Dark matter from cosmic defects on galactic scales?

We discuss the possible dynamical role of extended cosmic defects on galactic scales, specifically focusing on the possibility that they may provide the dark matter suggested by the classical problem of galactic rotation curves. We emphasize that the more standard defects (such as Goto-Nambu strings) are unsuitable for this task, but show that more general models (such as transonic wiggly strings) could in principle have a better chance. In any case, we show that observational data severely restricts any such scenarios.Comment: Submitted to Phys. Rev. D (Brief Reports). v2: Reference added and some typos corrected, matches published versio

Neutron activation analysis traces copper artifacts to geographical point of origin

Impurities remaining in the metallic copper are identified and quantified by spectrographic and neutron activation analysis. Determination of the type of ore used for the copper artifact places the geographic point of origin of the artifact

360 Cinematic literacy: a case study

360 degree film making necessitates a new language for storytelling. We investigate this issue from the point of view of the user, inferring 360 literacy from what users say about their viewing experiences. The case study is based on material from two user studies on a 360 video profile of an artist. Interviews were analysed using thematic analysis to understand how users made sense of the video. The sense of presence had a strong impact on the experience, while the ability to look around meant new skills had to be developed to try to make sense of 360 video. Viewers had most to say about a few particular shots, and some themes of note emerge: such as being in unusual places, certainty about what should be attended to and focus points, switches between first and third person views, and close-ups and interest

Detection of solvents using a distributed fibre optic sensor

A fibre optic sensor that is capable of distributed detection of liquid solvents is presented. Sensor interrogation using optical time domain reflectometry (OTDR) provides the capability of locating solvent spills to a precision of ±2 m over a total sensor length that may extend to 20 km

Unresolved Unidentified Source Contribution to the Gamma-ray Background

The large majority of EGRET point sources remain without an identified low-energy counterpart, and a large fraction of these sources are most likely extragalactic. Whatever the nature of the extragalactic EGRET unidentified sources, faint unresolved objects of the same class must have a contribution to the diffuse extragalactic gamma-ray background (EGRB). Understanding this component of the EGRB, along with other guaranteed contributions from known sources, is essential if we are to use this emission to constrain exotic high-energy physics. Here, we follow an empirical approach to estimate whether a potential contribution of unidentified sources to the EGRB is likely to be important, and we find that it is. Additionally, we show how upcoming GLAST observations of EGRET unidentified sources, as well as of their fainter counterparts, can be combined with GLAST observations of the Galactic and extragalactic diffuse backgrounds to shed light on the nature of the EGRET unidentified sources even without any positional association of such sources with low-energy counterparts.Comment: 11 pages, 5 figures, submitted to Ap

User experience of panoramic video in CAVE-like and head mounted display viewing conditions

Panoramic 360 video is a rapidly growing part of interactive TV viewing experience due to the increase of both production by consumers and professionals and the availability of consumer headsets used to view it. Recent years have also seen proposals for the development of home systems that could ultimately approximate CAVE-like experiences. The question arises as to the nature of the user experience of viewing panoramic video in head mounted displays compared to CAVE-like systems. User preference seems hard to predict. Accordingly, this study took a qualitative approach to describing user experience of viewing a panoramic video on both platforms, using a thematic analysis. Sixteen users tried both viewing conditions and equal numbers expressed preferences for each display system. The differences in user experience by viewing condition are discussed in detail via themes emerging from the analysis

The Revival of Galactic Cosmic Ray Nucleosynthesis?

Because of the roughly linear correlation between Be/H and Fe/H in low metallicity halo stars, it has been argued that a ``primary'' component in the nucleosynthesis of Be must be present in addition to the ``secondary'' component from standard Galactic cosmic ray nucleosynthesis. In this paper we critically re-evaluate the evidence for the primary versus secondary character of Li, Be, and B evolution, analyzing both in the observations and in Galactic chemical evolution models. While it appears that [Be/H] versus [Fe/H] has a logarithmic slope near 1, it is rather the Be-O trend that directly arises from the physics of spallation production. Using new abundances for oxygen in halo stars based on UV OH lines, we find that the Be-O slope has a large uncertainty due to systematic effects, rendering it difficult to distinguish from the data between the secondary slope of 2 and the primary slope of 1. The possible difference between the Be-Fe and Be-O slopes is a consequence of the variation in O/Fe versus Fe: recent data suggests a negative slope rather than zero (i.e., Fe $\propto$ O) as is often assumed. In addition to a phenomenological analysis of Be and B evolution, we have also examined the predicted LiBeB, O, and Fe trends in Galactic chemical evolution models which include outflow. Based on our results, it is possible that a good fit to the LiBeB evolution requires only traditional the Galactic cosmic ray spallation, and the (primary) neutrino-process contribution to B11. We thus suggest that these two processes might be sufficient to explain Li6, Be, and B evolution in the Galaxy, without the need for an additional primary source of Be and B.Comment: 25 pages, latex, 8 ps figures, figure 1 correcte

Effects of viewing condition on user experience of panoramic video

Panoramic video arises at the convergence of TV and virtual reality, and it is necessary to understand how these technologies interact to affect user experience in order to produce useful content. TV and film makers have developed a sophisticated language and set of techniques to achieve directed linear story telling on fixed screens, whereas virtual worlds more often emphasise user led exploration of possibly non-linear narrative and aspects such as presence and immersion in navigable 3D environments. This study focused on the user experience of panoramic video as viewed over two conditions, on a VR headset and using a handheld phone, and compared this to watching on a static screen thus emphasising the differences between traditional and panoramic TV. A qualitative approach to analysis was taken where users participated in semi-structured interviews. A thematic analysis was performed which produced thematic maps describing user experience for each condition. A detailed and nuanced account of emerging themes is given. Subsequently, key themes were identified and graphed to produce user response profiles to the three viewing conditions that highlight differences in user experience in terms of presence, attention, engagement, concentration on story, certainty, comfort and social eas

Euler buckling and nonlinear kinking of double-stranded DNA

The bending stiffness of double-stranded DNA (dsDNA) at high curvatures is fundamental to its biological activity, yet this regime has been difficult to probe experimentally, and literature results have not been consistent. We created a ‘molecular vise’ in which base-pairing interactions generated a compressive force on sub-persistence length segments of dsDNA. Short dsDNA strands (<41 base pairs) resisted this force and remained straight; longer strands became bent, a phenomenon called ‘Euler buckling’. We monitored the buckling transition via Förster Resonance Energy Transfer (FRET) between appended fluorophores. For low-to-moderate concentrations of monovalent salt (up to ∼150 mM), our results are in quantitative agreement with the worm-like chain (WLC) model of DNA elasticity, without the need to invoke any ‘kinked’ states. Greater concentrations of monovalent salts or 1 mM Mg2+ induced an apparent softening of the dsDNA, which was best accounted for by a kink in the region of highest curvature. We tested the effects of all single-nucleotide mismatches on the DNA bending. Remarkably, the propensity to kink correlated with the thermodynamic destabilization of the mismatched DNA relative the perfectly complementary strand, suggesting that the kinked state is locally melted. The molecular vise is exquisitely sensitive to the sequence-dependent linear and nonlinear elastic properties of dsDNA