Stability of trapped fermionic gases with attractive interactions

We present a unified overview, from the mean-field to the unitarity regime, of the stability of a trapped Fermi gas with short range attractive interactions. Unlike in a system of bosons, a Fermi gas is always stable in these regimes, no matter how large the particle number. However, when the interparticle spacing becomes comparable to the range of the interatomic interactions, instability is not precluded.Comment: 5 pages, 4 figure

Metabolic profiling of environmental stress in Scleractinian corals

Ben Gordon studied the effects of environmental stress on the metabolome of reef-building corals. His research produced the first extraction and analysis protocol for coral metabolomics and identified machine learning methods to classify the functional state of corals under a variety of conditions. His work has provided novel biomarkers of coral health and directions for implementing metabolomics biomonitoring

Designing protein β-sheet surfaces by Z-score optimization

Studies of lattice models of proteins have suggested that the appropriate energy expression for protein design may include nonthermodynamic terms to accommodate negative design concerns. One method, developed in lattice model studies, maximizes a quantity known as the "Z-score," which compares the lowest energy sequence whose ground state structure is the target structure to an ensemble of random sequences. Here we show that, in certain circumstances, the technique can be applied to real proteins. The resulting energy expression is used to design the β-sheet surfaces of two real proteins. We find experimentally that the designed proteins are stable and well folded, and in one case is even more thermostable than the wild type

The hagiography of St Alban and St Amphibalus in the twelfth century

This study is based on the fact that hagiographical texts can be used as historical sources. It examines texts produced at St Albans Abbey in the second half of the twelfth century which record the lives and miracles of St Alban and St Amphibalus, some of which were written by the monk William of St Albans. These texts were a stage in the development of the legend of St Alban which had its origins in Roman Britain. Textual and historical evidence suggests that they were written to provide both literary back-up for the discovery of the relics of St Amphibalus in June 1177, at Redbourn, near St Albans, and to document the emergent cult of that saint. The text can also be used to show that a principal motive for the initiation of the cult of St Amphibalus was the success of the cult of St Thomas of Canterbury, although there is also other evidence to suggest that St Albans Abbey was in debt and needed a new source of income. The invention-account and the miracle-account of St Amphibalus have not been studied before, and provide much information about the mechanics of cult-initiation and the spread of a 'new' saint's reputation for healing power

Reverse Derivative Categories

The reverse derivative is a fundamental operation in machine learning and automatic differentiation. This paper gives a direct axiomatization of a category with a reverse derivative operation, in a similar style to that given by Cartesian differential categories for a forward derivative. Intriguingly, a category with a reverse derivative also has a forward derivative, but the converse is not true. In fact, we show explicitly what a forward derivative is missing: a reverse derivative is equivalent to a forward derivative with a dagger structure on its subcategory of linear maps. Furthermore, we show that these linear maps form an additively enriched category with dagger biproducts.Comment: Extended version of paper to appear at CSL 202

Diagnosability, Adequacy & Size: How Test Suites Impact Autograding

Automated grading is now prevalent in software engineering courses, typically assessing the correctness of students' programs using automated test suites. However, deficiencies in test suites could result in inconsistent grading. As such, we investigate how different test suites impact grades, and the extent to which their observable properties influence these grades. We build upon existing work, using students' solution programs, and test suites that we constructed using a sampling approach. We find that there is a high variation in grades from different test suites, with a standard deviation of ~10.1%. We further investigate how several properties of test suites influence these grades, including the number of tests, coverage, ability to detect other faults, and uniqueness. We use our findings to provide tutors with strategies for building test suites that evaluate students' software with consistency. These strategies include constructing test suites with high coverage, writing unique and diverse tests which evaluate solutions' correctness in different ways, and to run the tests against artificial faults to determine their quality