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2000


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Phenomenological damping in optical response tensors

Buckingham, A., Fischer, P.

PHYSICAL REVIEW A, 61(3), 2000 (article)

Abstract
Although perturbation theory applied to the optical response of a molecule or material system is only strictly valid far from resonances, it is often applied to ``near-resonance{''} conditions by means of complex energies incorporating damping. Inconsistent signs of the damping in optical response tensors have appeared in the recent literature, as have errors in the treatment of the perturbation by a static held. The ``equal-sign{''} convention used in a recent publication yields an unphysical material response, and Koroteev's intimation that linear electro-optical circular dichroism may exist in an optically active liquid under resonance conditions is also flawed. We show that the isotropic part of the Pockels tensor vanishes.

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DOI [BibTex]

2000


DOI [BibTex]


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Ab initio investigation of the sum-frequency hyperpolarizability of small chiral molecules

Champagne, B., Fischer, P., Buckingham, A.

CHEMICAL PHYSICS LETTERS, 331(1):83-88, 2000 (article)

Abstract
Using a sum-over-states procedure based on configuration interaction singles /6-311++G{*}{*}, we have computed the sum-frequency hyperpolarizability beta (ijk)(-3 omega; 2 omega, omega) Of two small chiral molecules, R-monofluoro-oxirane and R-(+)-propylene oxide. Excitation energies were scaled to fit experimental UV-absorption data and checked with ab initio values from time-dependent density functional theory. The isotropic part of the computed hyperpolarizabilities, beta(-3 omega; 2 omega, omega), is much smaller than that reported previously from sum-frequency generation experiments on aqueous solutions of arabinose. Comparison is made with a single-centre chiral model. (C) 2000 Elsevier Science B.V. All rights reserved.

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DOI [BibTex]

DOI [BibTex]


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Three-wave mixing in chiral liquids

Fischer, P., Wiersma, D., Righini, R., Champagne, B., Buckingham, A.

PHYSICAL REVIEW LETTERS, 85(20):4253-4256, 2000 (article)

Abstract
Second-order nonlinear optical frequency conversion in isotropic systems is only dipole allowed for sum- and difference-frequency generation in chiral media. We develop a single-center chiral model of the three-wave mixing (sum:frequency generation) nonlinearity and estimate its magnitude. We also report results from ab initio calculations and from three- and four-wave mixing experiments in support of the theoretical estimates. We show that the second-order susceptibility in chiral liquids is much smaller than previously thought.

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DOI [BibTex]

DOI [BibTex]


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Two-dimensional fine particle positioning under an optical microscope using a piezoresistive cantilever as a manipulator

Sitti, M., Hashimoto, H.

journal of Micromechatronics, 1(1):25-48, Brill, 2000 (article)

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[BibTex]


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Investigation of Virtual Reality Interface for AFM-based Nano Manipulation

Horiguchi, S., Sitti, M., Hashimoto, H.

IEEJ Transactions on Electronics, Information and Systems, 120(12):1948-1956, The Institute of Electrical Engineers of Japan, 2000 (article)

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[BibTex]

[BibTex]


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Macro to Nano Tele-Manipulation Towards Nanoelectromec hanical Systems

Sitti, M., Hashimoto, H.

Journal of Robotics and Mechatronics, 12(3):209-217, FUJI TECHNOLOGY PRESS LTD., 2000 (article)

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[BibTex]

[BibTex]


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Wing transmission for a micromechanical flying insect

Fearing, R. S., Chiang, K. H., Dickinson, M. H., Pick, D., Sitti, M., Yan, J.

In Robotics and Automation, 2000. Proceedings. ICRA’00. IEEE International Conference on, 2, pages: 1509-1516, 2000 (inproceedings)

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[BibTex]

[BibTex]


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Controlled pushing of nanoparticles: modeling and experiments

Sitti, M., Hashimoto, H.

IEEE/ASME transactions on mechatronics, 5(2):199-211, IEEE, 2000 (article)

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[BibTex]

[BibTex]

1998


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Surface second-order nonlinear optical activity

Fischer, P., Buckingham, A.

JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS, 15(12):2951-2957, 1998 (article)

Abstract
Following the recent observation of a large second-harmonic intensity difference from a monolayer of chiral molecules with left and right circularly polarized light, the scattering theory is generalized and extended to predict linear and circular intensity differences for the more Versatile sum-frequency spectroscopy. Estimates indicate that intensity differences should be detectable for a typical experimental arrangement. The second-order nonlinear surface susceptibility tensor is given for different surface point groups in the electric dipole approximation; it is shown that nonlinear optical activity phenomena unambiguously probe molecular chirality only for molecular monolayers that are symmetric about the normal. Other surface symmetries can give rise to intensity differences from monolayers composed of achiral molecules. A water surface is predicted to show Linear and nonlinear optical activity in the presence of an electric field parallel to the surface. (C) 1998 Optical Society of America {[}S0740-3224(98)01311-3] OCIS codes: 190.0190, 190.4350, 240.6490.

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DOI [BibTex]

1998


DOI [BibTex]


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Linear electro-optic effect in optically active liquids

Buckingham, A., Fischer, P.

CHEMICAL PHYSICS LETTERS, 297(3-4):239-246, 1998 (article)

Abstract
A linear effect of an electrostatic field F on the intensity of sum- and difference-frequency generation in a chiral liquid is predicted. It arises in the electric dipole approximation. The effect changes sign with the enantiomer and on reversing the direction of the electrostatic field. The sum-frequency generator chi(alpha beta gamma)((2)) (-omega(3);omega(1),omega(2)), where omega(3) = omega(1) + omega(2), and the electric field-induced sum-frequency generator chi(alpha beta gamma delta)((3))(-omega(3);omega(1),omega(2),0)F-delta interfere and their contributions to the scattering power can be distinguished. Encouraging predictions are given for a typical experimental arrangement. (C) 1998 Elsevier Science B.V. All rights reserved.

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DOI [BibTex]

DOI [BibTex]


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Monolayers of hexadecyltrimethylammonium p-tosylate at the air-water interface. 1. Sum-frequency spectroscopy

Bell, G., Li, Z., Bain, C., Fischer, P., Duffy, D.

JOURNAL OF PHYSICAL CHEMISTRY B, 102(47):9461-9472, 1998 (article)

Abstract
Sum-frequency vibrational spectroscopy has been used to determine the structure of monolayers of the cationic surfactant, hexadecyltrimethylammonium p-tosylate (C(16)TA(+)Ts(-)), at the surface of water. Selective deuteration of the cation or the anion allowed the separate detection of sum-frequency spectra of the surfactant and of counterions that are bound to the monolayer. The p-tosylate ions an oriented with their methyl groups pointing away from the aqueous subphase and with the C-2 axis tilted, on average, by 30-40 degrees from the surface normal. The vibrational spectra of C(16)TA(+) indicate that the number of gauche defects in the monolayer does not change dramatically when bromide counterions are replaced by p-tosylate. The ends of the hydrocarbon chains of C16TA+ are, however, tilted much further from the surface normal in the presence of p-tosylate than in the presence of bromide. A quantitative analysis of the sum-frequency spectra requires a knowledge of the molecular hyperpolarizability tensor: the role of ab initio calculations and Raman spectroscopy in determining the components of this tensor is discussed.

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DOI [BibTex]

DOI [BibTex]


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Ultraviolet resonance Raman study of drug binding in dihydrofolate reductase, gyrase, and catechol O-methyltransferase

Couling, V., Fischer, P., Klenerman, D., Huber, W.

BIOPHYSICAL JOURNAL, 75(2):1097-1106, 1998 (article)

Abstract
This paper presents a study of the use of ultraviolet resonance Raman (UVRR) spectroscopic methods as a means of elucidating aspects of drug-protein interactions. Some of the RR vibrational bands of the aromatic amino acids tyrosine and tryptophan are sensitive to the microenvironment, and the use of UV excitation radiation allows selective enhancement of the spectral features of the aromatic amino acids, enabling observation specifically of their change in microenvironment upon drug binding. The three drug-protein systems investigated in this study are dihydrofolate reductase with its inhibitor trimethoprim, gyrase with novobiocin, and catechol O-methyltransferase with dinitrocatechol. It is demonstrated that UVRR spectroscopy has adequate sensitivity to be a useful means of detecting drug-protein interactions in those systems for which the electronic absorption of the aromatic amino acids changes because of hydrogen bonding and/or possible dipole-dipole and dipole-polarizability interactions with the ligand.

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DOI [BibTex]

DOI [BibTex]


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Tele-nanorobotics using an atomic force microscope as a nanorobot and sensor

Sitti, M., Hashimoto, H.

Advanced Robotics, 13(4):417-436, Taylor & Francis, 1998 (article)

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[BibTex]

[BibTex]


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Nano tele-manipulation using virtual reality interface

Sitti, M., Horiguchi, S., Hashimoto, H.

In Industrial Electronics, 1998. Proceedings. ISIE’98. IEEE International Symposium on, 1, pages: 171-176, 1998 (inproceedings)

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[BibTex]

[BibTex]


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Tele-nanorobotics using atomic force microscope

Sitti, M., Hashimoto, H.

In Intelligent Robots and Systems, 1998. Proceedings., 1998 IEEE/RSJ International Conference on, 3, pages: 1739-1746, 1998 (inproceedings)

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[BibTex]

[BibTex]


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2D micro particle assembly using atomic force microscope

Sitti, M., Hirahara, K., Hashimoto, H.

In Micromechatronics and Human Science, 1998. MHS’98. Proceedings of the 1998 International Symposium on, pages: 143-148, 1998 (inproceedings)

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[BibTex]

[BibTex]


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Macro to nano tele-manipulation through nanoelectromechanical systems

Sitti, M., Hashimoto, H.

In Industrial Electronics Society, 1998. IECON’98. Proceedings of the 24th Annual Conference of the IEEE, 1, pages: 98-103, 1998 (inproceedings)

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[BibTex]

[BibTex]