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Finite-amplitude wave groups with multiple near-resonances are investigated to extend the existing results due to Liu et al. (J. Fluid Mech., vol. 835, 2018, pp. 624–653) from steady-state wave groups in deep water to steady-state wave groups in finite water depth. The slow convergence rate of the series solution in the homotopy analysis method and extra unpredictable high-frequency components in finite water depth make it hard to obtain finite-amplitude wave groups accurately. To overcome these difficulties, a solution procedure that combines the homotopy analysis method-based analytical approach and Galerkin method-based numerical approaches has been used. For weakly nonlinear wave groups, the continuum of steady-state resonance from deep water to finite water depth is established. As nonlinearity increases, the frequency bands broaden and more steady-state wave groups are obtained. Finite-amplitude wave groups with steepness no less than
are obtained and the resonant sets configuration of steady-state wave groups are analysed in different water depths. For waves in deep water, the majority of non-trivial components appear around the primary ones due to four-wave, six-wave, eight-wave or even ten-wave resonant interactions. The dominant role of four-wave resonant interactions for steady-state wave groups in deep water is demonstrated. For waves in finite water depth, additional non-trivial high-frequency components appear in the spectra due to three-wave, four-wave, five-wave or even six-wave resonant interactions with the components around the primary ones. The amplitude of these high-frequency components increases further as the water depth decreases. Resonances composed by components only around the primary ones are suppressed while resonances composed by components around the primary ones and from the high-frequency domain are enhanced. The spectrum of steady-state resonant wave groups changes with the water depth and the significant role of three-wave resonant interactions in finite water depth is demonstrated.
We study the shape and motion of gas bubbles in a liquid flowing through a horizontal or slightly inclined thin annulus. Experimental data show that in the horizontal annulus, bubbles develop a unique ‘tadpole-like’ shape with a semi-circular cap and a highly stretched tail. As the annulus is inclined, the bubble tail tends to vanish, resulting in a significant decrease of bubble length. To model the bubble evolution, the thin annulus is conceptualised as a ‘Hele-Shaw’ cell in a curvilinear space. The three-dimensional flow within the cell is represented by a gap-averaged, two-dimensional model, which achieved a close match to the experimental data. The numerical model is further used to investigate the effects of gap thickness and pipe diameter on the bubble behaviour. The mechanism for the semi-circular cap formation is interpreted based on an analogous irrotational flow field around a circular cylinder, based on which a theoretical solution to the bubble velocity is derived. The bubble motion and cap geometry is mainly controlled by the gravitational component perpendicular to the flow direction. The bubble elongation in the horizontal annulus is caused by the buoyancy that moves the bubble to the top of the annulus. However, as the annulus is inclined, the gravitational component parallel to the flow direction becomes important, causing bubble separation at the tail and reduction in bubble length.
Bacillary dysentery continues to be a major health issue in developing countries and ambient temperature is a possible environmental determinant. However, evidence about the risk of bacillary dysentery attributable to ambient temperature under climate change scenarios is scarce. We examined the attributable fraction (AF) of temperature-related bacillary dysentery in urban and rural Hefei, China during 2006–2012 and projected its shifting pattern under climate change scenarios using a distributed lag non-linear model. The risk of bacillary dysentery increased with the temperature rise above a threshold (18·4 °C), and the temperature effects appeared to be acute. The proportion of bacillary dysentery attributable to hot temperatures was 18·74% (95 empirical confidence interval (eCI): 8·36–27·44%). Apparent difference of AF was observed between urban and rural areas, with AF varying from 26·87% (95% eCI 16·21–36·68%) in urban area to −1·90% (95 eCI −25·03 to 16·05%) in rural area. Under the climate change scenarios alone (1–4 °C rise), the AF from extreme hot temperatures (>31·2 °C) would rise greatly accompanied by the relatively stable AF from moderate hot temperatures (18·4–31·2 °C). If climate change proceeds, urban area may be more likely to suffer from rapidly increasing burden of disease from extreme hot temperatures in the absence of effective mitigation and adaptation strategies.
At the end of 2013, China reported a countrywide outbreak of measles. From January to May 2014, we investigated the clinical and immunological features of the cases of the outbreak admitted to our hospital. In this study, all 112 inpatients with clinically diagnosed measles were recruited from the 302 Military Hospital of China. The virus was isolated from throat swabs from these patients, and cytokine profiles were examined. By detecting the measles virus of 30 of the 112 patients, we found that this measles outbreak was of the H1 genotype, which is the major strain in China. The rates of complications, specifically pneumonia and liver injury, differed significantly in patients aged <8 months, 8 months to 18 years, and >18 years: pneumonia was more common in children, while liver injury was more common in adults. Pneumonia was a significant independent risk factor affecting measles duration. Compared to healthy subjects, measles patients had fewer CD4+IL-17+, CD4+IFN-γ+, and CD8+IFN-γ+ cells in both the acute and recovery phases. In contrast, measles patients in the acute phase had more CD8+IL-22+ cells than those in recovery or healthy subjects. We recommend that future studies focus on the age-related distribution of pneumonia and liver injury as measles-related complications as well as the association between immunological markers and measles prognosis.
Gray matter (GM) atrophy and disrupted intrinsic functional connectivity (IFC) are often present in patients with amnestic mild cognitive impairment (aMCI), which shows high risk of developing into Alzheimer's disease. Little is known, however, about the relationship between GM atrophy and altered IFC, and whether they are related to cognitive decline.
A total of 30 aMCI and 26 cognitively normal (CN) subjects were recruited for this study. Optimized voxel-based morphometric and resting-state functional connectivity magnetic resonance imaging approaches were performed to measure the GM volumes (GMVs) and atrophy-related IFC, respectively. Multivariate linear regression analysis was used to examine the effects of GM atrophy and IFC on cognitive performance across subjects, after controlling for the effects of age, education, gender and group.
Compared with CN subjects, aMCI subjects showed significantly reduced GMVs and decreased IFC in the frontal-parietal and medial temporal lobe systems. Multivariate regression analysis further demonstrated that the GMVs and decreased IFC simultaneously affected the cognitive function. Specifically, GMVs were positively correlated with cognitive performances, including global cognition and episodic memory, and showed a strong trend in correlation between GMVs and non-episodic memory, whilst IFC was positively correlated with the above three cognitive measures, across all subjects. In addition, significant correlation was found between GMVs and altered IFC strength across all subjects.
Our findings demonstrated that GMVs and IFC jointly contribute to cognitive performance, and combining quantitative information about GMVs and the strength of functional connectivity may serve as an indicator of cognitive deficits in non-demented elderly.
Boron was incorporated into GaN in order to determine its limits of solubility, its ability of reducing the lattice constant mismatch with 6H-SiC, as well as its effects on the structural and optical properties of GaN epilayers. BxGa1−xN films were deposited on 6H-SiC (0001) substrates at 950 °C by low pressure MOVPE using diborane, trimethylgallium, and ammonia as precursors. A single phase alloy with x=0.015 was successfully produced at a gas reactant B/Ga ratio of 0.005. Phase separation into pure GaN and BxGa1−xN alloy with x=0.30 was deposited for a B/Ga reactant ratio of 0.01. This is the highest B fraction of the wurtzite structure alloy ever reported. For B/Ga ratio ≥ 0.02, no BxGa1−xN was formed, and the solid solution contained two phases: wurtzite GaN and BN based on the results of Auger and x-ray diffraction. The band edge emission of BxGa1−xN varied from 3.451 eV for x=0 with FWHM of 39.2 meV to 3.465 eV for x=0.015 with FWHM of 35.1 meV. The narrower FWHM indicated that the quality of GaN epilayer was improved with small amount of boron incorporation.
Stimuli-sensitive materials can change properties upon exposure to an external stimulus. Thermoreversible gelation upon heating is one example for such a stimuli sensitivity. Here, it is of significance to tailor the transition temperature and to achieve large changes of G’ and the viscosity. Grafting of the thermosensitive poly(ethylene glycol-b-propylene glycol-b-ethylene glycol)s (PEPEs) to pectin was performed in order to investigate if tailoring of the sol-gel-transition temperature can be achieved by adjusting the grafting ratio. PEPEs were aminated and grafted to the polysaccharide via EDC coupling as shown by FTIR. The sol-gel transition of the pectin, PEPE, and the grafted system (PGP) was investigated by rheology. The gelation temperature (Tgel) of the system could be adjusted by varying the grafting density of PEPE onto pectin as well as by the concentration of the thermosensitive polymer in aqueous solution. A concentration of 15 – 20 wt% of the grafted system in water led to gelation temperatures in the range of 25 – 33 °C and the critical micelle concentration (CMC) and critical micelle temperature (CMT) of the grafted systems were determined by UV spectroscopy. The viscosity and the G’ increased by four orders of magnitudes at Tgel, which is comparable to PEPEs alone, but could be reached at lower PEPE concentrations. In the future, a thorough mechanistic investigation of the gelation process would be of interest.
To review the genotype and cochlear implantation outcome of patients with nonsyndromic hearing loss and enlarged vestibular aqueduct.
Twenty-one Chinese children with nonsyndromic hearing loss and enlarged vestibular aqueduct underwent genetic examination. A DNA microarray was used to screen for the IVS7-2A>G and H723R mutations. Any DNA samples with one or none of the two mutant alleles were sequenced to detect other mutations in the SLC26A4 and FOXI1 genes.
Twelve SLC26A4 mutations were detected, including three novel mutations. The most common mutations detected were IVS7-2A>G and H723R. Twelve patients received cochlear implants, and subsequently demonstrated excellent speech perception.
Three novel mutations were detected in Chinese patients with nonsyndromic hearing loss and enlarged vestibular aqueduct. The SLC26A4 mutation spectrum in the Chinese population is similar to that in other East Asian populations. Cochlear implantation is a safe and effective treatment in patients with enlarged vestibular aqueduct.
Studies conducted in Europe and the USA have shown that co-morbidity between major depressive disorder (MDD) and anxiety disorders is associated with various MDD-related features, including clinical symptoms, degree of familial aggregation and socio-economic status. However, few studies have investigated whether these patterns of association vary across different co-morbid anxiety disorders. Here, using a large cohort of Chinese women with recurrent MDD, we examine the prevalence and associated clinical features of co-morbid anxiety disorders.
A total of 1970 female Chinese MDD patients with or without seven co-morbid anxiety disorders [including generalized anxiety disorder (GAD), panic disorder, and five phobia subtypes] were ascertained in the CONVERGE study. Generalized linear models were used to model association between co-morbid anxiety disorders and various MDD features.
The lifetime prevalence rate for any type of co-morbid anxiety disorder is 60.2%. Panic and social phobia significantly predict an increased family history of MDD. GAD and animal phobia predict an earlier onset of MDD and a higher number of MDD episodes, respectively. Panic and GAD predict a higher number of DSM-IV diagnostic criteria. GAD and blood-injury phobia are both significantly associated with suicidal attempt with opposite effects. All seven co-morbid anxiety disorders predict higher neuroticism.
Patterns of co-morbidity between MDD and anxiety are consistent with findings from the US and European studies; the seven co-morbid anxiety disorders are heterogeneous when tested for association with various MDD features.
The 2009 novel H1N1 influenza pandemic had a significant impact on Shenzhen's population with 2063 laboratory-confirmed human H1N1 cases and five deaths being reported. We used parameters from two population-based surveys and the Shenzhen Influenza Surveillance System to estimate the total number of H1N1 influenza infections in Shenzhen in the 2009 pandemic. The attack rate of influenza-like illness (ILI) in family households was 11·2% (95% CI 9·4–13·0), with 80·2% (95% CI 77·8–82·5) seeking medical care. The ILI attack rate in workers was 38·1% (95% CI 34·3–41·7) with 72·5% (95% CI 66·9–78·0) seeking medical care. The average H1N1 positive rate in individuals reporting ILI and testing by polymerase chain reaction was 22·7%. A total of 611 000–768 000 people, or 4·7–5·9% of the Shenzhen population, are estimated to have experienced H1N1 influenza. The estimated total number of cases of H1N1 is likely to be 330 times greater than the number of laboratory-confirmed cases.
We have investigated the diffusion mechanism of Hg and Tl cations in cation-exchange process that has been used successfully for fabrication of Hg-based high-Tc superconducting films. Scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) was employed to map the distribution of Tl and Hg cations in films quenched at different stages of the cation exchange process. SEM/EDS mappings showed that the nonuniform distribution of Hg is visible in micrometer size on the surface of samples quenched after short-time (∼10min) Hg-annealing, but this nonuniformity disappears for longer-time (∼45 min) Hg-annealing samples. This change could be ascribed to different stages in Hg diffusion -- the former is the early stage when Hg is concentrated in the channels and the latter Hg-cations have already diffuse to grains. Our experimental results hence suggest that Hg-cations channel through defects in the films then diffuse into grains along a-b planes and vise versa for Tl-cations. The diffusion mechanism of anions (oxygen) in post annealing has also been discussed. Fluorine-doped Hg-1212 films were post annealed in flowing oxygen at 300 °C for several hours. Magnetic measurement has shown these samples are comprised pure overdoped Hg-1212 phase with smooth and sharp transition below 120 K, but resistivity vs. temperature measurement shows a kink at ∼123 K. This implies that the optimally doped Hg-1212 phase with higher Tc might be surrounded by overdoped Hg-1212 phase and their contribution to magnetization is minimized, thus the possible diffusion mechanism for anions is also through grain boundaries at a much larger time scale compared to the cations.
Previously we reported on a two-layer electrodeposition process of thallium oxide superconductors that showed transport critical current density above 106 A/cm2 at 77 K in zero field. In this article, we report our effort to convert an electrodeposited thick film of (Tl,Bi,Pb)2(Sr,Ba)2Ca1Cu2Ox to (Hg,Bi,Pb)2(Sr,Ba)2Ca1Cu2Ox by the cation-exchange process. We are also reporting magneto-optical imaging data on Tl oxide superconductor films, which are compared with YBCO. Magneto-optical imaging provides insight into the nature of current flow in the Tl oxide superconductor, and thus, will help us to improve the critical current density in bulk high-temperature superconductor wire or tape.
Boron was incorporated into GaN in order to determine its limits of solubility, its ability of reducing the lattice constant mismatch with 6H-SiC, as well as its effects on the structural and optical properties of GaN epilayers. BxGal-xN films were deposited on 6H-SiC (0001) substrates at 950 °C by low pressure MOVPE using diborane, trimethylgallium, and ammonia as precursors. A single phase alloy with x=0.015 was successfully produced at a gas reactant B/Ga ratio of 0.005. Phase separation into pure GaN and BxGal-xN alloy with x=0.30 was deposited for a B/Ga reactant ratio of 0.01. This is the highest B fraction of the wurtzite structure alloy ever reported. For B/Ga ratio ≥ 0.02, no BxGal-xN was formed, and the solid solution contained two phases: wurtzite GaN and BN based on the results of Auger and x-ray diffraction. The band edge emission of BxGal-xN varied from 3.451 eV for x=0 with FWHM of 39.2 meV to 3.465 eV for x=0.015 with FWHM of 35.1 meV. The narrower FWHM indicated that the quality of GaN epilayer was improved with small amount of boron incorporation.
Microstructure – mechanical property relations of 200 μm thick LIGA deposited Ni films have been investigated with a combination of optical cross-sectional microscopy and microsample tensile testing. Measurements of the grain size and morphology of nine different asdeposited films evidenced a predominantly columnar microstructure with significant variations in grain size. These as-deposited microstructural variations resulted in a range of Young's modulus, yield strength, and ultimate tensile strength values that are consistent with previously reported measurements, but these values did not appear to scale with the as-deposited microstructures. By contrast, significant changes in both the microstructure and mechanical properties were observed when these films were annealed at 800'C for 1 hour. Recrystallization and grain growth transformed the grain morphology from columnar to equiaxed, which resulted in a dramatic decrease in the tensile strength and corresponding increase in the ductility of the annealed films.
A new kind of TiO2 film catalyst was prepared by the Plasma-enhanced chemical vapor deposition (PECVD) method. The surface photovoltaic spectroscopy (SPS) results showed that its photoresponse was extended into the visible region. Photooxidation experiments showed that this kind of TiO2 film had high photocatalytic activity on degradation of phenol in aqueous solution. The influence of the thickness of TiO2 film on its photocatalytic activity was also discussed.
Mn-doped GaN films were grown by hydride vapor phase epitaxy(HVPE). structural measurements show that Mn may substitute Ga atoms in the GaN lattice. Ferromagnetism is observed in these HVPE grown Mn-doped GaN films, which may come from the GaxMn1−xN phase in the films.
Inlet start/unstart detection is one of the most important issues of hypersonic inlets and is also the foundation of protection controls of scramjets. In ground and flight tests, it is inevitably to introduce the sensor noises to the measurement system. How to overcome or weaken the influence of the sensor noises and the outer disturbances is an important issue to the control system of the engine. To solve this problem, the 2D inner steady flow of hypersonic inlets was numerically simulated in different freestream conditions and backpressures, and two different inlet unstart phenomena were analysed. The membership function for hypersonic inlet start/unstart can be obtained by using probabilistic output support vector machine, and the algorithm of multiple classifiers fusion is introduced. The variations of the classification accuracy with the intensity of the sensor noises and the number of the classifier were discussed respectively. In conclusion, it is useful to introduce the algorithm of support vector machine and multiple classifiers fusion to overcome or weaken the influence of the sensor noises on the classification accuracy of hypersonic inlet start/unstart. The number of the practical fusion classifiers needs a tradeoff between the fusion classification accuracy and the complexity of the classification system.