3,548 research outputs found
Higher-order vortex solitons, multipoles, and supervortices on a square optical lattice
We predict new generic types of vorticity-carrying soliton complexes in a
class of physical systems including an attractive Bose-Einstein condensate in a
square optical lattice (OL) and photonic lattices in photorefractive media. The
patterns include ring-shaped higher-order vortex solitons and supervortices.
Stability diagrams for these patterns, based on direct simulations, are
presented. The vortex ring solitons are stable if the phase difference \Delta
\phi between adjacent solitons in the ring is larger than \pi/2, while the
supervortices are stable in the opposite case, \Delta \phi <\pi /2. A
qualitative explanation to the stability is given.Comment: 9 pages, 4 figure
Superconductivity in CVD Diamond Thin Film Well-Above Liquid Helium Temperature
Diamond has always been adored as a jewel. Even more fascinating is its
outstanding physical properties; it is the hardest material known in the world
with the highest thermal conductivity. Meanwhile, when we turn to its
electrical properties, diamond is a rather featureless electrical insulator.
However, with boron doping, it becomes a p-type semiconductor, with boron
acting as a charge acceptor. Therefore the recent news of superconductivity in
heavily boron-doped diamond synthesized by high pressure sintering was received
with considerable surprise. Opening up new possibilities for diamond-based
electrical devices, a systematic investigation of these phenomena clearly needs
to be achieved. Here we show unambiguous evidence of superconductivity in a
diamond thin film deposited by a chemical vapor deposition (CVD) method.
Furthermore the onset of the superconducting transition is found to be 7.4K,
which is higher than the reported value in ref(7) and well above helium liquid
temperature. This finding establishes the superconductivity to be a universal
property of boron-doped diamond, demonstrating that device application is
indeed a feasible challenge.Comment: 6 pages, 3 figure
Microscopic Evidence for Evolution of Superconductivity by Effective Carrier Doping in Boron-doped Diamond:11B-NMR study
We have investigated the superconductivity discovered in boron (B)-doped
diamonds by means of 11B-NMR on heteroepitaxially grown (111) and (100) films.
11B-NMR spectra for all of the films are identified to arise from the
substitutional B(1) site as single occupation and lower symmetric B(2) site
substituted as boron+hydrogen(B+H) complex, respectively. A clear evidence is
presented that the effective carriers introduced by B(1) substitution are
responsible for the superconductivity, whereas the charge neutral B(2) sites
does not offer the carriers effectively. The result is also corroborated by the
density of states deduced by 1/T1T measurement, indicating that the evolution
of superconductivity is driven by the effective carrier introduced by
substitution at B(1) site.Comment: 4 pages, 6 figures, to be published in Phys. Rev. B (Brief report
Nondegenerate Super-Anti-de Sitter Algebra and a Superstring Action
We construct an Anti-de Sitter(AdS) algebra in a nondegenerate superspace.
Based on this algebra we construct a covariant kappa-symmetric superstring
action, and we examine its dynamics: Although this action reduces to the usual
Green-Schwarz superstring action in flat limit, the auxiliary fermionic
coordinates of the nondegenerate superspace becomes dynamical in the AdS
background.Comment: Latex, 12 pages, explanations added, version to be published in Phys.
Rev.
Gap solitons in Bragg gratings with a harmonic superlattice
Solitons are studied in a model of a fiber Bragg grating (BG) whose local
reflectivity is subjected to periodic modulation. The superlattice opens an
infinite number of new bandgaps in the model's spectrum. Averaging and
numerical continuation methods show that each gap gives rise to gap solitons
(GSs), including asymmetric and double-humped ones, which are not present
without the superlattice.Computation of stability eigenvalues and direct
simulation reveal the existence of completely stable families of fundamental
GSs filling the new gaps - also at negative frequencies, where the ordinary GSs
are unstable. Moving stable GSs with positive and negative effective mass are
found too.Comment: 7 pages, 3 figures, submitted to EP
Quantum switches and quantum memories for matter-wave lattice solitons
We study the possibility of implementing a quantum switch and a quantum
memory for matter wave lattice solitons by making them interact with
"effective" potentials (barrier/well) corresponding to defects of the optical
lattice. In the case of interaction with an "effective" potential barrier, the
bright lattice soliton experiences an abrupt transition from complete
transmission to complete reflection (quantum switch) for a critical height of
the barrier. The trapping of the soliton in an "effective" potential well and
its release on demand, without loses, shows the feasibility of using the system
as a quantum memory. The inclusion of defects as a way of controlling the
interactions between two solitons is also reported
M-theory on a Time-dependent Plane-wave
We propose a matrix model on a homogeneous plane-wave background with 20
supersymmetries. This background is anti-Mach type and is equivalent to the
time-dependent background. We study supersymmetries in this theory and
calculate the superalgebra. The vacuum energy of the abelian part is also
calculated. In addition we find classical solutions such as graviton solution,
fuzzy sphere and hyperboloid.Comment: 19pages, no figures, LaTeX, JHEP3.cl
Clinical implications of expression of vascular endothelial growth factor in metastatic lesions of ovarian cancers
Vascular endothelial growth factor (VEGF) has been identified as an important factor for tumour angiogenesis, which is essential for the growth, invasion and metastasis of solid tumours. Significantly increased VEGF level from the primary tumour to the metastatic lesion of ovarian cancers was found in 8 of 30 cases. The 24-month survival rate of the patients with significantly increased VEGF level was extremely poor (0/8 = 0%) in comparison with that of patients with no change in the level (15/22 = 68%) from the primary tumour to the metastatic lesion. This indicates that VEGF may contribute to the advancement of metastatic lesions, and that VEGF level in metastatic lesions may be a prognostic indicator. © 2001 Cancer Research Campaign http://www.bjcancer.co
Naturally Arising Human CD4 T-Cells That Recognize Islet Autoantigens and Secrete Interleukin-10 Regulate Proinflammatory T-Cell Responses via Linked Suppression
OBJECTIVE—Regulatory T-cells (Tregs) recognizing islet au-toantigens are proposed as a key mechanism in the maintenance of self-tolerance and protection from type 1 diabetes. To date, however, detailed information on such cells in humans, and insight into their mechanisms of action, has been lacking. We previously reported that a subset of CD4 T-cells secreting high levels of the immunosuppressive cytokine interleukin-10 (IL-10) is significantly associated with late onset of type 1 diabetes and is constitutively present in a majority of nondiabetic individuals. Here, we test the hypothesis that these T-cells represent a naturally generated population of Tregs capable of suppressing proinflammatory T-cell responses. RESEARCH DESIGN AND METHODS—We isolated and cloned islet-specific IL-10–secreting CD4 T-cells from nondia-betic individuals after brief ex vivo exposure to islet autoantigen
Subnormal operators regarded as generalized observables and compound-system-type normal extension related to su(1,1)
In this paper, subnormal operators, not necessarily bounded, are discussed as
generalized observables. In order to describe not only the information about
the probability distribution of the output data of their measurement but also a
framework of their implementations, we introduce a new concept
compound-system-type normal extension, and we derive the compound-system-type
normal extension of a subnormal operator, which is defined from an irreducible
unitary representation of the algebra su(1,1). The squeezed states are
characterized as the eigenvectors of an operator from this viewpoint, and the
squeezed states in multi-particle systems are shown to be the eigenvectors of
the adjoints of these subnormal operators under a representation. The affine
coherent states are discussed in the same context, as well.Comment: LaTeX with iopart.cls, iopart12.clo, iopams.sty, The previous version
has some mistake
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