Monitoring the Water Bodies of the Mackenzie Delta by Remote Sensing Methods

In the Mackenzie Delta, Northwest Territories, the thousands of lakes, ponds, channels and waterways, connected in an apparently chaotic manner, present a major logistical problem for collecting information regarding the nature of this complex hydrologic system. The use of satellite images gives an economical and synoptic view of this isolated region, while special analysis techniques simplify the environmental appraisal. The use of (mathematical) morphological analysis of the surface waters imaged by the satellite allowed the authors to distinguish all water bodies, even when they were at the limit of the spatial resolution of the sensor. The technique further permitted the classification of these water bodies by their inter- and intra-connectivity. Another technique, termed chromaticity analysis, allows for the removal of atmospheric differences among images, which in turn enables the use of surface calibration data from one date to be used on images of other dates. This method was also used to generate quantitative maps of suspended sediment concentration levels. Together, these techniques permit the assessment of the hydrologic flow (or its hindrance) of sediment and nutrients for the sustenance of aquatic flora and fauna. They further supply a method for the mapping of access routes by water craft to all parts of the Delta.Key words: mathematical morphology, chromaticity analysis, remote sensing, Landsat, Mackenzie Delta, suspensdeeddi ment, hydrologic networkMots clés: morphologie mathématique, analyse par chromaticité, télédétection, Landsat, Delta du Mackenzie, sediments en suspension, réseau hydrologiqu

L-Tryptophan Production by Auxotrophic and Analogue Resistant Mutants of Aureobacterium flavescens

A number of tyrosine plus phenylalanine double auxotrophic mutants were isolated by N-methyl-N-nitro-N-nitrosoguanidine (MNNG) treatment of a locally isolated strain of Aureobacterium flavescens of which 11A39 and 11A17 were selected on the basis of their tryptophan production in a mineral salt medium over other isolated mutant strains. The mutational block in the aromatic amino acid biosynthetic pathway of the selected double auxotrophs were determined. By controlling pH of the production medium to near neutrality, the active growth period could be extended up to 72 h and more tryptophan was accumulated compared to pH unregulated culture where the active growth ceased after 48 h. Further improvement of the tryptophan production has been achieved by stepwise isolation of a mutant strain resistant to the tryptophan analogues p-fluorotryptophan (FT) and 5-methyl tryptophan (MT) from the 11A39. Demand for L-tryptophan as food additive and therapeutic agent is increasing day by day throughout the World, particularly in the underdeveloped and developing countries like India. Still to date India depends on other countries for L-tryptophan. The aim of this work is to develop a potent high yielding, feed back insensitive mutant strain and optimization of its medium pH for maximum production of tryptophan

The meadow jumping mouse genome and transcriptome suggest mechanisms of hibernation [preprint]

Hibernating mammals exhibit medically relevant phenotypes, but the genetic basis of hibernation remains poorly understood. Using the meadow jumping mouse (Zapus hudsonius), we investigated the genetic underpinnings of hibernation by uniting experimental and comparative genomic approaches. We assembled a Z. hudsonius genome and identified widespread expression changes during hibernation in genes important for circadian rhythm, membrane fluidity, and cell cycle arrest. Tissue-specific gene expression changes during torpor encompassed Wnt signaling in the brain and structural and transport functions in the kidney brush border. Using genomes from the closely related Zapus oregonus (previously classified as Z. princeps) and leveraging a panel of hibernating and non-hibernating rodents, we found selective pressure on genes involved in feeding behavior, metabolism, and cell biological processes potentially important for function at low body temperature. Leptin stands out with elevated conservation in hibernating rodents, implying a role for this metabolic hormone in triggering fattening and hibernation. These findings illustrate that mammalian hibernation requires adaptation at all levels of organismal form and function and lay the groundwork for future study of hibernation phenotypes

The Caulobacter crescentus GTPase CgtA C is required for progression through the cell cycle and for maintaining 50S ribosomal subunit levels

The Obg subfamily of bacterial GTP-binding proteins are biochemically distinct from Ras-like proteins raising the possibility that they are not controlled by conventional guanine nucleotide exchange factors (GEFs) and/or guanine nucleotide activating proteins (GAPs). To test this hypothesis, we generated mutations in the Caulobacter crescentus obg gene ( cgtA C ) which, in Ras-like proteins, would result in either activating or dominant negative phenotypes. In C. crescentus , a P168V mutant is not activating in vivo , although in vitro , the P168V protein showed a modest reduction in the affinity for GDP. Neither the S173N nor N280Y mutations resulted in a dominant negative phenotype. Furthermore, the S173N was significantly impaired for GTP binding, consistent with a critical role of this residue in GTP binding. In general, conserved amino acids in the GTP-binding pocket were, however, important for function. To examine the in vivo consequences of depleting CgtA C , we generated a temperature-sensitive mutant, G80E. At the permissive temperature, G80E cells grow slowly and have reduced levels of 50S ribosomal subunits, indicating that CgtA C is important for 50S assembly and/or stability. Surprisingly, at the non-permissive temperature, G80E  cells  rapidly  lose  viability  and  yet  do not display an additional ribosome defect. Thus, the essential nature of the cgtA C gene does not appear to result from its ribosome function. G80E cells arrest as predivisional cells and stalkless cells. Flow cytometry on synchronized cells reveals a G1-S arrest. Therefore, CgtA C is necessary for DNA replication and progression through the cell cycle.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75652/1/j.1365-2958.2004.04354.x.pd

Delegation and coordination with multiple threshold public goods: experimental evidence

When multiple charities, social programs and community projects simultaneously vie for funding, donors risk mis-coordinating their contributions leading to an inefficient distribution of funding across projects. Community chests and other intermediary organizations facilitate coordination among donors and reduce such risks. To study this, we extend a threshold public goods framework to allow donors to contribute through an intermediary rather than directly to the public goods. Through a series of experiments, we show that the presence of an intermediary increases public good success and subjects’ earnings only when the intermediary is formally committed to direct donations to socially beneficial goods. Without such a restriction, the presence of an intermediary has a negative impact, complicating the donation environment, decreasing contributions and public good success.When multiple charities, social programs and community projects simultaneously vie for funding, donors risk mis-coordinating their contributions leading to an inefficient distribution of funding across projects. Community chests and other intermediary organizations facilitate coordination among donors and reduce such risks. To study this, we extend a threshold public goods framework to allow donors to contribute through an intermediary rather than directly to the public goods. Through a series of experiments, we show that the presence of an intermediary increases public good success and subjects’ earnings only when the intermediary is formally committed to direct donations to socially beneficial goods. Without such a restriction, the presence of an intermediary has a negative impact, complicating the donation environment, decreasing contributions and public good success