Crystallization of Arthrobacter sp. strain 1C N-(1-D-carboxyethyl)-L-norvaline dehydrogenase and its complex with NAD+

The novel NAD+-linked opine dehydrogenase from a soil isolate Arthrobacter sp. strain 1C belongs to an enzyme superfamily whose members exhibit quite diverse substrate specificites. Crystals of this opine dehydrogenase, obtained in the presence or absence of co-factor and substrates, have been shown to diffract to beyond 1.8 ? resolution. X-ray precession photographs have established that the crystals belong to space group P21212, with cell parameters a = 104.9, b = 80.0, c = 45.5 ? and a single subunit in the asymmetric unit. The elucidation of the three-dimensional structure of this enzyme will provide a structural framework for this novel class of dehydrogenases to enable a comparison to be made with other enzyme families and also as the basis for mutagenesis experiments directed towards the production of natural and synthetic opine-type compounds containing two chiral centres.     

The Foundations of Linear Stochastic Electrodynamics

An analysis is briefly presented of the possible causes of the failure of stochastic electrodynamics (SED) when applied to systems with nonlinear forces, on the basis that the main principles of the theory are correct. In light of this analysis, an alternative approach to the theory is discussed, whose postulates allow to establish contact with quantum mechanics in a natural way. The ensuing theory, linear SED, confirms the essential role of the vacuum–particle interaction as the source of quantum phenomena.     

New perturbative derivation of the Fokker-planck equation for coloured multiplicative noise

Starting from a stochastic differential equation with coloured, multiplicative noise with a finite correlation time, a perturbative treatment of the phase-space density to second order leads in a straightforward way to the generalized Fokker-Plank equation.     

Strong entanglement criterion involving momentum weak values

In recent years weak values have been used to explore interesting quantum features in novel ways. In particular, the real part of the weak value of the momentum operator has been widely studied, mainly in connection with Bohmian trajectories. Here we focus on the imaginary part and its role in relation with the entanglement of a bipartite system. We establish an entanglement criterion based on weak momentum correlations, that allows to discern whether the entanglement is encoded in the amplitude and/or in the phase of the wave function. Our results throw light on the physical role of the real and imaginary parts of the weak values, and stress the relevance of the latter in the multi-particle scenario.     

Estimate of Planck's Constant from an Electromagnetic Mach Principle

An electromagnetic Mach principle is introduced, considering the zero-point radiation field as being produced by all visible matter in the universe, and at the same time being responsible for the quantum fluctuations of matter. An order-of-magnitude estimate allows thus to derive a relation between Planck's constant (as a measure of the strength of the field fluctuations) and cosmological constants, which is well satisfied by the accepted values of the intervening quantities.     

Schrödinger equation derived from stochastic electrodynamics

A statistical treatment of a charged particle embedded in the zero-point radiation field leads to the Schrödinger equation including radiative terms. When the system approaches equilibrium, these terms represent the radiative corrections predicted by non-relativistic quantum electrodynamics.     

Quantum mechanics derived from stochastic electrodynamics

The connection between stochastic electrodynamics (SED) and the quantum theory of matter is further explored. The main result is that the Fokker-Planck-like equation of SED can be recast into the form of a Schrödinger equation with radiative corrections, when the system is close to a state of equilibrium. The phase-space distribution can be written as Wigner's pseudo-distribution plus corrections due to the nonlinearity of the external force and to radiative effects. The radiative corrections predicted by the theory, namely the Lamb shift and the decay of excited atomic states, coincide with those predicted by QED. Moreover, the theory offers a clear physical interpretation of these phenomena as due to the coupling of the electric dipole of the system with the zero-point radiation field and to radiation reaction, respectively.     

Stochastic treatment of the quantum-mechanical harmonic oscillator: Mass renormalization and lamb shift

By studying an oscillator coupled to the fluctuating radiation field, we obtain convergent results for the Lamb shift and for the mass renormalization even before introducing any cut-off. Once in stochastic equilibrium with the field, the oscillator obeys Schrödinger's equation.     

Intercalation of Toluidines into α-Zirconium Hydrogenphosphate

Intercalates of o-, m-, and p-toluidine into α-Zr(HPO₄)₂ · H₂O were prepared and characterized by powder X-ray diffraction, thermogravimetric analysis and infrared spectroscopy. As follows from IR, toludine molecules are protonated in the interlayer space. Toluidine molecules are arranged in a bimolecular way in the intercalates containing more than 1.5 toluidine molecules per Zr atom. On the other hand, a monolayer of the toluidine molecules is supposed in the intercalates with less than one toluidine molecule per Zr atom.