Canonical Analysis of the Jackiw-Teitelboim Model in the Temporal Gauge. I. The Classical Theory

As a preparation for its quantization in the loop formalism, the 2-dimensional gravitation model of Jackiw and Teitelboim is analysed in the classical canonical formalism. The dynamics is of pure constraints as it is well-known. A partial gauge fixing of the temporal type being performed, the resulting second class constraints are sorted out and the corresponding Dirac bracket algebra is worked out. Dirac observables of this classical theory are then calculated.Comment: 15 pages, Latex. Misprint correction

Species-specific growth response of coccolithophores to Palaeocene–Eocene environmental change

Coccolithophores—single-celled calcifying phytoplankton—represent an essential footing to marine ecosystems, yet their sensitivity to environmental change, and in particular increases in atmospheric CO2, is poorly understood1. During the Palaeocene–Eocene Thermal Maximum (PETM), about 56 million years ago, atmospheric CO2 concentrations rose rapidly and the oceans acidified2, 3, making this an ideal time interval to examine coccolithophore responses to environmental change. Here we compare the results of experiments on modern coccolithophore species with exceptional fossil coccosphere records of the PETM, providing a cellular-level perspective. In modern taxa, we find that during the exponential growth phase of rapid cell division, small cells with few coccoliths are produced, whereas larger cells with more coccoliths are produced during slowed cell division. Applying these diagnostic features to the PETM fossil record, we find that the dominant species exhibited different growth responses to the environmental forcing. Toweius pertusus shows geometry indicative of rapid cell division. In contrast, we suggest that cells of Coccolithus pelagicus grew more slowly during the period of environmental change. In the modern ocean, Emiliania huxleyi, which is closely related to the extinct T. pertusus, is prolific and widespread, whereas C. pelagicus is more limited in range and abundance. We argue that these different responses to environmental change were critical to the post-PETM evolutionary success of the descendants of these taxa

Workforce Skills Credentialing: Security Framework Report

The Credentialing Security Framework is designed to be used as a stand-alone guide or together with the efforts of other organizations (e.g. Connecting Credentials, the European Commission) to provide greater transparency regarding assessment-based workforce skills credentials