Hyperbolic Cooper-Pair Polaritons in Planar Graphene/Cuprate Plasmonic Cavities.

Hyperbolic Cooper-pair polaritons (HCP) in cuprate superconductors are of fundamental interest due to their potential for providing insights into the nature of unconventional superconductivity. Here, we critically assess an experimental approach using near-field imaging to probe HCP in Bi2Sr2CaCu2O8+x (Bi-2212) in the presence of graphene surface plasmon polaritons (SPP). Our simulations show that inherently weak HCP features in the near-field can be strongly enhanced when coupled to graphene SPP in layered graphene/hexagonal boron nitride (hBN)/Bi-2212 heterostructures. This enhancement arises from our multilayered structures effectively acting as plasmonic cavities capable of altering collective modes of a layered superconductor by modifying its electromagnetic environment. The degree of enhancement can be selectively controlled by tuning the insulating spacer thickness with atomic precision. Finally, we verify the expected renormalization of room-temperature graphene SPP using near-field infrared imaging. Our modeling, augmented with data, attests to the validity of our approach for probing HCP modes in cuprate superconductors.

Charge-Transfer Plasmon Polaritons at Graphene/α-RuCl3 Interfaces.

Nanoscale charge control is a key enabling technology in plasmonics, electronic band structure engineering, and the topology of two-dimensional materials. By exploiting the large electron affinity of α-RuCl3, we are able to visualize and quantify massive charge transfer at graphene/α-RuCl3 interfaces through generation of charge-transfer plasmon polaritons (CPPs). We performed nanoimaging experiments on graphene/α-RuCl3 at both ambient and cryogenic temperatures and discovered robust plasmonic features in otherwise ungated and undoped structures. The CPP wavelength evaluated through several distinct imaging modalities offers a high-fidelity measure of the Fermi energy of the graphene layer: EF = 0.6 eV (n = 2.7 × 1013 cm-2). Our first-principles calculations link the plasmonic response to the work function difference between graphene and α-RuCl3 giving rise to CPPs. Our results provide a novel general strategy for generating nanometer-scale plasmonic interfaces without resorting to external contacts or chemical doping.

In situ measurement of cesium-137 contamination in fruits from the northern Marshall Islands.

Radioactive contamination of fruits in the northern Marshall Islands, resulting from the US nuclear weapons testing program in the 1940s and 1950s, is still a human health concern, in particular pertaining to island population resettlement and the economic benefit from farming. Over 200 fruits, primarily coconuts and pandanus, were collected on 11 islands from four atolls in the northern Marshall Islands in 2017. The energy spectra from nuclear gamma decays were measured on a research vessel for each fruit in situ. From these recordings, the level of cesium-137 (137Cs) contamination was determined for individual fruits. Comparisons of the results are made to past studies and international food safety standards. There is a broad distribution of values, ranging from below detectable radiation levels to relatively high levels; safety concerns are largest for Bikini Island. A noticeable fraction of fruits from Bikini have significantly higher levels of 137Cs contamination compared with those from all other measured islands.

A density cusp of quiescent X-ray binaries in the central parsec of the Galaxy.

The existence of a 'density cusp'-a localized increase in number-of stellar-mass black holes near a supermassive black hole is a fundamental prediction of galactic stellar dynamics. The best place to detect such a cusp is in the Galactic Centre, where the nearest supermassive black hole, Sagittarius A*, resides. As many as 20,000 black holes are predicted to settle into the central parsec of the Galaxy as a result of dynamical friction; however, so far no density cusp of black holes has been detected. Low-mass X-ray binary systems that contain a stellar-mass black hole are natural tracers of isolated black holes. Here we report observations of a dozen quiescent X-ray binaries in a density cusp within one parsec of Sagittarius A*. The lower-energy emission spectra that we observed in these binaries is distinct from the higher-energy spectra associated with the population of accreting white dwarfs that dominates the central eight parsecs of the Galaxy. The properties of these X-ray binaries, in particular their spatial distribution and luminosity function, suggest the existence of hundreds of binary systems in the central parsec of the Galaxy and many more isolated black holes. We cannot rule out a contribution to the observed emission from a population (of up to about one-half the number of X-ray binaries) of rotationally powered, millisecond pulsars. The spatial distribution of the binary systems is a relic of their formation history, either in the stellar disk around Sagittarius A* (ref. 7) or through in-fall from globular clusters, and constrains the number density of sources in the modelling of gravitational waves from massive stellar remnants, such as neutron stars and black holes.

Expiratory muscle training in spinal cord injury: a randomized controlled trial.

OBJECTIVE: To assess the effectiveness of expiratory muscle training on the pulmonary function of spinal cord injured patients. DESIGN: Randomized controlled trial. SETTING: Acute inpatient rehabilitation hospital. PARTICIPANTS: Patients (N=29, 22 men and 7 women) with recent traumatic, motor complete, spinal cord injury (SCI) at or above level T1 consecutively admitted to an SCI rehabilitation service. Subjects were randomized to either resistance training (n=16) or sham training (n=13). INTERVENTIONS: The subjects completed either sham training or expiratory muscle resistive training with maximal expiratory force using a small handheld device, which is a tube with an aperture at the distal end, for 10 repetitions twice a day 5 days a week for a total of 6 weeks. MAIN OUTCOME MEASURES: Pulmonary function tests were measured before and after the training program and included forced vital capacity (FVC); forced expiratory volume in 1 second (FEV1); maximum expiratory pressure (MEP), which is often referred to as forced expiratory pressure; maximum inspiratory pressure (MIP), which is often referred to as negative inspiratory force; inspiratory capacity (IC); expiratory reserve volume (ERV); total lung capacity (TLC); functional residual capacity (FRC); and residual volume (RV). RESULTS: FVC, FEV1, and ERV improved in both groups. Although exit values of MEP were improved in both groups compared with entry values, this increase was statistically significant only in the resistance training group. No significant improvements occurred in IC, TLC, FRC, or RV from entry to exit. MIP improved in both groups, but this increase was statistically significant only in the resistance training group. There was also a significant between-group difference in MEP exit values (98cmH(2)O for the resistance training group and 59cmH(2)O for the sham training group, t=3.45, P=.002). Multivariate analyses failed to reveal significant effects of treatment for any of the pulmonary function tests. CONCLUSIONS: The resistance training group had significantly greater exit MEP values than the sham training group in univariate analysis only. However, improvements in pulmonary function were noted in both the resistance training and sham training groups. Although multivariate analysis failed to reveal a significant difference between groups, these findings offer some indication that expiratory training may benefit people with SCI.

Emotion expression among abusive mothers is associated with their children's emotion processing and problem behaviours.

The current study evaluated the quality of facial and vocal emotional expressions in abusive and non-abusive mothers, and assessed whether mothers' emotional expression quality was related to their children's cognitive processing of emotion and behavioural problems. Relative to non-abusive mothers, abusive mothers produced less prototypical angry facial expressions, and less prototypical angry, happy, and sad vocal expressions. The intensity of mothers' facial and vocal expressions of anger was related to their children's externalising and internalising symptoms. Additionally, children's cognitive processing of their mothers' angry faces was related to the quality of mothers' facial expressions. Results are discussed with respect to the impact of early emotional learning environments on children's socioemotional development and risk for psychopathology.

Listeners judge talker sex more efficiently from male than from female vowels.

Speech routinely provides cues as to the sex of the talker, in voiced sounds, these cues mainly reflect dimorphism in vocal anatomy. This dimorphism is not symmetrical, however, since during adolescent development, males specifically diverge from a previously shared trajectory with females. We therefore predicted that listeners would show a corresponding perceptual advantage for male sounds in talker-sex discrimination, a hypothesis tested using very brief, one- to eight-cycle vowel segments. The expected performance asymmetry was observed in threshold-like tests of multiple different vowels in Experiments 1-3, and a signal detection design in Experiment 4 helped rule out possible response bias effects. In confirming our counterintuitive prediction, the present study illustrates that a biological and evolutionary perspective can be helpful in understanding indexical cuing in speech.