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Creators/Authors contains: "Ahmed, H."

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  1. Abstract

    Recent advances in wavefront shaping have enabled complex classes of Structured Light which carry spin and orbital angular momentum, offering new tools for light-matter interaction, communications, and imaging. Controlling both components of angular momentum along the propagation direction can potentially extend such applications to 3D. However, beams of this kind have previously been realized using bench-top setups, requiring multiple interaction with light of a fixed input polarization, thus impeding their widespread applications. Here, we introduce two classes of metasurfaces that lift these constraints, namely: i) polarization-switchable plates that couple any pair of orthogonal polarizations to two vortices in whichmore »the magnitude and/or sense of vorticity vary locally with propagation, and ii) versatile plates that can structure both components of angular momentum, spin and orbital, independently, along the optical path while operating on incident light of any polarization. Compact and integrated devices of this type can advance light-matter interaction and imaging and may enable applications that are not accessible via other wavefront shaping tools.

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  2. Abstract

    Optical phase singularities are zeros of a scalar light field. The most systematically studied class of singular fields is vortices: beams with helical wavefronts and a linear (1D) singularity along the optical axis. Beyond these common and stable 1D topologies, we show that a broader family of zero-dimensional (point) and two-dimensional (sheet) singularities can be engineered. We realize sheet singularities by maximizing the field phase gradient at the desired positions. These sheets, owning to their precise alignment requirements, would otherwise only be observed in rare scenarios with high symmetry. Furthermore, by applying an analogous procedure to the full vectorialmore »electric field, we can engineer paraxial transverse polarization singularity sheets. As validation, we experimentally realize phase and polarization singularity sheets with heart-shaped cross-sections using metasurfaces. Singularity engineering of the dark enables new degrees of freedom for light-matter interaction and can inspire similar field topologies beyond optics, from electron beams to acoustics.

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  3. Background: Estrogen Receptors (ER) are members of the nuclear intracellular receptorsfamily. ER once activated by estrogen, it binds to DNA via translocating into the nucleus and regulatesthe activity of various genes. Withaferin A (WA) - an active compound of a medicinal plant Withaniasomnifera was reported to be a very effective anti-cancer agent and some of the recent studies hasdemonstrated that WA is capable of arresting the development of breast cancer via targeting estrogenreceptor. Objective: The present study is aimed at understanding the molecular level interactions of ER and Tamoxifenin comparison to Withaferin A using In-silico approaches with emphasis on Withaferinmore »Abinding capability with ER in presence of point mutations which are causing de novo drug resistance toexisting drugs like Tamoxifen. Methods: Molecular modeling and docking studies were performed for the Tamoxifen and WithaferinA with the Estrogen receptor. Molecular docking simulations of estrogen receptor in complex withTamoxifen and Withaferin A were also performed. Results: Amino acid residues, Glu353, Arg394 and Leu387 was observed as crucial for binding andstabilizing the protein-ligand complex in case of Tamoxifen and Withaferin-A. The potential ofWithaferin A to overcome the drug resistance caused by the mutations in estrogen receptor to the existingdrugs such as Tamoxifen was demonstrated. Conclusion: In-silico analysis has elucidated the binding mode and molecular level interactions whichare expected to be of great help in further optimizing Withaferin A or design / discovery of futurebreast cancer inhibitors targeting estrogen receptor.« less