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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.
Background: Global variation in the incidence of multiple sclerosis (MS) is generally ascribed to differences in genetic and environmental risk factors. Here we investigate temporal trends in the incidence of MS and related disorders in British Columbia, Canada, from 1986 to 2010, focusing particularly on the Asian ethnic subpopulation.
Methods: A longitudinal database was screened to identify newly diagnosed cases of MS and related disorders, including neuromyelitis optica and clinically isolated syndromes. Age-standardized, sex-specific mean annual incidence was calculated for the Asian and non-Asian population of British Columbia for 5-year intervals from 1986 to 2010. Temporal changes and cohort differences in incidence rates and demographic characteristics were evaluated. Results: During this period, the incidence of MS and related disorders in the non-Asian population remained relatively unchanged, from 10.41 (95% confidence interval [CI]: 9.87-10.97) to 9.91 (95% CI: 9.46-10.39) per 100,000 (p=0.167). In contrast, incidence in the Asian population doubled during the same period. This increase was driven by a precipitous rise in the incidence of MS in females from 0.71 (95% CI: 0.01-1.50) to 2.08 (95% CI: 1.43-2.91) per 100,000 (p=0.004), including both Canadian-born and immigrant Asians. The incidence of neuromyelitis optica did not change significantly during this period. Conclusions: The incidence of MS may be increasing among females in the Asian ethnic population of British Columbia.
Molecular cloning, tissue distribution and ontogenetic regulation of sodium/proton exchanger isoform 2 (NHE-2) mRNA expression were evaluated in the pig small intestine during postnatal development. The 2872-bp porcine full cDNA sequence of the NHE-2 (EF672046) cloned in this study showed 80% and 70% homology with known human and mouse gene sequence, respectively. Hydrophobic prediction suggests 13 putative membrane-spanning domains within porcine NHE-2. The porcine NHE-2 mRNA was detected in the brain, liver, kidney, heart, lung, small intestine and muscle. The small intestine had the highest NHE-2 mRNA abundance and the brain, lung and liver had the lowest NHE-2 mRNA abundance (P < 0.05). Along the longitudinal axis, the duodenum had the highest NHE-2 mRNA abundance and the ileum and colon had the lowest NHE-2 mRNA abundance (P < 0.05). The NHE-2 mRNA level was increased from day 1 to day 26 in the duodenum (P < 0.05) and dropped dramatically on day 30 (P < 0.05). There is no difference between day 1 and day 7 (P > 0.05). After day 30, the NHE-2 mRNA level remained the same except on day 90 (P > 0.05). The mRNA expression of NHE-2 was not only differentially regulated by age but also differentially distributed along the small intestine of piglets at early stages and growing stages of life, which may contribute to changes in NHE activity.
Because of its significant potential in controlling key steps of apatite mineralization, recombinant amelogenin has been applied in different in vitro systems for the synthesis of uniquely ordered composite material similar to enamel. Here we summarize the results of a series of experiments, in which mineral deposition took place on the exposed surface of enamel from extracted human third molars soaked in calcium phosphate solution, in the presence of amelogenin and fluoride. Analysis of crystal size and morphology revealed that in the presence of both amelogenin (50-100 μg/mL) and fluoride (1 ppm), bundles of oriented rod- like fluoridated apatite crystals were formed creating a dense coating on the enamel substrate. Such organized bundles were not formed at low concentrations of rP172 (< 30 μg/mL). Preparation of such ordered nanocomposites provides a promising approach for development of new generation of dental restorative materials with improved esthetic and mechanical properties.
Nanosized Co-doped ZnO samples were synthesized using an ultrasonic spray assisted chemical vapour deposition method. Microstructural and magnetic properties of these samples were studied. The room-temperature ferromagnetism was observed in the Co-doped ZnO. Also, x-ray analysis revealed a wurtzite ZnO structure with a small change of the lattice constants due to the doping of Co in ZnO. Raman spectroscopy of the Co-doped ZnO films indicated direct substitution of Co. Scanning electron microscopy showed nanostructured Co-doped ZnO with a ring or cup shape. Transmission electron microscopy analysis revealed nano grains within the rings of an average diameter of around 10 nm. Both energy dispersive spectroscopy and energy-filtered transmission electron microscopy indicated a uniform distribution of Co.
ZnO, which exhibits a direct bandgap of 3.37 eV at room temperature with a large exciton binding energy of 60 meV,is of considerable technological importance because of its potential use in short-wavelength devices, such as ultraviolet (UV) light-emitting diodes and laser diodes. The fabrication and application of 1-D ZnO nanostructures has attracted considerable interest in recent years. In this work, we produced single crystal nanowires of zinc oxide using a novel self-seeded growth using ultrasonic spray assisted chemical vapour deposition, in which a nanocrystalline seed layer was first deposited onto a glass substrate and the nanowires subsequently grown using a different precursor concentration and substrate temperature. The diameter of the nanowires is in the range of 20-80 nm and the length of the wires is as long as 10 μm. The single crystal nature of the nanowires was revealed by high resolution transmission electron microscopy. The formation of liquid droplets due to the reducing atmosphere and the higher temperature during the nanowire growth was found to be the key step of the ZnO nanowire formation.
As traditional poly-silicon gated MOSFET devices scale, the additional series capacitance due to poly-silicon depletion becomes an increasingly large fraction of the total gate capacitance, excessive boron penetration causes threshold voltage shifts, and the gate resistance is elevated. To solve these problems and continue aggressive device scaling we are studying metal electrodes with suitable work-functions and sufficient physical and electrical stability. Our studies of metal gates on HfO2 indicate that excessive inter-diffusion, inadequate phase stability, and interfacial reactions are mechanisms of failure at source drain activation temperatures that must be considered during the electrode selection process. Understanding the physical properties of the metal gate – HfO2 interface is critical to understanding the electrical behavior of MOS devices. Of particular interest is Fermi level pinning, a phenomenon that occurs at metal – dielectric interfaces which causes undesirable shifts in the effective metal work function. The magnitude of Fermi level pinning on HfO2 electrodes is studied with Pt and LaB6 electrodes. In addition, the intrinsic and extrinsic contributions to Fermi level pinning of platinum electrodes on HfO2 gate dielectrics are investigated by examining the impact of oxygen and forming gas anneals on the work function of platinum-HfO2-silicon capacitors. The presence of interfacial oxygen vacancies or Pt-Hf bonds is believed to be responsible for a degree of pinning that is stronger than predicted from the MIGS model alone. Interface chemistry and defects influence the effective metal work function.
In this paper, we report a simple method for preparing p-type ZnO thin films by thermal oxidization of Zn3N2 thin films. The Zn3N2 films were grown on fused silica substrates by using plasma-enhanced chemical vapor deposition from a Zn(C2H5)2 and NH3 gas mixture. The Zn3N2 film with a cubic antibixbyite structure transformed to ZnO:N with a hexagonal structure as the annealing temperature reached 500 °C. When the annealing temperature reached 700 °C, a high-quality p-type ZnO film with a carrier density of 4.16 × 1017 cm−3 was obtained, for which the film showed a strong near-band-edge emission at 3.30 eV without deep-level emission, and the full width at half-maximum of the photoluminescence spectrum was 120 meV at room temperature. The origin of the ultraviolet band was the overlap of free exciton and the bound exciton. The N concentration was as high as 1021 cm−3, which could be controlled by adjusting the parameters of the annealing processes.
Several new methods have been developed for the synthesis of POSS monomers from fully condensed [RSiO3/2]n and [ROSiO3/2]n (n = 6 or 8) frameworks. These methods, which all rely on highly selective base-catalyzed reactions of Si/O frameworks, provide unprecedented access to new POSS monomers and the means for manufacturing useful POSS monomers on a large scale from readily available silane monomers.
Conventional wisdom and earlier research have concluded that cattle feeding profitability is more determined by feeder and fed cattle prices than by animal performance. This study examined cross-sectional and time-series data from over 1600 pens of cattle in more than 220 feedlots in the upper Midwest where weather and lot conditions are thought to influence feedlot profitability. In addition to input and output prices and animal performance, other factors found to significantly impact cattle feeding profitability were sex, placement weight, facility design, and to a lesser extent placement season.
Two deep levels, located at Ev+0.26eV and Ec-0.44eV, in Al-implanted n-type samples and one at Ev+0.48eV in p-type samples have been observed by the deep level transient spectroscopy. The level of is identified as the shallower aluminum-acceptor. The 1.7 MeV electron-irradiation, used as a probe to distinguish the implantation induced deep-levels, induces at least six electron traps in the n-SiC and one hole-trap in the p-type material. The peak positions of these deep-levels in DLTS spectra are quite different from those induced by Al-implantation. This result suggests that various damages are formed after heavy ion (Al) and light particle (e) irradiation.
The thermal stability of thin CoSi2 films formed from four layered structures: Co/Si, TiN/Co/Si, Co/Ti/Si and TiN/Co/Ti/Si has been studied using four-point-probe (FPP), TEM and RBS/channeling. It is found that thermal instability can be influenced by the polycrystalline structure in CoSi2. Growing epitaxial CoSi2 film on Si (100) using TiN capping and Ti interfacial layers can improve the thermal stability of thin CoSi2 film.
We report a structural analysis of GaN layers with thicknesses ranging from 10 μm to 250 μm which have been grown on sapphire substrates by halide vapor phase epitaxy (HVPE). The effect of growth rate during HVPE growth has also been examined. The growth was performed using GaCl and ammonia as reactants; growth rates in excess of 90 μm/hr have been achieved. The structural characteristics of these layers have been performed wit'i high resolution x-ray diffractometry. Longitudinal scans parallel to the GaN  direction, transverse scans perpendicular to the , and reciprocal space maps of the total diffracted intensity have been obtained from a variety of GaN layers. The transverse scans typically show broad rocking curves with peak breadths of several hundreds of arcseconds. In contrast, the longitudinal scans (or “θ/2θ scans”) which are sensitive only to strains in the GaN layers (and not their mosaic distributions) showed peak widths that were at least an order of magnitude smaller and in some cases were as narrow as 16 arcseconds. These results suggest that the defect structure of the GaN layers grown by HVPE is dominated by a dislocation-induced mosaic distribution, with the effects of strain in these materials being negligible in comparison.
We have investigated the nucleation and growth of gallium nitride (GaN) films on silicon and sapphire substrates using halide vapor phase epitaxy (HVPE). GaN growth was carried out on bare Si and sapphire surfaces, as well as on MOVPE-grown GaN buffer layers. HVPE growth on MOVPE GaN/AlN buffer layers results in lower defect densities as determined by x-ray than growth directly on sapphire. HVPE GaN films grown directly on sapphire exhibit strong near-edge photoluminescence, a pronounced lack of deep level-based luminescence, and x-ray FWHM values of 16 arcsec by an x-ray θ-2θ scan. The crystallinity of GaN films on sapphire is dominated by the presence of rotational misorientation domains, as measured by xray ω-scan diffractometry, which tend to decrease with increasing thickness or with the use of a homoepitaxial MOVPE buffer layer. The effect of increasing film thickness on the defect density of the epilayer was studied. In contrast, the HVPE growth of nitride films directly on silicon is complicated by mechanisms involving the formation of silicon nitrides and oxides at the initial growth front.
The ion-beam-sputtered polycrystalline SiGe film and its doping properties have been studied. Boron and phosphorus have been doped into the sputtered poly-SiGe film by ion implantation and diffusion. To activate the implanted impurities, both rapid thermal annealing and fiirnace annealing have been used. The electrical measurements show that boron and plhosphorus can be doped into sputtered SiGe films and effectively activated by both ion implantation with post-annealing and diffiision. Hall mobilities as high as 31 cm2/V-s and 20 cm2/V.s have been obtained in B-difflhsed and P-diffused SiGe films, respectively. The x-ray diffraction spectra of the sputtered Sifie filhn show its typical polycrystalline structure with (111), (220) and (311) as the preferential orientations.
A numerical model of an experimental gallium nitride horizontal vapor phase epitaxy reactor is presented. The model predicts the flow, concentration profiles, and growth rates. The effects of flowrate variation and geometry on the growth rate, growth uniformity and crystal quality were investigated. Numerical model predictions are compared to experimentally observed values. Parasitic gas phase reactions between group III and group V sources and deposition of material on the wall are shown to lead to reduced overall growth rates and inferior crystal quality. A low ammonia concentration is correlated to deposition of polycrystalline films. An optimum HVPE growth process requires selection of reactor geometry and operating conditions to minimize parasitic reactions and wall deposition while providing a uniform reactant distribution across the substrate.
An evaluation of the use of intermediate layers for promoting adhesion between diamond and Fe and Ni base alloys is presented. The lack of adhesion between diamond and such alloys has prevented its use as a protective coating in applications at intermediate temperatures. In this study we use a combination of plasma assisted deposition techniques together with controlled bias of the substrate in order to deposit intermediate layers, and simultaneously achieve a thorough intermixing of the elements at the interface, in order to increase the adhesion between the layers. We have compared the performance of different carbide forming metals, as well as other materials. Properties considered in the selection of the appropriate intermediate layers are: chemical affinity with carbon, thermal expansion coefficient, mechanical properties, and adhesion to diamond and to the base metal as well. In the case of multiple layers, adhesion strength was measured after every new layer was deposited, in order to identify any weak links of the composite structure. Transmission electron microscopy was used to determine the microstructure and phases. An analysis is provided of the resulting performance on the basis of the microstructure.
The energy histogram method, introduced by Ferrenberg and Swendsen [Phys. Rev. Lett., 61, 2635, (1988) and 63, 1195, (1989)], was applied for the first time to the constant temperature molecular dynamics (MD) simulation of a two-dimensional (2D) system with incommensurate structures. We performed MD simulations for the stage-2 graphite intercalation compounds (GIC's) with Rb or K being the intercalants (Rb-GIC's and K- GIC's). The temperature dependence of the specific heat, Cv, is calculated for various sizes up to 864 atoms. The melting temperature was found to be 158 K for Rb-GIC's and 119 K for K-GIC's, respectively, which are in agreement with the experimental observations.