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Fengcheng Wu, Timothy Lovorn, A H MacDonald
Moiré patterns are common in van der Waals heterostructures and can be used to apply periodic potentials to elementary excitations. We show that the optical absorption spectrum of transition metal dichalcogenide bilayers is profoundly altered by long period moiré patterns that introduce twist-angle dependent satellite excitonic peaks. Topological exciton bands with nonzero Chern numbers that support chiral excitonic edge states can be engineered by combining three ingredients: (i) the valley Berry phase induced by electron-hole exchange interactions, (ii) the moiré potential, and (iii) the valley Zeeman field...
April 7, 2017: Physical Review Letters
Cai-Zhi Xu, Yang-Hao Chan, Yige Chen, Peng Chen, Xiaoxiong Wang, Catherine Dejoie, Man-Hong Wong, Joseph Andrew Hlevyack, Hyejin Ryu, Hae-Young Kee, Nobumichi Tamura, Mei-Yin Chou, Zahid Hussain, Sung-Kwan Mo, Tai-Chang Chiang
Three-dimensional (3D) topological Dirac semimetals (TDSs) are rare but important as a versatile platform for exploring exotic electronic properties and topological phase transitions. A quintessential feature of TDSs is 3D Dirac fermions associated with bulk electronic states near the Fermi level. Using angle-resolved photoemission spectroscopy, we have observed such bulk Dirac cones in epitaxially grown α-Sn films on InSb(111), the first such TDS system realized in an elemental form. First-principles calculations confirm that epitaxial strain is key to the formation of the TDS phase...
April 7, 2017: Physical Review Letters
Josefine Eilsø Nielsen, Kaizheng Zhu, Sverre Arne Sande, Lubomír Kováčik, Dušan Cmarko, Kenneth Dahl Knudsen, Bo Nyström
Thermoresponsive amphiphilic biodegradable block copolymers of the type poly(-caprolactone-co-lactide)-poly(ethylene glycol)-poly(-caprolactone-co-lactide) (PCLA-PEGm-PCLA) have great potential for various biomedical applications. In the present study, we have surveyed the effects of PEG-spacer length (m=1000 and 1500), temperature, and polymer concentration on the self-assembling process to form supramolecular structures in aqueous solutions of the PCLA-PEGm-PCLA copolymer. This copolymer has a lower critical solution temperature, and the cloud point depends on both concentration and PEG-length...
April 21, 2017: Journal of Physical Chemistry. B
Markus Eschbach, Martin Lanius, Chengwang Niu, Ewa Młyńczak, Pika Gospodarič, Jens Kellner, Peter Schüffelgen, Mathias Gehlmann, Sven Döring, Elmar Neumann, Martina Luysberg, Gregor Mussler, Lukasz Plucinski, Markus Morgenstern, Detlev Grützmacher, Gustav Bihlmayer, Stefan Blügel, Claus M Schneider
New three-dimensional (3D) topological phases can emerge in superlattices containing constituents of known two-dimensional topologies. Here we demonstrate that stoichiometric Bi1Te1, which is a natural superlattice of alternating two Bi2Te3 quintuple layers and one Bi bilayer, is a dual 3D topological insulator where a weak topological insulator phase and topological crystalline insulator phase appear simultaneously. By density functional theory, we find indices (0;001) and a non-zero mirror Chern number. We have synthesized Bi1Te1 by molecular beam epitaxy and found evidence for its topological crystalline and weak topological character by spin- and angle-resolved photoemission spectroscopy...
April 21, 2017: Nature Communications
T Sui, E Salvati, S Ying, G Sun, I P Dolbnya, K Dragnevski, C Prisacariu, A M Korsunsky
The strain-induced softening of thermoplastic polyurethane elastomers (TPUs), known as the Mullins effect, arises from their multi-phase structure. We used the combination of small- and wide- angle X-ray scattering (SAXS/WAXS) during in situ repeated tensile loading to elucidate the relationship between molecular architecture, nano-strain, and macro-scale mechanical properties. Insights obtained from our analysis highlight the importance of the 'fuzzy interface' between the hard and soft regions that governs the structure evolution at nanometre length scales and leads to macroscopic stiffness reduction...
April 20, 2017: Scientific Reports
Filippo Rossi, Franca Castiglione, Matteo Salvalaglio, Monica Ferro, Marta Moioli, Emanuele Mauri, Maurizio Masi, Andrea Mele
A huge number of studies and work in the drug delivery literature are focused on understanding and modeling transport phenomena, the pivotal point for a good device design. The rationalization of all phenomena involved is fundamental, but several concerns arise leaving many issues unsolved. In order to change the point of view we decided to focus our attention on the parallelisms between two fields that seem to be very far from each other: chromatography and drug release. Taking advantages of the studies conducted by many researchers using chromatographic columns we decided to explain all the phenomena involved in drug delivery considering sodium ibuprofen (IP) molecules as analytes and hydrogel as a stationary phase...
April 20, 2017: Physical Chemistry Chemical Physics: PCCP
P Passos, J Milho, C Button
Collective behaviors in team sports result in players forming interpersonal synergies that contribute to performance goals. Because of the huge amount of variables that continuously constrain players' behavior during a game, the way that these synergies are formed remain unclear. Our aim was to quantify interpersonal synergies in the team sport of Rugby Union. For that purpose we used the Uncontrolled Manifold Hypothesis (UCM) to identify interpersonal synergies that are formed between ball carrier and support player in two-versus-one situations in Rugby Union...
April 19, 2017: Behavior Research Methods
Nicolas Brodusch, Raynald Gauvin
Electron channelling is known to affect the x-ray production when an accelerated electron beam is applied to a crystalline material and is highly dependent on the local crystal orientation. This effect, unless very long counting time are used, is barely noticeable on x-ray energy spectra recorded with conventional silicon drift detectors (SDD) located at a small elevation angle. However, the very high count rates provided by the new commercially available annular SDDs permit now to observe this effect routinely and may, in some circumstances, hide the true elemental x-ray variations due to the local true specimen composition...
April 18, 2017: Journal of Microscopy
Victor R Carlson, Frances T Sheehan, Aricia Shen, Lawrence Yao, Jennifer N Jackson, Barry P Boden
BACKGROUND: The tibial tubercle to trochlear groove (TT-TG) distance is used for screening patients with a variety of patellofemoral joint disorders to determine who may benefit from patellar medialization using a tibial tubercle osteotomy. Clinically, the TT-TG distance is predominately based on static imaging with the knee in full extension; however, the predictive ability of this measure for dynamic patellar tracking patterns is unknown. PURPOSE: To determine whether the static TT-TG distance can predict dynamic lateral displacement of the patella...
April 1, 2017: American Journal of Sports Medicine
Zachary A Steelman, Will J Eldridge, Jacob B Weintraub, Adam Wax
The refractive index (RI) of biological materials is a fundamental parameter for the optical characterization of living systems. Numerous light scattering technologies are grounded in a quantitative knowledge of the refractive index at cellular and subcellular scales. Recent work in quantitative phase microscopy (QPM) has called into question the widely held assumption that the index of the cell nucleus is greater than that of the cytoplasm, a result which disagrees with much of the current literature. In this work, we critically examine the measurement of the nuclear and whole-cell refractive index using QPM, validating that nuclear refractive index is lower than that of cytoplasm in four diverse cell lines and their corresponding isolated nuclei...
April 18, 2017: Journal of Biophotonics
Christopher P J Schubert, Carsten Müller, Andreas Bogner, Frank Giesselmann, Robert P Lemieux
Structural variants of the 'de Vries-like' mesogen 5-[4-(12,12,14,14,16,16-hexamethyl-12,14,16-trisilaheptadecyloxy)phenyl]-2-hexyloxypyrimidine (QL16-6), including two isomers with branched iso-tricarbosilane end-groups, were synthesized and their mesomorphic and 'de Vries-like' properties were characterized by polarized optical microscopy, differential scanning calorimetry, small angle and 2D X-ray scattering techniques. A comparative analysis of isomers with linear and branched tricarbosilane end-groups shows that they exhibit comparable mesomorphic and 'de Vries-like' properties...
April 18, 2017: Soft Matter
Jenny Marie Andersson, Carl Grey, Marcus Larsson, Tiago Mendes Ferreira, Emma Sparr
The lipid-protein film covering the interface of the lung alveolar in mammals is vital for proper lung function and its deficiency is related to a range of diseases. Here we present a molecular-level characterization of a clinical-grade porcine lung surfactant extract using a multitechnique approach consisting of [Formula: see text]-[Formula: see text] solid-state nuclear magnetic spectroscopy, small- and wide-angle X-ray scattering, and mass spectrometry. The detailed characterization presented for reconstituted membranes of a lung extract demonstrates that the molecular structure of lung surfactant strongly depends on the concentration of cholesterol...
April 17, 2017: Proceedings of the National Academy of Sciences of the United States of America
Qintang Li, Meihuan Yao, Xiu Yue, Xiao Chen
The aggregation behavior of quaternary ammonium gemini surfactants (12-s-12) in a protic ionic liquid, ethanolammonium nitrate (EOAN), was investigated by small-angle X-ray scattering, freeze-fracture transmission electron microscopy, polarized optical microscopy, and rheological measurements. The rarely reported nonaqueous two phases in the ionic liquid were observed at lower 12-s-12 concentrations. The upper phase was composed of micelles, whereas only the surfactant unimers or multimers were detected in the low phase...
April 20, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Michel Y Louge
We outline a statistical mechanics of the triple gas-solid-liquid contact line on a rough plane. The analysis regards the neighborhood of the line as a solid dotted with cavities. It adopts the simplest mean-field statistical mechanics, in which each cavity is either full or empty, while being connected to near neighbors by thin necks. The theory predicts equilibrium angles for advance and recession in terms of the Young contact angle and the joint statistical distribution of two quantifiable geometrical parameters representing specific neck cross-section and specific cavity opening...
March 2017: Physical Review. E
Sébastien Leclaire, Andrea Parmigiani, Orestis Malaspinas, Bastien Chopard, Jonas Latt
This article presents a three-dimensional numerical framework for the simulation of fluid-fluid immiscible compounds in complex geometries, based on the multiple-relaxation-time lattice Boltzmann method to model the fluid dynamics and the color-gradient approach to model multicomponent flow interaction. New lattice weights for the lattices D3Q15, D3Q19, and D3Q27 that improve the Galilean invariance of the color-gradient model as well as for modeling the interfacial tension are derived and provided in the Appendix...
March 2017: Physical Review. E
H T Nguyen, C Reichhardt, C J Olson Reichhardt
We numerically examine clogging transitions for bidisperse disks flowing through a two-dimensional periodic obstacle array. We show that clogging is a probabilistic event that occurs through a transition from a homogeneous flowing state to a heterogeneous or phase-separated jammed state where the disks form dense connected clusters. The probability for clogging to occur during a fixed time increases with increasing particle packing and obstacle number. For driving at different angles with respect to the symmetry direction of the obstacle array, we show that certain directions have a higher clogging susceptibility...
March 2017: Physical Review. E
S P Sreenilayam, D M Agra-Kooijman, V P Panov, V Swaminathan, J K Vij, Yu P Panarin, A Kocot, A Panov, D Rodriguez-Lojo, P J Stevenson, Michael R Fisch, Satyendra Kumar
A heptamethyltrisiloxane liquid crystal (LC) exhibiting I-SmA^{*}-SmC^{*} phases has been characterized by calorimetry, polarizing microscopy, x-ray diffraction, electro-optics, and dielectric spectroscopy. Observations of a large electroclinic effect, a large increase in the birefringence (Δn) with electric field, a low shrinkage in the layer thickness (∼1.75%) at 20 °C below the SmA^{*}-SmC^{*} transition, and low values of the reduction factor (∼0.40) suggest that the SmA^{*} phase in this material is of the de Vries type...
March 2017: Physical Review. E
Salma Alrasheed, Enzo Di Fabrizio
Metasurfaces are new, promising ultrathin materials that can enable many novel optical devices due to their ability to act as a discontinuity interface that introduces an abrupt change in amplitude, phase, and sometimes the polarization of the incident light at the wavelength scale. Therefore they can function as flat optical elements. Here, we investigate the anomalous reflection of light for transverse-magnetic (TM) polarization for normal and oblique incidence in the visible regime. We propose gradient phase gap-surface plasmon metasurfaces that exhibit high conversion efficiency (up to ∼97% of total reflected light) to the anomalous reflection angle for blue, green, and red wavelengths at normal and oblique incidence, and where light polarization is unchanged after the reflection...
April 10, 2017: Applied Optics
Leah Bergquist, Cuiyu Zhang, Roberta R Ribeiro de Almeida, Brittany Pellegrene, Miroslaw Salamonczyk, Matthew Kim, Jung-Im Hwang, Kyeong-Jin Kim, Joun-Ho Lee, Antal Jákli, Torsten Hegmann
We report on the synthesis and characterization of bent-core liquid crystal (LC) compounds and the preparation of mixtures that provide an optically isotropic antiferroelectric (OI-AFLC) liquid crystal display mode over a very wide temperature interval and well below room temperature. From the collection of compounds synthesized during this study, we recognized that several ternary mixtures displayed a modulated SmCaPA phase down to below -40 °C and up to about 100 °C on both heating and cooling, as well as optical tilt angles in the transformed state of approximately 45° (optically isotropic state)...
April 2017: ChemistryOpen
Almat Raskaliyev, Sarosh Patel, Tarek Sobh
A computational algorithm is developed for estimating accurately the attitude of a robotic arm which moves along a predetermined path. This algorithm requires preliminary input data obtained in the static mode to yield phase observables for the precise, 3-axis attitude determination of a swinging manipulator in the dynamic mode. Measurements are recorded simultaneously by three GPS L1 receivers and then processed in several steps to accomplish this task. First, artkconv batch executable converts GPS receiver readings into RINEX format to generate GPS observables and ephemeris for multiple satellites...
July 2017: Journal of Advanced Research
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