5,423 research outputs found
A Threshold Model of Real US GDP and the Problem of Constructing Confidence Intervals in TAR Models
We estimate real U.S. GDP growth as a threshold autoregressive process, and construct confidence intervals for the parameter estimates. However, there are various approaches that can be used in constructing the confidence intervals. Specifically, standard- t , bootstrap- t , and bootstrap-percentile confidence intervals are simulated for the slope coefficients and the estimated threshold. However, the results for the different methods have very different economic implications. We perform a Monte Carlo experiment to evaluate the various methods.Bootstrap GDP; Threshold Autoregression; Bootstrap Confidence Intervals
Induction of IL 2 receptor expression and cytotoxicity of thymocytes by stimulation with TCF1
We investigated the role of T cell cytotoxicity inducing factor 1 (TCF1) in the induction of a cytotoxic T cell response. We found that help-deficient thymocyte cultures supplied with saturating amounts of purified IL 2 did not develop CTL in a 5-day culture. The expression of cytotoxicity was dependent on the addition of TCF1 derived from the T cell hybridoma K15. TCF1 also induced proliferation of thymocytes in the presence of IL 2. Only the PNA- thymocyte subpopulation responded to TCF1 with proliferation and cytotoxicity in the presence of IL 2. The monokine IL 1 also induced proliferation in this subpopulation but failed to induce cytotoxicity. IL 1 was further distinguished from TCF1 by inhibition of IL 1-induced but not TCF1-induced proliferation by anti-IL 1 antibodies. In addition, using anti-IL 2 receptor antibodies (AMT 13), we showed that TCF1 in the presence of IL 2 substantially increased IL 2 receptor expression in thymocytes. IL 1 had the same effect on induction of IL 2 receptor expression as TCF1. Because some effects of IL 1 and TCF1 are distinct and some overlap, we discuss whether IL 1 and TCF1 induce different subsets of PNA- thymocytes
Prescription opioid use and risk for major depressive disorder:a multivariable Mendelian randomization analysis
Elastic effects on relaxation volume tensor calculations
Relaxation volume tensors quantify the effect of stress on diffusion of
crystal defects. Continuum linear elasticity predicts that calculations of
these parameters using periodic boundary conditions do not suffer from
systematic deviations due to elastic image effects and should be independent of
supercell size or symmetry. In practice, however, calculations of formation
volume tensors of the interstitial in Stillinger-Weber silicon
demonstrate that changes in bonding at the defect affect the elastic moduli and
result in system-size dependent relaxation volumes. These vary with the inverse
of the system size. Knowing the rate of convergence permits accurate estimates
of these quantities from modestly sized calculations. Furthermore, within the
continuum linear elasticity assumptions the average stress can be used to
estimate the relaxation volume tensor from constant volume calculations.Comment: 31 pages, 6 figures, submitted to Phys. Rev.
Phenomenological Study of Strong Decays of Heavy Hadrons in Heavy Quark Effective Theory
The application of the tensor formalism of the heavy quark effective theory
(HQET) at leading order to strong decays of heavy hadrons is presented.
Comparisons between experimental and theoretical predictions of ratios of decay
rates for B mesons, D mesons and kaons are given. The application of HQET to
strange mesons presents some encouraging results. The spin-flavor symmetry is
used to predict some decay rates that have not yet been measured.Comment: 10 page
MESA and NuGrid simulations of classical novae: CO and ONe nova nucleosynthesis
Classical novae are the result of thermonuclear flashes of hydrogen accreted
by CO or ONe white dwarfs, leading eventually to the dynamic ejection of the
surface layers. These are observationally known to be enriched in heavy
elements, such as C, O and Ne that must originate in layers below the H-flash
convection zone. Building on our previous work, we now present stellar
evolution simulations of ONe novae and provide a comprehensive comparison of
our models with published ones. Some of our models include exponential
convective boundary mixing to account for the observed enrichment of the nova
ejecta even when accreted material has a solar abundance distribution. Our
models produce maximum temperature evolution profiles and nucleosynthesis
yields in good agreement with models that generate enriched ejecta by assuming
that the accreted material was pre-mixed. We confirm for ONe novae the result
we reported previously, i.e.\ we found that He could be produced {\it in
situ} in solar-composition envelopes accreted with slow rates (\dot{M} <
10^{-10}\,M_\odot/\mbox{yr}) by cold ( K) CO WDs, and that
convection was triggered by He burning before the nova outburst in that
case. In addition, we now find that the interplay between the He production
and destruction in the solar-composition envelope accreted with an intermediate
rate, e.g.\ \dot{M} = 10^{-10}\,M_\odot/\mbox{yr}, by the ONe
WD with a relatively high initial central temperature, e.g.\ K, leads to the formation of a thick radiative buffer zone that
separates the bottom of the convective envelope from the WD surface. (Abridged)Comment: 19 pages, 23 figures, 2 tables, accepted to publication by MNRA
Weak dipole moment of in collisions with longitudinally polarized electrons
It is pointed out that certain CP-odd momentum correlations in the production
and subsequent decay of tau pairs in collisions get enhanced when the
is longitudinally polarized. Analytic expressions for these correlations
are obtained for the single-pion decay mode of when have
a ``weak" dipole form factor (WDFF) coupling to . For collisions
at the peak, a sensitivity of about 1-5\mbox{ cm} for
the WDFF can be reached using a {\em single} decay
channel, with 's likely to be available at the SLC at Stanford with
polarization of 62\%-75\%.Comment: 9 pages, Latex, PRL-TH-93/17 (Revised
Radiative Leptonic Decays of Heavy Mesons
We compute the photon spectrum and the rate for the decays These photonic modes constitute a potentially large background
for the purely leptonic decays which are used to extract the heavy meson decay
constants. While the rate for D\to l\n\g is small, the radiative decay in the
meson case could be of comparable magnitude or even larger than B\to\m\n.
This would affect the determination of if the channel cannot be
identified. We obtain theoretical estimates for the photonic rates and disscuss
their possible experimental implications.Comment: 12 pages, RevTex, 3 uuencoded figures include
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