921 research outputs found
The diagnosis of bladder tumours
The commonest presenting symptom of a bladder tumour is haematuria, which may be repeated but frequently occurs on one occasion only. In males over the age of 40, about half the cases are due to neoplasm. It is therefore obvious that haematuria, however slight, should always be considered seriously. Thus the first essential in diagnosis is the proper investigation of all cases of haematuria. This phase is usually the responsibility of the general practitioner
Scaling of the 3P0 strength in heavy meson strong decays
The phenomenological 3P0 decay model has been extensively applied to
calculate meson strong decays. The strength \gamma\ of the decay interaction is
regarded as a free flavor independent constant and is fitted to the data. We
calculate through the 3P0 model the total strong decay widths of the mesons
which belong to charmed, charmed-strange, hidden charm and hidden bottom
sectors. The wave function of the mesons involved in the strong decays are
given by a constituent quark model that describes well the meson phenomenology
from the light to the heavy quark sector. A global fit of the experimental data
shows that, contrarily to the usual wisdom, the \gamma\ depends on the reduced
mass of the quark-antiquark pair in the decaying meson. With this
scale-dependent strength \gamma, we are able to predict the decay width of
orbitally excited B mesons not included in the fit.Comment: 7 pages, 5 tables, 2 figure
Lattice calculation of hybrid mesons with improved Kogut-Susskind fermions
We report on a lattice determination of the mass of the exotic
hybrid meson using an improved Kogut-Susskind action. Results from both
quenched and dynamical quark simulations are presented. We also compare with
earlier results using Wilson quarks at heavier quark masses. The results on
lattices with three flavors of dynamical quarks show effects of sea quarks on
the hybrid propagators which probably result from coupling to two meson states.
We extrapolate the quenched results to the physical light quark mass to allow
comparison with experimental candidates for the hybrid meson. The
lattice result remains somewhat heavier than the experimental result, although
it may be consistent with the .Comment: 24 pages, 12 figures. Replaced to match published versio
The discontinuous nature of chromospheric activity evolution
Chromospheric activity has been thought to decay smoothly with time and,
hence, to be a viable age indicator. Measurements in solar type stars in open
clusters seem to point to a different conclusion: chromospheric activity
undergoes a fast transition from Hyades level to that of the Sun after about 1
Gyr of main--sequence lifetime and any decaying trend before or after this
transition must be much less significant than the short term variations.Comment: 6 pages, 1 figure, to be published in Astrophysics and Space Scienc
Measurements of Scintillation Efficiency and Pulse-Shape for Low Energy Recoils in Liquid Xenon
Results of observations of low energy nuclear and electron recoil events in
liquid xenon scintillator detectors are given. The relative scintillation
efficiency for nuclear recoils is 0.22 +/- 0.01 in the recoil energy range 40
keV - 70 keV. Under the assumption of a single dominant decay component to the
scintillation pulse-shape the log-normal mean parameter T0 of the maximum
likelihood estimator of the decay time constant for 6 keV < Eee < 30 keV
nuclear recoil events is equal to 21.0 ns +/- 0.5 ns. It is observed that for
electron recoils T0 rises slowly with energy, having a value ~ 30 ns at Eee ~
15 keV. Electron and nuclear recoil pulse-shapes are found to be well fitted by
single exponential functions although some evidence is found for a double
exponential form for the nuclear recoil pulse-shape.Comment: 11 pages, including 5 encapsulated postscript figure
Matching Spherical Dust Solutions to Construct Cosmological Models
Conditions for smooth cosmological models are set out and applied to
inhomogeneous spherically symmetric models constructed by matching together
different Lemaitre-Tolman-Bondi solutions to the
Einstein field equations. As an illustration the methods are applied to a
collapsing dust sphere in a curved background. This describes a region which
expands and then collapses to form a black hole in an
Einstein de Sitter background. We show that in all such models if there is no
vacuum region then the singularity must go on accreting matter for an infinite
LTB time.Comment: 13 pages, Revtex; to appear Gen. Rel. Gra
Resonant transmission through an open quantum dot
We have measured the low-temperature transport properties of a quantum dot
formed in a one-dimensional channel. In zero magnetic field this device shows
quantized ballistic conductance plateaus with resonant tunneling peaks in each
transition region between plateaus. Studies of this structure as a function of
applied perpendicular magnetic field and source-drain bias indicate that
resonant structure deriving from tightly bound states is split by Coulomb
charging at zero magnetic field.Comment: To be published in Phys. Rev. B (1997). 8 LaTex pages with 5 figure
Improved perturbation theory in the vortex liquids state of type II superconductors
We develop an optimized perturbation theory for the Ginzburg - Landau
description of thermal fluctuations effects in the vortex liquids. Unlike the
high temperature expansion which is asymptotic, the optimized expansion is
convergent. Radius of convergence on the lowest Landau level is in
2D and in 3D. It allows a systematic calculation of magnetization
and specific heat contributions due to thermal fluctuations of vortices in
strongly type II superconductors to a very high precision. The results are in
good agreement with existing Monte Carlo simulations and experiments.
Limitations of various nonperturbative and phenomenological approaches are
noted. In particular we show that there is no exact intersection point of the
magnetization curves both in 2D and 3D.Comment: 24 pages, 9 figure
A Study of the \eta \pi^{0} Spectrum and Search for a J^{PC} = 1^{-+} Exotic Meson
A partial wave analysis (PWA) of the of the system (where ) produced in the charge exchange reaction at an incident momentum of 18 GeV is presented as a function of
invariant mass, , and momentum transfer squared,
, from the incident to the outgoing system. , and waves were included in the PWA. The
and states are clearly observed in the overall
effective mass distribution as well as in the amplitudes associated with
wave and waves respectively after partial wave decomposition. The observed
distributions in moments (averages of spherical harmonics) were compared to the
results from the PWA and the two are consistent. The distribution in
for individual waves associated with natural and
unnatural parity exchange in the -channel are consistent with Regge
phenomenology. Of particular interest in this study is the wave since this
leads to an exotic for the system. A wave is
present in the data, however attempts to describe the mass dependence of the
amplitude and phase motion with respect to the wave as a Breit-Wigner
resonance are problematic. This has implications regarding the existence of a
reported exotic meson decaying into with a mass
near 1.4 GeV.Comment: 19 pages, 29 figures, to appear in Phys. Rev.
Observation of a New J(PC)=1(+-) Isoscalar State in the Reaction Pi- Proton -> Omega Eta Neutron at 18 GeV/c
Results are presented on a partial wave analysis of the Omega Eta final state
produced in Pi- Proton interactions at 18 GeVc where Omega -> Pi+ Pi- Pi0, Pi0
-> 2 Gammas, and Eta -> 2 Gammas. We observe the previously unreported decay
mode Omega(1650) -> Omega Eta and a new 1(+-) meson state h1(1595) with a mass
M=1594(15)(+10)(-60) MeV/c^2 and a width Gamma=384(60)(+70)(-100) MeV/c^2. The
h1(1595) state exhibits resonant-like phase motion relative to the Omega(1650).Comment: Submitted to Physics Letters B Eight total pages including 11 figures
and 1 tabl
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