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Each tubulin protein molecule on the cylindrical surface of a microtubule, a fundamental element of the cytoskeleton, acts as a unit cell of a crystal sensor. Electromagnetic sensing enables the 2D surface of microtubule to act as a crystal or a collective electromagnetic signal processing system. We propose a model in which each tubulin dimer acts as the period of a one-dimensional crystal with effective electrical impedance related to its molecular structure. Based on the mathematical crystal theory with one-dimensional translational symmetry, we simulated the electrical transport properties of the signal across the microtubule length and compared it to our single microtubule experimental results. The agreement between theory and experiment suggests that one of the most essential components of any Eukaryotic cell acts as a one-dimensional crystal.

The gaze movement from a driver represents specific skills related to safe driving. Driving maneuvering evaluation is to know driving fitness. We found that gaze movement entropy is highly sensitive to visual behavior demands while driving a vehicle and the workload level. Entropy measures were more sensitive, more robust, and easier to calculate than gaze established measures. The gaze movement measures were collected using a driving simulator, using five different simulate routes and tree different workload scenarios; one route of familiarization was used to create a baseline. Because the workload became more difficult, drivers looked more at the central part of the road for more extended periods, the gaze movement entropy values decreased when the workload was increased, and the results show differences between two levels of workload. Also, the entropy result is compared against the classical analysis of the spatial distribution of gaze.

Motion analysis is widely used to monitor the dynamics of the gaze movement signal. The performance analysis in the spectral domain shows a variation of the characteristics due to the development of changes in dynamic behavior. Each dynamic reaps characteristics in its spectral domain. After examining the spectrum of gaze movement, one can provide valuable information about defects that develop with visible artifacts. The evaluation of the gaze movement is based on the presence of characteristic frequencies and its harmonics in the acquired movement signal. In this work, a signal processing analysis of the movement of the gaze in the domain of time and frequency was performed. The empirical mode decomposition has been proposed to plot the five first intrinsic mode functions in the polar form to detect the alteration of the gaze movement dynamics. The results show that the evaluation of the performance of the gaze movement dynamics can be done by observing the polar representation only.

All eye movement measurement contains some level of noise; denoising requires the use of digital filters and subsequent measurement processing. The elimination of noise in the eye movement signals commonly uses some linear time-invariant filter, such as the Butterworth, Gauss, or Savitzky-Golay filters. However, in high noise signals, the low-pass part of the filters can significantly distort and alter speeds saccades. This can be remedied by adding a high pass component, but this introduces its artifacts, especially false oscillations. Some of the problems can be improved using the mean filter, the Kalman filter, or the Bilateral filter. Although they are efficient, they still share the main feature: the resulting signal contains the remaining noise. Our proposed method is using the Wiener filter to denoise signal, and we will consider the estimation of the noise power spectrum calculated using an artificial eye. The results indicate that the method eliminates noise efficiently.

Biological movement analysis describes specific characteristics of the person’s health status, which motivates the analysis of the dynamic aspects related to the rhythms and movements of our body. Natural, free movements can be periodic or irregular in time and space, and each type of dynamic behavior can be related to efficient or altered movements. This research describes an overview of nonlinear dynamics and concepts of chaos applied to bio-motion paths as a way to describe and analyze a bio-movement, for example, the eye movement presents different rhythms depending on the demand for exploration or the state of health of the person. For this research, 20 subjects with normal vision were involved. Their eye movements and head movements were registered using an eye tracker and head-mounted tracker, measuring the position and rotation of the eye and head. The results demonstrate that nonlinear analysis can be applied to evaluate alteration in the biological system showing more sensitivity than traditional spectral analysis. This type of evaluation can provide a tool to find the relationship between movement dynamics and physiological phenomena, which might be useful to describe any alteration in the biological system.

Porous Si-SiO2 UV microcavities are used to modulate a broad responsivity photodetector (GVGR-T10GD) with a detection range from 300 to 510 nm. The UV microcavity filters modified the responsivity at short wavelengths, while in the visible range the filters only attenuated the responsivity. All microcavities had a localized mode close to 360 nm in the UV-A range, and this meant that porous Si-SiO2 filters cut off the photodetection range of the photodetector from 300 to 350 nm, where microcavities showed low transmission. In the short-wavelength range, the photons were absorbed and did not contribute to the photocurrent. Therefore, the density of recombination centers was very high, and the photodetector sensitivity with a filter was lower than the photodetector without a filter. The maximum transmission measured at the localized mode (between 356 and 364 nm) was dominant in the UV-A range and enabled the flow of high energy photons. Moreover, the filters favored light transmission with a wavelength from 390 nm to 510 nm, where photons contributed to the photocurrent. Our filters made the photodetector more selective inside the specific UV range of wavelengths. This was a novel result to the best of our knowledge.

Porous Si-SiO2 UV microcavities are used to modulate a broad responsivity photodetector (GVGR-T10GD) with a detection range from 300 to 510 nm. The UV microcavity filters modified the responsivity at short wavelengths, while in the visible range the filters only attenuated the responsivity. All microcavities had a localized mode close to 360 nm in the UV-A range, and this meant that porous Si-SiO2 filters cut off the photodetection range of the photodetector from 300 to 350 nm, where microcavities showed low transmission. In the short-wavelength range, the photons were absorbed and did not contribute to the photocurrent. Therefore, the density of recombination centers was very high, and the photodetector sensitivity with a filter was lower than the photodetector without a filter. The maximum transmission measured at the localized mode (between 356 and 364 nm) was dominant in the UV-A range and enabled the flow of high energy photons. Moreover, the filters favored light transmission with a wavelength from 390 nm to 510 nm, where photons contributed to the photocurrent. Our filters made the photodetector more selective inside the specific UV range of wavelengths. This was a novel result to the best of our knowledge.

We induced forced and auto-oscillations in one-dimensional photonic crystals (1-D- PCs) with localized defects when light impinges transversally to the defect layer. The photonic structure used consists of a microcavity-like structure formed of two 1-D-PCs made of free- standing porous silicon, separated by a variable air gap (the defect) and the working wavelength is 633 nm. The force generation was made evident by driving a laser light by means of a chopper; the light hit the photonic structure and induced a vibration and the vibration was characterized by using a very sensitive vibrometer. For example, we measured peak displacements and velocities ranging from 2 to 167 μm and 0.4 to 2.1 mm∕s with a power light level from 2.6 to 13 mW. In comparison, recent evidence showed that giant resonant light forces could induce average veloc- ity values of 0.45 mm∕s in microspheres embedded in water with a 43-mW light power. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI. (DOI: 10.1117/1.JNP.8.083071)

Control over the 1.5 µm emission from erbium is desirable for communication and computational technologies because the erbium emission falls in the window of maximum transmission for silica based fiber optics. Tunable, narrow, directional, and enhanced erbium emission from silicon based 1-D photonic bandgap structures will be demonstrated. The structures are prepared by anodic etching of crystalline silicon and consist of two highly reflecting Bragg reflectors sandwiching an active layer. The cavities are doped by electro-migrating the erbium ions into the porous silicon matrix, followed by high temperature oxidation. By controlling the oxidation temperature, porosity, and thickness of the structure, the position of the erbium emission is tuned to emit in regions where the normal erbium emission is very weak. The erbium emission from the cavity is narrowed to a full width at half maximum (FWHM) of 12 nm with a cavity quality factor Q of 130, highly directional with a 20 degree emission cone around the normal axis, and enhanced by more than one order of magnitude when compared to its lateral emission. Erbium photoluminescence (PL) from porous silicon 2-D photonic bandgap structures is also demonstrated.

The tuning of one-dimensional photonic band gap structures based on porous silicon will be presented. The photonic structures are prepared by applying a periodic pulse of current density to form alternating high and low porosity layers. The width and position of the photonic bandgap are determined by the dielectric function of each layer, which depends on porosity, and their thickness. In this work we show that by controlling the oxidation of the porous silicon structures, it is possible to tune the photonic bandgap towards shorter wavelengths. The formation of silicon dioxide during oxidation causes a reduction of the refractive index, which induces the blue shift. The photonic band gap is determined experimentally by taking the total reflection of the structures. In order to understand the tuning of the photonic band gap, we developed a geometrical model using the effective medium approximation to calculate the dielectric function of each of the oxidized porous silicon layers. The two key parameters are the porosity and the parameter β, defined as the ratio between the silicon dioxide thickness and the pore radius before oxidation. Choosing the parameter β, to fit the experimental photonic band gap of the oxidized structures, we extract the fraction of oxide that is present. For example, the measured 240 nm blue shift of a photonic bandgap that was centered at 1.7 microns corresponds to the transformation of 30% of the structure into silicon dioxide. A similar approach can be used for oxidized two-dimensional porous silicon photonic structures.