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Flexible electrode is an indispensable component of emerging portable, flexible, and wearable electronic devices. Although various flexible electrodes with different dimensions and functions have been explored, developing a new electrode material with excellent mechanical reliability and superior electrical performance remains a challenge. Here, a graphene-covered Cu composite electrode film with a total thickness of ∼100 nm is successfully fabricated onto a flexible polyimide substrate by means of a series of assembly methods including physical vapor deposition, chemical vapor deposition, and transfer technique. The composite electrode film on the flexible substrate exhibits evidently enhanced tensile strength, monotonic bending, and repeatedly bending fatigue reliability as well as electrical performance compared with that of the bared Cu film electrode. Such excellent mechanical performances are attributed to the role of the graphene coating in suppressing fatigue damage formation and preventing crack advance. It is expected that the chemical vapor-deposited graphene-covered Cu composite electrode would extend the potential ultrathin metal film electrode as the innovative electrode material for the next-generation flexible electronic devices.
We recently reported Cambrowania ovata Tang and Xiao in Tang et al., 2019, from the early Cambrian Hetang Formation in South China and interpreted it as a problematic animal fossil, possibly related to either sponges or bivalved arthropods (Tang et al., 2019). Slater and Budd (2019) contested our taxonomic identification and phylogenetic interpretation; instead, they claimed that Cambrowania ovata is a large acritarch referable to morphotaxon Leiosphaeridia Eisenack, 1958, and thus is not an animal. Here we refute their criticisms, clarify the differences between Cambrowania and Leiosphaeridia and other acritarchs, and reiterate why an animal affinity for Cambrowania cannot be ruled out.
Dongxiang common wild rice (Oryza rufipogon Griff., DXWR) is an important genetic resource for the improvement of cultivated rice. For the past three decades, great achievements have been made in the field of molecular marker development. Although structural variations (SVs) had been studied between DXWR and Nipponbare (Oryza sativa L. ssp. japonica), the development and application of SV markers in DXWR has not been reported. In this study, based on the genome-wide SV loci, we developed and synthesized a total of 195 SV markers that were evenly distributed across the 12 rice chromosomes. Then, these markers were tested for their stabilities and polymorphisms. Of these 195 markers, 147 (75.4%) were successfully amplified and displayed abundant polymorphisms between DXWR and Nipponbare. Meanwhile, through the genotyping of 20 rice varieties from 13 countries and areas, we concluded that these SV markers have a wide application prospect in the analysis of cultivated rice. Therefore, these molecular markers greatly enrich the number of markers available for DXWR, which will facilitate genomic research and molecular breeding for this important and endangered germplasm resource.
Sn–Sb alloy is an ideal candidate for lead-free solder; however, its performance has been inferior to that of Sn–Pb alloy. Here, the authors used ab initio molecular dynamics simulation to investigate the interatomic interaction in Sn–Sb-based lead-free solders. By calculating the electron density distribution, bond population, and partial density of states, the authors found that the Sn–Sb bonds are a mixture of nonlocalized metal and localized covalent bonds. The covalent bond between Sn and Sb is easy to break at higher temperatures, so Sn–Sb (6.4 wt%) had better fluidity than other studied Sn–Sb alloys. Furthermore, adding Cu or Ag into Sn–Sb alloys can decrease the strength of covalent bonds and stabilize the metal bonds, which improves the metallicity and wettability of the Sn–Sb–Cu and Sn–Sb–Cu–Ag systems when the temperature increases. These results are all in good agreement with experimental findings and have significant value for the development of new solder alloys.
The lower-middle Hetang Formation (Cambrian Stage 2–3) deposited in slope-basinal facies in South China is well known for its preservation of the earliest articulated sponge fossils, providing an important taphonomic window into the Cambrian Explosion. However, the Hetang Formation also hosts a number of problematic animal fossils that have not been systematically described. This omission results in an incomplete picture of the Hetang biota and limits its contribution to the understanding of the early evolution of animals. Here we describe a new animal taxon, Cambrowania ovata Tang and Xiao, new genus new species, from the middle Hetang Formation in the Lantian area of southern Anhui Province, South China. Specimens are preserved as carbonaceous compressions, although some are secondarily mineralized. A comprehensive analysis using reflected light microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and micro-CT reveals that the new species is characterized by a spheroidal to fusoidal truss-like structure consisting of rafter-like crossbars, some of which are secondarily baritized and may have been internally hollow. Some specimens have aperture-like structures that are broadly similar to oscula of sponges, whereas others show evidence of a medial split reminiscent of gaping carapaces. While the phylogenetic affinity of Cambrowania ovata Tang and Xiao, n. gen. n. sp. remains problematic, we propose that it may represent carapaces of bivalved arthropods or more likely sponges in early life stages. Along with other problematic metazoan fossils such as hyolithids and sphenothallids, Cambrowania ovata Tang and Xiao, n. gen. n. sp. adds to the diversity of the sponge-dominated Hetang biota in an early Cambrian deepwater slope-basinal environment.
Chickenpox is a common acute and highly contagious disease in childhood; moreover, there is currently no targeted treatment. Carrying out an early warning on chickenpox plays an important role in taking targeted measures in advance as well as preventing the outbreak of the disease. In recent years, the infectious disease dynamic model has been widely used in the research of various infectious diseases. The logistic differential equation model can well demonstrate the epidemic characteristics of epidemic outbreaks, gives the point at which the early epidemic rate changes from slow to fast. Therefore, our study aims to use the logistic differential equation model to explore the epidemic characteristics and early-warning time of varicella. Meanwhile, the data of varicella cases were collected from first week of 2008 to 52nd week of 2017 in Changsha. Finally, our study found that the logistic model can be well fitted with varicella data, besides the model illustrated that there are two peaks of varicella at each year in Changsha City. One is the peak in summer–autumn corresponding to the 8th–38th week; the other is in winter–spring corresponding to the time from the 38th to the seventh week next year. The ‘epidemic acceleration week’ average value of summer–autumn and winter–spring are about the 16th week (ranging from the 15th to 17th week) and 45th week (ranging from the 44th to 47th week), respectively. What is more, taking warning measures during the acceleration week, the preventive effect will be delayed; thus, we recommend intervene during recommended warning weeks which are the 15th and 44th weeks instead.
The aim of this article was to investigate the mechanism of appetite suppression induced by high-fat diets (HFD) in blunt snout bream (Megalobrama amblycephala). Fish (average initial weight 40·0 (sem 0·35) g) were fed diets with two fat levels (6 and 11 %) with four replicates. HFD feeding for 30 d could significantly increase the weight gain rate, but feeding for 60 d cannot. Food intake of M. amblycephala began to decline significantly in fish fed the HFD for 48 d. HFD feeding for 60 d significantly reduced the expression of neuropeptide Y and elevated the expression of cocaine- and amphetamine-regulated transcript (CART), actions both in favour of suppression of appetite. The activation of fatty acid sensing was partly responsible for the weakened appetite. In addition, inflammatory factors induced by the HFD may be involved in the regulation of appetite by increasing the secretion of leptin and then activating the mammalian target of rapamycin (mTOR). Lipopolysaccharide (LPS, 2·0 mg/kg of fish weight) was administered to induce inflammation, and sampling was performed after 3, 6, 9, 12, 18, 24 and 48 h of LPS injection. Within 6–24 h of LPS injection, the food intake and appetite of M. amblycephala decreased significantly, whereas the mRNA expression of leptin and mTOR increased significantly. Our results indicate that inflammatory cytokines may be the cause of appetite suppression in M. amblycephala fed a HFD.
Nacre-mimetic (PE/TiO2)4 nanolayered composites (NLCs) with the nanocrystalline TiO2 layer thickness less than 30 nm and different thickness ratios of inorganic/organic layers were successfully prepared by using layer-by-layer self-assembly and chemical bath deposition method. Mechanical properties, especially fatigue properties of the NLCs with different thickness ratios were evaluated. The elastic modulus, hardness and fracture toughness, strain amplitude to fatigue limits of the NLCs reached 27.78 ± 5.69 GPa, 1.33 ± 0.31 GPa, and 4.16 ± 0.20 MPa m1/2, respectively. Fatigue performance of the NLCs in the high and low cycle fatigue regimes was optimized by tailoring the thickness ratio of the TiO2/PE layers. The PE/TiO2 NLCs with the larger thickness ratio of ∼3 has the high fatigue limit (the critical strain amplitude of 0.0853%) in the high-cycle fatigue regime, while that with the smaller thickness ratio of ∼1 and ∼0.5 are of the good fatigue strength in the low-cycle fatigue regime. The basic mechanism for the enhanced fatigue performance is elucidated.
In this paper the asymmetric shock reflection configurations in two-dimensional steady flows have been studied theoretically. For an overall Mach reflection, it is found that the horizontal distance between both triple points in the Mach stem is related to the angles of two slip streams. Based on the features of the converging stream tube, several assumptions are put forward to perform better the wave configurations near the slip streams. Therefore, we present an analytical model here to describe the asymmetric overall Mach reflection configurations which agrees well with the computational and experimental results.
AMS radiocarbon measurements were started at Peking University in 1992 with a modified HICONEX 834 ion source. Some archaeological samples were measured at a sensitivity of 10−14 with ca. 1.7% precision for modern samples. We have made many improvements in our first two years of operation: a high-intensity Cs sputtering ion source was installed; the graphite sample preparation technique was investigated; and the system stability has been improved. The blank sample background is currently ca. 0.006 MC and a precision within 1% can be reached for modern samples. Geological, archaeological, environmental and biomedical samples can be measured routinely. We present some typical applications.
To study the transition from the Paleolithic to the Neolithic period and its duration, samples of charcoal, bone, flowstone and shells excavated from Bailiandong and Miaoyan caves, Guangxi Zhuang autonomous region, South China were dated using the Peking University AMS facility and liquid scintillation counter. The remains excavated from these sites show typical characteristics of the transition from the Paleolithic to the Neolithic. Radiocarbon dating results show a rapid transition from ca. 20 to 10 ka bp.
SG-III laser facility is now the largest laser driver for inertial confinement fusion research in China. The whole laser facility can deliver 180 kJ energy and 60 TW power ultraviolet laser onto target, with power balance better than 10%. We review the laser system and introduce the SG-III laser performance here.
The 〈001〉-textured 36Pb(In1/2Nb1/2)O3–30Pb(Mg1/3Nb2/3)O3–34PbTiO3 (36PIN–30PMN–34PT) ceramics were successfully prepared by the templated grain growth method using BaTiO3 (BT) templates with an average edge length of 10 μm and a thickness of about 0.5 μm. The highest Lotgering factor of 95% has been achieved for the textured ceramics with 5 wt% BT templates sintered at 1240 °C. The Curie temperature (TC) and dielectric constant (εr) of the textured 36PIN–30PMN–34PT ceramics were 225 °C and 2850, respectively. The piezoelectric constant d33 of the textured samples was 780 pC/N and almost 2 times higher than that of random 36PIN–30PMN–34PT samples. The planar mode electromechanical coupling coefficient kp was 59% for the textured samples. Unipolar strain-field measurements for the textured ceramics exhibited 0.34% strain at 4 kV/mm.
Ultra thin films of chromia (Cr2O3), less than 3 nm thick, grown epitaxial on α-Al2O3 (sapphire), and are thus compressively strained in-plane. The resulting films show evidence of some magnetic ordering above the Néel temperature of chromia (307 K). The observed higher temperature hysteresis effect observed are very likely a strain effect, and not associated with the typical antiferromagnetic ordering expected of chromia.
Predator–prey interactions play major and direct roles in the structuring of zooplankton communities. Asplanchna usually predates ciliates, rotifers, cladocerans and sometimes even copepods, its predation may drive not only the ecological, but also the evolutionary dynamics of prey populations. In the present study, the life-table demography and the population growth of Asplanchna brightwelli were investigated at four temperatures (16, 20, 24 and 28°C) using Brachionus angularis as prey at four densities (10, 20, 30 and 40 ind.mL−1). The results showed that temperature affected significantly all the life-table demographic parameters (age-specific survivorship and fecundity, average lifespan, life expectancy at hatching, generation time, net reproductive rate and intrinsic rate of population increase) and the population growth rate obtained from the population growth studies, prey density affected the generation time, the net reproductive rate, the intrinsic rate of population increase and the population growth rate, and the interaction between temperature and prey density affected the generation time and the population growth rate. Both the average lifespan and the life expectancy at hatching were the longest at 16°C, the generation times were longer at lower temperatures (16 and 20°C) and higher prey densities (30 and 40 ind.mL−1), the net reproductive rates were higher at lower temperatures (16 and 20°C) and 20–40 ind.mL−1 of B. angularis, and the population growth rates were higher at 20°C under 20–40 ind.mL−1 of B. angularis.
Owing to the limited regenerative capacity of cartilage tissue, cartilage repair remains a challenge in clinical treatment. Tissue engineering has emerged as a promising and important approach to repair cartilage defects. It is well known that material scaffolds are regarded as a fundamental element of tissue engineering. Novel biomaterial scaffolds formed by self-assembling peptides consist of nanofibre networks highly resembling natural extracellular matrices, and their fabrication is based on the principle of molecular self-assembly. Indeed, peptide nanofibre scaffolds have obtained much progress in repairing various damaged tissues (e.g. cartilage, bone, nerve, heart and blood vessel). This review outlines the rational design of peptide nanofibre scaffolds and their potential in cartilage tissue engineering.
To determine whether plastic-hardening behavior occurs in metal nanowires, an atomistic simulation was performed to investigate the tension process in a bicrystal Cu nanowire. The results indicate that bicrystal Cu nanowires exhibit strain-hardening behavior, unlike their single-crystal counterparts. The strain-hardening behavior is related to the orientation of two crystal grains, and the number of atoms determines whether strain-hardening behavior occurs in the asymmetrically tilted bicrystal Cu nanowires. Strain hardening occurs in almost bicrystal Cu nanowires with different orientation angles. The initial yield stress is determined by the grain whose orientation angle is closer to 45° among the two crystal grains, resulting in a high value of the tilting tendency factor, and thus making it easier to generate slip.
The mouse sperm genome is resistant to in vitro heat treatment, and embryos derived from heated sperm can support full-term embryonic development, but the blastocyst rate and implantation rate are lower compared to embryos derived from fresh sperm. In the present study, the patterns of DNA methylation, histone H4K12 (ACH4K12) acetylation, H3K9 trimethylation (H3K9-TriM), and H3K27 trimethylation (H3K27-TriM) in preimplantation embryos derived from 65°C-heated sperm were investigated. Although no evident changes in global DNA methyaltion, histone H4K12 (ACH4K12) acetylation, and H3K9 trimethylation (H3K9-TriM) were found, significantly lower levels of H3K27-TriM, which was thought to be one of the reasons for low efficiency of mouse cloning, were found in the inner cell mass of heated-sperm derived blastocysts. Thus, defective modification of H3K27-TriM might contribute to compromised development of embryos derived from heated sperm.
New techniques and procedures for measuring Poisson's ratio of MEMS materials are presented. Tensile specimens of polysilicon that are 3.5 μm thick are pulled in a small test machine that has a linear air bearing to eliminate friction. Biaxial strain is measured directly by laser-based interferometry from four gold lines deposited on the specimen surface. The value of Poisson's ratio for vapor-deposited polysilicon is 0.22 +/- 0.01 as determined from 19 tests..