade is a potential source of genome instability because it blocks DNA replication and that RecG helicase alleviates this by dissociating Cascade. This highlights how integrating in vitro CRISPR-Cas interference and adaptation reactions with DNA replication and repair reactions will help to determine precise mechanisms underpinning prokaryotic adaptive immunity