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Particle-matrix interfaces can play an important role in heat propagation through particulate composites. We investigated the possibility of using frequency domain thermoreflectance combined with a numerical thermal model to measure in situ the thermal resistance of the particle-matrix interface in particulate composite materials. We found that the sensitivity of the technique depended on the matrix thermal conductivity, the particle size, and the value of the interface thermal resistance. In general, high thermal conductivity matrix materials and small particles will present higher sensitivity to the interface thermal resistance. We tested the technique with diamond particles embedded in tin and showed that the interface thermal resistance could be measured for these samples. [ABSTRACT FROM AUTHOR]

The fluxes of total mass, organic carbon, biogenic opal, calcite and long-chain alkenones were measured at three water depths in the Cariaco Basin over three separate annual upwelling cycles (1996-99) as a part of the CARIACO time series. The study focused on the collection and analyses of undisturbed surface sediments from the Cariaco basin.

Analyses of more than 60 sediment samples from the Amazon deep sea fan show remarkably constant terrigenous biomarkers (lignin phenols and cutin acids) and stable carbon isotopic compositions of organic matter ([[delta].sup.13][C.sub.OM]) deposited from 10 to 70 ka. Sediments from the nine Amazon deep sea fan channel-levee systems investigated in this study yielded relatively narrow ranges for diagnostic parameters such as organic carbon (OC) normalized total lignin yields ([LAMBDA] = 3.1 [+ or -] 1.1 mg/100 mg OC), syringyl:vanillyl phenol ratios (S/V = 0.84 [+ or -] 0.06), cinnamyl:vanillyl phenol ratios (C/V = 0.08 [+ or -] 0.02), isomeric abundances of cutin-derived dihydroxyhexadecanoic acid ([f.sub.10,16-OH] = 0.65 [+ or -] 0.02), and [[delta].sup.13][C.sub.OM] (-27.6% [+ or -] 0.6 [per thousand]). Our measurements support the hypothesis that the vegetation of the Amazon Basin did not change significantly during the late Pleistocene, even during the Last Glacial Maximum. Moreover, the compositions obtained from the Amazon deep sea fan are similar to those of modern Amazon River suspended sediments. Such results strongly indicate that the current tropical rainforest vegetation has been a permanent and dominant feature of the Amazon River watershed over the past 70 k.y. Specifically, we found no evidence for the development of large savannas that had been previously postulated as indicators of increased glacial aridity in Amazonia. Climate models need to be modified to account for the uninterrupted input of moisture to the tropical Amazon region over the late Pleistocene-Holocene period. Keywords: Amazon deep sea fan, Amazon Basin, lignin, cutin acids, [sup.13]C, paleoclimate, late Pleistocene.

A novel approach for the analysis of lignin in geochemical samples has been developed as an alternative to the alkaline CuO oxidation procedure first developed in 1982. The new procedure utilizes microwave digestion technology, as opposed to conductive heating, to carry out oxidative hydrolysis of six samples in an oxygen-free atmosphere at 150 degrees C for 90 min. Ethyl acetate is used as the extraction solvent in place of diethyl ether. Additionally, the new method incorporates a simplified extraction procedure that minimizes solvent handling and the mount of glassware needed. Under these novel conditions, the yields and compositions of lignin phenols from four different samples (modem and ancient sediments; woody and nonwoody tissues) match those obtained by the 'traditional' procedure. The significant advantages of this new alkaline CuO oxidation method include faster reaction times, the ability to accurately measure and control reaction conditions, added flexibility for the analyst, and a marked increase in the achievable sample throughput.

A study of terrigenous organic matter in offshore surface sediments in the Gulf of Mexico revealed that offshore sediments originate from grassland soils in the Mississippi River drainage basin and that nearshore sediments derive from coastal forests and swamps. The study examined the chemical and stable isotope signatures of oxidation from lignins in the organic matter. It enabled researchers to differentiate between matter which originated from plants which use the C4 mechanism in photosynthesis and those which use the C3 mechanism. These results significantly expand knowledge of the nature and fraction of terrigenous organic carbon in marine sediments.