Trabecular Meshwork Motion Profile from Pulsatile Pressure Transients: A New Platform to Simulate Transitory Responses in Humans and Nonhuman Primates

Trabecular meshwork (TM) motion abnormality is the leading cause of glaucoma. With technique limitations, how TM moves is still an enigma. This study describes a new laboratory platform to investigate TM motion responses to ocular transients in ex vivo eyes. The anterior segments of human cadaver and primate eyes were mounted in a perfusion system fitting. Perfusion needles were placed to establish mean baseline pressure. A perfusion pump was connected to the posterior chamber and generated an immediate transient pressure elevation. A phase-sensitive optical coherent tomography system imaged and quantified the TM motion. The peak-to-peak TM displacements (ppTMD) were determined, a tissue relaxation curve derived, and a time constant obtained. This study showed that the ppTMD increased with a rise in the pulse amplitude. The ppTMD was highest for the lowest mean pressure of 16 mmHg and decreased with mean pressure increase. The pulse frequency did not significantly change ppTMD. With a fixed pulse amplitude, an increase in mean pressure significantly reduced the time constant of recoil from maximum distension. Our research platform permitted quantitation of TM motion responses to designed pulse transients. Our findings may improve the interpretation of new TM motion measurements in clinic, aiding in understanding mechanisms and management.

Motion Responses of a Berthed Tank under Resonance Coupling Effect of Internal Sloshing and Gap Flow

The growth of global energy transportation has promoted the rapid increase of large-scale LNG (liquefied natural gas) carriers, and concerns around the safety of LNG ships has attracted significant attention. Such a floating structure is affected by the external wave excitation and internal liquid sloshing. The interaction between the structure’s motion and the internal sloshing under wave actions may lead to the ship experiencing an unexpected accident. In this research, a hydrodynamic experiment is conducted to investigate the motion responses of a floating tank mooring, both close to and away from a dock. The resonance coupling effect of the internal sloshing and gap flow on the tank’s motion is considered. Based on the measured motion trajectory of the floating tank, the stability and safety of the floating tank are estimated. The results show that the sloshing resonance and narrow gap resonance are beneficial to the stability of the ship. This is helpful for controlling the motion of a berthed ship under wave action with a reasonable selection of the gap distance and the liquid level.

SUPERIOR SEAWORTHINESS OF A RESONANCE-FREE FAST OCEANGOING SWATH

The speed reduction, additional resistance or slamming caused by the large amplitude ship motions, should be completely restricted for a large fast oceangoing ship because of the strict time-punctuality and the high value of the cargo. A “Resonance-Free SWATH (RFS)”, which has negative restoring moments due to the extremely small water plane area, is introduced to minimize the motion responses. A motion control system using small fins is necessary for the RFS, which has no stability during high speed cruising. Theoretical estimations and experiments to search for the optimum values of PD control gains have been performed. Unsteady characteristics of fin-generated lift such as the time lag and the interaction among the fins and lower hulls have been measured and they are taken into account in the motion equations. Then, experiments using the RFS model with controlling fins have been carried out to validate the theoretical estimation for the motion responses of the RFS in waves. The theoretical and experimental results agree well with each other. The motion responses of the RFS in regular and irregular head waves are compared with those of other hull forms, such as a mono-hull, an ordinary SWATH and a trimaran. The clear advantage of the RFS regarding the seaworthiness has been found. In summary, the heave motion response of the RFS is reduced to 1/60 and the pitch motion becomes1/8, compared with those of the existing mono-hull ship.

IDENTIFICATION OF INFLUENTIAL PARAMETERS IN A SHIP’S MOTION RESPONSES: A ROUTE TO MONITORING DYNAMIC STABILITY

Six degrees of freedom motion response tests of a Ro-Ro model have been carried out in irregular waves under intact conditions. A stationary model was tested in different sea states for following, astern quartering and beam seas. The investigation was limited to the effect of encountered frequency components and associated magnitude of energy of the ship’s motion responses. Analysis of heave, pitch and roll motions confirmed the vulnerability of the model to certain frequency ranges resulting in an adverse effect on the responses, and these were closely related to its natural frequencies. It was confirmed that the roll motion maintains its highest oscillation around the natural frequency in all sea conditions regardless of heading angles. However spectral analysis of the heave and pitch responses revealed the wave peak frequency. Roll is magnified when the peak frequency of wave approaches the natural roll frequency; therefore keeping them apart avoids a large motion response. It was concluded that peak frequency and associated magnitude are two important inherent characteristics of motion responses. Detection of influential parameters of encountered wave through heave and pitch responses could be utilised to limit a large ship’s motion at sea.

Integration of visual motion and pursuit signals in areas V3A and V6+ across cortical depth using 9.4T fMRI

Neural mechanisms underlying a stable perception of the world during pursuit eye movements are not fully understood. Both, perceptual stability as well as perception of real (i.e. objective) motion are the product of integration between motion signals on the retina and efference copies of eye movements. Human areas V3A and V6 have previously been shown to have strong objective ('real') motion responses. Here we used high-resolution laminar fMRI at ultra-high magnetic field (9.4T) in human subjects to examine motion integration across cortical depths in these areas. We found an increased preference for objective motion in areas V3A and V6+ i.e. V6 and possibly V6A towards the upper layers. When laminar responses were detrended to remove the upper-layer bias present in all responses, we found a unique, condition-specific laminar profile in V6+, showing reduced mid-layer responses for retinal motion only. The results provide evidence for differential, motion-type dependent laminar processing in area V6+. Mechanistically, the mid-layer dip suggests a special contribution of retinal motion to integration, either in the form of a subtractive (inhibitory) mid-layer input, or in the form of feedback into extragranular or infragranular layers. The results show that differential laminar signals can be measured in high-level motion areas in human occipitoparietal cortex, opening the prospect of new mechanistic insights using non-invasive brain imaging.

Hydrodynamic Performance of a Multi-Module Three-Cylinder Floating Breakwater System under the Influence of Reefs: A 3D Experimental Study

As the technical and theoretical research of floating breakwaters is becoming increasingly mature, the floating breakwaters are now being utilized, especially in offshore reefs. Therefore, it is of practical significance to study the hydrodynamic performance of a multi-module floating breakwater system under the influence of reefs. In this study, a 3D model experiment was carried out on a system consisting of eight three-cylinder floating breakwater modules under the influence of reefs. A wave attenuation mesh cage was incorporated at the bottom of the model. The floating breakwater system was slack-moored in its equilibrium position, and each module was connected by elastic connectors. The reefs were modeled on a bathymetric map of existing reefs in the East China Sea. In this experiment, the wave transmission coefficients, motion responses, and mooring forces of the floating breakwater system were measured. The results showed that the three-cylinder floating breakwater in the beam waves (β = 90°) has excellent wave attenuating performance under the influence of reefs, especially for short-period waves. However, under the influence of the reef reflection wave and the shallow water effect, the motion responses in the three main stress directions of the floating breakwater were large, and there was some surge and pitch motion. Under the influence of the aggregation and superposition of reflected waves on both sides of the reefs, the peak mooring forces in the middle position of the floating breakwater system were the largest at large wave height. The three-cylinder floating breakwater exhibited satisfactory hydrodynamic performance under the influence of reefs. It has broad application prospects in offshore reefs.

Synergy of color and motion vision for detecting approaching objects in Drosophila

Color and motion are used by many species to identify salient moving objects. They are processed largely independently, but color contributes to motion processing in humans, for example, enabling moving colored objects to be detected when their luminance matches the background. Here, we demonstrate an unexpected, additional contribution of color to motion vision in Drosophila. We show that behavioral ON-motion responses are more sensitive to UV than for OFF-motion, and we identify cellular pathways connecting UV-sensitive R7 photoreceptors to ON and OFF-motion-sensitive T4 and T5 cells, using neurogenetics and calcium imaging. Remarkably, the synergy of color and motion vision enhances the detection of approaching UV discs, but not green discs with the same chromatic contrast, and we show how this generalizes for visual systems with ON and OFF pathways. Our results provide a computational and circuit basis for how color enhances motion vision to favor the detection of saliently colored objects.