641 research outputs found
A simulation experiment for comparing tests of regression transformation
AbstractAn example is given of the use of graphical methods in the analysis of a simulation experiment. Comments are made on the design of such studies
-optimal saturated designs: a simulation study
In this work we focus on saturated -optimal designs. Using recent results,
we identify -optimal designs with the solutions of an optimization problem
with linear constraints. We introduce new objective functions based on the
geometric structure of the design and we compare them with the classical
-efficiency criterion. We perform a simulation study. In all the test cases
we observe that designs with high values of -efficiency have also high
values of the new objective functions.Comment: 8 pages. Preliminary version submitted to the 7th IWS Proceeding
Quark gap equation within the analytic approach to QCD
The compatibility between the QCD analytic invariant charge and chiral
symmetry breaking is examined in detail. The coupling in question incorporates
asymptotic freedom and infrared enhancement into a single expression, and
contains only one adjustable parameter with dimension of mass. When inserted
into the standard form of the quark gap-equation it gives rise to solutions
displaying singular confining behavior at the origin. By relating these
solutions to the pion decay constant, a rough estimate of about 880 MeV is
obtained for the aforementioned mass-scale.Comment: Talk given by J.P. at 12th International QCD Conference (QCD05), 4 -
9 July 2005, Montpellier, France; 4 pages, 3 figure
D-optimal designs via a cocktail algorithm
A fast new algorithm is proposed for numerical computation of (approximate)
D-optimal designs. This "cocktail algorithm" extends the well-known vertex
direction method (VDM; Fedorov 1972) and the multiplicative algorithm (Silvey,
Titterington and Torsney, 1978), and shares their simplicity and monotonic
convergence properties. Numerical examples show that the cocktail algorithm can
lead to dramatically improved speed, sometimes by orders of magnitude, relative
to either the multiplicative algorithm or the vertex exchange method (a variant
of VDM). Key to the improved speed is a new nearest neighbor exchange strategy,
which acts locally and complements the global effect of the multiplicative
algorithm. Possible extensions to related problems such as nonparametric
maximum likelihood estimation are mentioned.Comment: A number of changes after accounting for the referees' comments
including new examples in Section 4 and more detailed explanations throughou
Numerical Study of the Ghost-Gluon Vertex in Landau gauge
We present a numerical study of the ghost-gluon vertex and of the
corresponding renormalization function \widetilde{Z}_1(p^2) in minimal Landau
gauge for SU(2) lattice gauge theory. Data were obtained for three different
lattice volumes (V = 4^4, 8^4, 16^4) and for three lattice couplings \beta =
2.2, 2.3, 2.4. Gribov-copy effects have been analyzed using the so-called
smeared gauge fixing. We also consider two different sets of momenta (orbits)
in order to check for possible effects due to the breaking of rotational
symmetry. The vertex has been evaluated at the asymmetric point (0;p,-p) in
momentum-subtraction scheme. We find that \widetilde{Z}_1(p^2) is approximately
constant and equal to 1, at least for momenta p > ~ 1 GeV. This constitutes a
nonperturbative verification of the so-called nonrenormalization of the Landau
ghost-gluon vertex. Finally, we use our data to evaluate the running coupling
constant \alpha_s(p^2).Comment: 19 pages, 6 figures, 9 tables, using axodraw.sty; minor modifications
in the abstract, introduction and conclusion
The Cytomegalovirus gB/MF59 vaccine candidate induces antibodies against an antigenic domain controlling cell-to-cell spread
Vaccination against human cytomegalovirus (CMV) infection remains high priority. A recombinant form of a protein essential for CMV entry, glycoprotein B (gB), demonstrated partial protection in a clinical trial (NCT00299260) when delivered with the MF59 adjuvant. Although the antibody titre against gB correlated with protection poor neutralising responses against the 5 known antigenic domains (AD) of gB were evident. Here, we show that vaccination of CMV seronegative patients induces an antibody response against a region of gB we term AD-6. Responses to the polypeptide AD-6 are detected inâ>70% of vaccine recipients yet inâ<5% of naturally infected people. An AD-6 antibody binds to gB and to infected cells but not the virion directly. Consistent with this, the AD-6 antibody is non-neutralising but, instead, prevents cell-cell spread of CMV in vitro. The discovery of AD-6 responses has the potential to explain part of the protection mediated by gB vaccines against CMV following transplantation
Spectral and Transport Properties of d-Wave Superconductors With Strong Impurities
One of the remarkable features of disordered d-wave superconductors is strong
sensitivity of long range properties to the microscopic realization of the
disorder potential. Particularly rich phenomenology is observed for the --
experimentally relevant -- case of dilute distributions of isolated impurity
centers. Building on earlier diagrammatic analyses, the present paper derives
and analyses a low energy effective field theory of this system. Specifically,
the results of previous diagrammatic T-matrix approaches are extended into the
perturbatively inaccessible low energy regimes, and the long range (thermal)
transport behaviour of the system is discussed. It turns out that in the
extreme case of a half-filled tight binding band and infinitely strong
impurities (impurities at the unitary limit), the system is in a delocalized
phase.Comment: 14 pages, two figures include
Clinician vs Patient Reporting of Baseline and Postbaseline Symptoms for Adverse Event Assessment in Cancer Clinical Trials
Many patients enter cancer clinical trials with baseline symptoms. Notably, the current clinician reporting mechanism for symptomatic adverse events (AEs) via the Common Terminology Criteria for Adverse Events (CTCAE) does not formally distinguish between symptoms present at baseline vs those that develop during a trial. Therefore, AE estimation in clinical trials may include symptoms that predate trial entry. This raises concern that the cumulative incidence of patient-reported AEs may be high, particularly if preexisting symptoms related to other causes (eg, comorbidities, prior treatment) are attributed to study drugs
The Gribov-Zwanziger action in the presence of the gauge invariant, nonlocal mass operator in the Landau gauge
We prove that the nonlocal gauge invariant mass dimension two operator
can be consistently added to the
Gribov-Zwanziger action, which implements the restriction of the path
integral's domain of integration to the first Gribov region when the Landau
gauge is considered. We identify a local polynomial action and prove the
renormalizability to all orders of perturbation theory by employing the
algebraic renormalization formalism. Furthermore, we also pay attention to the
breaking of the BRST invariance, and to the consequences that this has for the
Slavnov-Taylor identity.Comment: 30 page
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