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A compact, conformal, all-textile wearable antenna is proposed in this paper for the 2.45 GHz ISM (Industrial, Scientific and Medical) band. The integrated design consists of a monopole radiator backed by a 2 × 1 Electromagnetic Band Gap (EBG) array, resulting in a small form factor suitable for wristband applications. An EBG unit cell is optimized to work in the desired operating band, the results of which are further explored to achieve bandwidth maximization via floating EBG ground. A monopole radiator is made to work in association with the EBG layer to produce the resonance in the ISM band with plausible radiation characteristics. The fabricated design is tested for free space performance analysis and subjected to human body loading. The proposed antenna design achieves bandwidth of 2.39 GHz to 2.54 GHz with a compact footprint of 35.4 × 82.4 mm2. The experimental investigations reveal that the reported design adequately retains its performance while operating in close proximity to human beings. The presented Specific Absorption Rate (SAR) analysis reveals 0.297 W/kg calculated at 0.5 W input power, which certifies that the proposed antenna is safe for use in wearable devices.

This paper introduces an optical orthogonal frequency division multiplexing (OFDM)-based hyperchaotic key generation encryption approach that can improve confidentiality in visible light communication (VLC) networks. Using a hyperchaotic four-dimensional method, the bipolar real-valued OFDM signal can be used for constructing dynamic cypher keys modified at every frame over the communication time, resulting in a superior degree of protection against statistical and correlation attacks. In accordance with our findings, this approach decreases the ratio of peak-to-average power of the transmitted signal, and enhances the bit error rate efficiency and secrecy capacity of the OFDM-based VLC network, which improves confidentiality.

The theoretical analysis of hybrid surface plasmon polaritons in a planar waveguide filled with chiral material surrounded by graphene layers is presented in this manuscript. The Kobo formula is us...

This paper presents a theoretical study on the propagation of electromagnetic surface waves supported by the metamaterial-filled bi-layered graphene structure. The effective surface conductivity approach based upon the Kubo’s formalism is used to model the atomically thick graphene layer, while the analytical modeling of the metamaterials used the framework of causality principle-based Kramers-Kroing relations. With respect to the index of refraction, the two configurations of metamaterials have been considered—i.e., double positive (DPS) and double negative (DNG). The impedance boundary conditions (IBCs) have been employed at the interface for the computation of characteristics equations of odd and even surface modes under DPS and DNG configurations. The numerical results regarding the dispersion relations, effective mode index, and phase speed for the odd and even modes of electromagnetic surface waves supported by each configuration of structure have been presented. Further, the influence of chemical potential and thickness of metamaterial filling in parallel graphene layers on the wave propagation characteristics has been analyzed. To check the accuracy of the numerical results, special conditions were employed, which converge to the published results. The proposed work may have potential applications in plasmonic based logic designs, renewable energy devices, THz surface wave guides, and near-field communication devices.

The characteristics of hybrid surface plasmon modes in a double-layer graphene cylindrical waveguide filled with metamaterials are theoretically investigated. The dispersion relation for different configurations of metamaterials (double positive (DPS)-graphene-double negative (DNG)-graphene-DPS and DNG-graphene-DPS-graphene-DNG) is derived by solving Maxwell’s equations for cylindrical symmetry and implementing impedance boundary conditions at the interface. The Kubo formalism is used for the modeling of the electromagnetic response of graphene. The influence of the interlayer distance of graphene, chemical potential of graphene, and permittivity of interlayer metamaterials on the dispersion curve, effective mode index, propagation length, and phase velocity are presented. It is observed that the existence of double layers of graphene along with metamaterials provides better control and tuning of the propagation of the surface waves. The coupled surface plasmon polariton (SPP) and surface phonon polariton (SPhP) in the optical regime are observed due to the coupling of electromagnetic waves between graphene layers. The forward- and backward-propagating surface waves for the fundamental mode are studied for different waveguide configurations. The active trapping of light and tunable fast and ultraslow plasmon modes for both forward and backward propagation modes for the proposed design may enable the realization of potential optoelectronic applications, such as modulators, fast forward-wave amplifiers, frequency selectors, back wave contra couplers, thermal sensors, circular polarizers, slow light devices, infrared (IR) and molecular spectroscopy, on-chip buffers, communication switches, and energy devices.

The theoretical analysis of hybrid surface wave propagation at chiral-plasma planar interface is presented in this manuscript. The dispersion relation is obtained for the proposed structure by appl...

This study examines the analytical and numerical solution of electromagnetic surface waves supported by a resistive metasurface-covered grounded metamaterial structure. To simulate the metamaterial, the Kramers–Kronig relation based on the causality principle is used, while the modeling of the resistive metasurface has been done by implementing the impedance boundary conditions. The analytical expressions for the field phasors of surface waves are developed for the transverse magnetic (TM) polarized mode and transverse electric (TE) polarized mode. The characteristic equations are computed for both modes, and the unknown propagation constant is evaluated numerically in the kernel. After computation, the dispersion curves, electric field profiles, effective mode index ($$N_{eff}$$ N eff ), and phase speeds ($$v_{p}$$ v p ) are presented for both the TM and TE polarized modes. To study the tunability of surface waves, the influence of the thickness of the metamaterial slab ($$d$$ d ), effective permittivity of the metamaterial ($$\varepsilon_{1}$$ ε 1 ), thickness of the resistive metasurface ($$t$$ t ), and effective permittivity of the metasurface ($$\varepsilon_{r}$$ ε r ) on all the numerical results has been studied. However, the geometrical parameters are found to be more sensitive to the effective mode index ($$N_{eff}$$ N eff ) and phase speed ($$v_{p}$$ v p ) of the surface waves. The results are consistent with the published results, which reflects the accuracy of the work. It is concluded that the appropriate choice of parameters can be used to achieve surface waves with the desired characteristics in the GHz range. The present work may have potential applications in surface waveguide design, surface wave speed controllers, surface communication devices, and light trapping configurations.

The theoretical analysis of transverse electric surface waves in ferrite medium surrounded by isotropic plasma layers is presented in this manuscript. Maxwell’s equations in differential form are used, and we impose the boundary conditions to acquire the dispersion relation to formulate the proposed structure. The influence of number density, separation distance between the layers of plasma, and dielectric permittivity of ferrite film on the normalized propagation constant is studied. It is concluded from the result obtained that if the number density and values of dielectric permittivity of ferrite film increases the propagation constant Re(β) tends to decreases whereas the increase in separation distance between the layers of plasma tends to increase the propagation constant Re(β). Furthermore, to verify the surface waves, the normalized field distribution for plasma medium as well as ferrite medium are also presented in this manuscript. The present work has potential applications in communication, drug delivery, cancer treatment, and ferrite sensing waveguide structures in the GHz frequency regime.

A theoretical investigation has been carried out on the propagation of hybrid surface waves supported by a chiral loaded resistive metasurface. The canonical boundary-value problem approach is used in the analytical modeling of this problem. To simulate the resistive metasurface, an impedance boundary condition is applied at the chiral-resistive metasurface interface. The characteristics equation was solved numerically in the kernel for computing the unknown value of the propagation constant ( $$\beta $$ ) against its respective frequency ( $$\omega $$ ). The numerical results reveal that the chiral loaded resistive metasurface supports the upper and lower hybrid surface modes in the GHz range. The propagation bandgap between the upper and lower hybrid surface modes is highly sensitive to the chiral strength (ξ), and the propagation bandgap can be tuned with the variation of chirality. The surface wave characteristics i.e., the dispersion curve, effective mode index ( $${N}_{\mathrm{eff}}$$ ), field profiles, and phase speeds ( $${v}_{p}$$ ), have been computed numerically for both the upper and lower hybrid surface modes. The influence of chirality (ξ), thickness ( $$t$$ ), permittivity of chiral medium ( $${\varepsilon }_{c}$$ ), and the permittivity of resistive metasurface ( $${\varepsilon }_{r}$$ ) on the resonance frequency, confinement, and phase speed of surface waves have been analyzed and their tunability has been discussed. The results’ validity has been checked under special conditions and the numerical results converge to the published results. The presented numerical results may have potential applications in chip chiral sensing, enantiomeric detection, biochemical sensing, metasurface designing, and near-field hybrid surface communication devices.

Since late 2019, Coronavirus Disease 2019 (COVID-19) has spread all over the world. The disease is highly contagious, and it may lead to acute respiratory distress (ARD). Medical imaging can play an important role in classifying, detecting, and measuring the severity of the virus. This study aims to provide a novel auto-detection tool that can detect abnormal changes in conventional X-ray images for confirmed COVID-19 cases. X-ray images from patients diagnosed with COVID-19 were converted into 19 different colored layers. Each layer represented objects with similar contrast that could be defined as a specific color. The objects with similar contrasts were formed in a single layer. All the objects from all the layers were extracted as a single-color image. Based on the differentiation of colors, the prototype model was able to recognize a wide spectrum of abnormal changes in the image texture. This was true even if there was minimal variation of the contrast values of the detected uncleared abnormalities. The results indicate that the proposed novel method can detect and determine the degree of lung infection from COVID-19 with an accuracy of 91%, compared to the opinions of three experienced radiologists. The method can also efficiently determine the sites of infection and the severity of the disease by classifying the X-rays into five levels of severity. Thus, the proposed COVID-19 autodetection method can identify locations and indicate the degree of severity of the disease by comparing affected tissue with healthy tissue, and it can predict where the disease may spread.

The active tuning of surface waves supported by left-handed materials (LHMs) is a major challenge for their practical applications and usability, and graphene has been proposed as an agent for the active tuning of surface waves. In this study, tunable surface waves supported by graphene-layered LHM structures are investigated theoretically. The analytical and numerical results are computed for transverse electric (TE) and transverse magnetic (TM)-polarized surface waves. According to the spectral range, two configurations of LHMs (i.e., gigahertz (GHz)-LHM and terahertz (THz)-LHM) are discussed. The physical modeling of graphene is done using the conductivity model based on random phase approximation-based Kubo formalism. The split ring resonator (SRR) model and Kramers–Kronig relations-based causality principle are used for the physical realization of LHMs. To simulate the graphene-layered LHM interface, impedance boundary conditions (IBCs) are applied. Numerical results are computed for dispersion curves, effective wave numbers, and field profiles of surface waves supported by graphene-covered GHz-LHM and THz-LHM. The influence of graphene parameters on the resonance frequency, dispersion curves, and confinement characteristics of surface waves is analyzed for both configurations of LHMs. It is concluded that the graphene-covered GHz-LHM structure supports the tunable surface waves as surface plasmon polaritons (SPPs) support TM-polarized waves. However, with the TE-polarized surface wave, the structure supports the surface polaritons, which do not depend upon the graphene parameters. For the case of the graphene-covered THz-LHM structure, it is concluded that the structure supports the plasmon modes for both polarized waves and the resonance frequency ranges from THz to infrared (IR). The confinement of the TE-polarized surface waves on the graphene layer can be enhanced up to fourfold as compared to the suspended monolayer graphene by using a THz-LHM substrate. Further, the numerical results are found to be consistent with the literature under special conditions. The proposed graphene-layered LHM structure may have potential uses in the active tuning of surface waves, near-field communication and imaging devices, surface waveguide design, and LHM-based metasurfaces.

This manuscript presents a theoretical analysis of hybrid surface wave propagation at the ferrite–anisotropic plasma planar interface. Maxwell’s equations in differential forms and impedance boundary conditions are used to solve the problem. The influence of the plasma frequency, cyclotron frequency, and the different permittivities of ferrite films on the dispersion curve are analyzed. Moreover, the propagation length, normalized phase speed, and normalized field distribution are also analyzed. The presented work may have potential applications in surface waveguide control, optical sensing, and wave propagation in the terahertz frequency range such as measurement of electron bunches, remote sensing, material characterization, medical and biological imaging.

Massive multiple-input multiple-output (MIMO) is a breakthrough wireless transmission technique proposed for future wireless standards due to its spectrum and energy efficiencies. However, pilot contamination constitutes a particularly significant impairment in multi-cell systems that utilise reciprocity-based channel estimation. This phenomenon results from the non-orthogonality of the pilot sequences in different cells. Given a large number of antennas employed in massive MIMO systems, conventional channel estimation schemes cannot mitigate this problem effectively without high computational complexity. In this study, a simple rateless space–time block code (RSTBC) is employed in the downlink transmission of a lossy multi-cell massive MIMO system to mitigate the effects of signal-to-interference-and-noise ratio (SINR) degradation resulting from pilot contamination. Specifically, a robust optimisation problem is formulated to maximise the minimum downlink SINR among all users. Simulation and analytical results for large numbers of antenna elements at the base station (BS) are provided to demonstrate the usefulness of the proposed scheme. The SINR and spectral efficiency analyses indicate that RSTBC can effectively mitigate downlink SINR degradation that is caused by pilot contamination. Experimental results for the proposed scheme are also included for a 2 × 2 MIMO system, and it agrees closely with the simulation.

The emergence of new material platforms, focused on nanotechnology, have resulted in a growing interest in their application to healing skin wounds. The skin forms an effective barrier against the external environment and consequently, rapid healing of wound tissue after injury is essential. Curcumin (diferuloylmethane) is a promising small molecule for the treatment of wounds based on its wound-healing activity and antioxidant and anti-inflammatory properties. However, its therapeutic application is limited by the poor skin permeability and bioavailability due to its poor solubility and low stability. Herein, curcumin loaded LNPs was prepared and characterized for their wound healing activity. Cytotoxicity assays indicated that curcumin-free and loaded nanoparticles were biocompatible with skin keratinocytes with no cytotoxic effects, suggesting that they did not interfere with cell proliferation during wound healing. Curcumin loaded LNPs exhibited potent in vitro antibacterial activity against gram-positive bacterial pathogens, particularly against Staphylococcus aureus, the most common wound bacterium. Fibroblast cell migration was observed using a scratch assay; upon treatment with curcumin loaded LNPs, wounded keratinocytes exhibited increased cell migration, which is a key feature of wound healing. The in vivo results showed that wounded rats treated with curcumin loaded LNPs exhibited enhanced dermal wound closure compared with the untreated control. After 12 days, the wounds treated with curcumin loaded LNPs achieved nearly full wound contraction compared with the untreated control, which had a wound size reduction of approximately 43%. Curcumin-loaded LNPs treated wounds showed advanced granulation tissue formation, characterized by greater collagen deposition. They also had lower myeloperoxidase activity, which is indicative of less inflammatory infiltration. Lower expression of matrix metalloproteinases (MMPs), especially MMP9, was characteristic of wounds treated with curcumin loaded LNPs. Overall, the results from this study highlight the advantages of using lignin as a nanocarrier to accelerate wound healing.

A theoretical analysis of the characteristics of the hybrid surface plasmon of a monolayer graphene-wrapped metamaterial-filled cylindrical waveguide is performed. The dispersion relations for different configurations of metamaterials [double positive (DPS)–graphene–DPS, DPS–graphene–double negative (DNG), DNG–graphene–DPS, and DNG–graphene–DNG] are simulated by solving Maxwell’s equations for cylindrical symmetry and implementing impedance boundary conditions at the interface. The electromagnetic response of graphene is modeled using Kubo’s formalism. The influence of the geometrical parameters of the waveguide structure, the chemical potential of graphene and the parameters of partnering materials on the dispersion curve, the effective mode index, and the phase velocity is presented. It is observed that the existence of graphene along with metamaterials provides better control and tuning of the propagation of the surface waves. The backward surface waves, forward surface waves, and slow surface waves for the fundamental mode are studied for different waveguide configurations. The results are found to be in accordance with the published literature. These results may have potential applications in tuning surface waves, waveguide technology, modulators, backward-wave amplifiers, traveling-wave masers, frequency selectors, circular polarizers, switching and phase compensation, and graphene-based slow-light devices.

Multiple-input multiple-output (MIMO) wireless technology in combination with orthogonal frequency-division multiplexing (MIMO-OFDM) is an attractive technique for next-generation wireless systems. However, the performance of wireless links is severely degraded due to various channel impairments which cause a decoding failure and lead to packet loss at the receiver. One technique to cope with this problem is the rateless space-time block code (RSTBC). This paper presents experimental results on the performance of a 2×2 MIMO-OFDM system with RSTBC as measured in a testbed implemented with field-programmable gate array (FPGA). The average bit error rate (BER) performance of the proposed scheme is evaluated experimentally, and the results agree closely with simulation and analytical upper bound. It has been shown that RSTBC can be implemented in real-world scenarios and guarantee the reliability of loss-prone wireless channels.

Background Community pharmacists (CPs) are the most accessible health care provider to the public, and they have huge duties to improve medication use especially among the pregnant women in their community. The objective of this study was to evaluate knowledge of CPs about the medication safety during pregnancy. Methods A prospective cross-sectional survey was carried out over practicing community pharmacists in a capital of Saudi Arabia (SA). Pharmacists were asked about the safety of each medicine during pregnancy. It involved both prescription-only medications (POM) and over-the-counter (OTC) medications. Both descriptive and analytic statistics were utilized. For descriptive analysis, results were expressed as numbers, percentages and mean (±SD and 95% CI). Results The response rate was (71.1%). Most of the respondents (69.6%) believed that alprazolam is not safe while 22% of respondents believed that it is used on basis of risk-benefit assessment. Also, most of CPs (65.2%) said that amoxicillin is safe, but a very few of CPs (11.7%) knew that tetracycline should be used only if potential benefits may outweigh the risk. Among non-prescribed analgesics, majority of CPs (92.6%) knew that acetaminophen is safe. About dietary supplements, 48.4% of CPs reported that Vitamin A supplements are not safe. There was significant difference observed between age groups of CPs in scores of knowledge test (P = 0.001). Conclusion Community Pharmacists are the most accessible health care providers who can help pregnant women with their medications use there are still gaps in knowledge where educational interventions are needed.

In this paper, we study the performance of loss-tolerant multiuser large-scale multiple-input multiple-output (LS-MIMO) system with rateless space time block code (RSTBC). Since large number of low-power antenna elements are deployed in LS-MIMO systems, there is always a possibility of transmission losses, which may degrade the system performance significantly. In such cases, packets may get lost or not decodable at the receiver resulting in wireless erasure channels. Hence, RSTBC is introduced in LS-MIMO downlink transmission to tackle this problem. Performance analysis and simulation results are provided to demonstrate the feasibility of the proposed scheme in such cases. It has been shown that RSTBC guarantees the reliability of lossy LS-MIMO system with low overhead and complexity.