Small angle scattering in the Porod region from hydrated paper sheets at varying humidities

Holzforschung ◽  
2004 ◽  
Vol 58 (5) ◽  
pp. 473-479 ◽  
Author(s):  
Christopher J. Garvey ◽  
Ian H. Parker ◽  
Robert B. Knott ◽  
George P. Simon
Keyword(s):  
Small Angle ◽  
Scattering Length ◽  
Phase System ◽  
Phase Approximation ◽  
Contrast Variation ◽  
Two Phase ◽  
Scattering Angle ◽  
Angle Scattering ◽  
Porod Law ◽  
Two Phases

Abstract The microscopic changes in the structure of paper at different equilibrium moisture contents were examined using the novel technique of contrast variation small angle neutron scattering (SANS). Contrast variation, by appropriate selection of the H2O:D2O ratio, was used to simplify the scattering from hydrated paper to a two-phase approximation. The two phases were paper polymers (cellulose, lignin and hemicelluloses) and a phase consisting of water and voids. The two-phase approximation is justified by consideration of the chemistry and density of each of the polymer species belonging to paper, and by matching the scattering length density of the sorbed moisture to air. The neutron intensity at the higher scattering angles examined was successfully fitted using the Porod law, which is applicable to scattering from a two-phase system at the high scattering angle limit. This limit is related to the specific surface area between the two phases. The limiting scattered intensity of neutrons was found to increase with increasing moisture content for a range of paper materials. It is concluded that the sorption of water increased the limiting intensity because water disrupted polymer-polymer bonding. The Porod law also predicts the slope of the intensity/scattering angle curve at the high scattering angle limit.

Multiphase approximation for small-angle scattering

2009 ◽  
Vol 43 (1) ◽  
pp. 8-11 ◽  
Author(s):  
Dragomir Tatchev
Keyword(s):  
Small Angle ◽  
Small Angle Scattering ◽  
Multiphase System ◽  
Contrast Variation ◽  
Two Phase ◽  
Angle Scattering ◽  
Multiphase Systems ◽  
Phase Systems ◽  
The Difference ◽  
Two Phases

The two-phase approximation in small-angle scattering is well known and is still the dominant approach to data analysis. The intensity scattered at small angles is proportional to the second power of the difference between the scattering densities of the two phases. Nevertheless, scattering contrast variation techniques are widely used, and they are obviously suitable for multiphase systems or systems with gradually varying scattering density, since if no parasitic scattering contributions are present the scattering contrast variation would only change a proportionality coefficient. It is shown here that the scattered intensity at small angles of a multiphase system can be represented as a sum of the scattering of two-phase systems and terms describing interference between all pairs of phases. Extracting two-phase scattering patterns from multiphase samples by contrast variation is possible. These two-phase patterns can be treated with the usual small-angle scattering formalism. The case of gradually varying scattering density is also discussed.

Contrast variation in small-angle scattering experiments on polydisperse and superparamagnetic systems: basic functions approach

2007 ◽  
Vol 40 (1) ◽  
pp. 56-70 ◽  
Author(s):  
Mikhail V. Avdeev
Keyword(s):  
Small Angle ◽  
Magnetic Particles ◽  
Scattering Length ◽  
Small Angle Scattering ◽  
Contrast Variation ◽  
Match Point ◽  
Scattering Intensity ◽  
Scattering Length Density ◽  
Angle Scattering ◽  
Basic Functions

The development of the basic functions approach [Stuhrmann (1995).Modern Aspects of Small-Angle Scattering, edited by H. Brumberger, pp. 221–254. Dordrecht: Kluwer Academic Publishers] for the contrast variation technique in small-angle scattering from systems of polydisperse and superparamagnetic non-interacting particles is presented. For polydisperse systems the modified contrast is introduced as the difference between the effective mean scattering length density (corresponding to the minimum of the scattering intensity as the function of the scattering length density of the solvent) and the density of the solvent. Then, the general expression for the scattering intensity is written in the classical way through the modified basic functions. It is shown that the shape scattering from the particle volume can be reliably obtained. Modifications of classical expressions describing changes in integral parameters of the scattering (intensity at zero angle, radius of gyration, Porod integral) with the contrast are analyzed. In comparison with the monodisperse case, the residual scattering in the minimum of intensity as a function of contrast (effective match point) in polydisperse systems makes it possible to treat the Guinier region of scattering curves around the effective match point quite precisely from the statistical viewpoint. However, limitations of such treatment exist, which are emphasized in the paper. In addition, the effect of magnetic scattering in small-angle neutron scattering from superparamagnetic nanoparticles is considered in the context of the basic functions approach. Conceptually, modifications of the integral parameters of the scattering in this case are similar to those obtained for polydisperse multicomponent particles. Various cases are considered, including monodisperse non-homogeneous and homogeneous magnetic particles, and polydisperse non-homogeneous and homogeneous magnetic particles. The developed approach is verified for two models representing the main types of magnetic fluids – systems of polydisperse superparamagnetic particles located in liquid carriers.

scholarly journals Small-angle scattering from multiphase fractals

2014 ◽  
Vol 47 (1) ◽  
pp. 198-206 ◽  
Author(s):  
A. Yu. Cherny ◽  
E. M. Anitas ◽  
V. A. Osipov ◽  
A. I. Kuklin
Keyword(s):  
Power Law ◽  
Small Angle ◽  
Small Angle Scattering ◽  
Variation Method ◽  
Multiphase System ◽  
Model Parameters ◽  
Contrast Variation ◽  
Crossover Point ◽  
Two Phase ◽  
Angle Scattering

Small-angle scattering (SAS) intensities observed experimentally are often characterized by the presence of successive power-law regimes with various scattering exponents whose values vary from −4 to −1. This usually indicates multiple fractal structures of the sample characterized by different size scales. The existing models explaining the crossover positions (that is, the points where the power-law scattering exponent changes) involve only one contrast parameter, which depends solely on the ratio of the fractal sizes. Here, a model that describes SAS from a multiphase system with a few contrast parameters is described, and it is shown that the crossover position depends on the scattering length density of each phase. The Stuhrmann contrast variation method is generalized and applied to experimental curves in the vicinity of the crossover point beyond the Guinier region. The contrast variation is applied not to the intensity itself but to the model parameters, which can be found by fitting the experimental data with the suggested interpolation formula. The model supplements the existing two-phase models and gives the simple condition of their inapplicability: if the crossover point depends on the contrast then a two-phase model is not relevant. The developed analysis allows one to answer the qualitative question of whether one fractal `absorbs' another one or they are both immersed in a surrounding homogeneous medium like a solvent or solid matrix. The models can be applied to experimental SAS data where the absolute value of the scattering exponent of the first power-law regime is higher than that of the subsequent second power-law regime, that is, the scattering curve is `convex' near the crossover point. As is shown, the crossover position can be very sensitive to contrast variation, which influences significantly the length of the fractal range.

Small-angle scattering contrast calculator for protein and nucleic acid complexes in solution

2013 ◽  
Vol 46 (6) ◽  
pp. 1889-1893 ◽  
Author(s):  
Kathryn L. Sarachan ◽  
Joseph E. Curtis ◽  
Susan Krueger
Keyword(s):  
Nucleic Acid ◽  
Small Angle ◽  
Scattering Length ◽  
Software Tool ◽  
Scattering Data ◽  
Atomistic Modeling ◽  
Contrast Variation ◽  
X Ray ◽  
X Ray Scattering ◽  
Angle Scattering

Small-angle neutron scattering (SANS) with contrast variation can provide useful information about the structure and disposition of two or more chemically distinct components within a complex. TheSASSIE Contrast Calculator(SCC) is a new software tool designed to assist in planning SANS experiments with contrast variation on protein and nucleic acid complexes. On the basis of the primary sequence and deuteration level of each protein or nucleic acid component, theSCCcalculates and plotsI(0), contrast and scattering length densities; since SANS experiments often complement small-angle X-ray scattering studies, the program provides both neutron and X-ray parameters. TheSCCis run as an integrated component ofSASSIE[Curtis, Raghunandan, Nanda & Krueger (2012).Comput. Phys. Commun.183, 382–389], a software suite for atomistic modeling of ensembles of structures consistent with scattering data.

Supercritical carbon dioxide behavior in porous silica aerogel

2010 ◽  
Vol 44 (1) ◽  
pp. 43-51 ◽  
Author(s):  
Salvino Ciccariello ◽  
Yuri B. Melnichenko ◽  
Lilin He
Keyword(s):  
Carbon Dioxide ◽  
Low Temperature ◽  
Small Angle ◽  
Silica Aerogel ◽  
Small Angle Neutron Scattering ◽  
Scattering Length ◽  
Porous Silica ◽  
Phase System ◽  
Two Phase ◽  
Silica Wall

Analysis of the tails of the small-angle neutron scattering (SANS) intensities relevant to samples formed by porous silica and carbon dioxide at pressures ranging from 0 to 20 MPa and at temperatures of 308 and 353 K confirms that the CO2fluid must be treated as a two-phase system. The first of these phases is formed by the fluid closer to the silica wall than a suitable distance δ and the second by the fluid external to this shell. The sample scattering-length densities and shell thicknesses are determined by the Porod invariants and the oscillations observed in the Porod plots of the SANS intensities. The resulting matter densities of the shell regions (thickness 15–35 Å) are approximately equal, while those of the outer regions increase with pressure and become equal to the bulk CO2at the higher pressures only in the low-temperature case.

A new time-of-flight small-angle scattering instrument at the Helmholtz-Zentrum Berlin: V16/VSANS

2014 ◽  
Vol 47 (1) ◽  
pp. 237-244 ◽  
Author(s):  
Karsten Vogtt ◽  
Miriam Siebenbürger ◽  
Daniel Clemens ◽  
Christian Rabe ◽  
Peter Lindner ◽  
...  
Keyword(s):  
Momentum Transfer ◽  
Small Angle ◽  
Soft Matter ◽  
Scattering Length ◽  
Time Of Flight ◽  
Small Angle Scattering ◽  
Neutron Guide ◽  
Macromolecular Assemblies ◽  
Angle Scattering ◽  
The Individual

Small-angle scattering methods have become routine techniques for the structural characterization of macromolecules and macromolecular assemblies like polymers, (block) copolymers or micelles in the spatial range from a few to hundreds of nanometres. Neutrons are valuable scattering probes, because they offer freedom with respect to scattering length density contrast and isotopic labelling of samples. In order to gain maximum benefit from the allotted experiment time, the instrumental setup must be optimized in terms of statistics of scattered intensity, resolution and accessible range in momentum transferQ. The new small-angle neutron scattering instrument V16/VSANS at the Helmholtz-Zentrum in Berlin, Germany, augments neutron guide collimation and pinhole optics with time-of-flight data recording and flexible chopper configuration. Thus, the availableQrange and the respective instrumental resolution in the intermediate and high momentum transfer regions can be adjusted and balanced to the individual experimental requirements. This renders V16/VSANS a flexible and versatile instrument for soft-matter research.

Activity coefficients, densities, dipole moments, and surface tensions of the system triethylamine–methylethylketone–water

1981 ◽  
Vol 59 (1) ◽  
pp. 127-131 ◽  
Author(s):  
Alan N. Campbell
Keyword(s):  
Surface Layer ◽  
Dipole Moments ◽  
Phase System ◽  
Constant Composition ◽  
Two Phase ◽  
Three Phase ◽  
Wide Range ◽  
Isothermal System ◽  
Total Composition ◽  
Two Phases

The properties named in the title have been determined by standard methods. Viscosity, molar volume, and orientation polarisation all indicate abnormalities of the nature of association between the components.The most interesting result is that of surface tension which indicates that, in the case of the binary system triethylamine–water, a surface layer of constant composition is formed over a wide range of total composition. When, by a rise in temperature of two or three degrees, this layer becomes unstable, it splits into two phases of different composition. The surface layer may then be instantaneously reformed and so on. A mechanism for the generation of a two-phase system is thus established. The data for the three-phase, isothermal, system are not so convincing, for reasons that are suggested.

SMALL-ANGLE SCATTERING OF FAST POLARIZED NEUTRONS BY HEAVY NUCLEI

1956 ◽  
Vol 34 (1) ◽  
pp. 36-42 ◽  
Author(s):  
J. T. Sample
Keyword(s):  
Small Angle ◽  
Intensity Ratio ◽  
Horizontal Plane ◽  
Small Angle Scattering ◽  
Fast Neutrons ◽  
Heavy Nuclei ◽  
Spin Orientation ◽  
Scattering Angle ◽  
Angle Scattering ◽  
The Right

Detailed calculations have been carried out which indicate that the small-angle scattering of fast neutrons by lead depends on the polarization, or spin orientation, of the neutrons. When the scattering of neutrons whose spin vectors point upward is observed in the horizontal plane, more neutrons should be found scattered to the right than to the left. For completely polarized 3.1 Mev. neutrons, the theory predicts a maximum "right to left" intensity ratio of 14.5:1 at a scattering angle of 0.5°, the ratio decreasing to 1.6:1 at 5°, and approaching unity rapidly as the scattering angle increases.

Robotic Hardware and Software Integration for Changing Human Intentions

2012 ◽  
pp. 380-406 ◽  
Author(s):  
Akif Durdu ◽  
Ismet Erkmen ◽  
Aydan M. Erkmen ◽  
Alper Yilmaz
Keyword(s):  
Video Processing ◽  
Spatial Information ◽  
Human Robot Interaction ◽  
Phase System ◽  
Robot Interaction ◽  
Two Phase ◽  
Video Frames ◽  
Human Intention ◽  
Two Phases ◽  
Intention Estimation

Estimating and reshaping human intentions are among the most significant topics of research in the field of human-robot interaction. This chapter provides an overview of intention estimation literature on human-robot interaction, and introduces an approach on how robots can voluntarily reshape estimated intentions. The reshaping of the human intention is achieved by the robots moving in certain directions that have been a priori observed from the interactions of humans with the objects in the scene. Being among the only few studies on intention reshaping, the authors of this chapter exploit spatial information by learning a Hidden Markov Model (HMM) of motion, which is tailored for intelligent robotic interaction. The algorithmic design consists of two phases. At first, the approach detects and tracks human to estimate the current intention. Later, this information is used by autonomous robots that interact with detected human to change the estimated intention. In the tracking and intention estimation phase, postures and locations of the human are monitored by applying low-level video processing methods. In the latter phase, learned HMM models are used to reshape the estimated human intention. This two-phase system is tested on video frames taken from a real human-robot environment. The results obtained using the proposed approach shows promising performance in reshaping of detected intentions.

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