Wavefront-modified vector beams for THz cornea spectroscopy.

Terahertz spectroscopy is a promising method to diagnose ocular diseases, where the cornea is typically imaged by Gaussian beams. However, the beam's mismatch with the cornea's spherical surface produces a 5-10 % error in analysis. We investigate cornea spectroscopy with wavefront-modified vector beams, reducing the original analysis error to less than 0.5 %. Vector beams are synthesized by our developed 3D Angular Spectrum Method expanded to vector spherical harmonic presentation, allowing wavefront modification and scattering analysis from 100-layer cornea models. We show that wavefront-modified spherical vector beams possess increased accuracy and non-sensitive focusing on cornea spectroscopy compared to the Gaussian beams. Additionally, we investigate wavefront-modified cylindrical vector beams, which show frequency-dependent scattering power arising from s- and p-polarizations. As a result, these beams are unsuitable for cornea spectroscopy, although they have potential for optical force applications. Wavefront-modified vector beams can be applied to spherical target spectroscopy and optical force applications, such as medicine, medical imaging, and optical tweezers.

Mie scattering with 3D angular spectrum method.

Mie theory is a powerful method to model electromagnetic scattering from a multilayered sphere. Usually, the incident beam is expanded to its vector spherical harmonic representation defined by beam shape coefficients, and the multilayer sphere scattering is obtained by the T-matrix method. However, obtaining the beam shape coefficients for arbitrarily shaped incident beams has limitations on source locations and requires different methods when the incident beam is defined inside or outside the computational domain or at the scatterer surface. We propose a 3D angular spectrum method for defining beam shape coefficients from arbitrary source field distributions. This method enables the placement of the sources freely within the computational domain without singularities, allowing flexibility in beam design. We demonstrate incident field synthesis and spherical scattering by comparing morphology-dependent resonances to known values, achieving excellent matching and high accuracy. The proposed method has significant benefits for optical systems and inverse beam design. It allows for the analysis of electromagnetic forward/backward propagation between optical elements and spherical targets using a single method. It is also valuable for optical force beam design and analysis.

Curved boundary integral method for electromagnetic fields.

The angular spectrum method is a rigorous method to synthesize near and far-field electromagnetic beams from planar field distributions. However, this limitation of planar surfaces has restricted its applicability to beams with simple focal planes. We propose a curved boundary integral method (CBIM) to synthesize electromagnetic beams from arbitrary surfaces to address this limitation and expand the method's scope to synthesize beams from and between shaped objects. This study presents a detailed theoretical framework behind the CBIM and validates its effectiveness and accuracy with a comprehensive set of simulations. Additionally, we present mathematical proof to support our proposal. The proposed method satisfies Maxwell's equations and significantly benefits optical systems and inverse beam design. It allows for analyzing electromagnetic forward/backward propagation between optical elements using a single method. It is also valuable for optical force beam design and analysis.

On the qualitative study of a two-trophic plant-herbivore model.

The coexistence of plant-herbivore populations in an ecological system is a fundamental topic of research in mathematical ecology. Plant-herbivore interactions are often described by using discrete-time models in the case of non-overlapping generations: such generations have some specific time interval of life and their old generations are replaced by new generations after some regular interval of time. Keeping in mind the dynamical reliability of continuous-time models we presented two discrete-time plant-herbivore models. Mainly, by applying Euler's forward method a discrete-time plant-herbivore model is obtained from a continuous-time plant-herbivore model. In addition, a dynamically consistent discrete-time plant-herbivore model is obtained by applying a nonstandard difference scheme. Moreover, local stability is discussed and the existence of bifurcation about positive equilibrium is shown under some mathematical conditions. To control bifurcation and chaos, a modified hybrid technique is developed. Finally, to support our theocratical results and to show the dynamical reliability of the nonstandard difference scheme some numerical examples are provided.

Vector spherical harmonic analysis and experimental validation of spherical shells illuminated with broadband, millimeter wave Gaussian beams: applications to corneal sensing.

Coupling to longitudinal modes of thin spherical shells, under Gaussian-beam illumination, was explored with a theoretical method based on Fourier-optics analysis and vector spherical harmonics and was scrutinized with an experimental setup. For the theory part, the illumination frequency band was fixed between 100-600 GHz and the outer spherical shell radius of curvature and thickness are 7.5 mm and 0.5 mm, respectively. The shell material was either the lossless cornea or an aqueous effective media representing the cornea. Six different beam-target strategies were introduced being potential candidates for maximum coupling. Two dispersion-tuned beam ensembles with strongly frequency-dependent phase center location have been created with a fixed incident beam 1/e radius and radius of curvature called forward strategies. These computations of different alignments were continued with four beam ensembles of frequency-invariant phase center, constructed from fits to experimental data, oriented at four different axial locations with respect to the spherical shell center of curvature, they are called reverse strategies. Coupling efficiency for all strategies was calculated for different targets including perfect electrical conductor (PEC) sphere, PEC core covered by a cornea loss-free layer and cornea. All scattering strategies contrasted to scattering from equivalent planar targets as a reference with maximum coupling. The results show that, under an ideal calibration, forward strategies are a closer approximation to the plane-wave condition for the cornea. An experimental setup was assembled to explore the simulation approach in a frequency range between 220 GHz to 330 GHz. Two different quartz samples with permittivity of 4.1 were mounted on a water core, acting for a cornea. The first and second quartz radius and thickness were 7.5 mm and 0.5 mm and 8 mm and 1 mm, respectively. An adequate agreement between theory and experiment was confirmed. A particle optimisation swarm algorithm was applied to extract the thickness and permittivity of quartz from the measured back-scattered field for reverse strategies.

Calibration Alignment Sensitivity in Corneal Terahertz Imaging.

Improving the longitudinal modes coupling in layered spherical structure contributes significantly to corneal terahertz sensing, which plays a crucial role in the early diagnosis of cornea dystrophies. Using a steel sphere to calibrate reflection from the cornea sample assists in enhancing the resolution of longitudinal modes. The requirement and challenges toward applying the calibration sphere are introduced and addressed. Six corneas with different properties are spotted to study the effect of perturbations in the calibration sphere in a frequency range from 100 GHz to 600 GHz. A particle-swarm optimization algorithm is employed to quantify corneal characteristics considering cases of accurately calibrated and perturbed calibrated scenarios. For the first case, the study is carried out with signal-to-noise values of 40 dB, 50 dB and 60 dB at waveguide bands WR-5.1, WR-3.4, and WR-2.2. As expected, better estimation is achieved in high-SNR cases. Furthermore, the lower waveguide band is revealed as the most proper band for the assessment of corneal features. For perturbed cases, the analysis is continued for the noise level of 60 dB in the three waveguide bands. Consequently, the error in the estimation of corneal properties rises significantly (around 30%).

Effect of non nutritive sucking on the behavioral state and physiological change in premature infants before feeding.

Premature infants display few behaviors that provide quantitative information about their maturational development, making it difficult to carry out appropriate care. This study was performed to investigate the effect of non-nutritive sucking on behavioral state and physiological changes in premature infants. They were selected from premature unit of Main University Hospital at Tanta city. Forty premature infants were divided into two groups, nonnutritive sucking and no non-nutritive sucking. Personal characteristics were obtained from medical records. Anderson Behavioral State Scoring Systems were used and observed four times daily. Physiological changes were noticed; temperature, heart and respiratory rates The present study revealed that the time spent in sleep states was decreased and time spent in awake states was increased, when compared to no non-nutritive sucking group (ONNS). There was Statistically significant differences within the two groups related to behavior states and physiological changes. The development of sucking reflex was accelerated among premature in the non-nutritive sucking group. They shift earlier to oral feeding and their discharge was earlier.

Inhibition of steroid sex hormones release in rats by two Ca2+ channel blockers.

The calcium channel blockers Diltiazem HCl (2 mg kg-1 day-1, IP) or Cinnarizine (8 mg kg-1 day-1, IP) were given for a period of 30 days to adult male and female albino rats. The effect of each calcium channel blocker on circulating blood levels of steroid sex hormones was investigated by radioimmunoassay in comparison with the normal control level. The data demonstrated that both Diltiazem and Cinnarizine significantly decreased serum normal testosterone levels in males (36% and 52% inhibition respectively) as well as both normal estradiol and progesterone contents in females (58% and 45% inhibition with Diltiazem and 68% and 52% inhibition with Cinnarizine respectively). This study indicates the importance of blood sex hormones-follow up in case of long term Ca2+ channel blockers medication.

The effect of thiola, piroxicam and diltiazem on the uterine contractility of gamma-irradiated rats.

Accidental radiation exposure raises concern for functional modifications in the uterine physiology. In the current work, total body gamma-irradiation (0.7, 1.4 and 2.1 Gy) of non-pregnant adult female albino rats increased significantly the frequency and amplitude of uterine contractions in vivo. Administration of Thiola (a sulfhydryl containing agent) in doses of 100 or 250 mg kg-1, pre-irradiation or Piroxicam (a potent prostaglandin inhibitor) in a dose of 2 mg kg-1, pre- or post-irradiation failed to normalize the changes induced by gamma-irradiation. However, administration of Diltiazem (a Ca2+ channel blocker, 8 mg kg-1) pre- or post-irradiation caused a significant decrease in the frequency of uterine contractions (21% and 24% respectively) in comparison to the uterotonic pattern of gamma-irradiation alone. The results indicate a promising tocolytic activity of Diltiazem against the uterotonic effect of gamma-radiation.