16,107 research outputs found
Spring and surface water quality of the Cyprus ophiolites
A survey of surface, spring and borehole waters associated with the ophiolite rocks of Cyprus shows five broad water types (1) Mg-HCO3, (2) Na-SO4-Cl-HCO3, (3) Na-Ca-Cl-SO4-OH-CO3, (4) Na-Cl-SO4 and (5) Ca-SO4. The waters represent a progression in chemical reactivity from surface waters that evolve within a groundwater setting due to hydrolysis of the basic/ultrabasic rock as modified by CO2-weathering. An increase in salinity is also observed which is due to mixing with a saline end-member (modified sea-water) and dissolution of gypsum/anhydrite. In some cases, the waters have pH values greater than 11. Such high values are associated with low temperature serpentinisation reactions. The system is a net sink for CO2. This feature is related not only to the hydrolysis of the primary minerals in the rock, but also to CaCO3 or Ca-Mg-CO3 solubility controls. Under hyperalkaline conditions, virtually all the carbon dioxide is lost from the water due to the sufficiently high calcium levels and carbonate buffering is then insignificant. Calcium sulphate solubility controls may also be operative when calcium and sulphate concentrations are particularly high
Noncommutative topology and Jordan operator algebras
Jordan operator algebras are norm-closed spaces of operators on a Hilbert
space with for all . We study noncommutative topology,
noncommutative peak sets and peak interpolation, and hereditary subalgebras of
Jordan operator algebras. We show that Jordan operator algebras present perhaps
the most general setting for a `full' noncommutative topology in the
C*-algebraic sense of Akemann, L. G. Brown, Pedersen, etc, and as modified for
not necessarily selfadjoint algebras by the authors with Read, Hay and other
coauthors. Our breakthrough relies in part on establishing several strong
variants of C*-algebraic results of Brown relating to hereditary subalgebras,
proximinality, deeper facts about for a left ideal in a C*-algebra,
noncommutative Urysohn lemmas, etc. We also prove several other approximation
results in -algebras and various subspaces of -algebras, related to
open and closed projections, and technical -algebraic results of Brown.Comment: Revision, many typos corrected and exposition improved in places.
Section 2 expanded with some applications of the main theorem of that sectio
Metric characterizations II
The present paper is a sequel to our paper "Metric characterization of
isometries and of unital operator spaces and systems". We characterize certain
common objects in the theory of operator spaces (unitaries, unital operator
spaces, operator systems, operator algebras, and so on), in terms which are
purely linear-metric, by which we mean that they only use the vector space
structure of the space and its matrix norms. In the last part we give some
characterizations of operator algebras (which are not linear-metric in our
strict sense described in the paper).Comment: Presented at the AMS/SAMS Satellite Conference on Abstract Analysis,
University of Pretoria, South Africa, 5-7 December 2011. Revision of
2/24/2012 (Examples after theorem 3.2 added
Open partial isometries and positivity in operator spaces
We study positivity in C*-modules and operator spaces using open tripotents,
and an ordered version of the `noncommutative Shilov boundary'. Because of
their independent interest, we also systematically study open tripotents and
their properties.Comment: To appea
Study on the effect of contamination on the performance of X-ray telescopes
Modifications were made to the X-ray reflectometer located at the Space Sciences Laboratory, Marshall Space Flight Center. One was an automatic drive for the Large Micrometer Head. This system, interfaced with the Hewlett Packard Computer System, is used to record data and provides the X-ray reflectometer with an automated data-taking capability. Using this system, a complete scatter curve can be obtained automatically. Previously, it was necessary to manually reset the system after recording for each data point in the scatter curve. The second modification provided an externally controlled electrical drive to move the microfocus X-ray source along its axis. With this modification, one can translate the X-ray source while it is operating to locate the position providing maximum count rate
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