Scanning SQUID Microscope Study of Vortex Polygons and Shells in Weak Pinning Disks of an Amorphous Superconducting Film

Direct observation of vortices by the scanning SQUID microscopy was made on large mesoscopic disks of an amorphous MoGe thin film. Owing to the weak pinning nature of the amorphous film, vortices are able to form geometry induced, (quasi-)symmetric configurations of polygons and concentric shells in the large disks. Systematic measurements made on selected disks allow us to trace not only how the vortex pattern evolves with magnetic field, but also how the vortex polygons change in size and rotate with respect to the disk center. The results are in good agreement with theoretical considerations for mesoscopic disks with sufficiently large diameter. A series of vortex images obtained in a disk with a pinning site reveals a unique line symmetry in vortex configurations, resulting in modifications of the shell filling rule and the magic number.Comment: 8 pages, 5 figures. Phys Rev B 82 014501 (2010

In vitro characterization of cells derived from chordoma cell line U-CH1 following treatment with X-rays, heavy ions and chemotherapeutic drugs

<p>Abstract</p> <p>Background</p> <p>Chordoma, a rare cancer, is usually treated with surgery and/or radiation. However, very limited characterizations of chordoma cells are available due to a minimal availability (only two lines validated by now) and the extremely long doubling time. In order to overcome this situation, we successfully derived a cell line with a shorter doubling time from the first validated chordoma line U-CH1 and obtained invaluable cell biological data.</p> <p>Method</p> <p>After isolating a subpopulation of U-CH1 cells with a short doubling time (U-CH1-N), cell growth, cell cycle distribution, DNA content, chromosome number, p53 status, and cell survival were examined after exposure to X-rays, heavy ions, camptothecin, mitomycin C, cisplatin and bleocin. These data were compared with those of HeLa (cervical cancer) and U87-MG (glioblastoma) cells.</p> <p>Results</p> <p>The cell doubling times for HeLa, U87-MG and U-CH1-N were approximately 18 h, 24 h and 3 days respectively. Heavy ion irradiation resulted in more efficient cell killing than x-rays in all three cell lines. Relative biological effectiveness (RBE) at 10% survival for U-CH1-N was about 2.45 for 70 keV/μm carbon and 3.86 for 200 keV/μm iron ions. Of the four chemicals, bleocin showed the most marked cytotoxic effect on U-CH1-N.</p> <p>Conclusion</p> <p>Our data provide the first comprehensive cellular characterization using cells of chordoma origin and furnish the biological basis for successful clinical results of chordoma treatment by heavy ions.</p

Vortex pinning in Au-irradiated FeSe0.4Te0.6 crystals from the static limit to gigahertz frequencies

Fe(Se,Te) is one of the simplest compounds of iron-based superconductors, but it shows a variety of vortex pinning phenomena both in thin-film and single-crystal forms. These properties are particularly important in light of its potential for applications ranging from the development of coated conductors for high-field magnets to topological quantum computation exploiting the Majorana particles found in the superconducting vortex cores. In this paper, we characterize the pinning properties of FeSe 0.4 Te 0.6 single crystals, both pristine and Au-irradiated, with a set of characterization techniques ranging from the static limit to the GHz frequency range by using dc magnetometry, ac susceptibility measurements of both the fundamental and the third harmonic signals, and by microwave coplanar waveguide resonator measurements of London and Campbell penetration depths. We observed signatures of single vortex pinning that can be modeled by a parabolic pinning potential, dissipation caused by flux creep, and a general enhancement of the critical current density after 320 MeV Au ion irradiation

Sub-Arcsecond Imaging of 3C123:108-GHz Continuum Observations of the Radio Hotspots

We present the results of sub-arcsecond 108 GHz continuum interferometric observations toward the radio luminous galaxy 3C123. Using multi-array observations, we utilize the high u,v dynamic range of the BIMA millimeter array to sample fully spatial scales ranging from 0.5" to 50". This allows us to make one-to-one comparisons of millimeter-wavelength emission in the radio lobes and hotspots to VLA centimeter observations at 1.4, 4.9, 8.4, and 15 GHz. At 108 GHz, the bright, eastern double hotspot in the southern lobe is resolved. This is only the second time that a multiple hotspot region has been resolved in the millimeter regime. We model the synchrotron spectra of the hotspots and radio lobes using simple broken power-law models with high energy cutoffs, and discuss the hotspot spectra and their implications for models of multiple hotspot formation.Comment: 16 pages, 3 Figures, ApJ Accepte

Measurement of the π−\pi^- decay width of Λ5^5_\LambdaHe

We have precisely measured $\Lambda \to p\pi^-$ decay width of \5LHe and demonstrated significantly larger $\alpha$ -$\Lambda$ overlap than expected from the central repulsion $\alpha$-$\Lambda$ potential, which is derived from YNG \Lambda$-nucleon interaction.Comment: 4 pages, 3 figure

Classification and realizations of type III factor representations of Cuntz-Krieger algebras associated with quasi-free states

We completely classify type III factor representations of Cuntz-Krieger algebras associated with quasi-free states up to unitary equivalence. Furthermore, we realize these representations on concrete Hilbert spaces without using GNS construction. Free groups and their type ${\rm II}_{1}$ factor representations are used in these realizations.Comment: 11 page

Proton asymmetry in non-mesonic weak decay of light hypernuclei

We have obtained the decay asymmetry parameters in non-mesonic weak decay of polarized Lambda-hypernuclei by measuring the proton asymmetry. The polarized Lambda-hypernuclei, 5_Lambda-He, 12_Lambda-C, and 11_Lambda-B, were produced in high statistics via the (pi^+,k^+) reaction at 1.05 GeV/c in the forward angles. Preliminary analysis shows that the decay asymmetry parameters are very small for these s-shell and p-shell hypernuclei.Comment: 4pages, 4figures, International Conference on Hypernuclear and Strange Particle Physics (HYP2003

Gamma-Ray Spectroscopy of Λ16^{16}_\LambdaO and Λ15^{15}_\LambdaN Hypernuclei via the 16^{16}O(K−,π−)(K^-, \pi^-) reaction

he bound-state level structures of the $^{16}_{\Lambda}$O and $^{15}_{\Lambda}$N hypernuclei were studied by $\gamma$-ray spectroscopy using a germanium detector array (Hyperball) via the $^{16}$O ($K^-, \pi^- \gamma$) reaction. A level scheme for $^{16}_{\Lambda}$O was determined from the observation of three $\gamma$-ray transitions from the doublet of states ($2^-$,$1^-$) at $\sim 6.7$ MeV to the ground-state doublet ($1^-$,$0^-$). The $^{15}_{\Lambda}$N hypernuclei were produced via proton emission from unbound states in $^{16}_{\Lambda}$O . Three $\gamma$ -rays were observed and the lifetime of the $1/2^+;1$ state in $^{15}_{\Lambda}$N was measured by the Doppler shift attenuation method. By comparing the experimental results with shell-model calculations, the spin-dependence of the $\Lambda N$ interaction is discussed. In particular, the measured $^{16}_{\Lambda}$O ground-state doublet spacing of 26.4 $\pm$ 1.6 $\pm$ 0.5 keV determines a small but nonzero strength of the $\Lambda N$ tensor interaction.Comment: 22 pages, 17 figure