We investigated the cathode luminescence characteristics of CsI(Na)and CsI(Tl)crystals by the spectrum and structure properties at room temperature.We fabricated three different sizes of CsI(Na)and CsI(Tl)crystals and...We investigated the cathode luminescence characteristics of CsI(Na)and CsI(Tl)crystals by the spectrum and structure properties at room temperature.We fabricated three different sizes of CsI(Na)and CsI(Tl)crystals and measured their luminescence spectra under cathode rays.We found that CsI(Na)cathode luminescence peaks appear at 420 and 305 nm,and CsI(Tl)cathode luminescence peaks are 540 and 410 nm,the grain size affects CsI(Na)luminescence significantly,and the Na-related420 nm luminescence intensified relatively when the average grain size reaches^20μm,which becomes weak when the grain size is down to nano-scale.But the cathode luminescence spectra of CsI(Tl)crystals with different size have no obvious changes.Our explanations for these phenomena are that the different impurities in the same host material CsI lead to different luminescence mechanisms.These cathode luminescence characteristics indicate the suitability of CsI(Na)and CsI(Tl)crystals to match photomultiplier tube for large area crystal detector development.展开更多
Juveniles of the shore crab Hemigrapsus oregonensis are highly variable in color, ranging from the typical yellowish- green of adults to pure white and myriad patterns of white mottling and other disruptive markings, ...Juveniles of the shore crab Hemigrapsus oregonensis are highly variable in color, ranging from the typical yellowish- green of adults to pure white and myriad patterns of white mottling and other disruptive markings, but large individuals with white coloration appear to be very rare. Using image analysis to quantify the relative ＂whiteness＂ of beaches, we sampled crabs from nine locations in Washington State that varied widely in their amount of shell fragments and other light-colored material. The total proportion of white individuals in the different locations was strongly correlated to the proportion of white material on the beaches, but there was a striking difference between sexes. Although white specimens of both sexes declined significantly at sizes above 10 mm carapace width, white females generally persisted throughout the entire female size range on lighter-colored beaches while white males larger than 10 mm were virtually absent from all of the sampled populations. Pure white males held on dark backgrounds in captivity remained white, as they lack the dark chromatophores in their hypoderrnis needed to change color; off-white males became darker and in some cases lightened up again when transferred back to a white background. Behavioral differences between the sexes may result in differential mortality of white individuals by visual predators [Current Zoology 61 （4） 729-738, 2015 ].展开更多
基金supported by the Fundamental Research Funds for the Central Universities(Grant No.11QG14)
文摘We investigated the cathode luminescence characteristics of CsI(Na)and CsI(Tl)crystals by the spectrum and structure properties at room temperature.We fabricated three different sizes of CsI(Na)and CsI(Tl)crystals and measured their luminescence spectra under cathode rays.We found that CsI(Na)cathode luminescence peaks appear at 420 and 305 nm,and CsI(Tl)cathode luminescence peaks are 540 and 410 nm,the grain size affects CsI(Na)luminescence significantly,and the Na-related420 nm luminescence intensified relatively when the average grain size reaches^20μm,which becomes weak when the grain size is down to nano-scale.But the cathode luminescence spectra of CsI(Tl)crystals with different size have no obvious changes.Our explanations for these phenomena are that the different impurities in the same host material CsI lead to different luminescence mechanisms.These cathode luminescence characteristics indicate the suitability of CsI(Na)and CsI(Tl)crystals to match photomultiplier tube for large area crystal detector development.
基金We thank the staff of the Shannon Point Marine Center and the National Science Foundation Research Experiences for Undergraduates program. We are also grateful to Rachael Ream, Justin Ly, and Marc Baciagalupi for their help in the field, and for the very helpful comments from two anonymous referees.
文摘Juveniles of the shore crab Hemigrapsus oregonensis are highly variable in color, ranging from the typical yellowish- green of adults to pure white and myriad patterns of white mottling and other disruptive markings, but large individuals with white coloration appear to be very rare. Using image analysis to quantify the relative ＂whiteness＂ of beaches, we sampled crabs from nine locations in Washington State that varied widely in their amount of shell fragments and other light-colored material. The total proportion of white individuals in the different locations was strongly correlated to the proportion of white material on the beaches, but there was a striking difference between sexes. Although white specimens of both sexes declined significantly at sizes above 10 mm carapace width, white females generally persisted throughout the entire female size range on lighter-colored beaches while white males larger than 10 mm were virtually absent from all of the sampled populations. Pure white males held on dark backgrounds in captivity remained white, as they lack the dark chromatophores in their hypoderrnis needed to change color; off-white males became darker and in some cases lightened up again when transferred back to a white background. Behavioral differences between the sexes may result in differential mortality of white individuals by visual predators [Current Zoology 61 （4） 729-738, 2015 ].
