Methanesulfonyl Fluoride: A Probe of Substrate Interactions in the Catalytic Site of Acetylcholinesterase

Methanesulfonyl fluoride, which reacts at the catalytic S!ite of acetylcholinesterase causing inactivation, is a useful probe of substrate binding. This is because molecules absorbed in or near the active center appear to protect the enzyme only if, by interacting strongly with the esteratic s.ite, they physically obstruct its approach. Its reaction is not disturbed by non-specific adsorption of these molecules in regions adjoining the active center, and ~s comparatively insensitive to conditions that reversibly denature the enzyme. The binding of three classes of substrates is discussed: acetylcholine analogs, phenyl esters, and indophenyl acetate. Acetylcholine fits into an active center crevice and covers both the anionic and esteratic sites, but bulkier analogs, which cannot fully penetrate, are held primarily at the anionic site and adjoining non-polar regions, with weak and intermittent attraction to the esteratic site. Phenyl esters are bound within the crevice, over the esteratic site. Indophenyl acetate is adsorbed on the margin of the active center, covering neither the anionic nor esteratic site

Discovery of Bragg confined hybrid modes with high Q-factor in a hollow dielectric resonator

The authors report on observation of Bragg confined mode in a hollow cylindrical dielectric cavity. A resonance was observed at 13.4 $GHz$ with an unloaded Q-factor of order $2\times10^5$, which is more than a factor of 6 above the dielectric loss limit. Previously such modes have only been realized from pure Transverse Electric modes with no azimuthal variations and only the $E_{\phi}$ component. From rigorous numeric simulations it is shown that the mode is a hybrid mode with non-zero azimuthal variations and with dominant $E_r$ and $E_{\phi}$ electric field components and $H_z$ magnetic field component.Comment: Accepted to be published in Applied Physics Letter

On a Order Reduction Theorem in the Lagrangian Formalism

We provide a new proof of a important theorem in the Lagrangian formalism about necessary and sufficient conditions for a second-order variational system of equations to follow from a first-order Lagrangian.Comment: 9 pages, LATEX, no figures; appear in Il Nuovo Cimento

Precise microwave characterization of MgO substrates for HTS circuits with superconducting post dielectric resonator

Accurate data of complex permittivity of dielectric substrates are needed for efficient design of HTS microwave planar circuits. We have tested MgO substrates from three different manufacturing batches using a dielectric resonator with superconducting parts recently developed for precise microwave characterization of laminar dielectrics at cryogenic temperatures. The measurement fixture has been fabricated using a SrLaAlO3 post dielectric resonator with DyBa2Cu3O7 end plates and silver-plated copper sidewalls to achieve the resolution of loss tangent measurements of 2 {\times} 10-6. The tested MgO substrates exhibited the average relative permittivity of 9.63 and tan {\delta} from 3.7 {\times} 10-7 to 2 {\times} 10-5 at frequency of 10.5 GHz in the temperature range from 14 to 80 K.Comment: 6 pages, 8 figures, 3 table

Gauge Formalism for General Relativity and Fermionic Matter

A new formalism for spinors on curved spaces is developed in the framework of variational calculus on fibre bundles. The theory has the same structure of a gauge theory and describes the interaction between the gravitational field and spinors. An appropriate gauge structure is also given to General Relativity, replacing the metric field with spin frames. Finally, conserved quantities and superpotentials are calculated under a general covariant form.Comment: 18 pages, Plain TEX, revision, explicit expression for superpotential has been adde

Nonlinear optical properties of thiazolidinone derivatives

Thiazolidinone derivatives were synthesized and their physicochemical properties are determined by absorption, H NMR spectroscopies. The third order nonlinear optical properties of thiazolidinone containing compounds were investigated in solutions using degenerate four wave mixing (DFWM) method at 532 nm

Nonlinear Optical Properties of Functionalized DNA-CTMA complexes

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High reflector absorptance measurements by the surface thermal lensing technique

Surface thermal lensing is an alternate configuration of a photothermal deflection system that was used to measure low levels of optical absorption. The thermal lensing configuration facilitated the alignment of the pump and probe laser beams by using a larger diameter probe beam. This technique was applied to high performance optical coatings, specifically high reflectors at 511 nm, zero degrees angle of incidence. The absorptance of these coatings was previously measured using a high power copper vapor laser system. A high power copper laser beam is focused onto a -2 mm diameter spot. A thermal camera senses the temperature rise with respect to the rest of the coating. The temperature change, power density and beam diameter were used with an empirical formula that yields optical absorption. The surface thermal lensing technique was able to resolve absorption levels lower than that achieved with the copper laser method