4,161 research outputs found
Combustion instability prediction using a nonlinear bipropellant vaporization model
Combustion instability prediction using nonlinear bipropellant vaporization mode
Evidence for ferredoxin glutamate synthase activity in grape shoot tissues
Research NoteFerredoxin glutamate synthase (ferredoxin glutamine: oxoglutarate aminotransferase, or Fd-GOGAT, EC 1.4.7.1) activity was detected in grapevine (Vitis vinifera L.). Highest Fd-GOGAT activity was found in lamina tissue. Moderate levels of activity were found in petiole, tendril, rachis, and flower tissues. No activity was detected in extracts from pedicel tissue. Western blotting with rice Fd-GOGAT antibodies resulted in a positive reaction with single grape protein band of 73 kDa in all tissue types tested
Crossed Module Bundle Gerbes; Classification, String Group and Differential Geometry
We discuss nonabelian bundle gerbes and their differential geometry using
simplicial methods. Associated to any crossed module there is a simplicial
group NC, the nerve of the 1-category defined by the crossed module and its
geometric realization |NC|. Equivalence classes of principal bundles with
structure group |NC| are shown to be one-to-one with stable equivalence classes
of what we call crossed module gerbes bundle gerbes. We can also associate to a
crossed module a 2-category C'. Then there are two equivalent ways how to view
classifying spaces of NC-bundles and hence of |NC|-bundles and crossed module
bundle gerbes. We can either apply the W-construction to NC or take the nerve
of the 2-category C'. We discuss the string group and string structures from
this point of view. Also a simplicial principal bundle can be equipped with a
simplicial connection and a B-field. It is shown how in the case of a
simplicial principal NC-bundle these simplicial objects give the bundle gerbe
connection and the bundle gerbe B-field
37 GHz methanol masers : Horsemen of the Apocalypse for the class II methanol maser phase?
We report the results of a search for class II methanol masers at 37.7, 38.3
and 38.5 GHz towards a sample of 70 high-mass star formation regions. We
primarily searched towards regions known to show emission either from the 107
GHz class II methanol maser transition, or from the 6.035 GHz excited OH
transition. We detected maser emission from 13 sources in the 37.7 GHz
transition, eight of these being new detections. We detected maser emission
from three sources in the 38 GHz transitions, one of which is a new detection.
We find that 37.7 GHz methanol masers are only associated with the most
luminous 6.7 and 12.2 GHz methanol maser sources, which in turn are
hypothesised to be the oldest class II methanol sources. We suggest that the
37.7 GHz methanol masers are associated with a brief evolutionary phase (of
1000-4000 years) prior to the cessation of class II methanol maser activity in
the associated high-mass star formation region.Comment: 14 pages, 4 figures, accepted for publication in Ap
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