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Aiming at the problems of a narrow operating range and complex modeling of Flame-assisted Fuel Cells (FFCs), an FFC system based on a swirl burner is proposed, and neural network algorithms are used to construct the prediction model for the polarization curve of the FFC system. First, the output voltage and power values of the FFC system are measured under different working conditions, and various experimental parameters are collected to form a dataset; second, the correlation analysis method is used to screen out the parameters that are highly correlated with the output voltage as the input variables of the neural network; finally, the prediction model of the polarization curve is constructed, and back propagation (BP), long short term memory, and 1D-CNN algorithms are chosen to examine the applicability of various neural networks for the FFC system. The experimental and polarization characteristic curve prediction results show that the FFC system can obtain a maximum output voltage of 10.6 V and power of 7.71 W. The average relative errors of the three algorithms are 5.23%, 4.08%, and 6.19%, respectively, with the BP neural network algorithm showing the best generalization ability. The study provides support for the application of the FFC system in aerospace and other fields. [ABSTRACT FROM AUTHOR]

In this paper, we study the asymptotic and transient dynamics of a predator–prey model with square root functional responses and random perturbation. Firstly, the mean square stability matrix is obtained from the stability theory of stochastic systems, and three stability indexes (root-mean-square resilience, root-mean-square reactivity and root-mean-square amplification envelope) of the ecosystem response to stochastic disturbances are calculated. We find that: (1) no matter which population is disturbed, increasing the intensity of disturbance improves the ability of the system leaves steady state and thus decreases the stability. The root-mean-square amplification envelope rises with increasing disturbance intensity, (2) the system is more sensitive to the disturbance of the predator than disturbance to prey, (3) ρ m a x and t m a x are important indicators, which represent the intensity and time of maximum amplification by disturbance. These findings are helpful for managers to take corresponding management measures to reduce the disturbances, especially for predators, thereby avoiding the possible change of the structure and functions of the ecosystem. [ABSTRACT FROM AUTHOR]

Urban heat island (UHI) and sea–land-breeze systems are well-known and important characteristics of the climate of coastal cities. To model these, the accurate estimation of the surface energy balance (SEB) is a key factor needed to improve local-scale simulations of thermodynamic and dynamic boundary circulations. The Weather Research and Forecasting Model with a single-layer urban canopy model (WRF/SLUCM), with parameters derived from MODIS and local GIS information, is used to investigate the UHI and sea-breeze circulations (SBC) in the megacity of Shanghai. The WRF/SLUCM can reproduce observed urban radiation and SEB fluxes, near-surface meteorological variables, and the evolution of the UHI and SBC. Simulations for an August period show the maximum UHI tends to drift northwest in the afternoon, driven by the prevailing southeast wind. The sea breeze lasts for about 4 h and is strongest between 1200 and 1400 local time (UTC + 8 h). The interaction between UHI and SBC is evident with low-level convergence, upward motion, and moisture transport from the sea and urban breezes simulated. An urban circulation (horizontal/vertical/time scales: ∼20 km/∼1.5 km/∼3 h) with thermal vertical motions (∼1.5 m s−1) above the urban area and an SBC (horizontal/vertical/time scales: 6–7 km/∼1 km/2–3-h) above the northern coastal suburb occur. Combined the sea breeze and southerly winds form a low-level wind shear (convergence zone) ∼5 km from the coast that penetrates ∼20 km inland to the urban center. Using the WRF/SLUCM simulations we improve understanding of the complex spatial dynamics of summertime urban heating in coastal megacities, such as Shanghai. [ABSTRACT FROM AUTHOR]

Efficient mixing is of great importance for engineering applications of hypersonic propulsion systems. With supersonic air flowing through the interior of combustor in milliseconds, rapid mixing of airstream and fuel becomes one of the great challenges, and it is imperative to employ mixing enhancement strategies to improve the system performance. In present work the splitter plate jet assisted mixing (SPJAM) strategy is proposed and direct numerical simulations are conducted to reveal enhanced-mixing mechanisms. Both instantaneous fine structures and turbulent intensity distributions are obtained to analyze the flow dynamical behaviors. Mixing layer thickness growth rate and structure topology properties affected by SPJAM are researched as well. The results indicate that the introduction of SPJAM can significantly promote mixing by means of the newly found T-shaped structures and its dynamics. The interaction of T-shaped structure and inherent Kelvin-Helmholtz vortex leads to the breakdown of flow structures, which can obviously increase the interface of upper and lower streams. Turbulent intensity analysis suggests that with the effect of SPJAM, the region where turbulent activity exists is notably extended, and the peak values of the fluctuations are much larger. The evolution of transversely-integrated turbulent kinetic energy (IK) indicates that rapid increase of IK appear in the near field of the flow. Spatial correlation analysis results indicate that vortex size is notably increased with the introduction of SPJAM, especially for that with the strategy set at the front of the splitter plate. Through exploration of the enhanced-mixing mechanisms, present preliminary work indicates that the proposed strategy is a good candidate for efficient mixing, and in the future more detailed work including three-dimensional simulations concerning the strategy optimization should be conducted. • Splitter plate jet assisted mixing (SPJAM) strategy is proposed to promote mixing. • Direct numerical simulations are conducted to reveal the enhanced-mixing mechanisms. • T-shaped structures and its dynamics play an important role for mixing enhancement. • The proposed strategy is a good candidate in the application of RBCC and Scramjet engine. [ABSTRACT FROM AUTHOR]

In a previous paper, a numerical method preserving positivity was constructed for stochastic age‐dependent population equations. However, only the local error of the balanced Euler method was verified. In this paper, we will give the global error of this numerical method in the mean square sense. Moreover, the strong convergence order is investigated which proves the convergence of the aforementioned method with strong order p=12 in the mean of global error. At last, we give some numerical experiments to illustrate the efficiency of our method. [ABSTRACT FROM AUTHOR]

We propose a cavity as an actuator to actuate the supersonic mixing layer downstream a thick splitter plate. The cavity-actuated case at Re = 1.73 × 105 is simulated using large eddy simulation. The forced dynamics is resolved by the cluster-based network model (CNM) from a probabilistic point of view. Introducing a cavity obtains a 50% increase in the growth rate of vorticity thickness. The recirculation region immediately downstream the trailing edge of the splitter plate is largely reduced, which contributes to the advanced and fast growth of the redeveloping mixing layer. The cavity oscillation induces three-dimensional features that are beneficial to the small-scale mixing. Spectral analysis reveals that the cavity-actuated flow field exhibits the phenomena of the strict frequency-lock and temporal mode-switching. The CNM successfully resolves the intermittent dynamics of the supersonic mixing layer using only ten centroids. The CNM's outcomes reveal two flow regimes of the unforced case: the Kelvin–Helmholtz vortex and vortex pairing. The cavity oscillation significantly affects the flow patterns of the centroids, which exhibit flow structures closely associated with the wake mode and shear-layer mode of the cavity oscillations. The dynamics of the cavity-actuated case is tamed into a strictly periodic transition loop among ten clusters undergoing the cyclic motion of the cluster energy fluctuation from the maximum to the minimum. Each centroid of the cavity-actuated case transports much more turbulent kinetic energy than that of the unforced case. Overall, the cavity-actuated attractor gets a 3.27 times increase in the energy fluctuation. [ABSTRACT FROM AUTHOR]

Chemiluminescence information is of great significance for characterization of flame structure and combustion characteristics. An atmospheric low swirl burner was developed to investigate the chemiluminescence characteristics of OH* and CH* in low swirl flames, with the equivalence ratio varying from 0.8 to 1.2 and the swirl number from 0.2 to 0.6. The chemiluminescence images were captured via ICCD cameras coupled with narrow-bandpass filters, and an Abel inversion method was introduced to transform the line-of-sight-integrated image into two-dimensional radial distributions. The results show that the distribution of CH* is smaller than that of OH* and concentrated more upstream of the flame near the burner. The equivalence ratio has a relatively more direct influence on chemical reactions, while the swirl number has a more evident effect on the flame structure. As the equivalence ratio increases, the peak value of OH* and CH* increases and the peak position moves downstream of the flame, suggesting that the chemical reactions become more intense. In contrast, the height and width of chemiluminescence distribution increase linearly with increasing swirl number. Moreover, it is found that the equivalence ratio and swirl number can be feasibly estimated based on chemiluminescence measurement results, using the correlation between them derived from this study. [ABSTRACT FROM AUTHOR]

The cluster-based Markov model (CMM) is performed on a numerically simulated supersonic mixing layer at Re = 10 400 to extract physical mechanisms. The high-dimensional state space of the supersonic mixing layer is automatically partitioned into ten relatively homogeneous clusters with representative states called centroids via the cluster analysis. The transition dynamics is conceptualized as a Markov model between centroids using the cluster transition matrix from a probabilistic point of view. A comprehensive analysis of CMM's outcomes reveals two flow regimes: the single/double-vortex interaction (SDV) and multiple-vortex interaction (MV). The SDV regime plays the dominant role in the supersonic mixing layer, although any single centroid from the MV group carries much larger energy than that from the SDV group. More complicated patterns of vortex are well captured in an intelligent way associated with triple-vortex, quadruple-vortex, and even quintuple-vortex interaction. These vortex formations transport much more energy than the double-vortex pairing/merging. The CMM reveals a complicated set of dynamics that intermittently appear in the two regimes. The inner-circulation transition inside the SDV regime is the most probable route in the supersonic mixing layer. The MV regime can only be accessed from the SDV regime; meanwhile, it inclines to move back to the SDV regime. The transitions linking two regimes undergo large energy fluctuations. The predicted distribution of future cluster probability converges to a unique stationary distribution, which approximates the statistical probability distribution of the dataset. [ABSTRACT FROM AUTHOR]

H2/air supersonic mixing layers were calculated with different splitter plates thickness in both inert and reactive cases. The decay of mixing layer growth rates with the presence of heat release indicates the inhibition of fluctuations of velocity and scalar. Analyses of mean pressure and mean scalar show that the combustion efficiency increases with thickening of splitter plate. Heat release effect strengthens local compressibility, and then the relation among local compressibility, mean shear and velocity fluctuations is built. Considering heat release effect, the peak value of turbulent kinetic energy of moderate thickness splitter plates (the thickness equals 4 mm) is smallest. Similar phenomena are observed in scalar variance and vorticity variance, indicating the turbulent development of moderate thickness splitter plates is slowest. • Mixing layer growth rates decrease in the presence of heat release. • Combustion efficiency increases with thickening of splitter plate. • Thickening the splitter plate reduces the importance of nibbling. • The relation among local compressibility, shear and fluctuations are built. • The turbulent development of R-4 (moderate thickness) is slowest. [ABSTRACT FROM AUTHOR]

Numerical and experimental studies on 1-D, steady premixed methane-air flames were performed to investigate the quantitative measurement of heat release rate (HRR) using chemiluminescence. A detailed reaction mechanism, incorporating sub-reaction models for excited state radicals (CH* and OH*) was employed in the numerical study. The numerical work utilized the CHEMKIN-PRO package to investigate the distribution rule of excited state radicals and HRR. The heat release characteristic of elementary reactions and the relationship between net reaction rate and HRR were analyzed as well. According to the result of numerical study, experimental work was conducted to measure the HRR and chemiluminescence of OH* and CH* in the flat flames. The distributions of HRR and chemiluminescent intensity were measured by high-accuracy coated Pt/13%-Rh-Pt thermocouple and ICCD camera, respectively. The results shows that OH* and CH* are located in the narrow area where severe chemical reactions occur with much heat release. Compared to CH*, OH* is more effective in marking the spatial distribution of HRR and the correlation between chemiluminescent intensity and HRR possesses characteristic of linearity. Thus, the HRR quantitative measurement method using chemiluminescence has been acquired. • OH* is more effective in marking the spatial distribution of HRR than CH*. • HRR can be measured quantitatively by OH* and CH* chemiluminescence. • There is a strong linear correlation between chemiluminescent intensity and HRR. • The proportionality coefficient decreases with increasing equivalence ratio. [ABSTRACT FROM AUTHOR]

Direct numerical simulation of a spatially developing supersonic mixing layer with a convective Mach number of 1.0 is conducted. The present work focuses on the structural evolution and the turbulent statistics, and both instantaneous and time-averaged data are utilized to obtain further insight into the dynamical behaviors of the flow. The full development process of instability, including the shear action at the flow early stage, the generation of kinds of typical vortex structures in the flow transition region, and the establishment of self-similar turbulence, is clearly presented. The formation and evolution mechanisms of multiple ring-like vortices are reported and analyzed using the Helmholtz first law in compressible mixing layers, and the role they play in the mixing process in the flow transition stage is researched. The mean velocity distribution and the turbulent intensities are found to have close relations with the evolution of the multiple ring-like vortices. The presence of multiple ring-like vortices leads to local strong ejection and sweep regions that create pockets of partially mixed fluid near the tips of the vortices, which contributes much to the huge energy and momentum transfer of the upper and lower streams. Some anisotropy coefficients and turbulent structure parameters are described and analyzed to better reveal the effects of multiple ring-like vortices on flow behaviors. Our results indicate that with the increase in compressibility, though in a fully turbulent region, mixing layer growth and turbulent intensities are both suppressed, the appearance of multiple ring-like vortices and their evolutions can significantly promote mixing in the transition stage, which is usually ignored by previous researchers. Therefore, employing flow control methods to extend the flow transition stage and help sustain multiple ring-like vortices over a longer distance is a possible technique to enhance mixing. [ABSTRACT FROM AUTHOR]

Abstract The investigations on mixing process and structural topology properties of supersonic planar mixing layer with different inflow conditions are conducted by employing direct numerical simulation. First, the present high-order accuracy numerical methods are validated by comparing the simulation results with the data gained from previous well characterized experimental and numerical cases. Then the high-resolved three-dimensional numerical visualizations of supersonic mixing layer are presented by utilizing Q-criterion. The visualization results show the full development and evolution process of mixing layer, including the shear action, the transition process populated sequentially by Λ-vortices, hairpin vortices and braid structures and the establishment of self-similar turbulence. The effects of density ratio, velocity ratio and convective Mach number between the two parallel streams on mixing layer growth rate are evaluated by examining the indexes including velocity thickness and momentum thickness represented the mixing process. The results indicate that for the only variation of density ratio, the velocity thickness growth rates do not significantly vary, while the momentum thickness becomes larger when the upper and lower streams possess the same density. With the increase of only velocity ratio, the mixing layer becomes more stable and the velocity and momentum thickness are both drastically depressed in the whole flow field. As only convective Mach number increases, the mixing layer growth is inhibited in the near field through the transition delay of the flow, while in the far field, the growth rates are nearly the same for different convective Mach numbers. The spatial correlation analysis of structural topology indicates that the effects of each of the three main flow parameters on vortex topology lead to different mean structure sizes and shapes. The present research is useful for evaluating the effects of different flow parameters on mixing properties, which is important for the future scramjet combustor design and evaluation in engineering. Highlights • Direct numerical simulations of supersonic mixing layers are conducted. • Effects of density ratio, velocity ratio and Mc on mixing process are analyzed. • High-resolution visualization results of the mixing layer are presented. • Topology properties of structures with different flow parameters are revealed. • The paper explains the discrepant conclusions drawn by former researchers. [ABSTRACT FROM AUTHOR]

This paper establishes a novel mathematical model for computing the plume flow field of a carrier-based aircraft engine. Its objective is to study the impact of jet exhaust gases with high temperature, high speed and high pressure on the jet blast deflector. The working condition of the nozzle of a fully powered on engine is first determined. The flow field of the exhaust jet is then numerically simulated at different deflection angle using the three-dimensional Reynolds averaged Navier–Stokes equations and the standard κ - ε turbulence method. Moreover, infra-red temperature tests are further carried out to test the temperature field when the jet blast deflector is at the 45 ∘ deflection angle. The comparison between the simulation results and the experimental results show that the proposed computation model can perfectly describe the system. There is only 8–10% variation between them. A good verification is achieved. Moreover, the experimental results show that the jet blast deflector plays an outstanding role in driving the high-temperature exhaust gases. It is found that 45 ∘ may be the best deflection angle to protect the deck and the surrounding equipment effectively. These data results provide a valuable basis for the design and layout optimization of the jet blast deflector and deck. [ABSTRACT FROM AUTHOR]

Abstract As single component chemiluminescence cannot accurately measure the distribution of heat release rate, this paper put forward the idea of employing OH* and CH* chemiluminescence for the measurement. However, it is difficult to characterize the relationship between chemiluminescence and heat release rate, so the method of deep learning was applied to process numerical simulation results of methane-air steady premixed flames and a deep neural network model was developed to determine the distribution of heat release rate with OH* and CH* chemiluminescence. The evaluation indexes of the model performed satisfactorily: root mean square error of the normalized heat release rate is less than 0.13, mean relative error of peak and opening distance is below 3%, and mean error of peak position less than 0.01 mm. The validation results showed that OH* and CH* chemiluminescence could properly measure the distribution of heat release rate: relative error of peak ranges from −6% to 6%; on test dataset, correlation coefficient between predictive results and simulation results is above 0.99 in terms of heat release rate peak, peak positions and opening distance. Highlights • Deep learning was applied to process numerical simulation results. • HRR can be characterized by OH* and CH* chemiluminescence. • The deep neural network has good generalization ability and average performance. • OH* and CH* chemiluminescence can properly measure the distribution of HRR. [ABSTRACT FROM AUTHOR]

Highlights • A cavity is applied as an actuator to improve mixing in supersonic planar mixing layer. • The coherent structures is strongly locked to frequencies from self-sustaining oscillation of supersonic cavity flow. • The normalized growth rate of cavity-actuated supersonic mixing layer is much larger than the typical result of free shear layer. • Curvature shocklets are firstly observed at the low convective Mach number of 0.22. Abstract Mixing enhancement is vital to combustion efficiency in a rocket-based combined cycle engine. Presently, we propose a cavity as an actuator and investigate the cavity-actuated supersonic mixing layer experimentally using particle image velocimetry (PIV) and nanoparticle-based planar laser scattering (NPLS). Large eddy simulation (LES) is conducted to obtain the detailed flow structures and pressure spectra of the supersonic mixing layer. Results indicate that the vortex evolution of the supersonic mixing layer is locked strongly to the excitation frequencies from the self-sustaining oscillation of supersonic cavity flow in both the near and far flowfields. Multiple coherent structures of different sizes coexist in the initial flowfields, and then only large ones survive downstream. Pressure spectra can reflect the vortex evolution entirely. The third mode of the pressure spectrum gradually becomes dominant due to having the highest energy content. Curvature shocklets are observed in this case at the low convective Mach number of 0.22. The growth rate in the linear process is slightly larger than that of the case without a cavity while the velocity thickness is 3.34 times as large as that. The normalized growth rate sees a massive increase and is 8.95 times as large as the typical result of a free supersonic shear layer. [ABSTRACT FROM AUTHOR]

Abstract The development of supersonic and hypersonic aeronautical projects has led to a renewal of interest and research in supersonic mixing processes and methods to control them. Due to the compressibility effects, the mixing process in supersonic condition is significantly inhibited. Limited flow residence time (at the order of microseconds) for mixing of supersonic airstream and fuel in a scramjet combustor calls for the development of techniques for mixing enhancement. In the present paper, the applicable techniques for mixing enhancement of supersonic mixing layer flows are reviewed comprehensively. Following the brief introduction of fundamentals of supersonic mixing layer, this paper discusses the mixing enhancement methods in the categories of: passive flow control techniques, active flow control techniques and shock wave induced mixing enhancement strategy. Based on the review of former progress, the gaps in current knowledge and areas where more research is needed are pointed out. Meanwhile, the mechanisms of different enhanced mixing methods are summarized, which can be a reference and guidance for the future techniques design for mixing enhancement of supersonic flows. Highlights • Enhanced mixing methods for supersonic mixing layers are reviewed. • Overview of the fundamentals of supersonic mixing layers is presented. • The mechanisms of different methods for mixing enhancement are revealed. • The present review can be a reference and guidance for future strategy design. [ABSTRACT FROM AUTHOR]

Combustion instabilities have been a plaguing challenge in lean-conditioned propulsion systems. An open-loop control system was developed using machine learning to suppress pressure fluctuations and NO x emissions simultaneously. The open-loop control is realized by regulating the solenoid valve to modulate the methane supply. Control laws comprising the multi-frequency forcing are generated via the linear genetic programming (LGP), before being converted into square waves with different frequencies and duty cycles to activate the solenoid valve. The cost function is intended to evaluate and rank individuals of each generation, so as to select candidates for evolution. Optimized periodic forcing (OPF) with different duty cycles (d) and frequencies (f P) is set to provide a comparison with the superiority of multi-frequency forcing of LGP. Three stages of pressure oscillations and NO x emissions have been found as d increases from 0.5 to 1.0: high level, transition, and low level, revealing the transition of the combustion mode. After ten generations of development, the pressure amplitude and NO x emissions are reduced by 67.1% and 36.9% under the optimal control law identified by LGP, respectively. The flame structure images and Rayleigh index maps indicate that the convective movement of the flame, which may be the key factor driving combustion instabilities, can be suppressed by the optimal control law. Furthermore, the proximity graph of the similarity between control laws is introduced to depict the machine learning process, with the steepest descent lines visualizing its ridgeline topology. With the evolution process, individuals are found moving closer to the top right-hand corner of the map, and two main search pathways gradually become clear. [ABSTRACT FROM AUTHOR]

The flow behaviors and mixing characteristics of a supersonic mixing layer with a convective Mach number of 0.2 have been experimentally investigated utilizing nanoparticle-based planar laser scattering and particle image velocimetry techniques. The full development and evolution process, including the formation of Kelvin-Helmholtz vortices, breakdown of large-scale structures and establishment of self-similar turbulence, is exhibited clearly in the experiments, which can give a qualitative graphically comparing for the DNS and LES results. The shocklets are first captured at this low convective Mach number, and their generation mechanisms are elaborated and analyzed. The convective velocity derived from two images with space-time correlations is well consistent with the theoretical result. The pairing and merging process of large-scale vortices in transition region is clearly revealed in the velocity vector field. The analysis of turbulent statistics indicates that in weakly compressible mixing layers, with the increase of convective Mach number, the peak values of streamwise turbulence intensity and Reynolds shear stress experience a sharp decrease, while the anisotropy ratio seems to keep quasi unchanged. The normalized growth rate of the present experiments shows a well agreement with former experimental and DNS data. The validation of present experimental results is important for that in the future the present work can be a reference for assessing the accuracy of numerical data. [ABSTRACT FROM AUTHOR]

Visualization of the heat release zone (HRZ) of highly turbulent flames is significantly important to understand the interaction between turbulence and chemical reactions, which is the foundation to design and optimize engines. Simultaneous measurements of OH and CH 2 O using planar laser-induced fluorescence (PLIF) were performed to characterize the HRZ. A well-designed piloted premixed jet burner was employed to generate four turbulent premixed CH 4 /air jet flames, with different jet Reynolds numbers ( Re jet ) ranging from 4900 to 39200. The HRZ was visualized by both the gradient of OH and the pixel-by-pixel product of OH and CH 2 O. It is shown that turbulence has an increasing effect on the spatial structure of the flame front with an increasing height above the jet exit for the premixed jet flames, which results in the broadening of the HRZ and the increase of the wrinkling. The HRZ remains thin as the Re jet increases, whereas the preheat zone is significantly broadened and thickened. This indicates that the smallest turbulent eddies can only be able to enter the flame front rather than the HRZ in the present flame conditions. The flame quenching is observed with Re jet = 39200, which may be due to the strong entrainment of the cold air from outside of the burned gas region. [ABSTRACT FROM AUTHOR]

Using the Euler scheme to simulate the stochastic differential equations (SDEs) models in finance often gives rise to the problem that the exact solution is positive while the numerical solution is not. Recently, we find that this problem existed in the jump–diffusion models as well. Hence, this paper aims to construct a numerical method preserving positivity for jump–diffusion option pricing models. We generalize the balanced implicit method (BIM) to the jump–diffusion models, which already turned out to be efficient for preserving positivity in SDE models. Then the positivity of BIM for jump–diffusion models is proved under some conditions. Finally, a numerical example is simulated to verify the positivity and efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, our aim is to develop a compensated split-step θ (CSS θ) method for nonlinear jump-diffusion systems. First, we prove the convergence of the proposed method under a one-sided Lipschitz condition on the drift coefficient, and global Lipschitz condition on the diffusion and jump coefficients. Then we further show that the optimal strong convergence rate of CSS θ can be recovered, if the drift coefficient satisfies a polynomial growth condition. At last, a nonlinear test equation is simulated to verify the results obtained from theory. The results show that the CSS θ method is efficient for simulating the nonlinear jump-diffusion systems. [ABSTRACT FROM AUTHOR]

The ability to reconstitute sodium channel function and pharmacology in vitro using cloned subunits of known structure has greatly enhanced our understanding of the action of pyrethroid insecticides at this target and the structural determinants of resistance and interspecies selectivity. However, the use of reconstituted channels raises three critical questions: (1) Which subunits and subunit combinations should be used? (2) Which heterologous expression system is preferred? (3) Which combination of subunits and expression system best represents the function of native neuronal channels in the organism of interest? This review considers these questions from the perspective of recent research in this laboratory on the action of pyrethroid insecticides on rat Na v 1.6 sodium channels by comparing the effects of heteroligomeric complex composition on channel function and insecticide response when channels are expressed in either Xenopus oocytes or stably-transformed HEK293 cells. These comparisons provide new insight into the influence of cellular context on the functional and pharmacological properties of expressed channels, the modulatory effects of sodium channel auxiliary subunits on the action of pyrethroids, and the relative fidelity of the Xenopus oocyte and HEK293 cell expression systems as model systems for studying of channel function and pyrethroid action. [ABSTRACT FROM AUTHOR]

The aim of this paper is to construct a numerical method preserving positivity for stochastic age-dependent population equations. We use the balanced implicit numerical techniques to maintain the nonnegative path of the exact solution. It is proved that the Balanced Implicit Method (BIM) preserves positivity and converges with strong order 1/2 under given conditions. Finally, two examples are simulated to verify the positivity and efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

Computed tomography of chemiluminescence (CTC) is a promising technique for combustion diagnostics, providing instantaneous 3D information of flame structures, especially in harsh circumstance. This work focuses on assessing the feasibility of CTC and investigating structures of hydrogen-air premixed laminar flames using CTC. A numerical phantom study was performed to assess the accuracy of the reconstruction algorithm. A well-designed burner was used to generate stable hydrogen-air premixed laminar flames. The OH⁎ chemiluminescence intensity field reconstructed from 37 views using CTC was compared to the OH⁎ chemiluminescence distributions recorded directly by a single ICCD camera from the side view. The flame structures in different flow velocities and equivalence ratios were analyzed using the reconstructions. The results show that the CTC technique can effectively indicate real distributions of the flame chemiluminescence. The height of the flame becomes larger with increasing flow velocities, whereas it decreases with increasing equivalence ratios (no larger than 1). The increasing flow velocities gradually lift the flame reaction zones. A critical cone angle of 4.76 degrees is obtained to avoid blow-off. These results set up a foundation for next studies and the methods can be further developed to reconstruct 3D structures of flames. [ABSTRACT FROM AUTHOR]

Graphical abstract: [ABSTRACT FROM AUTHOR]

The honey bee ( Apis mellifera L.) is the most important managed pollinator species worldwide and plays a critical role in the pollination of a diverse range of economically important crops. This species is important to agriculture and historically has been used as a surrogate species for pollinators to evaluate the potential adverse effects for conventional, biological, and microbial pesticides, as well as for genetically engineered plants that produce pesticidal products. As part of the ecological risk assessment of MON 87411 maize, which expresses a double-stranded RNA targeting the Snf7 ortholog ( DvSnf7) in western corn rootworm ( Diabrotica virgifera virgifera), dietary feeding studies with honey bee larvae and adults were conducted. Based on the mode of action of the DvSnf7 RNA in western corn rootworm, the present studies were designed to be of sufficient duration to evaluate the potential for adverse effects on larval survival and development through emergence and adult survival to a significant portion of the adult stage. Testing was conducted at concentrations of DvSnf7 RNA that greatly exceeded environmentally relevant exposure levels based on expression levels in maize pollen. No adverse effects were observed in either larval or adult honey bees at these high exposure levels, providing a large margin of safety between environmental exposure levels and no-observed-adverse-effect levels. Environ Toxicol Chem 2016;35:287-294. © 2015 The Authors. Environmental Toxicology and Chemistry Published by Wiley Periodicals, Inc. on behalf of SETAC. [ABSTRACT FROM AUTHOR]

The mixing process has been an important issue for the design of supersonic combustion ramjet engine, and the mixing efficiency plays a crucial role in the improvement of the combustion efficiency. In the present study, nanoparticle-based planar laser scattering (NPLS), particle image velocimetry (PIV) and large eddy simulation (LES) are employed to investigate the flow and mixing characteristics of supersonic mixing layer under different forced vibration conditions. The indexes of fractal dimension, mixing layer thickness, momentum thickness and scalar mixing level are applied to describe the mixing process. Results show that different from the development and evolution of supersonic mixing layer without vibration, the flow under forced vibration is more likely to present the characteristics of three-dimensionality. The laminar flow region of mixing layer under forced vibration is greatly shortened and the scales of rolled up Kelvin–Helmholtz vortices become larger, which promote the mixing process remarkably. The fractal dimension distribution reveals that comparing with the flow without vibration, the turbulent fluctuation of supersonic mixing layer under forced vibration is more intense. Besides, the distribution of mixing layer thickness, momentum thickness and scalar mixing level are strongly influenced by forced vibration. Especially, when the forcing frequency is 4000 Hz, the mixing layer thickness and momentum thickness are 0.0391 m and 0.0222 m at the far field of 0.16 m, 83% and 131% higher than that without vibration at the same position, respectively. [ABSTRACT FROM AUTHOR]

In this paper, we constructed the split-step θ (SS θ)-method for stochastic age-dependent population equations. The main aim of this paper is to investigate the convergence of the SS θ-method for stochastic age-dependent population equations. It is proved that the proposed method is convergent with strong order 1/2 under given conditions. Finally, an example is simulated to verify the results obtained from the theory, and comparative analysis with Euler method is given, the results show the higher accuracy of the SS θ-method. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In recent years, corn rootworm (CRW)-resistant maize events producing two or more CRW-active Bt proteins have been commercialized to enhance efficacy against the target pest(s) by providing multiple modes of action (MoA). The maize hybrid MON 87411 has been developed that produces the CRW-active Cry3Bb1 Bt protein (hereafter Cry3Bb1) and expresses a RNAi-mediated MoA that also targets CRW. As part of an environmental risk assessment for MON 87411, the potential for an interaction between the CRW-active DvSnf7 RNA (hereafter DvSnf7) and Cry3Bb1 was assessed in 12-day diet incorporation bioassays with the southern corn rootworm (SCR, Diabrotica undecimpunctata howardi). The potential for an interaction between DvSnf7 and Cry3Bb1 was evaluated with two established experimental approaches. The first approach evaluated each substance alone and in combination over three different response levels. For all three response levels, observed responses were shown to be additive and not significantly different from predicted responses under the assumption of independent action. The second approach evaluated the potential for a fixed sub-lethal concentration of Cry3Bb1 to decrease the median lethal concentration (LC50) of DvSnf7 and vice-versa. With this approach, the LC50 value of DvSnf7 was not altered by a sub-lethal concentration of Cry3Bb1 and vice-versa. In addition, the potential for an interaction between the Cry3Bb1 and DvSnf7 was tested with Colorado potato beetle (CPB, Leptinotarsa decemlineata), which is sensitive to Cry3Bb1 but not DvSnf7. CPB assays also demonstrated that DvSnf7 does not alter the activity of Cry3Bb1. The results from this study provide multiple lines of evidence that DvSnf7 and Cry3Bb1 produced in MON 87411 have independent action. [ABSTRACT FROM AUTHOR]

In this paper, a new split-step θ (SS θ ) method for stochastic age-dependent population equations with Poisson jumps is constructed. The main aim of this paper is to investigate the convergence of the SS θ method for stochastic age-dependent population equations with Poisson jumps. It is proved that the proposed method is convergent with strong order 1/2 under given conditions. Finally, an example is simulated to verify the results obtained from theory, the results show that the SS θ method has better accuracy compared to the Euler method. [ABSTRACT FROM AUTHOR]

Vortex evolution and flame propagation of supersonic reactive mixing layer with the interaction of single/double oblique shock waves are researched by employing direct numerical simulation methods. The vortex dynamics are found to be modulated by oblique shock waves, resulting in mixing enhancement of vorticity values. Notably, wider range of vortex scale distribution induced by double oblique shock waves leads to intense entrainment and nibbling process of large and small scale structures, which can remarkably increase the mixing level of hydrogen and airstreams. The analysis of vorticity transport equation indicates that compressing effects induced by shock waves are responsible for the increase of vortex strength. By tracking the vortex braid dynamical evolution process, it is revealed that local auto-ignition induced by double shock waves can accelerate the consumption of hydrogen and finally lead to high efficiency combustion. Since complex background waves are inherently present in confined space of Rocket-based Combined Cycle (RBCC) engine, the newly observed mixing enhancement mechanism for double shocked-reactive mixing layer can provide a guidance for the future design of mixing strategy using the inherent wave structures in RBCC combustor chambers. [ABSTRACT FROM AUTHOR]

Abstract: We expressed the rat Nav1.3 and Nav1.6 sodium channel α subunit isoforms in Xenopus oocytes either alone or with the rat β1 and β2 auxiliary subunits in various combinations and assessed the sensitivity of the expressed channels to resting and use-dependent modification by the pyrethroid insecticide tefluthrin using the two-electrode voltage clamp technique. Coexpression with the β1 and β2 subunits, either individually or in combination, did not affecting the resting sensitivity of Nav1.6 channels to tefluthrin. Modification by tefluthrin of Nav1.6 channels in the absence of β subunits was not altered by the application of trains of high-frequency depolarizing prepulses. By contrast, coexpression of the Nav1.6 channel with the β1 subunit enhanced the extent of channel modification 2-fold following repeated depolarization. Coexpression of Nav1.6 with the β2 subunit also slightly enhanced modification following repeated depolarization, but coexpression of Nav1.6 with both β subunits caused enhanced modification following repeated depolarization that was indistinguishable from that found with Nav1.6+β1 channels. In contrast to Nav1.6, the resting modification by tefluthrin of Nav1.3 channels expressed in the absence of β subunits was reduced by repeated depolarization. However, tefluthrin modification of the Nav1.3 α subunit expressed with both β subunits was enhanced 1.7-fold by repeated depolarization, thereby confirming that β subunit modulation of use-dependent effects was not confined to the Nav1.6 isoform. These results show that the actions of pyrethroids on mammalian sodium channels in the Xenopus oocyte expression system are determined in part by the interactions of the sodium channel α subunit with the auxiliary β subunits that are part of the heteromultimeric sodium channel complexes found in neurons and other excitable cells. [Copyright &y& Elsevier]

Abstract: In rats expression of the Nav1.7 voltage-gated sodium channel isoform is restricted to the peripheral nervous system and is abundant in the sensory neurons of the dorsal root ganglion. We expressed the rat Nav1.7 sodium channel α subunit together with the rat auxiliary β1 and β2 subunits in Xenopus laevis oocytes and assessed the effects of the pyrethroid insecticide tefluthrin on the expressed currents using the two-electrode voltage clamp method. Tefluthrin at 100μM modified of Nav1.7 channels to prolong inactivation of the peak current during a depolarizing pulse, resulting in a marked “late current” at the end of a 40ms depolarization, and induced a sodium tail current following repolarization. Tefluthrin modification was enhanced up to twofold by the application of a train of up to 100 5ms depolarizing prepulses. These effects of tefluthrin on Nav1.7 channels were qualitatively similar to its effects on rat Nav1.2, Nav1.3 and Nav1.6 channels assayed previously under identical conditions. However, Nav1.7 sodium channels were distinguished by their low sensitivity to modification by tefluthrin, especially compared to Nav1.3 and Nav1.6 channels. It is likely that Nav1.7 channels contribute significantly to the tetrodotoxin-sensitive, pyrethroid-resistant current found in cultured dorsal root ganglion neurons. We aligned the complete amino acid sequences of four pyrethroid-sensitive isoforms (house fly Vssc1; rat Nav1.3, Nav1.6 and Nav1.8) and two pyrethroid-resistant isoforms (rat Nav1.2 and Nav1.7) and found only a single site, located in transmembrane segment 6 of homology domain I, at which the amino acid sequence was conserved among all four sensitive isoform sequences but differed in the two resistant isoform sequences. This position, corresponding to Val410 of the house fly Vssc1 sequence, also aligns with sites of multiple amino acid substitutions identified in the sodium channel sequences of pyrethroid-resistant insect populations. These results implicate this single amino acid polymorphism in transmembrane segment 6 of sodium channel homology domain I as a determinant of the differential pyrethroid sensitivity of rat sodium channel isoforms. [Copyright &y& Elsevier]

Abstract: The Nav1.6 voltage-gated sodium channel α subunit isoform is the most abundant isoform in the brain and is implicated in the transmission of high frequency action potentials. Purification and immunocytochemical studies imply that Nav1.6 exist predominantly as Nav1.6+β1+β2 heterotrimeric complexes. We assessed the independent and joint effects of the rat β1 and β2 subunits on the gating and kinetic properties of rat Nav1.6 channels by recording whole-cell currents in the two-electrode voltage clamp configuration following transient expression in Xenopus oocytes. The β1 subunit accelerated fast inactivation of sodium currents but had no effect on the voltage dependence of their activation and steady-state inactivation and also prevented the decline of currents following trains of high-frequency depolarizing prepulses. The β2 subunit selectively retarded the fast phase of fast inactivation and shifted the voltage dependence of activation towards depolarization without affecting other gating properties and had no effect on the decline of currents following repeated depolarization. The β1 and β2 subunits expressed together accelerated both kinetic phases of fast inactivation, shifted the voltage dependence of activation towards hyperpolarization, and gave currents with a persistent component typical of those recorded from neurons expressing Nav1.6 sodium channels. These results identify unique effects of the β1 and β2 subunits and demonstrate that joint modulation by both auxiliary subunits gives channel properties that are not predicted by the effects of individual subunits. [Copyright &y& Elsevier]

This paper deals with the mean-square (MS) stability of the Euler-Maruyama method for stochastic differential delay equations (SDDEs) with jumps. First, the definition of the MS-stability of numerical methods for SDDEs with jumps is established, and then the sufficient condition of the MS-stability of the Euler-Maruyama method for SDDEs with jumps is derived, finally a class scalar test equation is simulated and the numerical experiments verify the results obtained from theory. [ABSTRACT FROM AUTHOR]

Abstract: We expressed rat Nav1.6 sodium channels in combination with the rat β1 and β2 auxiliary subunits in Xenopus laevis oocytes and evaluated the effects of the pyrethroid insecticides S-bioallethrin, deltamethrin, and tefluthrin on expressed sodium currents using the two-electrode voltage clamp technique. S-Bioallethrin, a type I structure, produced transient modification evident in the induction of rapidly decaying sodium tail currents, weak resting modification (5.7% modification at 100μM), and no further enhancement of modification upon repetitive activation by high-frequency trains of depolarizing pulses. By contrast deltamethrin, a type II structure, produced sodium tail currents that were ~9-fold more persistent than those caused by S-bioallethrin, barely detectable resting modification (2.5% modification at 100μM), and 3.7-fold enhancement of modification upon repetitive activation. Tefluthrin, a type I structure with high mammalian toxicity, exhibited properties intermediate between S-bioallethrin and deltamethrin: intermediate tail current decay kinetics, much greater resting modification (14.1% at 100μM), and 2.8-fold enhancement of resting modification upon repetitive activation. Comparison of concentration–effect data showed that repetitive depolarization increased the potency of tefluthrin ~15-fold and that tefluthrin was ~10-fold more potent than deltamethrin as a use-dependent modifier of Nav1.6 sodium channels. Concentration–effect data from parallel experiments with the rat Nav1.2 sodium channel coexpressed with the rat β1 and β2 subunits in oocytes showed that the Nav1.6 isoform was at least 15-fold more sensitive to tefluthrin and deltamethrin than the Nav1.2 isoform. These results implicate sodium channels containing the Nav1.6 isoform as potential targets for the central neurotoxic effects of pyrethroids. [Copyright &y& Elsevier]

Abstract: In this paper, we focus on the numerical approximation of solutions of linear stochastic delay integro-differential equations (SDIDEs). Split-step backward Euler (SSBE) method for solving linear stochastic delay integro-differential equations is derived. It is proved that the SSBE method is convergent with strong order in the mean-square sense. The condition under which the SSBE method is mean-square stable (MS-stable) is obtained. At last some scalar test equations are simulated. The numerical experiments verify the results obtained from theory. [Copyright &y& Elsevier]

Abstract: Objectives: To investigate whether the incorporation of chlorhexidine in a two-step self-etching adhesive can preserve dentin bond strengths. Methods: Different amounts of 20% chlorhexidine digluconate were added directly to the primer of Clearfil SE Bond to prepare mixtures of four different concentrations of chlorhexidine: 0.05%, 0.1%, 0.5% and 1.0%. Sixteen extracted third molars were randomly divided into 4 groups. Each group corresponded to one of the four chlorhexidine concentrations. Each of the 16 teeth was sectioned into two halves. One half was bonded with Clearfil SE Bond without chlorhexidine, and the other half was bonded with Clearfil SE Bond containing different concentrations of chlorhexidine. Specimens were stored in 0.9% NaCl containing 0.02% sodium azide at 37°C. Microtensile bond strengths were tested 24h after specimen preparation or 12 months later. The modes of fractures were examined under a stereomicroscope. Results: Twelve-month storage resulted in significant bond strength reduction of all control groups (p <0.05). When incorporated in SE Bond primer, chlorhexidine preserved dentin bond in the 0.1%, 0.5% and 1.0% chlorhexidine group (p <0.05); in the 0.05% group, there is no statistical difference of bond strength between control group and experimental group tested at the 12-month period (p >0.05). Conclusions: When incorporated in the primer of Clearfil SE Bond, chlorhexidine can preserve dentin bond as long as the concentration of chlorhexidine in the primer is higher than or equal to 0.1%. [Copyright &y& Elsevier]

Abstract: This study was designed to assess the association between visibility and air quality, and to determine whether the variations in daily mortality were associated with fluctuations in visibility levels in Shanghai, China. Mortality data were extracted from the death certificates, provided by Shanghai Municipal Center of Disease Control and Prevention, and visibility data were obtained from Shanghai Municipal Bureau of Meteorology. Air quality data (PM10, PM2.5, PM10–2.5, SO2, NO2 and O3) were obtained from Shanghai Environmental Monitoring Center. Generalized additive model (GAM) with penalized splines was used to analyze the mortality, visibility, air pollution, and covariate data. Among various pollutants, PM2.5 showed strongest correlation with visibility. Visibility, together with humidity, was found appropriate in predicting PM2.5 (R-squared: 0.64) and PM10 (R-squared: 0.62). Decreased visibility was significantly associated with elevated death rates from all causes and from cardiovascular disease in Shanghai; one inter-quartile range (8 km) decrease in visibility corresponded to 2.17% (95%CI: 0.46%, 3.85%), 3.36% (95%CI: 0.96%, 5.70%), and 3.02% (95%CI: −1.32%, 7.17%) increase of total, cardiovascular and respiratory mortality, respectively. The effect estimates using predicted PM2.5 and PM10 concentrations were similar to those assessed using actual concentrations. This is the first study in Mainland China assessing the association between visibility and adverse health outcomes. Our findings suggest the possibility of using visibility as a surrogate of air quality in health research in developing countries where air pollution data might be scarce and not routinely monitored. [Copyright &y& Elsevier]

Abstract: Voltage-gated sodium channels are important sites for the neurotoxic actions of pyrethroid insecticides in mammals. The pore-forming α subunits of mammalian sodium channels are encoded by a family of 9 genes, designated Nav1.1–Nav1.9. Native sodium channels in the adult central nervous system (CNS) are heterotrimeric complexes of one of these 9 α subunits and two auxiliary (β) subunits. Here we compare the functional properties and pyrethroid sensitivity of the rat and human Nav1.3 isoforms, which are abundantly expressed in the developing CNS. Coexpression of the rat Nav1.3 and human Nav1.3 α subunits in combination with their conspecific β1 and β2 subunits in Xenopus laevis oocytes gave channels with markedly different inactivation properties and sensitivities to the pyrethroid insecticide tefluthrin. Rat Nav1.3 channels inactivated more slowly than human Nav1.3 channels during a depolarizing pulse. The rat and human channels also differed in their voltage dependence of steady-state inactivation. Exposure of rat and human Nav1.3 channels to 100μM tefluthrin in the resting state produced populations of channels that activated, inactivated and deactivated more slowly than unmodified channels. For both rat and human channels, application of trains of depolarizing prepulses enhanced the extent of tefluthrin modification approximately twofold; this result implies that tefluthrin may bind to both the resting and open states of the channel. Modification of rat Nav1.3 channels by 100μM tefluthrin was fourfold greater than that measured in parallel assays with human Nav1.3 channels. Human Nav1.3 channels were also less sensitive to tefluthrin than rat Nav1.2 channels, which are considered to be relatively insensitive to pyrethroids. These data provide the first direct comparison of the functional and pharmacological properties of orthologous rat and human sodium channels and demonstrate that orthologous channels with a high degree of amino acid sequence conservation differ in both their functional properties and their sensitivities to pyrethroid insecticides. [Copyright &y& Elsevier]

Abstract: The agonist actions of seven commercial neonicotinoid insecticides and nicotine were studied on nicotinic acetylcholine receptors (nAChRs) expressed by neurons isolated from the three thoracic ganglia of the American cockroach, Periplaneta americana. Single electrode voltage clamp recording was used to measure agonist-induced inward currents. Acetylcholine, nicotine and all neonicotinoids tested, except thiamethoxam, caused inward currents which were blocked reversibly by methyllycaconitine, a nAChR antagonist. Based on maximum inward currents, neonicotinoids could be divided into two subgroups: (1) those with a heterocyclic ring in their electronegative pharmacophore moiety (i.e. nicotine, imidacloprid and thiacloprid) were relatively weak partial agonists causing only 20–25% of the maximum ACh current and (2) open chain compounds (i.e. acetamiprid, dinotefuran, nitenpyram, and clothiandin) which were much more effective agonists producing 60–100% of the maximum ACh current. These compounds also elicited different symptoms of poisoning in American cockroaches with excitatory responses evident for the low efficacy agonists but depressive and paralytic responses predominating for the most efficacious agonists. No correlation was observed between agonist affinity and efficacy on these nAChRs. Thiamethoxam, even at 100μM, failed to cause an inward current and showed no competitive interaction with other neonicotinoids on nAChRs, indicating that it is not a direct-acting agonist or antagonist. Despite the probable presence of multiple subtypes of nAChRs on cockroach neurons, competition studies between neonicotinoids did not reveal evidence that separate binding sites exist for the tested compounds. The size of inward currents induced by co-application of neonicotinoid pairs at equal concentration (100μM) were predominantly determined by the one with higher binding affinity as indicated by EC50 values, rather than by the one with higher binding efficacy as indicated by maximal current (I max). Agonist efficacy, but not affinity, was positively correlated with insecticidal activity. These findings indicate that: (1) agonist affinity and efficacy vary independently with neonicotinoid structure; (2) high agonist efficacy is dependent on the presence of an acyclic electronegative pharmacophore group; (3) agonist efficacy is a significant factor in the insecticidal activity of neonicotinoids to cockroaches; (4) lower efficacy compounds cause excitatory symptoms (Type A), while high efficacy compounds cause depressive/paralytic symptoms (Type B). [Copyright &y& Elsevier]

Abstract: Fluvalinate is a pyrethroid insecticide that is widely used in the control of the varroa mite (Varroa destructor), an ecto-parasite of the honeybee. Previously we identified four fluvalinate-resistance-associated mutations in the sodium channel gene of the varroa mite. One of the mutations caused a leucine (L) to proline (P) change at 1770 in the linker connecting domains III and IV of the sodium channel. Interestingly, at the position corresponding to the L to P mutation, all known insect (including honeybee) sodium channel proteins already naturally contain a P residue (e.g., P1577 in the cockroach sodium channel BgNav). To determine whether insect sodium channels are less sensitive to fluvalinate than arachnid sodium channels, we replaced P1577 with an L in a BgNav variant (BgNav1-1) and examined the sensitivity of the recombinant channel to fluvalinate. The P1577L substitution did not alter the gating properties of the BgNav1-1 channel expressed in Xenopus oocytes. However, the BgNav1-1P1577L channel was five-fold more sensitive to fluvalinate compared with the BgNav1-1 channel. These results not only implicate the L to P mutation in fluvalinate resistance in varroa mites, but also suggest a possible contribution of L1770 to the higher sensitivity of varroa mites to fluvalinate than their insect hosts. [Copyright &y& Elsevier]

Pyrethroid insecticide resistance due to reduced nerve sensitivity, known as knockdown resistance (kdr or kdr-type), is linked to multiple point mutations in the para-homologous sodium channel genes. Previously we demonstrated that two mutations (E434K and C764R) in the German cockroach sodium channel greatly enhanced the ability of the L993F mutation (a known kdr -type mutation) to reduce sodium channel sensitivity to deltamethrin, a pyrethroid insecticide. Neither E434K nor C764R alone, however, altered sodium channel sensitivity. To examine whether E434K and C764R also enhance the effect of pyrethroid resistance-associated sodium channel mutations identified in other insects, we introduced a V to M mutation (V409M) into the cockroach sodium channel protein at the position that corresponds to the V421M mutation in the Heliothis virescens sodium channel protein. We found that the V409M mutation alone modified the gating properties of the sodium channel and reduced channel sensitivity to deltamethrin by 10-fold. Combining the V409M mutation with either the E434K or C764K alone did not reduce the V409M channel sensitivity to deltamethrin further. However, the triple mutation combination (V409M, E434K and C764R) dramatically reduced channel sensitivity by 100-fold compared with the wild-type channel. These results suggest that the E434K and C764R mutations are important modifiers of sodium channel sensitivity to pyrethroid insecticides. [Copyright &y& Elsevier]

The fast and efficient mixing of fuel and oxidizers under supersonic conditions is of great importance for improving the performance of scramjet engines. The mixing process in the inner flow of a scramjet combustor is heavily inhibited by compressibility effects. In this paper, the novel strategy of plate jet actuation is proposed, and its effects on mixing augmentation are analyzed by employing numerical programs developed in-house. The fine vortex structures induced by the plate jet actuation are well captured, and the dynamic behaviors of newly observed T-shaped structures are analyzed in detail. It is found that in plate jet actuation flow, Kelvin–Helmholtz (K–H) vortices induced by K–H instability coexist with T-shaped structures induced by jet actuation instability. The interaction of adjacent T-shaped structures leads to the distortion and breakup of large-scale structures, which can obviously improve the interfaces of upper and lower streams. The distribution of the turbulence intensity along the streamwise direction suggests that with the introduction of plate jet actuation, more intense fluctuations occur in the flow. The growth process of mixing layer thickness indicates that with plate jet actuation, a sharp increase in mixing thickness can be achieved in the near flow field. The results of structural topology analysis show that upper plate jet actuation can produce structures with larger sizes, and the distortion and penetration process of these structures can entrain more upper and lower streams into the mixing region. It is suggested that the present proposed strategy is a good candidate for mixing enhancement with the application of scramjet combustors. [ABSTRACT FROM AUTHOR]

In this paper, we main investigate the almost sure exponential stability of stochastic delay Hopfield neural networks with jumps on numerical solutions. The methods we used are Euler approach and backward Euler approach. By giving some conditions of theoretical significance, we verify that not only Euler approach but also backward Euler approach is almost sure exponential stability. However, the range of application of Euler approach is smaller than that of backward Euler approach. Moreover, our main research tool is the discrete semimartingale convergence theorem. Lastly, we give an example as illustration. • The Euler method and backward Euler method are used to the model. • The almost sure exponential stability of numerical solutions is investigated. • Our main research tool is the discrete semimartingale convergence theorem. • Our main result is illustrated by an example in this paper. [ABSTRACT FROM AUTHOR]

The integrated wind risk warning model for rail transport presented has four elements: Background wind data, a wind field model, a vulnerability model, and a risk model. Background wind data uses observations in this study. Using the wind field model with effective surface roughness lengths, the background wind data are interpolated to a 30-m resolution grid. In the vulnerability model, the aerodynamic characteristics of railway vehicles are analyzed with CFD (Computational Fluid Dynamics) modelling. In the risk model, the maximum value of three aerodynamic forces is used as the criteria to evaluate rail safety and to quantify the risk level under extremely windy weather. The full model is tested for the Shanghai Metro Line 16 using wind conditions during Typhoon Chan-hom. The proposed approach enables quick quantification of real-time safety risk levels during typhoon landfall, providing sophisticated warning information for rail vehicle operation safety. [ABSTRACT FROM AUTHOR]

Background: Clinical studies on immediate implant placement for a single anterior maxillary tooth with a facial bone wall defect are rarely reported. Objective: To study the clinical outcomes of immediate implant placement combined with flap surgery, guided bone regeneration and non‐submerged healing for a single anterior maxillary tooth with a facial bone wall defect. Materials and Methods: Forty‐five patients with a single failing tooth in the anterior maxillary region showing indications for extraction combined with a facial bone wall defect were treated by means of immediate implant placement combined with flap surgery, guided bone regeneration and non‐submerged healing. During this study, the implant survival rate, soft and hard tissue dimension changes, pink aesthetic score (PAS), and patient aesthetic satisfaction were assessed at 1, 6, and 12 months post‐operatively. Results: At 12 months post‐operatively, the survival rate of 45 implants was 100%. Mesial/distal papillary level reduction and midfacial soft tissue recession were measured as 0.53, 0.41, and 0.31 mm, respectively. The thickness of facial bone reduction measured by cone beam computed tomography was 0.94, 0.80, 0.85, 0.82, 0.45, and 0.41 mm at 6 different sites around the implant. The mean PAS and patient aesthetic satisfaction were determined to be 10.58% and 93%, respectively. Conclusions: The proposed surgical procedure is a valuable treatment strategy as assessed by preliminary clinical outcomes. [ABSTRACT FROM AUTHOR]

A simple model, the Surface Temperature and Near-Surface Air Temperature (at 2 m) Model (TsT2m), is developed to downscale numerical model output (such as from ECMWF) to obtain higher-temporal- and higher-spatial-resolution surface and near-surface air temperature. It is evaluated in Shanghai, China. Surface temperature (Ts) and near-surface air temperature (Ta) submodels account for variations in land cover and their different thermal properties, resulting in spatial variations of surface and air temperature. The net all-wave radiation parameterization (NARP) scheme is used to compute net wave radiation for the surface temperature submodel, the objective hysteresis model (OHM) is used to calculate the net storage heat fluxes, and the surface temperature is obtained by the force-restore method. The near-surface air temperature submodel considers the horizontal and vertical energy changes for a column of well-mixed air above the surface. Modeled surface temperatures reproduce the general pattern of MODIS images well, while providing more detailed patterns of the surface urban heat island. However, the simulated surface temperatures capture the warmer urban land cover and are 10.3°C warmer on average than those derived from the coarser MODIS data. For other land-cover types, values are more similar. Downscaled, higher-temporal- and higher-spatial-resolution air temperatures are compared to observations at 110 automatic weather stations across Shanghai. After downscaling with TsT2m, the average forecast accuracy of near-surface air temperature is improved by about 20%. The scheme developed has considerable potential for prediction and mitigation of urban climate conditions, particularly for weather and climate services related to heat stress. [ABSTRACT FROM AUTHOR]