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There has been a rapid increase in the number of human adenovirus type 7 (HAdV-7) and invasive pulmonary fungal infections (IPFIs) co-infection.In this study, we included patients with confirmed HAdV-7 infection during the period from 2018 to 2019 to explore clinical characteristics of severe HAdV-7 pneumonia combined with IPFIs.Among the 143 patients, 35 cases were co-infected with IPFIs. Others were assigned to the control group (n Z 108). Patients wereprone to be complicated with respiratory failure, heart failure and hemophagocytic syndromein IPFIs group. Thirty-one species of fungi were detected in the IPFIs group, among whichAspergillus was the most common species. Compared to control group, patients had lowerlevels of WBC, CD3þ T lymphocyte counts and CD19þ B lymphocyte counts in IPFIs group.Aspergillus is the most common species in IPFIs combined with severe HAdV-7 pneumonia. For children with severe HAdV-7 pneumonia who are younger, have a long course of disease, and have been admitted to the ICU, we should predict the occurrence of IPFIs when there is multi-system dysfunction and the reduction of CD3+ T lymphocyte counts and CD19+ B lymphocyte counts in course of their disease.

In this investigation, conventional microcrystalline diamond (MCD) and boron doped diamond (BDD) films are deposited onto commercially available cemented tungsten carbide (WC-Co) Ball-nose endmills by using hot filament chemical vapour deposition (HFCVD). The quality and properties of the as-deposited diamond film are characterized by field emission scanning electron microscope (FESEM) and Raman spectroscopy. Milling tests of graphite materials using MCD, BDD coated and uncoated tool are carried out. Experiment results reveal that BDD films possess higher adhesive strength to the substrate than that of MCD films, and the BDD coated mills allow to be given smaller flank wear and longer tool life, when compared with MCD coated and uncoated WC-Co tools. Cutting performances of WC-Co mills in graphite milling are greatly improved by BDD coating, and typically more than 10 times the tool life is obtained. The research results are of great significance for high efficiency and quality machining of graphite materials.

Linking diagenesis to depositional facies and sequence stratigraphy enables better prediction of spatial and temporal distribution of diagenetic alterations, and thus of evolution of reservoir quality in sandstones. This thesis demonstrates that employing this approach is possible because depositional facies and sequence stratigraphy can provide useful information on parameters controlling the near-surface diagenesis, such as changes in: (i) pore-water chemistry, (ii) residence time of sediments under certain geochemical conditions, (iii) detrital composition and proportion of extra- and intra-basinal grains, and (iv) types and amounts of organic matter.Evidence from four case studies enabled the development of conceptual models for distribution of diagenetic alterations and of their impact on evolution of reservoir quality in sandstones deposited in paralic, shallow marine and fluvio-lacustrine environments. Diagenetic alterations that have been constrained within the context of depositional facies and sequence stratigraphy include: (i) carbonate cement (microcrystalline and equant calcite spars dolomite over poikilotopic calcite), pyrite and glaucony are most abundant in progradational braid-delta fan sequences, particularly along the topsets (i.e. maxiumum flooding surface, MFS) and along parasequences boundaries in the deltaic facies of the early highstand systems tract HST, (ii) cementation by coarse spar calcite, dolomite, and the formation of moldic porosity by the dissolution of framework carbonate grains are most abundant in the aggradational fan deltas sequences, (iii) eogenetic kaolinitization of framework silicates is largely restricted to the fluvial and paralic HST sandstones, whereas telogenetic kaolinite may occur in the transgressive systems tract TST sandstones too, (iv) formation of goethite ooids in the TST sediments, (v) formation of glaucony, siderite spherules, and extensive grain-coatings, grain-replacing and ooidal berthierine, more in the TST than in the HST sediments, particularly below the transgressive surface TS and MFS, (vi) cementation by calcite with (δ18OV-PDB = -11.5‰ to -5.4‰) and Fe-dolomite/ankerite (δ18OV-PDB = -10.8‰ to -9.6‰) occurs in both TST and HST sandstones, (vii) syntaxial quartz overgrowths are most extensive in the HST sandstones owing to the presence of incomplete grain-coating berthierine/chlorite, (viii) greater amounts of micro-porosity in the TST sandstones than in the HST sandstones are related to the greater amounts of berthierine/chlorite in the former sandstones, and (ix) chlorite rims around quartz grains retarded the precipitation of quartz overgrowths, and hence prevented a greater loss of primary intergranular porosity in fluvio-lacustrine sandstones. Therefore, constraining the distribution of diagenetic alterations in the contexts of depositional facies and sequence stratigraphic context is a powerful approach to be used in hydrocarbon exploration.

Nano-scale 8mol% titania doped yttria stabilized zirconia (8TiYSZ) powders were prepared by coprecipitation combined with azeotropic distillation process. Powder X-ray diffraction, BET method and TEM were performed to characterize the powder properties. The relative density of 8TiYSZ sample sintered by spark plasma sintering technique at 1150°C for 3min reached 99%. The electrical conductivity of sintered pellet was much higher than the reported one.

We have theoretically investigated current–voltage characteristics of periodically-driven GaAs-based miniband superlattice at room temperature by using the time-dependent hydrodynamic balance equations. With the amplitude of the ac signal varying in the parameter space, the superlattice is found to exhibit various types of spatiotemporal behavior and current–voltage characteristics. In the case of a large-amplitude ac signal, the solution is synchronized with the ac frequency, and the time-averaged current–voltage curve exhibits microwave-radiation-induced dc current suppression. A good agreement is obtained between the calculated dc current and the recent experiment for a GaAs/AlAs miniband superlattice.

We study the effect of impact ionization (II) on high-field electron transport in bulk Si with a conduction band composed of ellipsoidal X and L valleys, using the nonparabolic multivalley balance-equation method. The impact ionization process is described by the II-induced effective acceleration A ii , the II-induced energy-loss rate W ii , and the II rate g ii , which are determined self-consistently during the process of the calculation. The calculated results such as average carrier velocity and the II coefficient show good agreement with experimental data and with MC simulation, thus confirming the validity of the model. An empirical relation of the field- and lattice temperature-dependence of the II coefficient is suggested, which may be useful in device simulation with the balance-equation theory.

Nonparabolic multivalley hydrodynamic balance equations are presented as an extension of the hydrodynamic equations for nonparabolic single valley semiconductors and of the balance equations for homogeneous multivalley nonparabolic semiconductors. Its main features which differ from the conventional hydrodynamic equations lie in: (1) a nonparabolicity-related factor, the ensemble-averaged inverse-effective mass, associated with the field acceleration term in the momentum-balance equation; (2) the collisional terms, which are expressed by functions of particle transition, frictional acceleration and energy-loss rate, by which the variation of the conduction band structure and intervalley kinetics are automatically included. As an example, we apply this set of balance equations to a self-consistent numerical simulation of a ballistic diode made of AlxGa1−xAs with a two-valley structure. The nonlinear electron transport characteristics, such as velocity overshoot and intervalley transfer, at several values of applied potential and composition are analyzed and discussed.

The paper presents new hydrodynamic balance equations for semiconductor device simulation, which stem from the Lei–Ting balance equations for spatially inhomogeneous device structures. Their main characteristics, which differ from those of the conventional hydrodynamic equations, is the inclusion of accurate momentum and energy collision terms at the microscopic level. With the help of the nonlinear frictional force and energy transfer functions, the collision terms as well as the relaxation times can be self-consistently calculated from the primary physical parameters, taking full account of dynamical screening and other quantum-mechanical effects. A solution method for this set of differential–integral equations is proposed and applied to a one-dimensional simulation of a submicron Si n+nn+n structure diode. The numerical results for various applied voltages are presented.

With the help of the Lei-Ting balance equations for multi-valley semiconductors, a detailed calculation of steady-state hot-electron transport in bulk Al x Ga 1− x As with a Γ - L - X band structure has been carried out for various compositions and lattice temperatures. We introduce different drift velocity, electron temperature and Fermi energy level (or electron density) for the Γ, L and X valleys. The calculated results for drift velocity as a function of the applied electric field show good agreement with those obtained from Monte Carlo simulation. The role of different scattering mechanisms, which affect the negative differential mobility characteristics is also discussed. It is indicated that the Lei-Ting method is a very convenient and effective tool for studying the transport behaviour of carriers in semiconductors.

This paper reports on a study of high-field transport in bulk GaAs on the basis of the nonparabolic balance equations recently extended to systems having a multiband structure. Nonlinear transport effects are analyzed taking account of the nonparabolicity of the band structure. The nonparabolic results for the drift velocity in n -type GaAs show good agreement with those from MC simulation and with measured data. It is shown that the nonparabolic balance equations can be used as an alternative theoretical approach to high-field transport in nonparabolic multivalley semiconductors.

We have theoretically investigated the free-earner absorption of intense terahertz (THz) radiation in InAs/AlSb heterojunctions (HJ), by considering multiple photon process and interband impact ionization. As many as needed hole subbands and multiphoton channels are self-consistently taken into account. It's indicated that the THz radiation with a larger amplitude or a lower frequency has a stronger effect on electric transport characteristics. Good agreement is obtained between the calculated absorption percentages and the available experimental data for InAs/AlSb HJ's at the radiation frequency f/sub ac/ = 0.64 THz.

Recently discovered modulations of Shubnikov-de Haas oscillations in microwave-irradiated two-dimensional electron systems are shown to arise from electron heating induced by the radiation. The electron temperature, obtained by balancing the energy absorption from the microwave field and the energy dissipation to the lattice through realistic electron-phonon couplings, exhibits resonance. The modulation of the Shubnikov de Haas oscillation and the suppression of magnetoresistance are demonstrated together with microwave-induced resistance oscillation, in agreement with experimental findings., Revised version, published in Appl. Phys. Letters

The effects of confinement on steady state miniband transport are examined here, particularly with respect to negative differential conductivity. The superlattice is taken to be confined in one of the two directions normal to the growth direction. Using a balance equation approach adjusted to incorporate superlattice band structure and transverse confinement-induced subbands, we present the results of numerical calculations which take account of impurity, acoustic phonon and polar optic phonon scatterings. Nonlinear drift velocity and electron temperature are exhibited as functions of applied electric field for a series of confined superlattices having miniband width Δ = 900 K . Negative differential conductivity is clearly manifested and the case of confinement width d x = 45 nm appears to be suitable for use in high frequency oscillators even at 300 K lattice temperature.

Force and energy balance equations are formulated for hot electron transport in an arbitrary superlattice miniband, and are analyzed for negative differential conductivity using a tight binding approximation for GaAs/AlAs superlattices. Both impurity and phonon scatterings are treated. The calculated steady-state peak drift velocity v p for transport across the superlattice, and the critical field E c at which the drift velocity peaks, are analyzed as functions of the miniband width. The present theory predicts for the first time an increase in E c d ( d is the superlattice period) with decreasing miniband width, in favorable comparison with the experimental observations of Sibille et al., indicating that Bloch miniband transport is responsible for negative differential velocity even for the samples of narrowest miniband width in their experiment.

Although narrow-miniband superlattices have an important transport inhomogeneity manifested in the formation of high-field domains and in periodic structure of the I-V characteristic when the applied voltage increases beyond a threshold,1 the most interesting transport phenomena in wide-miniband systems are those related to Esaki-Tsu negative differential mobility (NDM) at relatively low electric field.2 We report here on a careful examination of the frequency dependence of small-signal ac mobility and the possible fluctuation instability of a planar superlattice subject to negative differential miniband conductance. Our analysis is based on three-dimensional hydrodynamic nonlinear balance equations with accurate microscopic treatment of phonon and impurity scatterings.

A semiconductor device modeling program based on hydrodynamic balance equations is developed. It is capable of treating multiple carriers in compositionally nonuniform (such as heterostructures) and spatially inhomogeneous device structures, as well as high electric field and associated nonlinear effects. Unlike other balance equation based approaches to device modeling, where the various relaxation rates are imported from Monte Carlo calculations or simply assumed to be constant, our approach is based on the premise of computing these rates as part of the simulation, in the form of nonlinear frictional force and energy transfer functions, with full account of dynamical screening and other quantum mechanical effects embodied in the random phase approximation dielectric function of the system. The simplicity of our technique permit fast and economical modeling of device performance characteristics, requiring only a fraction of the CPU time needed for Monte Carlo simulations.

The transport properties of two device-related semiconductor microstructure quantum-well systems are addressed here. The first involves the theory of negative differential mini-band conductance (NDC) in a lateral semiconductor superlattice of very thin quantum dots laid out in a square array on a plane, both with and without a normal magnetic field. NDC of the total current is made steeper by the magnetic field, and the Hall coefficient is shown to exhibit hole features near the electron energy band top. The second system discussed here is composed of two parallel planar quantum wells separated by a potential barrier, which exhibits electron-hole Coulomb drag effects shown to involve nonlinearity.

Microwave small-signal mobility of vertical conduction in the presence of a dc bias is investigated for cylindrically confined superlattices having various transverse diameters. At finite dc bias the differential mobility exhibits peculiar frequency-dependence, which stems from a decrease of the average inverse effective mass of carriers in conjunction with an increase of their average longitudinal energy, and is characterized approximately by a momentum and an energy relaxation time. It is found that the effective energy-relaxation time increases significantly as the transverse dimensions of the superlattice increase. PACS: 72.30.+q; 73.50.Mx

In the presence of a static lattice distortation of wave vector Q, a direct coupling between electron density and dynamical CDW fluctuation exists in the first anharmonic term of the electron-ion potential. Based on this interaction a theory is developed for Raman scattering of light from an anisotropic CDW superconductor using a partial gapping model. The renormalization both by the Coulomb interaction at small q limit and by the residual coupling between electrons is taken into account. It is shown that this coupling not only always induces a pole at frequency ohms ≈ 2Δ (Δ is the superconducting gap) in the phonon spectrum but also contributes to the enhancement of Raman activity at gap frequency, if the coupling parameter g2(k) is anisotropic.

Force and energy balance equations are derived for steady state hot electron transport in a type-I superlattice composed of periodically arranged finite-width quantum wells. The scatterings by remote and background impurities and by acoustic and polar optical phonons are taken into account, together with Coulomb interactions between intralayer electrons and interlayer electrons. The carrier mobility and electron temperature are calculated as functions of drift velocity ν up to ν=3×107 cm / s, showing significant nonlinearity and dependence on geometrical superlattice parameters (quantum well width and separation, etc.)

We have studied the electron density correlation function of a tunneling superlattice using a tight-binding envelope function and taking account of the nearest-neighbor overlap. A matrix density correlation function Π is introduced, which can be expressed explicitly in terms of a matrix density correlation bubble Π 0 and a matrix effective Coulomb potential V in RPA. The plasmon dispersion relation of a superlattice with electron wave function overlap, given by the equation det(1 − VΠ 0 )=0, is determined.