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A comparison of methods for treatment selection in seamless phase II/III clinical trials incorporating information on short-term endpoints
In an adaptive seamless phase II/III clinical trial interim
analysis data are used for treatment selection, enabling resources to be focussed on comparison of more effective treatment(s) with a control. In this paper we compare two methods recently proposed to enable use of short-term endpoint data for decision-making at the interim analysis. The comparison focusses on the power and the probability of correctly identifying the most promising treatment. We show that the choice of method depends on how well short-term data predict the best treatment, which may be measured by the correlation between treatment effects on short-term and long-term endpoints
The Extended Shapes of Galactic Satellites
We are exploring the extended stellar distributions of Galactic satellite
galaxies and globular clusters. For seven objects studied thus far, the
observed profile departs from a King function at large r, revealing a ``break
population'' of stars. In our sample, the relative density of the ``break''
correlates to the inferred M/L of these objects. We discuss opposing hypotheses
for this trend: (1) Higher M/L objects harbor more extended dark matter halos
that support secondary, bound, stellar ``halos''. (2) The extended populations
around dwarf spheroidals (and some clusters) consist of unbound, extratidal
debris from their parent objects, which are undergoing various degrees of tidal
disruption. In this scenario, higher M/L ratios reflect higher degrees of
virial non-equilibrium in the parent objects, thus invalidating a precept
underlying the use of core radial velocities to obtain masses.Comment: 8 pages, including 2 figures Yale Cosmology Workshop: The Shapes of
Galaxies and Their Halo
Proton Differential Elliptic Flow and the Isospin-Dependence of the Nuclear Equation of State
Within an isospin-dependent transport model for nuclear reactions involving
neutron-rich nuclei, we study the first-order direct transverse flow of protons
and their second-order differential elliptic flow as a function of transverse
momentum. It is found that the differential elliptic flow of mid-rapidity
protons, especially at high transverse momenta, is much more sensitive to the
isospin dependence of the nuclear equation of state than the direct flow.
Origins of these different sensitivities and their implications to the
experimental determination of the isospin dependence of the nuclear equation of
state by using neutron-rich heavy-ion collisions at intermediate energies are
discussed.Comment: 15 pages, 6 figures. Phys. Rev. C (2001) in pres
Neutron-Proton Differential Flow as a Probe of Isospin-Dependence of Nuclear Equation of State
The neutron-proton differential flow is shown to be a very useful probe of
the isospin-dependence of the nuclear equation of state (EOS). This novel
approach utilizes constructively both the isospin fractionation and the nuclear
collective flow as well as their sensitivities to the isospin-dependence of the
nuclear EOS. It also avoids effectively uncertainties associated with other
dynamical ingredients of heavy-ion reactions at intermediate energies.Comment: 10 pages + 3 figures. Phys. Rev. Lett. (2000) in pres
Neutrons from multiplicity-selected Au-Au collisions at 150, 250, 400, and 650 AMeV
We measured neutron triple-differential cross sections from
multiplicity-selected Au-Au collisions at 150, 250, 400, and 650 \AMeV. The
reaction plane for each collision was estimated from the summed transverse
velocity vector of the charged fragments emitted in the collision. We examined
the azimuthal distribution of the triple-differential cross sections as a
function of the polar angle and the neutron rapidity. We extracted the average
in--plane transverse momentum and the normalized
observable , where is the neutron
transverse momentum, as a function of the neutron center-of-mass rapidity, and
we examined the dependence of these observables on beam energy. These
collective flow observables for neutrons, which are consistent with those of
protons plus bound nucleons from the Plastic Ball Group, agree with the
Boltzmann--Uehling--Uhlenbeck (BUU) calculations with a momentum--dependent
interaction. Also, we calculated the polar-angle-integrated maximum azimuthal
anisotropy ratio R from the value of .Comment: 20 LaTeX pages. 11 figures to be faxed on request, send email to
sender's addres
Differential flow in heavy-ion collisions at balance energies
A strong differential transverse collective flow is predicted for the first
time to occur in heavy-ion collisions at balance energies. We also give a novel
explanation for the disappearance of the total transverse collective flow at
the balance energies. It is further shown that the differential flow especially
at high transverse momenta is a useful microscope capable of resolving the
balance energy's dual sensitivity to both the nuclear equation of state and
in-medium nucleon-nucleon cross sections in the reaction dynamics.Comment: Phys. Rev. Lett. (1999) in pres
The importance of initial-final state correlations for the formation of fragments in heavy ion collisions
Using quantum molecular dynamics simulations, we investigate the formation of
fragments in symmetric reactions between beam energies of E=30AMeV and 600AMeV.
After a comparison with existing data we investigate some observables relevant
to tackle equilibration: dsigma/dErat, the double differential cross section
dsigma/pt.dpz.dpt,... Apart maybe from very energetic E>400AMeV and very
central reactions, none of our simulations gives evidence that the system
passes through a state of equilibrium. Later, we address the production
mechanisms and find that, whatever the energy, nucleons finally entrained in a
fragment exhibit strong initial-final state correlations, in coordinate as well
as in momentum space. At high energy those correlations resemble the ones
obtained in the participant-spectator model. At low energy the correlations are
equally strong, but more complicated; they are a consequence of the Pauli
blocking of the nucleon-nucleon collisions, the geometry, and the excitation
energy. Studying a second set of time-dependent variables (radii,
densities,...), we investigate in details how those correlations survive the
reaction especially in central reactions where the nucleons have to pass
through the whole system. It appears that some fragments are made of nucleons
which were initially correlated, whereas others are formed by nucleons
scattered during the reaction into the vicinity of a group of previously
correlated nucleons.Comment: 45 pages text + 20 postscript figures Accepted for publication in
Physical Review
Determination of atomic scattering lengths from measurements of molecular binding energies near Feshbach resonances
We present an analytic model to calculate the atomic scattering length near a
Feshbach resonance from data on the molecular binding energy. Our approach
considers finite-range square-well potentials and can be applied near broad,
narrow, or even overlapping Feshbach resonances. We test our model on Cs
Feshbach molecules. We measure the binding energy using magnetic-field
modulation spectroscopy in a range where one broad and two narrow Feshbach
resonances overlap. From the data we accurately determine the Cs atomic
scattering length and the positions and widths of two particular resonances.Comment: 6 pages, 4 figure
Radial Flow in Au+Au Collisions at E=0.25-1.15 A GeV
A systematic study of energy spectra for light particles emitted at
midrapidity from Au+Au collisions at E=0.25-1.15 A GeV reveals a significant
non-thermal component consistent with a collective radial flow. This component
is evaluated as a function of bombarding energy and event centrality.
Comparisons to Quantum Molecular Dynamics (QMD) and Boltzmann-Uehling-Uhlenbeck
(BUU) models are made for different equations of state.Comment: 10 pages of text and 4 figures (all ps files in a uuencoded package)
Classes of Multiple Decision Functions Strongly Controlling FWER and FDR
This paper provides two general classes of multiple decision functions where
each member of the first class strongly controls the family-wise error rate
(FWER), while each member of the second class strongly controls the false
discovery rate (FDR). These classes offer the possibility that an optimal
multiple decision function with respect to a pre-specified criterion, such as
the missed discovery rate (MDR), could be found within these classes. Such
multiple decision functions can be utilized in multiple testing, specifically,
but not limited to, the analysis of high-dimensional microarray data sets.Comment: 19 page
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