Quenching and Trapping of Lyman-α Fluorescence at Large Optical Depths

1973 ◽  
Vol 51 (10) ◽  
pp. 1517-1520 ◽  
Author(s):  
Leon Francis Phillips
Keyword(s):  
Steady State ◽  
Phase Shift ◽  
Cross Sections ◽  
Rate Constants ◽  
Atomic Hydrogen ◽  
Fluorescence Decay ◽  
Hydrogen Gas ◽  
Shift Method ◽  
Steady State Fluorescence ◽  
Phase Shift Method

Trapping times for 121.6 nm hydrogen resonance radiation in atomic hydrogen gas have been determined by a phase shift method. Rate constants for quenching of H atoms in the n = 2 level have been calculated from the measured trapping times together with the slopes of Stern–Volmer plots obtained under steady-state conditions. The results indicated that the trapping times characteristic of fluorescence decay, and of steady-state fluorescence, differed by less than a factor of two. For quenching by O2, Ar, and He, the values of quenching cross sections obtained (all × 10−16 cm2) were 30 ± 8, 0.9 ± 0.4, and 0.4 ± 0.2, respectively.

Migration by phase shift—An algorithmic description for array processors

Geophysics ◽  
1979 ◽  
Vol 44 (10) ◽  
pp. 1661-1666 ◽  
Author(s):  
Augustin A. Dubrulle ◽  
Jenö Gazdag
Keyword(s):  
Phase Shift ◽  
Frequency Domain ◽  
Cross Sections ◽  
Initial Conditions ◽  
Depth Interval ◽  
Array Processor ◽  
Seismic Section ◽  
Shift Method ◽  
Initial Values ◽  
Phase Shift Method

The phase shift method (Gazdag, 1978) is based on the solution, in the frequency domain, of an approximation (Claerbout, 1976) to the one‐way wave equation with initial conditions defined by a zero‐offset seismic section. Wave velocity is assumed to be constant within each layer of the section grid and is allowed to vary from layer to layer. Under these conditions, the equation written in the frequency domain reduces to a system of independent ordinary differential equations with initial values that can be solved analytically for each layer. The integration process simply amounts to multiplying the initial values by a complex number of unit modulus. The main advantages of this method are simplicity, stability, and high accuracy, since the precision of the Fourier approximation is limited only by the granularity of the seismic section. From a practical viewpoint of computer implementation, the phase shift method offers a great deal of flexibility. Some accuracy can be traded for speed, as needed, by excluding the waves traveling at an angle that exceeds a specified limit, or by ignoring frequencies at the higher end of the spectrum. The migration of a group of reflections can be excluded as well, since the phase shift angles can be accumulated for application to the frequency representation of the section only within a specified depth interval. The most interesting feature of the method may well reside in the fact that the Fourier coefficients of a seismic section can be treated independently of one another. This is of particular importance if the method is implemented for an array processor. In this case, cross‐sections of the frequency data can be sent to the array processor one‐by‐one (or in groups, as may be suitable) for phase shift operations, at minimal storage cost. A formulation of the method for an array processor is outlined here, which takes advantage of the features mentioned above. It is described in a step‐wise algorithmic fashion, using natural language and standard mathematical notations. Functions for discrete Fourier transformations, evaluation of square roots and circular functions (or fast table look‐up or interpolation), and vector reversal are assumed to exist in the array processor, in addition to elementary vector operations. This formulation can also be used for efficient implementation on conventional computers.

Determination by the phase shift method of the absolute rate constants of reactions of O(3P) atoms with olefins at 25°C

1974 ◽  
Vol 6 (5) ◽  
pp. 741-751 ◽  
Author(s):  
Shozo Furuyama ◽  
Roger Atkinson ◽  
Agustin J. Colussi ◽  
R. J. Cvetanović
Keyword(s):  
Phase Shift ◽  
Rate Constants ◽  
Absolute Rate ◽  
Shift Method ◽  
The Absolute ◽  
Phase Shift Method

A HIGHLY ACCURATE ULTRASONIC MEASUREMENT SYSTEM FOR TREMOR USING BINARY AMPLITUDE-SHIFT-KEYING AND PHASE-SHIFT METHOD

2003 ◽  
Vol 15 (02) ◽  
pp. 61-67 ◽  
Author(s):  
MENG-HSIANG YANG ◽  
K. N. HUANG ◽  
C. F. HUANG ◽  
S. S. HUANG ◽  
M. S. YOUNG
Keyword(s):  
Phase Shift ◽  
Measurement System ◽  
Low Cost ◽  
Phase Shifts ◽  
Ultrasonic Waves ◽  
Shift Method ◽  
Narrow Bandwidth ◽  
Shift Keying ◽  
Modulation Signal ◽  
Phase Shift Method

A highly accurate Binary Amplitude-Shift-Keyed (BASK) ultrasonic tremor measurement system for use in isothermal air is developed. In this paper, we present a simple but efficient algorithm based upon phase shifts generated by three ultrasonic waves of different frequencies. By the proposed method, we can conduct larger range measurement than the phase-shift method and also get higher accuracy compared with the time-of-flight (TOF) method. Our microcomputer-based system includes two important parts. One of which is BASK modulation signal generator. The other is a phase meter designed to record and compute the phase shifts of the three different frequencies and the result motion is then sent to either an LCD for display or a PC for calibration. Experiments are done in the laboratory using BASK modulation for the frequencies of 200 Hz and 1 kHz with a 40 kHz carrier. The measurement accuracy of this measurement system in the reported experiments is within +/- 0.98 mm. The main advantages of this ultrasonic tremor measurement system are high resolution, narrow bandwidth requirement, low cost, and easy to be implemented.

A digital phase shift method for phase compensation of electronic transformer

2017 ◽  
Vol 40 (13) ◽  
pp. 3690-3695 ◽  
Author(s):  
Wei Wei ◽  
Han-miao Cheng ◽  
Fan Li ◽  
Deng-ping Tang ◽  
Shui-bin Xia
Keyword(s):  
Phase Shift ◽  
Phase Error ◽  
Recursion Formula ◽  
Rogowski Coil ◽  
Shift Method ◽  
Electronic Transformer ◽  
Digital Phase ◽  
Fitting Algorithm ◽  
Fixed Phase ◽  
Phase Shift Method

When sampling analog signal, the electronic transformer generally produces a fixed phase error that will compromise the measurement accuracy and require a phase shift method for correction. In this paper, we propose a digital phase shift method based on least squares fitting algorithm and derive the recursion formula of digital phase shift. The simulation has also been done to analysis its performance. The result shows that the method has high phase shift resolution and precision. By applying the method to an electronic transformer based on Rogowski coil, we have experimentally verified the feasibility and validity of the method.

scholarly journals Mechanism of a Disassembly Driven Sensing System Studied by Stopped-Flow Kinetics

2021 ◽  
Author(s):  
Cara Gallo ◽  
Suma S. Thomas ◽  
Allison Selinger ◽  
Fraser Hof ◽  
Cornelia Bohne
Keyword(s):  
Steady State ◽  
Rate Constants ◽  
Artificial Saliva ◽  
Global Analysis ◽  
Dissociation Rate ◽  
Stopped Flow ◽  
Steady State Fluorescence ◽  
Saliva Analysis ◽  
Binding Isotherms ◽  
Dissociation Rate Constants

<div> Mechanistic studies were carried out on the kinetics for the assembly of a DimerDye (DD12) and the binding of the monomeric DimerDye (DD1) with nicotine in aqueous buffer and artificial saliva. DD12 is non-fluorescent, while monomeric DD1 and DD1-nicotine fluoresce. Binding isotherms were determined from steady-state fluorescence experiments. The report includes measurements of the steady-state fluorescence at pHs 2.2, 6.3 and 12.1, and stopped-flow kinetic data for the homodimerization forming DD12 and DD1-nicotine formation in buffer and artificial saliva. Analysis of the homodimerization kinetics led to the recovery of the association and dissociation rate constants for DD12. These rate constants were used in the global analysis for the coupled kinetics for DD1-nicotine formation, which led to the determination of the association and dissociation rate constants for nicotine binding to DD1.</div>

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