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In this paper, instabilities in the flow over a circular cylinder of diameter
with dual splitter plates attached to its rear surface are numerically investigated using the spectral element method. The key parameters are the splitter plate length
, the attachment angle
and the Reynolds number
. The presence of the plates was found to significantly modify the flow topology, leading to substantial changes in both the primary and secondary instabilities. The results showed that the three instability modes present in the bare circular cylinder wake still exist in the wake of the present configurations and that, in general, the occurrences of modes A and B are delayed, while the onset of mode QP is earlier in the presence of the splitter plates. Furthermore, two new synchronous modes, referred to as mode A
and mode B
, are found to develop in the wake. Mode A
is similar to mode A but with a quite long critical wavelength. Mode B
shares the same spatio-temporal symmetries as mode B but has a distinct spatial structure. With the exception of the case of
, mode A
persists for all configurations investigated here and always precedes the transition through mode A. The onset of mode B
. The characteristics of all the transition modes are analysed, and their similarities and differences are discussed in detail in comparison with the existing modes. In addition, the physical mechanism responsible for the instability mode B
is proposed. The weakly nonlinear feature of mode B
, as well as that of mode A
, is assessed by employing the Landau model. Finally, selected three-dimensional simulations are performed to confirm the existence of these two new modes and to investigate the nonlinear evolution of the three-dimensional modes.
The onset of thermal convection in a rapidly rotating spherical shell is studied by linear stability analysis based on the fully compressible Navier–Stokes equations. Compressibility is quantified by the number of density scale heights
, which measures the intensity of density stratification of the motionless, polytropic base state. The nearly adiabatic flow with polytropic index
is considered, where
is the adiabatic polytropic index. By investigating the stability of the base state with respect to the disturbance of specified wavenumber, the instability process is found to be sensitive to the Prandtl number
. For large
, the quasi-geostrophic columnar mode loses stability first; while for relatively small
a new quasi-geostrophic compressible mode is identified, which becomes unstable first under strong density stratification. The inertial mode can also occur first for relatively small
and a certain intensity of density stratification in the parameter range considered. Although the Rayleigh numbers
for the onsets of the quasi-geostrophic compressible mode and columnar mode are different by several orders of magnitude, we find that they follow very similar scaling laws with the Taylor number. The critical
for convection onset is found to be always positive, in contrast with previous results based on the widely used anelastic model that convection can occur at negative
. By evaluating the relative magnitude of the time derivative of density perturbation in the continuity equation, we show that the anelastic approximation in the present system cannot be applied in the small-
Heavy metal contamination in the paddy soils of China is a serious concern because of its health risk through transfer in food chains. A field experiment was conducted in 2014–2015 to investigate the long-term effects of different biochar amendments on cadmium (Cd) and arsenic (As) immobilisation in a contaminated paddy field in southern China. Two types of biochar, a rice-straw-derived biochar (RB) and a coconut-by-product-derived biochar (CB), were amended separately to determine their impacts on rice yield and their efficacy in reducing Cd and As in rice. The two-year field experiment showed that biochar amendments significantly improved the rice yields and that CB is superior to RB, especially in the first growth season. Using a large amount of biochar amendment (22.5tha–1) significantly increased soil pH and total organic carbon, and concomitantly decreased the Cd content in rice grains over the four growth seasons, regardless of biochar type and application rate. Arsenic levels in rice were similar to the control, and results from this study suggest that there was a sustainable effect of biochar on Cd sequestration in soil and reduction of Cd accumulation in rice for at least two years. Biochar amendment in soil could be considered as a sustainable, reliable and cost-effective option to remediate heavy metal contamination in paddy fields for long periods.
The 2Cr13/316L multilayered composite plates were fabricated by hot rolling with recycle heating step. The effect of rolling reductions on microstructure and properties was investigated. The 2Cr13 layer consists of martensite and lath ferrite, but the middle layer has less ferrite than both sides. The content and grains of ferrite increase with the increase of the reduction and number of reheating, which leads to a decrease in the hardness of the 2Cr13 layer. The hardness of the 2Cr13 layer is determined by the volume ratio of martensite and ferrite. Tensile strength of the specimens with the rolling reduction of 72% and 82% reached 815.8 MPa and 763.4 MPa, while elongations were 20% and 20.8%, respectively. With the increase of the rolling reduction, the fracture mode also changed from cleavage fracture to dimple fracture. There were no cracks and delamination when the 2Cr13/316L composite plate bent to 130° and 180°, which indicated better interfacial bonding.
We previously reported four heterozygous missense mutations of MYH7, KCNQ1, MYLK2, and TMEM70 in a single three-generation Chinese family with dual Long QT and hypertrophic cardiomyopathy phenotypes for the first time. However, the clinical course among the family members was various, and the potential myocardial dysfunction has not been investigated.
The objective of this study was to investigate the echocardiographic and electrocardiographic characteristics in a genetic positive Chinese family with hypertrophic cardiomyopathy and further to explore the association between myocardial dysfunction and electric activity, and the identified mutations.
A comprehensive echocardiogram – standard two-dimensional Doppler echocardiography and three-dimensional speckle tracking echocardiography – and electrocardiogram were obtained for members in this family.
As previously reported, four missense mutations – MYH7-H1717Q, KCNQ1-R190W, MYLK2-K324E, and TMEM70-I147T – were identified in this family. The MYH7-H1717Q mutation carriers had significantly increased left ventricular mass indices, elevated E/e’ ratio, deteriorated global longitudinal stain, but enhanced global circumferential and radial strain compared with those in non-mutation patients (all p<0.05). The KCNQ1-R190W carriers showed significantly prolonged QTc intervals, and the MYLK2-K324E mutation carriers showed inverted T-waves (both p<0.05). However, the TMEM70-I147T mutation carriers had similar echocardiography and electrocardiographic data as non-mutation patients.
Three of the identified four mutations had potential pathogenic effects in this family: MYH7-H1717Q was associated with increased left ventricular thickness, elevated left ventricular filling pressure, and altered myocardial deformation; KCNQ1-R190W and MYLK2-K324E mutations were correlated with electrocardiographic abnormalities reflected in long QT phenotype and inverted T-waves, respectively.
The purpose of this study was to investigate whether hesitant or preoccupied people (state-oriented) have different goal content and motives compared to initiative or disengaged people (action-oriented). People rated the degree of autonomous versus controlled feelings for extrinsic or intrinsic types of goals. Results showed that action-oriented people had a higher autonomous motive than state-oriented people for intrinsic goals, but not for extrinsic goals. Moreover, action-oriented individuals were related to a more internalised goal content (intrinsic goal) than state-oriented individuals. Implications for goal internalisation are discussed.
The influences of non-Oberbeck–Boussinesq (NOB) effects on flow instabilities and bifurcation characteristics of Rayleigh–Bénard convection are examined. The working fluid is air with reference Prandtl number
and contained in two-dimensional rigid cavities of finite aspect ratios. The fluid flow is governed by the low-Mach-number equations, accounting for the NOB effects due to large temperature difference involving flow compressibility and variations of fluid viscosity and thermal conductivity with temperature. The intensity of NOB effects is measured by the dimensionless temperature differential
. Linear stability analysis of the thermal conduction state is performed. An
scaling of the leading-order corrections of critical Rayleigh number
and disturbance growth rate
due to NOB effects is identified, which is a consequence of an intrinsic symmetry of the system. The influences of weak NOB effects on flow instabilities are further studied by perturbation expansion of linear stability equations with regard to
, and then the influence of aspect ratio
is investigated in detail. NOB effects are found to enhance (weaken) flow stability in large (narrow) cavities. Detailed contributions of compressibility, viscosity and buoyancy actions on disturbance kinetic energy growth are identified quantitatively by energy analysis. Besides, a weakly nonlinear theory is developed based on centre-manifold reduction to investigate the NOB influences on bifurcation characteristics near convection onset, and amplitude equations are constructed for both codimension-one and -two cases. Rich bifurcation regimes are observed based on amplitude equations and also confirmed by direct numerical simulation. Weakly nonlinear analysis is useful for organizing and understanding these simulation results.
We report a novel tip-type field emission (FE) emitter by synthesizing the few-layer graphene (FLG) flakes on tip of nichrome (8020) wire (ϕ≈80 μm) by microwave plasma enhanced chemical vapor deposition(PECVD). These resultant random arrays of free-standing FLG flakes are aligned vertically to the substrate surface in a high-density and stacked to each other to form several larger “flower-like” agglomerates in spherical shapes. The FE performance of the tip-type FLG flakes emitter shows a low threshold field of 0.55 V/μm, a large field enhancement factor of 9455 ± 46, a large field emission current density of 22.18 A/cm2 at 2.70 V/μm, and an excellent field emission stability at high emission current densities (6.93 A/cm2). It can be used in variety of applications that include cathode-ray tube monitors, X-ray sources, electron microscopes, and other vacuum electronic applications.
A new band-reject frequency-selective surface (FSS) based on dual-band near-zero refractive index metamaterial (ZIM) design is presented in this paper. Consisting of a planar array of complementary dual-layer symmetry resonant ring, the proposed FSS exhibits a high-selective band-reject filtering response. From the viewpoint of effective medium, the subwavelength FSS is characterized by near-zero effective magnetic permeability and near-zero effective electric permittivity in two different operational bands, respectively. The corresponding resonant behavior and E-field distributions are analyzed in detail. A prototype of the proposed FSS working in X-band is fabricated and measured. The simulation and experiment results verify the effectiveness and correctness of the ZIM-based design method.
To explore effective ways to decrease soil CO2 emission and increase winter wheat grain yield in the North China Plain, a field experiment was conducted using two planting systems (wide-precision planting and conventional-cultivation planting) and two straw mulching rates (0 and 0.6 kg m−2) to study carbon emission, carbon cumulative emission flux, grain yield and yield carbon utilization efficiency. In the 2013–2014 and 2014–2015 winter wheat growing seasons, CO2 emission rate and cumulative CO2-C fluxes following straw mulching treatment were significantly lower than those following non-mulching treatments, whereas the yield carbon utilization efficiency was significant higher following straw mulching treatment. Straw mulching significantly reduced winter wheat grain yield, which was mainly due to the significant decrease in spike numbers and 1000-kernel weight. However, wide-precision planting system significantly increased winter wheat grain yields by increasing spike numbers under straw mulching conditions. Therefore, wide-precision planting system could compensate for the reduction in winter wheat grain yield under carbon sequestration conditions in the North China Plain.
There has been a lot of study on the SOR-like methods for solving the augmented system of linear equations since the outstanding work of Golub, Wu and Yuan (BIT 41(2001)71-85) was presented fifteen years ago. Based on the SOR-like methods, we establish a class of accelerated SOR-like methods for large sparse augmented linear systems by making use of optimization technique, which will find the optimal relaxation parameter ω by optimization models. We demonstrate the convergence theory of the new methods under suitable restrictions. The numerical examples show these methods are effective.
The purpose of the present study was to examine the influence of maternal pre-pregnancy BMI and gestational weight gain (GWG) on initiation and duration of infant breast-feeding in a prospective birth cohort study.
Breast-feeding information was collected at 1, 3, 6 and 12 months postpartum. The association of pre-pregnancy BMI and GWG with delayed lactogenesis II and termination of exclusive breast-feeding was assessed with logistic regression analysis. The risk of early termination of any breast-feeding during the first year postpartum was assessed with Cox proportional hazards models.
Urban city in China.
Women with infants from the Ma’anshan Birth Cohort Study (n 3196).
The median duration of any breast-feeding in this cohort was 7·0 months. Pre-pregnancy obese women had higher risks of delayed lactogenesis II (risk ratio=1·89; 95 % CI 1·04, 3·43) and early termination of any breast-feeding (hazard ratio=1·38; 95 % CI 1·09, 1·75) adjusted for potential maternal and infant confounders, when compared with normal-weight women. No differences in breast-feeding initiation or duration of exclusive breast-feeding according to pre-pregnancy BMI were found. Moreover, GWG was not associated with any poor breast-feeding outcomes.
The present study indicated that pre-pregnancy obesity increases the risks of delayed lactogenesis II and early termination of any breast-feeding in Chinese women.
The fruit plus accessory parts, and thus not only the fruit or seed, is the diaspore in some species of flowering plants. Atriplex centralasiatica, a summer annual salt-secreting cold-desert halophyte of central Asia that produces flat and humped diaspores, is such a species. The dispersal/germination units of this diaspore-heteromorphic species are fruits enclosed in persistent ‘bracteoles’. Germination of black and brown fruits (i.e. ‘bracteoles’ removed) of this species has been studied in some detail previously, but little attention has been given to the germination biology of the intact diaspores. The aim of this study was to compare the germination biology of the intact diaspores of A. centralasiatica, and their fates in the field during 12 months on the soil surface and buried at 5-cm depth. Fresh flat diaspores germinated to 42.7–51.3% in light (12-h photoperiod) and to 16.0–59.3% in constant dark, over a temperature range of 15–20/30°C, while no freshly matured humped diaspores did so under any temperature/light regime. Neither gibberellin (GA3) nor potassium nitrate (KNO3) had an effect on germination of either diaspore. Both diaspores readily imbibed water, and removal of ‘bracteoles’ released most of the dormancy. Thus, the ‘bracteoles’ are primarily responsible for diaspore dormancy in A. centralasiatica. Humped diaspores persisted for a longer period in the soil than flat ones. The germination requirements of intact natural dispersal/germination units of A. centralasiatica differ from those previously reported for fruits of this species.
In order to identify the density and material type, high energy protons, electrons, and heavy ions are used to radiograph dense objects. The particles pass through the object, undergo multiple coulomb scattering, and are focused onto an image plane by a magnetic lens system. A modified beam line at the Institute of Modern Physics of the Chinese Academy of Sciences has been developed for heavy-ion radiography. It can radiograph a static object with a spatial resolution of about 65 µm (1 σ). This paper presents the heavy-ion radiography facility at the Institute of Modern Physics, including the beam optics, the simulation of radiography by Monte Carlo code and the experimental result with 600 MeV/u carbon ions. In addition, dedicated beam lines for proton radiography which are planned are also introduced.
Nanobiosensors have drawn significant research interest in recent years owing to the advantages of label-free, electrical detection. However, nanobiosensors fabricated by bottom-up process are limited in terms of yield and device uniformity due to the challenges in assembly. Nanobiosensors fabricated by top-down process, on the other hand, exhibit better uniformity but require time and costly processes and materials to achieve the critical dimensions required for high sensitivity. In this report, we introduce a top-down nanobiosensor based on polysilicon nanoribbon. The polysilicon nanoribbon devices can be fabricated by conventional photolithography with only materials and equipments used in the standard CMOS process, thus resulting in great time and cost efficiency, as well as scalability. The devices show great response to pH changes with a wide dynamic range and high sensitivity. Biomarker detection is also demonstrated with clinically relevant sensitivity. Such results suggest that polysilicon nanoribbon devices exhibit great potential toward a highly efficient, reliable and sensitive biosensing platform.
A GPU-based acceleration for the direct boundary integral equation method (GPU-DBIE) to extrapolate solar coronal magnetic fields is developed, which is about 1000 times faster than the original DBIE. The 3-d coronal magnetic field is reconstructed for NOAA 11158 on 14-Feb-2011 with the SDO/HMI vector magnetogram as bottom boundary condition. The extrapolated results agree well with the projected SDO/AIA, EUV loops and the STEREO EUV sideviews, which verifies the correctness of our GPU-DBIE method. It is also found that the group of bright EUV loops along magnetic neutral lines agree well with current lines, which may have played an important role in the flare process of the active region.
Kashin-Beck disease (KBD) is a chronic endemic osteoarthropathy, which mainly occurs in West and Northeast China. Epidemiological studies suggest that Se deficiency is an important environmental factor for the incidence of KBD. Glutathione peroxidase 4 (GPx4) belongs to the glutathione peroxidase family, which is crucial for optimal antioxidant defences. Our purpose is to investigate the putative association between GPx4 polymorphisms and the risk of KBD. Restriction fragment length polymorphism-PCR was used to detect two SNP (rs713041, rs4807542) in 219 cases and 194 controls in Han Chinese subjects, and quantitative analysis for the GPx4 mRNA level was performed by the real-time PCR method. The results revealed that linkage disequilibrium existed in the two SNP. A significant difference was observed in the haplotype A-T (P = 0·0066) of GPx4, which was obviously lower in the KBD cases (0·006 v. 0·032 %). Correlation analysis based on a single locus showed no association between each SNP and KBD risk. Furthermore, the GPx4 mRNA level was dramatically lower in the blood of KBD patients. Overall, our finding indicated GPx4 polymorphisms and decreased mRNA level may be related to the development of KBD in the Chinese population, suggesting GPx4 as a possible candidate susceptibility gene for KBD.