Looking through the crowded mask: investigating the effect of distractor number and position in object substitution masking

Object substitution masking (OSM) is a phenomenon wherein a surrounding mask (typically four dots) that onsets with a target but lingers after its offset significantly reduces target perceptibility. OSM was originally postulated to occur only when spatial attention was spread (Di Lollo et al., 2000). Specifically, it was claimed that OSM only occurred when the target was presented in the context of large set-size displays (Di Lollo et al., 2000). However, more recent research has raised questions over the relevance of set size in OSM. Two separate investigations (Argyropoulos et al., 2013; Filmer et al., 2014) found that strong masking by OSM could be produced even with a set size of one. It was argued that the “set size” effects in OSM were actually an artifact of constrained performance. That is, once performance was brought within a measurable range, OSM was reported to be independent of set size. Further research however has suggested that perhaps this rejection of the role of set size in OSM was premature. Pilling (2013) found that increased set size did in fact lead to greater OSM magnitude. Therefore it seems that an explanation of constrained performance cannot fully account for the experimental findings. This thesis begins by investigating the disparity between these results by further exploring the role of set size in OSM. The first chapter provides an overview of some of the constraints for perceptual awareness by examining experimental phenomena that prevent visual awareness. The experimental phenomena of visual masking and specifically OSM are focused on with particular focus given to the role of attention in OSM. Chapter 2 is the first experimental chapter. This chapter investigates the role of set size in OSM using five experiments. Chapter 3 explores if visual crowding can be used as an alternative explanation for the set size effects in OSM with five experiments. Chapter 4 attempts to investigate the neural underpinnings of OSM, and the interaction between OSM and crowding using an EEG method. This thesis proposes, based on its findings, that the nominal set size effect in OSM is actually an effect of crowding, a factor which tends to co-vary with set size in most studies. Further experiments in this thesis showed that the interaction between crowding and OSM was one in which OSM affected crowding rather than the converse process. That is, with the use of OSM, the window at which flankers crowd the target becomes extended. These findings show parallels with the previously reported phenomenon of “supercrowding” which has been reported with classical masking. Given this, these results challenge claims regarding the position of OSM and crowding in the object processing hierarchy (e.g. Breitmeyer, 2014). This thesis contributes to the ongoing investigation of OSM, provides implications for its existing theories and for accounts of object processing more generally as well as highlighting future directions for research in this field

Wind shear modeling for aircraft hazard definition

Mathematical models of wind profiles were developed for use in fast time and manned flight simulation studies aimed at defining and eliminating these wind shear hazards. A set of wind profiles and associated wind shear characteristics for stable and neutral boundary layers, thunderstorms, and frontal winds potentially encounterable by aircraft in the terminal area are given. Engineering models of wind shear for direct hazard analysis are presented in mathematical formulae, graphs, tables, and computer lookup routines. The wind profile data utilized to establish the models are described as to location, how obtained, time of observation and number of data points up to 500 m. Recommendations, engineering interpretations and guidelines for use of the data are given and the range of applicability of the wind shear models is described

STS-31 Space Shuttle mission report

The STS-31 Space Shuttle Program Mission Report contains a summary of the vehicle subsystem activities on this thirty-fifth flight of the Space Shuttle and the tenth flight of the Orbiter Vehicle Discovery (OV-103). In addition to the Discovery vehicle, the flight vehicle consisted of an External Tank (ET) (designated as ET-34/LWT-27), three Space Shuttle main engines (SSME's) (serial numbers 2011, 2031, and 2107), and two Solid Rocket Booster (SRB) (designated as BI-037). The primary objective of the mission was to place the Hubble Space Telescope (HST) into a 330 nmi. circular orbit having an inclination of 28.45 degrees. The secondary objectives were to perform all operations necessary to support the requirements of the Protein Crystal Growth (PCG), Investigations into Polymer Membrane Processing (IPMP), Radiation Monitoring Equipment (RME), Ascent Particle Monitor (APM), IMAX Cargo Bay Camera (ICBC), Air Force Maui Optical Site Calibration Test (AMOS), IMAX Crew Compartment Camera, and Ion Arc payloads. In addition, 12 development test objectives (DTO's) and 10 detailed supplementary objectives (DSO's) were assigned to the flight. The sequence of events for this mission is shown. The significant problems that occurred in the Space Shuttle Orbiter subsystems during the mission are summarized, and the official problem tracking list is presented. In addition, each of the Space Shuttle Orbiter problems is cited in the subsystem discussion

STS-41 Space Shuttle mission report

The STS-41 Space Shuttle Program Mission Report contains a summary of the vehicle subsystem activities on this thirty-sixth flight of the Space Shuttle and the eleventh flight of the Orbiter vehicle, Discovery (OV-103). In addition to the Discovery vehicle, the flight vehicle consisted of an External Tank (ET) (designated as ET-39/LWT-32), three Space Shuttle main engines (SSME's) (serial numbers 2011, 2031, and 2107), and two Solid Rocket Boosters (SRB's), designated as BI-040. The primary objective of the STS-41 mission was to successfully deploy the Ulysses/inertial upper stage (IUS)/payload assist module (PAM-S) spacecraft. The secondary objectives were to perform all operations necessary to support the requirements of the Shuttle Backscatter Ultraviolet (SSBUV) Spectrometer, Solid Surface Combustion Experiment (SSCE), Space Life Sciences Training Program Chromosome and Plant Cell Division in Space (CHROMEX), Voice Command System (VCS), Physiological Systems Experiment (PSE), Radiation Monitoring Experiment - 3 (RME-3), Investigations into Polymer Membrane Processing (IPMP), Air Force Maui Optical Calibration Test (AMOS), and Intelsat Solar Array Coupon (ISAC) payloads. The sequence of events for this mission is shown in tabular form. Summarized are the significant problems that occurred in the Orbiter subsystems during the mission. The official problem tracking list is presented. In addition, each Orbiter problem is cited in the subsystem discussion

Arm cavity resonant sideband control for laser interferometric gravitational wave detectors

We present a new optical control scheme for a laser interferometric gravitational wave detector that has a high degree of tolerance to interferometer spatial distortions and noise on the input light. The scheme involves resonating the rf sidebands in an interferometer arm cavity

Influence of the 5' intron in the control of acetylcholinesterase gene expression during myogenesis.

During myogenesis, marked increases in both acetylcholinesterase (AChE) and its encoding mRNA are observed. The intron in the AChE gene between non-coding exon 1 [T.L. Rachinsky, S. Camp, Y. Li, T.J. Ekstrom, M. Newton, P. Taylor, Molecular cloning of mouse acetylcholinesterase: tissue distribution of alternatively spliced mRNA species, Neuron 5 (1990) 317-327] and start-site containing exon 2 [A. Mutero, S. Camp, P. Taylor, Promoter elements of the mouse acetylcholinesterase gene, J. Biol. Chem. 270 (4) (1995) 1866-1872] appears to be responsible for the enhanced expression of the enzyme upon myoblast to myotube differentiation. Deletion of a 255 bp sequence within the first intron of the AChE gene abolishes the increase in cell-associated activity observed with differentiation. To study the involvement of the intronic region in post-transcriptional processing of AChE message, we used real time RT-PCR to quantify spliced and unspliced message levels in myoblasts and myotubes. We observe a 200-fold increase of the fully spliced mRNA associated with myotube formation, while the increase in the unspliced mRNA retaining either intron 1 or intron 2 is only 5 to 15-fold. We have generated knockout mice without the conserved region of intron 1. The mice show a phenotype where skeletal muscle, hematopoietic and central nervous system AChE expression differ with the greatest effect existing in the disappearance of skeletal muscle expression [S. Camp, L Zhang, M. Marquez, B. de La Torre, J.M. Long, G. Bucht, P. Taylor, Acetylcholinesterase (AChE) gene modification in transgenic animals: functional consequences of selected exon and regulatory region deletion, VIII IMC Proceedings]