In the framework of the Cartan classification of Hamiltonians, a kind of topological classification of Fermi surfaces is established in terms of topological charges. The topological charge of a Fermi ...surface depends on its codimension and the class to which its Hamiltonian belongs. It is revealed that six types of topological charges exist, and they form two groups with respect to the chiral symmetry, with each group consisting of one original charge and two descendants. It is these nontrivial topological charges which lead to the robust topological protection of the corresponding Fermi surfaces against perturbations that preserve discrete symmetries.
•Crack initiation stress (σci) and crack damage stress (σcd) of the Beishan granite under uniaxial and triaxial compressions are determined.•3D distributions of AE events in the rock samples at ...different loading stages in the compression tests are obtained.•Methods of indentifying σci and σcd at different confinements are discussed.•Confinement-dependent damage stress characteristics are analyzed.
During the Upper Paleolithic, lions become an important theme in Paleolithic art and are more frequent in anthropogenic faunal assemblages. However, the relationship between hominins and lions in ...earlier periods is poorly known and primarily interpreted as interspecies competition. Here we present new evidence for Neanderthal-cave lion interactions during the Middle Paleolithic. We report new evidence of hunting lesions on the 48,000 old cave lion skeleton found at Siegsdorf (Germany) that attest to the earliest direct instance of a large predator kill in human history. A comparative analysis of a partial puncture to a rib suggests that the fatal stab was delivered with a wooden thrusting spear. We also present the discovery of distal lion phalanges at least 190,000 old from Einhornhöhle (Germany), representing the earliest example of the use of cave lion skin by Neanderthals in Central Europe. Our study provides novel evidence on a new dimension of Neanderthal behavioral complexity.
A peculiar feature of quantum states is that they may embody so-called projective representations of symmetries rather than ordinary representations. Projective representations of space groups-the ...defining symmetry of crystals-remain largely unexplored. Despite recent advances in artificial crystals, whose intrinsic gauge structures necessarily require a projective description, a unified theory is yet to be established. Here, we establish such a unified theory by exhaustively classifying and representing all 458 projective symmetry algebras of time-reversal-invariant crystals from 17 wallpaper groups in two dimensions-189 of which are algebraically non-equivalent. We discover three physical signatures resulting from projective symmetry algebras, including the shift of high-symmetry momenta, an enforced nontrivial Zak phase, and a spinless eight-fold nodal point. Our work offers a theoretical foundation for the field of artificial crystals and opens the door to a wealth of topological states and phenomena beyond the existing paradigms.
Sodium-ion batteries are promising alternative electrochemical energy storage devices due to the abundance of sodium resources. One of the challenges currently hindering the development of the ...sodium-ion battery technology is the lack of electrode materials suitable for reversibly storing/releasing sodium ions for a sufficiently long lifetime. Redox-active polymers provide opportunities for developing advanced electrode materials for sodium-ion batteries because of their structural diversity and flexibility, surface functionalities and tenability, and low cost. This review provides a short yet concise summary of recent developments in polymer electrode materials for sodium-ion batteries. Challenges facing polymer electrode materials for sodium-ion batteries are identified and analyzed. Strategies for improving polymer electrochemical performance are discussed. Future research perspectives in this important field are projected.
Genetic evidence for anatomically modern humans (AMH) out of Africa before 75 thousand years ago (ka) and in island southeast Asia (ISEA) before 60 ka (93-61 ka) predates accepted archaeological ...records of occupation in the region. Claims that AMH arrived in ISEA before 60 ka (ref. 4) have been supported only by equivocal or non-skeletal evidence. AMH evidence from this period is rare and lacks robust chronologies owing to a lack of direct dating applications, poor preservation and/or excavation strategies and questionable taxonomic identifications. Lida Ajer is a Sumatran Pleistocene cave with a rich rainforest fauna associated with fossil human teeth. The importance of the site is unclear owing to unsupported taxonomic identification of these fossils and uncertainties regarding the age of the deposit, therefore it is rarely considered in models of human dispersal. Here we reinvestigate Lida Ajer to identify the teeth confidently and establish a robust chronology using an integrated dating approach. Using enamel-dentine junction morphology, enamel thickness and comparative morphology, we show that the teeth are unequivocally AMH. Luminescence and uranium-series techniques applied to bone-bearing sediments and speleothems, and coupled uranium-series and electron spin resonance dating of mammalian teeth, place modern humans in Sumatra between 73 and 63 ka. This age is consistent with biostratigraphic estimations, palaeoclimate and sea-level reconstructions, and genetic evidence for a pre-60 ka arrival of AMH into ISEA. Lida Ajer represents, to our knowledge, the earliest evidence of rainforest occupation by AMH, and underscores the importance of reassessing the timing and environmental context of the dispersal of modern humans out of Africa.
Dear Editor,
Transcription factors （TFs） are proteins that regulate the expression of target genes by binding to specific cis-elements in pro-moter regions. Transcriptional regulators （TRs） a）so ...regulate the expression of target genes; however, they operate indirectly via interaction with the basal transcription apparatus （e.g., TFs）, or by altering the accessibility of DNA to TFs via chromatin remodeling. Another type of regulatory proteins, protein kinases （PKs）,
We demonstrate a general approach to the preparation of layered graphene oxide structures with sandwiched conducting polymers of different morphologies. The approach is conceptualized on the basis of ...the electrostatic interactions between negatively charged graphene oxide sheets and positively charged surfactant micelles. A graphene oxide−polypyrrole composite prepared from this approach exhibited an excellent electrocapacitive performance with a high specific capacitance over 500 F g−1. Good rate performance and cycle ability were realized by the composite electrode. The simple method described here opens up a generalized route to making a wide range of graphene oxide-based and graphene-based composite materials for applications beyond electrochemical energy storage.
Topological fermions as excitations from multidegenerate Fermi points have been attracting increasing interest in condensed matter physics. They are characterized by topological charges, and magnetic ...fields are usually applied in experiments for their detection. Here we present an index theorem that reveals the intrinsic connection between the topological charge of a Fermi point and the in-gap modes in the Landau band structure. The proof is based on mapping fermions under magnetic fields to a topological insulator whose topological number is exactly the topological charge of the Fermi point. Our Letter lays a solid foundation for the study of intriguing magnetoresponse effects of topological fermions.
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