Player agency in interactive narrative: audience, actor & author

The question motivating this review paper is, how can computer-based interactive narrative be used as a constructivist learn- ing activity? The paper proposes that player agency can be used to link interactive narrative to learner agency in constructivist theory, and to classify approaches to interactive narrative. The traditional question driving research in interactive narrative is, ‘how can an in- teractive narrative deal with a high degree of player agency, while maintaining a coherent and well-formed narrative?’ This question derives from an Aristotelian approach to interactive narrative that, as the question shows, is inherently antagonistic to player agency. Within this approach, player agency must be restricted and manip- ulated to maintain the narrative. Two alternative approaches based on Brecht’s Epic Theatre and Boal’s Theatre of the Oppressed are reviewed. If a Boalian approach to interactive narrative is taken the conflict between narrative and player agency dissolves. The question that emerges from this approach is quite different from the traditional question above, and presents a more useful approach to applying in- teractive narrative as a constructivist learning activity

Superconducting niobium thin film slow-wave structures

A superconducting comb structure as a slow-wave element in a traveling-wave maser will significantly improve maser noise temperature and gain by reducing the insertion loss. The results of the insertion loss measurements of superconducting niobium slow-wave structures subjected to maser operating conditions at X-Band frequencies are presented

XUV Frequency Combs via Femtosecond Enhancement Cavities

We review the current state of tabletop extreme ultraviolet (XUV) sources based on high harmonic generation (HHG) in femtosecond enhancement cavities (fsEC). Recent developments have enabled generation of high photon flux (1014 photons/sec) in the XUV, at high repetition rates (>50 MHz) and spanning the spectral region from 40 nm - 120 nm. This level of performance has enabled precision spectroscopy with XUV frequency combs and promises further applications in XUV spectroscopic and photoemission studies. We discuss the theory of operation and experimental details of the fsEC and XUV generation based on HHG, including current technical challenges to increasing the photon flux and maximum photon energy produced by this type of system. Current and future applications for these sources are also discussed.Comment: invited review article, 38 page

The elimination of surface cross-hatch from relaxed, limited-area Si1 – xGex buffer layers

The influence of lateral dimensions on the relaxation and surface topography of linearly graded Si1 – xGex buffer layers has been investigated. A dramatic change in the relaxation mechanism has been observed for depositions on Si mesa pillars of lateral dimensions 10 µm and below. Misfit dislocations are able to extend unhindered and terminate at the edges of the growth zone, yielding a surface free of cross-hatch. For lateral dimensions in excess of 10 µm orthogonal misfit interactions occur and relaxation is dominated by the modified Frank–Read (MFR) mechanism. The stress fields associated with the MFR dislocation pile-ups result in a pronounced cross-hatch topography

The generating function for a particular class of characters of SU(n)

We compute the generating function for the characters of the irreducible representations of SU(n) whose associated Young diagrams have only two rows with the same number of boxes. The result is a rational determinantal expression in which both the numerator and the denominator have a simple structure when expressed in terms of Schur polynomials.Comment: 7 pages, no figure

First measurements of the index of refraction of gases for lithium atomic waves

We report here the first measurements of the index of refraction of gases for lithium waves. Using an atom interferometer, we have measured the real and imaginary part of the index of refraction $n$ for argon, krypton and xenon, as a function of the gas density for several velocities of the lithium beam. The linear dependence of $(n-1)$ with the gas density is well verified. The total collision cross-section deduced from the imaginary part is in very good agreement with traditional measurements of this quantity. Finally, as predicted by theory, the real and imaginary parts of $(n-1)$ and their ratio $\rho$ exhibit glory oscillations

Echo-subject in Southern Vanuatu versus switch-reference

In this talk we discuss the echo subject (ES) system in Whitesands, and contrast the ES system in Whitesands — and Vanuatu ES systems in general — with the better known New Guinean type of switch reference (SR) systems. Like other Southern Vanuatu languages, Whitesands has an ES marker. The ES marker m- is used instead of a normal subject prefix when the subject of a clause is coreferential with some reference(s) of the preceding clause. The antecedent is usually the subject, but it can also be the object, an oblique, or some combinations of these. Together with a brief survey of ES systems in other Vanuatu languages, we will conclude that the ES systems in Vanuatu are used solely for the syntacto-semantic function of reference tracking. This contrasts with the New Guinean type of SR systems, which is used for both reference tracking and the discourse function of indicating participant continuity versus discontinuity. For instance, the so-called ‘same subject’ or ‘coreferential’ marker, other than indicating that some reference is coreferential with another reference, also indicates that the ‘SR pivot’ is a salient participant, and that it will remain foregrounded, or reappear in the foreground sometime later in the discourse

Two-dimensional molecular para-hydrogen and ortho-deuterium at zero temperature

We study molecular para-hydrogen (p-${\rm H_{2}}$) and ortho-deuterium (o-${\rm D_{2}}$) in two dimensions and in the limit of zero temperature by means of the diffusion Monte Carlo method. We report energetic and structural properties of both systems like the total and kinetic energy per particle, radial pair distribution function, and Lindemann's ratio in the low pressure regime. By comparing the total energy per particle as a function of the density in liquid and solid p-${\rm H_{2}}$, we show that molecular para-hydrogen, and also ortho-deuterium, remain solid at zero temperature. Interestingly, we assess the quality of three different symmetrized trial wave functions, based on the Nosanow-Jastrow model, in the p-${\rm H_{2}}$ solid film at the variational level. In particular, we analyze a new type of symmetrized trial wave function which has been used very recently to describe solid $^{4}$He and found that also characterizes hydrogen satisfactorily. With this wave function, we show that the one-body density matrix $\varrho_{1} (r)$ of solid p-${\rm H_{2}}$ possesses off-diagonal long range order, with a condensate fraction that increases sizably in the negative pressure regime.Comment: 11 pages, 9 figure

Dilute Bose gases interacting via power-law potentials

Neutral atoms interact through a van der Waals potential which asymptotically falls off as r^{-6}. In ultracold gases, this interaction can be described to a good approximation by the atom-atom scattering length. However, corrections arise that depend on the characteristic length of the van der Waals potential. We parameterize these corrections by analyzing the energies of two- and few-atom systems under external harmonic confinement, obtained by numerically and analytically solving the Schrodinger equation. We generalize our results to particles interacting through a longer-ranged potential which asymptotically falls off as r^{-4}.Comment: 7 pages, 4 figure

Revealing ensemble state transition patterns in multi-electrode neuronal recordings using hidden Markov models

In order to harness the computational capacity of dissociated cultured neuronal networks, it is necessary to understand neuronal dynamics and connectivity on a mesoscopic scale. To this end, this paper uncovers dynamic spatiotemporal patterns emerging from electrically stimulated neuronal cultures using hidden Markov models (HMMs) to characterize multi-channel spike trains as a progression of patterns of underlying states of neuronal activity. However, experimentation aimed at optimal choice of parameters for such models is essential and results are reported in detail. Results derived from ensemble neuronal data revealed highly repeatable patterns of state transitions in the order of milliseconds in response to probing stimuli