Local canted spin behaviour in Co1.4−x Zn x Ge0.4Fe1.2O4 spinels: A macroscopic, mesoscopic and microscopic study

DC magnetization, neutron depolarization and neutron diffraction (with both polarized and unpolarized neutrons) measurements have been reported for the Co_1.1−x Zn _x Ge_0.1Fe_1.2O₁ spinels with x=0.5, 0.6 and 0.7. Neutron depolarization and neutron diffraction measurements confirm the presence of a long range ferrimagnetic ordering of the local canted spins in these ferrite samples. The observed features of low field magnetization have been explained under the framework of thermally activated domain wall movement of ferrimagnetic arrangement of local canted spins. An important role of magnetic anisotropy (due to the presence of Co²⁺ ions) in establishing the magnetic ordering and domain kinetics in these ferrites has been observed.     

Flow and oxygenation dependent (FLOOD) contrast MR imaging to monitor the response of rat tumors to carbogen breathing

Gradient recalled echo (GRE) images are sensitive to both paramagnetic deoxyhaemoglobin concentration (via T2*) and flow (via T1*). Large GRE signal intensity increases have been observed in subcutaneous tumors during carbogen (5% carbon dioxide, 95% oxygen) breathing. We term this combined effect flow and oxygenation-dependent (FLOOD) contrast. We have now used both spin echo (SE) and GRE images to evaluate how changes in relaxation times and flow contribute to image intensity contrast changes. T1-weighted images, with and without outer slice suppression, and calculated T2, T2* and "flow" maps, were obtained for subcutaneous GH3 prolactinomas in rats during air and carbogen breathing. T1-weighted images showed bright features that increased in size, intensity and number with carbogen breathing. H&E stained histological sections confirmed them to be large blood vessels. Apparent T1 and T2 images were fairly homogeneous with average relaxation times of 850 ms and 37 ms, respectively, during air breathing, with increases of 2% for T1 and 11% for T2 during carbogen breathing. The apparent T2* over all tumors was very heterogeneous, with values between 9 and 23 ms and localized increases of up to 75% during carbogen breathing. Synthesised "flow" maps also showed heterogeneity, and regions of maximum increase in flow did not always coincide with maximum increases in T2*. Carbogen breathing caused a threefold increase in arterial rat blood PaO2, and typically a 50% increase in tumor blood volume as measured by 51Cr-labelled RBC uptake. The T2* increase is therefore due to a decrease in blood deoxyhaemoglobin concentration with the magnitude of the FLOOD response being determined by the vascular density and responsiveness to blood flow modifiers. FLOOD contrast may therefore be of value in assessing the magnitude and heterogeneity of response of individual tumors to blood flow modifiers for both chemotherapy, antiangiogenesis therapy in particular, and radiotherapy.     

Detection of vacancy clustering by combined PAC and lattice location measurements

The formation of impurity-vacancy agglomerates starting with the trapping of monovacancies was studied using a combination of three complementary techniques applied to the system InCu: Perturbed -angular correlation, ion channeling and channeling of conversion electrons. This results in an almost complete picture of the first stage of vacancy agglomeration at In impurities in Cu.This work was supported by the Bundesminister für Forschung und Technologie.     

79Br NMR spectroscopy as a practical tool for kinetic analysis

⁷⁹Br NMR spectroscopy has been used to monitor a series of reactions in which the bromide ion is produced, including the Menschutkin reaction of pyridine with a range of substituted benzyl bromides and a Heck coupling process. In cases where the process could also be monitored using ¹H NMR spectroscopy, the kinetic analyses using heteronuclear magnetic resonance spectroscopy were shown to be completely consistent. Both the utility of the process in following reactions which may be difficult to analyse using other techniques and the practical limitations associated with solvent choice are discussed. Copyright © 2009 John Wiley & Sons, Ltd.     

Magnetic Resonance Microscopy of Heterogeneity in Polymer Electrolyte Membranes

Magnetic resonance microscopy of Nafion 117 is used to measure the spatial variation of solvent dynamics in protonated (acid form) membranes immersed in solvent. Spatial resolution allows determination of membrane material property heterogeneity via T ₂ and diffusion variations to be easily studied in the presence of strong free solvent signal. Variation of T ₂ and diffusion as a function of solvent methanol–water mole fraction is measured. Spatially averaged T ₂ and diffusion data are in general agreement with previous bulk nuclear magnetic resonance studies; however, significant disparities from sample to sample at fixed solvent concentration are present in the spatially averaged data. The variation is determined to be due to changes in solvent mobility within the membrane over scales of the order of 10 mm, indicating macroscale heterogeneity of the solvent saturated membrane morphology. Authors' address: Sarah L. Codd, Department of Mechanical and Industrial Engineering, Montana State University, Bozeman, MT 59717-3800, USA     

Methodologies for detection of hemoglobin-based oxygen carriers

Blood substitutes based on hemoglobin or hemoglobin-based oxygen carriers (HBOCs) are oxygen-carrying therapeutic agents developed for use in operations and emergencies in place of donated blood. Increased oxygen-carrying capacity through the use of blood substitutes could help elite athletes to lengthen endurance capacity and improve their performance. As blood substitutes become more readily available, it is essential that a qualitative detection method for their abuse in sport is available. Ideally, such a method would be simple and inexpensive. This study investigates methods that could be used as screening procedures to easily detect HBOCs in plasma and develops tests that can unequivocally confirm their presence. The investigation into the screening method indicates that the direct visual screening of plasma discoloration is the most appropriate with detection limits of less than 1% HBOC in plasma. Two methods are shown to confirm the presence of exogenous hemoglobin in plasma samples, size-exclusion chromatography with photodiode array detection and high-performance liquid chromatography analysis of enzymatic digests with detection by electrospray mass spectrometry. This work emphasizes the need for cooperation between drug developers and sports testing laboratories to ensure that methods for the detection of putative doping agents are available prior to product release.     

Stable branching rules for classical symmetric pairs

We approach the problem of obtaining branching rules from the point of view of dual reductive pairs. Specifically, we obtain a stable branching rule for each of classical families of symmetric pairs. In each case, the branching multiplicities are expressed in terms of Littlewood-Richardson coefficients. Some of the formulas are classical and include, for example, Littlewood's restriction rule as a special case.