The preparation of fluorescence-quenched probes for use in the characterization of human factor Xa substrate binding domains

The preparation and characterization by LCMS of a library of 55 fluorescence- quenched peptides is described. The peptides bear a terminal anthranilamide fluorophore and a penultimate 2,4-dinitrophenyl-L-lysine quencher, and will be used to probe the substrate binding domain of the human blood coagulation enzyme, factor Xa.     

Comments on limits of space-times

A coordinate-dependent investigation of limits of space-times is given. Different kinds of limits are found and analyzed. A criterion selecting limits which appear to be nothing but technical tricks is proposed. Finally, a method for generating new limits from a given family of metrics is examined.This work was carried out under the auspices of the National Group for Mathematical Physics of C.N.R.     

Boundedness of solutions for anisotropic degenerate elliptic equations with nonstandard growth

Under nonstandard growth conditions, following Moser's iteration technique, we prove boundedness of solutions for fourth order nonlinear elliptic equation in divergence form.     

Working group report: Heavy-ion physics and quark-gluon plasma

This is the report of Heavy Ion Physics and Quark-Gluon Plasma at WHEPP-09 which was part of Working Group-4. Discussion and work on some aspects of quark-gluon plasma believed to have created in heavy-ion collisions and in early Universe are reported.     

The Structure of the Elusive Urease–Urea Complex Unveils the Mechanism of a Paradigmatic Nickel‐Dependent Enzyme

Urease, the most efficient enzyme known, contains an essential dinuclear Ni^II cluster in the active site. It catalyzes the hydrolysis of urea, inducing a rapid pH increase that has negative effects on human health and agriculture. Thus, the control of urease activity is of utmost importance in medical, pharmaceutical, and agro‐environmental applications. All known urease inhibitors are either toxic or inefficient. The development of new and efficient chemicals able to inhibit urease relies on the knowledge of all steps of the catalytic mechanism. The short (microseconds) lifetime of the urease–urea complex has hampered the determination of its structure. The present study uses fluoride to substitute the hydroxide acting as the co‐substrate in the reaction, preventing the occurrence of the catalytic steps that follow substrate binding. The 1.42 Å crystal structure of the urease–urea complex, reported here, resolves the enduring debate on the mechanism of this metalloenzyme.     

Optical-damage-free guided second-harmonic generation in 1% MgO-doped stoichiometric lithium tantalate

Room-temperature cw second-harmonic generation from telecom wavelengths, with 30% W(-1) cm(-2) efficiency and second-harmonic power levels up to 41 mW, was achieved in buried waveguides fabricated by reverse-proton exchange in 1% MgO-doped stoichiometric lithium tantalate without any evidence of optical damage. The technology proves suitable for the realization of efficient nonlinear frequency converters and all-optical devices.     

On generalized torsion two-forms in general relativity: a result of null tetrad formalism

The method of reduction of a connection form from a principal fibre-bundle to a sub-bundle is studied by considering the null tetrad formalism in space-time and discussing in detail the resulting Generalized Maurer-Cartan Structural Equations. Vacuum space-times satisfying Einstein field equations and admitting the vanishing of the induced curvature form in the reduced bundle are investigated. It is shown that these hypotheses imply the existence of a field surface orthogonal to a real null geodesic vector of the tetrad field. This work was carried out under the auspices of the National Group of Mathematical Physics of CNR.     

Visualization of coherent destruction of tunneling in an optical double well system

We report on a direct visualization of coherent destruction of tunneling (CDT) of light waves in a double well system which provides an optical analog of quantum CDT as originally proposed by Grossmann, Dittrich, Jung, and H?nggi [Phys. Rev. Lett. 67, 516 (1991)10.1103/PhysRevLett.67.516]. The driven double well, realized by two periodically curved waveguides in an Er:Yb-doped glass, is designed so that spatial light propagation exactly mimics the coherent space-time dynamics of matter waves in a driven double well potential governed by the Schr?dinger equation. The fluorescence of Er ions is exploited to image the spatial evolution of light in the two wells, clearly demonstrating suppression of light tunneling for special ratios between the frequency and amplitude of the driving field.     

Non-Archimedean Analogues of Orthogonal and Symmetric Operators and p-adic Quantization

We study orthogonal and symmetric operators in non-Archimedean Hilbert spaces in the connection with p-adic quantization. This quantization describes measurements with finite precision. Symmetric (bounded) operators in the p-adic Hilbert spaces represent physical observables. We study spectral properties of one of the most important quantum operators, namely, the operator of the position (which is represented in the p-adic Hilbert L₂-space with respect to the p-adic Gaussian measure). Orthogonal isometric isomorphisms of p-adic Hilbert spaces preserve precisions of measurements. We study properties of orthogonal operators. It is proved that each orthogonal operator in the non-Archimedean Hilbert space is continuous. However, there exist discontinuous operators with the dense domain of definition which preserve the inner product. There also exist nonisometric orthogonal operators. We describe some classes of orthogonal isometric operators and we study some general questions of the theory of non-Archimedean Hilbert spaces (in particular, general connections between topology, norm and inner product).