241 research outputs found
Quantum efficiency of single-photon sources in the cavity-QED strong-coupling regime
We calculate the integrated-pulse quantum efficiency of single-photon sources
in the cavity quantum electrodynamics (QED) strong-coupling regime. An
analytical expression for the quantum efficiency is obtained in the
Weisskopf-Wigner approximation. Optimal conditions for a high quantum
efficiency and a temporally localized photon emission rate are examined. We
show the condition under which the earlier result of Law and Kimble [J. Mod.
Opt. 44, 2067 (1997)] can be used as the first approximation to our result.Comment: 8 pages, 3 figures, final version, tex file uploade
Evaluating Online Social Presence: An Overview of Social Presence Assessment
As an important variable in online learning environment, the construct of social presence has been widely studied by researchers in order to investigate students’ online communication behavior and their related performance. This study will provide an overview of the assessment of social presence throughout its historical development. In this review, both primary subjective and objectives measures of social presence will be introduced, followed by criticisms towards current social presence measures, and offer recommendations for future development of social presence measurement tools
Adopting Cell Phones in EFL Teaching and Learning
Though Mobile Learning (ML) has a brief history of no more than four decades, the medium is developing rapidly with the upgrading of different mobile devices. Among all the devices, cell phones have great potential in language teaching and learning. This article explores the different devices especially cell phone use in ML. The paper also reviews teaching and learning of English as a Foreign Language (EFL) in China and discusses potential applications of cell phones in Chinese EFL teaching and learning
Glandless Cottonseed Protein for Environmentally Friendly Bioplastics
Environmentally friendly bioplastics have attracted renewed attention over the last few decades due to the ever‐growing awareness of the environmental impact of petroleum‐based polymers and the rising costs of raw materials. Cottonseed protein (CP) extracted from cottonseed meal has abundant amino acid components and nutrition value, but are not carefully considered in non‐feed industries. For the purpose of being explored, glandless cottonseed flour is utilized in this work, as a raw material, to prepare cottonseed protein bioplastics (CPBs) as environmentally friendly products. The optimum synthesis conditions of CPBs were firstly investigated, followed by the analysis of protein modification and cross‐linking mechanism, with a close view on changes of their micro‐ or chemical structures. Detailed morphologies, element composition and biodegradabilities of CPBs were characterized via scanning electron microscopy, energy dispersive spectroscopy (EDS) and soil‐burial test, respectively, pointing out its structural heterogeneity as well as nature of biodegradability. Characterizations of the thermal stability and thermomechanical relaxation of thermal‐treated CPBs and its interaction with molecule revealed the presence of different thermal relaxation behaviours and different water states. Concluding remarks shortly summarize the importance of the work and point out possible solutions to addressing future potential challenges
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An automated method for comparing motion artifacts in cine four-dimensional computed tomography images.
The aim of this study is to develop an automated method to objectively compare motion artifacts in two four-dimensional computed tomography (4D CT) image sets, and identify the one that would appear to human observers with fewer or smaller artifacts. Our proposed method is based on the difference of the normalized correlation coefficients between edge slices at couch transitions, which we hypothesize may be a suitable metric to identify motion artifacts. We evaluated our method using ten pairs of 4D CT image sets that showed subtle differences in artifacts between images in a pair, which were identifiable by human observers. One set of 4D CT images was sorted using breathing traces in which our clinically implemented 4D CT sorting software miscalculated the respiratory phase, which expectedly led to artifacts in the images. The other set of images consisted of the same images; however, these were sorted using the same breathing traces but with corrected phases. Next we calculated the normalized correlation coefficients between edge slices at all couch transitions for all respiratory phases in both image sets to evaluate for motion artifacts. For nine image set pairs, our method identified the 4D CT sets sorted using the breathing traces with the corrected respiratory phase to result in images with fewer or smaller artifacts, whereas for one image pair, no difference was noted. Two observers independently assessed the accuracy of our method. Both observers identified 9 image sets that were sorted using the breathing traces with corrected respiratory phase as having fewer or smaller artifacts. In summary, using the 4D CT data of ten pairs of 4D CT image sets, we have demonstrated proof of principle that our method is able to replicate the results of two human observers in identifying the image set with fewer or smaller artifacts
Molecular Characterization and Expression of α-Globin and β-Globin Genes in the Euryhaline Flounder (Platichthys flesus)
In order to understand the possible role of globin genes in fish salinity adaptation, we report the molecular characterization and expression of all four subunits of haemoglobin, and their response to salinity challenge in flounder. The entire open reading frames of α1-globin and α2-globin genes were 432 and 435 bp long, respectively, whereas the β1-globin and β2-globin genes were both 447 bp. Although the head kidney (pronephros) is the predicted major site of haematopoiesis, real-time PCR revealed that expression of α-globin and β-globin in kidney (mesonephros) was 1.5 times higher than in head kidney. Notably, the α1-globin and β1-globin mRNA expression was higher than α2-globin and β2-globin in kidney. Expression levels of all four globin subunits were higher in freshwater- (FW-) than in seawater- (SW-)adapted fish kidney. If globins do play a role in salinity adaptation, this is likely to be more important in combating the hemodilution faced by fish in FW than the dehydration and salt loading which occur in SW
Keratin/Polyvinyl Alcohol Blend Films Cross-Linked by Dialdehyde Starch and Their Potential Application for Drug Release
Feather keratin (FK) extracted from feathers represents a valuable source of biodegradable and biocompatible polymer. The aim of this study was the development and characterization of blended films based on FK and polyvinyl alcohol (PVA) cross-linked by dialdehyde starch (DAS) for a potential drug release application. The compatibility of FK/PVA was improved when cross-linked by DAS: the relative crystallinity of the PVA/FK film slightly decreased, and the enthalpy value for the melting peak decreased by about 50% for the cross-linked films. The total soluble mass of all blend films in water was below 35% at 37 °C, indicating a good stability of the films in water. The results of the Rhodamine B dye (as a model drug) release tests showed that the release rates decreased with increasing DAS content. DAS-induced cross-linking improves several important properties of the FK/PVA films, such as the compactness, the compatibility, and the stability in water. These improvements offer the potential to expand the application of FK films in the biomaterial field
Grassland greening and water resource availability may coexist in a warming climate in Northern China and the Tibetan Plateau
Greening of Northern China and the Tibetan Plateau (NCTP) has been observed by increases in the remotely sensed leaf area index (LAI), driven primarily by CO2 fertilization effects, anthropogenic warming, and the implementation of ecological restoration programs. Continued growth of LAI throughout the 21st century is also projected by the Coupled Model Intercomparison Project Phase 6 (CMIP6) scenarios. However, the question of whether local water resources can sustain ongoing grassland greening has not been adequately investigated. Here we assessed the sustainability of water resources under grassland greening across NCTP under various climate scenarios using water yield (WY, defined as precipitation minus actual evapotranspiration) as the key metric. Unexpectedly, we observe the coexistence of increases in LAI and WY in most of NCTP. In a warming climate with increasing precipitation and CO2, we find that grasses maintain high water use efficiency to sustain their growth, contributing to continued local water resource availability. Thus, livestock production may also continue to increase under the simultaneous growth of LAI and WY in the future
A hemispherical, high-solid-angle optical micro-cavity for cavity-QED studies
We report a novel hemispherical micro-cavity that is comprised of a planar
integrated semiconductor distributed Bragg reflector (DBR) mirror, and an
external, concave micro-mirror having a radius of curvature .
The integrated DBR mirror containing quantum dots (QD), is designed to locate
the QDs at an antinode of the field in order to maximize the interaction
between the QD and the cavity. The concave micro-mirror, with high-reflectivity
over a large solid-angle, creates a diffraction-limited (sub-micron) mode-waist
at the planar mirror, leading to a large coupling constant between cavity mode
and QD. The half-monolithic design gives more spatial and spectral tuning
abilities, relatively to fully monolithic structures. This unique micro-cavity
design will potentially enable us to both reach the cavity quantum
electrodynamics (QED) strong coupling regime and realize the deterministic
generation of single photons on demand.Comment: 15 pages, 17 figures, final versio
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