The fundamental luminescence and chromaticity properties of a class of red-emitting phosphors LiEu͑WO 4 ͒ 2−x ͑MoO 4 ͒ x under near-UV excitation have been investigated. The photoluminescence ͑PL͒ and photoluminescence excitation ͑PLE͒ spectra reveal that the absorption is mainly attributed to O → Mo͑W͒ charge transfer at 300 nm and the Eu 3+ transitions in near-UV and visible regions, and red emissions are assigned to intraconfigurational 4f-4f transitions of Eu 3+ . Both PL and PLE intensity were found to increase with increasing doped Mo content. The intensity of the 5 D 0 → 7 F 2 emission of Eu 3+ activated at 394 nm was found to reach a maximum when the relative ratio of Mo/W was 2:0. The CIE chromaticity coordinates were found to be ͑0.66, 0.33͒ for LiEu͑MoO 4 ͒ 2 and it reached the same level as the commodity phosphor Y 2 O 2 S:Eu 3+ . A white-light-emitting diode fabricated using the composition-optimized LiEu͑MoO 4 ͒ 2 and the matching green-and blue-emitting phosphors shows that the quality of red color reproduction based on LiEu͑MoO 4 ͒ 2 was found to be much higher and improved than that using La 2 O 2 S:Eu 3+ .
We have investigated the luminescence of a series of M 5 Eu͑WO 4 ͒ 4−x ͑MoO 4 ͒ x ͑M = Li, Na, K͒ phosphors and discovered that Na 5 Eu͑WO 4 ͒ 4−x ͑MoO 4 ͒ x ͑0 Յ x Յ 4.0͒ exhibit the most intense red emission among the three investigated. Powder X-ray diffraction investigations show that a complete solid solution can be formed in the indicated composition range. The effect of chemical compositions on the luminescence properties of Na 5 Eu͑WO 4 ͒ 4−x ͑MoO 4 ͒ x has been investigated and discussed. The Commission International de l'Eclairage chromaticity coordinates were found to be ͑0.66,0.33͒ for Na 5 Eu͑WO 4 ͒ 4−x ͑MoO 4 ͒ x , which reaches the same level as that of the Y 2 O 2 S:Eu 3+ commodity. The color-rendering index ͑Ra͒ of a typical white-light-light emitting diode ͑WL-LED͒ based on Na 5 Eu͑WO 4 ͒ 2 ͑MoO 4 ͒ 2 was found to be 82.3, higher than that ͑i.e., Ra ϳ 70.8͒ obtained for the WL-LED fabricated using the commodity of La 2 O 2 S:Eu 3+ when the WL-LEDs were operated at a forward-bias current ͑I f ͒ of 20 mA at room temperature. Na 5 Eu͑WO 4 ͒ 4−x ͑MoO 4 ͒ x is therefore suggested to be a potential red-emitting phosphor for WL-LED. ExperimentalThe phosphors of the compositions M 5 Eu͑WO 4 ͒ 4−x ͑MoO 4 ͒ x were synthesized by high-temperature solid-state reactions. The starting materials used were M 2 MoO 4 ͑99.9%; MϭLi, Na, K͒ ͑Strem Chemicals, Newburyport, MA, USA͒, M 2 WO 4 ͑99.9%; MϭLi, Na, K͒, MoO 3 ͑99.95%͒, WO 3 ͑99.9%͒, ͑all from Cerac Chemicals, Milwaukee, Wisconsin, USA͒ and Eu 2 O 3 ͑99.99%, Aldrich Chemicals, Milwaukee, Wisconsin, USA͒. Stoichiometric amounts of reactants were ground by ballmilling and then heated at 600°C for 6 h. The XRD profiles were recorded by using a Bruker D8 Advanced diffractometer equipped with Cu K␣ radiation ͑ J71 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 132.174.254.155 Downloaded on 2015-04-05 to IP J76 Journal of The Electrochemical Society, 155 ͑3͒ J71-J78 ͑2008͒ J76 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 132.174.254.155 Downloaded on 2015-04-05 to IP
A phosphor-converted light-emitting diode structure with an increased phosphor extraction efficiency owing to the ring remote phosphor structure achieves a maximum luminous efficacy of 145 lm/W at 20 mA and a maximum luminous flux of 132 lm at 400 mA. The ring remote phosphor structure consists of an inverted cone lens encapsulant and a surrounding ring remote phosphor layer. Ray-tracing simulations demonstrate that the phosphor extraction efficiency of the ring remote phosphor structure exceeds 93%. A high phosphor extraction efficiency is achieved by decreasing the re-emitting light from the ring remote phosphor layer to the absorptive light-emitting diode (LED) chip. Our results further demonstrate that the ring remote phosphor structure device has a radiation pattern as a bi-wing, which is more appropriate for solid-state lighting owing to the low glare.
A mathematical model describing the transient hydraulic head distribution induced by constant-head pumping/injection at a partially penetrating well in a radial two-zone confined aquifer is a mixed-type boundary value problem. The analytical solution of the model is in terms of an improper integral with an integrand having a singularity at the origin. The solution should rely on numerical methods to evaluate the integral and handle the problems of convergence and singularity. This study aims at developing a new approximate solution describing the transient hydraulic head distribution for a constant-head test (CHT) at a partially penetrating well in the aquifer. This approximate solution is acquired based on a time-dependent diffusion layer approximation proposed in the field of electrochemistry. The diffusion layer can be analogous to the radius of influence in the area of well hydraulics. The approximate solution is in terms of modified Bessel functions for aquifers with a partially penetrating well and can reduce to a simpler form in terms of a natural logarithmic function for the case of well full penetration. The predicted hydraulic heads from the present approximate solution are compared with those estimated by the Laplace-domain solution of the model. The result shows that the predicted spatial head distributions are accurate in the formation zone and fairly good in the skin zone. In addition, the present solution gives an accurate temporal head distribution at a specific location when the radius of influence is far away from the observation wells. This newly developed approximate solution has advantages of easy computing and good accuracy from practical viewpoint, and thus is a handy tool to evaluate temporal and spatial hydraulic head distributions for the CHT.
Nicotine in tobacco smoke is considered carcinogenic in several malignancies including lung cancer. The high incidence of lung adenocarcinoma (LAC) in non-smokers, however, remains unexplained. Although LAC has long been less associated with smoking behavior based on previous epidemiological correlation studies, the effect of environmental smoke contributing to low-dose nicotine exposure in non-smoking population could be underestimated. Here we provide experimental evidence of how low-dose nicotine promotes LAC growth in vitro and in vivo. Screening of nicotinic acetylcholine receptor subunits in lung cancer cell lines demonstrated a particularly high expression level of nicotinic acetylcholine receptor subunit α5 (α 5-nAChR) in LAC cell lines. Clinical specimen analysis revealed up-regulation of α 5-nAChR in LAC tumor tissues compared to non-tumor counterparts. In LAC cell lines α 5-nAChR interacts with epidermal growth factor receptor (EGFR), positively regulates EGFR pathway, enhances the expression of epithelial-mesenchymal transition markers, and is essential for low-dose nicotine-induced EGFR phosphorylation. Functionally, low-dose nicotine requires α 5-nAChR to enhance cell migration, invasion, and proliferation. Knockdown of α 5-nAChR inhibits the xenograft tumor growth of LAC. Clinical analysis indicated that high level of tumor α 5-nAChR is correlated with poor survival rates of LAC patients, particularly in those expressing wild-type EGFR. Our data identified α 5-nAChR as an essential mediator for low-dose nicotine-dependent LAC progression possibly through signaling crosstalk with EGFR, supporting the involvement of environmental smoke in tumor progression in LAC patients.
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