scholarly journals Digital imaging fluorescence microscopy: spatial heterogeneity of photobleaching rate constants in individual cells.

1985 ◽  
Vol 100 (4) ◽  
pp. 1309-1323 ◽  
Author(s):  
D M Benson ◽  
J Bryan ◽  
A L Plant ◽  
A M Gotto ◽  
L C Smith
Keyword(s):  
Rate Constants ◽  
High Speed ◽  
Signal To Noise Ratio ◽  
High Sensitivity ◽  
Experimental Conditions ◽  
Excitation Light ◽  
Illumination Time ◽  
Probe Concentration ◽  
High Speed Data Acquisition ◽  
High Speed Data

Photobleaching and related photochemical processes are recognized experimental barriers to quantification of fluorescence by microscopy. We have measured the kinetics of photobleaching of fluorophores in living and fixed cells and in microemulsions, and have demonstrated the spatial variability of these processes within individual cells. An inverted fluorescence microscope and a high-sensitivity camera, together with high-speed data acquisition by a computer-controlled image processor, have been used to control precisely exposure time to excitation light and to record images. To improve the signal-to-noise ratio, 32 digital images were integrated. After correction for spatial variations in camera sensitivity and background fluorescence, the images of the relative fluorescence intensities for 0.065 micron2 areas in the object plane were obtained. To evaluate photobleaching objectively, an algorithm was developed to fit a three-parameter exponential equation to 20 images recorded from the same microscope field as a function of illumination time. The results of this analysis demonstrated that the photobleaching process followed first-order reaction kinetics with rate constants that were spatially heterogeneous and varied, within the same cell, between 2- and 65-fold, depending on the fluorophore. The photobleaching rate constants increased proportionally with increasing excitation intensity and, for benzo(a)pyrene, were independent of probe concentration over three orders of magnitude (1.25 microM to 1.25 mM). The propensity to photobleach was different with each fluorophore. Under the cellular conditions used in these studies, the average rates of photobleaching decreased in this order: N-(7-nitrobenz-2-oxa-1,3-diazole)-23,24-dinor-5-cholen-22-amine-3 beta-ol greater than acridine orange greater than rhodamine-123 greater than benzo(a)pyrene greater than fluorescein greater than tetramethylrhodamine greater than 1,1'dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine. The photobleaching appears to be an oxidation reaction, in that the addition of saturated solutions of Na2S2O5 to mineral oil microemulsions eliminated photobleaching of N-(7-nitrobenz-2-oxa-1,3-diazole)-23,24-dinor-5-cholen-22-amine-3 beta-ol or benzo(a)pyrene. We identified experimental conditions to observe, without detectable photobleaching, fluorophores in living cells, which can not be studied anaerobically. Useful images were obtained when excitation light was reduced to eliminate photobleaching, as determined from zero-time images calculated from the exponential fit routine.(ABSTRACT TRUNCATED AT 400 WORDS)

High-speed electron counting system for TV scan-rate secondary-electron images of SEM

1991 ◽  
Vol 49 ◽  
pp. 512-513
Author(s):  
S. Yamada ◽  
T. Ito ◽  
K. Gouhara ◽  
Y. Uchikawa
Keyword(s):  
High Speed ◽  
Signal To Noise Ratio ◽  
Pulse Height ◽  
Counting System ◽  
Main Amplifier ◽  
Electron Counting ◽  
Scan Rate ◽  
High Speed Data Acquisition ◽  
High Speed Data ◽  
New System

We reported a system for counting secondary electrons (SEs), with which SE image quality of SEM such as signal to noise ratio (SNR) and linearity were improved, in particular under the condition of low irradiation. The system had been developed for slow-scan rates (over 6 sec/flame). The TVscan rate (1/30 sec/frame) is often used to avoid charging of insulators and biological specimens. We developed a high speed electron counting system with which SE images can be obtained in the TVscan rate. This paper describes the new system attached to an SEM, and some experimental results obtained with it.A schematic diagram of the new system is shown in FIG.1, which consists of four main parts; Everhart-Thornley type detector (DT), main amplifier (MA), counter (CNT) and image processor (IP). In designing the system we took precautions for high speed data acquisition in the TV-scan rate. As described in the previous papers, the thermal noise and the fluctuations of the pulse height of the SE signal contained in the output of the DT can be removed through the CNT.

A Design of High Speed Data Acquisition and Storage System

2013 ◽  
Vol 367 ◽  
pp. 541-543
Author(s):  
Yun Peng Li
Keyword(s):  
Speech Recognition ◽  
High Speed ◽  
Storage System ◽  
Nand Flash ◽  
Flash Storage ◽  
Reading And Writing ◽  
Hardware Development ◽  
High Speed Data Acquisition ◽  
High Speed Data ◽  
And Storage

This article focuses on research and implementation of a kind of solid storage system that is based on NAND flash which can store the data with high speed and huge capacity. A design with quad 1.25Gsps ADC and flash storage array with 1TB is demonstrated in the paper. The design is applied widely in many fields such as radar, communication and speech recognition. The detail of hardware development is also introduced in the thesis. In addition, a method is discussed to approve the reading and writing bandwidth by parallel operations on multiple pieces of flash. By using the method, the data bandwidth is arrived 6GB/S.

Design of Data Transfer System Based on PCI Express Interface Applied in High-Speed Railway

2012 ◽  
Vol 229-231 ◽  
pp. 1543-1546
Author(s):  
Xiao Bo Zhou ◽  
Min Xia ◽  
Hai Long Cheng
Keyword(s):  
Data Acquisition ◽  
Data Transmission ◽  
High Speed ◽  
Data Transfer ◽  
Transmission Method ◽  
High Speed Railway ◽  
Pci Express ◽  
Data Acquisition Card ◽  
High Speed Data Acquisition ◽  
High Speed Data

To improve data transmission performance of the data acquisition card, a design of high-speed data transmission system is proposed in the thesis. Using FPGA of programmable logic devices, adopting Verilog HDL of hardware description language, the design of modularization and DMA transmission method is implemented in FPGA. Eventually the design implements the data transmission with high-speed through PCI Express interface. Through simulation and verification based on hardware system, this design is proved to be feasible and can satisfy the performance requirements of data transmission in the high-speed data acquisition card applied in high-speed railway communication. The design also has some value of application and reference for a universal data acquisition card.

scholarly journals Cloud shadow speed sensor

2014 ◽  
Vol 7 (6) ◽  
pp. 1693-1700 ◽  
Author(s):  
V. Fung ◽  
J. L. Bosch ◽  
S. W. Roberts ◽  
J. Kleissl
Keyword(s):  
High Speed ◽  
Sensor Data ◽  
Motion Vectors ◽  
Speed Sensor ◽  
Correlation Algorithm ◽  
High Speed Data Acquisition ◽  
Economical System ◽  
High Speed Data ◽  
Mean Square Difference ◽  
Artificial Shading

Abstract. Changing cloud cover is a major source of solar radiation variability and poses challenges for the integration of solar energy. A compact and economical system is presented that measures cloud shadow motion vectors to estimate power plant ramp rates and provide short-term solar irradiance forecasts. The cloud shadow speed sensor (CSS) is constructed using an array of luminance sensors and a high-speed data acquisition system to resolve the progression of cloud passages across the sensor footprint. An embedded microcontroller acquires the sensor data and uses a cross-correlation algorithm to determine cloud shadow motion vectors. The CSS was validated against an artificial shading test apparatus, an alternative method of cloud motion detection from ground-measured irradiance (linear cloud edge, LCE), and a UC San Diego sky imager (USI). The CSS detected artificial shadow directions and speeds to within 15° and 6% accuracy, respectively. The CSS detected (real) cloud shadow directions and speeds with average weighted root-mean-square difference of 22° and 1.9 m s−1 when compared to USI and 33° and 1.5 m s−1 when compared to LCE results.

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