Single Photon Counting
Mostrando 1-12 de 21 artigos, teses e dissertações.
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1. Performance assessment of the single photon emission microscope: high spatial resolution SPECT imaging of small animal organs
The single photon emission microscope (SPEM) is an instrument developed to obtain high spatial resolution single photon emission computed tomography (SPECT) images of small structures inside the mouse brain. SPEM consists of two independent imaging devices, which combine a multipinhole collimator, a high-resolution, thallium-doped cesium iodide [CsI(Tl)] col
Braz J Med Biol Res. Publicado em: 06/11/2013
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2. SINGLE PHOTON COUNTING IN THE NEAR- AND MID-INFRARED VIA FREQUENCY UP-CONVERSION APPLIED TO QUANTUM COMMUNICATIONS / CONTAGEM DE FÓTONS NO INFRAVERMELHO PRÓXIMO E MÉDIO VIA CONVERSÃO DE FREQÜÊNCIAS APLICADA A COMUNICAÇÕES QUÂNTICAS
Two single photon counting devices, operating at near- and mid-infrared wavelengths, are introduced and experimentally investigated. Both use a twostage technique, comprised of an initial frequency up-conversion procedure inside a nonlinear crystal followed by a silicon avalanche photodiode. Whereas the first project consists on detection of single photons a
Publicado em: 2007
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3. Evaluation of single-photon-counting measurements of excited-state lifetimes
An extremely short instrumental response function for a single-photon-counting system has been obtained by using a low-jitter photomultiplier tube, fast amplification of the single photoelectron pulse from this photomultiplier, a constant fraction discriminator with a wide bandwidth input, and a stable reference timing signal. This synchronously mode-locked
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4. Scanning two-photon fluctuation correlation spectroscopy: particle counting measurements for detection of molecular aggregation.
Scanning fluctuation correlation spectroscopy (FCS) is an experimental technique capable of measuring particle number concentrations by monitoring spontaneous equilibrium fluctuations in the local concentration of a fluorescent species in a small (femtoliter) subvolume of a sample. The method can be used to detect molecular aggregation for dilute, submicromo
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5. Fluorescence tomographic imaging in turbid media using early-arriving photons and Laplace transforms
We present a multichannel tomographic technique to detect fluorescent objects embedded in thick (6.4 cm) tissue-like turbid media using early-arriving photons. The experiments use picosecond laser pulses and a streak camera with single photon counting capability to provide short time resolution and high signal-to-noise ratio. The tomographic algorithm is bas
The National Academy of Sciences of the USA.
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6. Intrinsic noise in locust photoreceptors.
1. In locust photoreceptors, the amplitude of the response to light pulses lasting less than 20 ms depends solely upon the number of absorbed photons, which can be estimated at low intensities by counting quantum bumps. Consequently, each receptor can be operated as a calibrated photon counter. 2. Three types of noise in receptor responses have been identifi
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7. Molecular spectroscopy and dynamics of intrinsically fluorescent proteins: Coral red (dsRed) and yellow (Citrine)
Gene expression of intrinsically fluorescent proteins in biological systems offers new noninvasive windows into cellular function, but optimization of these probes relies on understanding their molecular spectroscopy, dynamics, and structure. Here, the photophysics of red fluorescent protein (dsRed) from discosoma (coral), providing desired longer emis
The National Academy of Sciences.
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8. Conformational transitions monitored for single molecules in solution.
Phenomena that can be observed for a large number of molecules may not be understood if it is not possible to observe the events on the single-molecule level. We measured the fluorescence lifetimes of individual tetramethylrhodamine molecules, linked to an 18-mer deoxyribonucleotide sequence specific for M13 DNA, by time-resolved, single-photon counting in a
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9. A multiple-capillary electrophoresis system for small-scale DNA sequencing and analysis.
A five-capillary system has been developed for DNA sequencing and analysis. The post-column fluorescence detector is based on a sheath-flow cuvette. The instrument provides uniform and continuous illumination of the samples. The cuvette virtually eliminates cross-talk in the fluorescence signal between capillaries. Discrete single-photon counting avalanche p
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10. Circadian rhythms of cyanobacteria: monitoring the biological clocks of individual colonies by bioluminescence.
Reproducible circadian rhythms of bioluminescence from individual colonies of cyanobacteria (Synechococcus sp. strain PCC 7942) has been observed. Phenotypic monitoring of colonies on agar plates will enable us to genetically analyze the molecular mechanism of the circadian clock of cyanobacteria by screening for clock mutants. By the introduction of a bacte
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11. The fluorescence resonance energy transfer (FRET) gate: A time-resolved study
The two-step energy-transfer process in a self-assembled complex comprising a cationic conjugated polymer (CCP) and a dsDNA is investigated by using pump-dump-emission spectroscopy and time-correlated single-photon counting; energy is transferred from the CCP to an ethidium bromide (EB) molecule intercalated into the dsDNA through a fluorescein molecule link
National Academy of Sciences.
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12. Optical imaging of Renilla luciferase reporter gene expression in living mice
Imaging reporter gene expression in living subjects is a rapidly evolving area of molecular imaging research. Studies have validated the use of reporter genes with positron emission tomography (PET), single photon emission computed tomography (SPECT), MRI, fluorescence with wild-type and mutants of green fluorescent protein, as well as bioluminescence u
The National Academy of Sciences.