Aditya K. Dharmadhikari

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Tank-treading (TT) motion is established in optically trapped, live red blood cells (RBCs) held in shear flow and is systematically investigated under varying shear rates, temperature (affecting membrane viscosity), osmolarity (resulting in changes in RBC shape and cytoplasmic viscosity), and viscosity of the suspending medium. TT frequency is measured as a(More)
We report on optical trapping in a weakly absorbing medium, hemin, an iron-containing porphyrin that is an important component of hemoglobin. By altering the hemin concentration we are able to control the amount of optical energy that is absorbed; changing the hemin concentration from <12 mg/ml to >45 mg/ml enables the onset of thermal trapping to be(More)
We demonstrate rotation of live Chlamydomonas reinhardtii cells in an optical trap; the speed and direction of rotation are amenable to control by varying the optical trapping force. Cells rotate with a frequency of 60-100 rpm; functional flagella are shown to play a decisive role in rotation. The rotating cells generate torque (typically ~7500-12000 pN nm)(More)
A modified optical tweezers set-up has been used to generate microbubbles in flowing, biologically relevant fluids and human whole blood that contains carbon nanotubes (CNTs) using low power (< or =5 mW), infrared (1064 nm wavelength), continuous wave laser light. Temperature driven effects at the tweezers' focal point help to optically trap these(More)
We demonstrate a high-contrast interference fringe pattern formed by amplified spontaneous emission (ASE) in a noncollinear two-beam self-diffraction setup by use of dyes. In the presence of a transient grating a stable interference pattern is observed in ASE induced by one- and two-photon absorption. The fringe visibility varies from 0.2 to 0.65 with a(More)
We have used optical tweezers to trap normal and Plasmodiuminfected red blood cells (iRBCs). Two different facets of the behavior of RBCs in infrared light fields emerge from our experiments. Firstly, while the optical field modifies both types of RBCs in the same fashion, by folding the original biconcave disk into a rod-like shape, iRBCs rotate with(More)
A laser-based method has been developed for experimentally probing single red blood cell (RBC) buckling and determining RBC membrane rigidity. Our method combines a liquid flow cell, fluorescence microscopy, and an optical-trap to facilitate simple measurements of the shear modulus and buckling properties of single RBCs, under physiological conditions. The(More)
We investigate the physics of an optically driven micromotor of biological origin. When a single, live red blood cell (RBC) is placed in an optical trap, the normal biconcave disc shape of the cell is observed to fold into a rod-like shape. If the trapping laser beam is circularly polarized, the folded RBC rotates. A model based on geometric considerations,(More)
H atoms in H(2)O are rearranged by strong optical fields generated by intense 9.3 fs laser pulses to form H(2)(+). This atomic rearrangement is ultrafast: It occurs within a single laser pulse. Quantum-chemical calculations reveal that H(2)(+) originates in the (1)A state of H(2)O(2+) when the O-H bond elongates to 1.15 a.u. and the H-O-H angle becomes 120(More)
A time-dependent bond-hardening process is discovered in a polyatomic molecule (tetramethyl silane, TMS) using few-cycle pulses of intense 800 nm light. In conventional mass spectrometry, symmetrical molecules such as TMS do not exhibit a prominent molecular ion (TMS(+)) as unimolecular dissociation into [Si(CH(3))(3)](+) proceeds very fast. Under a strong(More)