Stacking-enriched magneto-transport properties of few-layer graphenes

The quantum Hall effects in the sliding bilayer graphene and AAB-stacked trilayer system are investigated by the Kubo formula and the generalized tight-binding model. The various stacking configurations can greatly diversify the magnetic quantization and thus create the rich and unique transport properties. The quantum conductivities are very sensitive to the Fermi energy and magnetic-field strength. The diverse features cover the specific non-integer conductivities, the integer conductivities with the distinct steps, the splitting-created reduction and complexity of quantum conductivity, a vanishing or non-zero conductivity at the neutral point, and the well-like, staircase, composite, and abnormal plateau structures in the field-dependencies. Such stacking-dependent characteristics mainly originate from the crossing, anticrossing and splitting Landau-level energy spectra and three kinds of quantized modes.Comment: 33 pages, 10 figure

Phenotype-based and Self-learning Inter-individual Sleep Apnea Screening with a Level IV Monitoring System

Purpose: We propose a phenotype-based artificial intelligence system that can self-learn and is accurate for screening purposes, and test it on a Level IV monitoring system. Methods: Based on the physiological knowledge, we hypothesize that the phenotype information will allow us to find subjects from a well-annotated database that share similar sleep apnea patterns. Therefore, for a new-arriving subject, we can establish a prediction model from the existing database that is adaptive to the subject. We test the proposed algorithm on a database consisting of 62 subjects with the signals recorded from a Level IV wearable device measuring the thoracic and abdominal movements and the SpO2. Results: With the leave-one cross validation, the accuracy of the proposed algorithm to screen subjects with an apnea-hypopnea index greater or equal to 15 is 93.6%, the positive likelihood ratio is 6.8, and the negative likelihood ratio is 0.03. Conclusion: The results confirm the hypothesis and show that the proposed algorithm has great potential to screen patients with SAS

Phenotype-Based and Self-Learning Inter-Individual Sleep Apnea Screening With a Level IV-Like Monitoring System

Purpose: We propose a phenotype-based artificial intelligence system that can self-learn and is accurate for screening purposes and test it on a Level IV-like monitoring system.Methods: Based on the physiological knowledge, we hypothesize that the phenotype information will allow us to find subjects from a well-annotated database that share similar sleep apnea patterns. Therefore, for a new-arriving subject, we can establish a prediction model from the existing database that is adaptive to the subject. We test the proposed algorithm on a database consisting of 62 subjects with the signals recorded from a Level IV-like wearable device measuring the thoracic and abdominal movements and the SpO2.Results: With the leave-one-subject-out cross validation, the accuracy of the proposed algorithm to screen subjects with an apnea-hypopnea index greater or equal to 15 is 93.6%, the positive likelihood ratio is 6.8, and the negative likelihood ratio is 0.03.Conclusion: The results confirm the hypothesis and show that the proposed algorithm has potential to screen patients with SAS

Generic parameters of trajectory-extending kinetic Monte Carlo for calculating diffusion coefficients

One of the challenging applications of molecular dynamics (MD) simulations is to determine the dynamic properties such as the diffusion coefficient of the molecule of interest, particularly slow dynamic systems such as hydrogels and polymer melts. Recently, Neyertz et al. proposed a trajectory- extending kinetic Monte Carlo (TEKMC) algorithm combining both MD and kinetic Monte Carlo to probe the penetrant diffusion within the glassy polymer systems (S. Neyertz and D. Brown, Macromolecules 43, 9210, 2010). Yet, the original TEKMC relies on the manual adjustments of the key parameters of the sampling interval τ and the discretizing grid size rgrid, which limits its applicability to systems with unknown kinetic properties. Here, we reviewed the theoretical background of kinetic Monte Carlo to establish the generic criteria for selecting TEKMC parameters. Also, we modified and expanded the TEKMC algorithm for bulk fluid systems. The modified TEKMC algorithm were applied to systems with various kinetic properties, including Lennard Jones liquid, bulk water, Li+ liquid electrolyte, and Li+ polymer electrolyte. The diffusion coefficients obtained from the modified TEKMC and the generic parameter selections were promising and robust compared with the conventional MD results. With the proposed TEKMC approach, one can extend the MD trajectories to unambiguously characterize the diffusion behavior in the long-time diffusive regime

Effects of Cholesterol on Water Permittivity of Biomimetic Ion Pair Amphiphile Bilayers: Interplay between Membrane Bending and Molecular Packing

Ion pair amphiphile (IPA), a molecular complex composed of a pair of cationic and anionic amphiphiles, is an inexpensive phospholipid substitute to fabricate vesicles with various pharmaceutical applications. Modulating the physicochemical and permeation properties of IPA vesicles are important for carrier designs. Here, we applied molecular dynamics simulations to examine the cholesterol effects on the structures, mechanics, and water permittivity of hexadecyltrimethylammonium-dodecylsulfate (HTMA-DS) and dodecyltrimethylammonium- hexadecylsulfate (DTMA-HS) IPA bilayers. Structural and mechanical analyses indicate that both IPA systems are in gel phase at 298 K. Adding cholesterol induces alkyl chain ordering around the rigid sterol ring and increases the cavity density within the hydrophilic region of both IPA bilayers. Furthermore, the enhanced alkyl chain ordering and the membrane deformation energy induced by cholesterol increase the permeation free energy penalty. In contrast, cholesterol has minor effects on the water local diffusivities within IPA membranes. Overall, the cholesterol reduces the water permittivity of rigid IPA membranes due to the synergistic effects of increased alkyl chain ordering and enhanced membrane mechanical modulus. The results provide molecular insights into the effects of molecular packing and mechanical deformations on the water permittivity of biomimetic IPA membranes, which is critical for designing IPA vesicular carriers.</jats:p

Light-Enhanced Catalytic Activity of Intermetallic PdCd Nanocubes for Suzuki Coupling

Secondary non-noble metals have frequently been introduced to metal nanocrystals to modify their physicochemical properties and decrease the amount of precious metal used. However, this usually causes deactivation. Here, we synthesized intermetallic PdCd nanocubes that not only preserved the catalytic activity but also exhibited an increase in catalytic activity upon illumination. The intermetallic PdCd nanocubes, which are typically identified as the face-centered tetragonal phase, were verified to have a body-centered tetragonal phase theoretically with all exposed facets bounded by Pd atoms and the maximum number of active Pd sites in the alloyed structure. Examination of the physicochemical properties of the intermetallic PdCd nanocubes compared with those of pure Pd nanocubes in a Suzuki coupling reaction as a proof of concept revealed that the intermetallic PdCd nanocubes preserved the catalytic activity, decreased the amount of Pd metal used, and increased catalytic activity by 27% upon illumination. This increase can be attributed to an increase in the number of s-band free electrons upon doping of Cd atoms