Strongly hyperpolarized gas from parahydrogen by rational design of ligand-capped nanoparticles

The production of hyperpolarized fluids in continuous mode would broaden substantially the range of applications in chemistry, materials science, and biomedicine. Here we show that the rational design of a heterogeneous catalyst based on a judicious choice of metal type, nanoparticle size and surface decoration with appropriate ligands leads to highly efficient pairwise addition of dihydrogen across an unsaturated bond. This is demonstrated in a parahydrogen-induced polarization (PHIP) experiment by a 508-fold enhancement (±78) of a CH3 proton signal and a corresponding 1219-fold enhancement (±187) of a CH2 proton signal using nuclear magnetic resonance (1H-NMR). In contrast, bulk metal catalyst does not show this effect due to randomization of reacting dihydrogen. Our approach results in the largest gas-phase NMR signal enhancement by PHIP known to date. Sensitivity-enhanced NMR with this technique could be used to image microfluidic reactions in-situ, to probe nonequilibrium thermodynamics or for the study of metabolic reactions

2 nd Brazilian Consensus on Chagas Disease, 2015

Abstract Chagas disease is a neglected chronic condition with a high burden of morbidity and mortality. It has considerable psychological, social, and economic impacts. The disease represents a significant public health issue in Brazil, with different regional patterns. This document presents the evidence that resulted in the Brazilian Consensus on Chagas Disease. The objective was to review and standardize strategies for diagnosis, treatment, prevention, and control of Chagas disease in the country, based on the available scientific evidence. The consensus is based on the articulation and strategic contribution of renowned Brazilian experts with knowledge and experience on various aspects of the disease. It is the result of a close collaboration between the Brazilian Society of Tropical Medicine and the Ministry of Health. It is hoped that this document will strengthen the development of integrated actions against Chagas disease in the country, focusing on epidemiology, management, comprehensive care (including families and communities), communication, information, education, and research

Double-quantum double-quantum MAS exchange NMR spectroscopy: Dipolar-coupled spin pairs as probes for slow molecular dynamics

NANCY1-SCD Pharmacie-Odontologie (543952101) / SudocSudocFranceF

Dipolar spectroscopy and spin alignment in electron paramagnetic resonance

Jeschke G, Pannier M, Godt A, Spiess HW. Dipolar spectroscopy and spin alignment in electron paramagnetic resonance. Chemical Physics Letters. 2000;331(2-4):243-252

Confinement effects in ionomers: a high-field pulsed electron spin resonance spectroscopy study

Confinement effects in ionomeric poly(isoprene) homopolymers and poly(styrene)-poly(isoprene) diblock copolymers have been studied by pulsed high-field electron spin resonance spectroscopy. The reorientation of paramagnetic tracers (spin probes) being localized at the interface between the ionic clusters and the polymer has clear uniaxial features. Evidence is given that the dynamical constraints on the poly(isoprene) chains in the diblock copolymer propagate over the whole chain consisting of approximately 170 monomer units or over distances of several nano-meters. (C) 2002 Elsevier Science B.V. All rights reserved

Electron spin relaxation due to small-angle motion: Theory for the canonical orientations and application to hierarchic cage dynamics in ionomers

Analytical expressions for transverse electron spin relaxation induced by small angle motion were derived for the first time within an anisotropic model for rotational diffusion by using an approximation of the spin Hamiltonian and its variation during reorientation that is valid close to the canonical orientations. The dependence of the decay of the stimulated echo on such motion was studied by extensive Monte Carlo simulations and regimes were identified in which the time constant of this decay is related to parameters of the anisotropic diffusion model by simple equations. For testing these theoretical findings and obtaining insight into hierarchical cage dynamics in soft matter, high-field electron paramagnetic resonance (EPR) measurements were performed at a frequency of 94 GHz where the canonical orientations for nitroxide spin labels are well resolved. A combination of continuous wave EPR, saturation recovery measurements, and measurements of the decay of primary and stimulated electron spin echoes was employed to cover time scales from a few picoseconds up to several microseconds. Ionic spin probes attached by electrostatic interactions to the surface of ionic clusters in ionomers were used as a model system in which slow cage reorientation can be studied in the glass transition region of the polymer (0.64<T/T-g<1.05). Three hierarchical reorientation processes of the spin probe were observed on different time scales. The spin probe undergoes fast intramolecular libration on the time scale of a few picoseconds, it experiences a local rearrangement of the cage on the time scale of hundreds of nanoseconds and it performs cooperative reorientation coupled to the structural relaxation of the glassy matrix over time scales comparable to or longer than several microseconds in the glass transition region. (C) 2003 American Institute of Physics

Probing porous polymer resins by high-field electron spin resonance spectroscopy

High-field W-band (95 GHz) electron spin resonance spectroscopy of various spin probes was used to study the structure of highly cross-linked porous polymer resins based on a styrene-divinylbenzene matrix. The pores of these resins were created by template imprinting with reverse micelles solubilized in the mixture of monomers and cross-linkers prior to the polymerization. Functional groups in the resins were introduced by the use of polymerizable cosurfactants in the reverse micelles. Sufficiently large unpolar spin probes exhibit a distribution of mobilities that can be attributed to regions with different degrees of cross-linking in the polymer. The dynamics of a surfactant spin probe is sensitive to the presence of pores and the functionalization of the pore surface with highly polar groups. This effect disappears when the headgroup of the surfactant spin probe is esterified. It can be considered as a structural memory effect related to the use of reverse micelles as templates for imprinting. The result indicates that the pores can be filled or washed selectively