A Numerical Approach to Design the Kretschmann Configuration Based Refractive Index Graphene-MoS2 Hybrid Layers With TiO2-SiO2 Nano for Formalin Detection

In this paper, a Kretschmann configuration based surface plasmon resonance (SPR) sensor is numerically designed using graphene-MoS2 hybrid structure TiO2-SiO2 nano particles for formalin detection. In this design, the observations of SPR angle versus minimum reflectance and SPR frequency (FSPR) versus maximum transmittance (Tmax) are considered. The chitosan is used as probe legend to perform reaction with the formalin (40% formaldehyde) which acts as target legend. In this paper, both graphene and MoS2 are used as biomolecular acknowledgment element (BAE) and TiO2 as well as SiO2 bilayers is used to improve the sensitivity of the sensor. The numerical results show that the variation of FSPR and SPR angles for inappropriate sensing of formalin is quite insignificant which confirms the absence of formalin. On the other hand, these variations for appropriate sensing are considerably significant that confirm the presence of formalin. At the end of this article, the variation of sensitivity of the proposed biosensor is measured in corresponding to the increment of a refractive index with a refractive index step 0.01 refractive index unit (RIU). In inclusion of TiO2-SiO2 bilayers with graphene-MoS2, a maximum sensitivity of 85.375% is numerically calculated

FDTD Analysis Fiber Optic SPR Biosensor for DNA Hybridization: A Numerical Demonstration with Graphene

This article illustrates a design and finite difference time domain (FDTD) method based on analysis of fiber optic surface plasmon resonance (SPR) biosensor for biomedical application especially for DNA-DNA hybridization. The fiber cladding at the middle portion is constructed with the proposed hybrid of gold (Au), graphene, and a sensing medium. This sensor can be recognized adsorption of DNA biomolecules onto sensing medium of PBS saline using attenuated total reflection (ATR) technique. The refractive index (RI) is varied owing to the adsorption of different concentration of biomolecules.  Result states that the sensitivity with a monolayer of graphene will be improved up to 40% than bare graphene layer. Owing to increased adsorption capability of DNA molecules on graphene, sensitivity increases compared to the conventional gold thin film SPR biosensor. Numerical analysis shows that the variation of the SPR angle for mismatched DNA strands is quite negligible, whereas that for complementary DNA strands is considerable, which is essential for proper detection of DNA hybridization.  Finally, the effect of Electric field distribution on inserting graphene layer is analyzed incorporating the FDTD technique by using Lumerical FDTD solution software

Graphene-MoS2-Au-TiO2-SiO2 Hybrid SPR Biosensor: A New Window for Formalin Detection

In this article, numerically a surface plasmon resonance (SPR) biosensor is developed based on Graphene-M­­­­OS2-Au-TiO2-SiO2 hybrid structure for formalin detection. This developed sensor sensed the presence of formalin by applying attenuated total reflection (ATR). In ATR method, we developed and observed two characteristics curve, one is “SPR angle versus minimum reflectance (Rmin)” and another is “SPR frequency (SPRF) versus maximum transmittance (Tmax). In the proposed sensor, Chitosan is used as probe legend to perform specific reaction with the formalin (40% formaldehyde) as target legend. Here, graphene and MoS2 both are used as biomolecular acknowledgment element (BAE). And TiO2 as well as SiO2 bilayers are used to improve sensor sensitivity and Gold (Au) is to sharp SPR curve. In numerical results, the variation of SPRF and SPR angle for inappropriate sensing of formalin is quiet insignificant which confirms the absence of formalin. On the other hand, these variations for appropriate sensing is considerably significant that confirms the presence of formalin. At the end of this article, a study of variation of sensitivity of the proposed biosensor in corresponding to the increment of refractive index with a refractive index step 0.01 RIU is measured. In inclusion of TiO2-SiO2 bilayers with Graphene-M­­­­OS2, maximum sensitivity of 85.375% more is numerically reported

On secrecy performance of mixed generalized Gamma and Málaga RF-FSO variable gain relaying channel

The emergence of an array of new wireless networks has led researchers to evaluate the prospect of utilizing the physical properties of the wireless medium in order to design secure systems. In this paper, the physical layer secrecy performance of a mixed radio frequency-free space optical (RF-FSO) system with variable gain relaying scheme is investigated in the presence of an eavesdropper. We assume that the eavesdropper can wiretap the transmitted confidential data from the RF link only. It is further assumed that the main and eavesdropper RF links are modeled as generalized Gamma (GG) fading channel, and the free space optical (FSO) link experiences Málaga turbulence with pointing error impairment. Our primary concern is to protect this confidential information from being wiretapped. Besides pointing error, the atmospheric turbulence and two types of detection techniques (i.e. heterodyne detection and intensity modulation with direct detection) are also taken into consideration. Utilizing amplify-and-forward (AF) scheme, the novel mathematical closed-form expressions for average secrecy capacity, lower bound of secrecy outage probability, and strictly positive secrecy capacity are derived. As both the links (RF and FSO) undergo generalized fading channels, the derived expressions are also general. We present a unification of some existing works utilizing the proposed model to better clarify the novelty of this work. Finally, all the derived expressions are justified via Monte-Carlo simulations

Design and Performance Analysis of a Triple-band Rectangular Slot Microstrip Patch Antenna for Wi-Fi, Wi-MAX and Satellite Applications

A triple-band microstrip patch antenna is presented in this article with detail investigation of its working mechanism and performance characteristics. The antenna consists of a rectangular slot on the patch to achieve multiband operation. Three distinct frequencies of 2.4 GHz, 5.5 GHz and 7.5 GHz are achieved with return losses of 27 dB, 29 dB and 29 dB respectively. The Impedance Bandwidths are 70 MHz (2.52 GHz-2.44 GHz) at 2.4 GHz, 220 MHz (5.65 GHz-5.43 GHz) at 5.5 GHz and 250 MHz (7.57 GHz-7.32 GHz) at 7.5 GHz, which satisfy the requirements of Wi-Fi, Wi-MAX and satellite communications bands. The fabricated prototype of the antenna has total dimension of 53×53×1.6 mm3 over FR4 substrate. The antenna is simple and has sensible radiation characteristics with considerable gain. This work also focuses on developing a Link Budget model for its application in satellite communication. Most notably, it examines overall system efficiency and optimum path loss, distance analysis, system noise temperature, signal to noise power ratio, the size of antenna and the overall customer satisfactions. The highest gain of the antenna is achieved as 3.5 dB in the band (5.65 GHz-5.43 GHz), while the highest directivity and bandwidth are found as 8.7 dBi and 250 MHz respectively in the higher operating band. The affordable agreement between the simulated and measuring outcomes justifies that the antenna is often applicable for Wi-Fi (2.4 GHz), Wi-MAX (5.25 – 5.85 GHz) and satellite (7.24 – 7.57 GHz) communications

DNA Hybridization Detection Based on Resonance Frequency Readout in Graphene on Au SPR Biosensor

This paper demonstrates a numerical modeling of surface plasmon resonance (SPR) biosensor for detecting DNA hybridization by recording the resonance frequency characteristics (RFC). The proposed sensor is designed based on graphene material as biomolecular recognition elements (BRE) and the sharp SPR curve of gold (Au). Numerical analysis shows that the variation of RFC for mismatched DNA strands is quiet negligible whereas that for complementary DNA strands is considerably countable. Here, graphene is used to perform faster immobilization between target DNA and probe DNA. The usage of graphene also changes the RFC that ensure hybridization of DNA event by utilizing its optochemical property. In addition, proposed sensor successfully distinguishes between hybridization and single-nucleotide polymorphisms (SNP) by observing the variation level of RFC and maximum transmittance. Therefore, the proposed frequency readout based SPR sensor could potentially open a new window of detection for biomolecular interactions. We also highlight the advantage of using graphene sublayer by performing the sensitivity analysis. Sandwiching of each graphene sublayer enhances 95% sensitivity comparing with conventional SPR sensor

Agronomic approaches to biofortify iron in tomato

The study was conducted to biofortify Fe in tomato fruit. Seven tomato varieties were tested in this study to screen out the potential variety for biofortification. Based on Fe concentrations of tomato fruit, BARI Tomato-14 was selected as test crop. Six different methods for Fe application viz. 100% as seedling priming, 50% in soil + 50% as foliar spray at seedling stage, 50% as seedling priming + 50% as foliar spray, 100% as foliar spray at seedling stage, 100% as foliar spray at flowering stage and 100% as foliar spray at fruiting stage @ 4 kg Fe ha-1. Iron was applied for 3 times at 7 day interval at all growth stages. Experiments were laid out in a completely randomized design (CRD) with 3 replications. Different application methods of Fe significantly influenced the growth, yield contributing characteristics, yield, biochemical constituents, nutrient concentrations and their uptake by BARI Tomato-14. The highest values of most of the studied parameters including Fe content and uptake were recorded from the application of 50% Fe as seedling priming + 50% Fe as foliar spray. Significant and positive correlations among the growth and yield contributing parameters due to the application of Fe were observed. Interestingly the highest vitamin-C, protein, lycopene, N, K and Ca contents and uptake were observed in 50% as seedling priming + 50% as foliar spray of Fe @ 4 kg ha-1. Except few most of the studied nutrients were negatively correlated with Fe. Iron was biofortified by 66.28 µg g-1 in BARI Tomato-14. Results suggest that application of 2 kg Fe ha-1 as seedling priming + 2 kg Fe ha-1 as foliar spray at seedling stage for 3 times at 7 days interval along with the recommended doses of NPK fertilizers in soil can be practiced for Fe biofortification in tomato. [J Bangladesh Agril Univ 2022; 20(4.000): 362-372

How big of an impact do asymptomatic people have on the dynamics of an epidemic?

Asymptomatic carriers serve as a potential source of transmission of epidemic diseases. Exposed people who develop symptoms only get tested and remain isolated in their homes or sometimes in hospitals when needed. In contrast, the asymptomatic individuals go untested and spread the disease silently as they roam freely throughout their entire infectious lifetime. The work intends to explore the role of asymptomatic carriers in the transmission of epidemic diseases and investigate suitable optimal control strategies. We propose a SEIAQR compartmental model subdividing the total population into six different compartments. To illustrate the model’s implication, we estimate the number of asymptomatic individuals using COVID-19 data during June 9–July 18, 2021 from Bangladesh. We then analyze the model to explore whether the epidemic subsides if the asymptomatic individuals are tested randomly and isolated. Finally, to gain a better understanding of the potential of this unidentified transmission route, we propose an optimal control model considering two different control strategies: personal protective measures and isolation of asymptomatic carriers through random testing. Our results show that simultaneous implementation of both control strategies can reduce the epidemic early. Most importantly, sustained effort in identifying and isolation of asymptotic individuals allows relaxation in personal protective measures

A performance comparison of heterostructure surface plasmon resonance biosensor for the diagnosis of novel coronavirus SARS-CoV-2

This paper presents a performance comparison of heterostructure surface plasmon resonance (SPR) biosensors for the application of Novel Coronavirus SARS-CoV-2 diagnosis. The comparison is performed and compared with the existing literature based on the performance parameters in terms of several prisms such as BaF2, BK7, CaF2, CsF, SF6, and SiO2, several adhesion layers such as TiO2, Chromium, plasmonic metals such as Ag, Au, and two-dimensional (2D) transition metal dichalcogenides materials such as BP, Graphene, PtSe2 MoS2, MoSe2, WS2, WSe2. To study the performance of the heterostructure SPR sensor, the transfer matrix method is applied, and to analyses, the electric field intensity near the graphene-sensing layer contact, the finite-difference time-domain approach is utilized. Numerical results show that the heterostructure comprised of CaF2/TiO2/Ag/BP/Graphene/Sensing-layer has the best sensitivity and detection accuracy. The proposed sensor has an angle shift sensitivity of 390°/refractive index unit (RIU). Furthermore, the sensor achieved a detection accuracy of 0.464, a quality factor of 92.86/RIU, a figure of merit of 87.95, and a combined sensitive factor of 85.28. Furthermore, varied concentrations (0–1000 nM) of biomolecule binding interactions between ligands and analytes have been observed for the prospects of diagnosis of the SARS-CoV-2 virus. Results demonstrate that the proposed sensor is well suited for real-time and label-free detection particularly SARS-CoV-2 virus detection