119 research outputs found
A Newly Discovered Late Pleistocene Lower Third Premolar and the High Frequency Occurrence of Tomes’ Root in the Human Fossil Record from China
No full textDental remains provide crucial evidence for interpreting a populations’ affinity as well as human evolution. Recent studies of fossil human teeth have enriched our current view of morphological variation during the Pleistocene in East Asia. In the present paper, we describe a newly discovered late Pleistocene human tooth, a lower third premolar from the Weijiadong cave in Bijie in south-western China, which is dated around 18-20Ka BP using AMS Carbon 14 dating. The tooth is identified as belonging to an early modern human based on its morphology and size. The Tomes’ root is present in this lower third premolar, one of the non-metrical dental traits developed genetically. Moreover, we examine most of the fossil lower third premolars collected from China, as well as material from several Neolithic and historical human assemblages. We find that the Tomes’ root is very common in Chinese human fossils and occurs in high frequency in Neolithic and historic human remains from China. We suggest the high frequency of Tomes’ root may serve as a non-metric dental trait to support inferences regarding regional continuity of human evolution in East Asia
The size modulation of hollow mesoporous carbon spheres synthesized by a simplified hard template route
No full textIdentification and Antioxidant Capacity of Free and Bound Phenolics in Six Varieties of Mulberry Seeds Using UPLC-ESI-QTOF-MS/MS
No full textMulberry seeds are a byproduct of juice processing and may be an important resource for its abundant compounds. In this study, we analyzed the qualitative composition of free and bound phenolics from six varieties of mulberry seeds using UPLC-ESI-QTOF-MS/MS. Free phenolics (FPs) and bound phenolics (BPs) were measured using the Folin–Ciocalteu method; antioxidant capacity was determined by measuring 2,2-diphenyl-1-picrylhydrazyl radical-scavenging activity, using the ferric reducing antioxidant power assay. A total of 28 free and 11 bound phenolics were extracted and identified, wherein five free phenolics were found in mulberry matrices for the first time. The six varieties of mulberry seeds exhibited higher content of FPs than BPs, and there was a correlation between the phenolic content and antioxidant capacity. Consequently, three varieties were selected for their high phenolic content and antioxidant capacity. This study might offer a theoretical basis for the utilization of mulberry seed
Effects of cooling rate on the mechanical properties and precipitation behavior of carbides in H13 steel during quenching process
No full textThe effects of cooling rate (CR) on the mechanical properties and precipitation behavior of carbides in H13 steel during quenching process were investigated. The retained austenite tends to be more unstable with increasing CRs, while the martensite increases gradually, based on XRD analyses and EBSD results. The values of hardness are increased, and the elongation along with impact energy is decreased, respectively, at higher CRs. Tensile strength remains above 2.0 GPa. Work hardening rates increase considerably in three samples, suggesting that transformation-induced plasticity effect may take place during the tensile test. Moreover, an increase in yield strength is observed when CR exceeds 15 K s ^−1 , possibly due to a high volume fraction of martensite, decline in average grain size and precipitation of fine carbides. Types of the precipitates acquired were identified by electrolysis and XRD analyses. The results indicate the predominant existence of MC, M _6 C and M _7 C _3 , which are confirmed by SEM-EDS analyses and FactSage thermodynamic calculations. The size, volume and distribution of the carbides were also scrutinized under SEM. It is found that the volume fraction and size of the precipitates both decrease with increasing CRs. Based on these experimental data, an optimum CR for the quenching process could be determined to achieve the desired distribution of carbides, which in turn leads to the enhanced mechanical behaviors
Interannual Variation of Vegetation NDVI and Its Temporal and Spatial Response to Temperature and Precipitation in Qilian Mountains
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Sensitivity analysis of thermal factors affecting the nonlinear freezing process of soil
No full textIn the construction of artificial freezing methods and cold region engineering, the determination of the accurate temperature field is the demand of both ensuring the stability of frozen soil and reducing the project investment. Affected by the external environment, phase change latent heat, non-linear thermal parameters, etc., the temperature evolution of the soil freezing process is a non-linear form, and the temperature field evolution will be more complex with the change of different influencing factors. Scientific control and utilization of the influencing factors of the frozen soil temperature field play a vital role in improving the freezing efficiency and accuracy of the soil temperature field. This study aims to analyze the sensitivity of thermal factors on the nonlinear formation process of frozen soil temperature field, and to provide the results for the control of various factors in frozen soil engineering. A freezing model test was designed and implemented, the boundary conditions and temperature evolution in the model were monitored. Meanwhile, the thermal parameters and unfrozen water content of the model soil were tested indoor. Then the theoretical relationship between unfrozen water content and parameters was deduced to determine the variation range of unfrozen water content. The boundary condition values (including the maximum, minimum and average values) and thermal parameters were used in the orthogonal simulation of the freezing model, respectively. The temperature simulation values were compared with the model test values, and the factors affecting the nonlinear heat transfer of frozen soils were analyzed quantitatively by both the range method and variance analysis method. Several suggestions of the vital factors in the soil freezing construction were offered based on this research
ChemInform Abstract: Synthesis of Amides by Palladium‐Catalyzed Decarbonylative Coupling of Carboxylic Acids with Isocyanides.
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