Unconventional chiral particles have recently been predicted to appear in certain three dimensional (3D) crystal structures containing three-or more-fold linear band degeneracy points (BDPs). These BDPs carry topological charges, but are distinct from the standard twofold Weyl points or fourfold Dirac points, and cannot be described in terms of an emergent relativistic field theory. Here, we report on the experimental observation of a topological threefold BDP in a 3D phononic crystal. Using direct acoustic field mapping, we demonstrate the existence of the threefold BDP in the bulk

Berry phase associated with energy bands in crystals can lead to quantised observables like quantised dipole polarizations in one-dimensional topological insulators. Recent theories have generalised the concept of quantised dipoles to multipoles, resulting in the discovery of multipole topological insulators which exhibit a hierarchy of multipole topology: a quantised octupole moment in a three-dimensional bulk induces quantised quadrupole moments on its two-dimensional surfaces, which in turn induce quantised dipole moments on onedimensional hinges. Here, we report on the realisation of an octupole topological insulator in a three-dimensional acoustic metamaterial. We observe zero-dimensional topological corner states, one-dimensional gapped hinge states, two-dimensional gapped surface states, and three-dimensional gapped bulk states, representing the hierarchy of octupole, quadrupole and dipole moments. Conditions for forming a nontrivial octupole moment are demonstrated by comparisons with two different lattice configurations having trivial octupole moments. Our work establishes the multipole topology and its full hierarchy in three-dimensional geometries.

Topological acoustics has recently revolutionized fundamental concepts of acoustic propagation, giving rise to strikingly unique acoustic edge modes immune to backscattering. Despite the rapid progress in this field, simultaneous realization of reconfigurability, intelligentization, and automatic control over acoustic propagation paths is posing a great challenge. This challenge is overcome by proposing the concept of a programmable acoustic topological insulator based on two digital elements “0” or “1,” which consist of honeycomb‐lattice sonic crystals made of cylindrical rods with different diameters. The acoustic propagation paths in the topological insulators can be controlled automatically by programming different coding sequences, which arises from efficient transformation of pseudospin‐dependent edge modes on both interfaces of the digital elements. More importantly, a unique unit is experimentally fabricated that has either a “0” or “1” response automatically manipulated by an air cylinder, and design topological insulators with programmable functionality, to realize three digital acoustic devices, such as a single‐pole double‐throw switch, a single‐pole single‐throw switch, and a tunable logic gate. The proposed programmable topological insulators may enable future intelligent acoustic devices with exciting reconfigurable and programmable functionalities, which may lead to important advances in various applications, such as integrated acoustics, acoustic security, and information processing.

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The recently discovered non-Hermitian skin effect (NHSE) manifests the breakdown of current classification of topological phases in energy-nonconservative systems, and necessitates the introduction of non-Hermitian band topology. So far, all NHSE observations are based on one type of non-Hermitian band topology, in which the complex energy spectrum winds along a closed loop. As recently characterized along a synthetic dimension on a photonic platform, non-Hermitian band topology can exhibit almost arbitrary windings in momentum space, but their actual phenomena in real physical systems remain unclear. Here, we report the experimental realization of NHSE in a one-dimensional (1D) non-reciprocal acoustic crystal. With direct acoustic measurement, we demonstrate that a twisted winding, whose topology consists of two oppositely oriented loops in contact rather than a single loop, will dramatically change the NHSE, following previous predictions of unique features such as the bipolar localization and the Bloch point for a Bloch-wave-like extended state. This work reveals previously unnoticed features of NHSE, and provides the observation of physical phenomena originating from complex non-Hermitian winding topology.

BackgroundMany factors may lead to sperm DNA damage. However, it is little known that the correlations of sperm DNA damage with obesity-associated markers, and reproductive hormones and lipids levels in serum and seminal plasma.MethodsIn our prospective study, a total of 1 010 subfertile men, aged from 18 to 50 years old, were enrolled from August 2012 through June 2015. Their obesity-associated markers, semen parameters, sperm acrosomal enzyme activity, seminal plasma biochemical markers, and reproductive hormones and lipids levels in serum and seminal plasma were detected. Sperm DNA fragmentation index (DFI) was determined by sperm chromatin structure assay. The correlations between DFI and each of the above-mentioned variables were analyzed.ResultsSpearman correlation analysis showed that sperm DFI was positively related to age and abstinence time (P<0.001). Sperm DFI was also positively related to semen volume and percent of abnormal sperm head (P<0.001), while negatively related to sperm concentration, progressive motility (PR), sperm motility, total normal-progressively motile sperm count (TNPMS), percent of normal sperm morphology (NSM), percent of intact acrosome and acrosomal enzyme activity (P<0.001). Sperm DFI was positively related to seminal plasma zinc level (P<0.001) but unrelated to seminal plasma total α-glucotase, γ-glutamyl transpeptidase (GGT) and fructose levels. There was no any correlation between sperm DFI and obesity-associated markers such as body mass index (BMI), waist-to-hip ratio (WHR), waist circumference (WC) and waist-to-height ratio (WHtR), and serum lipids levels, but there was positive correlation between sperm DFI and seminal plasma triglyceride (TG) and total cholesterol (TC) levels (P<0.001). Sperm DFI was positively related to serum luteinizing hormone (LH) and follicle stimulating hormone (FSH) levels and seminal plasma FSH and estradiol (E2) levels (P<0.001), but unrelated to serum and seminal plasma testosterone (T) levels. The multivariate regression analysis for the variables which were significantly correlated with sperm DFI in Spearman correlation analysis showed that age, semen volume, sperm concentration, progressive motility, TNPMS and intact acrosome were independently correlated with sperm DFI.ConclusionsThere are many potential factors associated with sperm DFI, including age, abstinence time, spermatogenesis and maturation, seminal plasma lipids and reproductive hormones levels. However, the potential effects of seminal plasma lipids and reproductive hormones on sperm DNA damage need still to be demonstrated by the studies with scientific design and a large size of samples.Electronic supplementary materialThe online version of this article (10.1186/s12958-018-0345-y) contains supplementary material, which is available to authorized users.

Three-dimensional (3D) gapless topological phases can be classified by the dimensionality of the band degeneracies, including zero-dimensional (0D) nodal points, one-dimensional (1D) nodal lines, and two-dimensional (2D) nodal surfaces. Both nodal points and nodal lines have been realized recently in photonics and acoustics. However, a nodal surface has never been observed in any classical-wave system. Here, we report on the experimental observation of a twofold symmetry-enforced nodal surface in a 3D chiral acoustic crystal. In particular, the demonstrated nodal surface carries a topological charge of 2, constituting the first realization of a higher-dimensional topologically-charged band degeneracy. Using direct acoustic field measurements, we observe the projected nodal surface and its Fermi-arc-like surface states and demonstrate topologically-induced robustness of the surface states against disorders. This discovery of a higher-dimensional topologically-charged band degeneracy paves the way toward further explorations of the physics and applications of new topological semimetal phases.

There were controversial results between obesity-associated markers and semen quality. In this study, we investigated the correlations between age, obesity-associated markers including body mass index (BMI), waist-to-hip ratio (WHR), waist-to-height ratio (WHtR) and waist circumference (WC), the combination of age and obesity-associated markers, semen parameters and serum reproductive hormone levels in 1231 subfertile men. The results showed that BMI, WC, WHR and WHtR were positively related to age, and there were also positive relations between BMI, WHR, WC and WHtR and between sperm concentration (SC), total sperm count (TSC), progressive motility (PR), sperm motility and per cent of normal sperm morphology (NSM). However, age, each of obesity-associated markers and the combination of obesity-associated markers and age were unrelated to any of semen parameters including total normal-progressively motile sperm count (TNPMS). Age, BMI, WHR, WC and WHtR were negatively related to serum testosterone and SHBG levels. However, only serum LH and FSH levels were negatively related to sperm concentration, NSM and sperm motility. In a conclusion, although age and obesity have significant impacts on reproductive hormones such as testosterone, SHBG and oestradiol, semen parameters related to FSH and LH could not be influenced, indicating that obesity-associated markers could not predict male semen quality.