Jorge A. Santos

The effect of instruction to synchronize over step frequency while walking with auditory cues on a treadmill

Walking to a pacing stimulus has proven useful in motor rehabilitation, and it has been suggested that spontaneous synchronization could be preferable to intentional synchronization. But it is still unclear if the paced walking effect can occur spontaneously, or if intentionality plays a role. The aim of this work is to analyze the effect of sound pacing on gait with and without instruction to synchronize, and with different rhythmic auditory cues, while walking on a treadmill. Firstly, the baseline step frequency while walking on a treadmill was determined for all participants, followed by experimental sessions with both music and footstep sound cues. Participants were split into two groups, with one being instructed to synchronize their gait to the auditory stimuli, and the other being simply told to walk. Individual auditory cues were generated for each participant: for each trial, cues were provided at the participants baseline walking frequency, at 5% and 10% above baseline, and at 5% and 10% below baseline. This studys major finding was the role of intention on synchronization, given that only the instructed group synchronized their gait with the auditory cues. No differences were found between the effects of step or music stimuli on step frequency. In conclusion, without intention or cues that direct the individuals attention, spontaneous gait synchronization does not occur during treadmill walking.

Noise abatement and traffic safety: The trade-off of quieter engines and pavements on vehicle detection

Road traffic sounds are a major source of noise pollution in urban areas. But recent developments such as low noise pavements and hybrid/electric engine vehicles cast an optimistic outlook over such an environmental problem. However, it can be argued that engine, tire, and road noise could be relevant sources of information to avoid road traffic conflicts and accidents. In this paper, we analyze the potential trade-offs of traffic-noise abatement approaches in an experimental study, focusing for the first time on the impact and interaction of relevant factors such as pavement type, vehicle type, listeners age, and background noise, on vehicle detection levels. Results reveal that vehicle and pavement type significantly affect vehicle detection. Age is a significant factor, as both younger and older people exhibit lower detection levels of incoming vehicles. Low noise pavements combined with all-electric and hybrid vehicles might pose a severe threat to the safety of vulnerable road users. All factors interact simultaneously, and vehicle detection is best predicted by the loudness signal-to-noise ratio.

Optical flow techniques applied to the calibration of visual perception experiments

In this paper we present an evaluation of optical flow techniques applied to a case study in the perception of visual motion. This case study is being conducted in a project for the evaluation of human factors in road traffic, specifically, concerning the processing of visual information. We present the goals of the case study, discuss the need to apply optical flow techniques to synthesized image sequences and evaluate some limitations encountered in their use.

Learning auditory space: Generalization and Long-Term Effects

Background Previous findings have shown that humans can learn to localize with altered auditory space cues. Here we analyze such learning processes and their effects up to one month on both localization accuracy and sound externalization. Subjects were trained and retested, focusing on the effects of stimulus type in learning, stimulus type in localization, stimulus position, previous experience, externalization levels, and time. Method We trained listeners in azimuth and elevation discrimination in two experiments. Half participated in the azimuth experiment first and half in the elevation first. In each experiment, half were trained in speech sounds and half in white noise. Retests were performed at several time intervals: just after training and one hour, one day, one week and one month later. In a control condition, we tested the effect of systematic retesting over time with post-tests only after training and either one day, one week, or one month later. Results With training all participants lowered their localization errors. This benefit was still present one month after training. Participants were more accurate in the second training phase, revealing an effect of previous experience on a different task. Training with white noise led to better results than training with speech sounds. Moreover, the training benefit generalized to untrained stimulus-position pairs. Throughout the post-tests externalization levels increased. In the control condition the long-term localization improvement was not lower without additional contact with the trained sounds, but externalization levels were lower. Conclusion Our findings suggest that humans adapt easily to altered auditory space cues and that such adaptation spreads to untrained positions and sound types. We propose that such learning depends on all available cues, but each cue type might be learned and retrieved differently. The process of localization learning is global, not limited to stimulus-position pairs, and it differs from externalization processes.

Treatment of Morbid Obesity with Adjustable Gastric Band: Preliminary Report

Background: The goal of surgery for morbid obesity is to achieve a good and durable loss of weight and improve health. Previous studies have demonstrated a significant weight loss for the Swedish adjustable gastric band (SAGB). Patients and Methods: Between November 1996 and April 1998, 18 morbidly obese patients underwent SAGB laparoscopically. Their mean age at surgery was 35 years. The mean preoperative weight was 128 kg (range 89-163), and the mean body mass index was 50.4 ± 9. Comorbidity was present in 13 patients. Results: One gastric perforation occurred, and in one patient it was not possible to create the pneumoperitoneum. Regarding late morbidity, one intragastric migration and one slippage of the band occurred. There was no mortality. Conclusion: The low morbidity, the good results with weight loss, and the improvement in comorbidity lead the authors to believe that Swedish adjustable gastric banding for the treatment of morbidly obese patients is a successful means of losing weight and improving general health.

Depth Cues and Perceived Audiovisual Synchrony of Biological Motion

Background Due to their different propagation times, visual and auditory signals from external events arrive at the human sensory receptors with a disparate delay. This delay consistently varies with distance, but, despite such variability, most events are perceived as synchronic. There is, however, contradictory data and claims regarding the existence of compensatory mechanisms for distance in simultaneity judgments. Principal Findings In this paper we have used familiar audiovisual events – a visual walker and footstep sounds – and manipulated the number of depth cues. In a simultaneity judgment task we presented a large range of stimulus onset asynchronies corresponding to distances of up to 35 meters. We found an effect of distance over the simultaneity estimates, with greater distances requiring larger stimulus onset asynchronies, and vision always leading. This effect was stronger when both visual and auditory cues were present but was interestingly not found when depth cues were impoverished. Significance These findings reveal that there should be an internal mechanism to compensate for audiovisual delays, which critically depends on the depth information available.

Distributed Computation of Optical Flow

This paper describes a new parallel algorithm to compute the optical flow of a video sequence. A previous sequential algorithm has been distributed over a cluster. It has been implemented in a cluster with 8 nodes connected by means of a Gigabit Ethernet. On this architecture, the algorithm, that computes the optical flow of every image on the sequence, is able of processing 10 images of 720x576 pixels per second.

Parallel Computation of Optical Flow

This paper describes a new parallel algorithm to compute the optical flow of a video sequence. A previous sequential algorithm has been distributed over a cluster. It has been implemented in a cluster with 8 nodes connected by means of a Gigabit Ethernet. On this architecture, the algorithm, that computes the optical flow of every image on the sequence, is able of processing 10 images of 720 × 576 pixels per second.

FONTE: A Protégé Plug-in for Engineering Complex Ontologies

Humans have a natural ability to reason about scenarios including spatial and temporal information but for several reasons the process of developing complex ontologies including time and/or space is still not well developed and it remains an one-off, labour intensive experience. In this paper we present Fonte (Factorising ONTology Engineering complexity), an ontology engineering methodology that relies on a divide and conquer strategy. The targeted complex ontology is built by assembling modular ontologies that capture temporal, spatial and domain (atemporal and aspatial) aspects. In order to support the proposed methodology we developed a plug-in for Protege.

Monitoring system of discomfort in disability, bed rest people and surgical patients

Project aims to develop a system that allows to provide to the people with special needs (PSN) a relief to the level of the sensitive perception of discomfort, assuring greater independence, welfare, quality of life, prevention of illnesses/wounds, through the development of textile and polymers applications (cushions, mattresses and mattresses overlays) with functions of monitoring of pressure in the bodys areas in contact with the support surfaces. In this group of PSN will be enclosed the people with serious motor limitations that condition their mobility/deambulation, such as bed rest people, patients under effect of sedatives or anesthesia during long surgeries (intra and post operative), patients and users in general of wheelchairs. These people have, for the most part of the cases, a commitment of sensitivity in the bodys areas in contact with the support surfaces, or its motor capacity does not allow them to move regularly of position autonomously, as it would do a healthy person unconsciously. Than, insufficient sanguineous irrigation occurs as result of pressure exceeding too long the tissue capillary pressure depriving tissues of oxygen and essential nutrients, owing to ischemia and hypoxia, which then causes the pressure ulcers (UP) development.