A new population of terrestrial gamma-ray flashes in the RHESSI data

Terrestrial gamma-ray flashes (TGFs) are the most energetic photon phenomenon occurring naturally on Earth. An outstanding question is as follows: Are these flashes just a rare exotic phenomenon or are they an intrinsic part of lightning discharges and therefore occurring more frequently than previously thought? All measurements of TGFs so far have been limited by the dynamic range and sensitivity of spaceborne instruments. In this paper we show that there is a new population of weak TGFs that has not been identified by search algorithms. We use the World Wide Lightning Location Network (WWLLN) to identify lightning that occurred in 2006 and 2012 within the 800 km field of view of Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). By superposing 740,210 100 ms RHESSI data intervals, centered at the time of the WWLLN detected lightning, we identify at least 141 and probably as many as 191 weak TGFs that were not part of the second RHESSI data catalogue. This supports the suggestion that the global TGF production rate is larger than previously reported

Affordances in activity theory and cognitive systems engineering

For the last decade, the Gibsonian concept of affordances has at- tracted much attention within Human-Machine Interaction (HMI) and related research communities. The application of Gibson's ideas in HMI has lead to the notion of direct manipulation of interface objects. Previously, the focus has been on design for low level interaction modalities. To incorporate the concept of affordances in the design of human computer interaction it is necessary to systematically unravel affordances that support human action possibilities. Furthermore, it is a necessity that Gibson's theory of affordances is supplemented by careful analyses of other human modalities and activities than visual perception. Within HMI two well established perspectives on HMI, Activity Theory (AT) and Cognitive Systems Engineering (CSE), have discussed such analyses and design of action possibilities focusing on providing computer support for work situations. Within these perspectives, the primary unit of analysis in HMI is human work activity and the socio-cultural context in which this activity is carried out. Thus, they emphasise the actors' purposeful activity as the most important design rationale. According to previous views in HMI, notably those that have been put forward by Norman and Gaver, affordances are in the foreground, whereas the system or work area is in the background. AT and CSE share the view that the actors' perception of foreground and background shifts dynamically according to the actors' situational context in purposeful activity. AT and CSE follow the original notion by Gibson on the actor's dynamic shifting between foreground and background of the environment. Furthermore, their work- and actor-centred approach to analysis and design of information sys..

Detection of Legionella by quantitative-polymerase chain reaction (qPCR) for monitoring and risk assessment

<p>Abstract</p> <p>Background</p> <p>Culture and quantitative polymerase chain reaction (qPCR) assays for the detection of <it>Legionella </it>were compared on samples from a residential area before and after two interventions. A total of 84 samples were collected from shower hoses and taps as first flush samples and at constant temperature. Samples were grouped according to the origin of the sample, a) circulation water b) water from empty apartments c) water from shower hoses. The aims were to investigate the usefulness of qPCR compared to culture for monitoring remedial actions for elimination of <it>Legionella </it>bacteria and as a tool for risk assessment.</p> <p>Results</p> <p>In water collected from the apartments <it>Legionella </it>spp were detected by qPCR in the concentration range from LOQ to 9.6*10⁵GU/L while <it>L. pneumophila </it>were detected in a range from LOQ to 6.8*10⁵GU/L. By culturing, the legionellae were detected in the range from below detection limit (> 10 CFU/L) to 1.6*10⁶CFU/L. In circulating water and in first flush water from shower hoses, culture and qPCR showed the same tendencies. The overall correlation between the bacteria number detected by culture and the two developed qPCR assays (<it>L</it>. spp and <it>L. pneumophila</it>) was relatively poor (r²= 0.31 for culture and <it>Legionella </it>spp. assay, r²= 0.20 for culture and <it>L. pneumophila </it>assay).</p> <p>Conclusion</p> <p>Detection by qPCR was suitable for monitoring changes in the concentration of <it>Legionella </it>but the precise determination of bacteria is difficult. Risk assessment by qPCR only on samples without any background information regarding treatment, timing, etc is dubious. However, the rapid detection by qPCR of high concentrations of <it>Legionella </it>- especially <it>Legionella pneumophila </it>- is valuable as an indicator of risk, although it may be false positive compared to culture results. On the other hand, the detection of a low number of bacteria by qPCR is a strong indication for the absence of risk.</p

Laser-induced Coulomb explosion of heteronuclear alkali dimers on helium nanodroplets

A sample mixture of alkali homonuclear dimers, Ak$_2$ and Ak$^{\prime}_2$ and heteronuclear dimers, AkAk$^{\prime}$, residing on the surface of helium nanodroplets are Coulomb exploded into pairs of atomic alkali cations, (Ak$^{+}$,Ak$^{+}$), (Ak$^{\prime +}$,Ak$^{\prime +}$), (Ak$^{+}$, Ak$^{\prime +}$), following double ionization induced by an intense 50 fs laser pulse. The measured kinetic energy distribution $P(E_{\text{kin}})$ of both the Ak$^{+}$ and the Ak$^{\prime +}$ fragment ions contains overlapping peaks due to contributions from Coulomb explosion of the homonuclear and the heteronuclear dimers. Using a coincident filtering method based on the momentum division between the two fragment ions in each Coulomb explosion event, we demonstrate that the individual $P(E_{\text{kin}})$ pertaining to the ions from either the heteronuclear or from the homonuclear dimers can be retrieved, for both the Ak$^{+}$ and for the Ak$^{\prime +}$ fragment ions. This filtering method works through the concurrent detection of two-dimensional velocity images of the Ak$^{+}$ and the Ak$^{\prime +}$ ions implemented through the combination of a velocity map imaging spectrometer and a TPX3CAM detector. The key finding is that $P(E_{\text{kin}})$ for heteronuclear alkali dimers can be distinguished despite the simultaneous presence of homonuclear dimers. From $P(E_{\text{kin}})$ we determine the distribution of internuclear distances $P(R)$ via the Coulomb explosion imaging principle. We report results for LiK and for NaK but our method should should also work for other heteronuclear dimers and for differentiating between different isotopologues of homonuclear dimers.Comment: 10 pages, 11 figure

A Web-based multimedia collaboratory. Empirical work studies in film archives

This report represents the latest study in the activity on Ecological Information Systems conducted in the Center for Human Machine Interaction situated at Ris National Laboratory and the University of Aarhus. The purpose of this activity is to give a description of the characteristics of work domains that will serve to outline the general context of concern to design of collaboratories. In addition, a set of preliminary implications for the design of a collaboratory are derived from the cognitive work analysis. To anticipate, further research on this approach to the design of collaboratories will show how the preceding analysis is likely to lead to a novel theoretical framework, called Ecological Collaborative Information Systems (ECIS), required for the design of collaboratories. The intention is to illustrate how the general principles of ECIS can be instantiated to develop a concrete design product: A crossdisciplinary and cross-cultural collaboratory to support customer service and professional research in archives. A web based Collaboratory Numerous valuable historic and cultural films and their sources are scattered in various national archives. Knowledge and usage of the multinational film material are severely impeded by access problems. To fully exploit the cultural film heritage internationally, a high degree of cross-disciplinary and international collaboration among professionals working with the film media is required. The Collaboratory for Annotation, Indexing and Retrieval of Digitized Historical Archive Material (Collate) is intended to foster and support collaboration on research, cultural mediation and preservation of films through a distributed multimedia repository. The collaboratory will provide webbased tools and interfac..

The Validation and Assessment of Machine Learning: A Game of Prediction from High-Dimensional Data

In applied statistics, tools from machine learning are popular for analyzing complex and high-dimensional data. However, few theoretical results are available that could guide to the appropriate machine learning tool in a new application. Initial development of an overall strategy thus often implies that multiple methods are tested and compared on the same set of data. This is particularly difficult in situations that are prone to over-fitting where the number of subjects is low compared to the number of potential predictors. The article presents a game which provides some grounds for conducting a fair model comparison. Each player selects a modeling strategy for predicting individual response from potential predictors. A strictly proper scoring rule, bootstrap cross-validation, and a set of rules are used to make the results obtained with different strategies comparable. To illustrate the ideas, the game is applied to data from the Nugenob Study where the aim is to predict the fat oxidation capacity based on conventional factors and high-dimensional metabolomics data. Three players have chosen to use support vector machines, LASSO, and random forests, respectively

A Placebo-Controlled Study on the Effects of the Glucagon-Like Peptide-1 Mimetic, Exenatide, on Insulin Secretion, Body Composition and Adipokines in Obese, Client-Owned Cats

Glucagon-like Peptide-1 mimetics increase insulin secretion and reduces body weight in humans. In lean, healthy cats, short-term treatment has produced similar results, whereas the effect in obese cats or with extended duration of treatment is unknown. Here, prolonged (12 weeks) treatment with the Glucagon-like Peptide-1 mimetic, exenatide, was evaluated in 12 obese, but otherwise healthy, client-owned cats. Cats were randomized to exenatide (1.0 μg/kg) or placebo treatment twice daily for 12 weeks. The primary endpoint was changes in insulin concentration; the secondary endpoints were glucose homeostasis, body weight, body composition as measured by dual-energy x-ray absorptiometry and overall safety. An intravenous glucose tolerance test (1 g/kg body weight) was conducted at week 0 and week 12. Exenatide did not change the insulin concentration, plasma glucose concentration or glucose tolerance (P>0.05 for all). Exenatide tended to reduce body weight on continued normal feeding. Median relative weight loss after 12 weeks was 5.1% (range 1.7 to 8.4%) in the exenatide group versus 3.2% (range -5.3 to 5.7%) in the placebo group (P = 0.10). Body composition and adipokine levels were unaffected by exenatide (P>0.05). Twelve weeks of exenatide was well-tolerated, with only two cases of mild, self-limiting gastrointestinal signs and a single case of mild hypoglycemia. The long-term insulinotropic effect of exenatide appeared less pronounced in obese cats compared to previous short-term studies in lean cats. Further investigations are required to fully elucidate the effect on insulin secretion, glucose tolerance and body weight in obese cats

Excited rotational states of molecules in a superfluid

We combine experimental and theoretical approaches to explore excited rotational states of molecules embedded in helium nanodroplets using CS$_2$ and I$_2$ as examples. Laser-induced nonadiabatic molecular alignment is employed to measure spectral lines for rotational states extending beyond those initially populated at the 0.37 K droplet temperature. We construct a simple quantum mechanical model, based on a linear rotor coupled to a single-mode bosonic bath, to determine the rotational energy structure in its entirety. The calculated and measured spectral lines are in good agreement. We show that the effect of the surrounding superfluid on molecular rotation can be rationalized by a single quantity -- the angular momentum, transferred from the molecule to the droplet.Comment: 5 pages, 4 figures; 5 pages, 3 figure