Magnetic studies of GaN nanoceramics

The synthesis, morphology and magnetization measurements of GaN nanoceramics obtained under high pressure are reported. In particular the effect of grain size on magnetic properties of GaN nanopowders and nanoceramics was investigated. It was found that for the GaN nanoceramic characterized by the stronger deformation of nanocrystalline grains the diamagnetic signal changes with external magnetic field similarly to the Meissner effect in superconductors.Comment: 3 pages, 4 figures, accepted Appl.Phys.Let

Science Icebreaker Activities: An Example from Gravitational Wave Astronomy

At the beginning of a class or meeting an icebreaker activity is often used to help loosen the group and get everyone talking. Our motivation is to develop activities that serve the purpose of an icebreaker, but are designed to enhance and supplement a science-oriented agenda. The subject of this article is an icebreaker activity related to gravitational wave astronomy. We first describe the unique gravitational wave signals from three distinct sources: monochromatic binaries, merging compact objects, and extreme mass ratio encounters. These signals form the basis of the activity where participants work to match an ideal gravitational wave signal with noisy detector output for each type of source.Comment: Accepted to The Physics Teacher. Original manuscript divided into two papers at the request of the referee. For a related paper on gravitational wave observatories see physics/050920

H-2 mutation affecting immune response to Thy-1.1 antigen

Mouse thymus, thymus-derived lymphocytes, and brain share an antigen determined by gene at the Thy-1 locus in chromosome 9 (1). Two alleles have been identified at this locus: Thy-1(a), coding for antigen Thy-1.1 (or θ-AKR) present in AKR and seven other strains; and Thy-1(b), coding for antigen Thy-1.2 (or{teta}-C3H) and present in C3H and all the remaining inbred strains. Injection of AKR thymocytes into inbred mice carrying the Thy-1(b) allele results in an immune response that can be measured either serologically by determining the level of antibodies in the recipients’ serum (1) or by counting plaque- forming cells (PFC) detectable in spleens of the recipients by means of an assay, with AKR thymocytes as target cells(2). The magnitude of PFC and serum antibody responses after a single thymocyte injection depends on the genetic make-up of the recipient. Three genes controlling the PFC response to the Thy- 1.1 antigen have been identified: Ir-Thy-1A and Ir-Thy-1B, which are closely linked to the major histocompatibility complex (H-2) of the mouse (3-6), and Ir-5, which is located at a distance of 17 cm to the right of the H-2 complex on chromosome 17 (6). Previous genetic mapping with H-2 recombinant strains has indicated that the two Ir-Thy-1 loci are located to the left of the IC subregion (7). Further experiments strongly suggested that either one or both Ir-Thy-1 loci map to the K rather than the I region of the H-2 complex (8). In this report, the study of an H- 2 mutant, CBA-H-2(ka) (M523) (9), and its parental strain, CBA/LacStoY (CBA) provided further evidence that one of these loci apparently resides in the K region and might even be identical with the H-2K locus in that region

SO(5) superconductor in a Zeeman magnetic field: Phase diagram and thermodynamic properties

In this paper we present calculations of the SO(5) quantum rotor theory of high-T$_{c}$ superconductivity in Zeeman magnetic field. We use the spherical approach for five-component quantum rotors in three-dimensional lattice to obtain formulas for critical lines, free energy, entropy and specific heat and present temperature dependences of these quantities for different values of magnetic field. Our results are in qualitative agreement with relevant experiments on high-T$_{c}$ cuprates.Comment: 4 pages, 2 figures, to appear in Phys. Rev. B, see http://prb.aps.or