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In this study, a series of hindered urea bond (HUB) containing polyurethane-urea methacrylate prepolymers and a none HUB containing polyurethane methacrylate prepolymer were prepared using isobornyl methacrylate as the reactive diluent via one-pot procedure. The prepolymers were characterized fully by various techniques. Then, their thermosets were fabricated via UV curing in presence of a photo initiator, and their mechanical property and thermal behavior were investigated and compared. Different from the none HUB containing thermoset, the HUB containing thermosets (defined as PUT) could be recycled and reprocessed by hot press under relatively mild conditions with high recovery ratio of mechanical property. Furthermore, zinc oxide (ZnO) nanoparticles were modified with 3-(trimethoxysilyl) propyl methacrylate and the modified ZnO (defined as ZnO-TPM) was dispersed and polymerized into PUT matrix to prepare their nanocomposites. The influence of ZnO-TPM on the mechanical performance of the composites was evaluated, which indicated that the Young's modulus and tensile strength increased gradually to the maximum values at ZnO-TPM content of 1 wt% and then decreased. The composites also displayed good reprocessability with improved recovery ratio compared to the pure PUT sample. In addition, the composite materials exhibited strong UV absorption capacity, implying their potential application in the circumstance where UV-shielding was required. [ABSTRACT FROM AUTHOR]

The development of bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is highly desirable for fuel cells and rechargeable metal–air batteries. Till now, it is still challenging to achieve both efficient activities on a single commercial noble-metal catalyst. Recently, N, P co-doped graphene has shown good bifunctional evidence. However, the atomic-scale understanding of the bifunctional mechanism is still lacking. Here, we show that the N and P atoms prefer to bond with each other, forming embedded N-P clusters in graphene. The catalytic performances of the N-P clusters are sensitive to their geometries, especially the N:P ratios. The N:P ratio of ∼2 is optimal for OER, while ∼3 is optimal for ORR. Through evaluating the ORR/OER potential gaps, we found that the N-P cluster designated as N C 2 P C 1 shows both the high performances of ORR and OER, responsible for the unique bifunctionality in the N, P co-doped graphene. [ABSTRACT FROM AUTHOR]

Hoya longlingensis (E.F. Huang) and H. sichuanensis E.F. Huang are two new species of Apocynaceae from Southwestern China that are described in this study. Morphologically, the two species resemble H. tamdaoensis Rodda & T.B. Tran and H. lyi H. Lév., respectively. However, H. longlingensis differs from H. tamdaoensis by its elliptic leaves, mid-vein of leaf blades raised adaxially and depressed abaxially, lateral veins 2–4-paired, corolla yellow-green, outer angles of corona convex and spreading outside obviously. While H. sichuanensis differs from H. lyi by its obovate leaves, leaf apex rounded and base cuneate, petioles 1–3.5 cm long and ca. 3 mm in diameter, calyx lobes triangular, and corona whitish. [ABSTRACT FROM AUTHOR]

We have used first principles methods to systematically investigate the quantum confinement effect on the electronic properties of zinc-blende (ZB) and wurtzite (WZ) InAs nanowires (NWs) with different orientations and diameters, and compared their electronic properties before and after pseudo-hydrogen passivation. The results show that the calculated carrier effective masses are dependent on the NW diameter, except for [110] ZB NWs, and the hole effective masses of [111] ZB NWs are larger than the electron effective masses when the NW diameter is ≥26 Å. The band alignments of [111] ZB and [0001] WZ NWs reveal that the effect of quantum confinement on the conduction bands is greater than on the valence bands, and the position of the valence band maximum level changes little with increasing NW diameter. The pseudo-hydrogen passivated NWs have larger band gaps than the corresponding unpassivated NWs. The carrier effective masses and mobilities can be adjusted by passivating the surface dangling bonds. [ABSTRACT FROM AUTHOR]

Ballistic thermoelectric properties (TPs) in boron nitride nanoribbons (BNNRs) are studied using the nonequilibrium Green's function atomistic simulation of electron and phonon transport. A comparative analysis for TPs between BNNRs and graphene nanoribbons (GNRs) is made. Results show that the TPs of BNNRs are better than those of GNRs stemming from the higher power factor and smaller thermal conductance of BNNRs. With increasing the ribbon width, the maximum value of ZT (ZTmax) of BNNRs exhibits a transformation from the monotonic decrease to nonlinear increase. We also show that the lattice defect can enhance the ZTmax of these nanoribbons strongly depending on its positions and the edge shape. [ABSTRACT FROM AUTHOR]

To analyze heat generation in a quantum dot coupled to normal leads and subject to an ac field, a formula is derived for the heat generated Q using the nonequilibrium Keldysh Green's function technique. The numerical results show that the external ac field influences significantly the heat generated. The threshold bias decreases to Vt=ω0-nω through photon absorption. Additional steps emerge from photon-assisted tunneling, and the width of the step is equal to the frequency of photon ω and the height increases with the magnitude of the ac field. For large V/ω, the Q/ω curves display many resonant peaks due to multi-photon absorptions and emissions. Moreover, a negative differential heat generation can be observed as ω>ω0. [ABSTRACT FROM AUTHOR]

Using the density function theory in combination with the non-equilibrium Green's function method, the thermoelectric properties of molecular devices based on transition metal–terpyridine complexes are investigated. The results show that their thermoelectric properties can be significantly improved by changing the transition metal and the twist angle of the complex molecule, which is caused by shifting the molecular energy levels, resulting in increased coupling strength between the electrodes and the central molecule. The ZT value of the Ru-containing molecular device can reach up to 0.9 at room temperature, which is three orders of magnitude greater than that of the graphene nanoribbons of the same width. In addition, its thermoelectric performance can be further promoted by suppressing phonon thermal conductance through enhanced isotope scattering. The ZT value of doped devices can reach up to 1.0 in the range of 300–700 K. This work may help in the design and fabrication of transition metal-containing twistable molecular devices and provide effective methods to regulate their thermoelectric properties. [ABSTRACT FROM AUTHOR]

Using first-principles band structure methods, we investigate the interactions between different donors in In2O3. Through the formation energy and transition energy level calculations, we find that an oxygen-vacancy creates a deep donor level, while an indium-interstitial or a tin-dopant induces a shallow donor level. The coupling between these donor levels gives rise to even shallower donor levels and leads to a significant reduction in their formation energies. Based on the analysis of the PBE0-corrected band structure and the molecular-orbital bonding diagram, we demonstrate these effects of donor–donor binding. In addition, total energy calculations show that these defect pairs tend to be more stable with respect to the isolated defects due to their negative binding energies. Thus, we may design shallow donor levels to enhance the electrical conductivity via the donor–donor binding. [ABSTRACT FROM AUTHOR]

Hybrid metal-organic frameworks have some exotic electronic properties, such as extremely high electron and hole mobilities and nontrivial topological properties. Here, we systematically study the electronic properties of the two-dimensional metal-organic framework semiconductors (MOFSs) (M3S6C6, M=Mg, Ca, Zn, Cd, Ge, and Sn) using the first principles calculations. We find that the metal d band is important in determining the hole transport properties of M3S6C6. The p-d hybridization between the metal d and S-C p bands will delocalize the wavefunction of the band edge states and reduce the effective mass. From group IIA (Mg, Ca) to IVA (Ge, Sn) to IIB (Zn, Cd), as the p-d coupling increases, the hole effective masses dramatically decrease. Additionally, due to the fact that the conduction band minimum of group IIB (Zn, Cd) MOFSs is mainly dominated by the delocalized M s state, they also have the very small electron effective mass. Therefore, the 2D group IIB (Zn, Cd) MOFSs have excellent hole and electron effective masses, which are comparable with the conventional semiconductors and even better than the popular 2D materials WS2 and MoS2. This result suggests that Zn3S6C6 and Cd3S6C6 MOFSs could be the promising 2D semiconductors for the electronic applications. [ABSTRACT FROM AUTHOR]

The effects of magnetic atom on the band structure of zigzag-edged graphene nanoribbons are investigated by the density functional theory. The results show that for narrow zigzag-edged graphene nanoribbons, the band gap can be opened duo to the spin-up/spin-down charges being re-enriched on the edge sites. However, for the wide zigzag-edged graphene nanoribbons, a spin-up/spin-down half-metallic property can be observed. Moreover, it is found that the Seebeck coefficients in the narrow zigzag-edged graphene nanoribbons are reversed and enlarged, which provides a way to design novel thermoelectric device. [ABSTRACT FROM AUTHOR]

Abstract: The phonon scattering and thermal conductance properties have been studied in two coupled graphene nanoribbons connected by different bridge atoms by using density functional theory in combination with non-equilibrium Green's function approach. The results show that a wide range of thermal conductance tuning can be realized by changing the chemical bond strength and atom mass of the bridge atoms. It is found that the chemical bond strength (bridge atom mass) plays the main role in phonon scattering at low (high) temperature. A simple equation is presented to describe the relationship among the thermal conductance, bridge atom, and temperature. [Copyright &y& Elsevier]

Two classic animal behavior despair tests-the forced swimming test (FST) and the tail suspension test (TST) were used to evaluate antidepressant-like activity of a new chalcone compound, chalcone-1203 in mice. It was observed that chalcone-1203 at dose of 1, 5, and 10 mg/kg significantly reduced the immobility time in the FST and TST in mice 30 min after treatment. In addition, chalcone-1203 was found to exhibit significant oral activity in the FST in mice. It also produced a reduction in the ambulation in the open-field test in mice not previously habituated to the arena, but no effect in the locomotor activity in mice previously habituated to the open-field. The main monoamine neurotransmitters and their metabolites in mouse brain regions were also simultaneously determined by HPLC-ECD. It was found that chalcone-1203 significantly increased the concentrations of the main neurotransmitters 5-HT and NE in the hippocampus, hypothalamus and cortex. Chalcone-1203 also significantly reduced the ratio of 5-HIAA/5-HT in the hippocampus and cortex, shown down 5-HT metabolism compared with mice treated with stress vehicle. In conclusion, chalcone-1203 produced significant antidepressant-like activity, and the mechanism of action may be due to increased 5-HT and NE in the mouse hippocampus and cortex. [ABSTRACT FROM AUTHOR]

Abstract: The thermal transport properties of graphene nanoribbons (GNRs) with pentagon–heptagon defect (PHD) are studied by using first principles calculations in combination with non-equilibrium Green’s function approach. The results show that the PHD effect on thermal conduction in armchair-oriented GNR is stronger than that in zigzag-oriented GNR. The out-of-plane acoustic mode is almost reflected by the PHD at a particular frequency. When the temperature is larger than 400K, the thermal conduction ratio is only related to the PHD’s orientation, and insensitive to the width of PHD. These results will be helpful for designing high-performance thermal insulation or thermoelectric device. [Copyright &y& Elsevier]

Abstract: By using first-principles calculations, the magnetic properties of a SnO2 quantum dot (QD) are investigated. It is found that dangling bonds (DBs) are equated with Co (Ni) dopants, which can induce magnetic moments in SnO2 QDs. Thus, the QD shows very abundant variation of the magnetic properties by combining dopants with DBs. The changes of magnetic moments can be explained well by a carrier modulation model. [Copyright &y& Elsevier]

A facile method is reported to controllably fabricate one dimensional (1D) polymer nanostructures via metallogel template polymerization. The metallogel was prepared through coordination interactions between silver ions and a ligand (L) bearing three pyridyl groups in tetrahydrofuran (THF). The diameters of the metallogel nanofibers could be tuned by the gel concentration (GC). Due to its high thermal stability and facility of removal, the metallogel was used as the template for radical polymerization of diacryolyl-2,6-diaminopyridine (DADAP) to form poly-diacryolyl-2,6-diaminopyridine (PDADAP) nanostructures. The gradually eroding of the templates by PDADAP provided us an effective way to fabricate various nanostructures of the polymer. We have demonstrated that different 1D nanostructures, including nanoribbons, nanotubes and nanowires, could be selectively fabricated by adjusting polymerization time, monomer concentration and GC. The rheological properties of the gel samples were tested by a rheometer. As prolonging the reaction time, more and more polymers were formed and the strength of the resulting polymer gels became higher and higher. The simple preparation process, easy controlled microstructures and adequate gel strength would make it a facile synthetic method for different 1D polymer nanosturctures. [ABSTRACT FROM AUTHOR]

The thermoelectric properties in graphene nanoribbons modulated with stub structures are studied using atomistic simulation of electron and phonon transport. The results show that the phonon transport is dramatically suppressed by the elastic scattering of the stub structure; while the thermopower S can be enhanced by a few times of magnitude. This leads to a strong enhancement of the figure of merit (ZT). Moreover, it is found that the enhancement of ZT can be effectively tuned by modulating geometric parameters of the stub and edge shapes, which offers an effective way to improve the thermoelectric performance of graphene nanoribbons. [ABSTRACT FROM AUTHOR]

Five secondary amine terminated poly(ester-amine)s (defined as PEA) with controlled molecular structures were synthesized through reacting excessive piperazine with phthalicdiglycol diacrylate (PDDA) and 1,1,1-trimethylolpropane triacrylate (TMPTA) at a constant secondary amine/acrylate group ratio of 1.5/1 and at different PDDA/TMPTA molar ratios. Both IR and 1H-NMR spectra indicated that all acrylate groups were consumed in the reaction, based on which the structural parameters were calculated from the 1H-NMR spectra. With decreasing PDDA/TMPTA ratio, the content of secondary amine, degree of branching, molecular weight, Tg and Td increased accordingly. These polymers were further used as both crosslinkers and flexibilizers for a linear epoxy resin E51 to form cured films under ambient condition. The gel content, relative hardness and Tg of the resulting films increased as PEA molecules changed from linear to highly branching structures. Due to the flexibility of PEA molecules, all the films possessed excellent mechanical performance. [ABSTRACT FROM AUTHOR]

Abstract: A series of new titanium complexes bearing β-diiminato ligands [(Ph)NC(R1)CHC(R2)N(Ph)]2TiCl2 (4a: R1 =R2 =CH3; 4b: R1 =R2 =CF3; 4c: R1 =Ph, R2 =CH3; 4d: R1 =Ph, R2 =CF3) has been synthesized and characterized. X-ray crystal structures reveal that complexes 4a and 4c adopt distorted octahedral geometry around the titanium center. With modified methylaluminoxane (MMAO) as a cocatalyst, complexes 4a–d are active catalysts for ethylene polymerization, and produce high molecular weight polyethylenes. Catalyst activities and the molecular weights of polymers are considerably influenced by the steric and electronic effects of substituents on the catalyst backbone under the same polymerization condition. With the strong electron-withdrawing groups (CF3) at R1 or/and R2 position, complexes 4b and 4d show higher activities than complexes 4a and 4c, respectively. [Copyright &y& Elsevier]

Abstract: A series of titanium complexes [(Ar)NC(CF3)CHC(R)O]2TiCl2 (4b: Ar=–C6H4OMe(p), R=Ph; 4c: Ar=–C6H4Me(p), R=Ph; 4d: Ar=–C6H4Me(o), R=Ph; 4e: Ar=α-Naphthyl, R=Ph; 4f: Ar=–C6H5, R= t-Bu; 4g: Ar=–C6H4OMe(p); R= t-Bu; 4h: Ar=–C6H4Me(p); R= t-Bu; 4i: Ar=–C6H4Me(o); R= t-Bu) has been synthesized and characterized. X-ray crystal structures reveal that complexes 4b, 4c and 4h adopt distorted octahedral geometry around the titanium center. With modified methylaluminoxane (MMAO) as a cocatalyst, complexes 4b–c and 4f–i are active catalysts for ethylene polymerization and ethylene/norbornene copolymerization, and produce high molecular weight polyethylenes and ethylene/norbornene alternating copolymers. In addition, the complex 4c/MMAO catalyst system exhibits the characteristics of a quasi-living copolymerization of ethylene and norbornene with narrow molecular weight distribution. [Copyright &y& Elsevier]

Twisted bilayer and multilayer two-dimensional materials linked by van der Waals interactions exhibit various unique physical properties. The phonon properties of such systems are of great importance, but have not been explored in detail. In this work, we use a hybrid neural-network potential to systematically investigate the evolution of the phonon structure of twisted multilayer graphene under out-of-plane strain. With increasing out-of-plane strain, the evolution of the phonon structure of the moiré superlattice exhibits different behavior from that of AA and AB stacked multilayer graphene. Meanwhile, with twisting of the interlayer, a higher Grüneisen parameter and a lower phonon group velocity can be obtained. A possible method is revealed by which phonon anharmonic scattering in stacked multilayer graphene could be enhanced by varying the twist angle in combination with out-of-plane strain. Our work shows that the application of out-of-plane strain can serve as an effective way to amplify the effect of twist angle on phonon structures of twisted multilayer two-dimensional systems, with potential application to thermoelectric and thermal logical devices. [ABSTRACT FROM AUTHOR]

Two-dimensional semiconductors are considered as promising channel materials for next-generation nanoelectronics devices, while their practical applications are typically limited by their low mobilities. In this work, using first-principles calculations combined with the Boltzmann transport formalism involving electron–phonon coupling, we study the transport properties of monolayer group-IV monochalcogenides (MX, M = Ge, Sn; X = S, Se, and Te). We find that the GeTe and SnTe possess exceptionally high hole mobilities, which even reach 835 and 1383 cm2/V s, respectively, at room temperature. More interestingly, the hole mobilities increase with the increase in the atomic number of "X" in MXs when "M" remains the same. Such a trend is mainly due to the increased group velocity and decreased density of states, and the latter plays a significant role in determining the carrier scattering space and relaxation time. Meanwhile, different from the acoustic deformation potential theory, we find that the high-energy optical phonons contribute a lot to the scattering. Our work shows that the monolayer GeTe and SnTe are promising p-type semiconductors in nanoelectronics and reveals the intrinsic connection between phonons, charge density of states, and mobility, which would shed light on exploring the two-dimensional materials with high mobility. [ABSTRACT FROM AUTHOR]

By developing the mode matching numerical technique, we investigate the ballistic phonon thermal transport through a cylindrical semiconductor nanowire modulated with a coupling nanocavity. It is found that the phonon transmission exhibits the periodical transmission properties in low frequency region. The resonant transmission and reflection behaviors of acoustic phonon modes at particular energy can be observed. In the limit T → 0, the thermal conductance approaches the universal quantum value π2kB2T/3h, and such a quantum is robust against all geometrical parameters. However, the thermal conductance exhibits nonmonotonic behaviors with increasing temperature and can be modulated by adjusting geometrical parameters of the nanocavity. [ABSTRACT FROM AUTHOR]

Stacking order and strain are the key component in tuning magnetic property of two-dimensional (2D) van der Waals magnetic materials. In this work, we investigated the crystal structure stability of a 2D ferromagnetic Janus chromium dichalcogenide CrSTe bilayer in AB- and AC-stacking orders and found that AB-stacking CrSTe bilayers, which have a smaller layer spacing and a Curie temperature near room temperature, are more stable than AC-stacking one. The magnetic ground states, exchange coupling constant, and Curie temperature of the AB-stacking CrSTe bilayer can be tuned by strain. It is found that the magnetic ground states of the AB- and AC-stacking CrSTe bilayers are ferromagnetic and interlayer antiferromagnetic within a certain strain range, respectively, indicating that the CrSTe bilayers are expected to be used in the double spin filter. Our results demonstrated that the 2D Janus CrSTe bilayer has the potential in the application of spintronic devices with stable performance and low-power consumption at room temperature. [ABSTRACT FROM AUTHOR]

By performing first-principles calculation, we investigated the electronic properties of remotely p-type doping GaSb nanowire by a Zn-doped InAs shell. The results show that for bare zinc-blende (ZB) [111] GaSb/InAs core-shell nanowire the Zn p-type doped InAs shell donates free holes to the non-doped GaSb core nanowire without activation energy, significantly increasing the hole density and mobility of nanowire. For Zn doping in bare ZB [110] GaSb/InAs core-shell nanowire the hole states are compensated by surface states. We also studied the behaviors of remote p-type doing in two-dimensional (2D) GaSb/InAs heterogeneous slabs, and confirmed that the orientation of nanowire side facet is a key factor for achieving high efficient remote p-type doping. [ABSTRACT FROM AUTHOR]

Phonon hydrodynamics, a collective motion of phonons, has recently attracted renewed attention since its temperature window has been greatly extended in layered materials. The exploration of phonon hydrodynamics bears importance in understanding phonon collective behavior, and its window is crucial for determining the phonon transport regime and engineering the heat transport. Thus, strategies for continuous tuning of the hydrodynamic window are needed, but it remains a challenge. In this work, we demonstrate that the phonon hydrodynamic window in bilayer graphene can be strongly altered by the strain based on theoretical calculations. In particular, the phonon hydrodynamics can be observed at 60 K in unstrained bilayer graphene, while only 0.25% strain can reduce this temperature to 28 K. This strong strain dependence not only provides an efficient way of modulating the phonon collective behavior but also renders a possibility of strain-induced transition of phonon transport regime. [ABSTRACT FROM AUTHOR]

Enhanced thermoelectric performance is restricted greatly by the interaction of various transport parameters, and this bottleneck urgently requires a solution. In this paper, first-principles calculations and Boltzmann transport theory are used to study the thermoelectric performance of two-dimensional (PbX) 2 (X = S , Se , Te) monolayers, and it is found that the thermoelectric performance can be enhanced significantly by applying a biaxial tensile strain. The room-temperature ZT values of the p-type (PbS) 2 , (PbSe) 2 , and (PbTe) 2 in zigzag (armchair) directions are boosted as high as 1.97 (1.35), 2.26 (1.31), and 2.45 (1.59), respectively. The results show that it is mainly attributed to the significantly reduced phonon thermal conductivity. Moreover, the sharply reduced phonon thermal conductivity is mainly due to the enhancement of the phonon scattering rate caused by strong phonon anharmonicity. In addition, the excellent ZT value of the p-type (PbX) 2 (X = S , Se , Te) monolayer exhibits their potential application in the thermoelectric field, and the external strain has a good prospect in enhancing the thermoelectric performance. [ABSTRACT FROM AUTHOR]

Using the first-principles calculations, the holes-induced magnetism associated with oxygen vacancy in and has been investigated. To obtain holes, the divalent calcium and tetravalent IVB-group ions are replaced respectively by the monovalent alkali, IB-group and trivalent III-group ions. It is found that the can enhance the magnetic moment of few acceptors-doped , whereas it enhances the magnetic moment in most acceptor-doped except for La doping. Mainly, it is because the gives rise to no gap-states in but generates gap-states in . Based on the similar effect of on the band structure in or in (X = Ca, Sr, Ba), we suggest that there exists a similar effect of on magnetism in acceptor-doped alkaline titanium (zirconium) perovskites. [ABSTRACT FROM AUTHOR]

We investigate the thermal conductivity in the armchair and zigzag graphyne nanoribbons by using the nonequilibrium molecular dynamics method. The results show that a strong orientation dependence of the thermal conductivity is observed. The thermal conductivity in the armchair graphyne nanoribbon is larger than that in the zigzag graphyne nanoribbon with the same width and length at room temperature. Furthermore, the orientation dependence is increased when the width of the graphyne nanoribbons decreases. We disclose the underlying mechanism for this intrinsic orientation dependence to be the more phonon transport channels and higher phonon velocity in armchair graphyne nanoribbon throughout the overall frequency range. [ABSTRACT FROM AUTHOR]

By combining the density functional theory with the Boltzmann transport equation, thermoelectric properties of graphphenyl-based materials are investigated. The results show that anisotropic thermoelectric properties can be realized by breaking symmetry and twisting the phenyl ring. The ZT values reach 1.4 in both p- and n-type thermoelectric materials at room temperature. In addition, the thermoelectric properties of these materials can be further promoted by rotating the phenyl ring. These results demonstrate that these materials have excellent thermoelectric performance, two orders of magnitude greater than that of graphene, and have a wide range of suitable working temperatures. This work provides a way to optimize the thermoelectric performance of two-dimensional conjugated organic radical frameworks and provides theoretical support for the design of electrodes and thermoelectric components made of this organic material. [ABSTRACT FROM AUTHOR]

Aided by density functional theory with nonequilibrium Green's functions simulations, the thermoelectric (TE) properties of nanoporous carbon nanotube junctions formed by covalently binding carbon nanotubes via benzene bridges with either meta‐ or para‐connections are investigated. The results show that the TE performances of meta‐connected nanoporous carbon nanotube junctions are significantly improved due to the influence of destructive quantum interference (DQI) effect. Moreover, the TE properties of meta‐connected carbon nanotube junctions can be further improved by substitution of nitrogen atom and gate voltage. The reason is that the quantum interference patterns can be transformed from DQI to constructive quantum interference (or Fano resonance). The theoretical analysis shows that the TE figure of merit (ZT) for meta‐connected carbon nanotube junctions at room temperature is close to 0.5 near the Fermi level, ≈20 times higher than that of the perfect carbon nanotube junction. These results reveal that quantum interference effect can indeed be used to enhance the TE performance of molecular junctions. [ABSTRACT FROM AUTHOR]

Abstract: We investigate the phonon thermal transport properties in InAs nanowires with different size and growth directions by using nonequilibrium molecular dynamics methods. The results show a remarkable anisotropy for the thermal conductivity in InAs nanowire. It is found that the thermal conductivity along [110] growth direction is about three times larger than that along [100] or [111] direction. With the increase of temperature, the thermal conductivity along [110] direction decreases significantly. However, the thermal conductivity along other two directions is not sensitive to temperature. Moreover, we find a crossover from ballistic to ballistic-diffusive thermal transport for a certain length of InAs nanowire. A brief physical analysis of these results is given. It is suggested that the anisotropy of thermal conductivity is common for nanowires with zinc blende structures. [Copyright &y& Elsevier]

Highlights: [•] Electronic transport in single phthalocyanine-based molecules device are studied. [•] Perfect spin filtering can be realized at a wide bias voltage region. [•] Giant magnetoresistance can be observed. [ABSTRACT FROM AUTHOR]

Generating and manipulating valley polarization in a controlled method is significant. The inherently broken centrosymmetry of the buckled honeycomb structures gives it both ferroelectricity and valley degree of freedom, which provides an opportunity to realize electrically controlled valley polarization. In the first step, we explored the origin of buckling. The hexagonal structure is polar due to buckling of the surface, but the degree of buckling and the energy barrier to switching electric polarization are determined not solely by the chemical composition. We combined the electronegativity difference, bond length and the distribution of charge density to describe quantificationally the polarity of chemical bonds. It shows the characteristics of relatively long bond-length but relatively small electronegativity-difference. For exploring the ferroelectricity of buckling structures and the behavior of ferroelectric (FE) control of the valley degree of freedom, the β -GaP is used as a model system to elucidate the strain effect on FE behavior and the magnetic proximity effect on the polarization and switching of valley. We found that the spontaneous polarization is positively correlated with the electronegativity difference within a certain range, and the compression strain can effectively manipulate spontaneous polarization and switch barrier. A combination of the magnetic proximity effect and the inversion of electric polarization can generate and switch valley polarization effectively. [ABSTRACT FROM AUTHOR]

Abstract: Electronic and magnetic properties of half-bare zigzag silicon carbon nanoribbons (ZSiCNRs) have been studied by using HSE06 hybrid function. The calculation results show that the ZSiCNRs with bare Si edge and terminated C edge are metal with magnetic moments per supercell. While the half-bare ZSiCNRs with bare C edge are small band gap semiconductor with magnetic moments per supercell. Stable magnetism of the half-bare ZSiCNRs can be demonstrated by the total energy calculations of different spin configurations. It is found that the magnetic coupling of half-bare ZSiCNRs depends on the bare edge atoms, regardless of the terminated atoms (H or F). Our results indicate that the half-bare ZSiCNRs with turnable electronic and magnetic properties have potential applications in spintronic nanodevices. [Copyright &y& Elsevier]

Since the fixed ejector cannot adjust the optimum high-side pressure, the adjustable ejector is designed and built based on a transcritical CO2 heat pump system model results. The adjustable ejector is subjected to electrical pulses through the stepper motor which drives needle forward or backward movement to change the nozzle throat area for the optimum high-side pressure. Experimental investigation of the transcritical CO2 heat pump cycle with adjustable ejector is presented. The effects of the high-side pressure on the system performance are analyzed. A control strategy for maximum COP h is developed by correlating the CO2 pressure and temperature at the gas cooler exit, yielding the ejector optimum high-side pressure control equation. Experiment results show that there exist maximum values for heating performance coefficient and heat capacity with increasing high-side pressure. The increased high-side pressure has a positive effect on the system performance and outweighs lower ejector efficiencies. The ejector efficiency is mainly distributed within range of 20%–30%. [ABSTRACT FROM AUTHOR]

By using the nonequilibrium Green's function and the Landauer transport theory, nonlinear phonon properties in asymmetric graphene-based three terminal junctions (AGTTJs) are investigated. Results show that AGTTJs exhibit pronounced nonlinear thermal rectifying behaviors, and the efficiency is efficiently tuned by increasing the asymmetric degree between the left and right terminals or modulating the central probe. The thermal rectifying mechanism is analytically explained by the schematic diagram. It is suggested that AGTTJs may be served as a good ballistic thermal rectifier. [ABSTRACT FROM AUTHOR]

We compare the thermal conductance of SH mode and mixing mode of acoustic phonons in a double T-shaped quantum waveguide at low enough temperatures by using the scattering-matrix method, and analyze the influence from mode conversion. Our results show that the small changes of the geometric parameters can induce different variation on the thermal conductivity, where the effect of the stub height of SH wave is the strongest. Moreover, the mode conversion plays an important role on the thermal conductivity, especially at the higher temperatures, and the coupling effect between two stubs at mixing mode is larger than that at single SH mode. [ABSTRACT FROM AUTHOR]

Abstract: Using nonequilibrium Greenʼs functions in combination with the density functional theory, the spin-dependent electronic transport properties on V-shaped notched zigzag-edged graphene nanoribbons junctions have been calculated. The results show that the electronic transport properties are strongly depending on the type of notch and the symmetry of ribbon. The spin-filter phenomenon and negative differential resistance behaviors can be observed. A physical analysis of these results is given. [Copyright &y& Elsevier]

Thermal metamaterials can effectively manipulate heat flux to achieve different thermal management functions, such as thermal cloak, concentrator, and rotator. To date, most of these metamaterials are based on macroscopic compound structures, such as metal/polymer. Herein, the concept of thermal metamaterials is extended to two‐dimensional (2D) graphene‐based systems because of their fast response speeds, in contrast to traditional three‐dimensional metamaterials. Three thermal metamaterials with heterogeneous thermal parameters are constructed using nano‐holed graphene, and some extraordinary thermal phenomena, such as effective shielding, accumulation and rotation of heat flux, are observed due to the significant anisotropic thermal conductivity of these 2D systems. Moreover, these thermal phenomena are insensitive to external disturbances. For designing thermal metamaterials, this study provides a novel approach, which can be applied to other 2D thermal functional materials. [ABSTRACT FROM AUTHOR]

We investigate ballistic thermal transport contributed by the in-plane waves in a quantum wire modulated with an acoustic nanocavity. Here, the numerical calculations for two transmitted components (P wave and SV wave) are made to consider the mode conversion. Results show for the P wave component that the universal quantum thermal conductance can be observed in spite of structural details in the low temperature limit, and then the thermal conductance decreases with increasing temperature. However, for the SV wave component, the thermal conductance increases from zero monotonically with temperature. These indicate the mode conversion is directly proportional to the temperature. In addition, it is found that the mode conversion sensitively depend upon the incident frequency, the index of the modes as well as structural parameters. A brief analysis of these results is given. [ABSTRACT FROM AUTHOR]

The demands for waste heat energy recovery from industrial production, solar energy, and electronic devices have resulted in increasing attention being focused on thermoelectric materials. Over the past two decades, significant progress is achieved in inorganic thermoelectric materials. In addition, with the proliferation of wireless mobile devices, economical, efficient, lightweight, and bio‐friendly organic thermoelectric (OTE) materials have gradually become promising candidates for thermoelectric devices used in room‐temperature environments. With the development of experimental measurement techniques, the manufacturing for nanoscale thermoelectric devices has become possible. A large number of studies have demonstrated the excellent performance of nanoscale thermoelectric devices, and further improvement of their thermoelectric conversion efficiency is expected to have a significant impact on global energy consumption. Here, the development of experimental measurement methods, theoretical models, and performance modulation for nanoscale OTE materials are summarized. Suggestions and prospects for the future development of these devices are also provided. [ABSTRACT FROM AUTHOR]

Abstract Fructus Psoraleae (FP) causes cholestatic liver injury; however, its main toxic constituents that are responsible for causing hepatotoxicity remained undetermined in previous studies. In the present study, psoralen and isopsoralen, the two main constituents of FP, were administered orally to rats (80 and 40 mg/kg, respectively) and mice (320 and 160 mg/kg, respectively) for 28 days, followed by biochemical and histopathological examinations to evaluate their hepatotoxicity. The results showed that psoralen and isopsoralen could induce the toxic reactions of liver and other organs in rats, while mice were not sensitive to these two compounds. Furthermore, the corresponding results indicated that administration of psoralen and isopsoralen repressed the expression of CYP7A1, BSEP, MRP2 and SULT2A1 and increased the expression of FXR and MRP3 in the rat liver. In summary, the toxic reactions of psoralen and isopsoralen are different in different species. In this study, multiple organ toxicity, such as cholestatic liver injury, occurs in rats, but not in mice. Psoralen and isopsoralen are the two main toxic constituents of FP. In addition, psoralen and isopsoralen cause liver injury, possibly through inhibiting bile acid excretion in the liver, leading to the accumulation of toxin in hepatocytes. Highlights • Psoralen and isopsoralen cause liver injury in rats but are not sensitive in mice. • Psoralen and isopsoralen cause adrenal, seminal vesicle and prostate damage in rats. • Psoralen and isopsoralen inhibit bile acid excretion in the livers of rats. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • In MoS 2 , Al and Sb can play as good p-type dopants. • In WS 2 , Al dopes on cation site can perform as a good acceptor. • Halogen elements dope on the Te site in MoTe 2 are suitable n-type dopants; As and Sb are appropriate for p-type doping. • In WTe 2 , F is a suitable n-type dopant; P, As, Sb and Al are promising acceptors. Abstract Dopability in semiconductors plays a crucial role in device performance. Using the first-principles density-functional theory calculations, we investigate systematically the doping properties of layered MX 2 (M = Mo, W; X = S, Te) by replacing M or X with the groups III, V and VII elements. It is found that the defect B M is hard to form in MX 2 due to the large formation energy originating from the crystal distortion, while Al M is easy to realize compared to the former. In MoS 2 , WS 2 and MoTe 2 , Al is the most desirable p-type dopant under anion-rich conditions among the group III components. With respect to the doping of the group V elements, it is found that the substitutions on the cation sites have deeper defect levels than those on the anion sites. As Te and Sb Te in MoTe 2 and WTe 2 are trend to form shallow acceptors under cation-rich conditions, indicating high hole-concentrations for p-type doping, whereas Sb S in MoS 2 and P Te in WTe 2 are shown to be good p-type candidates under cation-rich conditions. In despite of that the substitutions of group VII on X site have low formation energies, the transition energies are too high to achieve n-type MoS 2 and WS 2. Nevertheless, for MoTe 2 , the substitutions with the group VII elements on the anion sites are suitable for n-type doping on account of the shallow donor levels and low formation energies under Mo-rich condition. As to WTe 2 , F is the only potential donor due to the shallow transition energy of F Te. Our findings of filtering out unfavorable and identifying favorable dopants in MX 2 are very valuable for experimental implementations. [ABSTRACT FROM AUTHOR]

Abstract Penta-hexa-graphene (PHG) is the name given to a novel puckered monolayer of carbon atoms tightly packed into an inerratic mixing pentagonal and hexagonal network. Theoretically, it exhibits excellent electronic properties and can be rolled into penta-hexa-graphene nanotubes (PHGNTs). By using first-principles combined with density functional theory, the PHGNTs with two types of chirality and different diameters were studied. Studies show that not only the nanotubes have intrinsic magnetic properties, but also the magnetic ground state changes with the tube diameter. Interestingly, the nanotubes exhibit semiconducting properties that do not vary with chirality in the antiferromagnetic (AFM) state. And in the ferromagnetic (FM) state, the materials realize the transitions from metal to spin gapless semiconductors (SGS), and to semiconductor with the change of tube diameter. Furthermore, first-principles calculation shows that PHGNTs exhibit diverse electronic properties when the external electrical field is applied, ranging not only from semiconductor to SGS and to metal, but also from semiconductor to half-metal and to metal. Our simulations have an impact on their possible applications in spintronic devices. Graphical abstract Image Highlights • The electronic and magnetic properties of the penta-hexa-graphene nanotubes (PHGNTs) were studied. • The PHGNTs have intrinsic magnetic properties, and the magnetic ground state changes with the tube diameter. • All of the stable PHGNTs are semiconducting regardless of chirality in the AFM state. • In FM state, the PHGNTs transit from metals to spin gapless semiconductors, and to semiconductors with increasing diameter. [ABSTRACT FROM AUTHOR]

Gastric cancer (GC) is one of the most common malignancies in the world. It is essential to develop novel targets and therapeutic approaches for GC, which requires identification of novel functional molecules. WW-domain containing transcription regulator 1 (WWTR1) may activate many transcriptional factors and exhibit an important role in the development of various tissues in mammals. The results of the present study demonstrated that mRNA and protein levels of WWTR1 are increased in GC tissues and cell lines. The SGC7901 cell line was selected to perform RNA interference (RNAi) targeting WWTR1, and for subsequent study. Compared with control groups (cells without any treatment) and mock groups (cells treated with nonspecific siRNA), cell proliferation of siWWTR1 cells (cells treated with WWTR1 siRNA) was detected using a Cell Counting Kit-8 assay at 12, 24 and 48 h, and decreased in a time-dependent manner. Cell cycle and apoptosis status were determined by flow cytometry, and it was demonstrated that G1/S transition was blocked in the cell cycle and apoptosis promoted in siWWTR1 cells, compared with control and mock cells. Reverse transcription-quantitative polymerase chain reaction and western blotting were performed to detect the mRNA and protein levels of cell cycle and apoptosis-associated factors. The expression of Cyclin D1, cancer Myc and B cell lymphoma/leukemia-2 (Bcl-2) decreased and Bcl-2 associated X protein increased significantly in siWWRT1 cells, at the mRNA and protein level, compared with control and mock cells. With the exception of the Hippo pathway, siWWTR1 regulated downstream factors, including mothers against decapentaplegic homolog family member 3 (SMAD3) and inhibitor of DNA binding 1, HLH protein (ID1), HLH protein in the transforming growth factor (TGF)-β pathway. The expression of asparagine synthetase was decreased whereas ID1, SMAD3 (proteins that participate in intracellular TGF-β transduction) and betacellulin increased notably in siWWRT1 cells. In conclusion, WWTR1 promotes cell proliferation and inhibits apoptosis of GC cells by regulating cell cycle/apoptosis-associated factors, and effectors in the TGF-β pathway. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new strategy to independently manipulate the phonon thermal conductivity of two-dimensional superlattice materials. • The strategy is realized by structure defects obtained by changing the superlattice arrangement. • The independence of this manipulation method makes it promising to combine with other methods to further regulate thermoelectric properties in such a system further. Effective regulation of phonon thermal conductivity is crucial for the understanding of phonon transmission and improving thermoelectric (TE) performance. Using density functional theory (DFT) combined with the non-equilibrium Green's function (NEGF) method, we investigated the effect of phonon localization induced by aperiodic superlattices on the TE transport properties of superlattices based on monolayer MoS 2 -MoSe 2. The results show that the structural defects obtained by changing the superlattice arrangement can effectively modulate the phonon thermal conductivity independently. In addition, the TE properties of the superlattices increase with temperature and central region length. The maximum value of the TE figure of merit of the aperiodic superlattice can reach 1.38 at 500 K. This implies a new potential strategy for tuning the TE performance of devices by exploiting the arrangements of the aperiodic superlattice. [ABSTRACT FROM AUTHOR]

Thermal transport across graphene/hexagonal boron nitride ( h -BN) nanoribbon interface is investigated using nonequilibrium molecular dynamics method. It is found that the heat current runs preferentially from the h -BN to graphene domain, which demonstrates pronounced thermal rectification behavior in this heterostructure. The observed phenomena can be attributed to the resonance effect between out-of-plane phonon modes of the graphene and h -BN domains in the low frequency region. In addition, we demonstrate that the optimum conditions for thermal rectification include low temperature, large temperature bias, short sample length and small interface densities. More interestingly, an unexpected negative differential thermal resistance (NDTR) behavior is also found at graphene/ h -BN (CBN) nanoribbon interface with special edge geometry. Phonon spectra analysis reveals that the transverse acoustic wave plays an important role for the heat transfer at such interface. [ABSTRACT FROM AUTHOR]

To analyze the thermal transport properties in core-shell nanowires, we calculate systematically the distributions of heat flux in InAs/GaAs and GaAs/InAs core-shell nanowires by using nonequilibrium molecular dynamics simulations. The results show that for InAs/GaAs core-shell nanowires, the heat current tends to transport in the shell, while for GaAs/InAs core-shell nanowires the heat current tends to transport through the core. Moreover, a simple equation is presented to describe the relationship of the thermal conductance among the core, the tubular shell, and core-shell nanowire. It is suggested that the core-shell nanowires can be served as heat cable. [ABSTRACT FROM AUTHOR]

Abstract: By using nonequilibrium Green’s functions in combination with the density-functional theory, we investigate the electronic transport properties of the molecular device constructed by a single 4,4-(ethene-1,2-diyl) dibenzoic acid sandwiched between carbon nanotube electrodes. The results show that an obvious reversible switching behavior can be observed when the molecular structure changes between E isomerization and Z isomerization by ultraviolet irradiation or visible irradiation. More importantly, the switching ratio can reach to a maximum (about 7000) at 0.28V and then decrease gradually to a minimum at 0.48V. It is suggested that the controllable switching behavior is very useful for the design of functional molecular devices. [Copyright &y& Elsevier]

Abstract: Applying nonequilibrium Green''s functions in combination with the first-principles density-functional theory, we investigate electronic transport properties of an all-carbon molecular device consisting of one phenalenyl molecule and two zigzag graphene nanoribbons. The results show that the electronic transport properties are strongly dependent on the contact geometry and device''s currents can drop obviously when the connect sites change from second-nearest sites from the central atom of the molecule (S site) to third-nearest sites from the central atom of the molecule (T site). More importantly, the negative differential resistance behavior is only observed on the negative bias region when the molecule connects the graphene nanoribbons through two T sites. [Copyright &y& Elsevier]