41,812 research outputs found
Cell surface localization of tissue transglutaminase is dependent on a fibronectin-binding site in its N-terminal beta-sandwich domain
Increasing evidence indicates that tissue transglutaminase (tTG) plays a role in the assembly and remodeling of extracellular matrices and promotes cell adhesion. Using an inducible system we have previously shown that tTG associates with the extracellular matrix deposited by stably transfected 3T3 fibroblasts overexpressing the enzyme. We now show by confocal microscopy that tTG colocalizes with pericellular fibronectin in these cells, and by immunogold electron microscopy that the two proteins are found in clusters at the cell surface. Expression vectors encoding the full-length tTG or a N-terminal truncated tTG lacking the proposed fibronectin-binding site (fused to the bacterial reporter enzyme β-galactosidase) were generated to characterize the role of fibronectin in sequestration of tTG in the pericellular matrix. Enzyme-linked immunosorbent assay style procedures using extracts of transiently transfected COS-7 cells and immobilized fibronectin showed that the truncation abolished fibronectin binding. Similarly, the association of tTG with the pericellular matrix of cells in suspension or with the extracellular matrix deposited by cell monolayers was prevented by the truncation. These results demonstrate that tTG binds to the pericellular fibronectin coat of cells via its N-terminal β-sandwich domain and that this interaction is crucial for cell surface association of tTG
Characterization of heat transfer in nutrient materials, part 2
A thermal model is analyzed that takes into account phase changes in the nutrient material. The behavior of fluids in low gravity environments is discussed along with low gravity heat transfer. Thermal contact resistance in the Skylab food heater is analyzed. The original model is modified to include: equivalent conductance due to radiation, radial equivalent conductance, wall equivalent conductance, and equivalent heat capacity. A constant wall-temperature model is presented
Diffraction-limited CCD imaging with faint reference stars
By selecting short exposure images taken using a CCD with negligible readout
noise we obtained essentially diffraction-limited 810 nm images of faint
objects using nearby reference stars brighter than I=16 at a 2.56 m telescope.
The FWHM of the isoplanatic patch for the technique is found to be 50
arcseconds, providing ~20% sky coverage around suitable reference stars.Comment: 4 page letter accepted for publication in Astronomy and Astrophysic
A Bayesian Analogue of Gleason's Theorem
We introduce a novel notion of probability within quantum history theories
and give a Gleasonesque proof for these assignments. This involves introducing
a tentative novel axiom of probability. We also discuss how we are to interpret
these generalised probabilities as partially ordered notions of preference and
we introduce a tentative generalised notion of Shannon entropy. A Bayesian
approach to probability theory is adopted throughout, thus the axioms we use
will be minimal criteria of rationality rather than ad hoc mathematical axioms.Comment: 14 pages, v2: minor stylistic changes, v3: changes made in-line with
to-be-published versio
New Features of the Morphotropic Phase Boundary in the PbZr(1-x)TixO3 System
Recently a new monoclinic phase in the PbZr(1-x)TixO3 ceramic system has been
reported by Noheda et al. for the composition x= 0.48. In the present work,
samples with Ti contents of x= 0.47 and 0.50, which are both tetragonal below
their Curie points, have been investigated. In the sample with x= 0.50, the
tetragonal phase was found to transform to a monoclinic phase at about 200 K as
the temperature was lowered. The sample with x= 0.47 showed a complicated
region of phase coexistence between 440-320 K, becoming rhombohedral at around
300 K. No further symmetry change was found down to 20 K. Dielectric
measurements for these two samples are also reported. On the basis of these
results, a preliminary phase diagram is presented. Optimum compositional
homogeneity is needed to properly characterize the new monoclinic region.Comment: 5 pages, 7 PS figures embedded. RevTeX and epsf macros. Presented at
the 9th. European Meeting on Ferroelectricity, Prague, July 1999. To be
published in "Ferroelectrics
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