Presence Of Depth Research Articles

Repetitive dynamic stereo test improved processing time in young athletes.

Current studies revealed the importance of perceptual training for the treatment of amblyopia. To improve stereo vision on a higher level, visual tasks have to be completed within a limited time window like in repetitive visual function tests. "Processing time" as the reaction time in which the absence or presence of depth was identified correctly, is of better predictive value for perceiving the depth than the stereo threshold only. To examine the long-term effects of repetitive dynamic testing of stereopsis on processing time. 15 male soccer athletes (13.3±3.2 years) underwent twelve sessions of a 15 minutes repetitive dynamic stereovision training over a period of six weeks, presented on a polarized 3D-TV in a four-alternative forced choice setup. We measured the response time of correct identified visual tasks of 11, 22, 44, 55, 66, 77 and 88arcsecs disparity before, after six sessions, after twelve sessions and after six month without testing. As response time is the sum of stereo processing time plus the motor reaction time, we defined the difference between the response times at 11 and 88arcsecs as "stereo processing time at 11arcsecs". A Wilcoxon Signed Rank Test was conducted between the testing sessions to evaluate significant changes in response time and stereo processing time. After six sessions the mean stereo processing time at 11arcsecs decreased significantly from 804.4 ms to 403.7 ms (Z = -2.499, p = 0.012). Six months after the last training the stereo processing time at 11arcsecs remained at the level of the last session. Our results suggest that repetitive testing of stereovision is effective in improving processing time of stereoscopic tasks in young male athletes significantly long-term.

Directional wave spectrum transformation in the presence of strong depth and current inhomogeneities by means of coupled-mode model

A variety of engineering applications, including interaction of waves with coastal fixed or floating structures, coastal morphodynamics and harbour maintenance, requires detailed information about nearshore and onshore wave conditions. Since information concerning sea states is usually available offshore, there is need for developing appropriate models transforming the offshore wave conditions to nearshore ones. In the present work, a fully dispersive coupled-mode model is exploited to implement an offshore to nearshore wave spectrum transformation, in the presence of depth and current inhomogeneities. This model is based on appropriate local-mode series expansions, containing the propagating and evanescent modes, plus an additional term enabling the satisfaction of the boundary condition on the sloping parts of the bottom. The wave spectrum transformation is achieved by defining and calculating a distributed transfer function, connecting incident wave components with wave conditions at each point in the domain. The model takes full account of reflection, refraction, and diffraction phenomena, due to strongly varying, 3D bottom topography and ambient currents, as well as dissipation of wave energy due to bottom friction and wave breaking. Numerical results are compared with results obtained by other methods and experimental data, demonstrating the usefulness and practical applicability of the present approach.

Population-specific shifts in viral and microbial abundance within a cryptic upwelling

Coastal upwelling systems play an essential role in bringing cold and nutrient-rich water into the euphotic zone, hence enhancing the biological productivity of the world's oceans. We describe a “cryptic” upwelling occurring in South Australian waters, in which cold upwelled waters do not reach surface waters and do not exhibit a sea surface temperature (SST) signature. Due to the wide continental shelf (ca. 100km), upwelled waters form a sub-surface cold water pool and are forced north-west after a secondary event. Using flow cytometry we investigated the abundance and composition of viruses, heterotrophic bacteria and pico-phytoplankton within upwelling affected and unaffected waters. Our results identified the presence of upwelled waters at and below the Deep-Chlorophyll Maximum (DCM), where water temperature was at least 4°C colder than surface waters. In contrast to previous studies, no significant differences were observed between upwelled and non-upwelled waters for most individual viral, bacterial and pico-phytoplankton sub-groups. However, one viral, one bacterial and two pico-phytoplankton sub-groups were significantly more abundant at the DCM. This indicates the presence of depth- and population-specific shifts in abundance and potential niche partitioning of these cytometrically-defined sub-groups that may be related to their host organisms and/or resource availability.