A cosmopolitan late Ediacaran biotic assemblage: new fossils from Nevada and Namibia support a global biostratigraphic link.

Owing to the lack of temporally well-constrained Ediacaran fossil localities containing overlapping biotic assemblages, it has remained uncertain if the latest Ediacaran (ca 550-541 Ma) assemblages reflect systematic biological turnover or environmental, taphonomic or biogeographic biases. Here, we report new latest Ediacaran fossil discoveries from the lower member of the Wood Canyon Formation in Nye County, Nevada, including the first figured reports of erniettomorphs, Gaojiashania, Conotubus and other problematic fossils. The fossils are spectacularly preserved in three taphonomic windows and occur in greater than 11 stratigraphic horizons, all of which are below the first appearance of Treptichnus pedum and the nadir of a large negative δ13C excursion that is a chemostratigraphic marker of the Ediacaran-Cambrian boundary. The co-occurrence of morphologically diverse tubular fossils and erniettomorphs in Nevada provides a biostratigraphic link among latest Ediacaran fossil localities globally. Integrated with a new report of Gaojiashania from Namibia, previous fossil reports and existing age constraints, these finds demonstrate a distinctive late Ediacaran fossil assemblage comprising at least two groups of macroscopic organisms with dissimilar body plans that ecologically and temporally overlapped for at least 6 Myr at the close of the Ediacaran Period. This cosmopolitan biotic assemblage disappeared from the fossil record at the end of the Ediacaran Period, prior to the Cambrian radiation.

Mechanisms of endotoxin tolerance. The role of the spleen.

Splenectomy markedly impaired the production of circulating anti-endotoxin antibodies during the initial 10 days after .v. administration of a Boivin preparation of Escherichia coli endotoxin (ET) in both rabbit and man. Increase in antibodies with secondary (flocculating and bactericidal) activities were virtually abolished, whereas increases in antibodies with primary (binding) activity were significantly reduced. On the basis of these findings, splenectomized rabbit and man were employed to test the hypothesis that the early phase (less than 72 h) of pyrogenic tolerance to endotoxin is independent of anti-endotoxin antibody but that such antibody contributes significantly to the later phase (less than or equal to 72 h) of tolerance. In the splenectomized rabbit, the initial pyrogenic reponses to ET and the subsequent tolerant responses at 24 and 48 h were comparable to sham-operated controls...

TRIDENT high-energy-density facility experimental capabilities and diagnostics.

The newly upgraded TRIDENT high-energy-density (HED) facility provides high-energy short-pulse laser-matter interactions with powers in excess of 200 TW and energies greater than 120 J. In addition, TRIDENT retains two long-pulse (nanoseconds to microseconds) beams that are available for simultaneous use in either the same experiment or a separate one. The facility's flexibility is enhanced by the presence of two separate target chambers with a third undergoing commissioning. This capability allows the experimental configuration to be optimized by choosing the chamber with the most advantageous geometry and features. The TRIDENT facility also provides a wide range of standard instruments including optical, x-ray, and particle diagnostics. In addition, one chamber has a 10 in. manipulator allowing OMEGA and National Ignition Facility (NIF) diagnostics to be prototyped and calibrated.

Computed tomography in the evaluation of thyroid disease.

Traditionally, thyroid imaging has been performed primarily using radionuclide scanning. High-resolution computed tomography (CT) was performed in 18 patients to evaluate the CT appearance of various thyroid abnormalities including diffuse toxic goiter, multinodular goiter, Hashimoto thyroiditis, thyroid adenoma, and malignant thyroid tumors. CT images of the thyroid were correlated with radionuclide scanning, surgical findings, and clinical and laboratory results. CT provided a complementary method for evaluation of the thyroid by defining the morphology of the thyroid gland and more precisely defining the anatomic extent of thyroid abnormalities in relation to the normal structures of the neck and mediastinum.