Wide-angle flat field telescope

Described is an unobscured three mirror wide angle telescopic imaging system comprised of an input baffle which provides a 20 deg (Y axis) x 30 deg (X axis) field of view, a primary mirror having a convex spherical surface, a secondary mirror having a concave ellipsoidal reflecting surface, a tertiary mirror having a concave spherical reflecting surface. The mirrors comprise mirror elements which are offset segments of parent mirrors whose axes and vertices commonly lie on the system's optical axis. An iris diaphragm forming an aperture stop is located between the secondary and tertiary mirror with its center also being coincident with the optical axis and being further located at the beam waist of input light beams reflected from the primary and secondary mirror surfaces. At the system focus following the tertiary mirror is located a flat detector which may be, for example, a TV imaging tube or a photographic film. When desirable, a spectral transmission filter is placed in front of the detector in close proximity thereto

High spectral resolution time-resolved optical spectroscopy of V893 Sco

We present high resolution time-resolved optical spectra of the high inclination short orbital period dwarf nova V893 Sco. We performed spectral analysis through radial velocity measurements, Doppler mapping, and ratioed Doppler maps. Our results indicate that V893 Sco's accretion disk is dissimilar to WZ Sge's accretion disk, and does not fit any of the current accretion disk models. We derive the system parameters M1 and i, and present evidence for V893 Sco as a very young cataclysmic variable and an ER UMa star. We advance the hypothesis that all ER UMa stars may be newly formed cataclysmic variables.Comment: 23 pages (total), 8 figures, accepted by Ap

Macroscopic modelling of the surface tension of polymer-surfactant systems

Polymer-surfactant mixtures are increasingly being used in a wide range of applications. Weakly-interacting systems, such as SDS/PEO and SDS/PVP, comprise ionic surfactants and neutral polymers, while strongly-interacting systems, such as SDS/POLYDMDAAC and C12TAB/NaPSS, comprise ionic surfactants and oppositely charged ionic polymers. The complex nature of interactions in the mixtures leads to interesting and surprising surface tension profiles as the concentrations of polymer and surfactant are varied. The purpose of our research has been to develop a model to explain these surface tension profiles and to understand how they relate to the formation of different complexes in the bulk solution. In this paper we shouw how an existing model based on the law of mass action can be extended to model the surface tension of weakly-interacting systems, and we also extend it further to produce a model for the surface tension of strongly interacting systems. Applying the model to a variety of strongly-interacting systems gives remarkable agreement with the experimental results. The model provides a sound theoretical basis for comparing and contrasting the behaviour of different systems and greatly enhances our understanding of the features observed

Cold‐water coral assemblages on vertical walls from the Northeast Atlantic

Aim In this study, we assess patterns of cold‐water coral assemblages observed on deep‐sea vertical walls. Similar to their shallow‐water counterparts, vertical and overhanging walls in the deep sea can host highly diverse communities, but because of their geometry, these habitats are generally overlooked and remain poorly known. These vertical habitats are however of particular interest, because they can protect vulnerable coral ecosystems from trawling activities. As such, it is important to understand their ecology and assess their global importance. Location Vertical walls on complex geomorphic features, in particular walls of the Rockall Bank Slope Failure Escarpment, Whittard and Explorer Canyons, Northeast Atlantic. Methods Video analysis of remotely operated vehicle transects carried out at five sites is used to investigate differences in species composition and diversity across walls and to compare those to nearby cold‐water coral sites on flat terrain. A high‐resolution photogrammetric reconstruction is further employed to examine whether wall complexity plays a role in promoting niche differentiation at very fine spatial scales. Results The investigated walls showed differences in species assemblage both across walls and in comparison to flat sites, with the fine‐scale heterogeneity engendered by walls allowing niche differentiation between closely related taxa. Main Conclusions Vertical walls represent an important cold‐water coral habitat with differences in species composition across walls within a region, illustrating their role in driving diversity patterns. Based on publicly available bathymetric datasets and a catalogue of broad‐scale terrain features, globally over 8,000 features are likely to have vertical walls and cold‐water corals, which highlight the need to consider deep‐sea vertical habitats in current conservation efforts

Interferometric weak value deflections: quantum and classical treatments

We derive the weak value deflection given in a paper by Dixon et al. (Phys. Rev. Lett. 102, 173601 (2009)) both quantum mechanically and classically. This paper is meant to cover some of the mathematical details omitted in that paper owing to space constraints

Heliocentric Escape and Lunar Impact from Near Rectilinear Halo Orbits

Spacecraft departing from the Gateway in a Near Rectilinear Halo Orbit (NRHO) experience gravitational forces from the Moon, the Earth, and the Sun, all of which can be simultaneously significant. These complex dynamics influence the post-separation risk of recontact with the Gateway and the eventual destinations of the departing spacecraft. The current investigation examines the flow of objects leaving NRHOs in the Bicircular Restricted Four-Body Problem, and results are applied to heliocentric escape and lunar impact trajectories in a higher-fidelity ephemeris model. Separation maneuver magnitude, direction, and location are correlated with risk of recontact with the Gateway and successful departure to various destinations

Early Identification of Violent Criminal Gang Members

Gang violence is a major problem in the United States accounting for a large fraction of homicides and other violent crime. In this paper, we study the problem of early identification of violent gang members. Our approach relies on modified centrality measures that take into account additional data of the individuals in the social network of co-arrestees which together with other arrest metadata provide a rich set of features for a classification algorithm. We show our approach obtains high precision and recall (0.89 and 0.78 respectively) in the case where the entire network is known and out-performs current approaches used by law-enforcement to the problem in the case where the network is discovered overtime by virtue of new arrests - mimicking real-world law-enforcement operations. Operational issues are also discussed as we are preparing to leverage this method in an operational environment.Comment: SIGKDD 201

Intervention for word-finding difficulty for children starting school who have diverse language backgrounds

Children who have word-finding difficulty can be identified by the pattern of disfluencies in their spontaneous speech; in particular whole-word repetition of prior words often occurs when they cannot retrieve the subsequent word. Work is reviewed that shows whole-word repetitions can be used to identify children from diverse language backgrounds who have word-finding difficulty. The symptom-based identification procedure was validated using a non-word repetition task. Children who were identified as having word-finding difficulty were given phonological training that taught them features of English that they lacked (this depended on their language background). Then they received semantic training. In the cases of children whose first language was not English, the children were primed to use English and then presented with material where there was interference in meanings across the languages (English names had to be produced). It was found that this training improved a range of outcome measures related to education