Search

The influences of freezing pretreatment, thermal pretreatments (water blanching and steam blanching) and their combinations on hot-air drying kinetics of Vaccinium bracteatum Thunb (VBT) leaves at 60°C and key quality attributes were investigated. Generally, all the applied pretreatments accelerated VBT leaf drying process. The sequential freezing (8 h) and water blanching (1 min) pretreatments shortened the drying time by 65.5%. The diffusion modeling results revealed that all the pretreatments intensified water diffusion and external water exchange with hot air during drying. Freezing pretreatments had no preservative effect on phenolics, iridoids, and antioxidant capacity of VBT leaves after dehydration, whereas both thermal pretreatments significantly improved dried VBT leaf quality in these three aspects. On the contrary, thermal pretreatments had destructive effects on activities of polyphenol oxidase and β-glucosidase. Due to the low β-glucosidase activity in dried VBT leaves with thermal pretreatments that participated in the transformation of iridoids to generate dark colorants eventually, the extracts from dried VBT leaves with only thermal pretreatments had weak ability to dye glutinous rice. However, this problem was fixed once extra β-glucosidase was added before rice cooking. Overall, the obtained results can provide guidance for the preservation and drying of VBT leaves that has been poorly studied. [ABSTRACT FROM AUTHOR]

Sand dunes and sand sheets are located along the south side of Kankakee River Valley in Illinois and Indiana, which overlie glaciofluvial outwash, lake sediments, and bedrock of Middle Paleozoic shales and carbonates. Dunes are prominent feature of the landscape, and most dunes are 15 to 25 feet ( ~4-7m) high, and some reach 50 feet (15m). Due to the lack of natural exposure and roadcuts, three dunes were sampled by hand augering for OSL (optically stimulated luminescence) dating. Ground penetrating radar (GPR) surveys were conducted for a better understanding of the stratigraphy where exposures are not available. Results show that all three sites contain ages within the Younger Dryas chronozone (11.5-12.8 ka). More importantly, we found that at site 1 there are about 8 meters of eolian sand yielded 5 ages within the Younger Dryas. Although the large error bar of singular individual OSL age (about 6-9%, about 0.8-1.2 ka) usually does not allow for the determination of a specific climatic event, multiple ages from multiple sites of these dunes and striking thickness in this study all fall into the range of Younger Dryas chronozone. Thus, we believe that the rapid climatic changes before, during and after Younger Dryas play key roles in the dune construction here in the Kankakee River Valley. These changes of the ages are consistent with GPR image and lithology changes observed in the field [ABSTRACT FROM AUTHOR]

River aggradation or incision at different spatial-temporal scales are governed by tectonics, climate change and surface processes which all adjust the ratio of sediment load to transport capacity of a channel. But how the river responds to differential tectonic and extreme climate events in a catchment is still poorly understood. Here, we address this issue by reconstructing the distribution, ages and sedimentary process of fluvial terraces in a tectonically active area and monsoonal environment in the headwaters of the Yangtze River in the eastern Tibet Plateau. Field observations, topographic analyses and optically stimulated luminescence (OSL) dating reveal a remarkable fluvial aggradation, followed by terraces formations at elevations of 62-55 m (T7), 42-46 m (T6), 38 m (T5), 22-36 m (T4), 18 m (T3), 11 m (T2), 2-6 m (T1) above the present floodplain. Gravelly fluvial accumulation more than 62 m thick has been dated prior to 24-19 ka. It is regarded as a response to cold climate during the Last Glacial Maximum. Subsequently, the strong monsoon precipitation contributed to cycles of rapid incision and lateral erosion, expressed as cut-in-fill terraces. The correlation of terraces suggests that specific tectonic activity controls the spatial scale and geomorphic characteristics of the terraces, while climate fluctuations determine the valley filling, river incision and terrace formation. Debris and colluvial sediments are frequently interbedded in fluvial sediment sequences, illustrating the episodic short-time blocking of the channel around 20 ka. This indicates the potential impact of extreme events on the geomorphic evolution in the rugged terrain. [ABSTRACT FROM AUTHOR]