Communications Biophysics

Contains reports on two research projects.National Science Foundation (Grant G-16526)National Institutes of Health (Grant MH-04737-03)National Aeronautics and Space Administration (Grant NsG-496

Human sensitivity to gearshift loads

This paper describes an investigation of the ability of humans to distinguish different levels of gearlever load. A test rig with a forward-backward moving gearshift lever was constructed using the typical interior dimensions of European B segment automobiles. The rig used a system of weights and pulleys to provide a load which could be varied in steps of 1%. Four reference loads were chosen which were considered representative of automotive gearshift operation: 0.5, 1.0, 2.0 and 5.0 kg. Twenty subjects took part in the study. Using a variation on the psychophysical method of limits, the subjects were asked to respond whether a test load was heavier or lighter than a reference load. The Weber Fraction was found to decrease monotonically from a value of 0.036 for the 0.5 kg reference load to a value of 0.029 at the 5.0 kg reference load. The average value across all reference loads was 0.032. Measurements of the gearshift force made by means of a knob containing a load cell suggested that the variation in the measured Weber Fraction might be attributable to the time behaviour of the force exchanged between the human subject and the control surface

A National Research Agenda for Virtual Reality: Report by the National Research Council Committee on VR R&D

In 1992, at the request of a consortium of federal agencies, the National Research Council established a committee to "recommand a national research and development agenda in the area of virtual reality" to set U.S. government R&D funding priorities for virtual reality (VR) for the next decade...

Communications Biophysics

Contains reports on two research projects.National Institutes of Health (Grant 1 PO1 GM-14940-02)Joint Services Electronics Programs (U. S. Army, U. S. Navy, and U. S. Air Force) under Contract DA 28-043-AMC-02536(E

Congenital toxoplasmosis: Serology, PCR, parasite isolation and molecular characterization of toxoplasma gondii

Introducción El diagnóstico de toxoplasmosis congénita (TC) en el recién nacido es muy importante porque debe recibir tratamiento siempre, sintomático o no, para evitar o aminorar las secuelas de la enfermedad. Objetivo Evaluación comparativa de los métodos disponibles en la institución para el diagnóstico de TC. Materiales y Métodos Se evaluaron métodos diagnósticos en 67 niños cuyas madres cursaron toxoplasmosis aguda durante el embarazo. Se utilizó la técnica de Sabin Feldman para IgG al nacimiento y durante el seguimiento serológico hasta el año de vida. Para determinar IgM, IgA e IgE se utilizó la técnica immunosorbent agglutination assay (ISAGA). El diagnóstico directo se realizó por reacción de polimerasa en cadena (RPC), aislamiento y caracterización molecular del parásito. Resultados La sensibilidad (S) de ISAGA IgM fue 87%, ISAGA IgA 91% y la especificidad (E) fue 100% para ambas; cuando se realizaron en conjunto, la S aumentó a 98%. La detección de IgE contribuyó al diagnóstico cuando se la detectó sólo en la sangre del neonato y no en sangre materna. Se aisló el parásito en cuatro casos de TC, uno fue genotipo II y los otros tres, genotipos “atípicos”. La S del aislamiento fue 80% y la E 100%. Conclusión Los métodos serológicos utilizados mostraron una buena eficacia diagnóstica. Un caso fue detectado sólo por el aislamiento y la caracterización molecular tiene gran valor epidemiológico.Background. Congenital toxoplasmosis diagnosis in the newborn is a very important issue due to the need for early treatment to prevent future sequels. Aim To compare available methods at the institution for the diagnosis of congenital toxoplasmosis. Material and Methods In this study we have evaluated the different diagnostic tests used in 67 congenital exposed newborns, including serological tests, PCR, parasite isolation and molecular characterization. Results The ISAGA IgM and IgA tests showed sensitivity (Se) of 87 and 91%, respectively, and specificity (Sp) of 100%. When ISAGA IgM and IgA were performed simultaneously, the Se increased to 98% and the Sp was 100%. The presence of IgE contributed to the diagnosis when it was detected in the child's serum but not in maternal blood. In four congenital infected children the parasite was isolated and genotyped: one was genotype II and the other three were “atypical” genotypes. No parasite was isolated in children without congenital toxoplasmosis. Discussion Overall, serological tests showed a good diagnostic performance although in one case they were all negative and isolation was the only tool to identify the infection. We conclude that it is essential to use all diagnostic tests in every single exposed child, including if possible, molecular characterization due to its epidemiological implication.Fil: Carral, Liliana. Hospital Aleman; ArgentinaFil: Kaufer, Federico. Hospital Aleman; ArgentinaFil: Pardini, Lais Luján. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Departamento de Epizootiología y Salud Pública. Laboratorio de Inmunoparasitología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Durlach, Ricardo. Hospital Aleman; ArgentinaFil: Moré, Gastón Andrés. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Departamento de Epizootiología y Salud Pública. Laboratorio de Inmunoparasitología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Venturini, María C.. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Departamento de Epizootiología y Salud Pública. Laboratorio de Inmunoparasitología; ArgentinaFil: Freuler, Cristina. Hospital Aleman; Argentin

Effects of Reapeated Doses of Caffeine on Performance and Alertness: New Data and Secondary Analyses

Rationale The effects of caffeine on mood and performance are well established. Some authors suggest that caffeine merely reverses effects of caffeine withdrawal rather than having direct behavioural effects. It has also been suggested that withdrawal may be removed by a first dose of caffeine and further doses have little subsequent effect. These issues were examined here. Objectives The present study aimed to determine whether caffeine withdrawal influenced mood and performance by comparing regular consumers who had been withdrawn from caffeine overnight with non-consumers. Following this repeated caffeine doses were administered to test the claim that repeated dosing has no extra effect on mood or performance. Secondary analyses of a data collected by Christopher et al. (2003) were also carried out to examine some alternative explanations of their results which showed effects of caffeine after a day of normal caffeine consumption. Methods One hundred and twenty volunteers participated in the study. Regular caffeine consumption was assessed by questionnaire and this showed that thirty six of the sample did not regularly consume caffeinated beve rages. Volunteers were instructed to abstain from caffeine overnight and then completed a baseline session measuring mood and a range of cognitive functions at 08.00 the next day. Following this volunteers were given 0, or 1mg/kg caffeine in a milkshake, glucose solution or water (at 09:00), followed by a second 0 or 1mg/kg caffeine dose (at 09:40) and the test battery repeated at 10:00. Results The baseline data showed no effect of overnight caffeine withdrawal on mood or performance. In contrast, caffeine challenge improved vigilance performance and prevented decreases in alertness induced by completion of the task battery. The magnitude of these effects increased as a function of the number of doses of caffeine given. Secondary analyses of data from Christopher et al. (2003) also confirmed that effects of caffeine did not depend on length of withdrawal. Conclusions The present findings show no effect of overnight caffeine withdrawal on mood and performance. Caffeine challenge did have the predicted effect on alertness and vigilance, with the size of the effects increasing with caffeine dose. These findings suggest that the effects of caffeine are not due to reversal of effects of withdrawal, a view confirmed by secondary analyses of data collected after a day of normal caffe ine consumption

Multi-Modal Perception for Selective Rendering

A major challenge in generating high-fidelity virtual environments (VEs) is to be able to provide realism at interactive rates. The high-fidelity simulation of light and sound is still unachievable in real-time as such physical accuracy is very computationally demanding. Only recently has visual perception been used in high-fidelity rendering to improve performance by a series of novel exploitations; to render parts of the scene that are not currently being attended to by the viewer at a much lower quality without the difference being perceived. This paper investigates the effect spatialised directional sound has on the visual attention of a user towards rendered images. These perceptual artefacts are utilised in selective rendering pipelines via the use of multi-modal maps. The multi-modal maps are tested through psychophysical experiments to examine their applicability to selective rendering algorithms, with a series of fixed cost rendering functions, and are found to perform significantly better than only using image saliency maps that are naively applied to multi-modal virtual environments

Communications Biophysics

Contains reports on six research projects.National Institutes of Health (Grant 2 P01 GM-14940-01)Joint Services Electronics Programs (U. S. Army, U.S. Navy, and U.S. Air Force) under Contract DA 28-043-AMC-02536(E)National Aeronautics and Space Administration (Grant NsG-496)National Institutes of Health (Grant 2 ROl NB-05462-03

Communication Biophysics

Contains reports on five research projects.National Science Foundation (Grant GP-2495)National Institutes of Health (Grant MH-04737-04)National Aeronautics and Space Administration (Grant NsG-496

Reducing reversal errors in localizing the source of sound in virtual environment without head tracking

International audienceThis paper presents a study about the effect of using additional audio cueing and Head-Related Transfer Function (HRTF) on human performance in sound source localization task without using head movement. The existing techniques of sound spatialization generate reversal errors. We intend to reduce these errors by introducing sensory cues based on sound effects. We conducted and experimental study to evaluate the impact of additional cues in sound source localization task. The results showed the benefit of combining the additional cues and HRTF in terms of the localization accuracy and the reduction of reversal errors. This technique allows significant reduction of reversal errors compared to the use of the HRTF separately. For instance, this technique could be used to improve audio spatial alerting, spatial tracking and target detection in simulation applications when head movement is not included