Using the Dirac–Heisenberg–Wigner formalism, effects of the asymmetric pulse shape on the generation of electron-positron pairs in three typical polarized fields, i.e., linear, middle elliptical and circular fields, are investigated. Two kinds of asymmetries for the falling pulse length, short and elongated, are studied. We find that the interference effect disappears with the shorter pulse length and that the peak value of the momentum spectrum is concentrated in the center of the momentum space. In the case of the extending falling pulse length, a multiring structure without interference appears in the momentum spectrum. Research results show that the momentum spectrum is very sensitive to the asymmetry of the pulse as well as to the polarization of the fields. We also find that the number density of electron-positron pairs under different polarizations is sensitive to the asymmetry of the electric field. For the short falling pulse, the number density can be significantly enhanced by over two orders of magnitude. These results could be useful in planning high-power and/or high-intensity laser experiments.

The aim of this study was to investigate the in vivo degradation mechanism and the mechanical properties of poly(lactide-co-glycolide)/beta-tricalcium phosphate (PLGA/β-TCP) composite anchors. Anchors composed of PLGA and β-TCP were implanted in the dorsal subcutaneous tissue of beagle dogs for 6, 12, 16, and 26 weeks. The degradation of the materials was evaluated by measuring the changes in thermal behavior, crystallinity, and mechanical properties. Scanning electron microscope (SEM) was used to observe the surface and longitudinal section of the material. The evaluation of mechanical strength retention and degradation properties suggest that the addition of β-TCP particles efficiently enhances their mechanical properties and thermal characteristics and delays their degradation rate. By analyzing the results of SEM, X-ray diffraction, and differential scanning calorimetry, we can infer that after 12 weeks, the connection between β-TCP and PLGA becomes less compact, which accelerates the decline of mechanical strength.

By solving the coupled equations of the electromagnetic field and electrostatic potential, we investigate solitary waves in an asymmetric electron–positron plasma and/or electron–positron–ion plasmas with delicate features. It is found that the solutions of the coupled equations can capture multipeak structures of solitary waves in the case of cold plasma, which are left out by using the long-wavelength approximation. By considering the effect of ion motion with respect to non-relativistic and ultra-relativistic temperature plasmas, we find that the ions’ mobility can lead to larger-amplitude solitary waves; especially, this becomes more obvious for a high-temperature plasma. The effects of asymmetric temperature between electrons and positrons and the ion fraction on the solitary waves are also studied and presented. It is shown that the amplitudes of solitary waves decrease with positron temperature in asymmetric temperature electron–positron plasmas and decrease also with ion concentration.

As the currently only available molluscicide, niclosamide has been widely used for snail control for over 2 decades in China. There is therefore a concern about the emergence of niclosamide-resistant snail populations following repeated, extensive use of the chemical. The purpose of this study was to investigate the likelihood of niclosamide resistance in Oncomelania hupensis in China. Active adult O. hupensis snails derived from 20 counties of 10 schistosomiasis-endemic provinces of China, of 10 snails in each drug concentration, were immersed in solutions of 1, 0·5, 0·25, 0·125, 0·063, 0·032, 0·016 and 0·008 mg L−1 of a 50% wettable powder of niclosamide ethanolamine salt (WPN) for 24 and 48 h at 25 °C, and the median lethal concentration (LC50) was estimated. Then, the 24- and 48-h WPN LC50 values were compared with those determined in the same sampling sites in 2002. The results indicated that the 24- and 48-h WPN LC50 values for O. hupensis were not significantly different from those determined in 2002 (P = 0·202 and 0·796, respectively). It is concluded that the current sensitivity of O. hupensis to niclosamide has not changed after more than 2 decades of repeated, extensive application in the main endemic foci of China, and there is no evidence of resistance to niclosamide detected in O. hupensis.

Polycrystalline Ba8Ga16MgxGe30−x compounds were synthesized by combining solid-state reaction with spark plasma sintering (SPS) method. The structural and electronic properties of Mg-substituted Ge type-I clathrate phase Ba8Ga16MgxGe30−x (x = 1, 2, 3, 4) were investigated experimentally and theoretically. Theoretically structural and electronic properties of Ba8Ga16MgxGe30−x were calculated by first-principles method based on the density-functional theory. The results indicate a strong preference for the occupation of the 6c sites by Mg. It is found that Mg substitution for Ge can lower the melting points and bulk modulus of this system. The formation energies and the binding energies decrease with increasing Mg content, suggesting that the Mg-doped Ba8Ga16Ge30 clathrates are stable in a limited range of composition. The calculated results show that these alloys are all indirect gap semiconductors and the values of band gap increase with the increase of Mg content. All specimens exhibit the behavior of the p-type conduction, which is originated from the presence of a shallow acceptor energy level. The electrical conductivity and the room-temperature carrier mobility decrease with increasing Mg content, while the room-temperature carrier concentration increases with increasing Mg content.

Seven isoenergetic semi-purified test diets containing graded levels of protein ranging from 20 to 50% were formulated using fish meal and casein as the protein sources. Test diets were fed to triplicate groups of Barbodes caldwelli juveniles with initial body weights of 1.26±0.02 g for eight weeks. The results indicated no significant effect of dietary protein levels on survival rate, relative weight of the viscera and relative weight of the liver in the juvenile fish. The weight gain and specific growth rate of the fish were found to be greater as dietary protein levels increased from 20 to 35%, but were not affected significantly as dietary protein level increased from 35 to 50%. Feed efficiencies did not differ significantly when fish were fed diets with protein levels from 30 to 50%, but were significantly higher than those of fish fed diets with protein levels of 20 and 25%. The protein efficiency ratio (PER) was negatively correlated with diet protein level (x) (PER=3.006−0.03251x, R=0.9366). There was no significant effect of dietary protein levels on carcass moisture, crude protein and ash. However, carcass lipid levels (L) decreased with an increase in dietary protein level (x) (L=8.2169−0.0458x, R=0.8551). There was no significant variation in hepatopancreas protease activity among the tests. Intestine protease activity and hepatopancreas amylase activity were increased to some extent, and then decreased as dietary protein levels continued to rise. The intestine amylase activity (IAA) of the juveniles was negatively correlated with dietary protein level (x) (IAA=84.625−0.9147x, R=0.8463). It was estimated that the suitable protein level for the B. caldwelli juvenile is 34% (the broken-line model was used to regress the relationship of the weight gain of the juvenile and dietary protein level).

Early studies have shown that some mouse cumulus–oocyte complexes (COCs) stored at room temperature for 24 h still retained full developmental potential. In this study, we stored denuded mouse oocytes (DOs) at room temperature (25 °C) for 24 h and activated these oocytes with 10 mM SrCl2 or fertilized the oocytes by IVF. We found that nearly half of the DOs stored at room temperature for 1 day can be fertilized normally by IVF and that two foster mothers gave birth to seven pups. Embryos from stored oocytes were cultured in CZB medium with or without 1 μg/ml 17β-estradiol (E2). The numbers of embryo that developed to morula/blastocyst stage after parthenogenetic activation and IVF were significantly increased when E2 was added to the culture (p < 0.05). These results suggest that E2 might improve mouse embryo development in vitro. The birth of seven agouti pups and their healthy growth indicated that the storage of DOs at room temperature for 1 day may be a practical procedure for mammalian reproduction.

The development of near-isogenic lines (NILs) is an important fundamental step in the cloning of quantitative trait loci (QTL) and molecular marker assisted breeding. In the present study, NILs for two major QTLs of basal root thickness (BRT) and 1000-grain-weight (TGW) were obtained by molecular marker-assisted selection (MAS) through foreground selection for target QTL and background selection in three backcross generations (BC1F1, BC2F1 and BC3F1). After phenotypic evaluation in the BC3F2 generation, nine BRT QTL-NILs with BRT ranges of 1.07–1.16 mm (6.11–15.18% greater than the recurrent parent) and an average recovery ratio of genetic background (RRGB) of 97.22%, and 11 TGW QTL-NILs with ranges of 21.25–26.25 g (7.05–32.16% greater than the recurrent parent) and 95.97% of RRGB, were selected.

The distribution of genetic diversity between Oryza sativa L. ssp. indica and O. sativa L. ssp. japonica covering different ecological zones in Yunnan was studied, and specific markers of indica/japonica subspecies, paddy/upland rice and different ecological zones were screened, using 36 microsatellite primers and 113 accessions in the Yunnan landrace rice core collection. The genetic diversity of japonica was higher than that of indica, and the ecological zone with the highest and smallest genetic diversity lay in south-east and north-east Yunnan, respectively. This distribution was consistent at morphological and isozyme levels with studies on the entire Yunnan rice resources and core collection. In addition, the results showed that, among 416 markers, there were six indica/japonica-specific markers, 15 specific markers for paddy/upland rice and three specific markers in different ecological zones. The main conclusions are that the landrace rice core collection in Yunnan genetically represents the entire landrace rice resources in Yunnan, the centre of genetic diversity at DNA level lies in south-east Yunnan, and the DNA differentiation between indica and japonica is small. Furthermore, microsatellite markers were useful for studying the genetic diversity, classification and ecotype of germplasm resources and their core collection.