Conspicuity of target lights: The influence of flash rate and brightness

The stimulus characteristics of lights that might aid a pilot to see and avoid, by alerting him to a potential threat were studied. The relative conspicuity of foveally equated, point-source, steady and flashing lights of several brightnesses, seen against a star background was examined. From the subject's viewpoint, these target lights could appear anywhere within a large (40 deg horizontal by 35 deg vertical) field of view. The lights appeared at random time intervals while the subject was periodically distracted by a simulated cockpit task. The results indicate that correct target detection increases and reaction time decreases with increased target intensity. Steady lights are missed more frequently and acquired more slowly than flashing lights, but no significant differences are found among the wide range of flash rates employed. The intensity of the light has a greater effect on both detection and reaction time to steady lights than to flashing lights. These results are compared with results of other researchers who used targets which appeared at fixed locations. The longest reaction times were recorded to lights which appeared either at the extremes or at the very center of the visual field

NASA human factors programmatic overview

Human factors addresses humans in their active and interactive capacities, i.e., in the mental and physical activities that they perform and in the contributions they make to achieving the goals of the mission. The overall goal of space human factors in NASA is to support the safety, productivity, and reliability of both the on-board crew and the ground support staff. Safety and reliability are fundamental requirements that human factors shares with other disciplines, while productivity represents the defining contribution of the human factors discipline

Allee Effects May Slow the Spread of Parasites in a Coastal Marine Ecosystem

Allee effects are thought to mediate the dynamics of population colonization, particularly for invasive species. However, Allee effects acting on parasites have rarely been considered in the analogous process of infectious disease establishment and spread. We studied the colonization of uninfected wild juvenile Pacific salmon populations by ectoparasitic salmon lice (Lepeophtheirus salmonis) over a 4-year period. In a data set of 68,376 fish, we observed 85 occurrences of precopular pair formation among 1,259 preadult female and 613 adult male lice. The probability of pair formation was dependent on the local abundance of lice, but this mate limitation is likely offset somewhat by mate-searching dispersal of males among host fish. A mathematical model of macroparasite population dynamics that incorporates the empirical results suggests a high likelihood of a demographic Allee effect, which can cause the colonizing parasite populations to die out. These results may provide the first empirical evidence for Allee effects in a macroparasite. Furthermore, the data give a rare detailed view of Allee effects in colonization dynamics and suggest that Allee effects may dampen the spread of parasites in a coastal marine ecosystem

Issues on combining human and non-human intelligence

The purpose here is to call attention to some of the issues confronting the designer of a system that combines human and non-human intelligence. We do not know how to design a non-human intelligence in such a way that it will fit naturally into a human organization. The author's concern is that, without adequate understanding and consideration of the behavioral and psychological limitations and requirements of the human member(s) of the system, the introduction of artificial intelligence (AI) subsystems can exacerbate operational problems. We have seen that, when these technologies are not properly applied, an overall degradation of performance at the system level can occur. Only by understanding how human and automated systems work together can we be sure that the problems introduced by automation are not more serious than the problems solved

The NASA teleconferencing system: An evaluation

The communication requirements of the Apollo project led to the development of a teleconferencing network which linked together, in an audio-fax mode, the several NASA centers and supporting contractors of the Apollo project. The usefulness of this communication linkage for the Apollo project suggested that the system might be extended to include all NASA centers, enabling them to conduct their in-house business more efficiently than by traveling to other centers. A pilot project was run in which seventeen NASA center and subcenters, some with multiple facilities, were connected into the NASA teleconferencing network. During that year, costs were charted and, at the end of the year, an evaluation was made to determine how the system had been used and with what results. The year-end evaluation of the use of NASA teleconferencing system is summarized

Breaking degeneracy in jet dynamics: multi-epoch joint modelling of the BL Lac PKS 2155-304

Supermassive black holes can launch powerful jets which can be some of the most luminous multi-wavelength sources; decades after their discovery their physics and energetics are still poorly understood. The past decade has seen a dramatic improvement in the quality of available data, but despite this improvement the semi-analytical modelling of jets has advanced slowly: simple one-zone models are still the most commonly employed method of interpreting data, in particular for AGN jets. These models can roughly constrain the properties of jets but they cannot unambiguously couple their emission to the launching regions and internal dynamics, which can be probed with simulations. However, simulations are not easily comparable to observations because they cannot yet self-consistently predict spectra. We present an advanced semi-analytical model which accounts for the dynamics of the whole jet, starting from a simplified parametrization of Relativistic Magnetohydrodynamics in which the magnetic flux is converted into bulk kinetic energy. To benchmark the model we fit six quasisimultaneous, multi-wavelength spectral energy distributions of the BL Lac PKS 2155-304 obtained by the TANAMI program, and we address the degeneracies inherent to such a complex model by employing a state-of-the-art exploration of parameter space, which so far has been mostly neglected in the study of AGN jets. We find that this new approach is much more effective than a single-epoch fit in providing meaningful constraints on model parameters.Comment: Accepted for publication on MNRA

The jet-disk symbiosis without maximal jets: 1-D hydrodynamical jets revisited

In this work we discuss the recent criticism by Zdziarski of the maximal jet model derived in Falcke & Biermann (1995). We agree with Zdziarski that in general a jet's internal energy is not bounded by its rest-mass energy density. We describe the effects of the mistake on conclusions that have been made using the maximal jet model and show when a maximal jet is an appropriate assumption. The maximal jet model was used to derive a 1-D hydrodynamical model of jets in agnjet, a model that does multiwavelength fitting of quiescent/hard state X-ray binaries and low-luminosity active galactic nuclei. We correct algebraic mistakes made in the derivation of the 1-D Euler equation and relax the maximal jet assumption. We show that the corrections cause minor differences as long as the jet has a small opening angle and a small terminal Lorentz factor. We find that the major conclusion from the maximal jet model, the jet-disk symbiosis, can be generally applied to astrophysical jets. We also show that isothermal jets are required to match the flat radio spectra seen in low-luminosity X-ray binaries and active galactic nuclei, in agreement with other works.Comment: 7 pages, accepted by A&

The Deserving And Undeserving: Examining Ontario\u27s New Strategy For Organ And Tissue Donation

The medical marvel of organ and tissue transplantation has spurred new questions about the divisible body and its potential for commodification, dividing the world into unequal populations —receivers and donors. Efforts to foster equilibrium in the supply and demand of transplantable organs have led many to argue for market-based solutions; however the role of privilege has often been made invisible in these discussions, exacerbating pre-existing global inequalities. This paper acknowledges Canadian patient engagement in systems of organ trafficking, and explores the current strategy enacted by Trillium Gift of Life Network (TGLN) to improve organ and tissue donation and transplantation (OTDT) in Ontario and its potential to mitigate transplant tourism. Using an institutional ethnographic approach, the focal point of this research is an examination of the primary texts produced by TGLN. Proposals supporting a legal market for organs are also addressed, including their conflict with the Canadian Medicare system, which was established to prevent the allocation of health care services based on ability to pay. Significantly, TGLN upholds this principle and emphasizes the value in altruistic donation and decommodified approaches to OTDT. If successful, TGLN could lead the way for improving systems of OTDT in Canada. However, concerning themes have been identified which can be understood as barriers to the success of TGLN and thus impede its efforts to increase donation, develop adequate infrastructure with which to effectively procure and allocate organs and tissues, and reduce incidence of Canadian patient participation in transplant tourism

A study of the emotional problems of patients on a diagnostic service.

Includes 5 tables and 2 figures. Thesis (M.S.)--Boston Universit