Penalized estimation in large-scale generalized linear array models

Large-scale generalized linear array models (GLAMs) can be challenging to fit. Computation and storage of its tensor product design matrix can be impossible due to time and memory constraints, and previously considered design matrix free algorithms do not scale well with the dimension of the parameter vector. A new design matrix free algorithm is proposed for computing the penalized maximum likelihood estimate for GLAMs, which, in particular, handles nondifferentiable penalty functions. The proposed algorithm is implemented and available via the R package \verb+glamlasso+. It combines several ideas -- previously considered separately -- to obtain sparse estimates while at the same time efficiently exploiting the GLAM structure. In this paper the convergence of the algorithm is treated and the performance of its implementation is investigated and compared to that of \verb+glmnet+ on simulated as well as real data. It is shown that the computation time fo

Wide band, tunable gamma-ray lenses

A new concept for an astronomical telescope in the MeV energy band is presented. The concept builds on Bragg diffraction in crystals, which has been discussed in the past, but so far a design with good sensitivity over a wide energy range has seemed out of reach. In this paper we point out that if we find ways to adjust, in orbit, the individual tilt of all the crystals in the lens this would allow one single lens to cover with excellent efficiency the full range of energies from 200 keV to 2.5 MeV in a few observation steps. Secondly, we note that the use of lenses with double crystal layers will increase the photon collection significantly. In an accompanying paper we describe our overall lens design in more detail and present our first prototype tilt adjustment pedestal for use with the individual lens facets. Keyords: Gamma-ray astronomy, Telescope technology, Laue lensesComment: Submitted to Experimental Astronom

Technologies for tunable gamma-ray lenses

The tunable gamma-ray lens has turned out to be a promising alternative to the classical fixed-energy Laue-lenses discussed in the past. We describe here our development work on a miniature pedestal with one-axis tilt adjustment. We also outline our design for an optical system, capable of monitoring the alignment of the many crystals needed. An added benefit of the tunable crystal pedestal is that it relieves both the demands for high precision in the crystal mounting and the stringent requirements for long-term stability of the support platform on which the crystals are mounted. Moreover, mounting the individual crystals on separate pedestals facilitates the use of double layers of crystals. Keywords: Gamma-ray astronomy, Telescope technology, Laue lensesComment: Submitted to Experimental Astronom

The power of co-creative story-telling in narratives of place: An account of VisitDenmark's social media practices to build alliances with storytellers

DMOs have for some years now developed strategies to create storytelling alliances with consumers in order to strengthen their destinations’ narrative position on social media. The emergence of social media has facilitated a democratisation of media production and a power shift towards consumers who can now produce and publish content (Berthon, Pitt, Plangger and Shapiro, 2012). This means that the construction of brands within social media can be interpreted as a collective, dynamic co-creational process involving multiple brand authors who all contribute their personal stories (Gensler, Völckner, Liu-Thompkins, & Wiertz, 2013). DMOs have to some degree adapted to the new social media spaces of storytelling (Roque and Raposso, 2016; Usakli, Koç and Sönmez, 2017). They try to actively engage with their tourists online to utilise their stories, repackage them and spread the positive narratives experienced at the destination. They need the users’ help to do marketing and branding as the users’ stories generate conversations about the destination and subsequently increase awareness. This paper offers an insight into VisitDenmark’s social media strategy to build alliances with users through a co-creative approach. VisitDenmark’s (2014) social media branding strategy is based on the so-called ‘Unceasing Eco-system’, where users’ stories, knowledge and recommendations are utilised before, during and after they have been at the destination

Overalls - Complex Document(s): a Never-ending Artistic Research Process

I want to show that a pair of overalls can be a document in many senses, and thus demonstrate that the complementary relationship between materiality, sociality and conceptuality is a very complex relationship. I will use an artistic approach to show the complex relationship and make an exposition of verbal text and images, consisting of 4 parts: 1. Origin of overalls A short history of overalls - denim pants first with suspenders and later with bibs. They go back to the 18th century, were mass-produced by Levi Strauss and Lee and became popular work garment and later for leisure and fashion for both men and women. 2. Broken in overalls A document of use and often hard work, shown in faded denim. They can be used for generations, with overalls handed over from father to sons or daughters 3. Mending overalls A document of repairing overalls by mending and patching, documenting traditions for mending clothes 4. Overalls as wearable art A document of art shown by the visible mending and patches making overalls into pieces of art work 5. Document theory Overalls - a showcase of the complexity of the complementary relationship between materiality, sociality and conceptualit

Experimental Document Analysis—an analytical framework for document design

In this paper I will present an analytical framework for future documents, an experimental document analysis providing support for document design. The American economist, Herbert A. Simon outlined how to design an artificial object in his work The Sciences of the Artificial (1969, 1996) and described how this can be done in a systematic way, by a science of design. Simon describes the design process as a matter of finding possible alternatives among the potential optimal alternatives and finding a satisficing solution, by which he means a solution in-between satisfactory solutions and optimal solutions which can work in real life, expressing a rationality bounded by the conditions given by the environment. I will illustrate the experimental document analysis by an historical example of a pasticcio opera in the 18th century, Dido Abbandonata by P. Metastastio and multiple composers. I will discuss how this kind of document analysis may open for a comparative approach in documentation research in general

How It All Started: 1996, the First Year of Dokvit

This article describes in detail the first year of the Documentation Studies (Dokvit) program in Tromsø (1996) in attempt to offer an understanding of how Dokvit was part of the neo-documentation movement that began in the mid-90s with the rediscovery of Suzanne Briet and discussions on What is a \u27document\u27? This article discusses how the Dokvit program was structured, including its curriculum, syllabus and teaching principles. In particular, it details the undergraduate student projects done this year and demonstrates how they were embedded within the historical and media situation of 1996. In conclusion, this article discusses how the experience of that first year in 1996 can be used today, 20 years later, in building the future of media and documentation studies—not only in Tromsø, but worldwide

Opera as a Multimedia Document

Opera can be considered a multimedia document created through a complex process involving multiple people and media. Opera arose in the 17th century as a way to synthesize multiple art forms. This work offers a panoramic overview of the historic development of opera, including examples of key works along this trajectory. It closes with some questions about the future of opera

Observations of short-duration X-ray transients by WATCH on Granat

During 1990-92, the WATCH all-sky X-ray monitor on Granat discovered six short-duration X-ray transients. In this paper we discuss their possible relationship to peculiar stars. Only one of the fast (few hours) X-ray transients (GRS 1100-771) might be tentatively ascribed to a superflare arising from a young stellar object in the Chamaeleon I star-forming cloud. At the distance of 150 pc, Lx = 1.35 x 10E34 erg/s (8-15 keV), or 2.6 x 10E34 erg/s (0.1-2.4 keV) assuming a thermal spectrum with kT = 10 keV, a temperature higher than those previously seen in T Tauri stars (Tsuboi et al. 1998). The peak X-ray luminosity is at least 2 times higher than that derived for the protostar IRS 43 (Grosso et al. 1997) which would make -to our knowledge- the strongest flare ever seen in a young stellar object. However, the possibility of GRS 1100-771 being an isolated neutron star unrelated to the cloud cannot be excluded, given the relatively large error box provided by WATCH. Regarding the longer duration (about 1 day) X-ray transients, none of them seem to be related to known objects. We suggest that the latter are likely to have originated from compact objects in low-mass or high-mass X-ray binaries, similarly to XTE J0421+560.Comment: Accepted for publication in Astronomy and Astrophysics (5 pages, 2 figures