The nonemptiness of thef-core of a game without side payments

We prove the nonemptiness of the core of a continuum game without side payments where only small coalitions — ones bounded in absolute size of finite cardinality — are permitted. This result covers assignment games with a continuum of players and includes combinations of several assignment games, such as housing and automobile markets.The authors thank two anonymous referees for many helpful comments. The second author is indebted primarily to the Natural Sciences and Engineering Research Council of Canada for financial support and also the Social Sciences and Humanities Research Council of Canada.     

Quantitative Bestimmung des Fluors, Chlors und Broms in biologischem Material

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Enhancement of the photoluminescence intensity of a single InAs/GaAs quantum dot by separate generation of electrons and holes

It is demonstrated that the microphotoluminescence (μPL) spectrum of a single InAs/GaAs self-assembled quantum dot (QD) undergoes considerable changes when the primary laser excitation is complemented with an additional infrared laser. The primary laser, tuned slightly below the GaAs band gap, provides electron-hole pairs in the wetting layer (WL), as well as excess free electrons from ionized shallow acceptors in the GaAs barriers. An additional IR laser with a fixed energy well below the QD ground state transition generates excess free holes from deep levels in GaAs. The excess electron and hole will experience diffusion separately, due to the time separation between the two events of their generation, to eventually become captured into the QD. Although the generation rates of excess carries are much lower than that of the electron-hole pair generation in the WL, they considerably influence the QD emission at low temperatures. The integrated PL intensity increases by several times as compared to single-laser excitation, and the QD exciton spectrum is redistributed in favor of a more neutral charge configuration. The dependence of the observed phenomenon on the powers of the two lasers and the temperature has been studied and is consistent with the model proposed. The concept of dual excitation could be successfully applied to different low-dimensional semiconductor structures in order to manipulate their charge state and emission intensity. The text was submitted by the authors in English.     

In vitro and in vivo survival of mouse blastocysts after repeated vitrification with the open pulled straw (OPS) method

This study addresses the in vitro and in vivo survival of mouse embryos repeatedly vitrified by the OPS-technique of Vajta et al. (24). Of 225 vitrified blastocysts, after warming one third was cultured in vitro, the other two-thirds were re-vitrified. After these were warmed, the second third was put to culture. With the remaining third the procedure was repeated. Of embryos vitrified once, 97% developed to expanded blastocysts and 81% proceeded to hatching. Corresponding values for embryos re-vitrified once were 93% and 72%, respectively (P > 0.05). After another re-vitrification, expansion and hatching rates were reduced to 76% and 35%, respectively (P < 0.01). Of 10 recipients provided with 10 embryos each that had been vitrified once, 80% remained pregnant with 5.5 +/- 0.3 fetuses. Corresponding values for re-vitrified embryos were 80% and 5.0 +/- 0.3. Of all embryos transferred, 44% became vital fetuses after a single vitrification, compared to 40% after revitrification.     

Evaluation of optical quality and properties of Ga0.64In0.36N0.006As0.994 lattice matched to GaAs by using photoluminescence spectroscopy

We have investigated optical properties of Ga_0.64In_0.36N_0.006As_0.994/GaAs single quantum-well structures using photoluminescence technique. We have found that nitrogen creates potential fluctuations in the InGaNAs structures, so it is the cause of trap centres in these structures and leads to localized excitons recombination dynamics. The near-band edge PL at 2 K exhibited a blueshift with an increase in excitation intensity of a sample but there is not such a shift in the PL peak position energy of same sample at 150 K. It has been found that PL spectra have a large full width at half maximum (FWHM) value at 2 K. These results are discussed in terms of carrier localization. Additionally, our results suggest decreasing PL integrated intensity in this structure, possibly due to non-radiative recombination. It has been shown that thermal annealing reduces the local strain created by nitrogen. By annealing process, a blue shifted emission can be observed.     

Macrocyclic Olefin Metathesis at High Concentrations by Using a Phase‐Separation Strategy

Macrocyclic olefin metathesis has seen advances in the areas of stereochemistry, chemoselectivity, and catalyst stability, but strategies aimed at controlling dilution effects in macrocyclizations are rare. Herein, a protocol to promote macrocyclic olefin metathesis, one of the most common synthetic tools used to prepare macrocycles, at relatively high concentrations (up to 60 mM ) is described by exploitation of a phase‐separation strategy. A variety of macrocyclic skeletons could be prepared having either different alkyl, aryl, or amino acids spacers.     

One-pot reactions of 2,4-(dioxobutylidene)phosphoranes. Efficient synthesis of 4-(2-hydroxybenzoyl)salicylic acid derivatives and buta-1,3-diene-1,4-dicarboxylates

4-(2-Hydroxybenzoyl)salicylic esters and amides were prepared by domino ‘Michael-Retro-Michael-Wittig’ reactions of (2,4-dioxobutylidene)triphenylphosphoranes with 3-formylchromones.     

Mikrochemie

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