New results in applied scattering theory: the physical-statistics approach, including strong multiple scatter versus classical statistical-physical methods* and the Born and Rytov approximations versus exact strong scatter probability distributions

2002 ◽  
Vol 12 (1) ◽  
pp. 99-144 ◽  
Author(s):  
David Middleton
Keyword(s):  
Scattering Theory ◽  
Probability Distributions ◽  
Physical Methods ◽  
Multiple Scatter

The multiple scattering of waves in irregular media. II. Spatial autocorrelation functions

1968 ◽  
Vol 307 (1491) ◽  
pp. 471-492 ◽  
Keyword(s):  
Refractive Index ◽  
Spatial Autocorrelation ◽  
Probability Distributions ◽  
Essential Feature ◽  
Joint Probability ◽  
Joint Probability Distribution ◽  
Autocorrelation Functions ◽  
Phase Fluctuations ◽  
Multiple Scatter ◽  
Special Cases

When a wave passes through a large thickness of a non-absorbing medium containing weak random irregularities of refractive index, large amplitude and phase fluctuations of the wave field can develop. In a previous paper it was shown how to calculate the probability distributions and average values of these fluctuations. An essential feature of the treatment was that it took into account waves which have been scattered many times (multiple scatter). The present paper considers the spatial autocorrelation functions of the intensity and phase fluctuations in a plane parallel to the wave front of the incident wave for conditions of multiple scatter. These autocorrelation functions are important since they are used in studying the scintillation of radio signals from stellar sources, and yield information about the scattering medium causing the scintillations. The autocorrelation functions of the field quantities depend on the moment matrix of a four-dimensional joint probability distribution. The moments, which are elements of the matrix, are certain average values of the scattered field. A set of integro-differential equations is formulated for the moments and solved analytically for some special cases. General solutions for the moments are obtained by numerical integration, in the case where the irregularities of refractive index have a Gaussian autocorrelation function. Curves for the spatial autocorrelation functions of intensity and phase in this case are given for different distances in the medium.

Southern Hemisphere Seti Survey: Five Years of Project Meta II

1997 ◽  
Vol 161 ◽  
pp. 611-621
Author(s):  
Guillermo A. Lemarchand ◽  
Fernando R. Colomb ◽  
E. Eduardo Hurrell ◽  
Juan Carlos Olalde
Keyword(s):  
Southern Hemisphere ◽  
Scattering Theory ◽  
Galactic Plane ◽  
Narrow Band ◽  
Neutral Hydrogen ◽  
Sky Survey ◽  
Inertial Frames ◽  
Interstellar Scattering ◽  
Extraterrestrial Origin ◽  
Spectral Channels

AbstractProject META II, a full sky survey for artificial narrow-band signals, has been conducted from one of the two 30-m radiotelescopes of the Instituto Argentino de Radioastronomía (IAR). The search was performed near the 1420 Mhz line of neutral hydrogen, using a 8.4 million channels Fourier spectrometer of 0.05 Hz resolution and 400 kHz instantaneous bandwidth. The observing frequency was corrected both for motions with respect to three astronomical inertial frames, and for the effect of Earths rotation, which provides a characteristic changing signature for narrow-band signals of extraterrestrial origin. Among the 2 × 1013spectral channels analyzed, 29 extra-statistical narrow-band events were found, exceeding the average threshold of 1.7 × 10−23Wm−2. The strongest signals that survive culling for terrestrial interference lie in or near the galactic plane. A description of the project META II observing scheme and results is made as well as the possible interpretation of the results using the Cordes-Lazio-Sagan model based in interstellar scattering theory.

Asteroid and Comet Impact Speeds upon Mars: Significance for Panspermia and the Supply of Organics

1997 ◽  
Vol 161 ◽  
pp. 197-201 ◽  
Author(s):  
Duncan Steel
Keyword(s):  
Probability Distributions ◽  
Regions Of Interest ◽  
Significant Fraction ◽  
Organic Chemicals ◽  
Impact Speed ◽  
The Mean ◽  
The Impact

AbstractWhilst lithopanspermia depends upon massive impacts occurring at a speed above some limit, the intact delivery of organic chemicals or other volatiles to a planet requires the impact speed to be below some other limit such that a significant fraction of that material escapes destruction. Thus the two opposite ends of the impact speed distributions are the regions of interest in the bioastronomical context, whereas much modelling work on impacts delivers, or makes use of, only the mean speed. Here the probability distributions of impact speeds upon Mars are calculated for (i) the orbital distribution of known asteroids; and (ii) the expected distribution of near-parabolic cometary orbits. It is found that cometary impacts are far more likely to eject rocks from Mars (over 99 percent of the cometary impacts are at speeds above 20 km/sec, but at most 5 percent of the asteroidal impacts); paradoxically, the objects impacting at speeds low enough to make organic/volatile survival possible (the asteroids) are those which are depleted in such species.

Dynamical Scattering in Electron Diffraction of wet Protein Crystals

1980 ◽  
Vol 38 ◽  
pp. 42-43
Author(s):  
B. B. Chang ◽  
D. F. Parsons
Keyword(s):  
Electron Diffraction ◽  
Scattering Theory ◽  
Protein Crystals ◽  
Electron Diffraction Data ◽  
Specimen Thickness ◽  
Major Question ◽  
X Ray ◽  
Scattering Effects ◽  
Diffraction Patterns ◽  
Acceleration Voltage

The significance of dynamical scattering effects remains the major question in the structural analysis by electron diffraction of protein crystals preserved in the hydrated state. In the few cases (single layers of purple membrane and 400-600 Å thick catalase crystals examined at 100 kV acceleration voltage) where electron-diffraction patterns were used quantitatively, dynamical scattering effects were considered unimportant on the basis of a comparison with x-ray intensities. The kinematical treatment is usually justified by the thinness of the crystal. A theoretical investigation by Ho et al. using Cowley-Moodie multislice formulation of dynamical scattering theory and cytochrome b5as the test object2 suggests that kinematical analysis of electron diffraction data with 100-keV electrons would not likely be valid for specimen thickness of 300 Å or more. We have chosen to work with electron diffraction patterns obtained from actual wet protein crystals (rat hemoglobin crystals of thickness range 1000 to 2500 Å) at 200 and 1000 kV and to analyze these for dynamical effects.

A Light Scattering Theory for Filled Diluted Polymer Solution under Flow

1995 ◽  
Vol 5 (7) ◽  
pp. 1017-1033 ◽  
Author(s):  
S. A. Patlazhan ◽  
P. Navard
Keyword(s):  
Light Scattering ◽  
Polymer Solution ◽  
Scattering Theory

SYNTHESIS AND CYTOTOXICITY OF POLYHYDROXYLATED CHOLESTEROL DERIVATIVES

2018 ◽  
Vol 56 (4) ◽  
pp. 467
Author(s):  
Thu Thuy Thi Tran ◽  
Ha Thi Dinh ◽  
Phương Lan Doan ◽  
Long Quoc Pham ◽  
Quang Dai Ngo
Keyword(s):  
Hepatocellular Carcinoma ◽  
Cell Line ◽  
Cell Lines ◽  
Carcinoma Cell ◽  
Addition Compound ◽  
Hep G2 ◽  
Physical Methods ◽  
Hepatocellular Carcinoma Cell Line ◽  
Human Hepatocellular Carcinoma Cell ◽  
Hepatocellular Carcinoma Cell

Eight polyhydroxylated cholesterol derivatives (1-8) were prepared from cholesterol, using oxidative reagents as SeO2, OsO4/NMO, HCOOH/H2O2 and BH3/ H2O2. Their structures were elucidated by using physical methods including NMR 1D and 2D. These compounds were evaluated against two cancer cell lines (Hep-G2, T98). Compounds 2, 4 and 8 inhibits human hepatocellular carcinoma cell line (Hep-G2) with IC50 4.69, 4.98 and 2.89 µg/mL, respectively. In addition, compound 8 exhibited strong cytotoxicity against T98 cell line (glioblastoma) with IC50 = 2.28 μM.

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