Roadmap towards the redefinition of the second

This paper outlines the roadmap towards the redefinition of the second, which was recently updated by the CCTF Task Force created by the CCTF in 2020. The main achievements of optical frequency standards (OFS) call for reflection on the redefinition of the second, but open new challenges related to the performance of the OFS, their contribution to time scales and UTC, the possibility of their comparison, and the knowledge of the Earth's gravitational potential to ensure a robust and accurate capacity to realize a new definition at the level of 10-18 uncertainty. The mandatory criteria to be achieved before redefinition have been defined and their current fulfilment level is estimated showing the fields that still needed improvement. The possibility to base the redefinition on a single or on a set of transitions has also been evaluated. The roadmap indicates the steps to be followed in the next years to be ready for a sound and successful redefinition

Synthesis of Unsymmetrical Diarylureas via Pd-Catalyzed C–N Cross-Coupling Reactions

A facile synthesis of unsymmetrical N,N′-diarylureas is described. The utilization of the Pd-catalyzed arylation of ureas enables the synthesis of an array of diarylureas in good to excellent yields from benzylurea via a one-pot arylation–deprotection protocol, followed by a second arylation.National Institutes of Health (U.S.) (Grant GM58160)Bristol-Myers Squibb Company (Graduate Fellowship)National Science Foundation (U.S.) (Grant CHE9808061)National Institutes of Health (U.S.) (Grant DBI 9729592

Meal-Anticipatory Glucagon-Like Peptide-1 Secretion in Rats

Animals anticipating a meal initiate a series of responses enabling them to better cope with the meal’s metabolic impact. These responses, such as cephalic insulin, occur prior to the onset of ingestion and are especially evident in animals maintained on a meal-feeding schedule with limited but predictable access to food each day. We tested the hypothesis that meal-fed rats secrete the incretin hormone glucagon-like peptide-1 (GLP-1) cephalically when anticipating a large meal. Male Long-Evans rats were fed ad libitum (controls) or adapted to a schedule on which food was available for the same 4-h period each day (meal fed animals). Plasma GLP-1 increased in meal-fed rats over an interval from 75 to 60 min prior to feeding time, from a baseline of 10 to around 40 pm, and then returned to baseline prior to food presentation. Controls had steady plasma GLP-1 levels (10–15 pm) over the same span. Meal-fed rats also secreted cephalic insulin starting around 15 min prior to food presentation. Administration of the selective GLP-1 receptor antagonist exendin-4[desHis-1,Glu-9] prior to the premeal spike of GLP-1 caused meal-fed rats to eat significantly less food than normal, whereas administration of the antagonist after the GLP-1 spike but prior to food presentation resulted in a significant increase in food consumption. These findings document for the first time a cephalic increase of plasma GLP-1 and suggest that it functions to facilitate consumption of a large meal