Muon spin rotation in solids

The muon spin rotation (MuSR) technique is used to probe the microscopic electron density in materials. High temperature MuSR and magnetization measurements in nickel are in progress to allow an unambiguous determination of the muon impurity interaction and the impurity induced change in local spin density. The first results on uniaxial stress induced frequency shifts in an Fe single crystal are also reported

Muon spin rotation research program

Data from cyclotron experiments and room temperature studies of dilute iron alloys and iron crystals under strain were analyzed. The Fe(Mo) data indicate that the effect upon the contact hyperfine field in Fe due to the introduction of Mo is considerably less than that expected from pure dilution, and the muon (+) are attracted to the Mo impurity sites. There is a significant change in the interstitial magnetic field with Nb concentration. The Fe(Ti) data, for which precession could clearly be observed early only at 468K and above, show that the Ti impurities are attractive to muon (+), and the magnitude of B(hf) is reduced far beyond the amount expected from pure dilution. Changes in the intersitital magnetic field with the introduction of Cr, W, Ge, and Si are also discussed. When strained to the elastic limit, the interstitial magnetic field in Fe crystals is reduced by 33 gauss, and the relaxation rate of the precession signal increases by 47%

Material science and solid state physics studies with positive muon spin precession

The hyperfine field on the muon, B sub hf, at interstitial sites in dilute Fe(Al) alloys was measured for four different concentrations of Al and as a function of temperature by the muon spin rotation method. The magnitude of B sub hf, which is negative, decreases at rates ranging from 0.09 + or - 0.03% per at.% Al at 200 K to an asymptotic limit of 0.35 + or - far above 440 K. This behavior shows that sites near the Al impurity are weakly repulsive to the muon, with an interaction potential of 13 + or - 3 meV. In order to fit the temperature dependence of the hyperfine field, it is necessary to hypothesize the existence of a small concentration of unidentified defects, possibly dislocations, which are attractive to the muon. Although the Al impurity acts as a non-magnetic hole in the Fe lattice, the observed decrease in B sub hf is only 35% of the decrease in the bulk magnetization. It is concluded that B sub hf is determined mainly by the enhanced screening of conduction electrons in Fe and Fe(Al). Since the influence of the Al impurity on the neighboring Fe monents is very small, most of the change in B sub hf is therefore attributed to the increase in conduction electron polarization of the Al impurity

Two muscle-specific LIM proteins in Drosophila

Journal ArticleThe LIM domain defines a zinc-binding motif found in a growing number of eukaryotic proteins that regulate cell growth and differentiation during development. Members of the cysteine-rich protein (CRP) family of LIM proteins have been implicated in muscle differentiation in vertebrates. Here we report the identification and characterization of cDNA clones encoding two members of the CRP family in Drosophila, referred to as muscle LIM proteins (Mlp)

Muscle LIM proteins are associated with muscle sarcomeres and require dMEF2 for their expression during Drosophila myogenesis

Journal ArticleA genetic hierarchy of interactions, involving myogenic regulatory factors of the MyoD and myocyte enhancer-binding 2 (MEF2) families, serves to elaborate and maintain the differentiated muscle phenotype through transcriptional regulation of muscle-specific target genes

Coexistence of ferromagnetism and superconductivity in the hybrid ruthenate-cuprate compound RuSr_2GdCu_2O_8 studied by muon spin rotation (\mu SR) and DC-magnetization

We have investigated the magnetic and the superconducting properties of the hybrid ruthenate-cuprate compound RuSr_{2}GdCu_{2}O_{8} by means of zero-field muon spin rotation- (ZF-$\mu$SR) and DC magnetization measurements. The DC-magnetisation data establish that this material exhibits ferromagnetic order of the Ru-moments ($\mu (Ru) \approx 1 \mu_{B}$) below T_{Curie} = 133 K and becomes superconducting at a much lower temperature T_c = 16 K. The ZF-$\mu$SR experiments indicate that the ferromagnetic phase is homogeneous on a microscopic scale and accounts for most of the sample volume. They also suggest that the magnetic order is not significantly modified at the onset of superconductivity.Comment: improved version submitted to Phys. Rev.

Magnetic Fields of Vortices in a Superconducting Thin Film

The magnetic fields associated with a single superconducting vortex traversing a thin film are calculated. The formulation of Pearl, which has been used for a geometry in which for z0 one has superconducting material, is extended to the case of a thin film. For the thin film, the flux in the mid-plane is less than a flux quantum unless one uses a very large radius. For instance a 100 nm film with a 130 nm penetration depth (lambda) has only 80% of a flux quantum within a radius of 1.5 mu m = 11.5.lambda. At 10 mu m 96% is enclosed. The magnetic field near the surface in both geometries has a significant radial component. The fields for a vortex array are then obtained by summing the fields from nearby vortices. The measurability of the field distributions is discussed

Productive Energy of Corn Meal, Alfalfa Leaf Meal, Dried Buttermilk, Casein, Cottonseed Meal, and Tankage as Measured by Production of Fat and Flesh by Growing Chickens.

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Productive Energy of Some Feeds and Foods as Measured by Gains of Energy by Growing Chickens.

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