To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure email@example.com
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Chlamydia trachomatis (CT) infection has been a major public health threat globally. Monitoring and prediction of CT epidemic status and trends are important for programme planning, allocating resources and assessing impact; however, such activities are limited in China. In this study, we aimed to apply a seasonal autoregressive integrated moving average (SARIMA) model to predict the incidence of CT infection in Shenzhen city, China. The monthly incidence of CT between January 2008 and June 2019 in Shenzhen was used to fit and validate the SARIMA model. A seasonal fluctuation and a slightly increasing pattern of a long-term trend were revealed in the time series of CT incidence. The monthly CT incidence ranged from 4.80/100 000 to 21.56/100 000. The mean absolute percentage error value of the optimal model was 8.08%. The SARIMA model could be applied to effectively predict the short-term CT incidence in Shenzhen and provide support for the development of interventions for disease control and prevention.
To investigate the morphology and dimensions of the vestibular aqueduct on axial, single-oblique and double-oblique computed tomography images.
The computed tomography temporal bone scans of 112 patients were retrospectively evaluated. Midpoint and opercular measurements were performed using axial, single-oblique and double-oblique images. Morphometric analyses were also conducted. The vestibular aqueduct sizes on axial, single-oblique and double-oblique images were compared.
At the midpoint, the mean (± standard deviation) vestibular aqueduct measured 0.61 ± 0.23 mm, 0.74 ± 0.27 mm and 0.82 ± 0.38 mm on axial, single-oblique and double-oblique images, respectively; at the operculum, the vestibular aqueduct measured 0.91 ± 0.30 mm, 1.11 ± 0.45 mm and 1.66 ± 1.07 mm on the respective images. The co-efficients of variation of the vestibular aqueduct measured at the midpoint were 37.4 per cent, 36.5 per cent and 47.5 per cent on axial, single-oblique and double-oblique images, respectively; at the operculum, the measurements were 33.0 per cent, 40.5 per cent and 64.5 per cent. Regarding morphology, the vestibular aqueduct was fissured (33.5 per cent), tubular (64.3 per cent) or invisible (2.2 per cent).
The morphology and dimensions of the vestibular aqueduct were highly variable among axial, single-oblique and double-oblique images.
Motivated by the process of
convective mixing in porous media, here we study the formation of rock-dissolution patterns that arise from geochemical reactions during Rayleigh–Bénard–Darcy convection. Under the assumption of instantaneous chemical equilibrium, we adopt a formulation of the local reaction rate as a function of scalar dissipation rate, a measure that depends solely on flow and transport, and chemical speciation, which is a measure that depends only on the equilibrium thermodynamics of the chemical system. We use high-resolution simulations to examine the interplay between the density-driven hydrodynamic instability and the rock dissolution reactions, and analyse the impact of geochemical reactions on the macroscopic mass exchange rate. We find that dissolution of carbonate rock initiates in regions of locally high mixing, but that the geochemical reaction shuts down significantly earlier than shutdown of convective mixing. This early shutdown feature reflects the important role that chemical speciation plays in this hydrodynamics–reaction coupled process. Finally, we extend our analysis to three dimensions and explore the morphology of dissolution patterns in three dimensions.
Gattini and CSTAR have been installed at Dome A, Antarctica, which provide time-series photometric data for a large number of pulsating variable stars. We present the study for several variable stars with the data collected with the two facilities in 2009 to demonstrate the scientific potential of observations from Dome A for asteroseismology.
Turbulent particle transport is investigated with a quasilinear theory that is motivated by the boron impurity transport experiments in the Alcator C-Mod. Eigenvalue problems for sets of reduced fluid equations for multi-component plasmas are solved for the self-consistent fluctuating field vectors composed of the electric potential φ, the main ion density δni, the impurity density δnz and the ion temperature fluctuation δTi. For Alcator C-Mod parameters, we investigate two drift wave models: (1) the density-gradient-driven impurity drift wave and (2) the ion-temperature-gradient-driven ion temperature gradient (ITG) mode. Analytic and numerical results for particle transport coefficients are derived and compared with the transport data and the neoclassical theory. We explore the ability of the model to explain impurity density profiles in three confinement regimes: H-mode, I-mode and internal transport barrier (ITB) regime in C-Mod. Related experiments reported on the Large Helical Device are briefly discussed.
We investigate some basic properties of Damped Lyman alpha systems based on the Semi-Analytical model of disk galaxy formation theory. We derive the DLA metallicity, column density, number density, gas content and cosmic star formation rate by assuming that disks form at the center of dark halos, and the modelled DLAs are selected by Monte Carlo simulation according to the distributions of halo properties. We find that DLA hosts are dominated by small galaxies and biased to extended galaxies. In terms of model results, DLAs could naturally arise in a ACDM universe from radiatively cooled gas in dark matter halos. However, model predicts a reverse correlation between metallicity and the column density when compared with observations, regardless of the proposed observational bias. We argue that this could be resulted from the model limitations, or the inadequacy of Schmidt-type star formation mode at high redshift, or/and the diversities of DLA populations.
A new process has been developed in Paratek Microwave Inc. to formulate stable tunable (Ba, Sr)TiO3 (BST) based thin film material. Varactors, with a co-planar structure, were fabricated by using the new material. The varactor Q of 105 tested at 2 GHz was observed with average tunability of 58 % at 150V (37.5 V/μm). The lifetime tests indicated that this material is very stable under continuous 100 to 150 V dc bias both at the room temperature and in 70 °C environment. Thus, this novel tunable thin film material opens a new avenue to develop high quality tunable microwave devices. Tunable IF filters have been built by using this novel material for microwave backhaul radios and handset applications. Initial results of a RF phase shifter are also included and demonstrate another application of these films.
Thin films of tin oxide (SnO2) with the rutile structure are the subject of many investigations due to their potential applications, such as gas sensing devices, lithium batteries cathodes and solar cells. There is a growing interest in the development of gas sensors using SnO2 thin films due to their high surface to volume ratio. Previous studies have shown that the gas sensing properties of SnO2 are very dependent on the microstructure and that doping elements can greatly influence their electrical properties. In this paper we present transmission electron microscopy (TEM) studies of the microstructure and crystal defects of SnO2 thin films.
Tin oxide films 5 nm in thickness were deposited on the surface of sapphire (A12O3) by pulsed laser ablation of ceramic SnO2 targets. The film microstructure was studied using X ray diffraction, atomic force microscopy and transmission electron microscopy. Defects were studied using high resolution transmission electron microscopy (HRTEM).
GaN implanted with donor(Si, S, Se, Te) or acceptor (Be, Mg, C) species was annealed at 900-1500 °C using AlN encapsulation. No redistribution was measured by SIMS for any of the dopants and effective diffusion coefficients are ≤2 × 10−13 cm2. s−1 at 1400 °C, except Be, which displays damage-enhanced diffusion at 900 °C and is immobile once the point defect concentration is removed. Activation efficiency of ∼90% is obtained for Si at 1400 °C. TEM of the implanted material shows a strong reduction in lattice disorder at 1400-1500 °C compared to previous results at 1100 °C. There is minimal interaction of the sputtered AlN with GaN under our conditions, and it is readily removed selectively with KOH.
In order to determine whether infection with
Schistosoma japonicum is related to a higher rate
of infection with hepatitis B virus and/or to a higher probability
of HBsAg chronic carriage, a
population based survey was carried out in China in which HBV markers were
studied in 112
subjects with long-lasting S. japonicum infection, and 93 subjects
with no S. japonicum infection
37·5% of the cases and 40·9% of controls showed no markers
of HBV infection. The
prevalence rate of HBsAg was 12·5% in the cases and
12·9% in the controls. For anti-HBc
and anti-HBs the figures were 59·8% and 59·8%, and
27·9% and 35·0%, respectively. These
data do not support the hypothesis of an interaction between infection
with hepatitis B virus
and S. japonicum.
Si+ implant activation efficiencies above 90%, even at doses of 5×1015 cm−2, have been achieved in GaN by RTP at 1400–1500°C for 10 secs. The annealing system utilizes with MoSi2 heating elements capable of operation up to 1900 °C, producing high heating and cooling rates (up to 100 °C · s−1). Unencapsulated GaN show severe surface pitting at 1300 °C, and complete loss of the film by evaporation at 1400 °C. Dissociation of nitrogen from the surface is found to occur with an approximate activation energy of 3.8 eV for GaN (compared to 4.4 eV for AIN and 3.4 eV for InN). Encapsulation with either rf-magnetron reactively sputtered or MOMBE-grown AIN thin films provide protection against GaN surface degradation up to 1400 °C, where peak electron concentrations of ∼5×1020 cm-3 can be achieved in Si-implanted GaN. SIMS profiling showed little measurable redistribution of Si, suggesting Dsi ≤ 10-13 cm2 · s−1 at 1400 °C. The implant activation efficiency decreases at higher temperatures, which may result from SiGa to SiN site switching and resultant self-compensation.
GaN implanted with donor(Si, S, Se, Te) or acceptor (Be, Mg, C) species was annealed at 900-1500°C using AIN encapsulation. No redistribution was measured by SIMS for any of the dopants and effective diffusion coefficients are ≤2×10-13 cm2 s-1 at 1400°C, except Be, which displays damage-enhanced diffusion at 900°C and is immobile once the point defect concentration is removed. Activation efficiency of ∼90% is obtained for Si at 1400°C. TEM of the implanted material shows a strong reduction in lattice disorder at 1400-1500°C compared to previous results at 1100°C. There is minimal interaction of the sputtered AIN with GaN under our conditions, and it is readily removed selectively with KOH.
We introduce for the first time a novel rapid thermal processing (RTP) unit called ZapperTM, which has recently been developed by MHI Inc. and the University of Florida for high temperature thermal processing of semiconductors. This ZapperTM unit is capable of reaching much higher temperatures (>1500 °C) than conventional tungsten-halogen lamp RTP equipment and achieving high ramp-up and ramp-down rates. We have conducted implant activation annealing studies of Si+-implanted GaN thin films (with and without an AIN encapsulation layer) using the ZapperTM unit at temperatures up to 1500 °C. The electrical property measurements of such annealed samples have led to the conclusion that high annealing temperatures and AIN encapsulation are needed for the optimum activation efficiency of Si+ implants in GaN. It has clearly been demonstrated that the ZapperTM unit has tremendous potential for RTP annealing of semiconductor materials, especially for wide bandgap compound semiconductors that require very high processing temperatures.
Gallium nitride is one of the most promising materials for ultraviolet and blue light-emitting diodes and lasers. Both Molecular Beam Epitaxy (MBE) and Metal-Organic Chemical Vapor Deposition (MOCVD) have recently made strong progress in fabricating high-quality epitaxial GaN thin films. In this paper, we review materials-related issues involved in MBE growth. We show that a strong understanding of the unique meta-stable growth process allows us to correctly predict the optimum conditions for epitaxial GaN growth. The resulting structural, electronic and optical properties of the GaN films are described in detail.
The ferroelectric thin films of bismuth titanate (Bi4Ti3O12) have been prepared by metalorganic chemical vapor deposition ( MOCVD) technique at atmosphere. The triphenyl bismuth (Bi(CaH5 ) 3)and tetrabutyl titanate (C16H36O4Ti) were used as precursors. Dense Bi4Ti3 O12 films with smooth shinning surface have been grown on Si( 100) substrates at 550°C whithout postannealing. The as- grown films were characterized by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and energy dispersion analysis ( EDAX). The films showed well-ordered crystallinity with an (001)preffered orientation. The influence of growth parameters on deposition rate, composition and morphology of as-grown films was also discussed.
Email your librarian or administrator to recommend adding this to your organisation's collection.