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With more and more high-rise building springing into the cities, the movement of pedestrians on stairs is of great importance for the evacuation of these facilities; the topic of human performance on stairs has attracted a lot of researcher to study. However, there is still a lack of analysis of specific situations, such as mid-landing and merging behaviors. In this paper we employ a modified version of the Optimal Steps Model, modified by taking block-based floor field into consideration under open boundary conditions, to reproduce movement at mid-landing and study performance of occupants in stairwell. Movements on this kind of stairs are simulated and studied with the help of extended model: achieved results are in accord with previous research in respect of specific flow and fundamental diagram. Lane formations on stairs come into being before mid-landing area through simulations. Furthermore most people reach at the mid-landing by the outside stairs at higher density due to more space and less force from other agents, which is induced that outside of the stairs is good for evacuation. At last the model is implemented to study the effect of stairs geometry on merging behaviors, and it is found when corridor is connected to the landing opposite to the incoming stairs, this structure is biased in favor of occupants from stairs. The work in this paper is intended to better understand movement during stair evacuations and develop a technical foundation for codes and standards requirements as well as egress modeling techniques. [ABSTRACT FROM AUTHOR]

Movements on stairs have attracted a lot of researchers to study in order to help evacuate as fast as possible. However, there has been much less awareness for this issue on preference for stairs and human behaviors under different illuminations. Experiments were carried out to study the human movement characteristics and human behavior performance when pedestrians walked down stairs alone. By extracting the positions of pedestrians on cameras, preference and movement characteristics were studied and discussed, and it is found that pedestrians would like to choose inner side stairs rather than outside stairs when stairs were divided into 2 parts. Besides, some conclusions can be drawn when stairs are divided into three components: when entering into sections under conditions of 100% and 12% illumination, both females and males have a preference for middle areas when the width of stairs is about 130 cm, but the preference would change with illumination conditions. Furthermore, when the illumination is 0%, the mean velocity is 0.50 ± 0.14 m/s. In addition, the usability to handrails helps to reduce time taken on interfaces or mid-landings. The results help to better understand movement during stair evacuations and are important for constructing or improving evacuation models. [ABSTRACT FROM AUTHOR]

The recent rapid development of distributed PV (photovoltaic) industry in China closely ties to the relevant policies support. This paper reviews some main points of relevant policies including financial support, technology innovation and management improvement. Scenario analysis both in residential sectors and industrial and commercial sectors are taken into account. We calculate IRR (internal rate of return) and static payback period of a specific distributed PV system in China's five cities located in different resource areas. In order to provide a realistic reference for investors, the historical data from real projects are used to calculate the generating capacity. The impacts of relevant policy variables such as subsidies, benchmark price, electricity price and tax on economic performance of distributed PV system are discussed. The results show that distributed PV system with high generation efficiency has produced good economic benefit in both two scenarios under China's current policies. The current policy instruments on distributed PV industry are efficient. At the end of the paper, policy recommendations are offered as references for the government. [ABSTRACT FROM AUTHOR]

InGaN light-emitting diodes (LEDs) with InGaN-GaN quantum barriers of gradually decreasing indium concentration along the growth direction are proposed to be used. In the proposed structure, simulation results show that the holes are widely distributed in the active region due to the larger hole injection/transportation efficiency by reducing the effective potential height for holes and the radiative recombination rate is efficiently improved, which leads to the significant enhancement of light-output power and internal quantum efficiency (IQE) over the conventional LED with GaN barriers. Moreover, the optical performance is further improved when the graded InGaN/GaN supperlattice (SL) is introduced between the multiple quantum wells (MQWs) and p-AlGaN electron blocking layer (EBL) in our designed LED structure, permitting more freedom for the optimization. [ABSTRACT FROM AUTHOR]

Abstract: The advantages of an InGaN light-emitting diode (LED) structure with Mg–Si-codoped barriers are studied numerically in this paper. Energy band diagrams, carrier concentrations in the active region, radiative recombination rates in the quantum wells (QWs), light-current performances, and internal quantum efficiency (IQE) are investigated. Simulation results suggest that by employing the Mg–Si-codoped barriers, the light-output power and IQE are more significantly improved than LEDs with step-Si-doped barriers when compared with the conventional LEDs with wholly Si-doped barriers, due to modified band diagrams, which are favorable for improvement of hole injection efficiency. Moreover, simulation also indicates that the optical performance can be further improved if the Si doping concentration of quantum barriers (QBs) is decreased gradually along the growth direction for the LED with Mg–Si-codoped barriers. [Copyright &y& Elsevier]

The advantages of InGaN-based light-emitting diodes (LEDs) with InGaN/GaN superlattice (SL) and graded-composition InGaN/GaN SL interlayers in the last-barrier/EBL space are studied numerically. The electrostatic field, energy band diagrams, carrier concentrations, radiative recombination rate, light-current-voltage (L-I-V) performances, and internal quantum efficiency (IQE) are investigated. Simulation results show that the light-output power and IQE are both enhanced compared to the conventional LED due to the appropriately modified energy band diagrams, which are favorable for the improvement in hole injection efficiency and electron blocking capability, especially for the LED with graded-composition InGaN/GaN SL interlayer. [ABSTRACT FROM AUTHOR]

Abstract: The structural properties, crystalline quality and surface morphology of CdTe thin films without and with a ZnTe buffer layer grown on (001)GaAs by molecular beam epitaxy (MBE) have been studied. CdTe thin film directly prepared on GaAs substrate displays (111) orientation with an island growth mode, whereas the CdTe epilayers with a ZnTe buffer are (001)-oriented single-crystalline film with a two-dimensional (2D) growth mode. The morphology and surface root-mean-square (RMS) roughness of CdTe epilayers are also dramatically improved by using a ZnTe buffer. Furthermore, it is suggested that the high-temperature (HT) ZnTe buffer grown at 360 °C is more efficient for enhancing CdTe structural quality than the low-temperature (LT) one at 320 °C. The CdTe epilayer on the HT-ZnTe buffer shows a narrower full-width at half-maximum (FWHM) of double-crystal X-ray rocking curve (DCXRC) for (004) reflection and a smaller RMS roughness. [Copyright &y& Elsevier]

Abstract: Lymphatic vessels guide interstitial fluid, modulate immune responses by regulating leukocyte and antigen trafficking to lymph nodes, and in a cancer setting enable tumor cells to track to regional lymph nodes. The aim of the study was to determine whether primary murine lymphatic endothelial cells (mLECs) show conserved vascular endothelial growth factor (VEGF) signaling pathways with human LECs (hLECs). LECs were successfully isolated from murine dermis and prostate. Similar to hLECs, vascular endothelial growth factor (VEGF) family ligands activated MAPK and pAkt intracellular signaling pathways in mLECs. We describe a robust protocol for isolation of mLECs which, by harnessing the power of transgenic and knockout mouse models, will be a useful tool to study how LEC phenotype contributes to alterations in lymphatic vessel formation and function. [Copyright &y& Elsevier]

Abstract: CdSe epilayers were grown on GaAs(001) substrates by molecular beam epitaxy (MBE) in a wide range of VI/II beam-equivalent-pressure (BEP) ratio from 1.1 to 8.5. X-ray diffraction (XRD) θ–2θ scan reveals all the CdSe samples possess cubic zinc blende structure with (001) orientation. The film grown at a low VI/II ratio of 1.1 has rough surface with a three-dimensional (3D) growth mode, while two-dimensional (2D) growth can be established under Se-rich conditions at higher Se/Cd BEP ratios over 4.4. The growth rate increases monotonically with the VI/II ratio and becomes saturated when the ratio is raised to 8.5. The sample grown at a VI/II ratio of 8.5 shows the narrowest full-width at half-maximum (FWHM) of X-ray rocking curve (XRC) for (004) reflection. No near-band-edge (NBE) emission of CdSe is observed for the sample prepared at a low ratio of 1.1. The NBE emission from cubic CdSe at around 1.67eV appears and its intensity is markedly enhanced by elevating the VI/II ratio. It is suggested that CdSe epilayer with good structural and optical properties can be prepared under a large VI/II BEP ratio. [Copyright &y& Elsevier]

Abstract: ZnTe epilayers were grown on GaAs(001) substrates by molecular beam epitaxy (MBE) at different VI/II beam equivalent pressure (BEP) ratios (R VI/II) in a wide range of 0.96–11 with constant Zn flux. Based on in situ reflection high-energy electron diffraction (RHEED) observation, two-dimensional (2D) growth mode can be formed by increasing the R VI/II to 2.8. The Te/Zn pressure ratios lower than 4.0 correspond to Zn-rich growth state, while the ratios over 6.4 correspond to Te-rich one. The Zn sticking coefficient at various VI/II ratios are derived by the growth rate measurement. The ZnTe epilayer grown at a R VI/II of 6.4 displays the narrowest full-width at half-maximum (FWHM) of double-crystal X-ray rocking curve (DCXRC) for (004) reflection. Atomic force microscopy (AFM) characterization shows that the grain size enlarges drastically with the R VI/II. The surface root-mean-square (RMS) roughness decreases firstly, attains a minimum of 1.14nm at a R VI/II of 4.0 and then increases at higher ratios. It is suggested that the most suitable R VI/II be controlled between 4.0 and 6.4 in order to grow high-quality ZnTe epitaxial thin films. [Copyright &y& Elsevier]

Abstract: ZnTe thin films have been grown on GaAs(001) substrates at different temperatures with constant Zn and Te beam equivalent pressures (BEPs) by molecular beam epitaxy (MBE). In situ reflection high-energy electron diffraction (RHEED) observation indicates that two-dimensional (2D) growth mode can be established after around one-minute three-dimensional (3D) nucleation by increasing the substrate temperature to 340°C. We found that Zn desorption from the ZnTe surface is much greater than that of Te at higher temperatures, and estimated the Zn sticking coefficient by the evolution of growth rate. The Zn sticking coefficient decreases from 0.93 to 0.58 as the temperature is elevated from 320 to 400°C. The ZnTe epilayer grown at 360°C displays the narrowest full-width at half-maximum (FWHM) of 660arcsec from (004) reflection in double-crystal X-ray rocking curve (DCXRC) measurements. The surface morphology of ZnTe epilayers is strongly dependent on the substrate temperature, and the root-mean-square (RMS) roughness diminishes drastically with the increase in temperature. [Copyright &y& Elsevier]

The deflagration evolution of premixed CH 4 /H 2 /air mixtures in sudden expansion duct was investigated by explosion experiments. Based on the previous research on different obstacle widths and spaces, the effect of various hydrogen blend ratios and the fuel equivalence ratios on deflagration evolution were further investigated. The results showed that the flame inversion is pronounced for hydrogen blend greater than 40% and the fuel equivalence ratio no less than 1, which is closely related to the increased flame propagation speed. Besides, the results showed that the overpressure in the chamber increases as the hydrogen blend ratio increases. Moreover, the maximum pressure (P red) and the maximum pressure rise rate ((dP/dt) max) are observed at the fuel equivalence ratio for the low hydrogen blend ratio, however, for the high hydrogen blends, the maximum values are observed at slightly higher fuel equivalence ratios. Furthermore, a model was developed to predict the maximum overpressure under conditions of sudden expansion and half-open ducts. • The effect of sudden expansion duct on the deflagration evolution was investigated. • The equivalence ratio for obtaining the maximum pressure is close to 1.2 at high hydrogen blend ratio. • As The hydrogen blend ratio increases, the second explosion pressure becomes high. • The addition of obstacles and hydrogen can promote the flame to inverse. • The pressure prediction model suited for the sudden expansion duct is corrected. [ABSTRACT FROM AUTHOR]

In this paper, we conduct a single-file experiment on stairs under two motivations, namely normal walking condition and fast walking condition at various densities. Totally four types of movements are analyzed and compared, namely normal walking-ascending movement, normal walking-descending movement, fast walking-ascending movement and fast walking-descending movement. Compared with the normal walking condition, in fast walking condition pedestrians move with higher velocity, which can be clearly observed in color-coded trajectories and time–space diagrams. We further make pairwise comparisons of density–velocity and headway–velocity relations for four types of movement, and critical parameters such as minimum headway, adaptation time, critical headway and free-flow velocity are extracted. It is found that the adaptation time is negatively correlated with free-flow velocity, indicating that pedestrians under higher movement motivation have a stronger ability to adapt their velocities. Besides, the values of time to collision are smaller for ascending movement than descending movement, apart from those at high density. In addition, we also analyze the following behavior through the relation between velocities of two adjacent pedestrians. The correlation analysis indicates that velocities are most correlated in fast walking-descending movement, and least correlated in normal walking-ascending movement. It is hoped that our study can be useful for the modeling of stair motion and the design of building stairway. [ABSTRACT FROM AUTHOR]

With more and more large-scale activities conducted in the cities, the issue how to evaluate risk in activities has attracted a lot of researchers to investigate. Bidirectional flow can be commonly observed in mass gathering events, therefore it is of great importance to gain deeper insights into this kind of movement. In this manuscript, three kinds of entropy are introduced and used in order to measure the disorder and risk of bidirectional movement, namely position entropy, angle entropy and speed entropy. Larger entropy means more uncertainty and risk in the system. Entropy is applied in two counter-flow experiments in order to describe the level of randomness. It is found when the number of lanes transits from 4 to 3, there is a sharp increase in respect of entropy because occupants compete for the space to move forward. In order to testify the effect of position entropy, another scenario is calculated and small position entropy means steady bidirectional movement, which is in accordance with the realistic movement in experiment. The speed entropy is measured and similar trend can be observed by comparing with speed variance proposed by previous researchers. Furthermore, angle entropy is also investigated and relation between angle entropy and density is obtained. The proposed entropy can help quantify randomness of counter-flow movement and be beneficial forfor the managers to better deal with potential abnormal activities. [ABSTRACT FROM AUTHOR]

Clustering data by identifying a subset of representative border points is essential for detecting dataset structures and processing complicated messages in data. Such border points can be found by exactly choosing an initial subset of data points, and then iteratively refining it with fuzzy membership values; however, this only works well if the fuzzy rule choice is close to a good solution. We propose a clustering algorithm, known as affine fuzzy neuron (AFN), which measures the relations of linear memberships between border points and the cluster centers of points within a subset. Fuzzy memberships of border points are calculated until their corresponding clusters gradually emerge. AFN exploits a typical feature of real-life biological gene clusters, like gene expression measurements, from microarrays or single-cell RNA-Seq. That is, genes sharing the same expression profile belong to different clusters with diverse functions. We hypothesize that these genes only appear at cluster boundaries and a subset of genes comprises points with similar expression profiles but entirely different functions. We use AFN to cluster several test cases and analyze various gene expression datasets. The proposed clustering algorithm is a flexible modeling framework that increases accuracy and combines border regions across multiple clusters while remaining computationally feasible. [ABSTRACT FROM AUTHOR]

This paper investigates turning characteristics of bidirectional pedestrian flows with controlled experiment under laboratory condition. Compared with straight walking bidirectional flow, pedestrian lane width of turning bidirectional flow narrows after turning, which indicates that pedestrians are suppressed a lot by the opposite flow when turning. The fundamental diagrams are almost the same in the density range between 1.5 ped/m2 and 3.2 ped/m2 for the straight and turning bidirectional flows. However, the density, velocity and specific flow profiles of the turning bidirectional flow are different from those of straight bidirectional flow. The density in the turning area for θ = 45° scene is larger compared with that for θ = 90° and 135° scene, and the maximal local density reaches 6 ped/m2. The region where pedestrian lanes are formed by pedestrians leaving the turning area has relatively large values of velocity and specific flow. Furthermore, position-velocity relation and the cumulative distribution of time lapse in the corridor are investigated. The results obtained can offer more insights into pedestrian dynamics of the turning bidirectional flow. • A controlled experiment on bidirectional pedestrian flows through angled corridors is conducted. • Pedestrian lane width will be narrowed due to the constraint of the opposite flow after turning. • The difference of fundamental diagrams for different turning angles only exists at low and high density. • The spatiotemporal profile for the turning bidirectional flow is less evenly distributed. • Pedestrian velocity before turning usually keeps low and will increase after turning. [ABSTRACT FROM AUTHOR]

Drug resistance remains a major challenge for anticancer treatment, and one of the major mechanisms of drug resistance is the overexpression of drug efflux transporters in cancer. A new approach for defeating drug resistance is the use of a co-delivery strategy that utilizes small interfering RNA (siRNA) to silence the expression of efflux transporters together with a suitable anticancer drug for drug-resistant cells. In this work, multifunctional graphene capable of integrating multiple functions in one system was employed as a novel co-delivery system for siRNA and doxorubicin (Dox), as well as for the controlled release of intracellular pH-triggered and heat-triggered Dox. Additionally, it was used as a synergistic therapy based on the photothermal effect of graphene oxide (GO) under near-infrared (NIR) irradiation and the chemotherapeutic effect of Dox. The nanocomplex exhibited high drug and siRNA loading. Furthermore, the dual delivery of siRNA and Dox by folic acid (FA)-conjugated polyethylenimine-modified PEGylated nanographene (PPG-FA/siRNA/Dox) exhibited a satisfactory gene silencing effect as well as efficient intracellular delivery of Dox. Thus, Dox could access the nucleus and induce greater cytotoxicity compared with siRNA-absent delivery systems. Significantly, under irradiation, the combined treatment showed more synergistic effect for overcoming drug resistance compared with chemotherapy effect alone. [ABSTRACT FROM AUTHOR]

Evacuation in high-rise buildings has attracted a lot of researchers to study human performance during evacuation process especially since the “911” disaster. However, there is little research studying the effect of initial distribution ratios among the different floors and the impact of sub-optimal illumination on merging behaviors between different pedestrian flows. In this paper, some experiments are presented in a real staircase to analyze the human behavior at the merging area. Through extracting movement characteristics from recorded video, the data about human movement performance is obtained and studied. It is found that when inflows from upstairs are opposite to inflows from stairs at the merging area, the geometrical structure seems to be biased in favor of occupants from floors and merging behaviors negatively affect the walking speed of pedestrians from upper floors. Then it is found there are three phases (free movement, extended zipper effect and following movement) during merging process. Furthermore, there is a relationship between the time pedestrians enter mid-landing and overall speed: speeds of pedestrians decrease and stabilize as the arrival time to the merging area grows. The merging behaviors are influenced by illumination and initial distribution ratios: in the experimental conditions, initial occupants from floors are more than that from upstairs, contributing high density at the merging area regardless of illumination. The results help to better understand the overall movement during stair evacuations and provide valuable data to validate and improve evacuation models. [ABSTRACT FROM AUTHOR]

This paper presents a numerical model that investigates the characteristics of flow, heat, and mass transfer on downward flame propagation in the discontinuous region of solid fuel. Simulations were carried out for various discontinuous distances to analyze the morphology of the flame front and the competition between the "jump" of flame spread and heat transfer from the flame to the unburned area. The results demonstrate that there is a "jump" in the flame propagation in the discontinuous zone, with the flame front exhibiting a defined "acute angle" that undergoes a process from large to small during the flame spreading in the discontinuous area and deflects towards the discontinuous area of the material. The temperature in the discontinuous zone reaches a peak, and the average flame spread rate initially increases and then decreases with the increase of discontinuity distance until the flame spread stops. The study provides valuable insights into the growth and development of fires involving discretely distributed combustible materials. [ABSTRACT FROM AUTHOR]

Presents a study which investigated the spectral response of two-dimensional gratings for quantum well infrared photodetectors. Influence of grating constant variation on coupling efficiency; Methodology for the evaluation of diffraction properties; Comparison of coupling efficiency with measured detectivity.

A novel real-time control method, named SF-B control method, was proposed and a comprehensive numerical simulation study was conducted for feasibility analysis. The simulation utilized a combination of Python scripts and FDS. The SF-B control method incorporates automatic detection and localization of the fire source, and the existing ventilation velocity is corrected based on the real-time state of motion of smoke fronts and the back-layering length. The control logic of the SF-B control method was described in detail, and the criterion for determining stabilization was provided. After a comparison with PID control method, scenarios involving random constant HHRs, random fire locations and variable HRR were set up for separate simulations, and the results were compared with previous experimental findings. The outcomes demonstrate that the fluctuation of the SF-B control method is only about 1/10 of that of the PID control method, and the control performance is not significantly influenced by the HRR or fire location. It shows a more powerful control ability on smoke back-layering in scenarios involving variable HRR. This method exhibits excellent compatibility with different fire conditions, showcasing high ventilation control efficiency, robust control capabilities, and delivering reliable control results. [ABSTRACT FROM AUTHOR]

• A novel mechanical board-coupled ventilation shaft was introduced. • Smoke extraction pattern would shift due to the coupling-effect between the shaft and the fan. • A model to analyze the dynamic of the synergistic smoke extraction was established. • The novel shaft can significantly improve both smoke and heat extraction performance. Ventilation shafts are widely equipped in extra-long road tunnels. Due to the plug-holing phenomenon, it may be impossible to improve smoke extraction performance solely by increasing extraction velocity in a traditional ventilation shaft. Taking reference from practices in mine ventilation shafts, a novel mechanical board-coupled ventilation shaft (MBCS) was introduced. A total of 120 experiments in a 1:20 reduced-scale tunnel model were conducted to validate the effectiveness of the novel shaft. The effects of shaft height, board location, and extraction velocity were investigated, and the interaction dynamic mechanism of synergistic smoke extraction between fan-driven and shaft-driven was revealed. The results indicate that the novel MBCS can achieve better smoke extraction performance as the extraction velocity increases. Besides, compared to the traditional MBCS in our previous study, the smoke extraction efficiency of the novel MBCS improves by 19.8 %, the heat extraction performance improves by 75.7 %. Moreover, based on theoretical and dimensional analysis, a model to analyze the dynamic mechanism of synergistic smoke extraction was established, which may provide positive insights for smoke control and extraction design both in extra-long road tunnels and mine ventilation shafts. [ABSTRACT FROM AUTHOR]

Many countries have been implementing various control measures with different strictness levels to prevent the coronavirus disease 2019 (COVID-19) from spreading. With the great reduction in human mobility and daily activities, considerable impacts have been imposed on the global air transportation industry. This study applies a hybrid SARIMA-based intervention model to measure the differences in the impacts of different control measures implemented in China, the U.S. and Singapore on air passenger and air freight traffic. To explore the effect of time span for the measures to be in force, two scenarios are invented, namely a long-term intervention and a short-term intervention, and predictions are made till the end of 2020 for all three countries under both scenarios. As a result, predictive patterns of the selected metrics for the three countries are rather different. China is predicted to have the mildest economic impact on the air transportation industry in this year in terms of air passenger revenue and air cargo traffic, provided that the control measures were prompt and effective. The U.S. would suffer from a far-reaching impact on the industry if the same control measures are maintained. More uncertainties are found for Singapore, as it is strongly associated with international travel demands. Suggestions are made for the three countries and the rest of the world on how to seek a balance between the strictness of control measures and the potential long-term industrial losses. [ABSTRACT FROM AUTHOR]

Based on theoretical studies of transport properties in InAsSb-based quantum well heterostructures, we propose a material design for InAsSb quantum well with AlInSb barrier. Variation of electron mobility and two-dimensional electron gas concentration in AlyIn1-ySb/InAs1-xSbx heterostructures over the compositional range of which InAsSb is fully strained to AlInSb are investigated, where impact from dislocation scattering could be minimized. In comparison with InAs and InSb based quantum well heterostructures, InAsSb is advantageous in achieving the highest electron mobility despite of alloy disorder scattering. The maximum mobility of 37 000 cm2/V s is attainable in 15 nm InAs0.2Sb0.8 quantum well with Al0.24In0.76Sb barrier and there is great potential for further improvement. Our InAsSb based quantum well heterostructure is proved to be a robust structure for high-speed applications. [ABSTRACT FROM AUTHOR]

A distinctive method is used to achieve transverse-mode control by building and integrating a tunable liquid crystal (LC) mode filter on top of traditional vertical-cavity surface-emitting lasers (VCSELs). An LC cell is fabricated by injecting a type of nematic LC material (E7) in an annular groove patterned by SiO2. By electrically tuning the refractive index of the LC, a spatially dependent reflectivity profile can be achieved and optimized, which directly influences the threshold modal gain of each transverse mode provided by oxide-confined VCSELs. The flexible and accurate control performance of the LC mode filter structure have been demonstrated by the simulation results and our analysis. This design is a completely novel method to realize VCSELs with an accurate and real-time controllable transverse-mode, and it will probably play a significant role in the future. [ABSTRACT FROM AUTHOR]

The high electron mobility transistor (HEMT)-based biosensors are highly competitive in the ultimate application of portable and point-of-care testing. Herein, we have demonstrated highly sensitive and real-time detection of cardiac troponin I (cTnI), a biomarker for the diagnosis of acute myocardial infarction (AMI) using AlGaAs/GaAs HEMT-based biosensors. The device has achieved a lower detection limit of 1 pg/ml in the buffer solution and less than 30 s response time, which demonstrated significant promise in the early diagnosis and screening of AMI. In addition, our results are consistent with the enzyme-linked immunosorbent assay according to the AMI patient's blood test results. Furthermore, by comparing the two HEMT structures, we also calculated the equilibrium dissociation constant (KD) of the cTnI and cTnI antibody and analyzed the sensing mechanism. The results show that this method is very promising for early diagnosis of AMI. [ABSTRACT FROM AUTHOR]

Theoretical studies of transport properties in InAsSb-based quantum well heterostructures are presented. The concentration of two-dimensional electron gas is calculated self-consistently from our improved Schrödinger-Poisson model by taking into account of nonparabolicity effect and strain effect, and the results are used to obtain the electron mobility. All major scattering mechanisms by acoustic phonon, polar optical phonon, remote ionized impurity, background impurity, interface roughness, and alloy disorder have been included in our calculation. Particularly, dislocation scattering, intrasubband scattering, and intersubband scattering, which are always neglected in heterostructure systems, are considered. The calculated electron mobility is proved to be in good agreement with the experimental data for modulation-doped AlSb/InAsSb quantum well heterostructures. With a view to optimize the transport property, quantum well width, spacer thickness, barrier thickness, and remote doping concentration for AlSb/InAsSb heterostructures are discussed to examine their effect on total electron mobility. Intrinsic electron mobility exceeding 40 000 cm2/Vs is predicted at 300 K for AlSb/InAs0.4Sb0.6 heterostructures which is dominated by a combination of polar optical phonon scattering, remote ionized impurity scattering, and interface roughness scattering. [ABSTRACT FROM AUTHOR]

We present a theoretical study of electron mobility in modulation-doped AlSb/InAs quantum wells. The theory also accounts for the nonparabolicity effect. All major scattering mechanisms, including scattering by deformation potential and piezoelectric acoustic phonons, polar optical phonons, ionized impurities, and interface roughness, have been included in our calculations. The low field transport properties of the two dimensional electron gas (2DEG) in the AlSb/InAs quantum wells are studied as a function of temperature, quantum well width, and spacer width and strategies for optimizing the 2DEG mobility are discussed. Depending on the quantum well parameters, the high-mobility limit in this quantum well structure may be determined by either ionized impurity scattering or interface-roughness scattering. The calculated 2DEG mobilities are in very good agreement with the reported experimental data for modulation-doped AlSb/InAs quantum wells. [ABSTRACT FROM AUTHOR]

A reverse-channel 4H-SiC trench gate metal-oxide-semiconductor field-effect transistor (UMOSFET) (RC-MOS) is proposed in this article. The RC-MOS is demonstrated to have low specific ON-resistance (RON,sp) by numerical simulation. The trench oxide in the RC-MOS is fully protected by the n+ source, the p-shield, and the p-base regions. Thus, a reduced trench corner field far below 3 MV/cm can be achieved in both the OFF- and ON-state. Furthermore, the gate-to-drain charge (QGD) of the RC-MOS is 33 nC/cm2, which is much lower than that of the dual buffer layer MOSFET (DB-MOS), owing to little overlap between the gate and drain electrodes. Consequently, the RC-MOS exhibits the superior figures of merit QGD × RON,SP = 82m Ω ⋅ nC. Due to the low reverse transfer capacitance and gate charges in the RC-MOS, the total switching loss of $570~μJ/cm2 is decreased by 64.5% in comparison to that of the DB-MOS. These superior properties show that the proposed UMOSFET can be a good candidate for further improvements in the gate oxide reliability and high-frequency performance of SiC MOSFETs. [ABSTRACT FROM AUTHOR]

Interfacial properties and energy-band alignment of annealed AlN dielectric films on Si-face 4° off-axis 4H–SiC substrates were characterized and demonstrated by x-ray photoelectron spectroscopy (XPS) and current-electric field (I–E) measurements. The XPS results reveal that the Al–O bonds and the silicon suboxides can convert into more stable Al–N bonds and Al–O–Si bonds at the AlN/4H–SiC interface under 1000 °C annealing. The variations in both oxygen-rich composition and the crystallinity in AlN make annealing-dependent conduction band offsets of as-deposited and annealed AlN/4H–SiC to be 1.36 eV and 1.20 eV, respectively. Meanwhile, I–E measurements separately yield the occurrence of the Fowler–Nordheim (FN) tunneling and space-charge-limited conduction in as-deposited and annealed metal-insulator-semiconductor capacitors, corresponding to lower barrier heights of 0.92 eV and 0.54 eV, respectively. The reason for the energy-band shift between I–E derivations and the XPS results was analyzed and demonstrated together. These results can provide considerable insight into the energy-band alignment of AlN as gate dielectric or passivation layers on 4H–SiC based devices. [ABSTRACT FROM AUTHOR]

Diluted magnetic nonpolar GaN:Cu films with ferromagnetic properties up to 380 K have been fabricated by implantation of Cu ions into nonpolar a-plane GaN films and a subsequent thermal annealing process. The nonpolar GaN:Cu films exhibit a strong saturation magnetization about 1.54 μB/Cu atom, while polar GaN:Cu films can only show a weak saturation magnetization of 0.36 μB/Cu atom. Moreover, according to the x-ray photoelectron spectroscopy results, the stronger ferromagnetism of nonpolar GaN:Cu films may be resulted from the higher Cu incorporation efficiency in nonpolar GaN films. [ABSTRACT FROM AUTHOR]

Sapphire substrates were patterned by a chemical wet etching technique in the micro- and nanoscale to enhance the light output power of InGaN/GaN light-emitting diodes (LEDs). InGaN/GaN LEDs on a pyramidal patterned sapphire substrate in the microscale (MPSS) and pyramidal patterned sapphire substrate in the nanoscale (NPSS) were grown by metalorganic chemical vapor deposition. The characteristics of the LEDs fabricated on the MPSS and NPSS prepared by wet etching were studied and the light output powers of the LEDs fabricated on the MPSS and NPSS increased compared with that of the conventional LEDs fabricated on planar sapphire substrates. In comparison with the planar sapphire substrate, an enhancement in output power of about 29% and 48% is achieved with the MPSS and NPSS at an injection current of 20 mA, respectively. This significant enhancement is attributable to the improvement of the epitaxial quality of GaN-based epilayers and the improvement of the light extraction efficiency by patterned sapphire substrates. Additionally, the NPSS is more effective to enhance the light output power than the MPSS. [ABSTRACT FROM AUTHOR]

Organic light emitting diodes using a mixed layer of electron acceptor 3, 4, 9, 10 perylenetetracarboxylic dianhydride and electron donor copper phthalocyanine (PTCDA:CuPc) on indium tin oxide (ITO) anodes were fabricated. The device properties were found to be strongly dependent on the thickness of the PTCDA:CuPc film: both the power efficiency and the driving voltage of the device were optimized with a thickness of PTCDA:CuPc ranging from 10 to 20 nm. As compared to the conventional ITO/CuPc hole injection structure, the ITO/PTCDA:CuPc hole injection structure could remarkably enhance both the luminance and the power efficiencies of devices. A mechanism of static-induced, very efficient hole-electron pairs generation in mixed PTCDA:CuPc films was proposed to explain the experimental phenomena. The structural and optical properties of PTCDA:CuPc film were examined as well. [ABSTRACT FROM AUTHOR]

Temperature dependences of the polarized Raman scattering spectra in the backscattering configuration of the nonpolar a-plane (or [1120]-oriented) GaN thin film are analyzed in the range from 100 to 570 K. The nonpolar a-plane GaN film is grown on an r-plane [or (1102)-oriented] sapphire substrate by metal organic chemical vapor deposition. The spectral features of the Raman shifts, intensities, and linewidths of the active phonons modes A1(TO), E1(TO), and E2(high) are significantly revealed, and corresponding temperature coefficients are well deduced by the empirical relationships. With increasing the measurement temperature the Raman frequencies are substantially redshifted and the linewidths gradually broaden. The compressive-strain-free temperature for the nonpolar a-plane GaN film is found to be at about 400 K. Our studies will lead to a better understanding of the fundamental physical characteristics of the nonpolar GaN film. [ABSTRACT FROM AUTHOR]

With the increasing application of SiC, it has become increasingly evident that high hardness and difficulty in etching are major issues. Wet etching is a popular method due to its low cost and convenience. Electrochemical (EC) etching is one such wet-etching technique used for removing SiC material. Currently, most studies on EC focus on constant voltage mode with few investigations into constant current mode operation. In this study, we investigate the EC etching of 4H–SiC under a constant current regime by analyzing basic reaction processes through changes in voltage curves while studying large-period pulse etching modes as well as examining how different magnitudes of electric currents affect the process outcome. We hope our systematic research will contribute towards advancing knowledge about using EC techniques under continuous-current conditions thereby promoting wider application possibilities for this type of surface modification approach. • In constant current mode, the voltage first decreases and then increases. • There is always a thin oxide layer on the surface during the etching process. • Both anodization and oxide desorption processes are localized. • The etch rate has a quadratic function relationship with the current density. [ABSTRACT FROM AUTHOR]

Abstract We have investigated and compared the influence of annealing temperature on composition and interfacial properties of AlN thin films deposited on 4H-SiC substrates by atomic layer deposition using trimethylaluminum (TMA) and ammonia as precursors at 400 °C. Those as-deposited films were annealed by rapid thermal annealing at 700 °C, 800 °C, 900 °C and 1000 °C for 1 min in N 2 atmosphere, respectively. As the annealing temperature increased, the thickness of AlN films decreased and the refractive index increased due to the densification and compositional changes in the films. The roughness of films decreased as the films became denser after annealing. In addition, the deposited AlN film is not amorphous structure and the intensity of the (0002) diffraction of the AlN films enhanced in the annealed films. N-O-Al bond broke down and the intensity of Al-N bond increased with the increase of annealing temperature. Moreover, the interface between AlN and SiC was mainly a transition layer containing Al-O-Si, and the intensity of Al-O-Si was enhanced after annealing at 1000 °C. And the annealing process reduced the negative charge and the density of interface trap of the AlN annealed film in the MIS capacitor. These results provide a significant reference for AlN as a gate dielectric for SiC-based MOS devices in the future. [ABSTRACT FROM AUTHOR]

Computer simulation for pedestrian dynamics is at the same time an application area in which research has completed its cycle and an active and lively research context in which contributions from different disciplines still produce advancements on the state of the art. The study of effects of the presence of groups in the simulated population is object of growing interest in the community. While previous results have started to investigate the phenomenon, implying conflicting tendencies for pedestrians, mechanisms for the flexible management of cohesion among group members are still investigated both in continuous and discrete modelling efforts. The present effort is aimed at extending previous modelling efforts, preserving and improving the capability to generate overall plausible aggregated dynamics, while at the same time improving the precision in the microscopic group dynamics, with particular attention to the shape of dyads. The paper presents validated results based on empirical data from a controlled experiment, also discussing qualitative results in different common situations (bends and bottlenecks). [ABSTRACT FROM AUTHOR]

In this paper, the dual-pulsed transient electroluminescence (EL) characteristics in organic light-emitting diodes (OLEDs) with NPB/Alq 3 multiple quantum-well (MQW) structures are investigated in detail. The threshold duty-ratio ( δ th ) is found in the NPB/Alq 3 MQW devices, whereas the bilayer NPB/Alq 3 device does not appear. Then the δ th in single and double wells are 0.68 and 0.35, respectively. In the single QW device, the second pulsed intensity will be greater than the first pulsed strength after reaching the δ th , while the double QW device is the opposite. This is due to the charge diffusion effect in the Alq 3 well layer near the cathode of MQW devices. As the well numbers increase, it is different from the fall time remaining almost constant, the transient delay time will increase linearly, which is totally caused by the recombination position of excitons. [ABSTRACT FROM AUTHOR]

• The growth of 4H-SiC using TCS in the temperature range of 1350 °C to 1550 °C was studied. • When the growth temperature was increased to 1450 °C, RMS reached about 0.2 nm. • When the growth temperature was increased to 1400 °C, the epitaxial layer is a single 4H-SiC. • High quality 4H-SiC epitaxial layer can be obtained at 1450 °C. TCS (SiHCl 3) is widely used in the rapid growth of SiC. However, in the study of using TCS to grow 4H-SiC, the growth temperature is mainly concentrated in 1550–1650 °C, and the research on lower growth temperature is lacking. In this study, TCS was used as the silicon precursor and epitaxial layers were grown in the temperature range of 1350–1500 °C. The results show that the single crystal type 4H-SiC epitaxial layer with good quality can be obtained at the growth temperature of 1450 ℃. [ABSTRACT FROM AUTHOR]

In this work, the organic light-emitting diodes (OLEDs) based on Alq 3 are fabricated. In order to make clear the transport mechanism of carriers in organic light-emitting devices at low temperature, detailed electroluminescence transient response and the current-voltage–luminescence (I–V–L) characteristics under different temperatures in those OLEDs are investigated. It founds that the acceleration of brightness increases with increasing temperature is maximum when the temperature is 200 K and it is mainly affected by the electron transport layer (Alq 3 ). The MoO 3 injection layer and the electroluminescent layer have great influence on the delay time when the temperature is 200 K. Once the temperature is greater than 250 K, the delay time is mainly affected by the MoO 3 injection layer. On the contrary, the fall time is mainly affected by the electroluminescent material. The V f is the average growth rate of fall time when the temperature increases 1 K which represents the accumulation rate of carriers. The difference between V f caused by the MoO 3 injection layer is 0.52 us/K and caused by the electroluminescent material Ir(ppy) 3 is 0.73 us/K. [ABSTRACT FROM AUTHOR]

The effect of InSb/In 0.9 Al 0.1 Sb buffer layers on InSb thin films grown on GaAs (0 0 1) substrate by molecular beam epitaxy (MBE) is investigated. The crystal quality and the surface morphology of InSb are characterized by XRD and AFM. The carrier transport property is researched through variable temperature hall test. The sharp interface between InSb/In 0.9 Al 0.1 Sb is demonstrated important for the high quality InSb thin film. We try different superlattice buffer layers by changing ratios, 2–0.5, thickness, 300–450 nm, and periods, 20–50. According to the function of the dislocation density to the absolute temperature below 150 K with different periods of SL buffers, we can find that the number of periods of superlattice is a major factor to decrease the density of threading dislocations. With the 50 periods SL buffer layer, the electron mobility of InSb at the room temperature and liquid nitrogen cooling temperature is ∼63,000 and ∼4600 cm 2 /V s, respectively. We deduce that the interface in the SL structure works as a filter layer to prevent the dislocation propagating to the upper InSb thin films. [ABSTRACT FROM AUTHOR]

Impaired wound healing caused by radiation happens frequently in clinical practice, and the exact mechanisms remain partly unclear. Various countermeasures have been taken to tackle with this issue. Ghrelin was considered as a potent endogenous growth hormone-releasing peptide, and its role in enhancing wound repair and regeneration was firstly investigated in whole-body irradiated (γ-ray) mice in this study. Collagen deposition and neovascularization were mostly discussed. The results demonstrated that ghrelin administration promoted cutaneous wound healing in irradiated mice, followed with reduced average wound closure time, increased spleen index ( SI) and improved haematopoiesis. After isolation and analysis of granulation tissues in combined radiation and wound injury ( CRWI) mice treated with and without ghrelin, a phenomenon of increased DNA, hexosamine, nitrate and nitrite synthesis, elevated collagen content and enhanced neovascularization was observed after ghrelin treatment. Western blotting indicated that ghrelin also increased the expression of vascular endothelial growth factor ( VEGF) and transforming growth factor-β ( TGF-β), both responsible for wound healing. However, previous administration of growth hormone secretagogue receptor 1a ( GHS-R1a) blocker blunted these therapeutic effects of ghrelin on CRWI mice. Our results identify ghrelin as a novel peptide that could be used for radiation-induced impaired wound healing. [ABSTRACT FROM AUTHOR]

• H 2 -etched SiC with different wafer orientation and doping are analyzed in detail. • Si-face 4° off-cut wafer boasts obvious terrace step after 1650 °C H 2 treatment. • ∼ 15 % to ∼ 51 % decrement in roughness is realized in C-face 4° off-cut substrate. • Defective graphitic structure is identified after high temperature Ar treatment. H 2 treatment is becoming a valuable method for the in-situ surface preparation of SiC wafer. Then clean interfacial layer can be attained in manufacturing SiC-based devices. However, surface morphology of SiC depends on wafer orientation and doping. Herein, H 2 -etched SiC wafers comprising various crystal planes were analyzed in detail. Formation of faceted etch pits occurs on C- and Si-faces of on-axis substrates. Meanwhile, Si-face of 4° off-cut substrate and the epitaxial layer boasts obvious terrace step after 1650 °C H 2 treatment, indicating the increment of surface roughness. As our study revealed, H 2 treatment is beneficial for achieving smoother surface morphology of C-face than Si-face wafers, as well as realizing ∼15 % to ∼51 % decrement in average roughness in C-face 4° off-cut substrate. Furthermore, defective graphitic structure and SiC crystal are identified after high temperature Ar treatment. The use of these results is expected to gain insights into the decomposition behavior of SiC with different wafer orientation and surface doping. Also, it is meaningful to realize the surface preparation process in power- and nano- electronic device fabrications. [ABSTRACT FROM AUTHOR]

Thermal rollover is one of the fundamental limitations that affect the output power and modulation bandwidth of high-speed laser in monolithic laser integrated circuits (ICs). Herein, an 850 nm vertical cavity surface emitting laser (VCSEL) with p-doping and sub quantum well (sub QW) centers active layer is proposed and investigated. The p-doping and sub QW insert in the offset position of each barrier, which are designed for reducing the thermal rollover and increasing the maximum intrinsic modulation bandwidth of the laser. Numerical simulations show that adding the p-doping and sub QW in active region could reduce the threshold currents (I th), improve the slope efficiency (SE) and delay the thermal rollover in VCSEL. Comparing with previous VCSEL, our proposed VCSEL has excellent high temperature output performance, and the maximum simulation 3-dB bandwidth is 43.9 GHz at 25 °C and 33.1 GHz at 85 °C, respectively. Furthermore, temperature-dependent time-resolved photoluminescence (PL) and PL excitation reveal this novel QW has strong radiative recombination rate, which is suitable for designing active region of high-speed and high power lasers. • A composite MQWs with sub QW insert layer and p-type δ -doping has been demonstrated. • Through simulation, the composite MQWs could reduce thermal rollover and increase the maximum intrinsic modulation bandwidth of VCSEL. • The maximum simulation 3 dB bandwidth could reach to 43.9 and 33.1 GHz at 25 ℃ and 85 ℃, respectively. • Through carrier dynamic analysis, this novel MQWs has strong radiative recombination rate. [ABSTRACT FROM AUTHOR]

• The temperature has a great influence on the crystal form of the 4H-SiC C-face epitaxial layer. • The Si source used for the growth of the SiC epitaxial layer is SiHCl 3. • Elevated temperature favors homoepitaxial growth of 4H-SiC C-face. SiC is an excellent semiconductor material that can be used in power semiconductor devices. It has the advantages of high thermal conductivity, stable chemical properties, and high critical breakdown field strength. The active region of a SiC device is usually in the SiC epitaxial layer, so the growth of high-quality SiC epitaxial layers is extremely valuable. In this paper, we investigate the epitaxial growth of SiC on n -type 4° off-axis SiC (0 0 0–1) substrates. We used a horizontal hot-wall chemical vapor deposition apparatus for rapid epitaxy on SiC substrates, using C 2 H 4 , and SiHCl 3 as precursors and H 2 as carrier gas, respectively, and growing at 1350 °C,1400 °C,1450 °C,1500 °C, 1550 °C, 1600 °C for half an hour to get epitaxial layer. The effect of growth temperature on the surface morphology of SiC (0 0 0 –1) epitaxial layer was analyzed and epitaxial layers is characterized by optical microscope, scanning electron microscope, atomic force microscope and Raman scattering instrument, and the growth rate of epitaxial layer was obtained. It is found that the higher growth temperature is helpful to obtain the epitaxial layer with smooth surface and higher content of 4H-SiC under certain pressure, C/Si molar ratio, and following rate of precursor and carrier gas. [ABSTRACT FROM AUTHOR]

• Temperature affects the polytype of epi-layer on semi-insulating substrates. • Elevated temperature is beneficial for homoepitaxial growth of 4H-SiC. • The surface morphologies obtained by Si-face and C-face epitaxy are different. • C-face epitaxy enables higher quality epitaxial layers. 4H-SiC has excellent physical and chemical properties such as wide band gap and high electron mobility and can be used in microwave and radio frequency devices. Epitaxial layer on semi-insulating (SI) substrate of 4H-SiC is a key structure for the fabrication of radio frequency devices. However, two-dimensional growth easily occurs during the epitaxy process to form 3C-SiC. Therefore, it is necessary to study the crystal polytype change in the epitaxial layer. This paper studied the effect of temperature on the epitaxial layer during epitaxy on 4H-SiC SI substrates using trichlorosilane and ethylene as source gases. The Si-face and the C-face were respectively selected as the growth planes, and the temperature varied in the range of 1400℃–1600℃. The samples were characterized using optical microscopy, atomic force microscopy, and Raman spectroscopy. The surface topography obtained by epitaxial growth was uniform, and the surface roughness of the smooth region was less than 1.0 nm. 3C-SiC was obtained at low temperature, and 4H-SiC was obtained at higher temperature. [ABSTRACT FROM AUTHOR]

3C-SiC thin films were grown on Si(111) substrates at 1250 °C by horizontal low pressure chemical vapor deposition (LPCVD). We performed an exhaustive study on the effect of H 2 flow rate on the crystalline quality, surface morphologies, growth rate, n-type doping of 3C-SiC thin films and the voids at the interface. The films show epitaxial nature with high crystal quality and surface morphology increase obviously with increasing H 2 flow rate. The growth rate and n-type doping are also dependent on H 2 flow rate. The properties of the voids at the interface are discussed based on the cross-sectional scanning electron microscope characterization. Transformation of voids with increasing H 2 flow rate are attributed to higher 3C-SiC film growth rate and H 2 etching rate. The mechanism of void formation is discussed based on our model, too. The results demonstrate that H 2 flow rate plays a very important role in the heteroepitaxial growth of 3C-SiC films. [ABSTRACT FROM AUTHOR]

Colossal magnetic moment up to 16.05 μ B /atom was found in GaN based diluted magnetic semiconductor films, which were fabricated by co-implantation with Cr and Er ions, followed by 800 °C annealing process. No secondary phase was detected in our samples within the detection limit of the high resolution X-ray diffractometer. Several new Raman peaks around 300, 360, 663 and 858 cm −1 are observed in the implanted and annealed samples, which have been explained reasonably. The colossal magnetic moment may come from the 3 d –4 f coupling between Cr and Er ions and/or the interaction between bound magnetic polarons formed in our samples, which can be facilitated by higher electron concentration. Cr and Er ions play a complementary role in determining the magnetic anisotropy. [ABSTRACT FROM AUTHOR]

As one of the most environmentally important cations, mercury(II) iron has the biological toxicity which impacts wild life ecology and human health heavily. A Hg 2+ biosensor based on AlGaAs/InGaAs high electron mobility transistors with high sensitivity and short response time is demonstrated experimentally. To achieve highly specific detection of Hg 2+ , an one-end thiol-modified ssDNA with lots of T thymine is immobilized to the Au-coated gate area of the high electron mobility transistors by a covalent modification method. The introduction of Hg 2+ to the gate of the high electron mobility transistors affects surface charges, which leads to a change in the concentration of the two-dimensional electron gas in the AlGaAs/InGaAs high electron mobility transistors. Thus, the saturation current curves can be shifted with the modification of the gate areas and varied concentrations of Hg 2+ . Under the bias of 100 mV, a detection limit for the Hg 2+ as low as10 nM is achieved. Successful detection with minute quantity of the sample indicates that the sensor has great potential in practical screening for a wide population. In addition, the dimension of the active area of the sensor is 20×50 μm 2 and that of the entire sensor chip is 1×2 mm 2 , which make the Hg 2+ biosensor portable. [ABSTRACT FROM AUTHOR]