There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Magnetic resonance (MR) is one of the most versatile and useful physical effects used for human imaging, chemical analysis, and the elucidation of molecular structures. However, its full potential is rarely used, because only a small fraction of the nuclear spin ensemble is polarized, that is, aligned with the applied static magnetic field. Hyperpolarization methods seek other means to increase the polarization and thus the MR signal. A unique source of pure spin order is the entangled singlet spin state of dihydrogen, parahydrogen (pH2 ), which is inherently stable and long-lived. When brought into contact with another molecule, this "spin order on demand" allows the MR signal to be enhanced by several orders of magnitude. Considerable progress has been made in the past decade in the area of pH2 -based hyperpolarization techniques for biomedical applications. It is the goal of this Review to provide a selective overview of these developments, covering the areas of spin physics, catalysis, instrumentation, preparation of the contrast agents, and applications.

Parahydrogen-Based Hyperpolarization for Biomedicine

SpinDynamica is a set of Mathematica packages for performing numerical and symbolic analysis of a wide range of magnetic resonance experiments and phenomena. An overview of the SpinDynamica architecture and functionality is given, with some simple representative examples.

SpinDynamica: Symbolic and numerical magnetic resonance in a Mathematica environment.

Fat intake has been associated with increased risk of cardiovascular disease, obesity, and diabetes. The aim of this study was to reformulate meat products using amorphous cellulose fiber (Z-trim®) as a fat substitute. Based on a Response Surface Methodology, an emulsified and cooked meat model system was carried out with a standard formulation with 20 g/100 g pork fat, and replacement levels of pork fat (from 0 to 20 g/100 g) by amorphous cellulose fiber (from 0 to 1.5 g/100 g). The independent variables within the levels studied influenced the dependent variables emulsion stability (from 73.64 to 91.76 g/100 g), firmness (from 27.32 to 48.02 N), hardness (from 50.86 to 83.00 N), b* color coordinate (14 days) (from 13.08 to 14.45), and weight loss during storage (from 1.88 to 5.16 g/100 g). Comparing the fitted models to the results of the standard sample, it is possible to obtain products with 1.3 g/100 g amorphous cellulose fiber and 10 g/100 g pork fat (50% fat reduction), with technological characteristics similar to the standard sample.

Dietary fiber as fat substitute in emulsified and cooked meat model system

Recently, a facile method for the synthesis of size-monodisperse Pt, Pt3Sn, and PtSn intermetallic nanoparticles (iNPs) that are confined within a thermally robust mesoporous silica (mSiO2) shell was introduced. These nanomaterials offer improved selectivity, activity, and stability for large-scale catalytic applications. Here we present the first study of parahydrogen-induced polarization NMR on these Pt-Sn catalysts. A 3000-fold increase in the pairwise selectivity, relative to the monometallic Pt, was observed using the PtSn@mSiO2 catalyst. The results are explained by the elimination of the three-fold Pt sites on the Pt(111) surface. Furthermore, Pt-Sn iNPs are shown to be a robust catalytic platform for parahydrogen-induced polarization for in vivo magnetic resonance imaging.

Silica-Encapsulated Pt-Sn Intermetallic Nanoparticles: A Robust Catalytic Platform for Parahydrogen-Induced Polarization of Gases and Liquids.

Pairwise and random addition processes are ordinarily indistinguishable in hydrogenation reactions. The distinction becomes important only when the fate of spin correlation matters, such as in parahydrogen-induced polarization (PHIP). Supported metal catalysts were not expected to yield PHIP signals given the rapid diffusion of H atoms on the catalyst surface and in view of the sequential stepwise nature of the H atom addition in the Horiuti-Polanyi mechanism. Thus, it seems surprising that supported metal hydrogenation catalysts can yield detectable PHIP NMR signals. Even more remarkably, supported Pt and Ir nanoparticles are shown herein to catalyze pairwise replacement on propene and 3,3,3-trifluoropropene. By simply flowing a mixture of parahydrogen and alkene over the catalyst, the scalar symmetrization order of the former is incorporated into the latter without a change in molecular structure, producing intense PHIP NMR signals on the alkene. An important indicator of the mechanism of the pairwise replacement is its stereoselectivity, which is revealed with the aid of density matrix spectral simulations. PHIP by pairwise replacement has the potential to significantly diversify the substrates that can be hyperpolarized by PHIP for biomedical utilization.

Parahydrogen-induced polarization by pairwise replacement catalysis on Pt and Ir nanoparticles

Z-trim is a zero calorie cellulosic fiber biopolymer produced from corn hulls. The micro-structural heterogeneities of Z-trim biopolymer were investigated by monitoring the thermally driven displacements of well-dispersed micro-spheres via video fluorescence microscopy named multiple-particle tracking (MPT). By comparing the distribution of the time-dependent mean-square displacement (MSD) of polystyrene micro-spheres embedded in three concentrations of Z-trim, we found that the degree of heterogeneity of the suspensions increased dramatically within a narrow range of concentrations. The ensemble-averaged MSD of 0.5 g/100 g Z-trim biopolymer exhibited a power-law behavior that scaled log-linearly with time lag. This behavior was similar to that of homogeneous aqueous glycerol solution. But the MSD distribution for Z-trim was wider and more asymmetric than for glycerol. Increasing Z-trim concentration caused more deviation of micro-spheres colloidal dispersion from homogeneity as detected by the MPT.

Micro-heterogeneity of cellulosic fiber biopolymer prepared from corn hulls

The invention relates to an application of a natural galactomannan, in particular to a petrochemical application of a natural galactomannan modified by quaternary ammonium salt (comprising guar gum, fenugreek gum or locust bean gum or degradation products thereof) as a relative permeability regulator. The invention provides a new application of the natural galactomannan, thereby widening the application fields of the natural galactomannan and also overcoming the disadvantages of the existing relative permeability regulators (RPM), such as complicated preparation, environmental pollution, etc.

Usage of cationic galactomannan

Parahydrogen induced polarization using heterogeneous catalysis can produce impurity-free hyperpolarized gases and liquids, but the comparatively low signal enhancements and limited scope of substrates that can be polarized pose significant challenges to this approach. This study explores the surface processes affecting the disposition of the bilinear spin order derived from parahydrogen in the hydrogenation of propyne over TiO2-supported Pt nanoparticles. The hyperpolarized adducts formed at low magnetic field are adiabatically transported to high field for analysis by proton NMR spectroscopy at 400 MHz. For the first time, the stereoselectivity of pairwise addition to propyne is measured as a function of reaction conditions. The correlation between partial reduction selectivity and stereoselectivity of pairwise addition is revealed. The systematic trends are rationalized in terms of a hybrid mechanism incorporating non-traditional concerted addition steps and well-established reversible step-wise addition involving the formation of a surface bound 2-propyl intermediate.

Parahydrogen enhanced NMR reveals correlations in selective hydrogenation of triple bonds over supported Pt catalyst

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Parahydrogen-induced polarization by pairwise replacement catalysis on Pt and Ir nanoparticles

Micro-heterogeneity of cellulosic fiber biopolymer prepared from corn hulls

Usage of cationic galactomannan

Parahydrogen enhanced NMR reveals correlations in selective hydrogenation of triple bonds over supported Pt catalyst