Design and Numerical Analysis of Hyperbolic Metamaterial Based Ultrasensitive E. Coli Sensor

We proposed an extremely sensitive \textit{E. Coli} sensor based on a hyperbolic metamaterial structure combining ultra-thin Ag-Al$_2$O$_3$ layers to minimize metallic optical loss. The principle relied on detecting the change in the resonance wavelength due to the interaction of bacteria with the surrounding aqueous environment by utilizing the finite-difference time-domain numerical technique. Our proposed hyperbolic metamaterial \textit{E. Coli} sensor operated in the range from visible to near-infrared wavelengths exhibiting strong bulk plasmon polaritons at the hyperbolic regime ($\lambda \geq$ 460 nm). An anisotropic hyperbolic range was obtained theoretically by solving the effective medium theory. An outstanding sensitivity of 9000 nm per bacteria was achieved for a bulk plasmon-polariton mode. The hyperbolic metamaterial was the origin of obtaining such extremely high sensitivity; no bulk plasmon polaritons were found without hyperbolic metamaterial. We analyzed the effect of different shapes in two-dimensional Ag differential grating on sensing performance. Additionally, we compared the performance parameters of our proposed \textit{E. Coli} sensor with recently demonstrated sensors. Our proposed hyperbolic metamaterial structure has the potential as a highly sensitive \textit{E. Coli} sensor operating in a wide range of wavelengths for label-free detection.Comment: this paper comprises 6 pages, 9 figures and 1 table, and accepted in IEEE TENCON 202

Graphene Metamaterials Based Plasmon-Induced Terahertz Modulator for High-Performance Multiband Filtering and Slow Light Applications

We proposed multilayered graphene (Gr)-based surface plasmon resonance-induced high-performance terahertz (THz) modulators with tunable resonance frequencies. Several THz plasmonic modulators based on Gr metamaterials were previously reported; however, these modulators had small group delay, low extinction ratio (ER), and difficult-to-tune resonant frequency without structural parameters in the THz range. A comprehensive investigation employing the finite-difference time-domain (FDTD) simulation technique revealed high group delay, broad tunability independent of structural parameters, and large ER for our proposed quadband and pentaband plasmonic modulators. We obtained tunable group delays with a maximum of 1.02 ps and 1.41 ps for our proposed quadband and pentaband plasmonic modulators, respectively, which are substantially greater compared to previously reported Gr-based metamaterial structures. The maximum ER of 22.3 dB was obtained which was substantially high compared to previous reports. Our proposed modulators were sensitive to the polarization angle of incident light; therefore, the transmittance at resonant frequencies was increased while the polarization angle varied from 0 to 180 degree. These high-performance plasmonic modulators have emerging potential for the design of optical buffers, slow light devices, multistop band filters, integrated photonic circuits, and various optoelectronic systems

The Study of Optical Properties for Ordered and Disordered Silicon Nanowire Structures

We designed ordered and disordered silicon (Si) nanowire structures and analyzed their optical performance using the finite-difference time-domain (FDTD) technique. We studied the orderness of nanowire structures by calculating scalar variance. This study reveals that utilizing disorder structures can increase the average absorbance of Si nanowire structures. Spatial electric field distributions provided insights into light-matter interaction, indicating that disorder structures had higher path lengths compared to the periodic structure. We achieved an average absorbance of 41.46% for the hyperuniform Si nanowire structure with a maximum absorbance of 78.18%. Intuitively, we obtained ~70% high absorbance compared to periodic Si nanowire structure. Our findings will be conducive to designing new efficient solar cells and photodetectors.Comment: This paper includes 4 pages, 5 figures, and 1 tabl

Usefulness of pleural fluid cholesterol in the diagnosis of tuberculous pleural effusion

Background: Tuberculous pleural effusion (TPE) is the most common etiology of exudative pleural effusion in high tuberculosis burden countries like Bangladesh. The usefulness of pleural fluid cholesterol for the diagnosis of TPE is not evaluated yet. This study aimed to assess the usefulness of pleural fluid cholesterol for the diagnosis of TPE. Methods: This cross-sectional study was conducted at the department of respiratory medicine at Bangabandhu Sheikh Mujib medical university. A total of thirty-five TPE was included in this study. Pleural fluid aspiration followed by cytological (total count, differential count), and biochemical (protein, glucose, lactate dehydrogenase, adenosine deaminase, and cholesterol) investigations were done. At the same time, blood was sent for biochemical (protein, glucose, and lactate dehydrogenase) investigation. Pleural biopsy followed by a histopathological examination was done to confirm TPE. Ethical clearance was obtained from the institutional review board (IRB) prior to starting this study. Results: In our study, the mean age of the participants was 35.54±14.13 years, and male predominant (74.3%). The mean pleural fluid cholesterol was 99.87±23.82 mg/dl. With a cut of value 69.85, the sensitivity, specificity, and accuracy were 97.14%, 57.14%, and 77.14% respectively. Conclusions: Pleural fluid cholesterol has significant diagnostic usefulness for the diagnosis of tuberculous pleural effusion

Binding of the human nucleotide excision repair proteins XPA and XPC/HR23B to the 5R-thymine glycol lesion and structure of the cis-(5R,6S) thymine glycol epimer in the 5′-GTgG-3′ sequence: destabilization of two base pairs at the lesion site

The 5R thymine glycol (5R-Tg) DNA lesion exists as a mixture of cis-(5R,6S) and trans-(5R,6R) epimers; these modulate base excision repair. We examine the 7:3 cis-(5R,6S):trans-(5R,6R) mixture of epimers paired opposite adenine in the 5′-GTgG-3′ sequence with regard to nucleotide excision repair. Human XPA recognizes the lesion comparably to the C8-dG acetylaminoflourene (AAF) adduct, whereas XPC/HR23B recognition of Tg is superior. 5R-Tg is processed by the Escherichia coli UvrA and UvrABC proteins less efficiently than the C8-dG AAF adduct. For the cis-(5R, 6S) epimer Tg and A are inserted into the helix, remaining in the Watson–Crick alignment. The Tg N3H imine and A N6 amine protons undergo increased solvent exchange. Stacking between Tg and the 3′-neighbor G•C base pair is disrupted. The solvent accessible surface and T2 relaxation of Tg increases. Molecular dynamics calculations predict that the axial conformation of the Tg CH3 group is favored; propeller twisting of the Tg•A pair and hydrogen bonding between Tg OH6 and the N7 atom of the 3′-neighbor guanine alleviate steric clash with the 5′-neighbor base pair. Tg also destabilizes the 5′-neighbor G•C base pair. This may facilitate flipping both base pairs from the helix, enabling XPC/HR23B recognition prior to recruitment of XPA

Tunable Multistate Terahertz Switch Based on Multilayered Graphene Metamaterial

We proposed plasmonic effect based narrow band tunable terahertz switches consisting of multilayered graphene metamaterial. Though several terahertz optical switches based on metamaterials were previously reported, these switches had complicated fabrication processes, limited tunability, and low modulation depths. We designed and simulated ingenious four and eight state terahertz optical switch designs that can be functional for multimode communication or imaging using the finite-difference time-domain simulation technique. The plasmonic bright modes and transparency regions of these structures were adjusted by varying the chemical potential of patterned graphene layers via applying voltage in different layers. The structures exhibited high modulation depth and modulation degree of frequency, low insertion loss, high spectral contrast ratio, narrow bandwidth, and high polarization sensitivity. Moreover, our proposed simple fabrication process will make these structures more feasible compared to previously reported terahertz switches. The calculated modulation depths were 98.81% and 98.71%, and maximum modulation degree of frequencies were ~61% and ~29.1% for four and eight state terahertz switches, respectively. The maximum transmittance in transparency regions between bright modes and the spectral contrast ratio were enumerated to be 95.9% and ~96%, respectively. The maximum insertion losses were quite low with values of 0.22 dB and 0.33 dB for four and eight state terahertz switches, respectively. Our findings will be beneficial in the development of ultra-thin graphene-based multistate photonic devices for digital switching, sensing in terahertz regime.Comment: 17 Pages, 8 Figure