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Polarized Small Angle Neutron Scattering (SANS) is a powerful tool for studying mesoscale magnetic structures. In a recent development at the Oak Ridge National Laboratory (ORNL), a polarized neutron beam has been implemented for ...
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Polarized Small Angle Neutron Scattering (SANS) is a powerful tool for studying mesoscale magnetic structures. In a recent development at the Oak Ridge National Laboratory (ORNL), a polarized neutron beam has been implemented for the CG-2 (GP-SANS) beamline at the High Flux Isotope Reactor (HFIR). Three major components were developed to provide the polarized neutron capability: a transmission supermirror neutron polarizer, an adiabatic fast passage neutron spin flipper and a polarized He-3 filter as neutron spin analyzer. The new polarized beam SANS capability was used to investigate several magnetic samples having mesoscale structures.
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We describe a monochromatic SESANS option with four inclined soft ferromagnetic foils. The polarization is drawn toward the normal of the foils by a local longitudinal field. (C) 2003 Elsevier Science B.V. All rights reserved. [References: 6]
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We have developed a magnetic neutron lens (MNL) based on an extended Halbach-type permanent sextupole magnet. The effective aperture size is 30 mm in diameter and the length is 2400 mm. The sextupole magnetic field distribution ve...
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We have developed a magnetic neutron lens (MNL) based on an extended Halbach-type permanent sextupole magnet. The effective aperture size is 30 mm in diameter and the length is 2400 mm. The sextupole magnetic field distribution vertical bar B vertical bar = (G/2) r(2) with the gradient coefficient G = 10,660 +/- 530 T/m(2) are generated inside the magnet, where r is the distance from the magnet center axis. The neutron-focusing property is investigated by using pulsed polarized neutrons. The obtained results are discussed in comparison with numerical simulation results. The application to the focusing-geometry small-angle neutron scattering experiments is discussed. (c) 2006 Elsevier B.V. All rights reserved.
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A new series of Cobalt ferrofluids with remarkable air stability have been prepared by subsequent smooth oxidation. We report on polarised small-angle neutron scattering (SANSPOL) investigations of the unknown nuclear and magnetic...
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A new series of Cobalt ferrofluids with remarkable air stability have been prepared by subsequent smooth oxidation. We report on polarised small-angle neutron scattering (SANSPOL) investigations of the unknown nuclear and magnetic nanostructures. In order to evaluate the effect of the smooth oxidation step, beneficial for the air stability we compared the results with measurements on cobalt ferrofluids prepared similarly but without this step. SANSPOL combined with isotope contrast variation using deuterated solvents revealed a ferromagnetic core stabilized by a non-magnetic shell of organic surfactants. Only in the smoothly oxidised samples we found an additional non-magnetic layer on the surface of cobalt, the scattering length density of which corresponds closely to that of Co-oxides. (c) 2006 Published by Elsevier B.V.
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Classical Larmor precession (LP) of neutron polarization is considered as a result of the quantum interference between neutron spin states split in the magnetic field due to the Zeeman effect. The interference takes place if polar...
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Classical Larmor precession (LP) of neutron polarization is considered as a result of the quantum interference between neutron spin states split in the magnetic field due to the Zeeman effect. The interference takes place if polarization is not collinear with the direction of the magnetic induction. At grazing incidence onto a magnetized film LP may occur not only in transmission through but also at reflection from the film. If the magnetic reflection potential of the film is much lower than that of the substrate then the interference between spin components of neutron wave results in anomalous LP with doubled LP phase shift. At reflection from a film whose magnetic potential is comparable with the nuclear one and with that of the substrate both spin components are totally reflected, but with a phase shift resulting in the Larmor pseudo-precession (LPP) of the neutron polarization vector. The LPP period is proportional, in contrast to LP, to the neutron wave vector component normal to the film. A Pilot experiment on a 57 Fe film deposited on sapphire substrate shows that one precession can be achieved for the film thickness of similar to100 nm. (C) 2004 Elsevier B.V. All rights reserved.
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Concentrated surfactant stabilized cobalt ferrofluids up to 6 vol % Co have been studied by small-angle scattering using polarized neutrons and synchrotron x rays. The combination of these techniques allowed the magnetic and nucle...
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Concentrated surfactant stabilized cobalt ferrofluids up to 6 vol % Co have been studied by small-angle scattering using polarized neutrons and synchrotron x rays. The combination of these techniques allowed the magnetic and nuclear form factors to be reliably separated from the structure factors. Above 1 vol % Co, inter particle interactions are induced by an applied external magnetic field that gives rise to pseudocrystalline ordering of cobalt core-shell particles. Particles are arranged in hexagonal planes, with the magnetic moments aligned parallel to the [110] direction. Two types of equivalent textures were found to be present simultaneously, corresponding to a stacking of the hexagonal planes in horizontal and vertical direction. The in-plane nearest-neighbor distance is almost independent of the concentration and temperatures, whereas the distance between the neighboring planes, c, strongly varies from sample to sample. In addition, segments of chains of particles with parallel moments are aligned along the magnetic field and frozen-in when the carrier liquid is solidified. The field induced pseudocrystalline lamellar hexagonal particle arrangement, observed experimentally in colloidal magnetic liquids, confirms predictions from molecular-dynamics and Monte Carlo simulations. [References: 39]
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An X-band radar system was deployed in Santa Clara, CA from February through May 2016 to support the National Weather Service in the event of potential flooding during one of the largest E1 Ninos on record and to provide a better ...
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An X-band radar system was deployed in Santa Clara, CA from February through May 2016 to support the National Weather Service in the event of potential flooding during one of the largest E1 Ninos on record and to provide a better understanding of rainfall processes occurring in the Bay Area. The system was also used to provide high-quality precipitation estimation (quantitative precipitation estimation-QPE) for Santa Clara's urban hydrologic modeling system. Although the Bay Area has coverage from the Next-Generation Weather Radar (NEXRAD) operational radar network, the combination of topographic influences and proximity to a maritime environment provide unique QPE challenges in this urban region. The X-band radar provided high-quality rainfall estimates that performed better than NEXRAD, demonstrating the added value of the X-band system. High-resolution rainfall monitoring systems in urban regions also provide a host of benefits across different sectors of the economy, including flood damage mitigation, water quality, water supply, and transportation.
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? 2022 Elsevier B.V.Data on aggregation/morphological behaviour of contrasting charge aqueous gemini mixtures at 303 K have been acquired in this study. Anionic and cationic components of the mixture were phosphoric acid, P, P' ?1...
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? 2022 Elsevier B.V.Data on aggregation/morphological behaviour of contrasting charge aqueous gemini mixtures at 303 K have been acquired in this study. Anionic and cationic components of the mixture were phosphoric acid, P, P' ?1,4-butanedieyl, P, P' didodecylester, disodium salt (12–4-12A) and (ethane-1,2-diyl bis (N, N-dimethyl-N-alkylammoniumacetoamide) dichloride) (12-Eda-12 or 14-Eda-14), respectively. Fluorescence data are used to acquire critical micelle concentration (CMC) value and micro-environmental information (micro-polarity and dielectric constant). DLS, SANS and TEM confirm the presence of ellipsoidal, rod-shaped or vesicles at different compositions of the mixture(s). Further, zeta-potential (ζ) data reveal the charge reversal on the aggregate by mole fraction (x) variation (0–1) of the mixture. Solubilization of an anti-cancer drug (raloxifene hydrochloride, RLX) has been seen in various morphologies (spectrophotometrically) and it has been found that vesicles (formed at x = 0.4 or 0.6) solubilize more RLX than the any other morphology. RLX release profile follows Higuchi model which confirms the diffusional release mechanism. RLX solubilised in 12–4-12A + 14-Eda-14 mixture (x = 0.6 and x = 0.4, respectively) showed good cell proliferation behaviour (9.06 μg/mL) over pure RLX (21.75 μg/mL) towards MCF-7.
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At the NIST Center for Neutron Research (NCNR), we have applied He-3 neutron spin filters (NSFs) to the instruments where He-3 NSFs are advantageous, such as thermal triple-axis spectrometry, small-angle neutron scattering, and di...
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At the NIST Center for Neutron Research (NCNR), we have applied He-3 neutron spin filters (NSFs) to the instruments where He-3 NSFs are advantageous, such as thermal triple-axis spectrometry, small-angle neutron scattering, and diffuse reflectometry. We present the status of our development and application of this method, including polarized gas production by spin-exchange optical pumping, magnetostatic cavities for storage of the polarized gas on the beam line, and nuclear magnetic resonance (NMR)-based, on-line monitoring and reversal of the He-3 polarization. We present the status of developing user-friendly interfaces incorporated into the instrument software to handle these He-3 neutron spin filters while taking data and performing data analysis. Finally we discuss the status of development of a polarization capability on the multi-axis crystal spectrometer, which requires polarization analysis over a 220 degrees angular range.
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The reaction product EPDM-g-SAN, synthesized by suspension graft copolymerization of styrene (St) and acrylonitrile (AN) in the presence of ethylene-propylene-diene terpolymer (EPDM), was blended with a commercial styrene-acryloni...
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The reaction product EPDM-g-SAN, synthesized by suspension graft copolymerization of styrene (St) and acrylonitrile (AN) in the presence of ethylene-propylene-diene terpolymer (EPDM), was blended with a commercial styrene-acrylonitrile copolymer (SAN resin) to prepare AES blends with high impact strength. The effects of AN mass percentage in the St-AN comonomer mixture (f_(AN)), EPDM mass percentage in the feed of EPDM and St-AN (fEPDM) and reaction time on monomer conversion ratio (CR), grafting ratio (GR), and AES notched Izod impact strength were characterized. The notched Izod impact strength of AES containing 15 wt% EPDM reached its maximum with f_(AN) of 40 wt% and f_(EPDM) of 45 wt%; this was attributed to the polarity of the SAN copolymer obtained being appropriate with that of the SAN resin matrix. The dependences of GR and the notched Izod impact strength of AES containing 25 wt% EPDM on the reaction time were in rough agreement. The effect of EPDM content on the AES notched Izod impact strength indicated that the brittle-ductile transition of AES occurred for an EPDM content from 12.5 to 15 wt%. TEM and SEM analysis showed that the phase structure of AES exhibited a "salami" like structure, and the toughening mechanism of AES was shear yielding of the SAN resin matrix, which endowed AES with excellent toughness.
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