Northern China harbored the world's earliest complex societies based on millet farming, in two major centers in the Yellow (YR) and West Liao (WLR) River basins. Until now, their genetic histories have remained largely unknown. Here we present 55 ancient genomes dating to 7500-1700 BP from the YR, WLR, and Amur River (AR) regions. Contrary to the genetic stability in the AR, the YR and WLR genetic profiles substantially changed over time. The YR populations show a monotonic increase over time in their genetic affinity with present-day southern Chinese and Southeast Asians. In the WLR, intensification of farming in the Late Neolithic is correlated with increased YR affinity while the inclusion of a pastoral economy in the Bronze Age was correlated with increased AR affinity. Our results suggest a link between changes in subsistence strategy and human migration, and fuel the debate about archaeolinguistic signatures of past human migration.

Unlike polyolefins (e.g., isotactic polypropylene), it is still a great challenge to form rich shish-kebabs in biodegradable poly(L-lactic acid) (PLLA) because of its short chain length and semirigid chain backbone. In the present work, a modified injection molding technology, named oscillation shear injection molding, was applied to provide an intense shear flow on PLLA melt in mold cavity, in order to promote shear-induced crystallization of PLLA. Additionally, a small amount of poly(ethylene glycol) (PEG) with flexible chains was introduced for improving the crystallization kinetics. Numerous shish-kebabs of PLLA were achieved in injection-molded PLLA for the first time. High-resolution scanning electronic microscopy and small-angle X-ray scattering showed a structure feature of shish-kebabs with a diameter of around 0.7 μm and a long period of ~20 nm. The wide-angle X-ray diffraction results showed that shish-kebabs had more ordered crystalline structure of α-form. A significant improvement of the mechanical properties was obtained; the tensile strength and modulus increased to 73.7 and 1888 MPa from the initial values of 64.9 and 1684 MPa, respectively, meanwhile the ductility is not deteriorated. Interestingly, when shish-kebabs form in the PLLA/PEG system, a bamboo-like bionic structure comprising a hard skin layer and a soft core develops in injection-molded specimen. This unique structure leads to a great balance of mechanical properties, including substantial increments of 26, 20, and 112% in the tensile strength, modulus, and impact toughness, compared to the control sample. Further exploration will give a rich fundamental understanding in the shear-induced crystallization and morphology manipulation of PLLA, aiming to achieve superior PLLA products.

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Polystyrene (PS) and poly(methyl methacrylate) (PMMA) blends filled with octadecylamine-functionalized graphene (GE-ODA) have been fabricated to obtain conductive composites with a lower electrical percolation threshold according to the concept of double percolation. The dependence of the electrical properties of the composites on the morphology is examined by changing the proportion of PS and PMMA. Our results reveal that the electrical conductivity of the composites can be optimal when PS and PMMA phases form a cocontinuous structure and GE-ODA nanosheets are selectively located and percolated in the PS phase. For the PS/PMMA blend (50w/50w), the composites exhibit an extremely low electrical percolation threshold (0.5 wt %) because of the formation of a perfect double percolated structure. Moreover, the rheological properties of the composites are also measured to gain a fundamental understanding of the relationship between microstructure and electrical properties.

In this study, the kinetics of vesicle formation of ABA amphiphilic triblock copolymers from an initially homogeneous state was theoretically and experimentally investigated by adding a selective solvent into the system. The pathway of spontaneous vesicle formation depended greatly on the selective solvent addition rate. At a slow addition rate, the pathway followed three stages: (1) the amphiphilic triblock copolymer combined into a large irregular aggregation; (2) the large irregular aggregation broke into big irregular spheres; and (3) some hydrophilic molecules in the big irregular spheres diffused toward the surface, and some hydrophilic molecules diffused toward the center, forming vesicles. However, at a fast addition rate, the pathway was as follows: (1) the amphiphilic triblock copolymer aggregated into many small spheres; (2) the small spheres merged to form rod-like micelles first and then oblate membranes; and (3) the oblate membranes closed up to form vesicles. This pathway difference for vesicle formation can be attributed to the existence of many metastable states in the system. This finding not only provides new insight into the origins of vesicles but also provides further understanding on the self-assembly kinetics of amphiphilic block copolymers in a selective solvent.

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We have investigated the effect of shear flow on the formation of ring-shaped ABA triblock copolymer (P4VP 43 -b-PS 260 -b-P4VP 43 ) micelles. The results reveal that shear flow plays an important role in the formation of the rings. Both ring size and its distribution are found to be dependent sensitively on the stirring rate. Sizable rings are more likely to be formed at moderate stirring rate. Interestingly, the ring formation mechanism is also dependent on the shear flow. Copolymers are likely to form rings via end-to-end cylinder connection at low stirring rates, whereas they tend to form rings via the pathway of the rod-sphere-vesicle-ring at high stirring rates.

We report the self-assembly of a linear ABC triblock copolymer into the previously unknown architecture of giant segmented wormlike micelles (SWMs). The lengths and diameters of these giant SWMs were as high as ca. 10 µm and 500 nm, respectively. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) analysis revealed that the SWMs comprised sequences of repeated elemental parts, i.e., disks having a thickness of ca. 65 nm. A most interesting feature is that disks having different diameters became connected through threads to form various giant segmented wormlike micelles. A kinetic study indicated that the process of SWM formation occurred basically through three stages: (1) the ABC triblock copolymer self-assembled into small spheres of ca. 38 nm diameter; (2) these small spheres joined together to form intermediate shuttlelike structures;(3) the spheres within the shuttlelike structures rearranged and underwent further adjustment to form the final SWMs.