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The parasite Fasciola hepatica is an important zoonotic parasite. The development of an animal model of F. hepatica's life cycle is critical for studying the biological characteristics of the parasite in snails and mammals. Eggs of F. hepatica of bovine origin were cultured, and metacercariae were obtained after infection of Galba pervia snails. The life cycle system of F. hepatica was initiated in 2 different animals by orally infecting rabbits, SD rats and Kunming mice with the metacercariae. The animals' survival after infection, parasite migration in the animals and pathological damage to the liver were observed. We discovered that rabbits died due to acute suppurative hepatitis 60–69 days after infection, and eggs were found in the feces on day 63 of infection. The liver of SD rats showed punctate lesions on day 3 of infection, and further changes occurred as the infection progressed. However, liver repair was observed at week 9. SD rats survived for more than a year after infection and continued the F. hepatica life cycle. The liver lesions in Kunming mice after infection were similar but more severe than those in SD rats. Death was observed on the 31st post-infection day. We discovered that while rabbits, SD rats and Kunming mice can all be used as animal models of F. hepatica, SD rats are more suitable experimental animals in terms of tolerance and pathological response.
Maternal supraphysiological estradiol (E2) environment during pregnancy leads to adverse perinatal outcomes. However, the influence of oocyte exposure to high E2 levels on perinatal outcomes remains unknown. Thus, a retrospective cohort study was conducted to explore the effect of high E2 level induced by controlled ovarian stimulation (COH) on further outcomes after frozen embryo transfer (FET). The study included all FET cycles (n = 10,581) between 2014 and 2017. All cycles were categorized into three groups according to the E2 level on the day of the human Chorionic Gonadotropin trigger. Odds ratios (ORs) and their confidence intervals (CIs) were calculated to evaluate the association between E2 level during COH and pregnancy outcomes and subsequent neonatal outcomes. From our findings, higher E2 level was associated with lower percentage of chemical pregnancy, clinical pregnancy, ongoing pregnancy, and live birth as well as increased frequency of early miscarriage. Preterm births were more common among singletons in women with higher E2 level during COH (aOR1 = 1.93, 95% CI: 1.22–3.06; aOR2 = 2.05, 95% CI: 1.33–3.06). Incidence of small for gestational age (SGA) was more common in both singletons (aOR1 = 2.01, 95% CI: 1.30–3.11; aOR2 = 2.51, 95% CI: 1.69–3.74) and multiples (aOR1 = 1.58, 95% CI: 1.03–2.45; aOR2 = 1.99, 95% CI: 1.05–3.84) among women with relatively higher E2 level. No association was found between high E2 level during COH and the percentage of macrosomia or large for gestational age. In summary, oocyte exposure to high E2 level during COH should be brought to our attention, since the pregnancy rate decreasing and the risk of preterm birth and SGA increasing following FET.
Two new species of egg parasitoids, Oobius saimaensis Yao and Mottern new species and Oobius fleischeri Yao and Duan new species (Hymenoptera: Encyrtidae), are described from eggs of Agrilus fleischeri Obenberger, 1925 (Coleoptera: Buprestidae). Agrilus fleischeri is a phloem-feeding woodborer of poplar (Populus Linnaeus; Salicaceae) in northeastern China. These two species can be distinguished morphologically as O. fleischeri has five tarsomeres and O. saimaensis has four tarsomeres. Although O. saimaensis is morphologically similar to its sympatric congener O. agrili Zhang and Hang, 2005, an important natural enemy of the invasive emerald ash borer, Agrilus planipennis Fairmaire, 1888, molecular phylogenetics and morphological data indicate that they are distinct species. Phylogenetic relationships among the new species and other closely related species are also inferred by using DNA sequence data from several ribosomal and mitochondrial genes. In addition, we expand the known distribution of Oobius primorskyensis Yao and Duan, 2016 to include South Korea.
The ‘Mystery Interval’ (MI, 17.5−14.5 ka) was the first stage of the last deglaciation, a key interval for understanding mechanisms of glacial–interglacial cycles. To elucidate possible causes of the MI, here we present three high-resolution, precisely dated oxygen-isotope records of stalagmites from Qingtian and Hulu Caves in China, reflecting changes in the East Asian summer monsoon (EASM) then. Based on well-established chronologies using precise 230Th dates and annual-band counting results, the two-cave δ18O profiles of ~7-yr resolution match well at decadal timescales. Both of the two-cave records document an abrupt weakening (2‰ of δ18O rise within 20 yr) in the EASM at ~16.1 ka, coinciding with the transition of the two-phased MI reconstructed from New Mexico's Lake Estancia. Our results indicate that the maximum southward displacement of the Intertropical Convergence Zone and associated southward shift of polar jet stream may generate this two-phase feature of the MI during that time. We also discover a linear relationship among decreasing EASM intensity, rising atmospheric CO2 and weakening Atlantic Meridional Overturning Circulation between the MI and Younger Dryas episodes, suggesting a strong coupling of atmospheric/oceanic circulations in response to the millennial-scale forcing, which in turn regulates global climate changes and carbon cycles.
CMOS-compatible fabrication and etching processes are often used in subwavelength grating structures manufacturing, it normally generates tapered sidewall profile of the gratings. In this work, we have studied the impacts on resonance mode characteristics of subwavelength grating structures due to the tapered sidewall profile, as well as grating with high aspect ratio. Our simulation results have revealed that both of these two factors play important roles on the resonance mode behavior of subwavelength grating devices. We also discussed the mechanism between the guided mode resonance and the grating cavity mode resonance. Our study will provide guidance for a series of integrated photonics devices applications, such as compact optical filter, photonics amplifier, and lasers, while the realistic subwavelength grating structure is considered.
One main difference between practical device and ideal design for subwavelength grating structure is the tapered sidewall profile of grating, which is normally obtained by the practical CMOS-compatible fabrication and etching process. Our work has investigated the impacts of tapered sidewall profile on the subwavelength grating wideband reflector characteristics. Both zero-contrast gratings (ZCG) and high- contrast gratings (HCG) are numerically investigated in detail and the results show a distinct differences of the impacts of tapered sidewall profile of grating. The simulation results reveal that this factor play a critical role in determining the reflection bandwidth, average reflectance, and the band edge. Our study has potential in guiding the utilization of subwavelength grating wideband reflector on application of a variety of nanophotonic devices and their integration, as well as to facilitate the design of the fabrication process on the control of tapered sidewall profile.
To investigate natural enemies of emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), in northeastern China, we conducted field surveys of ash (Fraxinus Linnaeus (Oleaceae)) trees in semi-natural forests and plantations at variable EAB densities from 2008 to 2013. Our surveys revealed a complex of natural enemies including eight hymenopteran parasitoids and two apparently parasitic Coleoptera, woodpeckers, and several undetermined mortality factors. Parasitoid complex abundance and its contribution to EAB mortality varied with the time of year, type of ash stands, and geographic regions. The egg parasitoid Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae) and the larval parasitoid Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae) were frequently observed in Jilin, Liaoning, and Heilongjiang provinces and in Beijing, but not in Tianjin. Spathius agrili Yang (Hymenoptera: Braconidae), however, was more prevalent near Beijing and further south in Tianjin. Larvae of two species of apparently parasitic beetle, Tenerus Laporte (Coleoptera: Cleridae) species and Xenoglena quadrisignata Mannerheim (Coleoptera: Trogossitidae), were also recovered attacking overwintering EAB in Liaoning Province, with Tenerus species being a dominant mortality agent (~13%). Our findings support the need to consider the geographic origin of insect natural enemies for EAB biocontrol, as well as an expanded foreign exploration for EAB natural enemies throughout its native range in Asia.
Monolayers of arrays of periodic polystyrene (PS) spheres are designed to couple onto the surface of cerium-doped lutetium-yttrium oxyorthosilicate scintillator to improve the light extraction efficiency. The enhancement of extraction efficiency up to 38% relative to the reference case without polystyrene spheres is achieved. Combining with the simulation for the transmission as well as its dispersion relation, detailed analysis of the effect of whispering gallery modes and diffraction on the extraction mechanism are given. As a result, the optimal diameter of 414 nm is obtained based on a trade-off between the transmission loss and the diffraction enhancement.
We present results of theoretical and experimental studies of whispering-gallery modes in optical microdisk resonators interacting with subwavelength dielectric particles. We predict theoretically and confirm by direct observations that, contrary to the generally accepted models, both peaks of the particle-induced doublet of resonances are red shifted with respect to the position of the initial resonance.
We have improved bio-inspired Moth eye nanostructures to enhance the scintillator materials external quantum efficiency significantly. As a proof of concept, we have demonstrated very high light output efficiency enhancement for Lu2SiO5:Ce3+ (LSO:Ce) film in large area. The X-ray mammographic instrument was employed to demonstrate the light output enhancement of the Lu2SiO5:Ce thin film with bio-inspired Moth eye-like nano photonic structures. Our work could be extended to other thin film scintillator materials and is promising to achieve lower patient dose, higher resolution image of human organs and even smaller scale medical imaging.
Antireflection with broadband and wide angle properties is important for a wide range of applications on photovoltaic cells and display. The SiOx shell layer provides a natural antireflection from air to the Si core absorption layer. In this work, we have demonstrated the random core-shell silicon nanowires with both broadband (from 400nm to 900nm) and wide angle (from normal incidence to 60°) antireflection characteristics within AM1.5 solar spectrum. The graded index structure from the randomly oriented core-shell (Air/SiOx/Si) nanowires may provide a potential avenue to realize a broadband and wide angle antireflection layer.
The major factor limiting the efficiencies of thin film Si solar cells is their weak absorption of red and near-infrared photons due to short optical path length and indirect bandgap. Powerful light trapping is essential to confine light inside the cell for sufficient absorption. Here we report the first experimental application of a new light trapping scheme, the textured photonic crystal (TPC) backside reflector, to monocrystalline thin film Si solar cells. TPC combines a onedimensional photonic crystal, i.e., a distributed Bragg reflector (DBR), with a reflection grating. The near unity reflectivity of DBR in a wide omnidirectional bandgap and the large angle diffraction by the grating ensures a strong enhancement in the absorption of red and near-infrared photons, leading to significant improvements in cell efficiencies. Measured short circuit current density Jsc was increased by 19% for 5 μm thick cells, and 11% for 20 μm thick cells, compared to theoretical predictions of 28% and 14%, respectively.
A new backside reflector, textured photonic crystal, is introduced into Si thin film solar cells. Scattering matrix method is used to systematically optimize all the parameters of the two components of the backside reflector, grating and distributed Bragg reflector, to achieve the highest power conversion efficiency for a given solar cell thickness. Experimentally, Si-on-insulator solar cells are being fabricated to verify the tremendous efficiency enhancement and optimal design. It is found that while the optimal period and etch depth of the grating, the Bragg wavelength of the distributed Bragg reflector, as well as the antireflection coating thickness all decrease as the cell becomes thinner, the optimum duty cycle of the grating remains almost constant at 0.5. For a 2 μm thick cell, the relative efficiency enhancement can be as high as 52% using the optimized design.
We have successfully developed a new light-trapping scheme for solar cells that can enhance the optical path length by more than 104 times using a textured photonic crystal structure as a backside reflector. Top-contacted crystalline Si solar cells integrated with the new back reflector were designed, fabricated and characterized. Both external quantum efficiency and power conversion efficiency of the cells have shown significant improvement due to the path length enhancement furnished by the new back reflector despite of the 675 um thick wafers and relatively short minority carrier diffusion length.
A novel light trapping scheme is developed to enhance the optical path length in solar cells by using a photonic structure as the backside reflector. This structure combines a reflection grating on the substrate with an over-deposited distributed Bragg reflector (DBR). With this structure, the optical path length can be enhanced by more than 104 times with very little reflection loss. In turn, solar cell efficiency is predicted to be enhanced enormously.
Aperiodic one dimensional Si/SiO2 Thue-Morse (T-M) multilayer structures have been fabricated, for the first time, in order to investigate both the band-gap behavior, with respect to the system size (band-gap scaling), and the omnidirectional reflectance of the fundamental optical band-gap. Variable angle reflectance data have experimentally demonstrated a large reflectance band-gap in the optical spectrum of a T-M quasicrystal, in agreement with transfer matrix simulations. We have explained the physical origin of the T-M omnidirectional band-gap as a result of periodic spatial correlations in the self-similar T-M structure, as revealed by Fourier Transform and Wavelet analysis. The unprecedented degree of structural flexibility showed by T-M systems can provide an attractive alternative to photonic crystals for the fabrication of photonic devices.
Between July 2000 and June 2001 we undertook a survey of François' langur Trachypithecus francoisi and its habitat in the Fusui Nature Reserve in south-west Guangxi, China, where 86 individual langurs were recorded in 1995. In our first survey period we located 45 individuals in 10 groups, but c. 12 months later, despite expending more effort, we were only able to locate three of the 10 groups, totalling 23 individuals. In all, in three separate surveys, we recorded densities that were 26–52% of the 1995 figures. Within the Reserve almost all of the valley bottoms and most flat areas in the hills have been cultivated and there is steady encroachment into the hills and forests. The majority of local families depend on the forest for firewood. It appears that habitat loss and illegal hunting are responsible for the decline of François' langur. We recommend that alternative income generating activities and energy sources should be explored to reduce human pressure on these langurs and their habitat. More funding should also be made available to the Reserve to enable staff to adequately tackle issues of hunting and habitat destruction.
Light propagation in a low index core (e.g. SiO2) is realized by a Photonic Band Gap (PBG) cladding waveguide structure with large dielectric index contrast layers (Si/Si3N4). The waveguide is fabricated with a CMOS compatible process. The measured loss for the asymmetric PBG cladding waveguide is about 0.5dB/cm for both polarizations at a wavelength of 1550nm. Potential applications include optical amplification when the SiO2 core is doped with optical active materials (e.g. Er).