840 research outputs found
A predictive model of energy savings from top of rail friction control
In this paper the authors present a predictive model of train energy requirements due to the application of a top of rail friction modifier (TOR-FM) versus dry wheel / rail conditions. Using the VAMPIRE® Pro simulation package, train energy requirements are modeled for two sets of TOR-FM frictional conditions, one using full Kalker coefficients and the other by using a Kalker factor of 18%. Both scenarios use a top of rail saturated coefficient of friction of 0.35. Under both TOR-FM frictional conditions, train energy savings are shown for complete laps of the Transportation Technology Center Inc.’s (TTCI) Transit Test Track (TTT) loop, and also when isolating only the tangent section of the loop. However, the magnitude of energy savings varies greatly depending on the Kalker coefficient factor used, highlighting the need to model this relationship as accurately as possible. These simulation results are compared with data obtained from a field study, in which train energy savings of 5.3% (lap) and 7.8% (tangent) are shown due to the application of TOR-FM
Identification of indirect new physics effects at e^+e^- colliders: the large extra dimensions case
We discuss indirect manifestations of graviton exchange, predicted by large
extra dimensions, in fermion-pair production at a high-energy e^+e^- collider.
By means of specifically defined asymmetries among integrated angular
distributions, the graviton exchange signal can be cleanly distinguished from
the effects of either vector-vector contact interactions or heavy scalar
exchanges. The role of initial electron and positron beams polarization is also
discussed. The method is applied to a quantitative assessment of the
sensitivity to the mass cut-off parameter M_H of the KK graviton tower in the
ADD scenario, and of the potential identification reach of this mechanism
obtainable at the currently planned Linear Collider.Comment: 21 pages, 11 figure
Statistical uncertainty in quantum optical photodetection measurements
We present a complete statistical analysis of quantum optical measurement
schemes based on photodetection. Statistical distributions of quantum
observables determined from a finite number of experimental runs are
characterized with the help of the generating function, which we derive using
the exact statistical description of raw experimental outcomes. We use the
developed formalism to point out that the statistical uncertainty results in
substantial limitations of the determined information on the quantum state:
though a family of observables characterizing the quantum state can be safely
evaluated from experimental data, its further use to obtain the expectation
value of some operators generates exploding statistical errors. These issues
are discussed using the example of phase-insensitive measurements of a single
light mode. We study reconstruction of the photon number distribution from
photon counting and random phase homodyne detection. We show that utilization
of the reconstructed distribution to evaluate a simple well-behaved observable,
namely the parity operator, encounters difficulties due to accumulation of
statistical errors. As the parity operator yields the Wigner function at the
phase space origin, this example also demonstrates that transformation between
various experimentally determined representations of the quantum state is a
quite delicate matter.Comment: 18 pages REVTeX, 7 figures included using epsf. Few minor corrections
made, clarified conclusion
ABCB1 Overexpression Is a key initiator of resistance to tyrosine kinase inhibitors in CML cell lines
The tyrosine kinase inhibitor (TKI) imatinib has resulted in excellent responses in the majority of Chronic Myeloid Leukaemia (CML) patients; however, resistance is observed in 20-30% of patients. More recently, resistance to the second generation TKIs, nilotinib and dasatinib, has also been observed albeit at a lower incidence. ABCB1 has previously been implicated in TKI export and its overexpression linked to TKI resistance. In this study the dynamics of nilotinib resistance was studied in CML cell lines with particular focus on ABCB1 expression levels during development of resistance. Results revealed ABCB1 overexpression is likely an important initiator of nilotinib resistance in vitro. ABCB1 overexpression was also observed in cell lines as an intermediate step during development of resistance to imatinib and dasatinib in vitro. We conclude that ABCB1 overexpression may provide an initial platform to facilitate development of additional mechanisms for resistance to TKIs. This provides a rationale for investigating this phenomenon in patients undergoing TKI therapy.Laura N. Eadie, Timothy P. Hughes, Deborah L. Whit
Z' signal from the LEP2 data
The many-parametric fit of the LEP2 data on e^+e^-\to e^+e^-, \mu^+\mu^-,
\tau^+\tau^- processes is performed to estimate signals of the Abelian Z'-boson
beyond the standard model. The model-independent relations between the Z'
couplings to the standard model particles allow to describe the Z' effects in
lepton processes by 4 independent parameters. No signal is found by the
complete LEP2 data set, and the 1.3\sigma signal is detected by the fit of the
backward bins. The Z' couplings to the vector and axial-vector lepton currents
are constrained. The comparisons with the one-parameter fits and with the LEP1
experiments are performed.Comment: 6 pages, 2 figures, RevTeX. The paper was completely rewritten. The
errors in the first version were eliminated. The comparison with the LEP1
data is adde
axial form factor from bubble chamber experiments
A careful reanalysis of both Argonne National Laboratory and Brookhaven
National Laboratory data for weak single pion production is done. We consider
deuteron nuclear effects and normalization (flux) uncertainties in both
experiments. We demonstrate that these two sets of data are in good agreement.
For the dipole parametrization of , we obtain , GeV. As an application we present the discussion of
the uncertainty of the neutral current 1 production cross section,
important for the T2K neutrino oscillation experiment.Comment: 16 pages, 8 figures, 2 table
Signals of Z' boson in the Bhabha process within the LEP2 data set
The LEP2 data set on the Bhabha process is analyzed with the aim to detect
the signals of the heavy virtual Z' gauge bosons. The state interacting with
the left-handed standard-model doublets and called the Chiral Z' is
investigated. This particle was introduced already as the low-energy state
allowed by the renormalizability of the model. The contribution of the Chiral
Z' state to the Bhabha process is described by two parameters: the coupling to
electrons and the Z-Z' mixing angle. The sign-definite one-parameter observable
is proposed to measure the Z' coupling to the electron current. The
one-parameter fit of the data shows no signals of the particle. The alternative
two-parameter fit of the differential cross-sections is also performed. It also
shows no Chiral Z' signals. The comparisons with other fits are discussed.Comment: 15 pages, 4 figures. The paper was completely rewritten on the base
of new dat
Maximum likelihood estimation of photon number distribution from homodyne statistics
We present a method for reconstructing the photon number distribution from
the homodyne statistics based on maximization of the likelihood function
derived from the exact statistical description of a homodyne experiment. This
method incorporates in a natural way the physical constraints on the
reconstructed quantities, and the compensation for the nonunit detection
efficiency.Comment: 3 pages REVTeX. Final version, to appear in Phys. Rev. A as a Brief
Repor
Fake symmetry transitions in lattice Dirac spectra
In a recent lattice investigation of Ginsparg-Wilson-type Dirac operators in
the Schwinger model, it was found that the symmetry class of the random matrix
theory describing the small Dirac eigenvalues appeared to change from the
unitary to the symplectic case as a function of lattice size and coupling
constant. We present a natural explanation for this observation in the
framework of a random matrix model, showing that the apparent change is caused
by the onset of chiral symmetry restoration in a finite volume. A transition
from unitary to symplectic symmetry does not occur.Comment: 6 pages, 3 figures, REVTe
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