Explanations of the tertiary global cooling trend

A series of General Circulation Model experiments are performed to examine the role of paleogeography as an explanation of the Tertiary global cooling trend. Systematic long-term variations in topography and land—sea distribution are potential causes of long-term climate change. However, climate model sensitivity experiments indicate a geographically related cooling during the last 20 million years, but not a long-term Cenozoic trend. Coarse resolution changes in geography throughout the Tertiary may not be the explanation of the Tertiary global cooling trend. Either a series of events, some geographically related, or another forcing factor, most probably atmospheric CO₂ concentration, are offered as alternative explanations of the Tertiary global cooling trend.     

Estimation of Wheat Grain Tissue Cohesion via Laser Induced Breakdown Spectroscopy

During the wheat milling process, the bran fractionation is related to its mechanical properties, which are measured using tensile tests on hand-isolated tissues. However, the dissection of wheat tissues implies a soaking stage in water that can modify tissue properties. New methodologies are required to evaluate wheat tissue properties directly on native grains. The aim of this work was to estimate wheat grain tissue cohesion by the ionization effectiveness via laser-induced breakdown spectroscopy (LIBS) technique. Isolated bran tissues and wheat grains were submitted to LIBS analysis using a pulsed argon fluoride (193 nm, 15 ns, 1 Hz, 2 J cm⁻²) excimer laser and a compact optic fiber spectrometer (HR2000). The first approach was to correlate the ratios of ionic to atomic emission lines (MgII/MgI and CaII/CaI) of isolated tissues to their mechanical measurements. The energy needed to rupture the tissue was correlated to MgII/MgI (R ² = 0.72). Secondly, native grains were irradiated and chemometrics was applied to discriminate tissue spectra. The aleurone layer isolated after the soaking step presented a higher MgII/MgI than the aleurone layer from native grains, indicating a possible water effect on the tissue cohesion. In conclusion, the LIBS technique may be a potential method for rapid structural analysis of vegetal material allowing wheat population screening of both compositional and mechanical properties.