Unidirectional Alignment of AgCN Microwires on Distorted Transition Metal Dichalcogenide Crystals.

Van der Waals epitaxy on the surface of two-dimensional (2D) layered crystals has gained significant research interest for the assembly of well-ordered nanostructures and fabrication of vertical heterostructures based on 2D crystals. Although van der Waals epitaxial assembly on the hexagonal phase of transition metal dichalcogenides (TMDCs) has been relatively well characterized, a comparable study on the distorted octahedral phase (1T' or Td) of TMDCs is largely lacking. Here, we investigate the assembly behavior of one-dimensional (1D) AgCN microwires on various distorted TMDC crystals, namely 1T'-MoTe2, Td-WTe2, and 1T'-ReS2. The unidirectional alignment of AgCN chains is observed on these crystals, reflecting the symmetry of underlying distorted TMDCs. Polarized Raman spectroscopy and transmission electron microscopy directly confirm that AgCN chains display the remarkable alignment behavior along the distorted chain directions of underlying TMDCs. The observed unidirectional assembly behavior can be attributed to the favorable adsorption configurations of 1D chains along the substrate distortion, which is supported by our theoretical calculations and observation of similar assembly behavior from different cyanide chains. The aligned AgCN microwires can be harnessed as facile markers to identify polymorphs and crystal orientations of TMDCs.

Layered Aluminum for Electromagnetic Wave Absorber with Near-Zero Reflection.

Ideal electromagnetic (EM) wave absorbers can absorb all incident EM waves, regardless of the incident direction, polarization, and frequency. Absorptance and reflectance are intrinsic material properties strongly correlated with electrical conductivity; hence, achieving perfect absorptance with zero reflectance is challenging. Herein, we present a design strategy for preparing a nearly ideal EM absorber based on a layered metal that maximizes absorption by utilizing multiple internal reflections and minimizes reflection using a monotonic gradient of intrinsic impedance. This approach was experimentally verified using aluminum nanoflakes prepared via topochemical etching of lithium from Li9Al4, and the impedance-graded structure was obtained through the size-based sorting behavior of aluminum nanoflakes sinking in dispersion. Unlike in traditional shielding materials, strong absorption (26.76 dB) and negligible reflectivity (0.04 dB) with a ratio of >103 can be achieved in a 120 µm thick film. Overall, our findings exhibit potential for developing a novel class of antireflective shielding materials.

Enhancement of Thermoelectric Performance in Na-Doped Pb0.6Sn0.4Te0.95- xSe xS0.05 via Breaking the Inversion Symmetry, Band Convergence, and Nanostructuring by Multiple Elements Doping.

Topological insulators have attracted much interest in topological states of matter featuring unusual electrical conduction behaviors. It has been recently reported that a topological crystalline insulator could exhibit a high thermoelectric performance by breaking its crystal symmetry via chemical doping. Here, we investigate the multiple effects of Na, Se, and S alloying on thermoelectric properties of a topological crystalline insulator Pb0.6Sn0.4Te. The Na doping is known to be effective for breaking the crystalline mirror symmetry of Pb0.6Sn0.4Te. We demonstrate that simultaneous emergence of band convergence by Se alloying and nanostructuring by S doping enhance the power factor and decrease lattice thermal conductivity, respectively. Remarkably, the high power factor of 22.3 µW cm-1 K-2 at 800 K is achieved for Na 1%-doped Pb0.6Sn0.4Te0.90Se0.05S0.05 mainly due to a relatively high Seebeck coefficient via band convergence by Se alloying as well as the suppression of bipolar conduction at high temperatures by the increase of energy band gap. Furthermore, the lattice thermal conductivity is significantly suppressed by PbS nanoprecipitates without deteriorating the hole carrier mobility, ranging from 0.80 W m-1 K-1 for Pb0.6Sn0.4Te to 0.17 W m-1 K-1 at 300 K for Pb0.6Sn0.4Te0.85Se0.10S0.05. As a result, the synergistically combined effects of breaking the crystalline mirror symmetry of topological crystalline insulator, band convergence, and nanostructuring for Pb0.6Sn0.4Te0.95- xSe xS0.05 ( x = 0, 0.05, 0.1, 0.2, and 0.95) give rise to an impressively high ZT of 1.59 at 800 K for x = 0.05. We suggest that the multiple doping in topological crystalline insulators is effective for improving the thermoelectric performance.

Reliability of thoracic spine rotation range-of-motion measurements in healthy adults.

CONTEXT: The reliability of clinical techniques to quantify thoracic spine rotation range of motion (ROM) has not been evaluated. OBJECTIVE: To determine the intratester and intertester reliability of 5 thoracic rotation measurement techniques. DESIGN: Descriptive laboratory study. SETTING: University research laboratory. PATIENTS OR OTHER PARTICIPANTS: Forty-six healthy volunteers (age = 23.6 ± 4.3 years, height = 171.0 ± 9.6 cm, mass = 71.4 ± 16.7 kg). MAIN OUTCOME MEASURE(S): We tested 5 thoracic rotation ROM techniques over 2 days: seated rotation (bar in back and front), half-kneeling rotation (bar in back and front), and lumbar-locked rotation. On day 1, 2 examiners obtained 2 sets of measurements (sessions 1, 2) to determine the within-session intertester reliability and within-day intratester reliability. A single examiner obtained measurements on day 2 (session 3) to determine the intratester reliability between days. Each technique was performed 3 times per side, and averages were used for data analysis. Reliability was determined using intraclass correlation coefficients, standard error of measurement (SEM), and minimal detectable change (MDC). Differences between raters during session 1 were determined using paired t tests. RESULTS: Within-session intertester reliability estimates ranged from 0.85 to 0.94. Ranges for the SEM were 1.0° to 2.3° and for the MDC were 2.8° to 6.3°. No differences were seen between examiners during session 1 for seated rotation (bar in front, both sides), half-kneeling rotation (bar in front, left side), or the lumbar locked position (both sides) (all values of P > .05). Within-day intratester reliability estimates ranged from 0.86 to 0.95. Ranges for the SEM were 0.8° to 2.1° and for the MDC were 2.1 ° to 5.9°. Between-days intratester reliability estimates ranged from 0.84 to 0.91. Ranges for the SEM were 1.4° to 2.0° and for the MDC were 3.9° to 5.6°. CONCLUSIONS: All techniques had good reliability and low levels of measurement error. The seated rotation, bar in front, and lumbar-locked rotation tests may be used reliably when more than 1 examiner is obtaining measurements.