2,704 research outputs found
Spontaneous two photon emission from a single quantum dot
Spontaneous two photon emission from a solid-state single quantum emitter is
observed. We investigated photoluminescence from the neutral biexciton in a
single semiconductor quantum dot coupled with a high Q photonic crystal
nanocavity. When the cavity is resonant to the half energy of the biexciton,
the strong vacuum field in the cavity inspires the biexciton to simultaneously
emit two photons into the mode, resulting in clear emission enhancement of the
mode. Meanwhile, suppression was observed of other single photon emission from
the biexciton, as the two photon emission process becomes faster than the
others at the resonance.Comment: 13 pages, 4 figure
G-language genome analysis environment with REST and SOAP web service interfaces
G-language genome analysis environment (G-language GAE) contains more than 100 programs that focus on the analysis of bacterial genomes, including programs for the identification of binding sites by means of information theory, analysis of nucleotide composition bias and the distribution of particular oligonucleotides, calculation of codon bias and prediction of expression levels, and visualization of genomic information. We have provided a collection of web services for these programs by utilizing REST and SOAP technologies. The REST interface, available at http://rest.g-language.org/, provides access to all 145 functions of the G-language GAE. These functions can be accessed from other online resources. All analysis functions are represented by unique universal resource identifiers. Users can access the functions directly via the corresponding universe resource locators (URLs), and biological web sites can readily embed the functions by simply linking to these URLs. The SOAP services, available at http://www.g-language.org/wiki/soap/, provide language-independent programmatic access to 77 analysis programs. The SOAP service Web Services Definition Language file can be readily loaded into graphical clients such as the Taverna workbench to integrate the programs with other services and workflows
Optical constraints of kerogen from 0.15 to 40 microns: Comparison with meteoritic organics
Kerogens are dark, complex organic materials produced on the Earth primarily by geologic processing of biologic materials, but kerogens have chemical and spectral similarities to some classes of highly processed extraterrestrial organic materials. Kerogen-like solids were proposed as constitutents of the very dark reddish surfaces of some asteroids and are also spectrally similar to some carbonaceous organic residues and the Iapetus dark material. Kerogen can thus serve as a useful laboratory analog to very dark, spectrally red extraterrestrial materials; its optical constants can be used to investigate the effects of particle size, void space and mixing of bright and dark components in models of scattering by dark asteroidal, cometary, and satellite surfaces. Measurements of the optical constants of both Type 2 kerogen and of macromolecular organic residue from the Murchison carbonaceous chondrite via transmission and reflection measurements on thin films are reported. The real part of the refractive index, n, is determined by variable incidence-angle reflectance to be 1.60 + or - 0.05 from 0.4 to 2.0 micrometers wavelength. Work extending the measurement of n to longer wavelengths is in progress. The imaginary part of the refractive index, k, shows substantial structure from 0.15 to 40 micrometers. The values are accurate to + or - 20 percent in the UV and IR regions and to + or - 30 percent in the visible. The k values of organic residues were also measured from the Murchison meteorite. Comparison of the kerogen and Murchison data reveals that between 0.15 and 40 microns, Murchison has a similar structure but no bands as sharp as in kerogen, and that the k values for Murchison are significantly higher than those of kerogen
AGN-driven galactic outflows: comparing models to observations
The actual mechanism(s) powering galactic outflows in active galactic nuclei
(AGN) is still a matter of debate. At least two physical models have been
considered in the literature: wind shocks and radiation pressure on dust. Here
we provide a first quantitative comparison of the AGN radiative feedback
scenario with observations of galactic outflows. We directly compare our
radiation pressure-driven shell models with the observational data from the
most recent compilation of molecular outflows on galactic scales. We show that
the observed dynamics and energetics of galactic outflows can be reproduced by
AGN radiative feedback, with the inclusion of radiation trapping and/or
luminosity evolution. The predicted scalings of the outflow energetics with AGN
luminosity can also quantitatively account for the observational scaling
relations. Furthermore, sources with both ultra-fast and molecular outflow
detections are found to be located in the `forbidden' region of the
plane. Overall, an encouraging agreement is obtained
over a wide range of AGN and host galaxy parameters. We discuss our results in
the context of recent observational findings and numerical simulations. In
conclusion, AGN radiative feedback is a promising mechanism for driving
galactic outflows that should be considered, alongside wind feedback, in the
interpretation of future observational data.Comment: accepted for publication in MNRA
Enhanced photoluminescence emission from two-dimensional silicon photonic crystal nanocavities
We present a temperature dependent photoluminescence study of silicon optical
nanocavities formed by introducing point defects into two-dimensional photonic
crystals. In addition to the prominent TO phonon assisted transition from
crystalline silicon at ~1.10 eV we observe a broad defect band luminescence
from ~1.05-1.09 eV. Spatially resolved spectroscopy demonstrates that this
defect band is present only in the region where air-holes have been etched
during the fabrication process. Detectable emission from the cavity mode
persists up to room-temperature, in strong contrast the background emission
vanishes for T > 150 K. An Ahrrenius type analysis of the temperature
dependence of the luminescence signal recorded either in-resonance with the
cavity mode, or weakly detuned, suggests that the higher temperature stability
may arise from an enhanced internal quantum efficiency due to the
Purcell-effect
Global Pharmacy: A Comparative Exploration and Analysis of Initial Professional Education
The quality of initial professional pharmacy education (IPPE) is receiving growing attention in the development of modern health policy. This is due to the gradually extended role of pharmacists, a global shortage of pharmacy workforce and their skill-mix imbalances, all of which require improvements to respond to the expanding and ever-changing population health needs. To achieve enhanced and equitable quality worldwide, evidence that can be used as a global basis for identifying gaps and challenges to assist strengthening IPPE is demanded. The purpose of this research was to generate evidence to construct the first global map of the attributes of quality IPPE for assisting the improvement of IPPE across nations. The research questions what are the differences and commonalities in the current IPPE practices worldwide, and if there are globally shared attributes for high quality IPPE, which can support further development of professional roles. A mixed-methods approach was implemented to investigate personal and institutional factors in a global context. To seek students’ factors in the quality IPPE, a global online survey on students’ learning processes and experiences was conducted, resulting in 4,105 student responses from 78 countries. To investigate teaching and institutional attributes of IPPE, an attached email global survey on IPPE institutions and programmes and a curriculum content analysis were conducted, which compared country-level institutional information from 110 countries and territories as well as contrasting in-depth curricula content data from 16 countries. The combined findings provide measures of current IPPE practices across nations. This includes differences in approaches to learning between regions and nations; pharmacy model to foster the adoption of deep approach to learning; global variation regarding capacity, provision, and regulations; and variation in curricula content when contrasting science and practice components. The thesis provides evidence for a policy review of IPPE to assist with enhancing global quality
Opportunities to demonstrate expertise and job satisfaction of community pharmacists in Japan and England
Background: In response to anticipated increased health needs as a consequence of aging populations, and associated rising co-morbidity and medicines use, in both Japan and the UK potential extended roles for community pharmacy are part of health policy agendas. It is widely perceived that community pharmacists do not fully utilize their expertise, which may limit their contribution to health care in their communities and also impact negatively on their own job satisfaction. Purpose: The aim of this qualitative study was to identify operations that are perceived as opportunities to demonstrate expertise (ODE) and/or sources of job satisfaction by pharmacists in Japan and England, and explore associated system and contextual factors. Methods: Data were gathered with purposively selected pharmacists in Japan and England. An initial questionnaire was forwarded which guided subsequent face-to-face semi-structured interviews. These were audio-recoded to enable qualitative analytical procedures. Results: There were 18 participants in England and 13 in Japan. There was a notable association between ODE and job satisfaction. However, ODE was not a sufficient condition for job satisfaction. Conclusion: In order for pharmacists to be satisfied with their jobs, not only ODE but also additional contextual factors, i.e. recognition of professionalism, autonomy and positive collaboration were also needed. The findings can inform initiatives in the development of pharmacy services that would be positive for pharmacists whilst potentially contributing to wider public health objectives
Optical constants of solid methane
Methane is the most abundant simple organic molecule in the outer solar system bodies. In addition to being a gaseous constituent of the atmospheres of the Jovian planets and Titan, it is present in the solid form as a constituent of icy surfaces such as those of Triton and Pluto, and as cloud condensate in the atmospheres of Titan, Uranus, and Neptune. It is expected in the liquid form as a constituent of the ocean of Titan. Cometary ices also contain solid methane. The optical constants for both solid and liquid phases of CH4 for a wide temperature range are needed for radiative transfer calculations, for studies of reflection from surfaces, and for modeling of emission in the far infrared and microwave regions. The astronomically important visual to near infrared measurements of solid methane optical constants are conspicuously absent from the literature. Preliminary results are presented on the optical constants of solid methane for the 0.4 to 2.6 micrometer region. Deposition onto a substrate at 10 K produces glassy (semi-amorphous) material. Annealing this material at approximately 33 K for approximately 1 hour results in a crystalline material as seen by sharper, more structured bands and negligible background extinction due to scattering. The constant k is reported for both the amorphous and the crystalline (annealed) states. Typical values (at absorption maxima) are in the .001 to .0001 range. Below lambda = 1.1 micrometers the bands are too weak to be detected by transmission through the films less than or equal to 215 micrometers in thickness, employed in the studies to date. Using previously measured values of the real part of the refractive index, n, of liquid methane at 110 K, n is computed for solid methane using the Lorentz-Lorenz relationship. Work is in progress to extend the measurements of optical constants n and k for liquid and solid to both shorter and longer wavelengths, eventually providing a complete optical constants database for condensed CH4
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