A Study on Angular Distribution of THz Radiation Driven by Two-Color Laser-induced Microplasma

We present an analytical method to study the angular distribution of THz radiation driven by two-color laser-induced microplasma in nitrogen gas. Directionally dependent temporal waveforms of the radiated THz pulse is calculated. To do so, we have extended the photo-current model to calculate three-dimensional distribution of the photo-induced current from which the far field THz radiation is computed. We have also studied the effect of optical polarization state and phase difference on the angular distribution of radiation. Our study shows that for two orthogonally-polarized colors, not only THz polarization state, but also the angular distribution of THz radiation is mostly influenced by the second optical harmonic. The possibility of rotating the angular radiation pattern around the axis of the laser propagation is illustrated for circularly-polarized laser drivers by changing the optical phase difference

Theory, Design and Development of Resonance Based Biosensors in Terahertz and Millimeter-wave

Recent advances in molecular biology and nanotechnology have enabled scientists to study biological systems at molecular and atomic scales. This level of sophistication demands for new technologies to emerge for providing the necessary sensing tools and equipment. Recent studies have shown that terahertz technology can provide revolutionary sensing techniques for organic and non-organic materials with unprecedented accuracy and sensitivity. This is due to the fact that most of the macromolecules have vibrational and/or rotational resonance signatures in terahertz range. To further increase the sensitivity, terahertz radiation is generated and interacted with the bio-sample on a miniaturized test site or the so-called biochip. From the view point of generation and manipulation of terahertz radiation, the biochip is designed based on the same rules as in high frequency electronic chips or integrated circuits (IC). By increasing the frequency toward terahertz range, the conventional IC design methodologies and analysis tools fail to perform accurately. Therefore, development of new design methodologies and analysis tools is of paramount importance for future terahertz integrated circuits (TIC) in general and terahertz biochips in particular. In this thesis, several advancements are made in design methodology, analysis tool and architecture of terahertz and millimeter-wave integrated circuits when used as a biochip. A global and geometry independent approach for design and analysis of the travelling-wave terahertz photomixer sources, as the core component in a TIC, is discussed in details. Three solvers based on photonic, semiconductor and electromagnetic theories are developed and combined as a unified analysis tool. Using the developed terahertz photomixer source, a resonance-based biochip structure is proposed, and its operation principle, based on resonance perturbation method, is explained. A planar metallic resonator acting as a sample holder and transducer is designed, and its performance in terms of sensitivity and selectivity is studied through simulations. The concept of surface impedance for electromagnetic modeling of DNA self-assembled monolayer on a metal surface is proposed, and its effectiveness is discussed based on the available data in the literature. To overcome the loss challenge, Whispering Gallery Mode (WGM) dielectric resonators with high Q factor are studied as an alternative for metallic resonator. The metallic loss becomes very high at terahertz frequencies, and as a result of that planar metallic resonators do not exhibit high Q factor. Reduced Q factor results in a low sensitivity for any sensor using such resonators. Theoretical models for axially and radially layered dielectric resonators acting on WGM are presented, and the analytical results are compared with the measured data. Excitation of WGM through dielectric waveguide is proposed, and the critical coupling condition is explained through analytical formulation. The possibility of selecting one resonance among many for sensing application is also studied both theoretically and experimentally. A high sensitivity sensor based on WGM resonance in mm-wave and terahertz is proposed, and its sensitivity is studied in details. The performance of the proposed sensor is tested for sensing drug tablets and also liquid droplets through various measurements in mm-wave range. The comprehensive sensitivity analysis shows the ability of the proposed sensor to detect small changes in the order of 10−4 in the sample dielectric constant. The results of various experiments carried out on drug tablets are reported to demonstrate the potential multifunctional capabilities of the sensor in moisture sensing, counterfeit drug detection, and contamination screening. The measurement and simulation results obtained in mm-wave hold promise for WGM to be used for sensing biological solutions in terahertz range with very high sensitivity

Quantum Sensing with Scanning Near-Field Optical Photons Scattered by an Atomic-Force Microscope Tip

Scattering scanning near-field optical microscopy (s-SNOM) is known as a promising technique for overcoming Abbe diffraction limit and substantially enhancing the spatial resolution in spectroscopic imaging. The s-SNOM works by exposing an atomic force microscope (AFM) tip to an optical electromagnetic (EM) field, while the tip is so close to a sample that the incident beam lies within the near-field regime and displays nonlinear behaviour. We suggest replacing the incident field by quantized EM fields, i.e. photons, and propose a quantum model for the suggested system, by employing electric-dipole approximation, image theory, and perturbation theory. Quantum state of scattered photons from the AFM tip is extracted from the proposed model, which contain information about electrical permittivity of the dielectric material beneath the tip. The permittivity of the sample can be extracted through spectroscopic setups. Our proposed scheme can be used for quantum imaging or quantum spectroscopy with high resolution.Comment: 4 pages and 3 figure

Effects of Traffic Air Pollution on Respiratory Health and Allergies in Schoolchildren

The objective of the study is to investigate gender differences in the respiratory effects of air pollution in schoolchildren. We studied 1397 schoolchildren from two locations in Egypt; Cairo city with high level of air pollution and Shbeen Al Koom in the Delta with low level of air pollution. Lung function testing was done by the Vitalograph spirometer. The Arabic version of ISAAC questionnaire was used (the International Study of Asthma and Allergies in Childhood). Air pollution measurements were collected from the Government sites in both locations. Boys in Shbeen Al Koom had significantly (p< 0.05) higher lung function tests than boys in Cairo. There was no significant differences in lung function tests between girls in both locations. Children in Cairo had significantly (p< 0.01) higher prevalence rates of asthma, rhinitis and eczema than children in Shbeen Al Koom. The prevalence rates of ever rhinitis were 6% and 3% higher in boys and girls in Cairo compared with Shbeen Al Koom, respectively. Children who developed rash less than 2 years of age were 2% and 5% higher in boys and girls in Cairo compared with Shbeen Al Koom, respectively. The prevalence of other allergic symptoms were 2-3% and 3-5% higher in boys and girls in Cairo compared with Shbeen Al Koom, respectively. The present study shows the adverse respiratory effects of exposure to traffic air pollution on schoolchildren showing gender difference. The study will help to implement strategic health intervention programmes to improve the respiratory health of children

MAC-Oriented Programmable Terahertz PHY via Graphene-based Yagi-Uda Antennas

Graphene is enabling a plethora of applications in a wide range of fields due to its unique electrical, mechanical, and optical properties. In the realm of wireless communications, graphene shows great promise for the implementation of miniaturized and tunable antennas in the terahertz band. These unique advantages open the door to new reconfigurable antenna structures which, in turn, enable novel communication protocols at different levels of the stack. This paper explores both aspects by, first, presenting a terahertz Yagi-Uda-like antenna concept that achieves reconfiguration both in frequency and beam direction simultaneously. Then, a programmable antenna controller design is proposed to expose the reconfigurability to the PHY and MAC layers, and several examples of its applicability are given. The performance and cost of the proposed scheme is evaluated through full-wave simulations and comparative analysis, demonstrating reconfigurability at nanosecond granularity with overheads below 0.02 mm$^{2}$ and 0.2 mW.Comment: Accepted for presentation in IEEE WCNC '1

Energy models: Methods and characteristics

Given the importance of models in complicated problem solving, an inappropriate energy model can lead to inaccurate decisions and poor policy prescriptions. This paper aims at developing a decision support tool with which the selection of appropriate model characteristics can be facilitated for developing countries. Hence, it provides a comparative overview of different ways of energy models characterization and extracts the underlying relationships amongst them. Moreover, evolution of dynamic characteristics of energy models for developing countries is identified according to the previous studies on the developed and developing countries. To do this, it reviews the related literature and follows a systematic comparative approach to achieve its purposes. These findings are helpful in cases where model developers themselves are looking for appropriate characteristics in terms of certain purpose or situation

Improving financial investment by deep learning method: predicting stock returns of Tehran stock exchange companies

Safe investment can be experienced by incorporating human experience and modern predicting science. Artificial Intelligence (AI) plays a vital role in reducing errors in this winning layout. This study aims at performance analysis of Deep Learning (DL) and Machine Learning (ML) methods in modellingand predicting the stock returns time series based on the return rate of previous periods and a set of exogenous variables. The data used includes the weekly data of the stock return index of 200 companies included in the Tehran Stock Exchange market from 2016 to 2021. Two Long Short-Term Memory (LSTM)and Deep Q-Network (DQN) models as DL processes and two Random Forest (RF) and Support Vector Machine (SVM) models as ML algorithms were selected. The results showed the superiority of DLalgorithms over ML, which can indicate the existence of strong dependence patterns in these time series, as well as relatively complex nonlinear relationships with uncertainty between the determinant variables. Meanwhile, LSTM with R-squared equals to 87 percent and the analysis of the results of five other evaluation models have shown the highest accuracy and the least error of prediction. On the other hand, the RF model results in the least prediction accuracy by including the highest amount of error

Energy models: Methods and characteristics

Given the importance of models in complicated problem solving, an inappropriate energy model can lead to inaccurate decisions and poor policy prescriptions. This paper aims at developing a decision support tool with which the selection of appropriate model characteristics can be facilitated for developing countries. Hence, it provides a comparative overview of different ways of energy models characterization and extracts the underlying relationships amongst them. Moreover, evolution of dynamic characteristics of energy models for developing countries is identified according to the previous studies on the developed and developing countries. To do this, it reviews the related literature and follows a systematic comparative approach to achieve its purposes. These findings are helpful in cases where model developers themselves are looking for appropriate characteristics in terms of certain purpose or situation

A case report of congenital myasthenic syndrome caused by a mutation in the CHRNE gene in the Iranian population

Congenital myasthenic syndrome (CMS) refers to a heterogeneous group of inherited disorders, characterized by defective transmission at the neuromuscular junction (NMJ). Patients with CMS showed similar muscle weakness, while other clinical manifestations are mostly dependent on genetic factors. This disease, caused by different DNA mutations, is genetically inherited. It is also associated with mutations of genes at NMJ, involving the acetylcholine receptor (AChR) subunits. Here, we present the case of a five-year-old Iranian boy with CMS, undergoing targeted sequencing of a panel of genes, associated with arthrogryposis and CMS. The patient had six affected relatives in his genetic pedigree chart. The investigations indicated a homozygous single base pair deletion at exon 12 of the CHRNE gene (chr17:4802186delC). This region was conserved across mammalian evolution and was not submitted to the 1000 Genomes Project database. Overall, the CHRNE variant may be classified as a significant variant in the etiology of CMS. It can be suggested that the Iranian CMS population carry regional pathogenic mutations, which can be detected via targeted and whole genome sequencing

Reprogrammable graphene-based metasurface mirror with adaptive focal point for THz imaging

Recent emergence of metasurfaces has enabled the development of ultra-thin flat optical components through different wavefront shaping techniques at various wavelengths. However, due to the non-adaptive nature of conventional metasurfaces, the focal point of the resulting optics needs to be fixed at the design stage, thus severely limiting its reconfigurability and applicability. In this paper, we aim to overcome such constraint by presenting a flat reflective component that can be reprogrammed to focus terahertz waves at a desired point in the near-field region. To this end, we first propose a graphene-based unit cell with phase reconfigurability, and then employ the coding metasurface approach to draw the phase profile required to set the focus on the target point. Our results show that the proposed component can operate close to the diffraction limit with high focusing range and low focusing error. We also demonstrate that, through appropriate automation, the reprogrammability of the metamirror could be leveraged to develop compact terahertz scanning and imaging systems, as well as novel reconfigurable components for terahertz wireless communications.Peer ReviewedPostprint (published version