Trapping Transient RNA Complexes by Chemically Reversible Acylation

RNA-RNA interactions are essential for biology, but they can be difficult to study due to their transient nature. While crosslinking strategies can in principle be used to trap such interactions, virtually all existing strategies for crosslinking are poorly reversible, chemically modifying the RNA and hindering molecular analysis. We describe a soluble crosslinker design (BINARI) that reacts with RNA through acylation. We show that it efficiently crosslinks noncovalent RNA complexes with mimimal sequence bias and establish that the crosslink can be reversed by phosphine reduction of azide trigger groups, thereby liberating the individual RNA components for further analysis. The utility of the new approach is demonstrated by reversible protection against nuclease degradation and trapping transient RNA complexes of E. coli DsrA-rpoS derived bulge-loop interactions, which underlines the potential of BINARI crosslinkers to probe RNA regulatory networks.     

From resolvents to càdlàg processes through compact excessive functions and applications to singular SDE on Hilbert spaces

We present an approach for constructing càdlàg strong Markov processes given a resolvent of kernels. The conditions imposed on the resolvent are checkable in applications and allow the control of the set of admissible starting points of the process. The main application is to singular SDEs on Hilbert spaces.     

Semiclassical neutral atom as a reference system in density functional theory

We use the asymptotic expansions of the semiclassical neutral atom as a reference system in density functional theory to construct accurate generalized gradient approximations (GGAs) for the exchange-correlation and kinetic energies without any empiricism. These asymptotic functionals are among the most accurate GGAs for molecular systems, perform well for solid state, and overcome current GGA state of the art in frozen density embedding calculations. Our results also provide evidence for the conjointness conjecture between exchange and kinetic energies of atomic systems.     

Comparison between three measurement methods for characterizing the charge state of granular insulating materials

Surface potential decay method has been frequently used to characterize the charge state of insulating materials. The present paper aims at a critical evaluation of this method when used for the characterization of granular plastics, by comparing it with the electric field monitoring by means of non-contact vibrating probes, and with the measurement of the charge induced in a capacitive probe connected to a Coulomb-meter. The experiments were performed on corona-charged polyethylene, polycarbonate, polyamide, and acetyl – butadiene – styrene granular materials. The experimental results show that surface potential decays faster than the electric field or the charge measured with the capacitive probe. The dimensions of the probes and the capacitive coupling between them and the samples, may explain this difference. Part of the potential decay measured by the smaller-size probe of the electrostatic voltmeter is due to the surface conduction, while the measurements made with the larger-size electric field and capacitive probes are less affected by this phenomenon.     

Neutralization of charged insulating granular materials using AC corona discharge

The control of the residual electric charge carried by granular materials processed in various electrostatic installations is a prerequisite for the safe and efficient operation of the respective industrial equipment. The aim of the present work was to evaluate the neutralization efficiency of polyethylene granules exposed to an AC corona discharge from a wire-type electrode. The control variables and their domains of variations were the following: the amplitude and the frequency of the applied high voltage (16–18 kV, 20–400 Hz), the position of the corona electrode (3–7 cm above the ground plate that carries the sample) and the duration of the exposure to the corona discharge (4–10 s). The surface potential decay method was used for monitoring the charge carried by granular samples of PE before and after neutralization. Design of experiment methodology was employed to evaluate the influence of each of the above mentioned control variables and determine the optimum operation conditions. The efficiency of the neutralization was characterized by the ratio between the values of the surface potential before and after AC corona discharge exposure. The obtained results show that neutralization efficiency may be improved by increasing the frequency of the high voltage as well as by adequately correlating its amplitude with the inter-electrode spacing.     

On deformation of associative algebras and graph homology

Deformation theory of associative algebras and in particular of Poisson algebras is reviewed. The role of an “almost contraction” leading to a canonical solution of the corresponding Maurer–Cartan equation is noted. This role is reminiscent of the Homotopical Perturbation Lemma, with the infinitesimal deformation cocycle as “initiator.”Applied to star-products, we show how Moyal's formula can be obtained using such an almost contraction and conjecture that the “merger operation” provides a canonical solution at least in the case of linear Poisson structures.