Discrimination of Individual Tigers (\u3cem\u3ePanthera tigris\u3c/em\u3e) from Long Distance Roars

This paper investigates the extent of tiger (Panthera tigris) vocal individuality through both qualitative and quantitative approaches using long distance roars from six individual tigers at Omaha\u27s Henry Doorly Zoo in Omaha, NE. The framework for comparison across individuals includes statistical and discriminant function analysis across whole vocalization measures and statistical pattern classification using a hidden Markov model (HMM) with frame-based spectral features comprised of Greenwood frequency cepstral coefficients. Individual discrimination accuracy is evaluated as a function of spectral model complexity, represented by the number of mixtures in the underlying Gaussian mixture model (GMM), and temporal model complexity, represented by the number of sequential states in the HMM. Results indicate that the temporal pattern of the vocalization is the most significant factor in accurate discrimination. Overall baseline discrimination accuracy for this data set is about 70% using high level features without complex spectral or temporal models. Accuracy increases to about 80% when more complex spectral models (multiple mixture GMMs) are incorporated, and increases to a final accuracy of 90% when more detailed temporal models (10-state HMMs) are used. Classification accuracy is stable across a relatively wide range of configurations in terms of spectral and temporal model resolution

Inclusions of C*-algebras of graded groupoids

We consider a locally compact Hausdorff groupoid $G$ which is graded over a discrete group. Then the fibre over the identity is an open and closed subgroupoid $G_e$. We show that the full C*-algebra of this subgroupoid embeds isometrically into the full C*-algebra of the groupoid; this extends a theorem of Kaliszewski--Quigg--Raeburn from the \'etale to the non-\'etale setting. We use the same ideas to investigate a possible embedding of the reduced C*-algebra of the subgroupoid in the reduced C*-algebra of the groupoid, and find that there is an obstruction in the kernel of the quotient map from the full to the reduced C*-algebras of $G_e$. As an application we show that the full and reduced C*-algebras of $G$ are topologically graded in the sense of Exel, and we discuss the full and reduced C*-algebras of the associated bundles.Comment: 12 page

The strangeness form factors of the proton

The present empirical information on the strangeness form factors indicates that the corresponding $uuds\bar s$ component in the proton is such that the $uuds$ subsystem has the flavor spin symmetry $[4]_{FS}[22]_F[22]_S$ and mixed orbital symmetry $[31]_X$. This $uuds\bar s$ configuration leads to the empirical signs of all the form factors $G_E^s$, $G_M^s$ and $G_A^s$. An analysis with simple quark model wave functions for the preferred configuration shows that the qualitative features of the empirical strangeness form factors may be described with a $\sim$ 15% admixture of $uuds\bar s$ with a compact wave function in the proton. Transition matrix elements between the $uud$ and the $uuds\bar s$ components give significant contributions

Strongly interacting σ\sigma-electrons and MgB2_2 superconductivity

MgB$(p^{n_{\sigma}}p^{n_{\pi}})_{2}$ is classified as a system with strongly interacting $\sigma$-electrons and non-correlated $\pi$-electrons of boron ions. The kinematic and Coulomb interaction V between the orbitally degenerated $\sigma$-electrons provide the superconducting state with an anisotropic gap of s*-wave symmetry. The critical temperature $T_c$ has a non-monotonic dependence on the distance r between the centers of gravity of $\sigma$- and $\pi$-bands. MgB$_2$ corresponds to r=0.085 eV and V=0.45 eV in our model with flat bands. The derived superconducting density of electronic states is in good agreement with available experimental and theoretical data. The possibilities for increasing $T_c$ are discussed.Comment: 8 pages, 4 figure

Filtering germs: Groupoids associated to inverse semigroups

We investigate various groupoids associated to an arbitrary inverse semigroup with zero. We show that the groupoid of filters with respect to the natural partial order is isomorphic to the groupoid of germs arising from the standard action of the inverse semigroup on the space of idempotent filters. We also investigate the restriction of this isomorphism to the groupoid of tight filters and to the groupoid of ultrafilters.Comment: 9 pages. This version matches the version in Expositiones Mathematica

Strangeness in the proton and N*(1535)

The newest progress on the study of the strangeness in the proton and in the lowest negative parity nucleon excited state $N^*(1535)$ is reviewed. Implications on the internal quark structure of the proton, $N^*(1535)$ and other baryons are discussed. The diquark cluster picture for the 5-quark components in baryons gives a natural explanation not only to the empirical indications for a positive strangeness magnetic moment $\mu_s$ and positive strangeness radius of the proton but also the longstanding mass-reverse problem of $N^*(1535)$, $N^*(1440)$ and $\Lambda^*(1405)$ resonances as well as the unusual decay pattern of the $N^*(1535)$ resonance. Evidence for possible existence of $N^*(1535)$'s ${1/2}^-$ SU(3) nonet partners in this picture is pointed out, and suggestion is made to search for these $1/2^-$ hyperon excited states under the well known $\Sigma^*(1385)$, $\Lambda^*(1520)$ and $\Xi^*(1530)$ peaks in various reactions.Comment: 6 pages, 2 figures, Plenary talk at 18th International IUPAP Conference on Few-Body Problems in Physics August 21-26. 2006 Santos SP Brazil; to be published in Nuclear Physics

Electronic Structure, Electron-Phonon Coupling, and Multiband Effects in MgB2

We review the current situation in the theory of superconducting and transport properties of MgB2. First principle calculations of of the electronic structure and electron-phonon coupling are discussed and compared with the experiment. We also present a brief description of the multiband effects in superconductivity and transport, and how these manifest themselves in MgB2. We also mention some yet open questions.Comment: Physica C, in pres

Scanning Tunneling Spectroscopy in MgB 2

We present extensive Scanning Tunneling Spectroscopy (STM/S) measurements at low temperatures in the multiband superconductor MgB$_2$. We find a similar behavior in single crystalline samples and in single grains, which clearly shows the partial superconducting density of states of both the $\pi$ and $\sigma$ bands of this material. The superconducting gaps corresponding to both bands are not single valued. Instead, we find a distribution of superconducting gaps centered around 1.9mV and 7.5mV, corresponding respectively to each set of bands. Interband scattering effects, leading to a single gap structure at 4mV and a smaller critical temperature can be observed in some locations on the surface. S-S junctions formed by pieces of MgB$_2$ attached to the tip clearly show the subharmonic gap structure associated with this type of junctions. We discuss future developments and possible new effects associated with the multiband nature of superconductivity in this compound.Comment: 11 pages, 6 figures, submitted to Physica

Effects of C, Cu and Be substitutions in superconducting MgB2

Density functional calculations are used to investigate the effects of partial substitutional alloying of the B site in MgB2 with C and Be alone and combined with alloying of the Mg site with Cu. The effect of such substitutions on the electronic structure, electron phonon coupling and superconductivity are discussed. We find that Be substitution for B is unfavorable for superconductivity as it leads to a softer lattice and weaker electron-phonon couplings. Replacement of Mg by Cu leads to an increase in the stiffness and doping level at the same time, while the carrier concentration can be controlled by partial replacement of B by C. We estimate that with full replacement of Mg by Cu and fractional substitution of B by C, Tc values of 50K may be attainable.Comment: 5 pages, 4 figure