Technical and practical aspects of 19F NMR‐based screening: toward sensitive high‐throughput screening with rapid deconvolution

The technical and practical aspects of ¹⁹F NMR‐based screening against a macromolecular target are analyzed in detail. A novel method utilizing the relaxation of ¹⁹F homonuclear double quantum coherence is proposed for performing NMR‐based binding assays in a direct‐ or competition‐mode format. A combined strategy based on ¹⁹F NMR chemical shift prediction, 2D ¹⁹F NMR DOSY, and 2D ¹⁹F–¹H NMR long‐range COSY experiments is presented for the deconvolution of complex mixtures of fluorinated molecules generated by either addition of single compounds or by chemical synthesis. The approaches presented here allow the screening of complex mixtures, even in the case where the exact composition is not known, and the rapid identification of the binders contained in the mixtures. Copyright © 2012 John Wiley & Sons, Ltd.     

A numerical shape finding procedure for very thin shells

The paper introduces a numerical shape-finding procedure for very thin continuous shells (thickness less than 10 cm): an assigned loading distribution is applied on a point-wise suspended membrane, which, after its deformation, is inverted to give the geometry of a reinforced concrete continuous shell. The procedure is an extension to the continuum case of previous ones introduced for gridshells. In the past it has been employed in an empirical way by several designers.The geometrically non-linear analysis of the membrane is carried out taking account of large displacements and finite rotations. Finally, the structural analysis of the shell, including stability aspects, is performed, for example, to check and control the membranal behaviour of the structure.

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Sommario Si introduce un metodo per la ricerca della forma di gusci sottili: un'assegnata distribuzione di carico è applicata a una membrana appesa per punti, che, dopo la sua deformazione, viene invertita per fornire la geometria di un guscio continuo in conglomerato cementizio armato. Il metodo è un' estensione al caso continuo di metodi precedenti introdotti per i gusci discreti. Nel passato è stato usato in modo empirico da molti progettisti.L'analisi geometricamente nonlineare della membrana viene eseguita in grandi spostamenti tenendo conto delle rotazioni finite. Infine viene eseguita l'analisi strutturale del guscio, considerando anche gli aspetti di stabilità, per verificare e controllare il comportamento membranale della struttura, che è confermato.

     

Functional analysis of integral transport equations in linear rarefied gas dynamics

Summary A study is proposed on the functional properties of the solutions of an interesting class of linear integral equations governing linear problems in rarefied gas dynamics. The analysis is carried out through a systematic study of the integral operator generated by the kernel of the equations themselves.

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Sommario In questa nota vengono studiate le proprietà funzionali di alcune equazioni integrali lineari che regolano problemi basilari della dinamica dei gas rarefatti. Gli operatori integrali, relativi alle operazioni stesse, sono analizzati in dettaglio.

     

Periodic Solutions of Symmetric Perturbations of Gravitational Potentials

It is shown that for certain symmetric perturbations of gravitational potentials in the space, which admit two first integrals of motion, a circular solution of the unperturbed system with inclination different from 0 and π gives rise to a periodic solution of the reduced dynamics which is defined in the quotient space of the action by the subgroup that fixes the symmetry axis. In the planar case, if we assume that the system admits a first integral of motion which is also symmetric with respect to the origin, then it is shown that each circular solution of the unperturbed problem gives rise to a periodic solution of the perturbed system.     

On the relationship between ultrasonic and micromechanical properties of contacting rough surfaces

In this work, it is suggested that a unique set of the interfacial stiffness constants, K_N and K_T, is sufficient to characterize the macroscopic elastic response of an interface between two rough contacting surfaces regardless of the direction of incidence of the ultrasonic wave. It is also shown that by combining ultrasonic spectroscopy with the theoretical procedures developed for a single imperfect interface, the stiffness constants of a double interface can be successfully recovered. The values of the stiffness constants determined from ultrasonic measurements are related to the micromechanical interaction and topography of the contacting surfaces using a micromechanical model of two rough surfaces in contact.     

Viscoelastic Solids of Exponential Type. II. Free Energies,Stability and Attractors

The asymptotic behavior for solutions of the semilinear motion equation of a linear viscoelastic solid of exponential type (VSET) is studied and the existence of a global attractor is proved. These results are obtained by means of a suitable class of quadratic free energies defined on the minimal state space and making use of semigroup techniques. This is the second part of a plan which was started in a previous paper [6] by the study of state-space representation, minimality and controllability for VSET.     

Nonadiabatic Van der Pol oscillations in molecular transport

The force exerted by the electrons on the nuclei of a current-carrying molecular junction can be manipulated to engineer nanoscale mechanical systems. In the adiabatic regime a peculiarity of these forces is negative friction, responsible for Van der Pol oscillations of the nuclear coordinates. In this work we study the robustness of the Van der Pol oscillations against high-frequency sources. For this purpose we go beyond the adiabatic approximation and perform full Ehrenfest dynamics simulations. The numerical scheme implements a mixed quantum-classical algorithm for open systems and is capable to deal with arbitrary time-dependent driving fields. We find that the Van der Pol oscillations are extremely stable. The nonadiabatic electron dynamics distorts the trajectory in the momentum-coordinate phase space but preserves the limit cycles in an average sense. We further show that high-frequency fields change both the oscillation amplitudes and the average nuclear positions. By switching the fields off at different times one obtains cycles of different amplitudes which attain the limit cycle only after considerably long times.     

Degenerate Landau levels for tripod-type cold atoms in U(2) Abelian gauge field

New data for positronium beam production efficiency are presented. As a converter of positrons to forward-going positronium, O₂ has been found to be as good as CO₂ from ～250 to 400 eV. Preliminary data is also presented for the production efficiency from Ar at 2.8 eV.