Impairment-based therapy for apraxia of speech: a single case study

This paper describes a controlled therapy study with a 54 year-old man (FB) with apraxia of speech (AOS). The therapy involved articulatory-kinematic techniques and facilitation of lexical retrieval using sets of high-frequency (HF) and low- frequency (LF) consonant-vowel-consonant words (e.g. fish, bus). FB showed a striking reduction in multiple attempts on word production tasks, and this generalised modestly to conversation in the clinic. He also improved more on treated HF words than on matched untreated HF words or LF words (treated and untreated), and appeared to improve more on Repetition than Naming and Reading

Insight into determinants of substrate binding and transport in a multidrug efflux protein

Multidrug resistance arising from the activity of integral membrane transporter proteins presents a global public health threat. In bacteria such as Escherichia coli, transporter proteins belonging to the major facilitator superfamily make a considerable contribution to multidrug resistance by catalysing efflux of myriad structurally and chemically different antimicrobial compounds. Despite their clinical relevance, questions pertaining to mechanistic details of how these promiscuous proteins function remain outstanding, and the role(s) played by individual amino acid residues in recognition, binding and subsequent transport of different antimicrobial substrates by multidrug efflux members of the major facilitator superfamily requires illumination. Using in silico homology modelling, molecular docking and mutagenesis studies in combination with substrate binding and transport assays, we identified several amino acid residues that play important roles in antimicrobial substrate recognition, binding and transport by Escherichia coli MdtM, a representative multidrug efflux protein of the major facilitator superfamily. Furthermore, our studies suggested that ‘aromatic clamps’ formed by tyrosine and phenylalanine residues located within the substrate binding pocket of MdtM may be important for antimicrobial substrate recognition and transport by the protein. Such ‘clamps’ may be a structurally and functionally important feature of all major facilitator multidrug efflux proteins

A New Look at an Old Cluster: The Membership, Rotation, and Magnetic Activity of Low-Mass Stars in the 1.3-Gyr-Old Open Cluster NGC 752

The nearby open cluster NGC 752 presents a rare opportunity to study stellar properties at ages >1 Gyr. However, constructing a membership catalog for it is challenging; most surveys have been limited to identifying its giants and dwarf members earlier than mid-K. We supplement past membership catalogs with candidates selected with updated photometric and proper-motion criteria, generating a list of 258 members, a >50% increase over previous catalogs. Using a Bayesian framework to fit MESA Isochrones & Stellar Tracks evolutionary models to literature photometry and the Tycho-Gaia Astrometric Solution data available for 59 cluster members, we infer the age of, and distance to, NGC 752: 1.34$\pm$0.06 Gyr and 438$_{-6}^{+8}$ pc. We also report the results of our optical monitoring of the cluster using the Palomar Transient Factory. We obtain rotation periods for 12 K and M cluster members, the first periods measured for such low-mass stars with a well-constrained age >1 Gyr. We compare these new periods to data from the younger clusters Praesepe and NGC 6811, and to a theoretical model for angular-momentum loss, to examine stellar spin down for low-mass stars over their first 1.3 Gyr. While on average NGC 752 stars are rotating more slowly than their younger counterparts, the difference is not significant. Finally, we use our spectroscopic observations to measure Halpha for cluster stars, finding that members earlier than $\approx$M2 are magnetically inactive, as expected at this age. Forthcoming Gaia data should solidify and extend the membership of NGC 752 to lower masses, thereby increasing its importance for studies of low-mass stars.Comment: Accepted to ApJ. This version 23 pages, 15 figures; on-line version will include 11 more figures as well as light curve data for the 12 rotators we identif

Contact-less measurements of Shubnikov-de Haas oscillations in the magnetically ordered state of CeAgSb2_2 and SmAgSb2_2 single crystals

Shubnikov - de Haas oscillations were measured in single crystals of highly metallic antiferromagnetic SmAgSb$_{2}$ and ferromagnetic CeAgSb$_{2}$ using a tunnel diode resonator. Resistivity oscillations as a function of applied magnetic field were observed via measurements of skin depth variation. The effective resolution of $\Delta\rho\simeq20$ p$\Omega$ allows a detailed study of the SdH spectra as a function of temperature. The effects of the Sm long - range magnetic ordering as well as its electronic structure ($4f$-electrons) on the Fermi surface topology is discussed

Topological insulator-based Dirac hyperbolic metamaterial with large mode indices

Hyperbolic metamaterials (HMMs) are engineered materials with a hyperbolic isofrequency surface, enabling a range of novel phenomena and applications including negative refraction, enhanced sensing, and subdiffraction imaging, focusing, and waveguiding. Existing HMMs primarily work in the visible and infrared spectral range due to the inherent properties of their constituent materials. Here we demonstrate a THz-range Dirac HMM using topological insulators (TIs) as the building blocks. We find that the structure houses up to three high-wavevector volume plasmon polariton (VPP) modes, consistent with transfer matrix modeling. The VPPs have mode indices ranging from 126 to 531, 10-100x larger than observed for VPP modes in traditional media while maintaining comparable quality factors. We attribute these properties to the two-dimensional Dirac nature of the electrons occupying the topological insulator surface states. Because these are van der Waals materials, these structures can be grown at a wafer-scale on a variety of substrates, allowing them to be integrated with existing THz structures and enabling next-generation THz optical devices

Near-field spectroscopy of Dirac plasmons in Bi2Se3 ribbon arrays

Plasmons supported in the massless electron surface states of topological insulators (TIs), known as Dirac plasmons, have great potential in next generation optoelectronics. However, their inherent confinement to the surface makes the investigation of Dirac plasmons challenging. Near-field techniques provide the ideal platform to directly probe Dirac plasmons due to the sensitivity to evanescent fields at the surface. Here, we demonstrate the use of aperture near-field spectroscopy for the investigation of localized terahertz (THz) Dirac plasmon resonances in Bi2Se3 ribbon arrays with widths ranging from 10 to 40 µm. Unlike scattering THz near-field techniques, the aperture method is most sensitive to plasmons with the relevant lower-momenta corresponding to plasmon wavelengths on the scale of ∼20 µm. The combination of THz time-domain spectroscopy and aperture near-field microscopy enables sampling of localized Dirac plasmons in the near-field zone in the 0.5–2.5 THz range. We map the plasmon dispersion, which reveals a coupled plasmon–phonon polariton interaction. The near-field spectra show a higher contrast of the upper polariton branch in comparison with far-field observations. The information revealed by aperture near-field spectroscopy could deepen our understanding of the behavior of Dirac plasmons, leading to the potential development of real-world TI devices

Numerically dominant species drive patterns in resource use along a vertical gradient in tropical ant assemblages

Resource availability can influence the foraging strategy adopted by different ant species as they endeavor to meet nutrient demands of the colony. In tropical rain forests, environmental conditions including resource availability vary over a vertical gradient. Consequently, nitrogen is predicted to become more limiting than carbohydrates toward the canopy as food webs shift to become more reliant on plant‐based resources. We used a “bait‐choice” experiment in a tropical rain forest to examine differences in protein and carbohydrate use with height and determined whether there were differences in response between common (numerically dominant) and rare species. Additionally, we investigated the nutrient use at the species level. Using species co‐occurrence analysis, we examined interspecific competition by testing the co‐occurrence of ant species at the tree level. Over the 12 trees investigated, 124 morphospecies were identified with eight species comprising 90% of total ant abundance. Species richness and protein use increased with height of bait for all species pooled and for common species but not rare species. Correspondingly, relative carbohydrate use decreased with height. We found greater species richness of rare species on carbohydrate baits compared with protein baits. Ant species were randomly distributed among trees when all species were included in co‐occurrence analysis. However, when only common species were considered, segregation between species was evident among trees providing evidence for the presence of ant mosaics. Our results suggest that nitrogen limitation in the canopy may not be true for the whole ant assemblage but rather for the few common species.DATA AVAILABILITY STATEMENT: Data are archived with the Environmental Information Data Centre (EIDC)/NERC, https://doi.org/10.5285/62bf0 251-ca8d-4288-a274-0ff6e39b3a3c (Law & Parr, 2019). Voucher specimens are retained at the University of Liverpool and the Universiti Malaysia Sabah.This publication is a contribution from the UK NERC-funded Biodiversity and Land-use Impacts on Tropical Ecosystem Function (BALI) consortium (http://bali.hmtf.info) (NERC grant no. NE/L000016/1) and was supported by the South-East Asian Rainforest Research Partnership (SEARRP) with permission from the Maliau Basin Management Committee. SL was funded by the University of Liverpool.http://wileyonlinelibrary.com/journal/btphj2020Zoology and Entomolog