948 resultados para Mechanisms of coordination and integration


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Using plant level data from a global survey with multiple time frames, one begun in the late 1990s, this paper introduces measures of supply chain integration and discusses the dynamic relationship between the level of integration and a set of internal and external performance measurements. Specifically, data from Hungary, The Netherlands and The People’s Republic of China are used in the analyses. The time frames considered range from the late 1990s till 2009, encompassing major changes and transitions. Our results seem to indicate that SCI has an underlying structure of four sets of indicators, namely: (1) delivery frequency from the supplier or to the customer; (2) sharing internal processes with suppliers; (3) sharing internal processes with buyers and (4) joint facility location with partners. The differences between groups in terms of several performance measures proved to be small, being mostly statistically insignificant - but looking at the ANOVA table we can conclude that in this sample of companies those having joint location with their partners seem to outperform others.

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This study analyzed the health and overall landcover of citrus crops in Florida. The analysis was completed using Landsat satellite imagery available free of charge from the University of Maryland Global Landcover Change Facility. The project hypothesized that combining citrus production (economic) data with citrus area per county derived from spectral signatures would yield correlations between observable spectral reflectance throughout the year, and the fiscal impact of citrus on local economies. A positive correlation between these two data types would allow us to predict the economic impact of citrus using spectral data analysis to determine final crop harvests.

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An extensive study of the reaction pathways of 1,1-dicyclopropyl ethylene, cis- and trans- 1,2-dicyclopropylethylenes has been undertaken with different electrophiles 4-methyl-1,2,4-triazoline-3,5-dione (MTAD), tetracyanoethylene (TCNE), and singlet oxygen $\rm(\sp1O\sb2).$ Comparison of reactivity and reaction mechanisms among the electrophiles is investigated. Singlet oxygen exhibits significantly lower reactivity compared to the other electrophiles. MTAD and TCNE react with dicyclopropylethylenes to produce predominantly $\sp{\prime\prime}2+2\sp{\prime\prime}$ adducts and a small amount of the "ene" adducts. The $\sp{\prime\prime}2+2\sp{\prime\prime}$ is the major product presumably because of the high activation energy leading to the highly strained "ene" products. Solvent trapping studies provide strong evidence of a "stepwise" mechanism, involving a zwitterionic or aziridinium imide as an intermediate from the study of the reactions products of dicyclopropylethylenes and MTAD. ^

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In the Florida Everglades, tree islands are conspicuous heterogeneous elements in a complex wetland landscape. I investigated the effects of increased freshwater flow in southern Everglades seasonally flooded tree islands, and characterized biogeochemical interactions among tree islands and the marsh landscape matrix, specifically examining hydrologic flows of nitrogen (N), and landscape N sequestration capacity. I utilized ecological trajectories of key ecosystem variables to differentiate effects of increased sheetflow and hydroperiod. I utilized stable isotope analyses and nutrient content of tree island ecosystem components to test the hypothesis that key processes in tree island nitrogen cycling would favor ecosystem N sequestration. I combined estimates of tree island ecosystem N standing stocks and fluxes, soil and litter N transformation rates, and hydrologic inputs of N to quantify the net sequestration of N by a seasonally flooded tree island. ^ Results show that increased freshwater flow to seasonally flooded tree islands promoted ecosystem oligotrophy, whereas reduced flows allowed some plant species to cycle P less efficiently. As oligotrophy is a defining parameter of Everglades wetlands, and likely promotes belowground production and peat development, reintroducing freshwater flow from an upstream canal had a favorable effect on ecosystem dynamics of tree islands in the study area. Important factors influencing the stable isotopic composition of nitrogen and carbon were: (1) a contribution to soil N by soil invertebrates, animal excrement, and microbes, (2) a possible NO3 source from an upstream canal and an "open" ecosystem N cycle, and (3) greater availability of phosphorus in tree islands relative to the marsh landscape, suggesting that tree island N cycling favors N sequestration. Hydrologic sources of N were dominated by surface water loads of NO3- and NH 4+, and an important soil N transformation promoting the net loss of surface water DIN was nitrate immobilization associated with soils and surficial leaf litter. The net inorganic N sequestration capacity of a seasonally flooded tree island was 50 g yr-1 m -2. Thus, tree islands likely have an important function in landscape sequestration of inorganic N, and may reduce significant anthropogenic N loads to downstream coastal systems. ^

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The serine/threonine kinase LKB1 is a regulator of critical events including development and stress responses in metazoans. The current study was undertaken to determine the function of LKB1 in Dictyostelium . During multicellular development and in response to stress insult, an apparent increase in the DdLKB1 kinase activity was observed. Depletion of DdLKB1 with a knockdown construct led to aberrant development; a severe reduction in prespore cell differentiation and a precocious induction of prestalk cells, which were reminiscent of cells lacking GSK3, a well known cell-fate switch. Furthermore, DdLKB1 depleted cells displayed lower GSK3 activity than wild type cells in response to cAMP stimulation during development and failed to activate AMPK, a well known LKB1 target in mammals, in response to cAMP and stress insults. These results suggest that DdLKB1 positively regulates both GSK3 and AMPK during Dictyostelium development, and DdLKB1 is necessary for AMPK activation during stress response regulation. No apparent GSK3 activation was observed in response to stress insults. Spatial and temporal regulation of phosphatidylinositol-(3,4,5)-triphosphate (PIP3) along the membrane of polarized cells is important for efficient chemotaxis. A REMI screen for PIP3 suppressors in the absence of stimulation led to the identification of SodC as PIP3 regulator. Consistent with their higher PIP3 levels, sodC− cells showed defects in chemotaxis and exhibited higher intra-cellular superoxide levels. Protein localization studies along with observations from GPI specific PI-PLC treatment of wild-type cells suggested that SodC is a GPI anchored outer-membrane protein. SodC showed superoxide dismutase activity in vitro, and motility defects of sodC− cells can be rescued by expressing the intact SodC but not by the mutant SodC, which has point mutations that affect its dismutase function. Treatment of sodC− cells with LY294002, a pharmacological inhibitor of PI3K, partially rescued the polarization and chemoattractant sensing defects but not motility defects. Consistent with increased intracellular superoxide levels, sodC − cells also exhibited higher basal Ras activity, an upstream regulator of PI3K, which can be suppressed by a cell permeable superoxide scavenger, XTT, indicating that SodC is important in regulation of intracellular superoxide levels thereby regulating the Ras activity and PIP3 levels at the membrane.

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Chloroperoxidase (CPO) is a heme-containing glycoprotein secreted by the marine fungus Caldariomyces fumago. Chloroperoxidase contains one ferriprotoporphyrin IX prosthetic group per molecule and catalyzes a variety of reactions, such as halogenation, peroxidation and epoxidation. The versatile catalytic activities of CPO coupled with the increasing demands for chiral synthesis have attracted an escalating interest in understanding the mechanistic and structural properties of this enzyme. In order to better understand the mechanisms of CPO-catalyzed enantioselective reactions and to fine-tune the catalytic properties of chloroperoxidase, asparagine 74 (N74) located in the narrow substrate access channel of CPO was replaced by a bulky, nonpolar valine and a polar glutamine using site-directed mutagenesis. The CPO N74 mutants displayed significantly enhanced activity toward nonpolar substrates compared to wild-type CPO as a result of changes in space and polarity of the heme distal environment. More interestingly, N74 mutants showed dramatically decreased chlorination and catalase activity but significantly enhanced epoxidation activity as a consequence of improved kinetic perfection introduced by the mutation as reflected by the favorable changes in k cat and kcat/KM of these reactions. It is also noted that the N74V mutant is capable of decomposing cyanide, the most notorious poison for many hemoproteins, as judged by the unique binding behavior of N74V with potassium cyanide. Histidine 105 (H105) was replaced by a nonpolar amino acid alanine using site-directed mutagenesis. The CPO H105 mutant (H105A) displayed dramatically decreased chlorination and catalase activity possibly because of the decreased polarity in the heme distal environment and loss of the hydrogen bonds between histidine 105 and glutamic acid 183. However, significantly increased enantioselectivity was observed for the epoxidation of bulky styrene derivatives. Furthermore, my study provides strong evidence for the proposed histidine/cysteine ligand switch in chloroperoxidase, providing experimental support for the structure of the 420-nm absorption maximum for a number of carbon monoxide complexes of heme-thiolate proteins. For the NMR study, [dCPO(heme)] was produced using 90% deuterated growth medium with excess heme precursors and [dCPO(Phe)] was grown in the same highly deuterated medium that had been supplemented with excess natural phenylalanine. To make complete heme proton assignments, NMR spectroscopy has been performed for high-resolution structural characterization of [dCPO(heme)] and [dCPO(Phe)] to achieve unambiguous and complete heme proton assignments, which also allows important amino acids close to the heme active center to be determined.

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A number of factors influence the information processing needs of organizations, particularly with respect to the coordination and control mechanisms within a hotel. The authors use a theoretical framework to illustrate alternative mechanisms that can be used to coordinate and control hotel operations.

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This research sought to determine the implications of a non-traded differentiated commodity produced with increasing returns to scale, for the welfare of countries that allowed free international migration. We developed two- and three-country Ricardian models in which labor was the only factor of production. The countries traded freely in homogeneous goods produced with constant returns to scale. Each also had a non-traded differentiated good sector where production took place using increasing returns to scale technology. Then we allowed for free international migration between two of the countries and observed what happened to welfare in both countries as indicated by their per capita utilities in the new equilibrium relative to their pre-migration utilities. ^ Preferences of consumers were represented by a two-tier utility function [Dixit and Stiglitz 1977]. As migration took place it impacted utility in two ways. The expanding country enjoyed the positive effect of increased product diversity in the non-traded good sector. However, it also suffered adverse terms-of-trade as its production cost declined. The converse was true for the contracting country. To determine the net impact on welfare we derived indirect per capita utility functions of the countries algebraically and graphically. Then we juxtaposed the graphs of the utility functions to obtain possible general equilibria. These we used to observe the welfare outcomes. ^ We found that the most likely outcomes were either that both countries gained, or one country lost while the other gained. We were, however, able to generate cases where both countries lost as a result of allowing free inter-country migration. This was most likely to happen when the shares of income spent on each country's export good differed significantly. In the three country world when we allowed two of the countries to engage in preferential trading arrangements while imposing a prohibitive tariff on imports from the third country welfare of the partner countries declined. When inter-union migration was permitted welfare declined even further. This we showed was due to the presence of the non-traded good sector. ^

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An extensive study of the reaction pathways of 1,1- dicyclopropyl ethylene, cis- and trans- 1,2-dicyclopropylethylenes has been undertaken with different electrophiles 4-methyl-1,2,4- triazoline-3,5-dione (MTAD), tetracyanoethylene (TCNE), and singlet oxygen (102). Comparison of reactivity and reaction mechanisms among the electrophiles is investigated. Singlet oxygen exhibits significantly lower reactivity compared to the other electrophiles. MTAD and TCNE react with dicyclopropylethylenes to produce predominantly "2+2" adducts and a small amount of the "ene" adducts. The "2+2" is the major product presumably because of the high activation energy leading to the highly strained "ene" products. Solvent trapping studies provide strong evidence of a "stepwise" mechanism, involving a zwitterionic or aziridinium imide as an intermediate from the study of the reactions products of dicyclopropylethylenes and MTAD.

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The presence of inhibitory substances in biological forensic samples has, and continues to affect the quality of the data generated following DNA typing processes. Although the chemistries used during the procedures have been enhanced to mitigate the effects of these deleterious compounds, some challenges remain. Inhibitors can be components of the samples, the substrate where samples were deposited or chemical(s) associated to the DNA purification step. Therefore, a thorough understanding of the extraction processes and their ability to handle the various types of inhibitory substances can help define the best analytical processing for any given sample. A series of experiments were conducted to establish the inhibition tolerance of quantification and amplification kits using common inhibitory substances in order to determine if current laboratory practices are optimal for identifying potential problems associated with inhibition. DART mass spectrometry was used to determine the amount of inhibitor carryover after sample purification, its correlation to the initial inhibitor input in the sample and the overall effect in the results. Finally, a novel alternative at gathering investigative leads from samples that would otherwise be ineffective for DNA typing due to the large amounts of inhibitory substances and/or environmental degradation was tested. This included generating data associated with microbial peak signatures to identify locations of clandestine human graves. Results demonstrate that the current methods for assessing inhibition are not necessarily accurate, as samples that appear inhibited in the quantification process can yield full DNA profiles, while those that do not indicate inhibition may suffer from lowered amplification efficiency or PCR artifacts. The extraction methods tested were able to remove >90% of the inhibitors from all samples with the exception of phenol, which was present in variable amounts whenever the organic extraction approach was utilized. Although the results attained suggested that most inhibitors produce minimal effect on downstream applications, analysts should practice caution when selecting the best extraction method for particular samples, as casework DNA samples are often present in small quantities and can contain an overwhelming amount of inhibitory substances.

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The serine/threonine kinase LKB1 is a regulator of critical events including development and stress responses in metazoans. The current study was undertaken to determine the function of LKB1 in Dictyostelium. During multicellular development and in response to stress insult, an apparent increase in the DdLKB1 kinase activity was observed. Depletion of DdLKB1 with a knockdown construct led to aberrant development; a severe reduction in prespore cell differentiation and a precocious induction of prestalk cells, which were reminiscent of cells lacking GSK3, a well known cell-fate switch. Furthermore, DdLKB1 depleted cells displayed lower GSK3 activity than wild type cells in response to cAMP stimulation during development and failed to activate AMPK, a well known LKB1 target in mammals, in response to cAMP and stress insults. These results suggest that DdLKB1 positively regulates both GSK3 and AMPK during Dictyostelium development, and DdLKB1 is necessary for AMPK activation during stress response regulation. No apparent GSK3 activation was observed in response to stress insults. Spatial and temporal regulation of phosphatidylinositol-(3,4,5)-triphosphate (PIP3) along the membrane of polarized cells is important for efficient chemotaxis. A REMI screen for PIP3 suppressors in the absence of stimulation led to the identification of SodC as PIP3 regulator. Consistent with their higher PIP3 levels, sodC- cells showed defects in chemotaxis and exhibited higher intra-cellular superoxide levels. Protein localization studies along with observations from GPI specific PI-PLC treatment of wild-type cells suggested that SodC is a GPI anchored outer-membrane protein. SodC showed superoxide dismutase activity in vitro, and motility defects of sodC- cells can be rescued by expressing the intact SodC but not by the mutant SodC, which has point mutations that affect its dismutase function. Treatment of sodC- cells with LY294002, a pharmacological inhibitor of PI3K, partially rescued the polarization and chemoattractant sensing defects but not motility defects. Consistent with increased intracellular superoxide levels, sodC- cells also exhibited higher basal Ras activity, an upstream regulator of PI3K, which can be suppressed by a cell permeable superoxide scavenger, XTT, indicating that SodC is important in regulation of intracellular superoxide levels thereby regulating the Ras activity and PIP3 levels at the membrane.

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Arsenic is a ubiquitous environmental toxic substance. As a consequence of continual exposure to arsenic, nearly every organism, from Escherichia coli to humans have evolved arsenic detoxification pathways. One of the pathways is extrusion of arsenic from inside the cells, thereby conferring resistance. The R773 arsRDABC operon in E. coli encodes an ArsAB efflux pump that confers resistance to arsenite. ArsA is the catalytic subunit of the pump, while ArsB forms the oxyanion conducting pathway. ArsD is an arsenite metallochaperone that binds arsenite and transfers it to ArsA. The interaction of ArsA and ArsD allows for resistance to As(III) at environmental concentrations. The interaction between ArsA ATPase and ArsD metallochaperone was examined. A quadruple mutant in the arsD gene encoding a K2A/K37A/K62A/K104A ArsD is unable to interact with ArsA. An error-prone mutagenesis approach was used to generate random mutations in the arsA gene that restored interaction with the quadruple arsD mutant in yeast two-hybrid assays. Three such mutants encoding Q56R, F120I and D137V ArsA were able to restore interaction with the quadruple ArsD mutant. Structural models generated by in silico docking suggest that an electrostatic interface favors reversible interaction between ArsA and ArsD. Mutations in ArsA that propagate changes in hydrogen bonding and salt bridges to the ArsA-ArsD interface also affect their interactions. The second objective was to examine the mechanism of arsenite resistance through methylation and subsequent volatilization. Microbial ArsM (As(III) S-adenosylmethyltransferase) catalyzes the formation of trimethylarsine as the volatile end product. The net result is loss of arsenic from cells. The gene for CrArsM from the eukaryotic green alga Chlamydomonas reinhardtii was chemically synthesized and expressed in E. coli. The purified protein catalyzed the methylation of arsenite into methyl-, dimethyl- and trimethyl products. Synthetic purified CrArsM was crystallized in an unliganded form. Biochemical and biophysical studies conducted on CrArsM sheds new light on the pathways of biomethylation. While in microbes ArsM detoxifies arsenic, the human homolog, hAS3MT, converts inorganic arsenic into more toxic and carcinogenic forms. An understanding of the enzymatic mechanism of ArsM will be critical in deciphering its parallel roles in arsenic detoxification and carcinogenesis.

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The exponential growth of studies on the biological response to ocean acidification over the last few decades has generated a large amount of data. To facilitate data comparison, a data compilation hosted at the data publisher PANGAEA was initiated in 2008 and is updated on a regular basis (doi:10.1594/PANGAEA.149999). By January 2015, a total of 581 data sets (over 4 000 000 data points) from 539 papers had been archived. Here we present the developments of this data compilation five years since its first description by Nisumaa et al. (2010). Most of study sites from which data archived are still in the Northern Hemisphere and the number of archived data from studies from the Southern Hemisphere and polar oceans are still relatively low. Data from 60 studies that investigated the response of a mix of organisms or natural communities were all added after 2010, indicating a welcomed shift from the study of individual organisms to communities and ecosystems. The initial imbalance of considerably more data archived on calcification and primary production than on other processes has improved. There is also a clear tendency towards more data archived from multifactorial studies after 2010. For easier and more effective access to ocean acidification data, the ocean acidification community is strongly encouraged to contribute to the data archiving effort, and help develop standard vocabularies describing the variables and define best practices for archiving ocean acidification data.

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This research is funded by UK Medical Research Council grant number MR/L011115/1

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This research is funded by UK Medical Research Council grant number MR/L011115/1. We would like to thank the 105 experts in behaviour change who have committed their time and offered their expertise for study 2 of this research. We are also very grateful to all those who sent us peer-reviewed behaviour change intervention descriptions for study 1. Finally, we would like thank Dr. Emma Beard and Dr. Dan Dediu for their statistical input and to all the researchers, particularly Holly Walton, who have assisted in the coding of papers for study 1.