Garry Berkovic | Technology(Iraq) - Academia.edu (original) (raw)

Papers by Garry Berkovic

Journal of the Optical Society of America B, 1989

$Research paper thumbnail of Multiple-Fiber and Multiple-Wavelength Confocal Sensing With Diffractive Optical Elements$

Adding a diffractive element to the imaging optics of a fiber-based confocal sensor greatly enhan... more Adding a diffractive element to the imaging optics of a fiber-based confocal sensor greatly enhances the chromatic dispersion of the optics. This can be exploited to enhance the sensing range and resolution of the sensor. Several examples are given using one and two fibers with simultaneous dual wavelength illumination to probe the displacement of a target object.

The Journal of Chemical Physics, 1986

Optical second harmonic generation has been used to study the polymerization of a monolayer of vi... more Optical second harmonic generation has been used to study the polymerization of a monolayer of vinyl stearate or octadecyl methacrylate spread at the air/water interface. Rapid polymerization occurred when monolayers were irradiated with ultraviolet light, while some slower polymerization occurred when certain redox initiators were added to the water subphase. Information regarding polymerization kinetics and the orientation of molecules at the interface were also obtained using this method.

Molecular Crystals and Liquid Crystals, 1994

A new mechanism for inducing bulk asymmetry and second order optical nonlinearity in polymer-dye ... more A new mechanism for inducing bulk asymmetry and second order optical nonlinearity in polymer-dye systems is described. An anisotropic distribution of charges is established inside the medium resulting from the application of high voltage via an asymmetric electrode structure. The nonlinearity induced via this mechanism is perpendicular to the externally applied electric field. It is proven that the nonlinearity induced

The Journal of Physical Chemistry, 1991

ABSTRACT Silver metal liquidlike films (MELLFs) exhibit second harmonic generation signals (SHG) ... more ABSTRACT Silver metal liquidlike films (MELLFs) exhibit second harmonic generation signals (SHG) that are clearly different from those produced by smooth silver films or those given by electrochemically roughened silver surfaces. These differences are consistent with the interfacial colloidal model proposed for the MELLFs. The polarization and enhancement of the SHG signals are rationalized quantitatively in a model consisting of noninteracting silver particles. The results show that the particles are very nearly spherical. Trends in the results can be possibly explained by small eccentricities that vary slightly in the various MELLF preparations. We also find the volume fraction of the silver cores at the uppermost layer of the film to be 6-21%. The time dependence of the SHG revealed a curing process, on the time scale of several hours, that is attributed to diffusional rearrangements of the silver particles within the film.

Macromolecules, 1990

... 1984,88,6448. (13) Shvartsman, F. P.; Cabrera, I. R.; Weis, AL; Wachtel, E. J.; (14) Hsiung, ... more ... 1984,88,6448. (13) Shvartsman, F. P.; Cabrera, I. R.; Weis, AL; Wachtel, E. J.; (14) Hsiung, H.; Rasing, Th.; Shen, Y. R.; Shvartsman, F. P.; Cabrera, (15) Yitzchaik, S.; Berkovic, G.; Krongauz, V. Adu. Mater. ... 1986, 22, 460. Shlomo Yitzchaik, Garry Berkovic,. and Valeri Krongauz' ...

Advanced Materials, 1990

tropic environment even without a poling field, and that applying an electric field causes macros... more tropic environment even without a poling field, and that applying an electric field causes macroscopic alignment of LC domains.

Synthetic Metals, 2000

The second order nonlinearity (β) of a series of organic π-conjugated molecules involving 1,3 ind... more The second order nonlinearity (β) of a series of organic π-conjugated molecules involving 1,3 indandione derivatives as an acceptor moiety has been measured. The effect of varying the donor from dialkylamino to N-carbazolyl substituents was examined. Despite the chemically similar nature of the two donors, a drastic reduction of electric field induced second harmonic (EFISH) β values for the molecules involving the N-carbazolyl substituents was detected. Quantum mechanical calculations indicate that the decrease in β values results from the presence of two overlapping transitions that contribute to β with opposite signs. Thus, the charge transfer band gives a positive βzzz contribution along the long molecular axis, while a transition essentially within the carbazole group provides a negative βzxx contribution to βEFISH. Therefore, these molecules can only be described with a two-dimensional model as opposed to the ‘classical’ one-dimensional model for NLO chromophores. Experimental verification of this hypothesis was provided by a combination of two experimental methods, EFISH and hyper Rayleigh scattering (HRS). Each technique probes a different combination of the β tensor elements, so we could deduce the two contributions.

European Journal of Organic Chemistry, 2001

Electron donor−π−acceptor chromophores 5, 9, 11, 18−20, 21, 22, 27, 28a, 28c, 31, 32, 34−36, 38a−... more Electron donor−π−acceptor chromophores 5, 9, 11, 18−20, 21, 22, 27, 28a, 28c, 31, 32, 34−36, 38a−c, 41a, 41c, and 42 have been synthesised. The donor units are 1,3-dithiole and ferrocene; conjugated ethylenic, phenyl, phenylenevinylene, thienyl, bithienyl, terthienyl, or thienylenevinylene linkers act as a central π-electron relay unit, and dicyanomethylene and polynitrofluorene groups as the acceptor unit. The electronic absorption spectra display a broad low-energy intramolecular charge transfer band in the visible region (500−700 nm) the energy (hν ICT ഠ 1.7−2.5 eV) and intensity (ε ഠ 5000−50000 m −1 cm −1 ) of which depend substantially on the nature of both D and A moieties and on the structure of the linker unit. Nonlinear optical properties have been evaluated using the EFISH technique: the highest µβ values are observed for 38b [(900±300)×10 −48 esu] and 42 [ ‡] See ref. [1] [a]

Journal of Physical Chemistry B, 2001

... Khodorkovsky,* Lev Shapiro, Jacob T. Klug, Efim Kovalev, Guilia Meshulam, § Garry Ber... more ... Khodorkovsky,* Lev Shapiro, Jacob T. Klug, Efim Kovalev, Guilia Meshulam, § Garry Berkovic, § Zvi Kotler, § and Shlomo Efrima* . ... (3) Blanchard-Desce, M.; Alain, V.; Bedworth, PV;Marder, SR; Fort, A.; Runser, C.; Barzoukas, M.; Lebus, S.; Wortmann, R. Chem. Eur. ...

Bioelectromagnetics, 2002

A new form of biomineralization has been studied in the pineal gland of the human brain. It consi... more A new form of biomineralization has been studied in the pineal gland of the human brain. It consists of small crystals that are less than 20 μm in length and that are completely distinct from the often observed mulberry-type hydroxyapatite concretions. A special procedure was developed for isolation of the crystals from the organic matter in the pineal gland. Cubic, hexagonal, and cylindrical morphologies have been identified using scanning electron microscopy. The crystal edges were sharp whereas their surfaces were very rough. Energy dispersive spectroscopy showed that the crystals contained only the elements calcium, carbon, and oxygen. Selected area electron diffraction and near infrared Raman spectroscopy established that the crystals were calcite. With the exception of the otoconia structure of the inner ear, this is the only known nonpathological occurrence of calcite in the human body. The calcite microcrystals are probably responsible for the previously observed second harmonic generation in pineal tissue sections. The complex texture structure of the microcrystals may lead to crystallographic symmetry breaking and possible piezoelectricity, as is the case with otoconia. It is believed that the presence of two different crystalline compounds in the pineal gland is biologically significant, suggesting two entirely different mechanisms of formation and biological functions. Studies directed toward the elucidation of the formation and functions, and possible nonthermal interaction with external electromagnetic fields are currently in progress. Bioelectromagnetics 23:488–495, 2002. © 2002 Wiley-Liss, Inc.

Chemical Reviews, 2000

... 2. Photochromic Liquid Crystal Polymers (PLCPs). While the combination of photochromic and me... more ... 2. Photochromic Liquid Crystal Polymers (PLCPs). While the combination of photochromic and mesogenic groups in one low molar mass molecule seldom gives photochromic liquid crystals, the synthesis of side-chain liquid ...