Search Results (3)

The circular polarization of light flips its handedness after a conventional metallic mirror reflection. Therefore, a polarization-preserving metasurface is a crucially important element in a series of chiral photonic structures. They include tunable cholesteric LCs and anisotropic photonic crystals. Chiral structures are rich in interfacial localized modes including Tamm states. In this report, coupled modes formed as a result of the interaction between two chiral optical Tamm states or a chiral optical Tamm state and a chiral Tamm plasmon polariton are analytically and numerically investigated. It is shown that the effective control of coupled modes can be carried out by changing the pitch of the cholesteric and the angle between the optical axis of the cholesteric and the polarization-preserving anisotropic mirror. The influence of the metasurface period on the spectral characteristics of coupled modes is investigated. The possibility of realizing a bound state in the continuum of the Friedrich–Wintgen type, resulting from the destructive interference of coupled modes, which leads to the collapse of the resonance line corresponding to the chiral optical Tamm state, has been demonstrated. Full article

This study is an extension of current research into a novel class of synthetic antihypertensive drugs referred to as “bisartans”, which are bis-alkylated imidazole derivatives bearing two symmetric anionic biphenyltetrazoles. Research to date indicates that bisartans are superior to commercially available hypertension drugs, since the former undergo stronger docking to angiotensin-converting enzyme 2 (ACE2). ACE2 is the key receptor involved in SARS-CoV-2 entry, thus initiating COVID-19 infection and in regulating levels of vasoactive peptides such as angiotensin II and beneficial heptapeptides A(1-7) and Alamandine in the renin–angiotensin system (RAS). In previous studies using in vivo rabbit-iliac arterial models, we showed that Na⁺ or K⁺ salts of selected Bisartans initiate a potent dose–response inhibition of vasoconstriction. Furthermore, computational studies revealed that bisartans undergo stable binding to the vital interfacial region between ACE2 and the SARS-CoV-2 “receptor binding domain” (i.e., the viral RBD). Thus, bisartan homologs are expected to interfere with SARS-CoV-2 infection and/or suppress disease expression in humans. The primary goal of this study was to investigate the role of tetrazole in binding and the network of amino acids of SARS-CoV-2 Spike RBD-ACE2 complex involved in interactions with sartans. This study would, furthermore, allow the expansion of the synthetic space to create a diverse suite of new bisartans in conjunction with detailed computational and in vitro antiviral studies. A critical role for tetrazole was uncovered in this study, shedding light on the vital importance of this group in the binding of sartans and bisartans to the ACE2/Spike complex. The in silico data predicting an interaction of tetrazole-containing sartans with ACE2 were experimentally validated by the results of surface plasmon resonance (SPR) analyses performed with a recombinant human ACE2 protein. Full article

The ultrafast interaction of tightly focused femtosecond laser pulses with bulk dielectric media in direct laser writing (inscription) regimes is known to proceed via complex multi-scale light, plasma and material modification nanopatterns, which are challenging for exploration owing to their mesoscopic, transient and buried character. In this study, we report on the first experimental demonstration, analysis and modeling of hierarchical multi-period coupled longitudinal and transverse nanogratings in bulk lithium niobate inscribed in the focal region by 1030 nm, 300 fs laser pulses in the recently proposed sub-filamentary laser inscription regime. The longitudinal Bragg-like topography nanogratings, possessing the laser-intensity-dependent periods ≈ 400 nm, consist of transverse birefringent nanogratings, which are perpendicular to the laser polarization and exhibit much smaller periods ≈ 160 nm. Our analysis and modeling support the photonic origin of the longitudinal nanogratings, appearing as prompt electromagnetic and corresponding ionization standing waves in the pre-focal region due to interference of the incident and plasma-reflected laser pulse parts. The transverse nanogratings could be assigned to the nanoscale material modification by interfacial plasmons, excited and interfered in the resulting longitudinal array of the plasma sheets in the bulk dielectric material. Our experimental findings provide strong support for our previously proposed mechanism of such hierarchical laser nanopatterning in bulk dielectrics, giving important insights into its crucial parameters and opening the way for directional harnessing of this technology. Full article