Video Game Navigation: A Classification System for Navigational Acts

Navigation in video games has been a vastly neglected topic in game studies. In this paper a classification system for navigational acts has been developed through theoretical work as well as the analysis of multiple games. The result is an exclusive five-step classification system. Moreover, the development showed that navigational acts are highly dependent on the environment in which they occur. The system is a first step towards a deeper understanding of how the player navigates the gameworld, instead of what she navigates

Influence of the heterointerface sharpness on exciton recombination dynamics in an ensemble of (In,Al)As/AlAs quantum dots with indirect band-gap

The dynamics of exciton recombination in an ensemble of indirect band-gap (In,Al)As/AlAs quantum dots with type-I band alignment is studied. The lifetime of confined excitons which are indirect in momentum-space is mainly influenced by the sharpness of the heterointerface between the (In,Al)As quantum dot and the AlAs barrier matrix. Time-resolved photoluminescence experiments and theoretical model calculations reveal a strong dependence of the exciton lifetime on the thickness of the interface diffusion layer. The lifetime of excitons with a particular optical transition energy varies because this energy is obtained for quantum dots differing in size, shape and composition. The different exciton lifetimes, which result in photoluminescence with non-exponential decay obeying a power-law function, can be described by a phenomenological distribution function, which allows one to explain the photoluminescence decay with one fitting parameter only.Comment: 10 pages, 7 figure

Spin dynamics and magnetic-field-induced polarization of excitons in ultrathin GaAs/AlAs quantum wells with indirect band gap and type-II band alignment

The exciton spin dynamics are investigated both experimentally and theoretically in two-monolayer-thick GaAs/AlAs quantum wells with an indirect band gap and a type-II band alignment. The magnetic-field-induced circular polarization of photoluminescence, $P_c$, is studied as function of the magnetic field strength and direction as well as sample temperature. The observed nonmonotonic behaviour of these functions is provided by the interplay of bright and dark exciton states contributing to the emission. To interpret the experiment, we have developed a kinetic master equation model which accounts for the dynamics of the spin states in this exciton quartet, radiative and nonradiative recombination processes, and redistribution of excitons between these states as result of spin relaxation. The model offers quantitative agreement with experiment and allows us to evaluate, for the studied structure, the heavy-hole $g$ factor, $g_{hh}=+3.5$, and the spin relaxation times of electron, $\tau_{se} = 33~\mu$s, and hole, $\tau_{sh} = 3~\mu$s, bound in the exciton.Comment: 17 pages, 16 figure

Restoring betatron phase coherence in a beam-loaded laser-wakefield accelerator

Matched beam loading in laser wakefield acceleration (LWFA), characterizing the state of flattening of the acceleration electric field along the bunch, leads to the minimization of energy spread at high bunch charges. Here, we demonstrate by independently controlling injected charge and acceleration gradients, using the self-truncated ionization injection scheme, that minimal energy spread coincides with a reduction of the normalized beam divergence. With the simultaneous confirmation of a constant beam radius at the plasma exit, deduced from betatron radiation spectroscopy, we attribute this effect to the reduction of chromatic betatron decoherence. Thus, beam loaded LWFA enables highest longitudinal and transverse phase space densities

Assessment of band recoveries for three Australian eagle species

Band recoveries to 2012 were analysed for the White-bellied Sea-Eagle 'Haliaeetus leucogaster' (n = 11, recovery rate = 6%), Wedge-tailed Eagle 'Aquila audax' (n = 55, recovery rate = 7%) and Little Eagle 'Hieraaetus morphnoides' (n = 30, recovery rate = 9%) in Australia (for Wedge-tailed Eagle eastern Australia only). Juvenile/immature Sea-Eagles (n = 8) were recovered within 3.5 years (0-41 months, mean 13 months), 0-1824 kilometres (mean 268 km) from the banding site. Adults (n = 3) were recovered at the banding site; one notable lifespan was 19+ years. Of 60 Sea-Eagles wing-tagged in the coastal Northern Territory, 1978-1994, four (recovery rate = 7%) were juveniles recovered/resighted within 1-4 years, 30-90 kilometres from the banding site, whereas territorial adults were resighted on their territories over the ensuing year. Juvenile/immature Wedge-tailed Eagles (n = 55) were recovered 0-821 kilometres from the banding site (mean 130 km, 95% within 300 km), 1-72 months later (mean 11 months); one banded on Kangaroo Island was recovered on the adjacent mainland (13+ km across sea). Little Eagles (mostly aged as 'first year or older' and unsexed) were recovered 0-2884 kilometres from the banding site (mean 219 km, 80% within 200 km), 1-311 months later (mean 60 months); notable lifespans were of 19-26 years, but average lifespan may be approximately five years in the sheep-wheat belt. Human-related mortalities, either deliberate (persecution) or accidental (e.g. collisions, interactions with infrastructure), formed a large proportion of the reported public recoveries of each species

Tracing the first steps of American sturgeon pioneers in Europe

Background: A Baltic population of Atlantic sturgeon was founded ~1,200 years ago by migrants from North America, but after centuries of persistence, the population was extirpated in the 1960s, mainly as a result of over-harvest and habitat alterations. As there are four genetically distinct groups of Atlantic sturgeon inhabiting North American rivers today, we investigated the genetic provenance of the historic Baltic population by ancient DNA analyses using mitochondrial and nuclear markers. Results: The phylogeographic signal obtained from multilocus microsatellite DNA genotypes and mitochondrial DNA control region haplotypes, when compared to existing baseline datasets from extant populations, allowed for the identification of the region-of-origin of the North American Atlantic sturgeon founders. Moreover, statistical and simulation analyses of the multilocus genotypes allowed for the calculation of the effective number of individuals that originally founded the European population of Atlantic sturgeon. Our findings suggest that the Baltic population of A. oxyrinchus descended from a relatively small number of founders originating from the northern extent of the species' range in North America. Conclusion: These results demonstrate that the most northerly distributed North American A. oxyrinchus colonized the Baltic Sea ~1,200 years ago, suggesting that Canadian specimens should be the primary source of broodstock used for restoration in Baltic rivers. This study illustrates the great potential of patterns obtained from ancient DNA to identify population-of-origin to investigate historic genotype structure of extinct populations

Instruments of value: using the analytic tools of public value theory in teaching and practice

The tools of public value management - such as the strategic triangle and the public value account,– are increasingly used by scholars and practitioners alike. At the same time, some confusion remains regarding their functionality in action. Based on our experiences with these tools in classrooms and boardrooms, we analyze how these instruments help to explore and structure different dimensions of public management challenges. We propose a set of ‘principles of application’, detailing under what conditions public value tools are most likely to be helpful, and suggest a course of action for strengthening, connecting and extending the current tool box