Analysis of Small Angle Scattering Data by Model Fitting

Small angle scattering is a common technique for investigating fluctuations in materials, for sizes ranging from about ten to a few hundred Angstroms. The technique could be more widely used if data analysis were more convenient; however, expressions relating the small angle scattered intensity to materials parameters of interest tend to be complicated. Non-linear regression fitting of experimental small angle scattering data from metallurgical systems is discussed, and the analysis procedure is demonstrated for two models on data from a Ni-Si alloy undergoing phase separation. It is concluded that if sufficient information is available to permit the proper model to be identified, quantitative values for the relevant materials parameters can be extracted in a rather routine manner, provided the parameters are not too closely coupled

Analysis of a Drum Chopper for Use on a New Small Angle Diffractometer at IPNS

Light-weight drum choppers rotating at 15 Hz have been in use on the IPNS powder diffractometers for several years, where they serve to eliminate the delayed-neutron background from much of the spectral region of interest. Monte Carlo simulations indicate that a similar chopper operated at 15 Hz should do an excellent job of delayed-neutron removal in the new small-angle diffractometer being designed at IPNS. The simulations also show that when the same chopper is operated at 7.5 Hz it performs quite successfully as a frame-elimination chopper, effectively eliminating neutrons from alternate pulses and allowing extension of the useful wavelength range of the instrument to {approximately}28 {Angstrom}. Thus the incorporation of such a chopper should add considerably to the range and flexibility of the new instrument. 7 refs., 9 figs

Effects of nematicides on nematode population densities and crop yield in a turnip-corn-pea cropping system

Nous avons évalué quatre systèmes de conduite de cultures lors d'une étude de 6 ans afin de lutter contre les nematodes dans un système annuel de production de navet-maïs-pois sur des parcelles de sable loameux Tifton naturellement infestées par les Meloidogyne spp. (environ 90 % de M. incognita et 10 % de M. hapla), les Pratylenchus spp. (environ 65 % de P. scribneri, 25 % de P. brachyurus et 10 % de P. zeae), ainsi que par les Paratrichodorus minor et Criconemella ornata. Le navet (Brassica campestris subsp. rapifera) a toléré de faibles quantités de tous les nematodes. Le maïs (Zea mays) 'Pioneer 3369A' a toléré de plus importantes quantités de tous les nematodes que le maïs 'Funks G-4507'. Les densités de population de juvéniles (J2) de Meloidogyne spp. ont été abaissées en deçà de 80 par 150 cm3 de sol par un mélange composé de 98 % de bromure de méthyle et 2 % de chloropicrine et par 20% de methyl isothiocyanate combiné à 80% d'hydrocarbones C3 chlorinés sur le navet et le maïs. Ces populations de nematodes ont augmenté rapidement chez le pois (Vigna unguiculata) 'Pinkeye purplehull' mais ce ne fut pas le cas chez le cultivar Worthmore. Les densités de populations des autres nematodes n'ont pas été affectées par le cultivar de pois ou par le nématicide, en l'occurrence l'ethoprop. Le fenamiphos a été plus efficace que l'ethoprop en abaissant les densités de nematodes. Les augmentations de rendement du système intensif de conduite des cultures se sont échelonnées de 4% à 52 % par rapport aux témoins non traités.Four management systems were evaluated in a six-year study to control nematodes in a turnip-corn-pea annual cropping System on plots of Tifton loamy sand naturally infested with Meloidogyne spp. (about 90 % M. incognita and 10% M. hapla), Pratylenchus spp. (about 65% P. scribneri, 25% P. brachyurus, and 10% P. zeae), Paratrichodorus minor and Criconemella ornata. Turnip (Brassica campestris subsp. rapifera) supported low numbers of all nematodes. 'Pioneer 3369A' corn (Zea mays) supported greater numbers of all nematodes than 'Funks G-4507'. Population densities of Meloidogyne spp. juveniles (J2) were suppressed below 80 per 150 cm3 of soil by 98 % methyl bromide + 2 % chloropicrin and 20 % methyl isothiocyanate + 80 % chlorinated C3 hydrocarbons on turnip and corn, and increased rapidly on 'Pinkeye purplehull', but not on a resistant cultivar, 'Worthmore' pea (Vigna unguiculata). Population densities of other nematodes were not affected by cultivar of pea or the nematicide, ethoprop. Fenamiphos was more effective than ethoprop in suppressing nematode population densities. Increases in crop yield in the intensive management system ranged from 4% to 52% over untreated controls

Sans measurement of deuterium trapping at dislocations and grain boundaries in palladium

Small angle neutron scattering (SANS) measurements have been made on deformed single crystal and polycrystalline palladium with and without deuterium dissolved in the solution phase at room temperature. The net scattering cross section for the same sample with and without deuterium loading shows a behavior expected from deuterium correlation with dislocations forming rod-like scattering structures. We conclude from these scattering measurements that the trapped deuterium is within 2-3 Burgers vectors of the dislocation core. On average 1-3 deuterons per A are trapped at dislocations in the deformed samples. The measurements indicate the straight, rod-like correlation geometry extends on average 50-100 A along the dislocations. Net scattering from a well annealed polycrystalline palladium sample exhibiting a behavior expected from surfaces has been observed. This net scattering is attributed to deuterium trapped at grain boundaries in the polycrystalline sample. A value of 0.4 +/- 0.2 trapped deuterons per A2 of grain boundary area is calculated from the well annealed polycrystalline scattering measurement.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29076/1/0000111.pd

Observation of Scaling Violations in Scaled Momentum Distributions at HERA

Charged particle production has been measured in deep inelastic scattering (DIS) events over a large range of $x$ and $Q^2$ using the ZEUS detector. The evolution of the scaled momentum, $x_p$, with $Q^2,$ in the range 10 to 1280 $GeV^2$, has been investigated in the current fragmentation region of the Breit frame. The results show clear evidence, in a single experiment, for scaling violations in scaled momenta as a function of $Q^2$.Comment: 21 pages including 4 figures, to be published in Physics Letters B. Two references adde

An Examination of the Market Structure of the U.S. Produce Industry

Recent literature, largely from the U.S. Department of Agriculture Economic Research Service, indicates that substantial changes have occurred in the produce industry in recent years. With the rise of retail mass merchandisers and increased concentration in the retail food industry, the procurement power of these large firms reportedly has also increased. With direct buying and contracting, market intermediaries such as brokers and wholesalers allegedly are being bypassed. As a result, these market intermediaries ostensibly are also consolidating, becoming fewer and larger with increased emphasis on servicing the food-service industry. However, the findings of this study indicate that there is no convinc­ ing evidence that the market structure of the U.S. produce industry has markedly changed since the early 1980s. While supermarket concentration has increased noticeably, the same cannot be said for produce market intermediaries such as brokers and wholesalers

Small Angle Neutron Scattering From Nanometer Grain Sized Materials

Small angie neutron scattering has been utilized, along with a number of complementary characterization methods suitable to the nanometer size scale, to investigate the structures of cluster-assembled nanophase materials. Results of these investigations are described and problems and opportunities in using small angle scattering for elucidating nanostructures are discussed

Anomalous and Resonance Small Angle Scattering: Revision

Significant changes in the small angle scattered intensity can be induced by making measurements with radiation close to an absorption edge of an appropriate atomic species contained in the sample. These changes can be related quantitatively to the real and imaginary anomalous dispersion terms for the scattering factor (x-rays) or scattering length (neutrons). The physics inherent in these anomalous dispersion terms is first discussed before considering how they enter the relevant scattering theory. Two major areas of anomalous scattering research have emerged; macromolecules in solution and unmixing of metallic alloys. Research in each area is reviewed, illustrating both the feasibility and potential of these techniques. All the experimental results reported to date have been obtained with x-rays. However, it is pointed out that the formalism is the same for the analogue experiment with neutrons, and a number of suitable isotopes exist which exhibit resonance in an accessible range of energy. Potential applications of resonance small angle neutron scatterings are discussed. 54 refs., 8 figs., 1 tab

Anomalous and resonance small angle scattering

Significant changes in the small angle scattered intensity can be induced by making measurements with radiation close to an absorption edge of an appropriate atomic species contained in the sample. These changes can be related quantitatively to the real and imaginary anomalous dispersion terms for the scattering factor (x-rays) or scattering length (neutrons). The physics inherent in these anomalous dispersion terms is first discussed before considering how they enter the relevant scattering theory. Two major areas of anomalous scattering research have emerged; macromolecules in solution and unmixing of metallic alloys. Research in each area is reviewed, illustrating both the feasibility and potential of these techniques. All the experimental results reported to date have been obtained with x-rays. However, it is pointed out that the formalism is the same or the analogue experiment with neutrons, and a number of suitable isotopes exist which exhibit resonance in an accessible range of energy. Potential applications of resonance small-angle neutron scatterings are discussed. 8 figs