Mitigating risk of exceeding environmental limits requires ambitious food system interventions

Transforming the global food system is necessary to avoid exceeding planetary boundaries. A robust evidence base is crucial to assess the scale and combination of interventions required for a sustainable transformation. We developed a risk assessment framework, underpinned by a meta-regression of 60 global food system modeling studies, to quantify the potential of individual and combined interventions to mitigate the risk of exceeding the boundaries for land-system change, freshwater use, climate change, and biogeochemical flows by 2050. Limiting the risk of exceedance across four key planetary boundaries requires a high but plausible level of ambition in all demand-side (diet, population, waste) and most supply-side interventions. Attaining the required level of ambition for all interventions relies on embracing synergistic actions across the food system

CMS physics technical design report : Addendum on high density QCD with heavy ions

Peer reviewe

"Squaring the Circle" by Graham Metson, "On-Site Project"

Metson describes thematic and technical aspects of his performance/installation work. Includes reproductions of the artist's proposal as well as biographical notes on all performance participants

Immolation : Recent Figuration by Graham Metson

Rosshandler's introduction traces Metson's British roots and association with the "London School". Smart's analysis of the artist's paintings and drawings references his formative influence, use of literary sources, and exploration of the theme of violence. Artist's statement. Biographical notes. 26 bibl. ref

Characterization of the active site for the selective oxidation of methanol to formaldehyde on polycrystalline silver catalyst

Using in situ FTIR spectroscopy to compare the interaction of methyl formate and formic acid with a polycrystalline silver catalyst shows that methyl fromate is dissociatively chemisorbed on conventional silver faces such as (111) and (110) which contained nucleophilic adsorbed oxygen species while in contrast, formic acid is adsorbed not only on (111) and (110) silver planes but also on silver sites modified by the presence of subsurface oxygen; this behaviour supports a previously proposed model of the active site for the selective oxidation of methanol to formaldehyde on silver catalyst.</p

An in situ fourier transform infrared study of formic acid adsorption on a polycrystalline silver catalyst

Infrared spectra are reported for the adsorption of formic acid on a polycrystalline silver catalyst after various degrees of oxidation. Three distinct chemisorbed species were identified, two of which corresponded to adsorbed formate on Ag(110) and Ag(111) crystal planes and the other to adsorbed formate on a silver site modified by the presence of subsurface oxygen. Moreover, it was discovered that subsurface oxygen species were primarily located in the vicinity of grain boundary defects. Desorption profiles suggested that coadsorbed oxygen moieties could destabilize chemisorbed formate. Because of the invariance in infrared band positions associated with formate species, regardless of whether or not neighbouring atomic oxygen species were present, a kinetic stabiiization mechanism is proposed. The pivotal role of subsurface oxygen species found in the region of grain boundaries, in the mechanism for the selective oxidation of methanol to formaldehyde, is emphasised.</p

Influence of oxidation and reduction conditions upon the morphology of silica-supported polycrystalline silver catalysts

The effect of oxidation and reduction conditions upon the morphology of polycrystalline silver catalysts has been investigated by means of in situ Fourier-transform infrared (FTIR) spectroscopy. Characterization of the sample was achieved by inspection of the νas(COO) band profile of adsorbed formate, recorded after dosing with formic acid at ambient temperature. Evidence was obtained for the existence of a silver surface reconstructed by the presence of subsurface oxygen in addition to the conventional family of Ag(111) and Ag(110) crystal faces. Oxidation at 773 K facilitated the reconstruction of silver planes due to the formation of subsurface oxygen species. Prolonged oxygen treatment at 773 K also caused particle fragmentation as a consequence of excessive oxygen penetration of the silver catalyst at defect sites. It was also deduced that the presence of oxygen in the gas phase stabilized the growth of silver planes which could form stronger bonds with oxygen. In contrast, high-temperature thermal treatment in vacuum induced significant sintering of the silver catalyst. Reduction at 773 K resulted in substantial quantities of dissolved hydrogen (and probably hydroxy species) in the bulk silver structure. Furthermore, enhanced defect formation in the catalyst was also noted, as evidenced by the increased concentration of formate species associated with oxygen-reconstructed silver faces.</p

In situ Raman studies of the selective oxidation of methanol to formaldehyde and ethene to ethylene oxide on a polycrystalline silver catalyst

The combined techniques of in situ Raman microscopy and scanning electron microscopy (SEM) have been used to study the selective oxidation of methanol to formaldehyde and the ethene epoxidation reaction over polycrystalline silver catalysts. The nature of the oxygen species formed on silver was found to depend critically upon the exact morphology of the catalyst studied. Bands at 640, 780 and 960 cm were identified only on silver catalysts containing a significant proportion of defects. These peaks were assigned to subsurface oxygen species situated in the vicinity of surface dislocations, Ag=O sites formed on silver atoms modified by the presence of subsurface oxygen and O species stabilized on subsurface oxygen-modified silver sites, respectively. The selective oxidation of methanol to formaldehyde was determined to occur at defect sites, where reaction of methanol with subsurface oxygen initially produced subsurface OH species (451 cm) and adsorbed methoxy species. Two distinct forms of adsorbed ethene were identified on oxidised silver sites. One of these was created on silver sites modified by the interaction of subsurface oxygen species, and the other on silver crystal planes containing a surface coverage of atomic oxygen species. The selective oxidation of ethene to ethylene oxide was achieved by the reaction between ethene adsorbed on modified silver sites and electrophilic Ag=O species, whereas the combustion reaction was perceived to take place by the reaction of adsorbed ethene with nucleophilic surface atomic oxygen species. Defects were determined to play a critical role in the epoxidation reaction, as these sites allowed the rapid diffusion of oxygen into subsurface positions, and consequently facilitated the formation of the catalytically active Ag=O sites