Structure formation in electromagnetically driven granular media

We report structure formation in submonolayers of magnetic microparticles subjected to periodic electrostatic and magnetic excitations. Depending on the excitation parameters, we observe the formation of a rich variety of structures: clusters, rings, chains, and networks. The growth dynamics and shapes of the structures are strongly dependent on the amplitude and frequency of the external magnetic field. We find that for pure ac magnetic driving at low densities of particles, the low-frequency magnetic excitation favors clusters while high frequency excitation favors chains and net-like structures. An abrupt phase transition from chains to a network phase was observed for a high density of particles.Comment: 4 pages, 5 figure

Prognostic value of troponins in acute coronary syndrome depends upon patient age

Peer reviewedPostprin

The Submillimeter Array

The Submillimeter Array (SMA), a collaborative project of the Smithsonian Astrophysical Observatory (SAO) and the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), has begun operation on Mauna Kea in Hawaii. A total of eight 6-m telescopes comprise the array, which will cover the frequency range of 180-900 GHz. All eight telescopes have been deployed and are operational. First scientific results utilizing the three receiver bands at 230, 345, and 690 GHz have been obtained and are presented in the accompanying papers.Comment: 10 pages, 4 figure

Automated Classification of 2000 Bright IRAS Sources

An Artificial Neural Network (ANN) has been employed using a supervised back-propagation scheme to classify 2000 bright sources from the Calgary database of IRAS (Infrared Astronomy Satellite) spectra in the wavelength region of 8-23 microns. The data base has been classified into 17 pre-determined classes based on spectral morphology. We have been able to classify more than 80 percent of the 2000 sources correctly at the first instance. The speed and robustness of the scheme will allow us to classify the whole of LRS database, containing more than 50,000 sources in the future.Comment: 26 pages, To appear in ApJS after July 200

General study on piezoelectric transformer

Author name used in this publication: Cheng K. W. E.Author name used in this publication: Kwok K. W.Power Electronics Research Center, Department of Electrical EngineeringAuthor name used in this publication: Chan H.Refereed conference paper2004-2005 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

Decision-making by children

In this paper, we examine the determinants of decision-making power by children and young adolescents. Moving beyond previous economic models that treat children as goods consumed by adults rather than agents, we develop a noncooperative model of parental control of child behavior and child resistance. Using child reports of decision-making and psychological and cognitive measures from the NLSY79 Child Supplement, we examine the determinants of shared and sole decision-making in seven domains of child activity. We find that the determinants of sole decision-making by the child and shared decision-making with parents are quite distinct: sharing decisions appears to be a form of parental investment in child development rather than a simple stage in the transfer of authority. In addition, we find that indicators of child capability and preferences affect reports of decision-making authority in ways that suggest child demand for autonomy as well as parental discretion in determining these outcomes

An increase in TcT_c under hydrostatic pressure in the superconducting doped topological insulator Nb0.25_{0.25}Bi2_2Se3_3

We report an unexpected positive hydrostatic pressure derivative of the superconducting transition temperature in the doped topological insulator \NBS via $dc$ SQUID magnetometry in pressures up to 0.6 GPa. This result is contrary to reports on the homologues \CBS and \SBS where smooth suppression of $T_c$ is observed. Our results are consistent with recent Ginzburg-Landau theory predictions of a pressure-induced enhancement of $T_c$ in the nematic multicomponent $E_u$ state proposed to explain observations of rotational symmetry breaking in doped Bi$_2$Se$_3$ superconductors.Comment: 5 pages, 5 figure

Collapse of the vortex-lattice inductance and shear modulus at the melting transition in untwinned YBa2Cu3O7\rm YBa_2Cu_3O_7

The complex resistivity $\hat{\rho}(\omega)$ of the vortex lattice in an untwinned crystal of 93-K $\rm YBa_2Cu_3O_7$ has been measured at frequencies $\omega/2\pi$ from 100 kHz to 20 MHz in a 2-Tesla field $\bf H\parallel c$, using a 4-probe RF transmission technique that enables continuous measurements versus $\omega$ and temperature $T$. As $T$ is increased, the inductance ${\cal L}_s(\omega) ={\rm Im} \hat{\rho}(\omega)/ \omega$ increases steeply to a cusp at the melting temperature $T_m$, and then undergoes a steep collapse consistent with vanishing of the shear modulus $c_{66}$. We discuss in detail the separation of the vortex-lattice inductance from the `volume' inductance, and other skin-depth effects. To analyze the spectra, we consider a weakly disordered lattice with a low pin density. Close fits are obtained to $\rho_1(\omega)$ over 2 decades in $\omega$. Values of the pinning parameter $\kappa$ and shear modulus $c_{66}$ obtained show that $c_{66}$ collapses by over 4 decades at $T_m$, whereas $\kappa$ remains finite.Comment: 11 pages, 8 figures, Phys. Rev. B, in pres

Pluri-Canonical Models of Supersymmetric Curves

This paper is about pluri-canonical models of supersymmetric (susy) curves. Susy curves are generalisations of Riemann surfaces in the realm of super geometry. Their moduli space is a key object in supersymmetric string theory. We study the pluri-canonical models of a susy curve, and we make some considerations about Hilbert schemes and moduli spaces of susy curves.Comment: To appear in the proceedings of the intensive period "Perspectives in Lie Algebras", held at the CRM Ennio De Giorgi, Pisa, Italy, 201