457 research outputs found
Magnetic fullerenes inside single-wall carbon nanotubes
C59N magnetic fullerenes were formed inside single-wall carbon nanotubes by
vacuum annealing functionalized C59N molecules encapsulated inside the tubes. A
hindered, anisotropic rotation of C59N was deduced from the temperature
dependence of the electron spin resonance spectra near room temperature.
Shortening of spin-lattice relaxation time, T_1, of C59N indicates a reversible
charge transfer toward the host nanotubes above K. Bound C59N-C60
heterodimers are formed at lower temperatures when C60 is co-encapsulated with
the functionalized C59N. In the 10-300 K range, T_1 of the heterodimer shows a
relaxation dominated by the conduction electrons on the nanotubes
Pattern forming instability induced by light in pure and dye-doped nematic liquid crystals
We study theoretically the instabilities induced by a linearly polarized
ordinary light wave incident at a small oblique angle on a thin layer of
homeotropically oriented nematic liquid crystal with special emphasis on the
dye-doped case. The spatially periodic Hopf bifurcation that occurs as the
secondary instability after the stationary Freedericksz transition is analyzed.Comment: 8 pages, 7 figures, LaTeX, accepted to Phys. Rev.
Routine immunofluorescent and histochemical analysis of bone marrow involvement of lymphoma/leukaemia: the use of cryostat sections.
Enzyme histochemical and immunohistological (immuno-fluorescence and -peroxidase) techniques have been routinely used for investigating over 70 normal and pathological bone marrow samples. This recently standardized diagnostic procedure is very quick and can be performed in a few hours. In 6 cases the clinical diagnosis of leukaemia/lymphoma has become apparent only after the immunohistological analysis of the bone marrow. In 6 other cases the information about the staging of B cell malignancies was superior in the frozen biopsies to the paraffin embedded preparations. Amongst many other features the monoclonality of B CLL/lymphomas, the special features of B CLL infiltrates (RFA-1+, Leu-1+, HLA-DR+, SmIg+), follicular lymphoma deposits (containing follicular dendritic cells) and non-T, non-B acute lymphoblastic leukaemic blasts (terminal transferase+, HLA-DR+) as well as the sometimes conspicuous presence of infiltrating normal T cells could be clearly and reproducibly demonstrated
Orientational instabilities in nematics with weak anchoring under combined action of steady flow and external fields
We study the homogeneous and the spatially periodic instabilities in a
nematic liquid crystal layer subjected to steady plane {\em Couette} or {\em
Poiseuille} flow. The initial director orientation is perpendicular to the flow
plane. Weak anchoring at the confining plates and the influence of the external
{\em electric} and/or {\em magnetic} field are taken into account. Approximate
expressions for the critical shear rate are presented and compared with
semi-analytical solutions in case of Couette flow and numerical solutions of
the full set of nematodynamic equations for Poiseuille flow. In particular the
dependence of the type of instability and the threshold on the azimuthal and
the polar anchoring strength and external fields is analysed.Comment: 12 pages, 6 figure
Electronic density of states derived from thermodynamic critical field curves for underdoped La-Sr-Cu-O
Thermodynamic critical field curves have been measured for
over the full range of carrier concentrations
where superconductivity occurs in order to determine changes in the normal
state density of states with carrier concentration. There is a substantial
window in the plane where the measurements are possible because the
samples are both thermodynamically reversible and the temperature is low enough
that vortex fluctuations are not important. In this window, the data fit
Hao-Clem rather well, so this model is used to determine and
for each temperature and carrier concentration. Using N(0) and the ratio of the
energy gap to transition temperature, , as fitting
parameters, the curves give over the
whole range of . Values of N(0) remain rather constant in the optimum-doped
and overdoped regime, but drops quickly toward zero in the underdoped regime.
Anisotropy of superconducting MgB2 as seen in electron spin resonance and magnetization data
We have observed the conduction electron spin resonance (CESR) in fine
powders of MgB2 both in the superconducting and normal states. The Pauli
susceptibility is chi_s=2.0*10^{-5} emu/mole in the temperature range of 450 to
600 K. The spin relaxation rate has an anomalous temperature dependence. The
CESR measured below T_c at several frequencies suggests that MgB_2 is a
strongly anisotropic superconductor with the upper critical field, H_c2,
ranging between 2 and 16 T. The high-field reversible magnetization data of a
randomly oriented powder sample are well described assuming that MgB_2 is an
anisotropic superconductor with H_c2^{ab} / H_{c2}^{c} \approx 6--9.Comment: 4 pages, 4 eps figure
Spatial point process theory
No abstract
Non-magnetic impurities in two dimensional superconductors
A numerical approach to disordered 2D superconductors described by BCS mean
field theory is outlined. The energy gap and the superfluid density at zero
temperature and the quasiparticle density of states are studied. The method
involves approximate self-consistent solutions of the Bogolubov-deGennes
equations on finite square lattices. Where comparison is possible, the results
of standard analytic approaches to this problem are reproduced. Detailed
modeling of impurity effects is practical using this approach. The {\it range}
of the impurity potential is shown to be of {\it quantitative importance} in
the case of strong potential scatterers. We discuss the implications for
experiments, such as the rapid suppression of superconductivity by Zn doping in
Copper-Oxide superconductors.Comment: 16 pages, latex, 8 figures( available upon request
The GRA Beam-Splitter Experiments and Particle-Wave Duality of Light
Grangier, Roger and Aspect (GRA) performed a beam-splitter experiment to
demonstrate the particle behaviour of light and a Mach-Zehnder interferometer
experiment to demonstrate the wave behaviour of light. The distinguishing
feature of these experiments is the use of a gating system to produce near
ideal single photon states. With the demonstration of both wave and particle
behaviour (in two mutually exclusive experiments) they claim to have
demonstrated the dual particle-wave behaviour of light and hence to have
confirmed Bohr's principle of complementarity. The demonstration of the wave
behaviour of light is not in dispute. But we want to demonstrate, contrary to
the claims of GRA, that their beam-splitter experiment does not conclusively
confirm the particle behaviour of light, and hence does not confirm
particle-wave duality, nor, more generally, does it confirm complementarity.
Our demonstration consists of providing a detailed model based on the Causal
Interpretation of Quantum Fields (CIEM), which does not involve the particle
concept, of GRA's which-path experiment. We will also give a brief outline of a
CIEM model for the second, interference, GRA experiment.Comment: 24 pages, 4 figure
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