NMR Relaxivities of Paramagnetic, Ultra-High Spin Heterometallic Clusters within Polyoxometalate Matrix as a Function of Solvent and Metal Ion.

Selectivity and image contrast are always challenging in magnetic resonance imaging (MRI), which are - inter alia - addressed by contrast agents. These compounds still need to be improved, and their relaxation properties, i. e., their paramagnetic relaxation enhancement (PRE), needs to be understood. The main goal is to improve specificity and relaxivities, especially at the high magnetic fields currently exploited not only in material science but also in the medical environment. Longitudinal and transverse relaxivities, r1 and r2 , which correspond to the longitudinal and transverse relaxation rates R1 and R2, normalized to the concentration of the paramagnetic moieties, need to be considered because both contribute to the image contrast. 1 H-relaxivities r1 and r2 of high-spin heterometallic clusters were studied containing lanthanide and transition-metal ions within a polyoxometalate matrix. A wide range of magnetic fields from 0.5 T/20 MHz to 33 T/1.4 GHz was applied. The questions addressed here concern the rotational and diffusion correlation times which determine the relaxivities and are affected by the solvent's viscosity. Moreover, the variation of the lanthanide and transition-metal ions of the clusters provided insights into the sensitivity of PRE with respect to the electron spin properties of the paramagnetic centers as well as cooperative effects between lanthanides and transition metal ions.

Nuclear magnetic resonance/magnetic resonance imaging on lubricating greases: Observation of bleeding and aging.

Lubricating greases were investigated by nuclear magnetic resonance/magnetic resonance imaging (NMR/MRI) to get insight into their structure and into their response to mechanical forces, which is related to bleeding and aging. The investigated greases are based on metallic soaps of fatty acids and oils, whereby LiOH is often used. These organic soaps act as thickeners and provide a network in which oils and their additives are embedded. Lubricating greases can thus be considered as a class of substances similar to oleogels or even hydrogels. Questions arise about translational mobility of guest molecules, mainly base oil, in these networks. Molecular structuring and interactions within the network of thickeners are of interest as they are related to macroscopic stability. Apart from NMR spectroscopy (1 H-, 7 Li- and 31 P-NMR), spectrally resolved relaxation and diffusion measurements are used for characterization. In addition, magic angle spinning (MAS)-NMR was combined with 1 H-MRI to investigate the impact of mechanical stress and swelling of lubricating greases.

Contact-mediated nucleation in melt emulsions investigated by rheo-nuclear magnetic resonance.

Increasing the efficiency of disperse phase crystallization is of great interest for melt emulsion production as the fraction of solidified droplets determines product quality and stability. Nucleation events must appear within every single one of the µm-sized droplets for solidification. Therefore, primary crystallization requires high subcooling and is, thus, time and energy consuming. Contact-mediated nucleation is a mechanism for intensifying the crystallization process. It is defined as the successful nucleation of a subcooled liquid droplet induced by contact with an already crystallized droplet. We investigated contact-mediated nucleation under shear flow conditions up to shear rates of 457 s-1 for a quantitative assessment of this mechanism. Rheo-nuclear magnetic resonance was successfully used for the time-resolved determination of the solids fraction of the dispersed phase of melt emulsions upon contact-mediated nucleation events. The measurements were carried out in a dedicated Taylor-Couette cell. The efficiency of contact-mediated nucleation λsec decreased with increasing shear rate, whereas the effective second order kinetic constant kcoll,eff increased approximately linearly at small shear rates and showed a linear decrease for shear rates higher than about 200 s-1 . These findings are in accordance with coalescence theory. Thus, the nucleation rate is optimal at specific flow conditions. There are limitations for successful inoculation at a low shear rate because of rare contact events and at a high shear rate due to too short contact time.

Structural Characterisation of Deposit Layer during Milk Protein Microfiltration by Means of In-Situ MRI and Compositional Analysis.

Milk protein fractionation by microfiltration membranes is an established but still growing field in dairy technology. Even under cross-flow conditions, this filtration process is impaired by the formation of a deposit by the retained protein fraction, mainly casein micelles. Due to deposition formation and consequently increased overall filtration resistance, the mass flow of the smaller whey protein fraction declines within the first few minutes of filtration. Currently, there are only a handful of analytical techniques available for the direct observation of deposit formation with opaque feed media and membranes. Here, we report on the ongoing development of a non-invasive and non-destructive method based on magnetic resonance imaging (MRI), and its application to characterise deposit layer formation during milk protein fractionation in ceramic hollow fibre membranes as a function of filtration pressure and temperature, temporally and spatially resolved. In addition, the chemical composition of the deposit was analysed by reversed phase high pressure liquid chromatography (RP-HPLC). We correlate the structural information gained by in-situ MRI with the protein amount and composition of the deposit layer obtained by RP-HPLC. We show that the combination of in-situ MRI and chemical analysis by RP-HPLC has the potential to allow for a better scientific understanding of the pressure and temperature dependence of deposit layer formation.

Polyoxometalate-based high-spin cluster systems: a NMR relaxivity study up to 1.4 GHz/33 T.

Paramagnetic polyoxometalates [RE30Co8Ge12W108O408(OH)42(OH2)30]56- (Rare Earth (RE): Gd, Dy, Eu, and Y) are of special interest with regard to their application as alternative contrast agents in non-human magnetic resonance imaging which is increasingly used in materials science and process engineering. This class of new paramagnetic materials promises detailed findings in the magnetic resonance images due to their rather large total electron spin on the one hand, i.e. large, field-dependent relaxivities up to the highest magnetic fields, and due to their relatively large cluster sizes with an impact on adsorption and penetration on the other hand. Apart from the magnetic field dependence, the sensitivity of relaxivities to motional correlation times will be shown for these polyoxometalates which is a prerequisite for modelling and understanding the physical behaviour of this new class of polyoxometalates in MRI. Also for the qualitative and quantitative interpretation of MR images, the knowledge of transverse and longitudinal relaxivities of the paramagnetic clusters in a given environment is mandatory. Examples considered in this publication are proteins in milk fractionation, the deposit of which was measured by MRI.

In situ measurement of deposit layer formation during skim milk filtration by MRI.

Filtration and separation via membranes are key processes in food processing. One major application of membrane filtration is in the dairy industry, aiming for the separation of different milk proteins. The various chemical components of milk possess different physiochemical properties and can be used most effectively in food processing if they are separately available and remain in their native state. Microfiltration of skim milk allows a fractionation of the milk proteins casein and whey by size. A deposit is formed on the membrane surface mainly but not exclusively by micellar casein proteins during filtration. Membrane pore blockage by whey proteins and fouling occur during membrane filtration, negatively affecting the yield of the whey protein fraction. Skim milk filtration and the deposit layer formation were measured time and spatially resolved by in situ magnetic resonance imaging (MRI). The nature of the fouling layer was investigated during dead-end filtration in ceramic hollow fiber membranes. MRI was used to further clarify the influence of operating conditions on separation and filtration mechanisms that are responsible for growth of the fouling layer and its reversibility. The MRI measurements were analyzed for a detailed description of skim milk filtration by modeling the signal intensity distribution.

CACNA1C gene polymorphisms, cardiovascular disease outcomes, and treatment response.

BACKGROUND: The gene encoding the target of calcium channel blockers, the alpha1c-subunit of the L-type calcium channel (CACNA1C), has not been well characterized, and only small pharmacogenetic studies testing this gene have been published to date. METHODS AND RESULTS: Resequencing of CACNA1C was performed followed by a nested case-control study of the INternational VErapamil SR/trandolapril STudy (INVEST) GENEtic Substudy (INVEST-GENES). Of 46 polymorphisms identified, 8 were assessed in the INVEST-GENES. Rs1051375 was found to have a significant interaction with treatment strategy (P=0.0001). Rs1051375 A/A genotype was associated with a 46% reduction in the primary outcome among those randomized to verapamil SR treatment, when compared with atenolol treatment (odds ratio 0.54 95% CI 0.32 to 0.92). In heterozygous A/G individuals, there was no difference in the occurrence of the primary outcome when randomized to verapamil SR versus atenolol treatment (odds ratio 1.47 95% CI 0.86 to 2.53), whereas homozygous G/G individuals had a greater than 4-fold increased risk of the primary outcome with verapamil treatment compared with those randomized to atenolol treatment (odds ratio 4.59 95% CI 1.67 to 12.67). We did not identify allelic expression imbalance or differences in mRNA expression in heart tissue by rs1051375 genotype. CONCLUSIONS: Variation in CACNA1C is associated with treatment response among hypertensive patients with stable coronary artery disease. Our data suggest a genetically defined group of patients that benefit most from calcium channel blocker therapy, a group that benefits most from beta-blocker therapy, and a third group in which calcium channel blocker and beta-blocker therapy are equivalent.

Similarities of periodontal clinical and microbiological parameters in mother-child pairs / Similaridades da clinica periodontal e parametros microbiológicos em pares mãe-filho

The aim of this study was to verify the association between children and their mothers (N=28) for periodontal clinical and microbiological measures. Periodontal clinical parameters (probing depth and bleeding on probing) were obtained from six reference teeth from each mother-child pair. In addition, subgingival plaque samples taken from the same reference teeth were collected and placed on the Perioscan test for the detection of Treponema denticola, Porphyromonas gingivalis and Bacteroides forsythus. There were statistically significant differences between children and mothers regarding probing depth; there was an overall tendency for mothers to exhibit average probing depths greater than their children. In contrast, if a child had a bleeding site, the respective site on the mother usually also bled on probing, implying that there was an association in terms of bleeding between the mother-child pairs. Similar findings were observed for the Perioscan test. It is concluded that the occurrence of bleeding and periodontal anaerobic infections (as determined by the Perioscan test)were similar in reference teeth of mother-child pairs. These data suggest that parents with periodontal disease may serve as a reservoir of periodontopathic organisms for their children