After some general remarks, a few observed time-scale in stars discussed in this colloquium are presented. Characteristic times in stellar models for the internal structure and the outerlayers are
reviewed. Examples of mode Identification are discussed. In the low frequency domain, the situation is quite simple. But the high frequency region is more difficult to decipher as many phenomena occupy the same domain: orbital motion, rotation of a non-uniform body, spheroidal g modes and Rossby waves. The linear framework is not always relevant and the nonlinear dynamic is more difficult to characterise. In general timescales alone cannot permit a mode idenfitication. Additional informations on energy content, amplitudes, coherence, multiplicity, stationarity are necessary to discriminate among the different possibilities.
In this paper we are concerned with a class of time-varying discounted Markov decision models Mn with unbounded costs cn and state-action dependent discount factors. Specifically we study controlled systems whose state process evolves according to the equation xn+1=Gn(xn,an,ξn),n=0,1,…, with state-action dependent discount factors of the form αn(xn,an), where an and ξn are the control and the random disturbance at time n, respectively. Assuming that the sequences of functions {αn},{cn} and {Gn} converge, in certain sense, to α∞, c∞ and G∞, our objective is to introduce a suitable control model for this class of systems and then, to show the existence of optimal policies for the limit system M∞ corresponding to α∞, c∞ and G∞. Finally, we illustrate our results and their applicability in a class of semi-Markov control models.
Potential involvement of circadian clock genes in so far unknown mechanism of photoperiodic time measurement is an important question of insect life-cycle regulation science. Here we report about the cloning of full-length cDNA of the structural homologue of the Drosophila's timeless gene in Chymomyza costata. Its expression was compared in two strains: a wild-type strain, responding to short days by entering larval diapause and a npd-mutant strain, showing no photoperiodic response. The timeless mRNA transcripts were not detectable by Northern blot analysis in the fly heads of npd-mutants, while they were detectable and showed typical daily oscillations in the wild-type strain. After disrupting the normal process of timeless transcription in the wild-type strain by injection of timeless double-strandRNA into early embryos of wild-type (RNAi method: Kennerdell & Carthew 1998, 2000), a certain proportion of the individuals adopted a npd-mutant phenotype, showing no-diapause in response to short-daylength. Cloning of genomic DNA fragments revealed that npd-mutants carry a different allele, timelessnpd, with a 13-bp insertion in an intron positioned within the 5'-leader sequence. Genetic linkage analysis showed that the 13-bp insertion (a marker for timelessnpd) and the absence of response to short days (a marker for npd-phenotype) are strictly co-inherited in the F2 progeny of the reciprocal crosses between wild-type and npd-mutant flies. Such results indicated that the locus npd could code for the timeless gene in C. costata and its product might thus represent a molecular link between circadian and photoperiodic clock systems in this fly.
(Statement of Responsibility) von Dobelhof - Dier, partitura tisk, party opis, (Ownership) Biskupský seminář České Budějovice, opsal Schönbek theolog. ann. II, 1883 CZ-CbJVK, and (Version Identification) Mh 14 CZ-CbJVK