Tento článek se pokouší vysvětlit schema ve tvaru U v míře návratu migrantů ve vztahu k dosaženému vzdělání. Vytváříme OLG model na dvě období, kde jsou rozhodnutí emigrovat a navrátit se udělána činiteli, kteří jsou heterogenní z pohledu dosaženého vzdělání. Imigrační politika je brána v potaz jako další determinanta migračního rozhodnutí. Model předpovídá, že kombinace dvou sil - relativní návratnost vzdělávání a nejisté příležitosti pro přizpůsobení statusu - vede ke kladným podmínkám k tomu, aby migranti se středoškolským vzděláním zůstali v zahraničí natrvalo., Renata Ivanova, Byeongju Jeong ; editor: Michal Kejak., and born digital
In this paper we present the first insight about the impact of the COVID epidemic on the pri-mary housing market in Poland, with a focus on Warsaw which is the largest market. We ex-plain the structural features that allowed the market to return to pre-shock levels after the pandemic shock. Contrary, after the 2007-2008 global financial crisis the negative consequences lasted for several years. This time a sharp monetary policy and fiscal intervention was carried out. Moreover, the developer sector is much more mature, has expanded its production capaci-ties. We show empirically that the monopolistic competition of developers allowed them to restrict excessive demand that was observed before the COVID broke out. In this way they were able to increase prices despite the economic problems. Another important structural change was the increased housing demand, mainly for investment housing, which was fi-nanced predominantly with cash and contributed to the development of the rental market. We approximate the investment demand, which was generated by private households that pur-chased flats for rental, with the help of a simple demand and supply model.
Factors were examined that could be responsible for the predominance of Coccinella septempunctata (C7) in most habitats of the Palaearctic and for its successful invasion of the Nearctic Region. C7 is euryphagous, but less polyphagous than Harmonia axyridis or Coleomegilla maculata in that it cannot develop or reproduce on non-aphid food. The intraguild status of C7 is intermediate. Although adult size is large, preimaginal stages are palatable to those of H. axyridis and Adalia bipunctata, whereas it is not an intraguild predator of these species. Although these traits appear to be neutral or negative, many aspects of population plasticity are advantageous for C7, often acting in concert with a bet-hedging strategy. Given its high mobility and eurytopy, the inhibition of oviposition in the presence of conspecific larval trails represents an adaptive advantage that favors increased egg dispersal and lowers the risk of offspring mortality due to cannibalism. The ability to temporarily suspend oviposition, combined with heterogenous voltinism and diapause tendencies, enable a portion of C7 populations to feed and reproduce on unpredictably occurring aphid populations. An absence of reproductive diapause in males and pre-hibernation mating are other significant adaptations, along with the tendency to produce offspring in excess of the carrying capacity of local food resources. We suggest that one explanation for the broad geographic success of C7 resides in an ecological plasticity that is based on both genetic and phenotypic polymorphisms.
In this article we will describe a surprising observation that occurred in the construction of quadratic unramified extensions of a family of pure cubic number fields. Attempting to find an explanation will lead us on a magical mystery tour through the land of pure cubic number fields, Hilbert class fields, and elliptic curves.
N. N. Cencov wrote a commentary chapter included in the Appendix of the Russian translation of the Devroye and Györfi book [15] collecting some arguments supporting the <span class="tex">L<sub>1</sub></span> view of density estimation. The Cencov's work is available in Russian only and it hasn't been translated, so late Igor Vajda decided to translate the Cencov's paper and to add some remarks on the occasion of organizing the session "25 Years of the <span class="tex">L<sub>1</sub></span> Density Estimation" at the Prague Stochastics 2010 Symposium. In this paper we complete his task, i.e., we translate the Cencov's chapter and insert some remarks on the related literature focusing primarily on Igor's results. We would also like to acknowledge the excellent work of Alexandre Tsybakov who translated the Devroye and Györfi book in Russian, annotated it with valuable comments and included some related references published in Russian only.
The paper is concerned with generalized (i. e. monotone and possibly non-additive) measures. A discussion concerning the classification of these measures, according to the type and amount of non-additivity, is done. It is proved that λ-additive measures appear naturally as solutions of functional equations generated by the idea of (possible) non additivity.