Abstract:Emerald from the deposits at Poona shows micrometre-scale chemical, optical, and cathodoluminescence zonation. This zonation, combined with fluid inclusion and isotope studies, indicates early emerald precipitation from a single-phase saline fluid of approximately 12 weight percent NaCl equivalent, over the temperature range of 335-525 • C and pressures ranging from 70 to 400 MPa. The large range in pressure and temperature likely reflects some post entrapment changes and re-equilibration of oxygen isotopes. Secondary emerald-hosted fluid inclusions indicate subsequent emerald precipitation from higher salinity fluids. Likewise, the δ 18 O-δD of channel fluids extracted from Poona emerald is consistent with multiple origins yielding both igneous and metamorphic signatures. The combined multiple generations of emerald precipitation, different fluid compositions, and the presence of both metamorphic and igneous fluids trapped in emerald, likely indicate a protracted history of emerald precipitation at Poona conforming to both an igneous and a metamorphic origin at various times during regional lower amphibolite to greenschist facies metamorphism over the period~2710-2660 Ma.
This note states results extending those of Nash [2] on isometric embeddings of Riemannian manifolds in euclidean spaces; proofs and further details will be given elsewhere.Let M be a d-dimensional C 00 manifold. For convenience, we assume throughout that manifolds, whether compact or not, are connected. A metric on M is defined to be a quadratic form on the tangent bundle of M ; note that there is no assumption of nondegeneracy. We shall assume that all metrics are C 00 . A Riemannian metric on M is a metric whose restriction to the tangent space T q at a point qÇzM is positive definite, for all g£Af. A pseudo-Riemannian, or indefinite, metric is a metric whose restriction to the tangent space at each point is nondegenerate; if the nondegenerate restriction to T q has n negative eigenvalues and p positive eigenvalues, with p+n=d } the metric is said to have signature (p, n) at q. The connectedness of M implies that the signature is independent of the choice of qÇzM.
The fission cross sections of the uranium isotopes, 234 and 236, have been measured from their thresholds to 4.0-Mev neutron energy by use of neutrons from the T(£,n)He 3 reaction. Neutron energy spread varied from 60 to 100 kev for most points.U 234 has a threshold at about 300 kev, rises to 1.24 barns at 850 kev, dips to 1.08 barns at 1.06 Mev, rises to 1.47, barns at 1.9 Mev, dips to 1.40 barns at 2.4 Mev, and then rises to 1.55 barns at 4.0 Mev. Variations in between these points appear smooth with the energy spread present in the neutron beam.Similarly, U 236 has a threshold at about 670 kev, rises to 0.36 barn at 970 kev and remains nearly constant to 1.04 Mev when it again rises, reaching 0.75 barn at 1.4 Mev, falling to 0.66 barn at 1.56 Mev, rising to 0.89 barn at 2.5 Mev, falling to 0.87 barn at 2.7 Mev, and then rising to 0.99 barn at 4.0 Mev.The thresholds referred to are the energies at which the cross sections are only about 1% of their values on the relatively flat portion of the curve between 2 and 3 Mev.Results are believed to be accurate to 6.0%.
This report was prepared as an account of work sponsored by the United Stfftes Government. Neither the United States nor the United States Atomic Energy Co-«mres:on. mx any of their employees, nor any of their contractors, subcontrectoi., or their employees, makes any warranty, express or implied, or assumes any legal liability or respcnsnilit/ for the accuracy, completeness or ustfu f->«ss of any id'ormetion, .operatus, product or proces* drsclosed, or rapiasenis that its use would not inning* privately owned rights. ORNI-4819 OC-23-Radioisotope aad Radiation Applications Contract No. V-7405-eng-26
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