Evaluation of the use of Sr2+ in alginate immobilization of cells

In recent years the method of immobilization of living cells in Ca-alginate beads has gained a wide range of applications. In all cases high chemical stability of the immobilization material and mild conditions for the cells are prerequisites. However, in long-term experiments that may last for several days Ca-alginate may dissolve due to an exchange of Ca²⁺ with Na⁺, forming fluid Na-alginate. As well as Ca-alginate, the more chemically stable Sr-alginate and Ba-alginate are materials that have been used for the immobilization of living cells. In this study, the effects of Ca²⁺, Sr²⁺ and Ba²⁺ on growth, viability and intracellular free calcium concentration in a human leukemic T cell line (Jurkat) were investigated. The findings in this study, and the fact that Sr-alginate has a considerably higher chemical stability than Ca-alginate, led to the conclusion that Sr-alginate is a more suitable material for use in the entrapment of living cells in long-term studies.     

The effect of other orientation on self–supervisor rating agreement

Employees generally rate their performance more favorably than do their supervisors, which can lead to conflict and poor job performance. However, comparative international research indicates that persons from other‐oriented collectivist cultures are less self‐enhancing, suggesting that other‐oriented employees will exhibit greater agreement with ratings provided by their supervisors. We examined the effect of subordinates' other orientation on self‐supervisor performance rating agreement. Consistent with cultural expectations, self‐ratings of other‐oriented subordinates showed greater agreement with ratings provided by their supervisors and less leniency relative to their supervisors' evaluations. These findings have implications for understanding how employees in different professions, organizations, and cultures utilize feedback from their supervisors. Copyright © 2004 John Wiley & Sons, Ltd.     

CONFIDENCE INTERVALS FOR FLOOD EVENTS UNDER A PEARSON 3 OR LOG PEARSON 3 DISTRIBUTION1

ABSTRACT: The Pearson type 3 (P3) and log Pearson type 3 (LP3) distributions are very frequently used in flood frequency analysis. Existing methods for constructing confidence intervals for quantiles (X_p) of these two distributions are very crude. Most of these methods are based on the idea of adjusting confidence intervals for quantiles Y_p of the normal distribution to obtain approximate confidence inervals for quantiles X_p of the P3/LP3 distribution. Since there is no theoretical reason why this “base” distribution, Y, should be taken to be normal, we search in the present study for the best possible base distribution for producing confidence intervals for P3/LP3 quantiles. We consider a group of base distributions such as the normal, log normal, Weibull, Gumbel, and exponential. We first assume that the skew coefficient, γ of X, to be known, and develop a method for adjusting confidence intervals for Y_p to produce approximate confidence intervals for X_p. We then compare this method (Method A) with another method (Method B) introduced by Stedinger. Simulation shows that the performance of each of these two methods depends on the base distribution Y that is being used, but as a whole, the normal distribution appears to be the best-fit distribution for producing confidence intervals for P3/LP3 quantiles when γ is assumed to be known. We then extend our method (Method A) to the more important case of unknown coefficient of skewness. It is shown that by taking Y to be Weibull, fairly accurate confidence intervals for P3/LP3 quantiles can be obtained for quite a wide range of sample sizes and coefficients of skewness commonly found in hydrology. The case of the P3 distribution with negative skewness needs further research.     

Estimating the Relative Efficiency of Brazilian Publicly and Privately Owned Water Utilities: A Stochastic Cost Frontier Approach1

Abstract: This paper assesses cost efficiencies of Brazilian public and private companies of water supply. To measure the efficiency, we used a stochastic frontier model derived from the translog family – a specification similar to a Cobb‐Douglas including a quadratic term in log output. The model parameters are estimated by maximum likelihood using Brazilian data for the year 2002. Statistical inference leads to the conclusion that there is no evidence that private firms and public firms are significantly different in terms of efficiency measurements.     

Taking Ethics into Account in Farm Animal Breeding: What can the Breeding Companies Achieve?

Animal welfare and the ethical issues it raises have been discussed intensively for a couple of decades. The emphasis has been on the direct effects of housing and husbandry, but more attention is now being given to problems originating in selective breeding. European attempts to adjust animal welfare legislation to deal with these problems have been largely unsuccessful, but the fact that selective breeding can introduce welfare problems continues to place an ethical responsibility on the animal breeding industry. Since breeding decisions are made centrally and, increasingly, internationally, strategic change is only likely to occur if it is embedded in an international agreement of some kind. The aim of this paper is to describe the key ethical issues facing animal breeding and assess the suggestion that the breeding industry itself can deal with ethical issues by means of an ethical code. Results from recent projects involving commercial breeding enterprises are presented.     

Ammonia stomatal compensation point of young oilseed rape leaves during dark/light cycles under various nitrogen nutritions

The plant can be a source or a sink of ammonia (NH₃) depending on its nitrogen (N) supply, metabolism and on the background atmospheric concentrations. Thus plants play a major role in regulating atmospheric NH₃ concentrations. For a better understanding of the factors influencing the NH₃ stomatal compensation point, it is important to analyse the dynamics of leaf NH₃ fluxes. The relationship between the leaf NH₃ fluxes and the leaf apoplast ammonium and nitrate concentrations, N nutrition and the light and dark periods was studied here.We designed an experiment to quantitatively assess leaf-atmosphere NH₃ exchange and the stomatal compensation point and to identify the main factors affecting the variation of NH₃ fluxes in oilseed rape. We tested day and night dynamics as well as the effect of five different N treatments. Two experimental methods were used: a dynamic open flux chamber and extraction of the apoplastic solution.Chamber measurements showed that there was a good correlation between plant NH₃ fluxes and water fluxes. Compensation points were calculated by two different methods and ranged between 0.8 and 12.2 μg m⁻³ NH₃ (at 20 °C) for the different N treatments. Apoplastic solution measurements showed that there was no significant differences in the apoplastic NH₄⁺ concentrations ([NH₄⁺]_apo) extracted in dark and light periods for the same N treatment. Statistical analysis also showed that [NH₄⁺]_apo was correlated with [NH₄⁺] in the nutrient solution and weakly correlated with [NO₃⁻]. Apoplast NH₄⁺ concentrations ranged between 0.1 and 2.1 mM, bulk tissue NH₄⁺ concentrations between 3.9 and 6.6 mM and xylem concentrations between 2.4 and 6.1 mM depending on the N supply.Calculated NH₃ emission potential from the extraction measurements were over-estimated when compared with the value calculated from chamber measurements. Errors related to chamber measurements included separation of the cuticular and stomatal fluxes and the calculation of total resistance to NH₃ exchange. Errors related to the extraction measurements included assessing the amount of cytoplasmic contamination. We do not have another method to assess the NH₃ stomatal compensation point and the choice between these two measurement techniques should depend on the scales to which the measurements apply and the processes to be studied.     

Citation marketing and networking

This is a comment on Thatje (Naturwissenschaften 97:237–239, 2010) The multiple faces of journal peer review, Naturwissenschaften, 97:237–239.     

The ornament�Ccondition relationship varies with parasite abundance at population level in a female bird

Environmental heterogeneity is expected to create variation in the ornament-condition relationship. This topic has been studied in males with less attention being given to females. Here, we explore inter-population variation in the relationship between the size of a male-like trait, supra-orbital combs, and body mass in female red grouse Lagopus lagopus scoticus. We used the abundance of the nematode Trichostrongylus tenuis, a parasite with strong negative effects on this species, as a proxy of environmental conditions. We studied six populations over 5?years and showed that the comb size-body mass relationship varied with mean parasite abundance, with stronger ornament-condition relationships in populations with higher parasite infection levels. Our study supports the idea that environmental conditions, and in particular parasite infection levels, may affect the reliability of female ornaments as condition indicators.