Exploring Fitness and Edit Distance of Mutated Python Programs

Genetic Improvement (GI) is the process of using computational search techniques to improve existing software e.g. in terms of execution time, power consumption or correctness. As in most heuristic search algorithms, the search is guided by fitness with GI searching the space of program variants of the original software. The relationship between the program space and fitness is seldom simple and often quite difficult to analyse. This paper makes a preliminary analysis of GI’s fitness distance measure on program repair with three small Python programs. Each program undergoes incremental mutations while the change in fitness as measured by proportion of tests passed is monitored. We conclude that the fitnesses of these programs often does not change with single mutations and we also confirm the inherent discreteness of bug fixing fitness functions. Although our findings cannot be assumed to be general for other software they provide us with interesting directions for further investigation

Differential Modulation of Beta-Adrenergic Receptor Signaling by Trace Amine-Associated Receptor 1 Agonists

Trace amine-associated receptors (TAAR) are rhodopsin-like G-protein-coupled receptors (GPCR). TAAR are involved in modulation of neuronal, cardiac and vascular functions and they are potentially linked with neurological disorders like schizophrenia and Parkinson's disease. Subtype TAAR1, the best characterized TAAR so far, is promiscuous for a wide set of ligands and is activated by trace amines tyramine (TYR), phenylethylamine (PEA), octopamine (OA), but also by thyronamines, dopamine, and psycho-active drugs. Unfortunately, effects of trace amines on signaling of the two homologous β-adrenergic receptors 1 (ADRB1) and 2 (ADRB2) have not been clarified yet in detail. We, therefore, tested TAAR1 agonists TYR, PEA and OA regarding their effects on ADRB1/2 signaling by co-stimulation studies. Surprisingly, trace amines TYR and PEA are partial allosteric antagonists at ADRB1/2, whereas OA is a partial orthosteric ADRB2-antagonist and ADRB1-agonist. To specify molecular reasons for TAAR1 ligand promiscuity and for observed differences in signaling effects on particular aminergic receptors we compared TAAR, tyramine (TAR) octopamine (OAR), ADRB1/2 and dopamine receptors at the structural level. We found especially for TAAR1 that the remarkable ligand promiscuity is likely based on high amino acid similarity in the ligand-binding region compared with further aminergic receptors. On the other hand few TAAR specific properties in the ligand-binding site might determine differences in ligand-induced effects compared to ADRB1/2. Taken together, this study points to molecular details of TAAR1-ligand promiscuity and identified specific trace amines as allosteric or orthosteric ligands of particular β-adrenergic receptor subtypes

Photopyroelectric Spectroscopy (P2ES) of a-Si:H Thin Semiconducting Films on Quartz

Photopyroelectric Spectroscopy has proven to be a sensitive qualitative [1] and quantitative [2] technique for thin film spectroscopic applications. An important feature of this back-surface detection technique, not shared with the more conventional front-surface photothermal detection methods (Photothermal Deflection Spectroscopy, PDS; and Photoacoustic Spectroscopy, PAS) is its ability to measure directly and separately two independent spectrally-varying parameters: the optical absorption coefficient [3] and the nonradiative quantum efficiency. PDS of thin semiconducting films of amorphous hydrogenated Si [4] readily yields information about the product of the optical absorption coefficient, α(λ), and the nonradiative quantum efficiency, η(λ). The standard assumption is, however, that η(λ) is not a sensitive function of the exciting photon energy. This assumption is generally wrong, and nonradiative quantum efficiencies have been found photoacoustically to vary by one order of magnitude [5] across the optical gap in Ge doped As 2 Se 3 chalcogenide glasses. PAS yields amorphous thin film spectra similar to PDS [6]. The working assumption has been that PA spectra are essentially accurate above the optical gap, as η(λ) is expected to be independent of photon energy. Kitamura et al. [5] were able to derive extended η(λ) spectra of (As 2 Se 3 )100-x Ge xglasses upon combining PA spectra with optical absorption coefficient information obtained in an independent spectrophotometric experiment using ordinary polished bulk samples. These authors, however, were not able to guarantee that the glasses and the bulk samples had the same (or even nearly similar) α(λ) spectra.</p