3,046 research outputs found
Dr. Awkward and Olson in Oslo
The long voyage between my first tentative effort at constructing a short palindrome of some forty letters, and the eventual completion of a palindromic novel numbering 31,594 words (or approximately 104,000 letters) some twenty years later, was an unrelenting lesson in many disciplines. There were lessons in trial and error, in logic, in vocabulary, in syntactics, and a wide-ranging lexical development that I never thought possible. Although I had always considered myself a more than ordinary lover of my native language, I had never before realized how metamorphic and submissive was this extraordinary English tongue, until the day I began manipulating its words, letter by letter, for palindromic composition
Proteasome inhibitors: Their effects on arachidonic acid release from cells in culture and arachidonic acid metabolism in rat liver cells
BACKGROUND: I have postulated that arachidonic acid release from rat liver cells is associated with cancer chemoprevention. Since it has been reported that inhibition of proteasome activities may prevent cancer, the effects of proteasome inhibitors on arachidonic acid release from cells and on prostaglandin I(2 )production in rat liver cells were studied. RESULTS: The proteasome inhibitors, epoxomicin, lactacystin and carbobenzoxy-leucyl-leucyl-leucinal, stimulate the release of arachidonic acid from rat glial, human colon carcinoma, human breast carcinoma and the rat liver cells. They also stimulate basal and induced prostacycin production in the rat liver cells. The stimulated arachidonic acid release and basal prostaglandin I(2 )production in rat liver cells is inhibited by actinomycin D. CONCLUSIONS: Stimulation of arachidonic acid release and arachidonic acid metabolism may be associated with some of the biologic effects observed after proteasome inhibition, e.g. prevention of tumor growth, induction of apoptosis, stimulation of bone formation
Effect of mean on variance function estimation in nonparametric regression
Variance function estimation in nonparametric regression is considered and
the minimax rate of convergence is derived. We are particularly interested in
the effect of the unknown mean on the estimation of the variance function. Our
results indicate that, contrary to the common practice, it is not desirable to
base the estimator of the variance function on the residuals from an optimal
estimator of the mean when the mean function is not smooth. Instead it is more
desirable to use estimators of the mean with minimal bias. On the other hand,
when the mean function is very smooth, our numerical results show that the
residual-based method performs better, but not substantial better than the
first-order-difference-based estimator. In addition our asymptotic results also
correct the optimal rate claimed in Hall and Carroll [J. Roy. Statist. Soc.
Ser. B 51 (1989) 3--14].Comment: Published in at http://dx.doi.org/10.1214/009053607000000901 the
Annals of Statistics (http://www.imstat.org/aos/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Variance estimation in nonparametric regression via the difference sequence method
Consider a Gaussian nonparametric regression problem having both an unknown
mean function and unknown variance function. This article presents a class of
difference-based kernel estimators for the variance function. Optimal
convergence rates that are uniform over broad functional classes and bandwidths
are fully characterized, and asymptotic normality is also established. We also
show that for suitable asymptotic formulations our estimators achieve the
minimax rate.Comment: Published in at http://dx.doi.org/10.1214/009053607000000145 the
Annals of Statistics (http://www.imstat.org/aos/) by the Institute of
Mathematical Statistics (http://www.imstat.org
A Semiparametric Multivariate Partially Linear Model: A Difference Approach
A multivariate semiparametric partial linear model for both fixed and random design cases is considered. In either case, the model is analyzed using a difference sequence approach. The linear component is estimated based on the differences of observations and the functional component is estimated using a multivariate Nadaraya–Watson kernel smoother of the residuals of the linear fit. We show that both components can be asymptotically estimated as well as if the other component were known. The estimator of the linear component is shown to be asymptotically normal and efficient in the fixed design case if the length of the difference sequence used goes to infinity at a certain rate. The functional component estimator is shown to be rate optimal if the Lipschitz smoothness index exceeds half the dimensionality of the functional component argument. We also develop a test for linear combinations of regression coefficients whose asymptotic power does not depend on the functional component. All of the proposed procedures are easy to implement. Finally, numerical performance of all the procedures is studied using simulated data
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