Numerical arc segmentation algorithm for a radio conference: A software tool for communication satellite systems planning

The Numerical Arc Segmentation Algorithm for a Radio Conference (NASARC) provides a method of generating predetermined arc segments for use in the development of an allotment planning procedure to be carried out at the 1988 World Administrative Radio Conference (WARC) on the Use of the Geostationary Satellite Orbit and the Planning of Space Services Utilizing It. Through careful selection of the predetermined arc (PDA) for each administration, flexibility can be increased in terms of choice of system technical characteristics and specific orbit location while reducing the need for coordination among administrations. The NASARC software determines pairwise compatibility between all possible service areas at discrete arc locations. NASARC then exhaustively enumerates groups of administrations whose satellites can be closely located in orbit, and finds the arc segment over which each such compatible group exists. From the set of all possible compatible groupings, groups and their associated arc segments are selected using a heuristic procedure such that a PDA is identified for each administration. Various aspects of the NASARC concept and how the software accomplishes specific features of allotment planning are discussed

Modification of a Hydrophobic Layer by a Point Mutation in Syntaxin 1A Regulates the Rate of Synaptic Vesicle Fusion

Both constitutive secretion and Ca(2+)-regulated exocytosis require the assembly of the soluble N-ethylmaleimide–sensitive factor attachment protein receptor (SNARE) complexes. At present, little is known about how the SNARE complexes mediating these two distinct pathways differ in structure. Using the Drosophila neuromuscular synapse as a model, we show that a mutation modifying a hydrophobic layer in syntaxin 1A regulates the rate of vesicle fusion. Syntaxin 1A molecules share a highly conserved threonine in the C-terminal +7 layer near the transmembrane domain. Mutation of this threonine to isoleucine results in a structural change that more closely resembles those found in syntaxins ascribed to the constitutive secretory pathway. Flies carrying the I254 mutant protein have increased levels of SNARE complexes and dramatically enhanced rate of both constitutive and evoked vesicle fusion. In contrast, overexpression of the T254 wild-type protein in neurons reduces vesicle fusion only in the I254 mutant background. These results are consistent with molecular dynamics simulations of the SNARE core complex, suggesting that T254 serves as an internal brake to dampen SNARE zippering and impede vesicle fusion, whereas I254 favors fusion by enhancing intermolecular interaction within the SNARE core complex

Suitability of northern Michigan soils for the disposal of zinc and copper industrial wastes.

http://deepblue.lib.umich.edu/bitstream/2027.42/52894/1/1327.pdfDescription of 1327.pdf : Access restricted to on-site users at the U-M Biological Station

Extracting Spectral Information from AND/OR Representations

Spectral information can be used for many CAD system tasks including synthesis, verication and test vector generation. AND/OR graphs are also useful for representing functions in CAD systems since they can oer advantages with respect to storage and representation of incompletely specied relations. We analyze the problem of extracting spectral information from AND/OR graphs. It is shown that spectral information may be calculated directly from output probabilities and a method for extracting output probabilities from AND/OR graphs is described with experimental results provided. 1 Introduction An ecient method for representing a Boolean function is mandatory for a CAD tool to be practically useful. Although many representations have been used in the past, each type has its' own disadvantages. Recently, the AND/OR decision graph has been proposed for representing functions in CAD tools. An overview of the use of this graph in the digital logic arena is given in [4]. The AND/OR grap..

A model for sealing plasmalemmal damage in neurons and other eukaryotic cells

Plasmalemmal repair is necessary for survival of damaged eukaryotic cells. Ca2 influx through plasmalemmal disruptions activates calpain, vesicle accumulation at lesion sites, and membrane fusion proteins; Ca2 influx also initiates competing apoptotic pathways. Using the formation of a dye barrier (seal) to assess plasmalemmal repair, we now report that B104 hippocampal cells with neurites transected nearer ( 50 m)to the soma seal at a lower frequency and slower rate compared to cells with neurites transected farther ( 50 m) from the soma. Analogs of cAMP, including protein kinase A (PKA)-specific and Epac-specific cAMP, each increase the frequency and rate of sealing and can even initiate sealing in the absence of Ca2 influx at both transection distances. Furthermore, Epac activates a cAMP-dependent, PKA-independent, pathway involved in plasmalemmal sealing. The frequency and rate of plasmalemmal sealing are decreased by a small molecule inhibitor of PKA targeted to its catalytic subunit (KT5720), a peptide inhibitor targeted to its regulatory subunits (PKI), an inhibitor of a novel PKC (an nPKC pseudosubstrate fragment), and an antioxidant (melatonin). Given these and other data, we propose a model for redundant parallel pathways of Ca2 -dependent plasmalemmal sealing of injured neurons mediated in part by nPKCs, cytosolic oxidation, and cAMP activation of PKA and Epac. We also propose that the evolutionary origin of these pathways and substances was to repair plasmalemmal damage in eukaryotic cells. Greater understanding of vesicle interactions, proteins, and pathways involved in plasmalemmal sealing should suggest novel neuroprotective treatments for traumatic nerve injuries and neurodegenerative disorders.This work was funded by grants from the Lone Star Paralysis Foundation.Neuroscienc