Cone signals and activity in myopia and emmetropia

Myopia (short-sightedness) is a common ocular disorder of children and young adults. Studies primarily using animal models have shown that the retina controls eye growth and the outer retina is likely to have a key role. One theory is that the proportion of L (long-wavelength-sensitive) and M (medium-wavelength-sensitive) cones is related to myopia development; with a high L/M cone ratio predisposing individuals to myopia. However, not all dichromats (persons with red-green colour vision deficiency) with extreme L/M cone ratios have high refractive errors. We predict that the L/M cone ratio will vary in individuals with normal trichromatic colour vision but not show a systematic difference simply due to refractive error. The aim of this study was to determine if L/M cone ratios in the central 30° are different between myopic and emmetropic young, colour normal adults. Information about L/M cone ratios was determined using the multifocal visual evoked potential (mfVEP). The mfVEP can be used to measure the response of visual cortex to different visual stimuli. The visual stimuli were generated and measurements performed using the Visual Evoked Response Imaging System (VERIS 5.1). The mfVEP was measured when the L and M cone systems were separately stimulated using the method of silent substitution. The method of silent substitution alters the output of three primary lights, each with physically different spectral distributions to control the excitation of one or more photoreceptor classes without changing the excitation of the unmodulated photoreceptor classes. The stimulus was a dartboard array subtending 30° horizontally and 30° vertically on a calibrated LCD screen. The m-sequence of the stimulus was 215-1. The N1-P1 amplitude ratio of the mfVEP was used to estimate the L/M cone ratio. Data were collected for 30 young adults (22 to 33 years of age), consisting of 10 emmetropes (+0.3±0.4 D) and 20 myopes (–3.4±1.7 D). The stimulus and analysis techniques were confirmed using responses of two dichromats. For the entire participant group, the estimated central L/M cone ratios ranged from 0.56 to 1.80 in the central 3°-13° diameter ring and from 0.94 to 1.91 in the more peripheral 13°-30° diameter ring. Within 3°-13°, the mean L/M cone ratio of the emmetropic group was 1.20±0.33 and the mean was similar, 1.20±0.26, for the myopic group. For the 13°-30° ring, the mean L/M cone ratio of the emmetropic group was 1.48±0.27 and it was slightly lower in the myopic group, 1.30±0.27. Independent-samples t-test indicated no significant difference between the L/M cone ratios of the emmetropic and myopic group for either the central 3°-13° ring (p=0.986) or the more peripheral 13°-30° ring (p=0.108). The similar distributions of estimated L/M cone ratios in the sample of emmetropes and myopes indicates that there is likely to be no association between the L/M cone ratio and refractive error in humans.

Utilizing Wide-Area Signals for off-center SVCs to damp interarea oscillations

Wide-Area Measurement Systems (WAMS) provide the opportunity of utilizing remote signals from different locations for the enhancement of power system stability. This paper focuses on the implementation of remote measurements as supplementary signals for off-center Static Var Compensators (SVCs) to damp inter-area oscillations. Combination of participation factor and residue method is used for the selection of most effective stabilizing signal. Speed difference of two generators from separate areas is identified as the best stabilizing signal and used as a supplementary signal for lead-lag controller of SVCs. Time delays of remote measurements and control signals is considered. Wide-Area Damping Controller (WADC) is deployed in Matlab Simulink framework and is tested under different operating conditions. Simulation results reveal that the proposed WADC improve the dynamic characteristic of the system significantly.

Testing second order cyclostationarity in the squared envelope spectrum of non-white vibration signals

Cyclostationary models for the diagnostic signals measured on faulty rotating machineries have proved to be successful in many laboratory tests and industrial applications. The squared envelope spectrum has been pointed out as the most efficient indicator for the assessment of second order cyclostationary symptoms of damages, which are typical, for instance, of rolling element bearing faults. In an attempt to foster the spread of rotating machinery diagnostics, the current trend in the field is to reach higher levels of automation of the condition monitoring systems. For this purpose, statistical tests for the presence of cyclostationarity have been proposed during the last years. The statistical thresholds proposed in the past for the identification of cyclostationary components have been obtained under the hypothesis of having a white noise signal when the component is healthy. This need, coupled with the non-white nature of the real signals implies the necessity of pre-whitening or filtering the signal in optimal narrow-bands, increasing the complexity of the algorithm and the risk of losing diagnostic information or introducing biases on the result. In this paper, the authors introduce an original analytical derivation of the statistical tests for cyclostationarity in the squared envelope spectrum, dropping the hypothesis of white noise from the beginning. The effect of first order and second order cyclostationary components on the distribution of the squared envelope spectrum will be quantified and the effectiveness of the newly proposed threshold verified, providing a sound theoretical basis and a practical starting point for efficient automated diagnostics of machine components such as rolling element bearings. The analytical results will be verified by means of numerical simulations and by using experimental vibration data of rolling element bearings.

Development of a new signal processing diagnostic tool for vibration signals acquired in transient conditions

The diagnostics of mechanical components operating in transient conditions is still an open issue, in both research and industrial field. Indeed, the signal processing techniques developed to analyse stationary data are not applicable or are affected by a loss of effectiveness when applied to signal acquired in transient conditions. In this paper, a suitable and original signal processing tool (named EEMED), which can be used for mechanical component diagnostics in whatever operating condition and noise level, is developed exploiting some data-adaptive techniques such as Empirical Mode Decomposition (EMD), Minimum Entropy Deconvolution (MED) and the analytical approach of the Hilbert transform. The proposed tool is able to supply diagnostic information on the basis of experimental vibrations measured in transient conditions. The tool has been originally developed in order to detect localized faults on bearings installed in high speed train traction equipments and it is more effective to detect a fault in non-stationary conditions than signal processing tools based on spectral kurtosis or envelope analysis, which represent until now the landmark for bearings diagnostics.

Estimation of vibration amplitude in Fourier domain optical coherence tomography interferometric signals from Doppler spectrum

In presented method combination of Fourier and Time domain detection enables to broaden the effective bandwidth for time dependent Doppler Signal that allows for using higher-order Bessel functions to calculate unambiguously the vibration amplitudes.

Homologs of FT, CEN and FD respond to developmental and environmental signals affecting growth and flowering in the perennial vine kiwifruit

FLOWERING LOCUS T (FT) and CENTRORADIALIS (CEN) homologs have been implicated in regulation of growth, determinacy and flowering. The roles of kiwifruit FT and CEN were explored using a combination of expression analysis, protein interactions, response to temperature in high-chill and low-chill kiwifruit cultivars and ectopic expression in Arabidopsis and Actinidia. The expression and activity of FT was opposite from that of CEN and incorporated an interaction with a FLOWERING LOCUS D (FD)-like bZIP transcription factor. Accumulation of FT transcript was associated with plant maturity and particular stages of leaf, flower and fruit development, but could be detected irrespective of the flowering process and failed to induce precocious flowering in transgenic kiwifruit. Instead, transgenic plants demonstrated reduced growth and survival rate. Accumulation of FT transcript was detected in dormant buds and stem in response to winter chilling. In contrast, FD in buds was reduced by exposure to cold. CEN transcript accumulated in developing latent buds, but declined before the onset of dormancy and delayed flowering when ectopically expressed in kiwifruit. Our results suggest roles for FT, CEN and FD in integration of developmental and environmental cues that affect dormancy, budbreak and flowering in kiwifruit.

Dependence of second-harmonic signals generated in malignant human prostate tissue on excitation wavelength

The dependence of second harmonic generation (SHG) from hyperplastic parenchyma and stroma in maligant human prostate tissue on excitation wavelengths was measured. A femtosecond pulsed laser, a scanning microscope and a spectrograph were used to perform the measurements. The spectra were measured under excitation power of 10 mW at excitation wavelengths of 730 nm, 750 nm, 800 nm, 850 nm and 890 nm. Analysis suggested that the SHG in prostate tissue is highly structured and wavelength dependent signifying its ability to be used as an indicator for recognizing tissue components, ultrastructures, micro-environments and diseases.

Rescuers ignored danger to pluck mother and child from torrent

"Jenny Perry, her husband James and nine-year-old son Ted balanced on the roof of their car until the floodwaters at Helidon took them towards a power line."

Teleoperation of a 7 DOF humanoid robot arm using human arm accelerations and EMG signals

We present our work on tele-operating a complex humanoid robot with the help of bio-signals collected from the operator. The frameworks (for robot vision, collision avoidance and machine learning), developed in our lab, allow for a safe interaction with the environment, when combined. This even works with noisy control signals, such as, the operator’s hand acceleration and their electromyography (EMG) signals. These bio-signals are used to execute equivalent actions (such as, reaching and grasping of objects) on the 7 DOF arm.

Monitoring changes of the tibialis anterior during dorsiflexion with electromyography, sonomyography, dynamometry and kinematic signals

Dorsiflexion (DF) of the foot plays an essential role in both controlling balance and human gait. Electromyography and Sonomyography can provide information on several aspects of muscle function. The aim was to describe a new method for real-time monitoring of muscular activity, as measured using EMG, muscular architecture, as measured using SMG, force, as measured using dynamometry, and kinematic parameters, as measured using IS during isometric and isotonic contractions of the foot DF. The present methodology may be clinically relevant because it involves a reproducible procedure which allows the function and structure of the foot DF to be monitored.

A method for estimating intrinsic noise in electroretinographic (ERG) signals

Purpose To develop a signal processing paradigm for extracting ERG responses to temporal sinusoidal modulation with contrasts ranging from below perceptual threshold to suprathreshold contrasts. To estimate the magnitude of intrinsic noise in ERG signals at different stimulus contrasts. Methods Photopic test stimuli were generated using a 4-primary Maxwellian view optical system. The 4-primary lights were sinusoidally temporally modulated in-phase (36 Hz; 2.5 - 50% Michelson). The stimuli were presented in 1 s epochs separated by a 1 ms blank interval and repeated 160 times (160.16 s duration) during the recording of the continuous flicker ERG from the right eye using DTL fiber electrodes. After artefact rejection, the ERG signal was extracted using Fourier methods in each of the 1 s epochs where a stimulus was presented. The signal processing allows for computation of the intrinsic noise distribution in addition to the signal to noise (SNR) ratio. Results We provide the initial report that the ERG intrinsic noise distribution is independent of stimulus contrast whereas SNR decreases linearly with decreasing contrast until the noise limit at ~2.5%. The 1ms blank intervals between epochs de-correlated the ERG signal at the line frequency (50 Hz) and thus increased the SNR of the averaged response. We confirm that response amplitude increases linearly with stimulus contrast. The phase response shows a shallow positive relationship with stimulus contrast. Conclusions This new technique will enable recording of intrinsic noise in ERG signals above and below perceptual visual threshold and is suitable for measurement of continuous rod and cone ERGs across a range of temporal frequencies, and post-receptoral processing in the primary retinogeniculate pathways at low stimulus contrasts. The intrinsic noise distribution may have application as a biomarker for detecting changes in disease progression or treatment efficacy.