Chiral lariat ethers as membrane carriers for chiral amino acids and their sodium and potassium salts

Four chiral lariat ethers 8–11 containing a (p-methoxyphenoxy) methyl side arm were used for chiral discrimination of amino acids in their zwitterionic form or as potassium and sodium salts in transport across a bulk chloroform membrane with satisfactory selectivity. The carriers that were employed exhibited different transport selectivity relative to the amino acids and their salts under study. The d/l selectivity strongly depends on the amino acids or their salts, and in some cases reverse selectivity has been obtained. The best selectivity was obtained in the case of tyrosine and its potassium salts for all carriers. The transport rates of amino acids and their salts were found to be controlled by factors such as the structure of the carriers and amino acids or their salts. Among these factors, it was also found that the side arm of the lariat ethers plays an important role in the transport process. As a consequence, the main goal of our investigation was to separate the chiral amino acids through liquid membranes.     

On Tauberian theorems for (<Emphasis Type="Italic">A,k</Emphasis>) summability method

Let (u _n ) be a sequence of real numbers. In this paper we introduce some Tauberian conditions in terms of regularly generated sequences for (A, k) summability method.     

Seasonal Changes in Copper and Cobalt Concentrations of Pinus nigra L.,Cedrus libani and Cupressus arizonica Leaves to Monitor the Effects of Pollution in Elazig(Turkey)

The aim of this study is to examine seasonal changes in Cu and Co concentrations of three plant species for monitoring the effects of pollution in Elazig,Turkey.For this purpose,the leaves of the Pinus nigra L.,Cedrus libani and Cupressus arizonica together with soil samples were collected from different points depending on traffic intensity,nearness the city center and cement factory as well as control location during different months of the year.Flame atomic absorption spectrophotometer(FAAS) was used for measurement of the metals in clear digests after the dry ashing method.Copper and Co concentrations were in the ranges from 1.3to 2.6mg.kg-1 and相似文献   

Weight reduction for mod ? Bianchi modular forms

Let K be an imaginary quadratic field with class number one and ? be a rational prime that splits in K. We prove that mod ?, a system of Hecke eigenvalues occurring in the first cohomology group of some congruence subgroup Γ of SL₂(OK) can be realized, up to twist, in the first cohomology with trivial coefficients after increasing the level of Γ by (?).     

A note on efficient signaling of bargaining power

Strategic delay and restricted offers are two modes of signaling bargaining power in alternating offers bargaining games. This paper shows that when both modes are available, the best signaling strategy of the “strong” type of the informed player consists of a pure strategic delay followed by an offer on the whole pie. There is no signaling motivation for issue-by-issue bargaining when the issues are perfectly substitutable. Received: July 1996/Final version: August 1999     

Contribution of nitrification and denitrification to nitrous oxide emissions from soils after application of biogas waste and other fertilizers

The attribution of nitrous oxide (N₂O) emission to organic and inorganic N fertilizers requires understanding of how these inputs affect the two biological processes, i.e. denitrification and nitrification. Contradictory findings have been reported when the effects of organic and inorganic fertilizers on nitrous oxide emission were compared. Here we aimed to contribute to the understanding of such variation using ¹⁵N‐labelling techniques. We determined the processes producing N₂O, and tested the effects of soil moisture, N rates, and the availability of organic matter. In a pot experiment, we compared soil treated with biogas waste (BGW) and mineral ammonium sulphate (Min‐N) applied at four rates under two soil moisture regimes. We also tested biogas waste, conventional cattle slurry and mineral N fertilizer in a grassland field experiment. During the first 37 days after application we observed N₂O emissions of 5.6 kg N₂O‐N ha^?1 from soils supplied with biogas waste at a rate of 360 kg N ha^?1. Fluxes were ca. 5‐fold higher at 85% than at 65% water holding capacity (WHC). The effects of fertilizer types and N rates on N₂O emission were significant only when the soil moisture was high. Organic fertilizer treated soils showed much higher N₂O emissions than those receiving mineral fertilizer in both, pot and field experiment. Over all the treatments the percentage of the applied N emitted as N₂O was 2.56% in BGW but only 0.68% in Min‐N. In the pot experiment isotope labelling indicated that 65–95% of the N₂O was derived from denitrification for all fertilizer types. However, the ratio of denitrification/nitrification derived N₂O was lower at 65% than at 85% WHC. We speculate that the application of organic matter in conjunction with ammonium nitrogen first leads to a decrease in denitrification‐derived N₂O emission compared with soil receiving mineral fertilizer. However, at later stages when denitrification becomes C‐limited, higher N₂O emissions are induced when the soil moisture is high. Copyright © 2009 John Wiley & Sons, Ltd.     

Efficient synthesis of some oxalacetic acid and pyruvic acid derivatives from the reactions of 2,3-furandiones with 2-phenylindole

Oxalacetic acid and pyruvic acid derivatives have been synthesized efficiently in high yields by the treatment of 4-ethoxycarbonyl-5-phenyl-2,3-furandione and 4-benzoyl-5-phenyl-2,3-furandione with 2-phenylindole at room temperature and converted to simple derivatives such as an ester or a hydrazone.     

Supplier diversification under binomial yield

We consider supplier diversification in an EOQ type inventory setting with multiple suppliers and binomial yields. We characterize the optimal policy for the model and show that, in this case, it does not pay to diversify, in contrast to previous results in the random yield literature.