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Selected AbstractsThe effects of dispersal and recruitment limitation on community structure of odonates in artificial pondsECOGRAPHY, Issue 4 2006Shannon J. McCauley I examined the effects of isolation on the structure of both adult and larval dragonfly (Odonata: Anisoptera) communities forming at physically identical artificial ponds over two years. Isolation, whether measured by distance to the nearest source habitat or by connectivity to multiple sources, was significantly negatively related to the species richness of dragonflies observed at and collected in these ponds. These results indicate that dispersal and recruitment limitation acted as filters on the richness of communities at these artificial ponds. The richness of larval recruits in artificial ponds was lower than the richness of adult dispersers observed at ponds, and distance from a source habitat explained a greater fraction of the variation in larval than adult richness (83 and 50%, respectively). These results and a male biased sex-ratio in adults observed at artificial ponds suggest that isolated habitats may be more recruitment limited than observations of dispersers would suggest. A Mantel test indicated there was a spatial component to the composition of communities forming in tanks, and that distance between tanks and community dissimilarity (1-Jaccard's) were significantly positively related (r=0.52). This pattern suggests that their position with respect to alternative source environments influenced the composition of the communities that recruited into these ponds. These results provide further evidence of recruitment limitation in this system. Results from this study highlight the importance behaviorally limited dispersal may have in taxa morphologically capable of broad dispersal and suggest that the role of dispersal and recruitment limitation may be critical in shaping community structure across habitat gradients that include variation in habitat duration. [source] Valuing executive stock options: performance hurdles, early exercise and stochastic volatilityACCOUNTING & FINANCE, Issue 3 2008Philip Brown G13 Abstract Accounting standards require companies to assess the fair value of any stock options granted to executives and employees. We develop a model for accurately valuing executive and employee stock options, focusing on performance hurdles, early exercise and uncertain volatility. We apply the model in two case studies and show that properly computed fair values can be significantly lower than traditional Black,Scholes values. We then explore the implications for pay-for-performance sensitivity and the design of effective share-based incentive schemes. We find that performance hurdles can require a much greater fraction of total compensation to be a fixed salary, if pre-existing incentive levels are to be maintained. [source] Synthesis and characterization of polyaniline doped with organic acidsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2004Milind V. Kulkarni Abstract Spectroscopic [UV,visible and Fourier transform IR (FTIR)] and thermal properties of chemically synthesized polyanilines are found to be affected by varying the protonation media (acetic, citric, oxalic, and tartaric acid). The optical spectra show the presence of a greater fraction of fully oxidized insulating pernigraniline phase in polyaniline doped with acetic acid. In contrast, the selectivity in the formation of the conducting phase is higher in oxalic acid as a protonic acid media. The FTIR spectra of these polymers reveal a higher ratio of the relative intensities of the quinoid to benzenoid ring modes in acetic acid doped polyaniline. Scanning electron micrographs revealed a sponge-like structure derived from the aggregation of the small granules in acetic acid and oxalic acid doped polyaniline. A three-step decomposition pattern is observed in all the polymers, regardless of the protonic acid used for the doping. The second step loss related to the loss of dopant is found to be higher in the oxalic acid doped polymer. In accordance with these results the conductivity is also found to be higher in oxalic acid doped material. The temperature dependent conductivity measurements show the thermal activated behavior in all the polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2043,2049, 2004 [source] Herbivory and Abiotic Factors Affect Population Dynamics of Arabidopsis thaliana in a Sand Dune AreaPLANT BIOLOGY, Issue 5 2005A. Mosleh Arany Abstract: Population dynamics of the annual plant Arabidopsis thaliana (L.) Heynh. were studied in a natural habitat of this species on the coastal dunes of the Netherlands. The main objective was to elucidate factors controlling population dynamics and the relative importance of factors affecting final population density. Permanent plots were established and plants were mapped to obtain data on survival and reproductive performance of each individual, with special attention to herbivore damage. In experimental plots we studied how watering, addition of nutrients, artificial disturbance, and natural herbivores affected survival and growth. Mortality was low during autumn and early winter and high at the time of stem elongation, between February and April. A key factor analysis showed a high correlation between mortality from February to April and total mortality. The specialist weevils Ceutorhyncus atomus and C. contractus (Curculionidae) were identified as the major insect herbivores on A. thaliana, reducing seed production by more than 40 %. These herbivores acted in a plant size-dependent manner, attacking a greater fraction of the fruits on large plants. While mortality rates were not affected by density, fecundity decreased with density, although the effect was small. Adding water reduced mortality in rosette and flowering plant stages. Soil disturbance did not increase seed germination, but did have a significant positive effect on survival of rosette and flowering plants. Seed production of A. thaliana populations varied greatly between years, leading to population fluctuations, with a small role for density-dependent fecundity and plant size-dependent herbivory. [source] Phosphoproteome analysis of the human Chang liver cells using SCX and a complementary mass spectrometric strategyPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 10 2008Shaohui Sui Abstract The liver is the largest organ in the body, with many complex, essential functions, such as metabolism, deintoxication, and secretion, often regulated via post-translational modifications, especially phosphorylation. Thus, the detection of phosphoproteins and phosphorylation sites is important to comprehensively explore human liver biological function. The human Chang liver cell line is among the first derived from non-malignant tissue, and its phosphoproteome profile has never been globally analyzed. To develop the complete phosphoproteome and probe the roles of protein phosphorylation in normal human liver, we adopted a shotgun strategy based on strong cation exchange chromatograph, titanium dioxide and LC-MS/MS to isolate and identify phosphorylated proteins. Two types of MS approach, Q-TOF and IT, were used and compared to identify phosphosites from complex protein mixtures of these cells. A total of 1035 phosphorylation sites and 686 phosphorylated peptides were identified from 607 phosphoproteins. A search using the public database of PhosphoSite showed that approximately 344 phosphoproteins and 760 phosphorylation sites appeared to be novel. In addition, N-terminal phosphorylated peptides were a greater fraction of all identified phosphopeptides. With GOfact analysis, we found that most of the identified phosphoproteins are involved in regulating metabolism, consistent with the liver's role as a key metabolic organ. [source] Impaired enzyme-to-enzyme channelling between hexokinase isoenzyme(s) and phosphoglucoisomerase in rat pancreatic islets incubated at a low concentration of D -glucoseCELL BIOCHEMISTRY AND FUNCTION, Issue 1 2005Ying Zhang Abstract It was recently proposed that in rat pancreatic islets exposed to 8.3,mMD -glucose, ,- D -glucose-6-phosphate undergoes enzyme-to-enzyme channelling between hexokinase isoenzyme(s) and phosphoglucoisomerase. To explore the identity of the hexokinase isoenzyme(s) involved in such a tunnelling process, the generation of 3HOH from the ,- and ,-anomers of either D -[2- 3H]glucose or D -[5- 3H]glucose was now measured over 60,min incubation at 4°C in pancreatic islets exposed only to 2.8,mMD -glucose, in order to decrease the relative contribution of glucokinase to the phosphorylation of the hexose. Under these experimental conditions, the ratio for 3HOH production from D -[2- 3H]glucose/D -[5- 3H]glucose at anomeric equilibrium (39.7,±,11.6%) and the ,/, ratios for the generation of 3HOH from either the D -[2- 3H]glucose anomers (70.9,±,12.6%) or the D -[5- 3H]glucose anomers (59.6,±,12.4%) indicated that a much greater fraction of ,- D -glucose-6-phosphate escapes from the process of enzyme-to-enzyme channelling in the islets exposed to 2.8,mM, rather than 8.3,mMD -glucose. These findings suggest, therefore, that the postulated process of enzyme-to-enzyme channelling involves mainly glucokinase. Copyright © 2004 John Wiley & Sons, Ltd. [source] | ||||||||||