Alexander S. Dvornikov

University of California, Irvine, Irvine, California, United States

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Publications (84)140.37 Total impact

  • A. S. DVORNIKOV, J. MALKIN, P. M. RENTZEPIS
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 11/2010; 25(48).
  • Yongchao Liang, A. S. Dvornikov, P. M. Rentzepis
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 02/2010; 31(8).
  • A S Dvornikov, E P Walker, P M Rentzepis
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    ABSTRACT: We describe the design and construction of ultrahigh capacity three-dimensional, 3D, optical storage devices that operate by two-photon absorption. The molecular systems and their properties that are used as two photon media for writing and one photon for accessing the stored information within the volume of the device are presented in some detail and the nonlinear two-photon absorption mechanism is briefly visited. The optical system and its components, which facilitated writing and reading, are also described and the bit density, bit error rate, store and access speeds, cycle times, and stability of the materials under various experimental conditions are also topics addressed in this review. The first ever storage of terabyte data in a removable storage disk is described in detail.
    The Journal of Physical Chemistry A 10/2009; 113(49):13633-44. · 2.77 Impact Factor
  • Jie Chen, Alexander S Dvornikov, Peter M Rentzepis
    The Journal of Physical Chemistry A 08/2009; 113(30):8818-9; discussion 8820-2. · 2.77 Impact Factor
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    A.S. Dvornikov, H. Zhang, P.M. Rentzepis
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    ABSTRACT: A new dye precursor (DP) molecule was synthesized and its photochromic, spectroscopic and kinetic properties were determined. This dye precursor yields the strongly fluorescent Rhodamine 700 dye when it is exposed to UV light. The ability to form a highly fluorescent dye was utilized in the fabrication of two-photon volumetric optical memory materials. The spectral characteristics, kinetics and photochemistry were measured and the photoreactions mechanism is proposed.
    Journal of Photochemistry and Photobiology A Chemistry 01/2009; 201(1):57-61. · 2.29 Impact Factor
  • Ed Walker, Alexander Dvornikov, Ken Coblentz, Peter Rentzepis
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    ABSTRACT: 1 Tbyte of data has been recorded in 200 layers inside the volume of one of our two-photon 3D disks. Each layer contains 5 Gb of data similar to the capacity of a single layer DVD. The results obtained with our high-performance 1.0 numerical aperture (NA) objective lens show a full disk recording of 1 Tbyte within a standard optical disk form factor 120 mm x 1.2 mm thick utilizing our very stable and efficient materials. Very high sensitivity materials are recorded with bit energies as low as 250 pJ/bit. Materials sensitive at 405 nm are experimentally tested by recording with a 405 nm Nichia laser diode. Results show that bit dimensions are further reduced, which enables future recordings of 5 Tbyte disk capacities by recording 25 Gb/layer, the equivalent of a Blu-ray disk capacity per layer.
    Applied Optics 09/2008; 47(22):4133-9. · 1.69 Impact Factor
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    Ed Walker, Alexander Dvornikov, Ken Coblentz, Peter Rentzepis
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    ABSTRACT: We have recorded 1TeraByte of data in 200 layers in the volume of one DVD-like two-photon 3D disks. Each layer contains 5GBytes of data, equal to single layer DVD capacity. The results obtained with our high-performance 1.0NA objective lens show a full disk recording of 1 TByte within a standard optical disk form factor of 120mm × 1.2mm thick utilizing our very stable and efficient materials. Very high sensitivity materials are used to store information with bit energies as low as 250pJ/bit. Materials sensitive at 405nm are been tested by recording with 405nm Nichia laser diodes. Results show that bit dimensions are further reduced enabling future recordings at 5TByte disk capacities by recording 25GBytes/layer, the equivalent of a Blu-ray disk capacity per layer.
    Proc SPIE 08/2008;
  • Hua Zhang, Jie Chen, Ivan V Tomov, Alexander S Dvornikov, Peter M Rentzepis
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    ABSTRACT: The photochemical redox reaction kinetics of [M(III)(C(2)O(4))(3)](3-) [M = Co, Fe] complexes have been reexamined and studied by time-resolved spectroscopy. The redox mechanisms of the two systems, Co and Fe, were found to be similar to each other, and solvated electrons were observed immediately after 266/267 nm photoexcitation. A reaction mechanism is proposed that involves photoelectron detachment as a primary process. The charge-transfer bands for both complexes, which had been attributed to ligand to metal charge-transfer (LMCT) transitions previously, are reassigned to charge transfer to solvent (CTTS) transitions.
    The Journal of Physical Chemistry A 12/2007; 111(45):11584-8. · 2.78 Impact Factor
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    ABSTRACT: 253GB have been recorded in 300 layers inside the volume of one of our two-photon 3D disks. Each layer contains the equivalent of CD layer bit-densities recorded with a 0.5NA objective lens. A new 1.0NA lens with the desirable first order optical properties of long working distance and small diameter, 1.2mm and 4.5mm, and a self-compensating spherical aberration correction mechanism is designed, manufactured and integrated into our single beam two-photon 3D automated recording system. Experimental data obtained with the 1.0NA lens are presented. The resulting bit densities obtained with our new high-performance liquid immersion singlet (LIS) objective lens indicate that our system is capable of full disk recordings from 0.5 to 1 TB within a standard optical disk form factor of 120mm x 1.2mm thick utilizing our very stable and efficient materials. A compact optical head based on our new objective lens capable of TB storage is described.
    Optics Express 10/2007; 15(19):12264-76. · 3.53 Impact Factor
  • Masaharu Akiba, Alexander S. Dvornikov, Peter M. Rentzepis
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    ABSTRACT: The synthesis and photochemical reaction mechanism of N-benzoyl oxazine derivatives have been investigated. The synthesized materials were found to be photosensitive and capable of generating oxazine dye upon light irradiation. The initial reactions were found to include homolytic bond cleavage between the oxazine nitrogen and benzoyl carbon atoms proceeding through the excited singlet state and the formation of oxazine and benzoyl radicals. Subsequent reaction steps include direct electron transfer between two oxazine radicals or disproportionation of the oxazine dimer species formed through the recombination of two oxazine radicals. These reactions lead to the formation of the oxazine dye cation and anion pair.
    Journal of Photochemistry and Photobiology A Chemistry 07/2007; · 2.29 Impact Factor
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    ABSTRACT: 253GB have been recorded in one of our two-photon 3-d disks. Experiments indicate a roadmap of full disk recordings from 0.5 to 1TB utilizing our very stable and efficient materials and new high-performance objective lens.
    Proc SPIE 05/2007;
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    ABSTRACT: An 800-nm 200-fs laser is used to produce DNA damage in rat kangaroo (PtK1) and human cystic fibrosis pancreatic adenoma carcinoma (CFPAC-1) cells. Immunofluorescence staining for DNA repair factors in irradiated cells displays localization of gammaH2AX, Nbs1, and Rad50 to the site of irradiation 3 to 30 min following laser exposure. It is concluded that the 200-fs near-infrared laser is an excellent source for the production and study of spatially defined regions of DNA damage.
    Journal of Biomedical Optics 01/2007; 12(2):020505. · 2.75 Impact Factor
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    ABSTRACT: In this study, 532-nm picosecond and 800-nm femtosecond lasers are used in combination with fluorescently labeled tubulin to further elucidate microtubule depolymerization and the effect lasers may have on the resulting depolymerization. Depolymerization rates of targeted single microtubules are dependent on location with respect to the nucleus. Microtubules located near the nucleus exhibit a significantly faster depolymerization rate when compared to microtubule depolymerization rates near the periphery of the cell. Microtubules cut with the femtosecond laser depolymerize at a slower rate than unirradiated controls (p=0.002), whereas those cut with the picosecond laser depolymerize at the same rate as unirradiated controls (p=0.704). Our results demonstrate the ability of both the picosecond and femtosecond lasers to cut individual microtubules. The differences between the two ablation results are discussed.
    Journal of Biomedical Optics 01/2007; 12(2):024022. · 2.75 Impact Factor
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    ABSTRACT: We have built a robotic laser scissors and laser tweezers microscope ("RoboLase") that can be operated via the Internet. The system can be used to image, ablate, and/or trap cells and their organelles by remote-control. In the ablation mode, RoboLase is being used to perform delicate microsurgery on mitotic organelles (individual microtubules, spindle fibers, and centrioles). In the trapping mode, the system is being used as a real-time automatic tracking and trapping system (RATTS) of fast moving cells. RATTS performs all tracking and trapping functions without human intervention and has been used remotely between Australia and the US.
    Circuits, Systems and Computers, 1977. Conference Record. 1977 11th Asilomar Conference on 01/2006;
  • Masaharu Akiba, Alexander Dvornikov, Peter M. Rentzepis
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    ABSTRACT: The synthesis and photochemical reaction of N-benzoyl oxazines was investigated. The materials were found to be photosensitive and capable of generating oxazine dye upon light irradiation. The early step of the reaction may include homolytical bond cleavage between the oxazine nitrogen and benzoyl carbon atoms via an excited singlet state and formation of oxazine and benzoyl radicals. Subsequent reaction steps include disproportionation of the oxazine dimer species formed through recombination of two oxazine radicals, which led to the formation of oxazine dye cation and oxazine anion pair. At the present time direct electron transfer between two oxazine radicals cannot be excluded. These molecules are potential media for optical storage and other applications.
    01/2006;
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    ABSTRACT: We have employed new molecular media for volumetric data storage by means of two photon absorption. The optical and spectroscopic characteristics of the materials that are relevant to volumetric optical storage are described. In addition, fatigue characteristics of the photochromic media and substrates used in the fabrication of the storage devices are presented. These include temperature, read/write/erase cycles and space environments such as heavy ion and proton radiation, and heat under vacuum.
    Proc SPIE 01/2006;
  • Hua Zhang, A S Dvornikov, P M Rentzepis
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    ABSTRACT: In this paper we describe the mechanism of the photodissociation of CBr4 in various solvents. We have monitored and identified the intermediate species and determined the growth and decay rates of the excited states and metastable species formed during the photodissociation process by means of ultrafast time-resolved spectroscopy. On the basis of the experimental data presented in this paper, the observed transient spectra and species have been assigned to the stabilized solvated ion pair (CBr3+//Br-)solv.
    The Journal of Physical Chemistry A 08/2005; 109(27):5984-8. · 2.78 Impact Factor
  • Alexander Dvornikov, Yongchao Liang, Peter Rentzepis
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    ABSTRACT: The spectroscopic properties, transient spectra and kinetics of a composite molecule are described. This molecule consists of a photochromic moiety chemically bonded to a strongly fluorescing dye. Experimental data presented here show that this composite molecule performs as an erasable, re-writable molecular optical storage medium with non-destructive read-out. The dependence of the fluorescence efficiency on the structure of the photochromic group and viscosity is discussed.
    Journal of Materials Chemistry 01/2005; 15(10). · 6.63 Impact Factor
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    ABSTRACT: The spectroscopic properties, ultrafast kinetics and utilization of a photochromic molecule as a bi-stable fluorescing sensor of polarity in live cells are described. This molecule is a photochromic fulgimide, 2,3-dialkylidenesuccinimide, which emits fluorescence that can be switched optically on and off. The fluorescence intensity is a function of the polarity of the molecular environment, namely it fluoresces strongly when the molecule is in its polar isomeric structure form. We demonstrate that this molecule enters live cells without inducing damage, it binds primarily to internal membranous organelles (mitochondria) and its fluorescence can be switched optically "on" and "off" repeatedly while inside the living cell. A possible use as a bi-stable, on/off sensor is discussed.
    Journal of Photochemistry and Photobiology B Biology 08/2004; 75(1-2):51-6. · 2.80 Impact Factor
  • A. S. Dvornikov, Y. C. Liang, P. M. Rentzepis
    Research on Chemical Intermediates 06/2004; 30(4):545-561. · 1.54 Impact Factor