Pliocene and Pleistocene geologic and climatic evolution in the San Luis Valley of south-central Colorado

Sediments of the Alamosa Formation spanning the upper part of the Gauss and most of the Matuyama Chrons were recovered by coring in the high (2300 m) San Luis Valley of south-central Colorado. The study site is located at the northern end of the Rio Grande rift. Lithologic changes in the core sediments provide evidence of events leading to integration of the San Luis drainage basin into the Rio Grande. The section, which includes the Huckleberry Ridge Ash (2.02 Ma) and spans the entire Matuyama Chron, contains pollen, and invertebrate and vertebrate fossils. Stable isotope analyses of inorganic and biogenic carbonate taken over most of the core indicate substantially warmer temperatures than occur today in the San Luis Valley. At the end of the Olduvai Subchron, summer precipitation decreased, summer pan evaporation increased, and temperatures increased slightly compared to the earlier climate represented in the core. By the end of the Jaramillo Subchron, however, cold/wet and warm/dry cycles become evident and continue into the cold/wet regime associated with the deep-sea oxygen-isotope Stage 22 glaciation previously determined from outcrops at the same locality. Correspondence between the Hansen Bluff climatic record and the deep-sea oxygen-isotope record (oxygen-isotope stages from about 110-18) is apparent, indicating that climate at Hansen Bluff was responding to global climatic changes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29956/1/0000316.pd

Reoperation following direct myocardial revascularization.

Among the 5507 patients who underwent aortocoronary bypass between October 1969 and June 1975, 41 patients (0.007%) developed recurrent angina and required reoperation. The factors necessitating reoperation were graft thrombosis in 10 patients (24%), progression of disease in 12 (29%), graft thrombosis and critical unbypassed lesions in one (2.4%), graft failure and progression of disease in in 12 (29%), graft failure and critical unbypassed lesions in four (10%), and all three factors in two patients (4.8%). Among 10 patients with 50% lesions present but not bypassed at the initial operation, nine of these lesions progressed to significant stenosis and in five patients this was the sole reason for reoperation. At the second operation, total revascularization was achieved in 32 patients (78%). One patient (2%) experienced a perioperative myocardial infarction and one patient (2%) died. This study emphasizes the importance of "complete" revascularization at initial operation, the concept that arteries with 50% obstruction should be routinely bypassed, and the conclusion that risks of reoperation are comparable with those of initial aortocoronary bypass, but that long-term relief of angina is less favorable

SOURCE SIGNATURES OF FINE PARTICULATE MATTER FROM PETROLEUM REFINING AND FUEL USE

The molecular structure and microstructure of a suite of fine particulate matter (PM) samples produced by the combustion of residual fuel oil and diesel fuel were investigated by an array of analytical techniques. Some of the more important results are summarized below. Diesel PM (DPM): A small diesel engine test facility was used to generate a suite of diesel PM samples from different fuels under engine load and idle conditions. C XANES, {sup 13}C NMR, XRD, and TGA were in accord that the samples produced under engine load conditions contained more graphitic material than those produced under idle conditions, which contained a larger amount of unburned diesel fuel and lubricating oil. The difference was enhanced by the addition of 5% of oxygenated compounds to the reference fuel. Scanning transmission x-ray micro-spectroscopy (STXM) was able to distinguish particulate regions rich in C=C bonds from regions rich in C-H bonds with a resolution of {approx}50 nm. The former are representative of more graphitic regions and the latter of regions rich in unburned fuel and oil. The dominant microstructure observed by SEM and TEM consisted of complex chain-like structures of PM globules {approx}20-100 nm in mean diameter, with a high fractal dimension. High resolution TEM revealed that the graphitic part of the diesel soot consisted of onion-like structures made up of graphene layers. Typically 3-10 graphene layers make up the ''onion rings'', with the layer spacing decreasing as the number of layers increases. ROFA PM: Residual oil fly ash (ROFA) PM has been analyzed by a new approach that combines XAFS spectroscopy with selective leaching procedures. ROFA PM{sub 2.5} and PM{sub 2.5+} produced in combustion facilities at the U.S. EPA National Risk Management Research Laboratory (NRML) were analyzed by XAFS before and after leaching with water, acid (1N HCl), and pentane. Both water and acid leaching removed most of the metal sulfates, which were the dominant phase present for most metals (V, Ni, Zn, etc.). This allowed conclusive identification in the leaching residue of important secondary sulfide and oxide phases, including Ni sulfide, a toxic and carcinogenic phase observed in the leached PM{sub 2.5+} samples. Other significant secondary phases identified included V{sub 2}O{sub 4}, V sulfide, and NiFe{sub 2}O{sub 4}