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Ultraintense laser pulses with a few-cycle rising edge are ideally suited to accelerating ions from ultrathin foils, and achieving such pulses in practice represents a formidable challenge. We show that such pulses can be obtained using sufficiently strong and well-controlled relativistic nonlinearities in spatially well-defined near-critical-density plasmas. The resulting ultraintense pulses with an extremely steep rising edge give rise to significantly enhanced carbon ion energies consistent with a transition to radiation pressure acceleration.

Quantum calculations at the DFT-D3/def2-TZVPD level of theory have been used to examine complexes between O2YBr (Y═N, P, and As) molecules and several Lewis bases, that is, NH3, H2O, and HF. The interactions of the lone pair of the ammonia, water, and hydrogen fluoride with the σ-hole and π-hole of O2YBr molecules have been considered. In general, the complexes where the Lewis base lone pair interacts with the π-hole are more favorable than those with σ-hole. The nature of the interactions has been characterized with the Bader theory of atoms in molecules (AIM). We have also studied the ability of trifluoronitromethane and nitromethane to interact with anions using their π-hole along with an analysis the Cambridge Structural Database. We have found a large number of hits that provide strong experimental support for ability of the nitryl (-NO2) group to interact with anions and Lewis bases. In some X-ray structures, the π-hole interaction is crucial in the crystal packing and has a strong influence in the solid state architecture of the complexes. Finally, due to the relevance in atmospheric chemistry, we have studied noncovalent σ/π-hole complexes of nitryl bromide with ozone.

A fully nonlinear sharp-boundary model of the ablative Rayleigh-Taylor instability is derived and closed in a similar way to the self-consistent closure of the linear theory. It contains the stabilizing effect of ablation and accurately reproduces the results of 2D DRACO simulations. The single-mode saturation amplitude, bubble and spike evolutions in the nonlinear regimes, and the seeding of long-wavelength modes via mode coupling are determined and compared with the classical theory without ablation. Nonlinear stability above the linear cutoff is also predicted.

Intrinsically disordered proteins (IDPs) are not well described by a single 3D conformation but by an ensemble of them, which makes their structural characterization especially challenging, both experimentally and computationally. Most all-atom force fields are designed for folded proteins and give too compact IDP conformations. α-Synuclein is a well-known IDP because of its relation to Parkinson’s disease (PD). To understand its role in this disease at the molecular level, an efficient methodology is needed for the generation of conformational ensembles that are consistent with its known properties (in particular, with its dimensions) and that is readily extensible to post-translationally modified forms of the protein, commonly found in PD patients. Herein, we have contributed to this goal by performing explicit-solvent, microsecond-long Replica Exchange with Solute Scaling (REST2) simulations of α-synuclein with the coarse-grained force field SIRAH, finding that a 30% increase in the default strength of protein–water interactions yields a much better reproduction of its radius of gyration. Other known properties of α-synuclein, such as chemical shifts, secondary structure content, and long-range contacts, are also reproduced. Furthermore, we have simulated a glycated form of α-synuclein to suggest the extensibility of the method to its post-translationally modified forms. The computationally efficient REST2 methodology in combination with coarse-grained representations will facilitate the simulations of this relevant IDP and its modified forms, enabling a better understanding of their roles in disease and potentially leading to efficient therapies.

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A systematic study of the thermodynamic stability of various Cu­(II) complexes with aminoguanidine (AG) is performed, together with the study of its secondary antioxidant activity. Calculations have been carried out at the M05­(SMD)/6-311+G­(d,p) level of theory using water as the solvent. The results obtained indicate that AG is capable of forming a wide array of stable coordination compounds with Cu­(II) under physiological pH conditions, and it possesses some degree of secondary antioxidant activity when coordinating to copper. The most thermodynamically stable complex can slow down 2.8 times the first step of the Haber–Weiss cycle (from 7.71 × 109 to 2.80 × 109 M–1 s–1) and slightly reduce the potential damage that the formation of •OH radicals can cause. The results of this research add to previous knowledge on this molecule, which could be used as a potential glycation inhibitor.

We report on experimental studies of ion acceleration from spherical targets of diameter 15 microm irradiated by ultraintense (1x10(20) W/cm2) pulses from a 20-TW Ti:sapphire laser system. A highly directed proton beam with plateau-shaped spectrum extending to energies up to 8 MeV is observed in the laser propagation direction. This beam arises from acceleration in a converging shock launched by the laser, which is confirmed by 3-dimensional particle-in-cell simulations. The temporal evolution of the shock-front curvature shows excellent agreement with a two-dimensional radiation pressure model.