640 research outputs found
Solitary wave solution to Aw-Rascle viscous model of traffic flow
A traveling wave solution to the Aw-Rascle traffic flow model that includes the relaxation and diffusion terms is investigated. The model can be approximated by the well-known Kortweg-de Vries (KdV) equation. A numerical simulation is conducted by the first-order accurate Lax-Friedrichs scheme, which is known for its ability to capture the entropy solution to hyperbolic conservation laws. Periodic boundary conditions are applied to simulate a lengthy propagation, where the profile of the derived KdV solution is taken as the initial condition to observe the change of the profile. The simulation shows good agreement between the approximated KdV solution and the numerical solution.postprin
High-energy scale revival and giant kink in the dispersion of a cuprate superconductor
In the present photoemission study of a cuprate superconductor
Bi1.74Pb0.38Sr1.88CuO6+delta, we discovered a large scale dispersion of the
lowest band, which unexpectedly follows the band structure calculation very
well. The incoherent nature of the spectra suggests that the hopping-dominated
dispersion occurs possibly with the assistance of local spin correlations. A
giant kink in the dispersion is observed, and the complete self-energy
containing all interaction information is extracted for a doped cuprate in the
low energy region. These results recovered significant missing pieces in our
current understanding of the electronic structure of cuprates.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Lett. on May 21, 200
First Observation of and Decays
We have observed new channels for decays with an in the final
state. We study 3-prong tau decays, using the and
\eta\to 3\piz decay modes and 1-prong decays with two \piz's using the
channel. The measured branching fractions are
\B(\tau^{-}\to \pi^{-}\pi^{-}\pi^{+}\eta\nu_{\tau})
=(3.4^{+0.6}_{-0.5}\pm0.6)\times10^{-4} and \B(\tau^{-}\to
\pi^{-}2\piz\eta\nu_{\tau}
=(1.4\pm0.6\pm0.3)\times10^{-4}. We observe clear evidence for
substructure and measure \B(\tau^{-}\to
f_1\pi^{-}\nu_{\tau})=(5.8^{+1.4}_{-1.3}\pm1.8)\times10^{-4}. We have also
searched for production and obtain 90% CL upper limits
\B(\tau^{-}\to \pi^{-}\eta'\nu_\tau)<7.4\times10^{-5} and \B(\tau^{-}\to
\pi^{-}\piz\eta'\nu_\tau)<8.0\times10^{-5}.Comment: 11 page postscript file, postscript file also available through
http://w4.lns.cornell.edu/public/CLN
Search for the Decays B^0 -> D^{(*)+} D^{(*)-}
Using the CLEO-II data set we have searched for the Cabibbo-suppressed decays
B^0 -> D^{(*)+} D^{(*)-}. For the decay B^0 -> D^{*+} D^{*-}, we observe one
candidate signal event, with an expected background of 0.022 +/- 0.011 events.
This yield corresponds to a branching fraction of Br(B^0 -> D^{*+} D^{*-}) =
(5.3^{+7.1}_{-3.7}(stat) +/- 1.0(syst)) x 10^{-4} and an upper limit of Br(B^0
-> D^{*+} D^{*-}) D^{*\pm} D^\mp and
B^0 -> D^+ D^-, no significant excess of signal above the expected background
level is seen, and we calculate the 90% CL upper limits on the branching
fractions to be Br(B^0 -> D^{*\pm} D^\mp) D^+
D^-) < 1.2 x 10^{-3}.Comment: 12 page postscript file also available through
http://w4.lns.cornell.edu/public/CLNS, submitted to Physical Review Letter
Production in Two-Photon Interactions at CLEO
Using the CLEO detector at the Cornell storage ring, CESR, we study
the two-photon production of , making the first
observation of . We present the
cross-section for as a function of
the center of mass energy and compare it to that predicted by
the quark-diquark model.Comment: 10 pages, postscript file also available through
http://w4.lns.cornell.edu/public/CLN
Comparative mortality of hemodialysis patients at for-profit and not-for-profit dialysis facilities in the United States, 1998 to 2003: A retrospective analysis
<p>Abstract</p> <p>Background</p> <p>Concern lingers that dialysis therapy at for-profit (versus not-for-profit) hemodialysis facilities in the United States may be associated with higher mortality, even though 4 of every 5 contemporary dialysis patients receive therapy in such a setting.</p> <p>Methods</p> <p>Our primary objective was to compare the mortality hazards of patients initiating hemodialysis at for-profit and not-for-profit centers in the United States between 1998 and 2003. For-profit status of dialysis facilities was determined after subjects received 6 months of dialysis therapy, and mean follow-up was 1.7 years.</p> <p>Results</p> <p>Of the study population (<it>N </it>= 205,076), 79.9% were dialyzed in for-profit facilities after 6 months of dialysis therapy. Dialysis at for-profit facilities was associated with higher urea reduction ratios, hemoglobin levels (including levels above 12 and 13 g/dL [120 and 130 g/L]), epoetin doses, and use of intravenous iron, and less use of blood transfusions and lower proportions of patients on the transplant waiting-list (<it>P </it>< 0.05). Patients dialyzed at for-profit and at not-for-profit facilities had similar mortality risks (adjusted hazards ratio 1.02, 95% CI 0.99–1.06, <it>P </it>= 0.143).</p> <p>Conclusion</p> <p>While hemodialysis treatment at for-profit and not-for-profit dialysis facilities is associated with different patterns of clinical benchmark achievement, mortality rates are similar.</p
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