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In kinesin's mechanochemical cycle, ATP's binding to the nucleotide-free leading head is exquisitely gated so that futile hydrolysis is effectively avoided. Experiments show that, when both kinesin heads bind to a microtubule, ATP cannot bind to kinesin's leading head when the neck linker (NL) of this head has a backward orientation. How NL's backward orientation is maintained needs understanding on a structural basis. By using steered molecular dynamics and mutation simulations, we investigate the backward-pointing conformation of the leading head's NL under different inter-head tensions. We find that the NL cannot keep in a strict backward orientation solely by the inter-head tension. LYS325 (amino acid sequence in 2KIN) has an assistant locking function which locks the NL and β0 to the β-domain. This locking function has an enhanced positive cooperation with the inter-head tension. When the inter-head tension is weakened, this locking function can be broken, resulting in a loose backward orientation of the NL. The difference between the strict and loose backward orientation of the NL might be a crucial factor in the gating mechanism. These results are consistent with relevant experiments and proposals. [ABSTRACT FROM AUTHOR]

In this paper, based on the equivalent single diode circuit model of the solar cell, an equivalent circuit diagram for two serial solar cells is drawn. Its equations of current and voltage are derived from Kirchhoff's current and voltage law. First, parameters are obtained from the I—V (current—voltage) curves for typical monocrystalline silicon solar cells (125 mm × 125 mm). Then, by regarding photo-generated current, shunt resistance, serial resistance of the first solar cell, and resistance load as the variables. The properties of shunt currents (Ish1 and Ish2), diode currents (ID1 and ID2), and load current (IL) for the whole two serial solar cells are numerically analyzed in these four cases for the first time, and the corresponding physical explanations are made. We find that these parameters have different influences on the internal currents of solar cells. Our results will provide a reference for developing higher efficiency solar cell module and contribute to the better understanding of the reason of efficiency loss of solar cell module. [ABSTRACT FROM AUTHOR]

Textured silicon (Si) substrates decorated with regular microscale square pillar arrays of nearly the same side length, height, but different intervals are fabricated by inductively coupled plasma, and then silanized by self-assembly octadecyl-trichlorosilane (OTS) film. The systematic water contact angle (CA) measurements and micro/nanoscale hierarchical rough structure models are used to analyze the wetting behaviors of original and silanized textured Si substrates each as a function of pillar interval-to-width ratio. On the original textured Si substrate with hydrophilic pillars, the water droplet possesses a larger apparent CAs (> 90°) and contact angle hysteresis (CAH), induced by the hierarchical roughness of microscale pillar arrays and nanoscale pit-like roughness. However, the silanized textured substrate shows superhydrophobicity induced by the low free energy OTS overcoat and the hierarchical roughness of microscale pillar arrays, and nanoscale island-like roughness. The largest apparent CA on the superhydrophobic surface is 169.8°. In addition, the wetting transition of a gently deposited water droplet is observed on the original textured substrate with pillar interval-to-width ratio increasing. Furthermore, the wetting state transition is analyzed by thermodynamic approach with the consideration of the CAH effect. The results indicate that the wetting state changed from a Cassie state to a pseudo-Wenzel during the transition. [ABSTRACT FROM AUTHOR]

In this paper, the electro—magnetic control of a cylinder wake in shear flow is investigated numerically. The effects of the shear rate and Lorentz force on the cylinder wake, the distribution of hydrodynamic force, and the drag/lift phase diagram are discussed in detail. It is revealed that Lorentz force can be classified into the field Lorentz force and the wall Lorentz force and they affect the drag and lift forces independently. The drag/lift phase diagram with a shape of “8" consists of two closed curves, which correspond to the halves of the shedding cycle dominated by the upper and lower vortices respectively. The free stream shear (K > 0) induces the diagram to move downward and leftward, so that the average lift force directs toward the downside. With the upper Lorentz force, the diagram moves downwards and to the right by the field Lorentz force, thus resulting in the drag increase and the lift reduction, whereas it moves upward and to the left by the wall Lorentz force, leading to the drag reduction and the lift increase. Finally the diagram is dominated by the wall Lorentz force, thus moving upward and leftward. Therefore the upper Lorentz force, which enhances the lift force, can be used to overcome the lift loss due to the free stream shear, which is also obtained in the experiment. [ABSTRACT FROM AUTHOR]

Embedded-atom method (EAM) potentials are used to investigate the effects of alloying (e.g. 3d-metals) on the trends of elastic and thermodynamic properties for CuPd3 alloy. Our calculated lattice parameter, cohesive energy, and elastic constants of CuPd3 are consistent with the available experimental and theoretical data. The results of elastic constants indicate that all these alloys are mechanically stable. Further mechanical behavior analysis shows that the additions of Cr, Fe, Co, and Ni could improve the hardness of CuPd3 while V could well increase its ductility. Moreover, in order to evaluate the thermodynamic contribution of 3d-metals, the Debye temperature, phonon density of states, and vibrational entropy for CuMPd6 alloy are also investigated. [ABSTRACT FROM AUTHOR]

Open clusters (OCs) are usually young and suitable for studying the formation and evolution of planetary systems. So far, only four planets have been found with radial velocity measurements in OCs. Meanwhile, a lot of freefloating planets (FFPs) have been detected. We utilize N-body simulations to investigate the evolution and final configurations of multi-planetary systems in very young open clusters with an age <10 Myr. After an evolution of 10 Myr, 61%-72% of the planets remain bounded and more than 55% of the planetary systems will maintain their initial orbital configurations. For systems with one planet ejected, more than 25% of them have the surviving planets in misaligned orbits. In the clusters, the fraction of planetary systems with misalignment is >6%, and only 1% have planets in retrograde orbits. We also obtain a positive correlation between the survival planet number and the distance from the cluster center r: planetary systems with a larger r tend to be more stable. Moreover, stars with a mass >2.5 M⊙ are likely unstable and lose their planets. These results are roughly consistent with current observations. Planetary systems in binaries are less stable and we achieve a rough criterion: most of the binary systems with ab(1 - eb2) >100 AU can retain all the initial planets. Finally, 80% of the FFPs are ejected out of the clusters, while the rest (~20%) still stay in host clusters and most of them are concentrated in the center (<2 pc). [ABSTRACT FROM AUTHOR]

In Besocke-style scanners, a theoretical model with stick-slip sliding boundary conditions is presented by Timoshenko beam theory combined with the harmonic-balance method. The flexural vibration characteristics of the piezo-tubes induced by the stick-slip motions of the ball on the rail are investigated. The results show that the flexural vibrations essentially depend on the ratio of the ball-rail lateral friction threshold to the product of the ball-rail lateral contact stiffness and the vibration amplitude of the ball. When the ratio changes from zero to one, the lateral friction applied to the ball induces complex flexural vibrations. The vibrations can be regulated by adjusting an input electric signal to change the vibration amplitude of the ball, or using an external electro-magnetic force to change the preload of the ball-rail interaction, or changing the radius of the ball. Thus, the adverse vibrations of Besocke-style scanner can be eliminated to improve the spatial resolution of the atomic structure in scanning probe microscopes. [ABSTRACT FROM AUTHOR]

To investigate the late effects of radiation on child-bearing women, a follow-up study was performed on a 39-year-old survivor 16 years after a 60Co radiation accident. The woman, Fang, was 19 weeks pregnant at the time of exposure. Physical examinations, a full range of clinical laboratory and imaging tests, as well as cytogenetic analyses were conducted to evaluate Fang's current health conditions. Fang shows the appearance of premature ageing and has a decreased menstrual period. Laboratory studies and imaging tests suggest nodular goitre disease and osteoporosis. Otherwise, no apparent abnormalities were found in the major organs. No malignant tumours were detected by either tumour markers or imaging tests. However, the existence of chromosome aberrations warrants long-term follow-up for tumour incidence in the future. Fang became pregnant 8 years after the accident, but suffered a miscarriage due to the death of the foetus at 6 months into the pregnancy. In conclusion, our findings suggest that the intrauterine death of the foetus might be associated with the previous exposure. There is no evidence of malignant tumours as of the date of the follow-up study. Non-cancerous diseases, i.e. thyroid disease and osteoporosis, which may be related to radiation exposure, are the major manifestations of the long-term effects of the accident. [ABSTRACT FROM AUTHOR]

A follow-up study of the late effects of intrauterine exposure to irradiation has been made on a 16-year-old girl whose mother was exposed to external 60Co irradiation during the Xinzhou radiation accident 16 years previously. The outcomes of the general medical examinations, conventional chromosome aberration analyses and fluorescence in situ hybridisation (FISH) are presented and the China-revised Wechsler Intelligence Scale for Children (C_WISC) was used to identify her IQ level, which was well below normal for her age. The biological dose of the radiation to which she was exposed when she was in her mother's uterus was inferred to be 1.85 Gy. Although there is no evidence of any other developmental changes or tumour induction at this stage in her life, the child's total intelligence level does appear to have been affected. [ABSTRACT FROM AUTHOR]

The sublimation vapour transport method is a widely used technique for the production of optoelectronic materials, such as aluminium nitride (AIN). One-step reaction with two vapour species, i.e. aluminium (Al) vapour and nitrogen (N2) gas, is widely assumed and diffusion-controlled growth mechanism with thermodynamic equilibrium calculations is usually used in the open literature. In this paper, the diffusion transport model, aluminium vapour dominated model and nitrogen dominated model are summarized/proposed. The operating conditions in which different models can be employed are identified. The predicted growth rates using different models are compared with each other and with the experimental data. A kinetic-controlled growth model is also developed considering surface kinetics. Furthermore, an anisotropic sublimation growth model is proposed for the first time, in which aluminium vapour or nitrogen dominated model is applied along the c-axis and the kinetic model is employed perpendicular to the c-axis. The model is used to predict the transition temperature at which the morphology of the crystal changes. [ABSTRACT FROM AUTHOR]

Patterned sapphire substrates (PSS) have been widely used to enhance the light output power of light emitting diodes (LEDs).The morphology and shape of the PSS have a great influence on the performance of the LEDs. In this work, commercial PSS is reprocessed utilizing selective-area wet etching approach, in which selective-area SiO2 mask is fabricated through partial exposure lithography instead of conventional overlay lithography. By precisely controlling the exposure time, the etching process can be controlled to take place only on the top of the PSS. Various surface morphology including pyramid, volcano, clover and closed-packaged inverted pyramid can be attained from the evolution of the selective-area etched PSS. The mechanism of the selective-area etched sapphire is correlated to the slant angle of the pattern surface and the SiO2 mask pattern. [ABSTRACT FROM AUTHOR]

Polytriazine imide (PTI), a triazine-based carbon nitride has a wider band gap and more positive conduction band (CB) potential compared to those of graphitic carbon nitride (g-C3N4). Therefore, it is highly desired to develop an effective strategy to optimize the band structure of PTI for the enhancement of the photocatalytic performance, especially upshift the conductive band potential. Here, a ternary C-PTI/ZnO (CPZ) photocatalyst was developed via a simple one-step molten salt method. In the obtained CPZ sample, the carbon ring in-plane connects to the triazine ring, leading to the formation of C-PTI nanosheets. The carbon ring incorporation not only efficiently narrows the band gap of PTI, but also shifts its conduction band potential negatively and accelerates the photogenerated electron transport. In addition, ZnO nanoparticles are well dispersed on the C-PTI nanosheets, further promoting the charge carriers transfer and separation. As a result, the CPZ sample presents a photocatalytic H2 evolution rate up to 52 μmol h−1 under visible light, which is 60 and 179 times higher than that of C-PTI and PTI, respectively. [ABSTRACT FROM AUTHOR]

Using optical pump-terahertz (THz) time-domain spectroscopy measurements along with ab initio density functional theory (DFT) calculations, we studied the effect of 3,9-bis(2-methylene-(3-(1, 1-dicyanomethylene)-5-methylindanone)-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno [1,2-b:5,6-b′]-dithiophene (IT-M) molecules on the ultrafast dynamics and photoconductivity of the active layers of ternary organic solar cells (OSCs), which are composed by the conjugated polymer donor and fullerene derivative acceptor. The THz photoconductivity measurements show that the introduction of IT-M molecule increases the photoconductivity of the ternary OSC and the maximum value of photoconductivity is obtained in the sample with IT-M weight ratio of 15%. To reveal the mechanism of IT-M doping on the photoconductivity of OSC material, ab initio DFT calculations were performed to identify the band structures of the ternary OSC heterostructures. Resonant charge transfers induced by the band alignment of IT-M with the conjugated polymer donor and fullerene derivative acceptor, which lead to an increase of photoconductivity with a reduction of electron–hole recombination rate, were obtained from DFT calculations. In addition to the resonant charge transfer process, defect scattering induced by the doping of IT-M molecules leads to a reduction of photoconductivity. By competing these two effects, maximum photoconductivity of ternary OSC materials is obtained with IT-M weight ratio of 15%. Moreover, the charge carrier densities and scattering times of ternary OSC materials were derived from the measured THz photoconductivity via the classical Drude–Smith model. With these material properties, we identified that the maximum value of photoconductivity in OSC material with IT-M weight ratio of 15% is induced by its long scattering time instead of high carrier density. [ABSTRACT FROM AUTHOR]

Pedestrian evacuation is actually a process of behavioral evolution. Interaction behaviors between pedestrians affect not only the evolution of their cooperation strategy, but also their evacuation paths-scheduling and dynamics features. The existence of interaction behaviors and cooperation evolution is therefore critical for pedestrian evacuation. To address this issue, an extended cellular automaton (CA) evacuation model considering the effects of interaction behaviors and cooperation evolution is proposed here. The influence mechanism of the environment factor and interaction behaviors between neighbors on the decision- making of one pedestrian to path scheduling is focused. Average payoffs interacting with neighbors are used to represent the competitive ability of one pedestrian, aiming to solve the conflicts when more than one pedestrian competes for the same position based on a new method. Influences of interaction behaviors, the panic degree and the conflict cost on the evacuation dynamics and cooperation evolution of pedestrians are discussed. Simulation results of the room evacuation show that the interaction behaviors between pedestrians to a certain extent are beneficial to the evacuation efficiency and the formation of cooperation behaviors as well. The increase of conflict cost prolongs the evacuation time. Panic emotions of pedestrians are bad for cooperation behaviors of the crowd and have complex effects on evacuation time. A new self-organization effect is also presented. [ABSTRACT FROM AUTHOR]

Negative refraction usually demands complex structure engineering while it is very natural for massless Dirac fermions (MDFs) across the p–n junction (PNJ), this leads to Dirac electron optics. The emergent Dirac materials may exhibit hitherto unidentified phenomenon due to their nontrivial band structures in contrast to the isotropic MDFs in graphene. Here, as a specific example, we explore the negative refraction induced caustics and Veselago focusing of tilted MDFs across 8-Pmmn borophene PNJs. To this aim, we develop a technique to effectively construct the electronic Green’s function (GF) in PNJs with arbitrary junction directions. Based on analytical discussions and numerical calculations, we demonstrate the strong dependence of interference pattern on the junction direction. As the junction direction perpendicular to the tilt direction, Veselago focusing or normal caustics (similar to that in graphene) appears resting on the doping configuration of the PNJs, otherwise anomalous caustics (different from that in graphene) occurs which is manipulated by the junction direction and the doping configuration. Finally, the developed GF technique is generally promising to uncover the unique transport of emergent MDFs, and the discovered anomalous caustics makes tilted MDFs potential applications in Dirac electron optics. [ABSTRACT FROM AUTHOR]

Magnetosheath properties, particularly those related to magnetopause magnetic reconnection (MR), are investigated in this study. (1) Asymmetries are found to exist in the distributions of plasma and magnetic field parameters in the magnetosheath. These asymmetries are related to the interplanetary magnetic field (IMF) orientation, and they are produced either on the bow shock or inside the magnetosheath. Thus, one must be very cautious in directly using the upstream solar wind and IMF properties as the magnetopause MR initiation conditions, since the magnetosheath parameters are not the same everywhere. (2) A unique method is introduced to estimate how much IMF magnetic flux passes through the magnetosphere via MR on either the low-latitude or the high-latitude magnetopause. This flux mainly varies with three independent parameters: the IMF clock angle θCL, the magnetosheath plasma β, and the solar wind sound Mach number MS. Surprisingly, the magnetic fluxes passing through the magnetosphere are comparable under the southward and northward IMF conditions. (3) The dipole tilt angle, the property from the inside of the magnetosphere, also controls the magnetosheath parameters. As the Earth’s dipole tilt angle varies, the plasma pressure ridge shifts its location but remains near the magnetic equator. The stagnation point of the magnetosheath flow on the magnetopause, however, remains at the subsolar point no matter how large the dipole tilt angle is. These behaviors may be determinative of the locations of MR and the generation of flux transfer events on the magnetopause. [ABSTRACT FROM AUTHOR]

Memory can remarkably modify the collective behavior of active particles. We show that, in a micellar fluid, Quincke particles driven by a square-wave electric field exhibit a frequency-dependent memory. Upon increasing the frequency, a memory of directions emerges, whereas the activity of particles decreases. As the activity is dominated by interaction, Quincke particles aggregate and form dense clusters, in which the memory of the direction is further enhanced due to the stronger electric interactions. The density-dependent memory and activity result in dynamic heterogeneity in flocking and offer a new opportunity for research of collective motions. [ABSTRACT FROM AUTHOR]

A method of combining Green’s function retrieval theory and ultrasonic array imaging using Lamb waves is presented to solve near filed defects in thin aluminum plates. The defects are close to the ultrasonic phased array and satisfy the near field calculation formula. Near field acoustic information of defects is obscured by the nonlinear effects of initial wave signal in a directly acquired response using the full matrix capture mode. A reconstructed full matrix of inter-element responses is produced from cross-correlation of directly received ultrasonic signals between sensor pairs. This new matrix eliminates the nonlinear interference and restores the near-field defect information. The topological imaging method that was developed in recent ultrasonic inspection is used for displaying the scatterers. The experiments are conducted on both thin aluminum plates containing two and four defects, respectively. The results show that these defects are clearly identified when using a reconstructed full matrix. The spatial resolution is equal to about one wavelength of the selectively excited mode and the identifiable defect is about one fifth of the wavelength. However, in a conventional directly captured image, the images of defects overlap together and cannot be distinguished. The proposed method reduces the background noise and allows for effective topological imaging of near field defects. [ABSTRACT FROM AUTHOR]

Based on the Fourier–Chebyshev spectral method, the control of turbulent channel flow by space-dependent electromagnetic force and the mechanism of drag reduction are investigated with direct numerical simulation (DNS) methods for different Reynolds numbers. A formula is derived to express the relation between fluctuating velocities and the friction drag coefficient. With the application of electromagnetic force, the in-depth relations among the fluctuating velocities near the wall, Reynolds stress, and the effect of drag reduction for different Reynolds numbers are discussed. The results indicate that the maximum drag reductions can be obtained with an optimal combination of parameters for each case of different Reynolds numbers. The fluctuating velocities along the streamwise and normal directions are suppressed significantly, while the fluctuating velocity along the spanwise direction is enhanced dramatically due to the spanwise electromagnetic force. However, the values of Reynolds stress depend on the fluctuating velocities along the streamwise and normal directions rather than that along the spanwise direction. Therefore, the significant effect of drag reduction is obtained. Moreover, the maximum drag reduction is weakened due to the decay of control effect for fluctuating velocities as the Reynolds number increases. [ABSTRACT FROM AUTHOR]

A Cu2O/TiO2 p-n heterojunction composite was created via a facile, controllable, one-pot hydrothermal method based on cubic Cu2O and TiO2 nanoparticles in the presence of dioctyl sulfosuccinate sodium salt (AOT) surfactant. The TiO2 nanoparticles with an average edge length of ∼10.1 nm were uniformly distributed on the crystal surface of a Cu2O cube {100}. The photocatalytic performance of the composite was effectively tuned by controlling the amount of TiO2. The Cu2O/TiO2 (60 wt%, labeled as CT-60) exhibits the highest enhanced photocatalytic activity in hydrogen production with H2 evolution of 3002.5 μmol g–1. The yield remained around 92.6% after three cycles. Hydrogen production of the CT-60 is 103 and 8.5 fold higher than the cubic Cu2O and TiO2 nanoparticles, respectively. The improvement in photocatalytic performance could be attributed to the formation of p-n heterojunction. Furthermore, the interface effect of Cu2O and TiO2 caused a broader absorbance in the visible-light region and the lower recombination of photogenerated electron–hole pairs. It is believed that the Cu2O/TiO2 p-n heterojunction composites could provide an alternative method to design highly efficient photocatalysts for solar energy. [ABSTRACT FROM AUTHOR]

We report a strong antiferromagnetic (AFM) interlayer coupling in ferromagnetic La0.67Sr0.33MnO3/SrRuO3 (LSMO/SRO) superlattices grown on (111)-oriented SrTiO3 substrate. Unlike the (001) superlattices for which the spin alignment between LSMO and SRO is antiparallel in the in-plane direction and parallel in the out-of-plane direction, the antiparallel alignment is observed along both the in-plane and out-of-plane directions in the present sample. The low temperature hysteresis loop demonstrates two-step magnetic processes, indicating the coexistence of magnetically soft and hard components. Moreover, an inverted hysteresis loop was observed. Exchange bias tuned by the temperature and cooling field was also investigated, and positive as well as negative exchange bias was observed at the same temperature with the variation of the cooling field. A very large exchange field (HEB) was observed and both magnitude and sign of the HEB depend on the cooling field, which can be attributed to an interplay of Zeeman energy and AFM coupling energy at the interfaces. The present work shows the great potential of tuning a spin texture through interfacial engineering for the complex oxides whose spin state is jointly determined by strongly competing mechanisms. [ABSTRACT FROM AUTHOR]

A wool-TiO2 nanoparticle composite material having TiO2 nanoparticles both infiltrated in the matrix between macrofibrils inside cortical cells of wool fibers and grafted on the fiber surface is obtained in this study, and the wool-nanoparticle composite material is found to have highly photocatalytic activities with an extremely narrow band gap of 2.8 eV. The wool fibers are obtained using three successive technical steps: wool fibers are swollen by using lithium bromide, then saturated with tetrabutyl titanate ethanol solution and subsequently treated in boiling water. It was demonstrated that the chemical bonds formed between the as-synthesized TiO2 nanoparticles and the wool fibers swollen by lithium bromide include C−Ti4+(Ti3+), N−Ti4+(Ti3+), O−Ti3+, and S−Ti4+(Ti3+) bonds. The modified wool fibers have shown markedly improved photocatalytic efficiency due to their enhanced visible light absorption capability, which is much better than the (N-doped) TiO2 coated wool fibers. In contrast, TiO2 modified wool fibers swollen by using formic acid have poorer photoactivity, this might be due to the elimination of trivalent titanium between TiO2 nanoparticles and the wool fibers. [ABSTRACT FROM AUTHOR]

Spontaneous alpha oscillations are a ubiquitous phenomenon in the brain and play a key role in neural information processing and various cognitive functions. Jansenʼs neural mass model (NMM) was initially proposed to study the origin of alpha oscillations. Most of previous studies of the spontaneous alpha oscillations in the NMM were conducted using numerical methods. In this study, we aim to propose an analytical approach using the describing function method to elucidate the spontaneous alpha oscillation mechanism in the NMM. First, the sigmoid nonlinear function in the NMM is approximated by its describing function, allowing us to reformulate the NMM and derive its standard form composed of one nonlinear part and one linear part. Second, by conducting a theoretical analysis, we can assess whether or not the spontaneous alpha oscillation would occur in the NMM and, furthermore, accurately determine its amplitude and frequency. The results reveal analytically that the interaction between linearity and nonlinearity of the NMM plays a key role in generating the spontaneous alpha oscillations. Furthermore, strong nonlinearity and large linear strength are required to generate the spontaneous alpha oscillations. [ABSTRACT FROM AUTHOR]

Highly mobile 2-dimensional electron gases (2DEGs) at the (001), (011) and (111)-oriented LaAlO3/SrTiO3 (LAO/STO) interfaces are obtained using spin coating chemical method, which is a gentle technique without plasma bombardment of the pulsed laser deposition. As revealed by x-ray diffraction spectrum and x-ray reflectivity analysis, the LAO over layer is epitaxially grown, and has a uniform thickness of ∼15 nm, ∼20 nm and ∼26 nm for (001), (011) and (111) orientations, respectively. The interfaces are well metallic down to 2 K. The carrier mobilities are ∼28 000 cm2 V−1 s−1, ∼22 000 cm2 V−1 s−1 and ∼8300 cm2 V−1 s−1 at 2 K for the (001), (011) and (111) LAO/STO interfaces, respectively, and ∼8 cm2 V−1 s−1, ∼4 cm2 V−1 s−1 and ∼4 cm2 V−1 s−1 at room temperature. The present work shows that the spin coating chemical method is a feasible approach to get high quality 2DEG at both the polar/non-polar and polar/polar interfaces. [ABSTRACT FROM AUTHOR]

A direct numerical simulation (DNS) is performed to investigate the control effect and mechanism of turbulent channel flow with the distribution of spanwise Lorentz force. A sinusoidal distribution of constant spanwise Lorentz force is selected, of which the control effects, such as flow characters, mean Reynolds stress, and drag reductions, at different parameters of amplitude A and wave number kx are discussed. The results indicate that the control effects vary with the parameter A and kx. With the increase of A, the drag reduction rate Dr first increases and then decreases rapidly at low kx, and slowly at high kx. The low drag reduction (or even drag increase) is due to a weak suppression or even the enhancements of the random velocity fluctuation and mean Reynolds stress. The efficient drag reduction is due to the quasi-streamwise vortex structure induced by Lorentz force, which contributes to suppressing the random velocity fluctuation and mean Reynolds stress, and the negative vorticity improves the distribution of streamwise velocity. Therefore, the optimal control effect with a drag reduction of up to 58% can be obtained. [ABSTRACT FROM AUTHOR]

Exponential-polar coordinates attached to a moving cylinder are used to deduce the stream function-vorticity equations for two-degree-of-freedom vortex-induced vibration, the initial and boundary conditions, and the distribution of the hydrodynamic force, which consists of the vortex-induced force, inertial force, and viscous damping force. The fluid-structure interactions occurring from the motionless cylinder to the steady vibration are investigated numerically, and the variations of the flow field, pressure, lift/drag, and cylinder displacement are discussed. Both the dominant vortex and the cylinder shift, whose effects are opposite, affect the shear layer along the transverse direction and the secondary vortex along the streamwise direction. However, the effect of the cylinder shift is larger than that of the dominant vortices. Therefore, the former dominates the total effects of the flow field. Moreover, the symmetry of the flow field is broken with the increasing shear rate. With the effect of the background vortex, the upper vortices are strengthened, and the lower vortices are weakened; thus, the shear layer and the secondary vortices induced by the upper shedding vortices are strengthened, while the shear layer and the secondary vortices induced by the lower shedding vortices are weakened. Therefore, the amplitudes of the displacement and drag/lift dominated by the upper vortex are larger than those of the displacement and drag/lift dominated by the lower vortex. [ABSTRACT FROM AUTHOR]

Flexible and transparent electronics enters into a new era of electronic technologies. Ubiquitous applications involve wearable electronics, biosensors, flexible transparent displays, radio-frequency identifications (RFIDs), etc. Zinc oxide (ZnO) and relevant materials are the most commonly used inorganic semiconductors in flexible and transparent devices, owing to their high electrical performances, together with low processing temperatures and good optical transparencies. In this paper, we review recent advances in flexible and transparent thin-film transistors (TFTs) based on ZnO and relevant materials. After a brief introduction, the main progress of the preparation of each component (substrate, electrodes, channel and dielectrics) is summarized and discussed. Then, the effect of mechanical bending on electrical performance is highlighted. Finally, we suggest the challenges and opportunities in future investigations. [ABSTRACT FROM AUTHOR]

Metal nanostructures integrated with soft, elastomeric substrates provide an unusual platform with capabilities in plasmonic frequency tuning of mechanical strain. In this paper, we have prepared a tunable optical device, dense arrays of plasmonic nanodisks on a low-modulus, and high-elongation elastomeric substrate with a three-dimensional (3D) sinusoidal wavy, and their optical characteristics have been measured and analyzed in detail. Since surface plasmon is located and propagates along metal surfaces with sub-wavelength structures, and those dispersive properties are determined by the coupling strength between the individual structures, in this study, a 3D sinusoidal curve elastomeric substrate is used to mechanically control the inter-nanodisk spacing by applying straining and creating a frequency tunable plasmonic device. Here we study the optical resonance peak shifting generated by stretching this type of flexible device, and the role that 3D sinusoidal curve surface configuration plays in determining the tunable properties. Since only the hybrid dipolar mode has been observed in experiments, the coupled dipole approximation (CDA) method is employed to simulate the optical response of these devices, and the experimental and simulation results show that these devices have high tunability to shift optical resonance peaks at near-infrared wavelengths, which will provide strong potential for new soft optical sensors and wearable plasmonic sensors. [ABSTRACT FROM AUTHOR]

The B-spline configuration-interaction method is applied to the investigations of dynamic dipole polarizabilities for the four lowest triplet states (2 3S, 33S, 23P, and 33P) of the Li+ ion. The accurate energies for the triplet states of n3S, n3P, and n3D, the dipole oscillator strengths for 23S(33S) → n3P, 23P(33P) → n3S, and 23P(33P) → n3D transitions, with the main quantum number n up to 10 are tabulated for references. The dynamic dipole polarizabilities for the four triplet states under a wide range of photon energy are also listed, which provide input data for analyzing the Stark shift of the Li+ ion. Furthermore, the tune-out wavelengths in the range from 100 nm to 1.2 μm for the four triplet states, and the magic wavelengths in the range from 100 nm to 600 nm for the 23S → 33S, 23S → 23P, and 23S → 33P transitions are determined accurately for the experimental design of the Li+ ion. [ABSTRACT FROM AUTHOR]

A variational principle code which can calculate self-consistently currents on the conductors is used to assess the coupling characteristic of the EAST 4-strap ion cyclotron range of frequency (ICRF) antenna. Taking into account two layers of antenna conductors without lateral frame but with slab geometry, the antenna impedances as a function of frequency and the structure of RF field excited inside the plasma in various phasing cases are discussed in this paper. [ABSTRACT FROM AUTHOR]

We propose a novel scheme of optical confinement for atoms by using a concave grating reflector. The two-dimension grating structure with a concave surface shape exhibits strong focusing ability under radially polarized illumination. Especially, the light intensity at the focal point is about 100 times higher than that of the incident light. Such a focusing optical field reflected from the curved grating structure can provide a deep potential to trap cold atoms. We discuss the feasibility of the structure serving as an optical dipole trap. Our results are as follows. (i) Van der Waals attraction potential to the surface of the structure has a low effect on trapped atoms. (ii) The maximum trapping potential is ∼ 1.14 mK in the optical trap, which is high enough to trap cold 87Rb atoms from a standard magneto-optical trap with a temperature of 120 μK, and the maximum photon scattering rate is lower than 1/s. (iii) Such a microtrap array can also manipulate and control cold molecules, or microscopic particles. [ABSTRACT FROM AUTHOR]

The dynamic dipole polarizabilities for 1S, 2S and 3S states of the hydrogen atom are calculated using the finite B-spline basis set method, and the magic wavelengths for 1S—2S and 1S—3S transitions are identified. In comparison of the solutions from the Schrödinger and Dirac equations, the relativistic corrections on the magic wavelengths are of the order of 10−2 nm. The laser intensities for a 300-Er-deep optical trap and the heating rates at 514 and 1371 nm are estimated. The reliable prediction of the magic wavelengths would be helpful for the experimental design on the optical trapping of the hydrogen atoms, and in turn, it would be helpful to improve the accuracy of the measurements of the hydrogen 1S—2S and 1S—3S transitions. [ABSTRACT FROM AUTHOR]

Based on the experimental phenomena of flexoelectric response at defect sites in nematic inversion walls conducted by Kumar et al., we gave the theoretical analysis using the Frank elastic theory. When a direct-current electric field normal to the plane of the substrate is applied to the parallel aligned nematic liquid crystal cell with weak anchoring, the rotation of ±1 defects in the narrow inversion walls can be exhibited. The free energy of liquid crystal molecules around the +1 and –1 defect sites in the nematic inversion walls under the electric field was formulated and the electric-field-driven structural changes at the defect site characterized by polar and azimuthal angles of the local director were simulated. The results reveal that the deviation of azimuthal angle induced by flexoelectric effect are consistent with the switching of extinction brushes at the +1 and −1 defects obtained in the experiment conducted by Kumar et al. [ABSTRACT FROM AUTHOR]

A uniform doping ultra-thin silicon-on-insulator (SOI) lateral-double-diffused metal-oxide-semiconductor (LDMOS) with low specific on-resistance (Ron,sp) and high breakdown voltage (BV) is proposed and its mechanism is investigated. The proposed LDMOS features an accumulation-mode extended gate (AG) and back-side etching (BE). The extended gate consists of a P– region and two diodes in series. In the on-state with VGD > 0, an electron accumulation layer is formed along the drift region surface under the AG. It provides an ultra-low resistance current path along the whole drift region surface and thus the novel device obtains a low temperature distribution. The Ron,sp is nearly independent of the doping concentration of the drift region. In the off-state, the AG not only modulates the surface electric field distribution and improves the BV, but also brings in a charge compensation effect to further reduce the Ron,sp. Moreover, the BE avoids vertical premature breakdown to obtain high BV and allows a uniform doping in the drift region, which avoids the variable lateral doping (VLD) and the “hot-spot” caused by the VLD. Compared with the VLD SOI LDMOS, the proposed device simultaneously reduces the Ron,sp by 70.2% and increases the BV from 776 V to 818 V. [ABSTRACT FROM AUTHOR]

We propose a femtosecond laser polarization modulation scheme to control the up-conversion (UC) luminescence in Er3+-doped NaYF4 nanocrystals dispersed in the silicate glass. We show that the UC luminescence can be suppressed when the laser polarization is changed from linear through elliptical to circular, and the higher repetition rate will yield the lower control efficiency. We theoretically analyze the physical control mechanism of the UC luminescence polarization modulation by considering on- and near-resonant two-photon absorption, energy transfer up-conversion, and excited state absorption, and show that the polarization control mainly comes from the contribution of near-resonant two-photon absorption. Furthermore, we propose a method to improve the polarization control efficiency of UC luminescence in rare-earth ions by applying a two-color femtosecond laser field. [ABSTRACT FROM AUTHOR]

The effect of dielectric cladding on modifying a mode field based on a multilayer planar surface plasmon polariton (SPP) waveguide is investigated at the telecom wavelength of 1.55 μm. Through numerical calculations based on the transfer matrix method and Cauchy integration method, we point out that the mode loss and the mode size can be efficiently engineered via tailoring the dielectric cladding layer. With appropriately optimized thickness and refractive index of the dielectric cladding, the mode size and mode loss of the long-range SPP modes supported by the proposed structure could reach their minima simultaneously such that the figure of merit exhibits a maximum, which breaks the trade-off relationship between confinement and attenuation of SPP waveguide to a certain degree. Furthermore, benefiting from the dielectric cladding effect, the adjustability of field distribution in the dielectric region provides a simple and effective means for improving the light–matter interaction strength for the purpose of SPP signal modulating, detecting or sensing. [ABSTRACT FROM AUTHOR]

In this work, we developed a general and feasible method to improve both Voc and Jsc in polymer/ZnO nanrod array (ZnO-NRA) hybrid solar cells (HSCs) through modification of the heterojunction interface by using a combination of inorganic and organic methods. First, homogeneous ZnO core/shell array (CSA), in which ZnO nanorods in array served as the core and ZnO quantum dot (QD) films acted as shells, was synthesized by inorganic modification. Next, the ZnO-CSA was modified with organic molecules (Z907) on QD shell surfaces by a solvothermal method. After co-modification of the polymer/ZnO-NRA heterojunction interfaces by the QD shells and organic molecules, the device efficiency improved by 4.8 times compared with that of pristine ZnO-NRA based solar cells. Our results indicate that a higher efficiency of HSCs can be realized by inorganic and organic co-modification of their heterojunction interfaces. [ABSTRACT FROM AUTHOR]

High-quality and sizable single crystals are crucial for studying the intrinsic properties of unconventional superconductors, which are lacking in the 1111 phase of Fe-based superconductors. Here we report the successful growth of CaFeAsF single crystals with sizes of 1–2 mm using the self-flux method. Owing to the availability of the high-quality single crystals, the structure and transport properties were investigated with a high reliability. The structure was refined by using single-crystal x-ray diffraction data, which confirms earlier reports on the basis of powder data. A clear anomaly associated with the structural transition was observed at 121 K from the resistivity, magnetoresistance, and magnetic susceptibility measurements. Another kink-feature at 110 K, most likely an indication of antiferromagnetic transition, was also detected in the resistivity data. Our results supply a basis from which to propel physical investigations of the 1111 phase of Fe-based superconductors. [ABSTRACT FROM AUTHOR]

We numerically demonstrate terahertz multichannel filters with independently tunable defect modes based on fractal photonic crystals. Single defect and multiple defects models are proposed to fabricate the multichannel terahertz filters. The facts that the wave functions of the defect states do not overlap and their bases are orthogonal lead to the independency among the defect modes. The simulated results theoretically provide the principle for fabricating independently tunable multichannel terahertz filters by utilizing one-dimensional photonic crystals with defects. [ABSTRACT FROM AUTHOR]

In this paper, we theoretically investigate the coherent enhancement of resonance-mediated (2+2) four-photon absorption. It is found that by shaping the spectral phase with a p phase step, the resonance-mediated (2+2) four-photon transition probability can be enhanced. Furthermore, the coherent enhancement dependences on the detuning between the two two-photon absorptions, laser spectral bandwidth and laser centre frequency are explicitly discussed and analysed. We believe these theoretical results may play an important role in enhancing more complex resonance-mediated multiphoton absorption processes. [ABSTRACT FROM AUTHOR]

The presence of a strong, changing, randomly-oriented, local electric field, which is induced by the photo-ionization that occurs universally in colloidal semiconductor quantum dots (QDs), makes it difficult to observe the quantum-confined Stark effect in ensemble of colloidal QDs. We propose a way to inhibit such a random electric field, and a clear quantum-confined Stark shift is observed directly in close-packed colloidal QDs. Besides the applications in optical switches and modulators, our experimental results indicate how the oscillator strengths of the optical transitions are changed under external electric fields. [ABSTRACT FROM AUTHOR]

Triacetone triperoxide (TATP) is one of the most sensitive known explosives and can be easily synthesized using the commonly available chemicals acetone and hydrogen peroxide, but is difficult to be detected. In this study, In2O3 nanoparticles were synthesized by a glucose-assisted solvothermal method at 120 degC for 18 h. The gas sensor based on In2O3 nanoparticles exhibits a high response, fast response and recovery, a wide detecting range of 0.50-500 mg, good stability and excellent stability to TATP. [ABSTRACT FROM AUTHOR]

Using density functional theory and nonequilibrium Green's function (NEGF) formalism, we have theoretically investigated the binding of organic donor, acceptor and metal atoms on graphene sheets, and revealed the effects of the different noncovalent functionalizations on the electronic structure and transport properties of graphene. The adsorptions of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and tetrathiafulvalene (TTF) induce hybridization between the molecular levels and the graphene valence bands, and transform the zero-gap semiconducting graphene into a metallic graphene. However, the current versus voltage (I-V) simulation indicates that the noncovalent modifications by organic molecules are not sufficient to significantly alter the transport property of the graphene for sensing applications. We found that the molecule/graphene interaction could be dramatically enhanced by introducing metal atoms to construct molecule/metal/graphene sandwich structures. A chemical sensor based on iron modified graphene shows a sensitivity two orders of magnitude higher than that of pristine graphene. The results of this work could help to design novel graphene-based sensing or switching devices. [ABSTRACT FROM AUTHOR]

Dissolved cardiac myocytes can couple together and generate synchronous beatings in culture. We observed a synchronized early after-depolarization(EAD)-like rhythm in cultured cardiac myocytes and reproduced the experimental observation in a network mathematical model whose dynamics are close to a Hopf bifurcation. The mechanism for this EAD-like rhythm is attributed to noised-induced stochastic alternatings between the focus and the limit cycle. These results provide novel understandings for pathological heart rhythms like the early immature beatings. [ABSTRACT FROM AUTHOR]

A model of high-overtone bulk acoustic resonators is used to study the effects of thickness deviation of elastic plates on resonance frequency spectra in planar multi-layered systems. The resonance frequency shifts induced by the thickness deviations of the elastic plates periodically vary with the resonance order, which depends on the acoustic impedance ratios of the elastic plates to piezoelectric patches. Additionally, the center lines of the frequency shift oscillations linearly change with the orders of the resonance modes, and their slopes are sensitive to the thickness deviations of the plates, which can be used to quantitatively evaluate the thickness deviations. [ABSTRACT FROM AUTHOR]

The interactions between four different graphenes (including pristine, B- or N-doped and defective graphenes) and small gas molecules (CO, NO, NO2 and NH3) were investigated by using density functional computations to exploit their potential applications as gas sensors. The structural and electronic properties of the graphene-molecule adsorption adducts are strongly dependent on the graphene structure and the molecular adsorption configuration. All four gas molecules show much stronger adsorption on the doped or defective graphenes than that on the pristine graphene. The defective graphene shows the highest adsorption energy with CO, NO and NO2 molecules, while the B-doped graphene gives the tightest binding with NH3. Meanwhile, the strong interactions between the adsorbed molecules and the modified graphenes induce dramatic changes to graphene's electronic properties. The transport behavior of a gas sensor using B-doped graphene shows a sensitivity two orders of magnitude higher than that of pristine graphene. This work reveals that the sensitivity of graphene-based chemical gas sensors could be drastically improved by introducing the appropriate dopant or defect. [ABSTRACT FROM AUTHOR]

Nickel silicide nanowire arrays have been achieved by the decomposition of SiH4 on Ni foil at 650 °C. It is indicated that the nickel silicide nanowires consist of roots with diameter of about 100-200 nm and tips with diameter of about 10-50 nm. A Ni diffusion controlled mechanism is proposed to explain the formation of the nickel silicide nanowires. Field emission measurement shows that the turn-on field of the nickel silicide nanowire arrays is low, at about 3.7 V µm[?]1, and the field enhancement factor is as high as 4280, so the arrays have promising applications as emitters. [ABSTRACT FROM AUTHOR]

With a point-to-plane geometry, the experimental investigation of the current-voltage characteristics in corona discharges demonstrated that existing empirical formulae met with some physical difficulties in explaining the results. By mathematically processing the experimental data and applying the updated knowledge of corona inception, a new general formula in characterizing the relationship of corona current-voltage was derived and expressed as I = K(V [?] V0)n. It was demonstrated that the exponent n falls into a limited scope of 1.5-2.0, and there always exists an optimal exponent n in the scope, which can be determined by maximizing the R-square of regression. Of all the potentially influential factors, it was disclosed that the point radius has the strongest influence on the optimal exponent n, and the effects of ambient conditions and corona polarities are not noticeable. The optimal exponent n holds a fixed value of 2.0 for microscopic points and of 1.5 for large points with a radius in millimetres, but changes decreasingly with the radius for the points of microns. For given experimental conditions, the optimal exponent n almost does not change with the inter-electrode distance. Furthermore, it was demonstrated that the formula is applicable not only for both negative and positive coronas in point-to-plane geometries but also for both polarities in point-to-ring geometries. With the optimal exponent n, the formula can well explain the inconsistencies met by other existing formulae and best represent the characteristics of corona current-voltage with an accuracy of 1 µm. [ABSTRACT FROM AUTHOR]

We have developed a simple approach for the large-scale synthesis of cobalt nitrate carbonate hydroxide hydrate (Co(CO3)0.35(NO3)0.2(OH)1.1·1.74H2O) nanowires via the hydrothermal process using sodium hydroxide and formaldehyde as mineralizers at 120 °C. The porous Co3O4 nanorods 10-30 nm in diameter and hundreds of nanometres in length have been fabricated from the above-mentioned multicomponent nanowires by calcination at 400 °C. The morphology and structure of cobalt nitrate carbonate hydroxide hydrate nanowires and Co3O4 nanorods have been characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and x-ray powder diffraction (XRD). Moreover, the porous Co3O4 nanorods have been applied in the negative electrode materials for lithium ion batteries, which exhibit high electrochemical performance. [ABSTRACT FROM AUTHOR]

A novel solvothermal process using ethylene glycol (EG) as solvent has been employed to synthesize 3D ZnO hollow microhemispheres consisting of numerous orderly and radical nanorods with diameter of about 50 nm and length of several hundred nanometers. The glycol such as EG and the solvothermal process play the critical role in the synthesis of the 3D ZnO hollow microhemispheres by the primary formation of glycolate precursors and subsequent transformation into ZnO. The morphology, structure and optical property of the 3D ZnO hollow microhemispheres have been characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), x-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL). Furthermore, the 3D ZnO hollow microhemisphere based gas sensor exhibits high sensitivity for ethanol and ammonia as well as quick response and recovery time at room temperature due to the high surface-to-volume ratio. [ABSTRACT FROM AUTHOR]