Browsing by Author "Ivanova, EP"

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    Femtosecond laser fabrication of diffractive optics for spatial and spectral imaging at synchrotron infrared beamlines
    (Society of Photo-Optical Instrumentation Engineers (SPIE), 2021-03-06) Anand, V; Katkus, T; Ng, SH; Vongsvivut, JP; Maksimovic, J; Klein, AR; Bambery, KR; Lundgaard, S; Linklater, D; Ivanova, EP; Tobin, MJ; Juodkazis, S
    Infrared (IR) microspectroscopy is a powerful molecular fingerprinting tool widely used for the identification of structural and functional composition of biological and chemical samples. The IR microspectroscopy beamline at the Australian Synchrotron can be operated either with a single-point narrow-band mercury cadmium telluride (MCT) detector or a focal plane array (FPA) imaging detector with 64 × 64 pixels. For the implementation of indirect nonscanning imaging technology, the system was operated with the FPA detector. In this study, we propose an indirect IR imaging technique based on the principles of correlation optics using diffractive optical elements such as random pinhole array (RPA) and Fresnel zone plate (FZP). The spatial and spectral variations of point spread functions (PSFs) of the RPA and FZP were simulated for the synchrotron configuration. Intensity responses for 2D objects were simulated using the same simulation conditions and reconstructed using Lucy-Richardson algorithm. Fabrication of diffractive elements for IR wavelengths is often a challenging task as the IR transparent material substrates, such as barium fluoride and calcium fluoride, are highly susceptible to thermal shocks and brittle by nature. The diffractive elements were fabricated by ablating directly on a 100 nm thick gold coated substrate using femtosecond laser pulses. The simulation results and the fabrication outcomes demonstrate the feasibility of indirect imaging at the synchrotron IR beamline. © 2021 Society of Photo-Optical Instrumentation Engineers (SPIE)
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    Growth response of Escherichia coli bacterial cells on exposure to 1.25 Wm-2 synchrotron-sourced Terahertz radiation
    (Institute of Electrical and Electronics Engineers (IEEE), 2023-09-19) Vilagosh, Z; Nguyen, THPP; Perera, PGT; Linklater, D; Appadoo, D; Vingsvivut, JP; Tobin, MJ; Croft, R; Ivanova, EP
    The growth of E. coli cells following low intensity 1.25 Wm−2 broadband synchrotron-sourced Terahertz (THz) radiation was monitored following serial exposures for 60 minutes with distinct samples at 10-minute intervals. After 20 minutes, E. coli cells showed a reduction to 53% compared to the control, and a minor fluctuation in colony forming units density followed by a major recovery to 80% at 60 minutes. © 2023 IEEE.
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    Intrinsic microtubule GTP-cap dynamics in semi-confined systems: kinetochore–microtubule interface
    (Springer Nature, 2012-10-18) Buljan, VA; Holsinger, RMD; Hambly, BD; Banati, RB; Ivanova, EP
    In order to quantify the intrinsic dynamics associated with the tip of a GTP-cap under semi-confined conditions, such as those within a neuronal cone and at a kinetochore–microtubule interface, we propose a novel quantitative concept of critical nano local GTP-tubulin concentration (CNLC). A simulation of a rate constant of GTP-tubulin hydrolysis, under varying conditions based on this concept, generates results in the range of 0-420 s−1. These results are in agreement with published experimental data, validating our model. The major outcome of this model is the prediction of 11 random and distinct outbursts of GTP hydrolysis per single layer of a GTP-cap. GTP hydrolysis is accompanied by an energy release and the formation of discrete expanding zones, built by less-stable, skewed GDP-tubulin subunits. We suggest that the front of these expanding zones within the walls of the microtubule represent soliton-like movements of local deformation triggered by energy released from an outburst of hydrolysis. We propose that these solitons might be helpful in addressing a long-standing question relating to the mechanism underlying how GTP-tubulin hydrolysis controls dynamic instability. This result strongly supports the prediction that large conformational movements in tubulin subunits, termed dynamic transitions, occur as a result of the conversion of chemical energy that is triggered by GTP hydrolysis (Satarić et al., Electromagn Biol Med 24:255–264, 2005). Although simple, the concept of CNLC enables the formulation of a rationale to explain the intrinsic nature of the “push-and-pull” mechanism associated with a kinetochore–microtubule complex. In addition, the capacity of the microtubule wall to produce and mediate localized spatio-temporal excitations, i.e., soliton-like bursts of energy coupled with an abundance of microtubules in dendritic spines supports the hypothesis that microtubule dynamics may underlie neural information processing including neurocomputation. © 2012, Springer Nature