排序方式: 共有25条查询结果,搜索用时 15 毫秒
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Cletus A D'Souza Vikramjit Chopra Richard Varhol Yuan-Yun Xie Slavita Bohacec Yongjun Zhao Lisa LC Lee Mikhail Bilenky Elodie Portales-Casamar An He Wyeth W Wasserman Daniel Goldowitz Marco A Marra Robert A Holt Elizabeth M Simpson Steven JM Jones 《BMC neuroscience》2008,9(1):1-14
Background
We have recorded responses from single neurons in murine visual cortex to determine the effectiveness of the input from the two murine cone photoreceptor mechanisms and whether there is any unique selectivity for cone inputs at this higher region of the visual system that would support the possibility of colour vision in mice. Each eye was stimulated by diffuse light, either 370 (strong stimulus for the ultra-violet (UV) cone opsin) or 505 nm (exclusively stimulating the middle wavelength sensitive (M) cone opsin), obtained from light emitting diodes (LEDs) in the presence of a strong adapting light that suppressed the responses of rods.Results
Single cells responded to these diffuse stimuli in all areas of striate cortex. Two types of responsive cells were encountered. One type (135/323 – 42%) had little to no spontaneous activity and responded at either the on and/or the off phase of the light stimulus with a few impulses often of relatively large amplitude. A second type (166/323 – 51%) had spontaneous activity and responded tonically to light stimuli with impulses often of small amplitude. Most of the cells responded similarly to both spectral stimuli. A few (18/323 – 6%) responded strongly or exclusively to one or the other spectral stimulus and rarely in a spectrally opponent manner.Conclusion
Most cells in murine striate cortex receive excitatory inputs from both UV- and M-cones. A small fraction shows either strong selectivity for one or the other cone mechanism and occasionally cone opponent responses. Cells that could underlie chromatic contrast detection are present but extremely rare in murine striate cortex. 相似文献3.
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Flávia R. O. Silva Camila T. Nabeshima Maria H. Bellini Nestor Schor Nilson D. Vieira Jr Lilia C. Courrol 《Journal of fluorescence》2013,23(1):131-135
This paper describes the elimination of porphyrins by feces. It was demonstrated that porphyrin accumulates substantially more in tumors than in normal tissues, and consequently more PPIX reaches the blood of patients and animals with tumors, and then, it needs to be eliminated. The fluorescence of feces revealed that there are large amounts of PPIX in the excreta of animals with cancer comparing with healthy animals. The autofluorescence of feces porphyrin extracted with acetone was analyzed using fluorescence spectroscopy of animals inoculated with DU145 cells into the prostate and healthy animals to monitor the PPIX concentration. Emission spectra were obtained by exciting the samples at 405 nm. Significant differences were observed in autofluorescence intensities measured in the 575–725 nm spectral regions for the studied groups. The results showed a noninvasive, simple, rapid and sensitive method to detect cancer by feces analysis. 相似文献
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Ricardo Elgul Samad Lilia Coronato Courrol Ademar Benévolo Lugão Anderson Zanardi de Freitas Nilson Dias Vieira 《Radiation Physics and Chemistry》2010,79(3):355-357
We report here the creation of color centers in commercial, transparent PMMA samples by ultrashort pulses from a Ti:Sapphire laser emitting at 800 nm, with spatial control. Although the 800 nm photon energy is not sufficient to ionize the polymer, the centers are created following a multiphotonic absorption that causes the ionization. We propose that the free electrons quivering motion on the pulse electric field displaces atoms from its equilibrium positions, creating free radicals and double bonds that coalesce into color centers. The absorption and emission spectra of the centers were measured, but a dose-like curve could not be built due to the presence of damages created along with the centers that scatter the excitation and emission lights due to the commercial sample's poor optical quality. 相似文献
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Juliana Steffens Eduardo Landulfo Lilia Coronato Courrol Roberto Guardani 《Journal of fluorescence》2011,21(3):859-864
Crude petroleum oils are complex mixtures of different compounds (mainly organic), which are obtained from an extensive range
of different geological sources. The fluorescence of crude petroleum oils derives largely from the aromatic hydrocarbon fraction,
and this fluorescence emission is strongly influenced by the chemical composition (e.g., fluorophore and quencher concentrations)
and physical characteristics (e.g., viscosity and optical density) of the oil. The fluorescence spectroscopy (FS) is increasingly
used in petroleum technology due the availability of better optical detection techniques, because FS offers high sensitivity,
good diagnostic potential, and relatively simple instrumentation. In this work we analyzed crude petroleum at different dilution
in Nujol, a transparent mineral oil. The main objective of this work was to verify the possibility to measure crude oil emission
spectroscopic without use of volatile solvents. The mixtures of nujol with different -crude oil concentrations were measured
with a 10 mm optical path cuvette thus simplifying the fluorescence spectroscopy signal detection. The emission spectra were
obtained by exciting the samples with a 400 W Xenon lamp at 350 nm, 450 nm and 532 nm. The emissions of the samples were collected
perpendicularly with the excitation axis. 相似文献
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Epitaxial La1−x
Pb
x
MnO3 (LPMO) thin films, grown on (100) SrTiO3 substrates by laser ablation technique at different temperatures between 600 and 850°C, have been characterized for electrical
and magnetic properties. The temperature dependence of resistivity showed that the metal-insulator transition temperature
(T
MI) decreases with increasing substrate temperature, which has been attributed to decrease in Pb content in the filsm. The YBa2Cu3O
x
/La1−x
MnO3 heterostructures, exhibiting both superconductivity and ferromagnetism, have been fabricated. 相似文献
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L. C. Courrol R. E. Samad L. Gomes I. M. Ranieri S. L. Baldochi A. Z. Freitas S. P. Morato N. D. Vieira Jr. 《Laser Physics》2006,16(2):331-335
Color centers are lattice vacancy defects trapping electrons or holes. They are easily created in single crystals by irradiation with ionizing radiation. We report the production of color centers in LiF and LiYF4 single crystals by ultrashort high-intensity laser pulses (60 fs, 12.5 GW). An intensity threshold for color center creation of 1.9 and 2 TW/cm2 was determined in YLF and LiF, respectively, which is slightly smaller than the continuum generation threshold. Due to the high energy density of the coherent radiation of the focused laser beam, we were able to identify a large amount of F centers, which gave rise to aggregates such as F2, F 2 + , and F 3 + . The proposed mechanism of formation is based on multiphoton excitation, which also produces short-lived F 2 + centers. It is also shown that it is possible to write tracks in the LiF crystals with dimensional control. 相似文献
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Correlation Between Autofluorescence Intensity and Tumor Area in Mice Bearing Renal Cell Carcinoma 总被引:3,自引:2,他引:1
Bellini MH Coutinho EL Courrol LC Rodrigues de Oliveira Silva F Vieira Júnior ND Schor N 《Journal of fluorescence》2008,18(6):1163-1168
Protoporphyrin IX (PpIX) is a porphyrin derivative that is accumulated in cancerous tissue in consequence of the tumor-specific
metabolic alterations. The aim of this study was to evaluate the accumulation of PpIX in mice bearing renal cell carcinoma
by spectroscopy analysis. A total of 24 male Balb/c mice, 6 weeks old, were divided into six groups: Normal (without inoculation
of tumor cells) and 4, 8, 13, 16, and 20 days after inoculation of tumor cells. The orthotopic tumor model of renal cancer
was used. Murine renal cell carcinoma (Renca cells) were inoculated into the subcapsular space of the kidney. Normal and tumor-bearing
kidneys in different progression stages were removed and analyzed by ex-vivo spectroscopy and by microscopy, for tumor histometric
analysis. Emission spectra were obtained by exciting the samples at 405 nm. Significant differences between normal and tumor-bearing
kidneys in autofluorescence shape occurred in the 600–700 nm spectral region. A good correlation was found between emission
band intensity at 635 nm and the tumor area. 相似文献