Wavelength-independent constant period spin-echo modulated small angle neutron scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sales, Morten, E-mail: lsp260@alumni.ku.dk; Plomp, Jeroen; Bouwman, Wim

2016-06-15

Spin-Echo Modulated Small Angle Neutron Scattering (SEMSANS) in Time-of-Flight (ToF) mode has been shown to be a promising technique for measuring (very) small angle neutron scattering (SANS) signals and performing quantitative Dark-Field Imaging (DFI), i.e., SANS with 2D spatial resolution. However, the wavelength dependence of the modulation period in the ToF spin-echo mode has so far limited the useful modulation periods to those resolvable with the limited spatial resolution of the detectors available. Here we present our results of an approach to keep the period of the induced modulation constant for the wavelengths utilised in ToF. This is achieved bymore » ramping the magnetic fields in the coils responsible for creating the spatially modulated beam in synchronisation with the neutron pulse, thus keeping the modulation period constant for all wavelengths. Such a setup enables the decoupling of the spatial detector resolution from the resolution of the modulation period by the use of slits or gratings in analogy to the approach in grating-based neutron DFI.« less

Flow-through compression cell for small-angle and ultra-small-angle neutron scattering measurements

NASA Astrophysics Data System (ADS)

Hjelm, Rex P.; Taylor, Mark A.; Frash, Luke P.; Hawley, Marilyn E.; Ding, Mei; Xu, Hongwu; Barker, John; Olds, Daniel; Heath, Jason; Dewers, Thomas

2018-05-01

In situ measurements of geological materials under compression and with hydrostatic fluid pressure are important in understanding their behavior under field conditions, which in turn provides critical information for application-driven research. In particular, understanding the role of nano- to micro-scale porosity in the subsurface liquid and gas flow is critical for the high-fidelity characterization of the transport and more efficient extraction of the associated energy resources. In other applications, where parts are produced by the consolidation of powders by compression, the resulting porosity and crystallite orientation (texture) may affect its in-use characteristics. Small-angle neutron scattering (SANS) and ultra SANS are ideal probes for characterization of these porous structures over the nano to micro length scales. Here we show the design, realization, and performance of a novel neutron scattering sample environment, a specially designed compression cell, which provides compressive stress and hydrostatic pressures with effective stress up to 60 MPa, using the neutron beam to probe the effects of stress vectors parallel to the neutron beam. We demonstrate that the neutron optics is suitable for the experimental objectives and that the system is highly stable to the stress and pressure conditions of the measurements.

Small-angle neutron scattering study of the structure of mixed micellar solutions based on heptaethylene glycol monotetradecyl ether and cesium dodecyl sulfate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rajewska, A., E-mail: aldonar@jinr.ru; Medrzycka, K.; Hallmann, E.

2016-01-15

The micellization in mixed aqueous systems based on a nonionic surfactant, heptaethylene glycol monotetradecyl ether (C{sub 14}E{sub 7}), and an anionic surfactant, cesium dodecyl sulfate, has been investigated by small-angle neutron scattering. Preliminary data on the behavior of the C{sub 14}E{sub 7} aqueous solutions (with three concentrations, 0.17, 0.5, and 1%) mixed with a small amount of anionic surfactant, cesium dodecyl sulfate, are reported.

The Small-Angle Neutron Scattering Data Analysis of the Phospholipid Transport Nanosystem Structure

NASA Astrophysics Data System (ADS)

Zemlyanaya, E. V.; Kiselev, M. A.; Zhabitskaya, E. I.; Aksenov, V. L.; Ipatova, O. M.; Ivankov, O. I.

2018-05-01

The small-angle neutron scattering technique (SANS) is employed for investigation of structure of the phospholipid transport nanosystem (PTNS) elaborated in the V.N.Orekhovich Institute of Biomedical Chemistry (Moscow, Russia). The SANS spectra have been measured at the YuMO small-angle spectrometer of IBR-2 reactor (Joint Institute of Nuclear Research, Dubna, Russia). Basic characteristics of polydispersed population of PTNS unilamellar vesicles (average radius of vesicles, polydispersity, thickness of membrane, etc.) have been determined in three cases of the PTNS concentrations in D2O: 5%, 10%, and 25%. Numerical analysis is based on the separated form factors method (SFF). The results are discussed in comparison with the results of analysis of the small-angle X-ray scattering spectra collected at the Kurchatov Synchrotron Radiation Source of the National Research Center “Kurchatov Institute” (Moscow, Russia).

Structure of spontaneously formed solid-electrolyte interphase on lithiated graphite determined using small-angle neutron scattering

DOE PAGES

Sacci, Robert L.; Banuelos, Jose Leobardo; Veith, Gabriel M.; ...

2015-03-25

We report the first small-angle neutron scattering of a chemically formed solid-electrolyte interphase from LixC6 reacting with ethylene carbonate/dimethyl carbon solvent. This provides a different and perhaps simpler view of SEI formation than the usual electrochemically-driven reaction. We show that an organic layer coats the graphite particles filling in micro-pores and is polymeric in nature being 1-3 nm thick. We used inelastic neutron scattering to probe the chemistry, and we found that the SEI showed similar inelastic scattering to polyethylene oxide.

Study of High Temperature Failure Mechanisms in Ceramics

DTIC Science & Technology

1988-06-01

The major experimental 4 techniques employed in the program are the use of small- angle neutron scattering to characterize cavity nucleation and growth...creep crackgrowth. Of particular interest are the development of a stochastic model of grainboundary sliding and a micromechanical model that relates...Accession For NTIS GF.A&I DTIC T,’ IDi st ribut Ion’ ;i Avillii~diii l l= (~~ I. RESEARCH OBJECTIVES I. Utilize small- angle neutron scattering to

Structural studies of Neurospora crassa LPMO9D and redox partner CDHIIA using neutron crystallography and small-angle scattering.

PubMed

Bodenheimer, Annette M; O'Dell, William B; Stanley, Christopher B; Meilleur, Flora

2017-08-07

Sensitivity to hydrogen/deuterium and lack of observable radiation damage makes cold neutrons an ideal probe the structural studies of proteins with highly photosensitive groups such as the copper center of lytic polysaccharide monooxygenases (LPMOs) and flavin adenine dinucleotide (FAD) and heme redox cofactors of cellobiose dehydrogenases (CDHs). Here, neutron crystallography and small-angle neutron scattering are used to investigate Neurospora crassa LPMO9D (NcLPMO9D) and CDHIIA (NcCDHIIA), respectively. The presence of LPMO greatly enhances the efficiency of commercial glycoside hydrolase cocktails in the depolymerization of cellulose. LPMOs can receive electrons from CDHs to activate molecular dioxygen for the oxidation of cellulose resulting in chain cleavage and disruption of local crystallinity. Using neutron protein crystallography, the hydrogen/deuterium atoms of NcLPMO9D could be located throughout the structure. At the copper active site, the protonation states of the side chains of His1, His84, His157 and Tyr168, and the orientation of water molecules could be determined. Small-angle neutron scattering measurements provided low resolution models of NcCDHIIA with both the dehydrogenase and cytochrome domains in oxidized states that exhibited elongated conformations. This work demonstrates the suitability of neutron diffraction and scattering for characterizing enzymes critical to oxidative cellulose deconstruction. Copyright © 2017 Elsevier Ltd. All rights reserved.

Structural studies of Neurospora crassa LPMO9D and redox partner CDHIIA using neutron crystallography and small-angle scattering

DOE PAGES

Bodenheimer, Annette M.; O'Dell, William B.; Stanley, Christopher B.; ...

2017-03-04

Sensitivity to hydrogen/deuterium and lack of observable radiation damage makes cold neutrons an ideal probe the structural studies of proteins with highly photosensitive groups such as the copper center of lytic polysaccharide monooxygenases (LPMOs) and flavin adenine dinucleotide (FAD) and heme redox cofactors of cellobiose dehydrogenases (CDHs). In this paper, neutron crystallography and small-angle neutron scattering are used to investigate Neurospora crassa LPMO9D (NcLPMO9D) and CDHIIA (NcCDHIIA), respectively. The presence of LPMO greatly enhances the efficiency of commercial glycoside hydrolase cocktails in the depolymerization of cellulose. LPMOs can receive electrons from CDHs to activate molecular dioxygen for the oxidation ofmore » cellulose resulting in chain cleavage and disruption of local crystallinity. Using neutron protein crystallography, the hydrogen/deuterium atoms of NcLPMO9D could be located throughout the structure. At the copper active site, the protonation states of the side chains of His1, His84, His157 and Tyr168, and the orientation of water molecules could be determined. Small-angle neutron scattering measurements provided low resolution models of NcCDHIIA with both the dehydrogenase and cytochrome domains in oxidized states that exhibited elongated conformations. Finally, this work demonstrates the suitability of neutron diffraction and scattering for characterizing enzymes critical to oxidative cellulose deconstruction.« less

Structural studies of Neurospora crassa LPMO9D and redox partner CDHIIA using neutron crystallography and small-angle scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bodenheimer, Annette M.; O'Dell, William B.; Stanley, Christopher B.

Sensitivity to hydrogen/deuterium and lack of observable radiation damage makes cold neutrons an ideal probe the structural studies of proteins with highly photosensitive groups such as the copper center of lytic polysaccharide monooxygenases (LPMOs) and flavin adenine dinucleotide (FAD) and heme redox cofactors of cellobiose dehydrogenases (CDHs). In this paper, neutron crystallography and small-angle neutron scattering are used to investigate Neurospora crassa LPMO9D (NcLPMO9D) and CDHIIA (NcCDHIIA), respectively. The presence of LPMO greatly enhances the efficiency of commercial glycoside hydrolase cocktails in the depolymerization of cellulose. LPMOs can receive electrons from CDHs to activate molecular dioxygen for the oxidation ofmore » cellulose resulting in chain cleavage and disruption of local crystallinity. Using neutron protein crystallography, the hydrogen/deuterium atoms of NcLPMO9D could be located throughout the structure. At the copper active site, the protonation states of the side chains of His1, His84, His157 and Tyr168, and the orientation of water molecules could be determined. Small-angle neutron scattering measurements provided low resolution models of NcCDHIIA with both the dehydrogenase and cytochrome domains in oxidized states that exhibited elongated conformations. Finally, this work demonstrates the suitability of neutron diffraction and scattering for characterizing enzymes critical to oxidative cellulose deconstruction.« less

Small Angle Neutron Scattering experiments on ``side-on fixed"" liquid crystal polyacrylates

NASA Astrophysics Data System (ADS)

Leroux, N.; Keller, P.; Achard, M. F.; Noirez, L.; Hardouin, F.

1993-08-01

Small Angle Neutron Scattering experiments were carried out on liquid crystalline “side-on fixed” polyacrylates : we observe that the polymer backbone adopts a prolate conformation in the nematic phase. Such anisotropy of the global backbone is larger for smaller spacer length. In every case we measure at low temperatures a large chain extension as previously described in polysiloxanes. Par diffusion des neutrons aux petits angles nous observons que la chaîne de polyacrylates “en haltère” adopte une conformation type prolate en phase nématique. Son anisotropie est d'autant plus grande que l'espaceur est plus court. Dans tous les cas, nous retrouvons à basse température la forte extension de la chaîne polymère qui fut d'abord révélée dans les polysiloxanes.

The suite of small-angle neutron scattering instruments at Oak Ridge National Laboratory

DOE PAGES

Heller, William T.; Cuneo, Matthew J.; Debeer-Schmitt, Lisa M.; ...

2018-02-21

Oak Ridge National Laboratory is home to the High Flux Isotope Reactor (HFIR), a high-flux research reactor, and the Spallation Neutron Source (SNS), the world's most intense source of pulsed neutron beams. The unique co-localization of these two sources provided an opportunity to develop a suite of complementary small-angle neutron scattering instruments for studies of large-scale structures: the GP-SANS and Bio-SANS instruments at the HFIR and the EQ-SANS and TOF-USANS instruments at the SNS. This article provides an overview of the capabilities of the suite of instruments, with specific emphasis on how they complement each other. As a result, amore » description of the plans for future developments including greater integration of the suite into a single point of entry for neutron scattering studies of large-scale structures is also provided.« less

The suite of small-angle neutron scattering instruments at Oak Ridge National Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heller, William T.; Cuneo, Matthew J.; Debeer-Schmitt, Lisa M.

Oak Ridge National Laboratory is home to the High Flux Isotope Reactor (HFIR), a high-flux research reactor, and the Spallation Neutron Source (SNS), the world's most intense source of pulsed neutron beams. The unique co-localization of these two sources provided an opportunity to develop a suite of complementary small-angle neutron scattering instruments for studies of large-scale structures: the GP-SANS and Bio-SANS instruments at the HFIR and the EQ-SANS and TOF-USANS instruments at the SNS. This article provides an overview of the capabilities of the suite of instruments, with specific emphasis on how they complement each other. As a result, amore » description of the plans for future developments including greater integration of the suite into a single point of entry for neutron scattering studies of large-scale structures is also provided.« less

Vacuum System Upgrade for Extended Q-Range Small-Angle Neutron Scattering Diffractometer (EQ-SANS) at SNS

DOE PAGES

Stone, Christopher M.; Williams, Derrick C.; Price, Jeremy P.

2016-09-23

The Extended Q-Range Small-Angle Neutron Scattering Diffractometer (EQ-SANS) instrument at the Spallation Neutron Source (SNS), Oak Ridge, Tennessee, incorporates a 69m3 detector vessel with a vacuum system which required an upgrade with respect to performance, ease of operation, and maintenance. The upgrade focused on improving pumping performance as well as optimizing system design to minimize opportunity for operational error. This upgrade provided the following practical contributions: Reduced time required to evacuate from atmospheric pressure to 2mTorr from 500-1,000 minutes to 60-70 minutes Provided turn-key automated control with a multi-faceted interlock for personnel and machine safety.

Vacuum System Upgrade for Extended Q-Range Small-Angle Neutron Scattering Diffractometer (EQ-SANS) at SNS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stone, Christopher M.; Williams, Derrick C.; Price, Jeremy P.

The Extended Q-Range Small-Angle Neutron Scattering Diffractometer (EQ-SANS) instrument at the Spallation Neutron Source (SNS), Oak Ridge, Tennessee, incorporates a 69m3 detector vessel with a vacuum system which required an upgrade with respect to performance, ease of operation, and maintenance. The upgrade focused on improving pumping performance as well as optimizing system design to minimize opportunity for operational error. This upgrade provided the following practical contributions: Reduced time required to evacuate from atmospheric pressure to 2mTorr from 500-1,000 minutes to 60-70 minutes Provided turn-key automated control with a multi-faceted interlock for personnel and machine safety.

A novel small-angle neutron scattering detector geometry

PubMed Central

Kanaki, Kalliopi; Jackson, Andrew; Hall-Wilton, Richard; Piscitelli, Francesco; Kirstein, Oliver; Andersen, Ken H.

2013-01-01

A novel 2π detector geometry for small-angle neutron scattering (SANS) applications is presented and its theoretical performance evaluated. Such a novel geometry is ideally suited for a SANS instrument at the European Spallation Source (ESS). Motivated by the low availability and high price of 3He, the new concept utilizes gaseous detectors with 10B as the neutron converter. The shape of the detector is inspired by an optimization process based on the properties of the conversion material. Advantages over the detector geometry traditionally used on SANS instruments are discussed. The angular and time resolutions of the proposed detector concept are shown to satisfy the requirements of the particular SANS instrument. PMID:24046504

Small Angle Neutron Scattering (SANS) Studies on the Structural Evolution of Pyromellitamide Self-assembled Gels

DOE PAGES

Scott, Jamieson; Tong, Katie; William, Hamilton; ...

2014-10-31

The kinetics of aggregation of two pyromellitamide gelators; tetrabutyl- (C4) and tetrahexylpyromellitamide (C6), in deuterated cyclohexane has been investigated by small angle neutron scattering (SANS) for up to six days. The purpose of this study was to improve our understanding of how self-assembled gels are formed. Short-term (< 3 hour) time scales revealed multiple phases with the data for the tetrabutylpyromellitamide C4 indicating one dimensional stacking and aggregation corresponding to a multi-fiber braided cluster arrangement that is about 35 Å in diameter. The corresponding tetrahexylpyromellitamide C6 data suggests that the C6 also forms one-dimensional stacks but that these aggregate tomore » a thicker multi-fiber braided cluster that have a diameter of 61.8 Å. Over a longer period of time, the radius, persistence length and contour length all continue to increase in 6 days after cooling. This data suggests that structural changes in self-assembled gels occur over a period exceeding several days and that fairly subtle changes in the structure (e.g. tail-length) can influence the packing of molecules in self-assembled gels on the single-to-few fiber bundle stage.« less

Small angle neutron scattering (SANS) studies on the structural evolution of pyromellitamide self-assembled gels.

PubMed

Jamieson, Scott A; Tong, Katie W K; Hamilton, William A; He, Lilin; James, Michael; Thordarson, Pall

2014-11-25

The kinetics of aggregation of two pyromellitamide gelators, tetrabutyl- (C4) and tetrahexyl-pyromellitamide (C6), in deuterated cyclohexane has been investigated by small angle neutron scattering (SANS) for up to 6 days. The purpose of this study was to improve our understanding of how self-assembled gels are formed. Short-term (< 3 h) time scales revealed multiple phases with the data for the tetrabutylpyromellitamide C4, indicating one-dimensional stacking and aggregation corresponding to a multifiber braided cluster arrangement that is about 35 Å in diameter. The corresponding tetrahexylpyromellitamide C6 data suggest that the C6 also forms one-dimensional stacks but that these aggregate to a thicker multifiber braided cluster that has a diameter of about 62 Å. Over a longer period of time, the radius, persistence length, and contour length all continue to increase in 6 days after cooling. These data suggest that structural changes in self-assembled gels occur over a period exceeding several days and that fairly subtle changes in the structure (e.g., tail-length) can influence the packing of molecules in self-assembled gels on the single-to-few fiber bundle stage.

Small Angle Neutron Scattering (SANS) Studies on the Structural Evolution of Pyromellitamide Self-assembled Gels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scott, Jamieson; Tong, Katie; William, Hamilton

The kinetics of aggregation of two pyromellitamide gelators; tetrabutyl- (C4) and tetrahexylpyromellitamide (C6), in deuterated cyclohexane has been investigated by small angle neutron scattering (SANS) for up to six days. The purpose of this study was to improve our understanding of how self-assembled gels are formed. Short-term (< 3 hour) time scales revealed multiple phases with the data for the tetrabutylpyromellitamide C4 indicating one dimensional stacking and aggregation corresponding to a multi-fiber braided cluster arrangement that is about 35 Å in diameter. The corresponding tetrahexylpyromellitamide C6 data suggests that the C6 also forms one-dimensional stacks but that these aggregate tomore » a thicker multi-fiber braided cluster that have a diameter of 61.8 Å. Over a longer period of time, the radius, persistence length and contour length all continue to increase in 6 days after cooling. This data suggests that structural changes in self-assembled gels occur over a period exceeding several days and that fairly subtle changes in the structure (e.g. tail-length) can influence the packing of molecules in self-assembled gels on the single-to-few fiber bundle stage.« less

Characterization of nano-sized oxides in Fe-12Cr oxide-dispersion-strengthened ferritic steel using small-angle neutron scattering

NASA Astrophysics Data System (ADS)

Han, Young-Soo; Mao, Xiaodong; Jang, Jinsung; Kim, Tae-Kyu

2015-04-01

The ferritic ODS steel was manufactured by hot isostatic pressing and heat treatment. The nano-sized microstructures such as yttrium oxides and Cr oxides were quantitatively analyzed by small-angle neutron scattering (SANS). The effects of the fabrication conditions on the nano-sized microstructure were investigated in relation to the quantitative analysis results obtained by SANS. The ratio between magnetic and nuclear scattering components was calculated, and the characteristics of the nano-sized yttrium oxides are discussed based on the SANS analysis results.

Distinguishing oil and water layers in a cracked porous medium using pulsed neutron logging data based on Hudson's crack theory

NASA Astrophysics Data System (ADS)

Zhang, Xueang; Yang, Zhichao; Tang, Bin; Wang, Renbo; Wei, Xiong

2018-05-01

During geophysical surveys, water layers may interfere with the detection of oil layers. In order to distinguish between oil and water layers in porous cracked media, research on the properties of the cracks, the oil and water layers, and their relation to pulsed neutron logging characteristics is essential. Using Hudson's crack theory, we simulated oil and water layers in a cracked porous medium with different crack parameters corresponding to the well log responses. We found that, in a cracked medium with medium-angle (40°-50°) cracks, the thermal neutron count peak value is higher and more sensitive than those in low-angle and high-angle crack environments; in addition, the thermal neutron density distribution shows more minimum values than in other cases. Further, the thermal neutron count and the rate of change for the oil layer are greater than those of the water layer, and the time spectrum count peak value for the water layer in middle-high-angle (40°-70°) cracked environments is higher than that of the oil layer. The thermal neutron density distribution sensitivity is higher in the water layer with a range of small crack angles (0°-30°) than in the oil layer with the same range of angles. In comparing the thermal neutron density distribution, thermal neutron count peak, thermal neutron density distribution sensitivity, and time spectrum maximum in the oil and water layers, we find that neutrons in medium-angle (40°-50°) cracked reservoirs are more sensitive to deceleration and absorption than those in water layers; neutrons in approximately horizontal (0°-30°) cracked water layers are more sensitive to deceleration than those in reservoirs. These results can guide future work in the cracked media neutron logging field.

CAMEA—A novel multiplexing analyzer for neutron spectroscopy

NASA Astrophysics Data System (ADS)

Groitl, Felix; Graf, Dieter; Birk, Jonas Okkels; Markó, Márton; Bartkowiak, Marek; Filges, Uwe; Niedermayer, Christof; Rüegg, Christian; Rønnow, Henrik M.

2016-03-01

The analyzer detector system continuous angle multiple energy analysis will be installed on the cold-neutron triple-axis spectrometer RITA-2 at SINQ, PSI. CAMEA is optimized for efficiency in the horizontal scattering plane enabling rapid and detailed mapping of excitations. As a novelty the design employs a series of several sequential upward scattering analyzer arcs. Each arc is set to a different, fixed, final energy and scatters neutrons towards position sensitive detectors. Thus, neutrons with different final energies are recorded simultaneously over a large angular range. In a single data-acquisition many entire constant-energy lines in the horizontal scattering plane are recorded for a quasi-continuous angular coverage of about 60°. With a large combined coverage in energy and momentum, this will result in a very efficient spectrometer, which will be particularly suited for parametric studies under extreme conditions with restrictive sample environments (high field magnets or pressure cells) and for small samples of novel materials. In this paper we outline the concept and the specifications of the instrument currently under construction.

Nanospheres with a smectic hydrophobic core and an amorphous PEG hydrophilic shell: structural changes and implications for drug delivery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murthy, N. Sanjeeva; Zhang, Zheng; Borsadia, Siddharth

The structural changes in nanospheres with a crystalline core and an amorphous diffuse shell were investigated by small-angle neutron scattering (SANS), small-, medium-, and wide-angle X-ray scattering (SAXS, MAXS and WAXS), and differential scanning calorimetry (DSC).

Applicability of the two-angle differential method to response measurement of neutron-sensitive devices at the RCNP high-energy neutron facility

NASA Astrophysics Data System (ADS)

Masuda, Akihiko; Matsumoto, Tetsuro; Iwamoto, Yosuke; Hagiwara, Masayuki; Satoh, Daiki; Sato, Tatsuhiko; Iwase, Hiroshi; Yashima, Hiroshi; Nakane, Yoshihiro; Nishiyama, Jun; Shima, Tatsushi; Tamii, Atsushi; Hatanaka, Kichiji; Harano, Hideki; Nakamura, Takashi

2017-03-01

Quasi-monoenergetic high-energy neutron fields induced by 7Li(p,n) reactions are used for the response evaluation of neutron-sensitive devices. The quasi-monoenergetic high-energy field consists of high-energy monoenergetic peak neutrons and unwanted continuum neutrons down to the low-energy region. A two-angle differential method has been developed to compensate for the effect of the continuum neutrons in the response measurements. In this study, the two-angle differential method was demonstrated for Bonner sphere detectors, which are typical examples of moderator-based neutron-sensitive detectors, to investigate the method's applicability and its dependence on detector characteristics. Experiments were performed under 96-387 MeV quasi-monoenergetic high-energy neutron fields at the Research Center for Nuclear Physics (RCNP), Osaka University. The measurement results for large high-density polyethylene (HDPE) sphere detectors agreed well with Monte Carlo calculations, which verified the adequacy of the two-angle differential method. By contrast, discrepancies were observed in the results for small HDPE sphere detectors and metal-induced sphere detectors. The former indicated that detectors that are particularly sensitive to low-energy neutrons may be affected by penetrating neutrons owing to the geometrical features of the RCNP facility. The latter discrepancy could be consistently explained by a problem in the evaluated cross-section data for the metals used in the calculation. Through those discussions, the adequacy of the two-angle differential method was experimentally verified, and practical suggestions were made pertaining to this method.

On the analysis of time-of-flight spin-echo modulated dark-field imaging data

NASA Astrophysics Data System (ADS)

Sales, Morten; Plomp, Jeroen; Bouwman, Wim G.; Tremsin, Anton S.; Habicht, Klaus; Strobl, Markus

2017-06-01

Spin-Echo Modulated Small Angle Neutron Scattering with spatial resolution, i.e. quantitative Spin-Echo Dark Field Imaging, is an emerging technique coupling neutron imaging with spatially resolved quantitative small angle scattering information. However, the currently achieved relatively large modulation periods of the order of millimeters are superimposed to the images of the samples. So far this required an independent reduction and analyses of the image and scattering information encoded in the measured data and is involving extensive curve fitting routines. Apart from requiring a priori decisions potentially limiting the information content that is extractable also a straightforward judgment of the data quality and information content is hindered. In contrast we propose a significantly simplified routine directly applied to the measured data, which does not only allow an immediate first assessment of data quality and delaying decisions on potentially information content limiting further reduction steps to a later and better informed state, but also, as results suggest, generally better analyses. In addition the method enables to drop the spatial resolution detector requirement for non-spatially resolved Spin-Echo Modulated Small Angle Neutron Scattering.

The effects of burial diagenesis on multiscale porosity in the St. Peter Sandstone: An imaging, small-angle, and ultra-small-angle neutron scattering analysis

DOE PAGES

Anovitz, Lawrence M.; Freiburg, Jared T.; Wasbrough, Matthew; ...

2017-11-06

To examine the effects of burial diagenesis on heirarchical pore structures in sandstone and compare those with the effects of overgrowth formation, we obtained samples of St. Peter Sandstone from drill cores obtained in the Illinois and Michigan Basins. The multiscale pore structure of rocks in sedimentary reservoirs and the mineralogy associated with those pores are critical factors for estimating reservoir properties, including fluid mass in place, permeability, and capillary pressures, as well as geochemical interactions between the rock and the fluid. The combination of small- and ultra-small-angle neutron scattering with backscattered electron or X ray-computed tomographic imaging, or both,more » provided a means by which pore structures were quantified at scales ranging from aproximately 1 nm to 1 cm—seven orders of magnitude. Larger scale (>10 µm) porosity showed the expected logarithmic decrease in porosity with depth, although there was significant variation in each sample group. However, small- and ultra-small-angle neutron scattering data showed that the proportion of small-scale porosity increased with depth. Porosity distributions were not continuous, but consisted of a series of log normal-like distributions at several distinct scales within these rocks. Fractal dimensions at larger scales decreased (surfaces smoothed) with increasing depth, and those at smaller scales increased (surfaces roughened) and pores become more isolated (higher lacunarity). Furthermore, data suggest that changes in pore-size distributions are controlled by both physical (compaction) and chemical effects (precipitation, cementation, dissolution).« less

The effects of burial diagenesis on multiscale porosity in the St. Peter Sandstone: An imaging, small-angle, and ultra-small-angle neutron scattering analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anovitz, Lawrence M.; Freiburg, Jared T.; Wasbrough, Matthew

To examine the effects of burial diagenesis on heirarchical pore structures in sandstone and compare those with the effects of overgrowth formation, we obtained samples of St. Peter Sandstone from drill cores obtained in the Illinois and Michigan Basins. The multiscale pore structure of rocks in sedimentary reservoirs and the mineralogy associated with those pores are critical factors for estimating reservoir properties, including fluid mass in place, permeability, and capillary pressures, as well as geochemical interactions between the rock and the fluid. The combination of small- and ultra-small-angle neutron scattering with backscattered electron or X ray-computed tomographic imaging, or both,more » provided a means by which pore structures were quantified at scales ranging from aproximately 1 nm to 1 cm—seven orders of magnitude. Larger scale (>10 µm) porosity showed the expected logarithmic decrease in porosity with depth, although there was significant variation in each sample group. However, small- and ultra-small-angle neutron scattering data showed that the proportion of small-scale porosity increased with depth. Porosity distributions were not continuous, but consisted of a series of log normal-like distributions at several distinct scales within these rocks. Fractal dimensions at larger scales decreased (surfaces smoothed) with increasing depth, and those at smaller scales increased (surfaces roughened) and pores become more isolated (higher lacunarity). Furthermore, data suggest that changes in pore-size distributions are controlled by both physical (compaction) and chemical effects (precipitation, cementation, dissolution).« less

Neutron Reflectometry and Small Angle Neutron Scattering of ABC Miktoarm Terpolymer Thin-Films

NASA Astrophysics Data System (ADS)

Arras, Matthias M. L.; Wang, Weiyu; Mahalik, Jyoti P.; Hong, Kunlun; Sumpter, Bobby G.; Smith, Gregory S.; Chernyy, Sergey; Kim, Hyeyoung; Russell, Thomas P.

Due to the constraint of the junction point in miktoarm terpolymers, where three chains meet, ABC miktoarm terpolymers are promising to obtain nanostructured, long-range ordered materials. We present details of the thin-film structure of ABC miktoarm terpolymers in the poly(styrene), poly(isoprene), poly(2-vinylpyridine) (PS-PI-P2VP) system, investigated by neutron reflectometry and small angle neutron scattering. To this end, we synthesized partially deuterated versions of the PS-PI-P2VP and investigated annealed samples, spin-coated to various thicknesses of the bulk repeat period. Furthermore, we investigated the structural change upon selective blending with homopolymers or fullerenes. We find that thin-film constraints on the morphology can vanish after only twice the repetition period. In addition, it is indicated that nanoparticles improve the ordering in these systems, however, this seems to be not necessarily true for homopolymer blending. This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory.

Spin waves in full-polarized state of Dzyaloshinskii-Moriya helimagnets: Small-angle neutron scattering study

NASA Astrophysics Data System (ADS)

Grigoriev, S. V.; Sukhanov, A. S.; Altynbaev, E. V.; Siegfried, S.-A.; Heinemann, A.; Kizhe, P.; Maleyev, S. V.

2015-12-01

We develop the technique to study the spin-wave dynamics of the full-polarized state of the Dzyaloshinskii-Moriya helimagnets by polarized small-angle neutron scattering. We have experimentally proven that the spin-waves dispersion in this state has the anisotropic form. We show that the neutron scattering image displays a circle with a certain radius which is centered at the momentum transfer corresponding to the helix wave vector in helimagnetic phase ks, which is oriented along the applied magnetic field H . The radius of this circle is directly related to the spin-wave stiffness of this system. This scattering depends on the neutron polarization showing the one-handed nature of the spin waves in Dzyaloshinskii-Moriya helimagnets in the full-polarized phase. We show that the spin-wave stiffness A for MnSi helimagnet decreased twice as the temperature increases from zero to the critical temperature Tc.

A Study of Cross-linked Regions of Poly(Vinyl Alcohol) Gels by Small-Angle Neutron Scattering

NASA Astrophysics Data System (ADS)

Lawrence, Mathias B.; Desa, J. A. E.; Aswal, V. K.

2011-07-01

A poly(vinyl alcohol)-borax cross-linked hydrogel has been studied by Small Angle Neutron Scattering as a function of borax concentration in the wave-vector transfer (Q) range of 0.017 Å-1 to 0.36 Å-1. It is found that as the concentration of borax increases, so does the intensity of scattering in this range. Beyond a borax concentration of 2 mg/ml, the increase in cross-linked PVA chains leads to cross-linked units larger than 150 Å as evidenced by a reduction in intensity in the lower Q region.

Structure of polyacrylic acid and polymethacrylic acid solutions : a small angle neutron scattering study

NASA Astrophysics Data System (ADS)

Moussaid, A.; Schosseler, F.; Munch, J. P.; Candau, S. J.

1993-04-01

The intensity scattered from polyacrylic acid and polymethacrylic acid solutions has been measured by small angle neutron scattering experiemnts. The influence of polymer concentration, ionization degree, temperature and salt content has been investigated. Results are in qualitative agreement with a model which predicts the existence of microphases in the unstable region of the phase diagram. Quantitative comparison with the theory is performed by fitting the theoretical structure factor to the experimental data. For a narrow range of ionizaiton degrees nearly quantitative agreement with the theory is found for the polyacrylic acide system.

In-situ temperature-controllable shear flow device for neutron scattering measurement--an example of aligned bicellar mixtures.

PubMed

Xia, Yan; Li, Ming; Kučerka, Norbert; Li, Shutao; Nieh, Mu-Ping

2015-02-01

We have designed and constructed a temperature-controllable shear flow cell for in-situ study on flow alignable systems. The device has been tested in the neutron diffraction and has the potential to be applied in the small angle neutron scattering configuration to characterize the nanostructures of the materials under flow. The required sample amount is as small as 1 ml. The shear rate on the sample is controlled by the flow rate produced by an external pump and can potentially vary from 0.11 to 3.8 × 10(5) s(-1). Both unidirectional and oscillational flows are achievable by the setting of the pump. The instrument is validated by using a lipid bicellar mixture, which yields non-alignable nanodisc-like bicelles at low T and shear-alignable membranes at high T. Using the shear cell, the bicellar membranes can be aligned at 31 °C under the flow with a shear rate of 11.11 s(-1). Multiple high-order Bragg peaks are observed and the full width at half maximum of the "rocking curve" around the Bragg's condition is found to be 3.5°-4.1°. It is noteworthy that a portion of the membranes remains aligned even after the flow stops. Detailed and comprehensive intensity correction for the rocking curve has been derived based on the finite rectangular sample geometry and the absorption of the neutrons as a function of sample angle [See supplementary material at http://dx.doi.org/10.1063/1.4908165 for the detailed derivation of the absorption correction]. The device offers a new capability to study the conformational or orientational anisotropy of the solvated macromolecules or aggregates induced by the hydrodynamic interaction in a flow field.

Two hump-shaped angular distributions of neutrons and soft X-rays in a small plasma focus device.

PubMed

Habibi, Morteza

2018-03-01

Angular distributions of soft X-rays (SXRs) and neutrons emitted by a small plasma focus device (PFD) were investigated simultaneously using TLD-100 dosimeters and Geiger-Muller activation counters, respectively. The distributions represented two humps with a small dip at the angular position 0° and reduced from the angles of ± 15° and ± 30° for the neutrons and SXRs, respectively. The maximum yield of 2.98 × 10 8 neutrons per shot of the device was obtained at 13.5kV and 6.5mbar. A time of flight (TOF) of 75.2ns between the hard X-ray and the neutron peaks corresponds to neutrons with energy of 2.67MeV. A similar behavior was observed between the angular distributions of neutron and soft X-ray emissions. Copyright © 2018 Elsevier Ltd. All rights reserved.

Structural evolution of photocrosslinked silk fibroin and silk fibroin-based hybrid hydrogels: A small angle and ultra-small angle scattering investigation.

PubMed

Whittaker, Jasmin L; Balu, Rajkamal; Knott, Robert; de Campo, Liliana; Mata, Jitendra P; Rehm, Christine; Hill, Anita J; Dutta, Naba K; Roy Choudhury, Namita

2018-07-15

Regenerated Bombyx mori silk fibroin (RSF) is a widely recognized protein for biomedical applications; however, its hierarchical gel structure is poorly understood. In this paper, the hierarchical structure of photocrosslinked RSF and RSF-based hybrid hydrogel systems: (i) RSF/Rec1-resilin and (ii) RSF/poly(N-vinylcaprolactam (PVCL) is reported for the first time using small-angle scattering (SAS) techniques. The structure of RSF in dilute to concentrated solution to fabricated hydrogels were characterized using small angle X-ray scattering (SAXS), small angle neutron scattering (SANS) and ultra-small angle neutron scattering (USANS) techniques. The RSF hydrogel exhibited three distinctive structural characteristics: (i) a Porod region in the length scale of 2 to 3nm due to hydrophobic domains (containing β-sheets) which exhibits sharp interfaces with the amorphous matrix of the hydrogel and the solvent, (ii) a Guinier region in the length scale of 4 to 20nm due to hydrophilic domains (containing turns and random coil), and (iii) a Porod-like region in the length scale of few micrometers due to water pores/channels exhibiting fractal-like characteristics. Addition of Rec1-resilin or PVCL to RSF and subsequent crosslinking systematically increased the nanoscale size of hydrophobic and hydrophilic domains, whereas decreased the homogeneity of pore size distribution in the microscale. The presented results have implications on the fundamental understanding of the structure-property relationship of RSF-based hydrogels. Copyright © 2018. Published by Elsevier B.V.

Direct Observation Of Nanoparticle-Surfactant Interactions Using Small Angle Neutron Scattering

NASA Astrophysics Data System (ADS)

Kumar, Sugam; Aswal, V. K.

2010-12-01

Interactions of anionic silica nanoparticles with anionic, cationic and nonionic surfactants have directly been studied by contrast variation small angle neutron scattering (SANS). The measurements are performed on 1 wt% of both silica nanoparticles and surfactants of anionic sodium dodecyle sulphate (SDS), cationic dodecyltrimethyl ammonium bromide (DTAB) and non-ionic polyoxyethylene 10 lauryl ether (C12E10) in aqueous solution. We show that there is no direct interaction in the case of SDS with silica particles, whereas strong interaction for DTAB leads to the aggregation of silica particles. The interaction of C12E10 is found through the micelles adsorbed on the silica particles.

Scattering from fractals

NASA Astrophysics Data System (ADS)

Hurd, Alan J.

The realization that structures in Nature often can be described by Mandelbrot's fractals has led to a revolution in many areas of physics. The interaction of waves with fractal systems has, understandably, become intensely studied since scattering is the method of choice to probe delicate fractal structures such as chainlike particle aggregates. Not all of these waves are electromagnetic. Neutron scattering, for example, is an important complementary tool to structural studies by X-ray and light scattering. Since the phenomenology of small-angle neutron scattering (SANS), as it is applied to fractal systems, is identical to that of small-angle X-ray scattering (SAXS), it falls within the scope of this paper.

Interpretation of small-angle diffraction experiments on opal-like photonic crystals

NASA Astrophysics Data System (ADS)

Marlow, F.; Muldarisnur, M.; Sharifi, P.; Zabel, H.

2011-08-01

Comprehensive structural information on artificial opals involving the deviations from the strongly dominating face-centered cubic structure is still missing. Recent structure investigations with neutrons and synchrotron sources have shown a high degree of order but also a number of unexpected scattering features. Here, we point out that the exclusion of the allowed 002-type diffraction peaks by a small atomic form factor is not obvious and that surface scattering has to be included as a possible source for the diffraction peaks. Our neutron diffraction data indicate that surface scattering is the main reason for the smallest-angle peaks in the diffraction patterns.

Small-angle neutron scattering study of recombinant yeast-derived human hepatitis B virus surface antigen vaccine particle

NASA Astrophysics Data System (ADS)

Sato, M.; Ito, Y.; Kameyama, K.; Imai, M.; Ishikawa, N.; Takagi, T.

1995-02-01

The overall and internal structure of recombinant yeast-derived human hepatitis B virus surface antigen vaccine particles was investigated by small-angle neutron scattering using the contrast variation method. The vaccine is a nearly spherical particle, and its contrast-matching point was determined to be at about 24% D 2O content, indicating that a large part of the vaccine particle is occupied by lipids and carbohydrates from the yeast. The Stuhrmann plot suggests that the surface antigens exist predominantly in the peripheral region of the particle, which is favorable to the induction of anti-virus antibodies.

Use of Small Angle Neutron Scattering to Study Various Properties of Wool and Mohair Fibres

DOE Office of Scientific and Technical Information (OSTI.GOV)

Franklyn, C. B.; Toeroek, Gy.

2011-12-13

To maintain a competitive edge in the wool and mohair industry, a detailed knowledge and understanding of the properties of wool fibres is essential. Standard techniques are used to determine fibre diameter, length and strength; however, properties such as hydroscopicity, lustre and changes in fibre structure following chemical or mechanical treatment are not so well understood. The unique capabilities of small angle neutron scattering to study changes in the supermolecular structure of wool fibres, particularly at the level of the microfibril-matrix complex, have been used to provide previously unknown features of the fibres. The results of these studies are presented.

Mean-field Ising crossover and the critical exponents γ, ν, and η for a polymer blend: d-PB/PS studied by small-angle neutron scattering

NASA Astrophysics Data System (ADS)

Janssen, S.; Schwahn, D.; Springer, T.

1992-05-01

The critical behavior of the polymer blend d-PB/PS was investigated by small-angle neutron scattering experiments. 3D Ising behavior was clearly observed with the critical exponents γ=1.26+/-0.01, ν=0.59+/-0.01, and η=0.047+/-0.004. The crossover to mean-field behavior occurs at T*=Tc+5.4 K. This is compared with the results of other experiments and the Landau-Ginzburg criterion. The Q dependence of the structure factor S(Q) follows the Ornstein-Zernike form in both regimes.

Effect of calcium/sodium ion exchange on the osmotic properties and structure of polyelectrolyte gels.

PubMed

Horkay, Ferenc; Basser, Peter J; Hecht, Anne-Marie; Geissler, Erik

2015-12-01

We discuss the main findings of a long-term research program exploring the consequences of sodium/calcium ion exchange on the macroscopic osmotic and elastic properties, and the microscopic structure of representative synthetic polyelectrolyte (sodium polyacrylate, (polyacrylic acid)) and biopolymer gels (DNA). A common feature of these gels is that above a threshold calcium ion concentration, they exhibit a reversible volume phase transition. At the macroscopic level, the concentration dependence of the osmotic pressure shows that calcium ions influence primarily the third-order interaction term in the Flory-Huggins model of polymer solutions. Mechanical tests reveal that the elastic modulus is practically unaffected by the presence of calcium ions, indicating that ion bridging does not create permanent cross-links. At the microscopic level, small-angle neutron scattering shows that polyacrylic acid and DNA gels exhibit qualitatively similar structural features in spite of important differences (e.g. chain flexibility and chemical composition) between the two polymers. The main effect of calcium ions is that the neutron scattering intensity increases due to the decrease in the osmotic modulus. At the level of the counterion cloud around dissolved macroions, anomalous small-angle X-ray scattering measurements made on DNA indicate that divalent ions form a cylindrical sheath enveloping the chain, but they are not localized. Small-angle neutron scattering and small-angle X-ray scattering provide complementary information on the structure and interactions in polymer solutions and gels. © IMechE 2015.

Experimental study of boron-coated straws with a neutron source

NASA Astrophysics Data System (ADS)

Xie, Zhaoyang; Zhou, Jianrong; Song, Yushou; Lacy, Jeffrey L.; Sun, Liang; Sun, Zhijia; Hu, Bitao; Chen, Yuanbo

2018-04-01

Multiple types of high quality neutron detectors are proposed for the first phase of the China Spallation Neutron Source (CSNS), which will be commissioned in 2018. Considering the shortage of 3He supply, a detector module composed of 49 boron-coated straws (BCS) was developed by Proportional Technologies Inc. (PTI). Each straw has a length of 1000 mm and a diameter of 7.5 mm. Seven straws are tightly packed in a tube, and seven tubes are organized in a row to form a detector module. The charge division method is used for longitudinal positioning. A specific readout system was utilized to output the signal and simultaneously encode each straw. The performance of this detector module was studied using a moderated 252Cf source at the Institute of High Energy Physics (IHEP). The signal amplitude spectrum indicates its n-gamma discrimination capability. Despite the complex readout method, a longitudinal resolution of FWHM=6.1 ± 0.5 mm was obtained. The three-dimensional positioning ability qualifies this BCS detector module as a promising detector for small angle neutron scattering.

Universality of the helimagnetic transition in cubic chiral magnets: Small angle neutron scattering and neutron spin echo spectroscopy studies of FeCoSi

NASA Astrophysics Data System (ADS)

Bannenberg, L. J.; Kakurai, K.; Falus, P.; Lelièvre-Berna, E.; Dalgliesh, R.; Dewhurst, C. D.; Qian, F.; Onose, Y.; Endoh, Y.; Tokura, Y.; Pappas, C.

2017-04-01

We present a comprehensive small angle neutron scattering and neutron spin echo spectroscopy study of the structural and dynamical aspects of the helimagnetic transition in Fe1 -xCoxSi with x =0.30 . In contrast to the sharp transition observed in the archetype chiral magnet MnSi, the transition in Fe1 -xCoxSi is gradual, and long-range helimagnetic ordering coexists with short-range correlations over a wide temperature range. The dynamics are more complex than in MnSi and involve long relaxation times with a stretched exponential relaxation which persists even under magnetic field. These results in conjunction with an analysis of the hierarchy of the relevant length scales show that the helimagnetic transition in Fe1 -xCoxSi differs substantially from the transition in MnSi and question the validity of a universal approach to the helimagnetic transition in chiral magnets.

Quasielastic small-angle neutron scattering from heavy water solutions of cyclodextrins

NASA Astrophysics Data System (ADS)

Kusmin, André; Lechner, Ruep E.; Saenger, Wolfram

2011-01-01

We present a model for quasielastic neutron scattering (QENS) by an aqueous solution of compact and inflexible molecules. This model accounts for time-dependent spatial pair correlations between the atoms of the same as well as of distinct molecules and includes all coherent and incoherent neutron scattering contributions. The extension of the static theory of the excluded volume effect [A. K. Soper, J. Phys.: Condens. Matter 9, 2399 (1997)] to the time-dependent (dynamic) case allows us to obtain simplified model expressions for QENS spectra in the low Q region in the uniform fluid approximation. The resulting expressions describe the quasielastic small-angle neutron scattering (QESANS) spectra of D _2O solutions of native and methylated cyclodextrins well, yielding in particular translational and rotational diffusion coefficients of these compounds in aqueous solution. Finally, we discuss the full potential of the QESANS analysis (that is, beyond the uniform fluid approximation), in particular, the information on solute-solvent interactions (e.g., hydration shell properties) that such an analysis can provide, in principle.

Effect of benzocaine and propranolol on phospholipid-based bilayers.

PubMed

Mangiapia, G; Gvaramia, M; Kuhrts, L; Teixeira, J; Koutsioubas, A; Soltwedel, O; Frielinghaus, H

2017-12-06

Cell membranes play a fundamental role in protecting the cell from its surroundings, in addition to hosting many proteins with fundamental biological tasks. A study of drug/lipid interactions is a necessary and important step in fully clarifying the role and action mechanism of active ingredients, and shedding light on possible complications caused by drug overdosage. In this paper, the influence of benzocaine and propranolol drugs on the structure of l-α-phosphatidylcholine-based membranes has been investigated by means of neutron reflectivity, grazing incidence small angle neutron scattering, and small/ultra-small angle neutron scattering. Investigations allowed discovering a stiffening of the membranes and the formation of stalks, caused by the presence of benzocaine. On the other hand, disordered bilayers (lamellar powders) and highly curved structures were found in the presence of propranolol. The results obtained may be rationalized in terms of the molecular structures of drugs and may serve as a starting point for explaining the toxic behavior in long-term and overdosage scenarios.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Groitl, Felix, E-mail: felix.groitl@psi.ch; Paul Scherrer Institute, Laboratory for Neutron Scattering and Imaging, 5232 Villigen; Graf, Dieter

The analyzer detector system continuous angle multiple energy analysis will be installed on the cold-neutron triple-axis spectrometer RITA-2 at SINQ, PSI. CAMEA is optimized for efficiency in the horizontal scattering plane enabling rapid and detailed mapping of excitations. As a novelty the design employs a series of several sequential upward scattering analyzer arcs. Each arc is set to a different, fixed, final energy and scatters neutrons towards position sensitive detectors. Thus, neutrons with different final energies are recorded simultaneously over a large angular range. In a single data-acquisition many entire constant-energy lines in the horizontal scattering plane are recorded formore » a quasi-continuous angular coverage of about 60°. With a large combined coverage in energy and momentum, this will result in a very efficient spectrometer, which will be particularly suited for parametric studies under extreme conditions with restrictive sample environments (high field magnets or pressure cells) and for small samples of novel materials. In this paper we outline the concept and the specifications of the instrument currently under construction.« less

SUSANS With Polarized Neutrons.

PubMed

Wagh, Apoorva G; Rakhecha, Veer Chand; Strobl, Makus; Treimer, Wolfgang

2005-01-01

Super Ultra-Small Angle Neutron Scattering (SUSANS) studies over wave vector transfers of 10(-4) nm(-1) to 10(-3) nm(-1) afford information on micrometer-size agglomerates in samples. Using a right-angled magnetic air prism, we have achieved a separation of ≈10 arcsec between ≈2 arcsec wide up- and down-spin peaks of 0.54 nm neutrons. The SUSANS instrument has thus been equipped with the polarized neutron option. The samples are placed in a uniform vertical field of 8.8 × 10(4) A/m (1.1 kOe). Several magnetic alloy ribbon samples broaden the up-spin neutron peak significantly over the ±1.3 × 10(-3) nm(-1) range, while leaving the down-spin peak essentially unaltered. Fourier transforms of these SUSANS spectra corrected for the instrument resolution, yield micrometer-range pair distribution functions for up- and down-spin neutrons as well as the nuclear and magnetic scattering length density distributions in the samples.

Fission time scale from pre-scission neutron and α multiplicities in the 16O + 194Pt reaction

NASA Astrophysics Data System (ADS)

Kapoor, K.; Verma, S.; Sharma, P.; Mahajan, R.; Kaur, N.; Kaur, G.; Behera, B. R.; Singh, K. P.; Kumar, A.; Singh, H.; Dubey, R.; Saneesh, N.; Jhingan, A.; Sugathan, P.; Mohanto, G.; Nayak, B. K.; Saxena, A.; Sharma, H. P.; Chamoli, S. K.; Mukul, I.; Singh, V.

2017-11-01

Pre- and post-scission α -particle multiplicities have been measured for the reaction 16O+P194t at 98.4 MeV forming R210n compound nucleus. α particles were measured at various angles in coincidence with the fission fragments. Moving source technique was used to extract the pre- and post-scission contributions to the particle multiplicity. Study of the fission mechanism using the different probes are helpful in understanding the detailed reaction dynamics. The neutron multiplicities for this reaction have been reported earlier. The multiplicities of neutrons and α particles were reproduced using standard statistical model code joanne2 by varying the transient (τt r) and saddle to scission (τs s c) times. This code includes deformation dependent-particle transmission coefficients, binding energies and level densities. Fission time scales of the order of 50-65 ×10-21 s are required to reproduce the neutron and α -particle multiplicities.

FINAL REPORT: DOE CONTRACT NUMBER FG0205ER64026 Biological Neutron Scattering: A Collaboration with the Oak Ridge Center for Structural Molecular Biology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trewhella, Jill

2011-01-12

The overarching goal of this project was to promote applications of small-angle scattering in structural molecular biology by providing model examples of cutting edge applications that demonstrate the unique capabilities and potential of the DOE national user facilities at Oak Ridge, especially the newly commissioned BioSANS. The approach taken was three-fold: (1) to engage in high impact collaborative research projects that would benefit from small-angle neutron scattering to both demonstrate the power of the technique while expanding the potential user community; (2) to provide access to scattering facilities established at the University of Utah to as broad a set ofmore » researchers as possible to increase the expertise in small-angle scattering generally; and (3) to develop new methods and tools for small-angle scattering. To these ends, three major research collaborations were pursued that resulted in a significant body of published work where neutron scattering and contrast variation played a major role. These major collaborations involved studies of protein complexes involved in (1) bacterial transcription regulation and adaptive response (a DOE/BER priority area); (2) regulation of cardiac muscle; and (3) neuronal disorders. In addition, to broaden the impact of the project, smaller collaborative efforts were supported that used either small-angle X-ray or neutron scattering. Finally, the DOE supported facilities at the University of Utah were made available to researchers on a service basis and a number of independent groups took advantage of this opportunity. In all of this work, there was an emphasis on the training of students and post docs in scattering techniques, and a set of publications (a book chapter, a review, and an encyclopedia article) were produced to guide the non-specialist potential user of scattering techniques in successful applications of the techniques. We also developed a suite of user friendly web-based computational tools currently being accessed world-wide by researchers as an aid in neutron scattering data interpretation. In all, these collaborative projects and resulted in 29 original refereed journal articles published between 2005 and 2010 and engaged groups from at least 14 Universities (10 US, 4 international) and 3 National Laboratories (2 US, 1 international). An important final initiative from this project was to begin a process for international community agreement on a set of standards for the publication of biomolecular small-angle scattering data. This initiative is being championed with the International Union of Crystallography and has engaged a number of Journal Editors and is a very important step in the maturing of this now burgeoning field.« less

Nondispersive neutron focusing method beyond the critical angle of mirrors

DOEpatents

Ice, Gene E.

2008-10-21

This invention extends the Kirkpatrick-Baez (KB) mirror focusing geometry to allow nondispersive focusing of neutrons with a convergence on a sample much larger than is possible with existing KB optical schemes by establishing an array of at least three mirrors and focusing neutrons by appropriate multiple deflections via the array. The method may be utilized with supermirrors, multilayer mirrors, or total external reflection mirrors. Because high-energy x-rays behave like neutrons in their absorption and reflectivity rates, this method may be used with x-rays as well as neutrons.

Small-Angle Neutron Scattering and Neutron Spin Echo Characterization of Monoclonal Antibody Self-Associations at High Concentrations

NASA Astrophysics Data System (ADS)

Yearley, Eric; Zarraga, Isidro (Dan); Godfrin, Paul (Doug); Perevozchikova, Tatiana; Wagner, Norman; Liu, Yun

2013-03-01

Concentrated therapeutic protein formulations offer numerous delivery and stability challenges. In particular, it has been found that several therapeutic proteins exhibit a large increase in viscosity as a function of concentration that may be dependent on the protein-protein interactions. Small-Angle Neutron Scattering (SANS) and Neutron Spin Echo (NSE) investigations have been performed to probe the protein-protein interactions and diffusive properties of highly concentrated MAbs. The SANS data demonstrate that the inter-particle interactions for a highly viscous MAb at high concentrations (MAb1) are highly attractive, anisotropic and change significantly with concentration while the viscosity and interactions do not differ considerably for MAb2. The NSE results furthermore indicate that MAb1 and MAb2 have strong concentration dependencies of dynamics at high Q that are correlated to the translational motion of the proteins. Finally, it has also been revealed that the individual MAb1 proteins form small clusters at high concentrations in contrast to the MAb2 proteins, which are well-dispersed. It is proposed that the formation of these clusters is the primary cause of the dramatic increase in viscosity of MAb1 in crowded or concentrated environments.

Small Angle Neutron Scattering Observation of Chain Retraction after a Large Step Deformation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blanchard, A.; Heinrich, M.; Pyckhout-Hintzen, W.

The process of retraction in entangled linear chains after a fast nonlinear stretch was detected from time-resolved but quenched small angle neutron scattering (SANS) experiments on long, well-entangled polyisoprene chains. The statically obtained SANS data cover the relevant time regime for retraction, and they provide a direct, microscopic verification of this nonlinear process as predicted by the tube model. Clear, quantitative agreement is found with recent theories of contour length fluctuations and convective constraint release, using parameters obtained mainly from linear rheology. The theory captures the full range of scattering vectors once the crossover to fluctuations on length scales belowmore » the tube diameter is accounted for.« less

Clustering of water molecules in ultramicroporous carbon: In-situ small-angle neutron scattering

DOE PAGES

Bahadur, Jitendra; Contescu, Cristian I.; Rai, Durgesh K.; ...

2016-10-19

The adsorption of water is central to most of the applications of microporous carbon as adsorbent material. We report early kinetics of water adsorption in the microporous carbon using in-situ small-angle neutron scattering. It is observed that adsorption of water occurs via cluster formation of molecules. Interestingly, the cluster size remains constant throughout the adsorption process whereas number density of clusters increases with time. The role of surface chemistry of microporous carbon on the early kinetics of adsorption process was also investigated. Lastly, the present study provides direct experimental evidence for cluster assisted adsorption of water molecules in microporous carbonmore » (Do-Do model).« less

Insights into molecular architecture of terpenes using small angle neutron scattering

NASA Astrophysics Data System (ADS)

Rai, Durgesh K.; Annamraju, Aparna; Pingali, Sai Venkatesh; O'Neill, Hugh M.; Mewalal, Ritesh; Gunter, Lee E.; Tuskan, Gerald A.

Understanding macromolecular architectures is vital to engineering prospective terpene candidates for advanced biofuels. Eucalyptus plants store terpenes in specialized cavity-like structures in the leaves called oil glands, which comprises of volatile (VTs) and non-volatile (NVTs) terpenes. Using small-angle neutron scattering, we have investigated the structure and phase behavior of the supramolecular assembly formed by Geranyl beta-D-glucoside (GDG), a NVT and compare the results with that of beta-octyl glucoside (BOG). The formation of micellar structures was observed in the concentration range of 0.5-5 v/v% in water using small angle neutron scattering (SANS) where Schultz sphere model was used in quantifying structural parameters of micelles. SANS studies determine that GDG and BOG behave like amphiphiles forming micellar structures in aqueous solution. The micelles swell upon addition of alpha-Pinene (AP) indicating partition to the core region of the micelles. The general behavior of the micellar growth after partitioning of AP to form thermodynamically stable sizes varies with the NVT concentration. Our studies reveal that the presence of steric hindrance in the GDG via the unsaturated bonds could help stabilize VTs inside the oil glands. LDRD project LOIS ID 7428, SNS, CSMB, HFIR, ORNL, DOE Office of Science User Facilities.

A new ultrasonic transducer sample cell for in situ small-angle scattering experiments

NASA Astrophysics Data System (ADS)

Gupta, Sudipta; Bleuel, Markus; Schneider, Gerald J.

2018-01-01

Ultrasound irradiation is a commonly used technique for nondestructive diagnostics or targeted destruction. We report on a new versatile sonication device that fits in a variety of standard sample environments for neutron and X-ray scattering instruments. A piezoelectric transducer permits measuring of the time-dependent response of the sample in situ during or after sonication. We use small-angle neutron scattering (SANS) to demonstrate the effect of a time-dependent perturbation on the structure factor of micelles formed from sodium dodecyl sulfate surfactant molecules. We observe a substantial change in the micellar structure during and after exposure to ultrasonic irradiation. We also observe a time-dependent relaxation to the equilibrium values of the unperturbed system. The strength of the perturbation of the structure factor depends systematically on the duration of sonication. The relaxation behavior can be well reproduced after multiple times of sonication. Accumulation of the recorded intensities of the different sonication cycles improves the signal-to-noise ratio and permits reaching very short relaxation times. In addition, we present SANS data for the micellar form factor on alkyl-poly (ethylene oxide) surfactant molecules irradiated by ultrasound. Due to the flexibility of our new in situ sonication device, different experiments can be performed, e.g., to explore molecular potentials in more detail by introducing a systematic time-dependent perturbation.

Small-Angle and Ultrasmall-Angle Neutron Scattering (SANS/USANS) Study of New Albany Shale: A Treatise on Microporosity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bahadur, Jitendra; Radlinski, Andrzej P.; Melnichenko, Yuri B.

We applied small-angle neutron scattering (SANS) and ultrasmall-angle neutron scattering (USANS) techniques to study the microstructure of several New Albany shales of different maturity. It has been established that the total porosity decreases with maturity and increases somewhat for post-mature samples. A new method of SANS data analysis was developed, which allows the extraction of information about the size range and number density of micropores from the relatively flat scattering intensity observed in the limit of the large scattering vector Q. Macropores and significant number of mesopores are surface fractals, and their structure can be described in terms of themore » polydisperse spheres (PDSP) model. The model-independent Porod invariant method was employed to estimate total porosity, and the results were compared with the PDSP model results. It has been demonstrated that independent evaluation of incoherent background is crucial for accurate interpretation of the scattering data in the limit of large Q-values. Moreover, pore volumes estimated by the N 2 and CO 2 adsorption, as well as via the mercury intrusion technique, have been compared with those measured by SANS/USANS, and possible reasons for the observed discrepancies are discussed.« less

Small-Angle and Ultrasmall-Angle Neutron Scattering (SANS/USANS) Study of New Albany Shale: A Treatise on Microporosity

DOE PAGES

Bahadur, Jitendra; Radlinski, Andrzej P.; Melnichenko, Yuri B.; ...

2014-12-17

We applied small-angle neutron scattering (SANS) and ultrasmall-angle neutron scattering (USANS) techniques to study the microstructure of several New Albany shales of different maturity. It has been established that the total porosity decreases with maturity and increases somewhat for post-mature samples. A new method of SANS data analysis was developed, which allows the extraction of information about the size range and number density of micropores from the relatively flat scattering intensity observed in the limit of the large scattering vector Q. Macropores and significant number of mesopores are surface fractals, and their structure can be described in terms of themore » polydisperse spheres (PDSP) model. The model-independent Porod invariant method was employed to estimate total porosity, and the results were compared with the PDSP model results. It has been demonstrated that independent evaluation of incoherent background is crucial for accurate interpretation of the scattering data in the limit of large Q-values. Moreover, pore volumes estimated by the N 2 and CO 2 adsorption, as well as via the mercury intrusion technique, have been compared with those measured by SANS/USANS, and possible reasons for the observed discrepancies are discussed.« less

Development of a simultaneous SANS / FTIR measuring system and its application to polymer cocrystals

NASA Astrophysics Data System (ADS)

Kaneko, F.; Seto, N.; Sato, S.; Radulescu, A.; Schiavone, M. M.; Allgaier, J.; Ute, K.

2016-09-01

In order to provide plenty of structure information which would assist in the analysis and interpretation of small angle neutron scattering (SANS) profile, a novel method for the simultaneous time-resolved measurement of SANS and Fourier transform infrared (FTIR) spectroscopy has been developed. The method was realized by building a device consisting of a portable FTIR spectrometer and an optical system equipped with two aluminum coated quartz plates that are fully transparent to neutron beams but play as mirrors for infrared radiation. The optical system allows both a neutron beam and an infrared beam pass through the same position of a test specimen coaxially. The device was installed on a small angle neutron diffractometer, KWS2 of the Jülich Centre for Neutron Science (JCNS) outstation at Heinz Maier-Leibnitz Center (MLZ) in Garching, Germany. In order to check the performance of this simultaneous measuring system, the structural changes in the cocrystals of syndiotactic polystyrene during the course of heating were followed. It has been confirmed that FTIR spectra measured in parallel are able to provide information about the behavior of each component and also useful to grasp in real time what is actually happening in the sample system.

Forward Helion Scattering and Neutron Polarization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buttimore, N. H.

The elastic scattering of spin half helium-3 nuclei at small angles can show a sufficiently large analyzing power to enable the level of helion polarization to be evaluated. As the helion to a large extent inherits the polarization of its unpaired neutron the asymmetry observed in helion collisions can be transformed into a measurement of the polarization of its constituent neutron. Neutron polarimetry therefore relies upon understanding the spin dependence of the electromagnetic and hadronic interactions in the region of interference where there is an optimal analyzing power.

Prototype of the novel CAMEA concept—A backend for neutron spectrometers

NASA Astrophysics Data System (ADS)

Markó, Márton; Groitl, Felix; Birk, Jonas Okkels; Freeman, Paul Gregory; Lefmann, Kim; Christensen, Niels Bech; Niedermayer, Christof; Jurányi, Fanni; Lass, Jakob; Hansen, Allan; Rønnow, Henrik M.

2018-01-01

The continuous angle multiple energy analysis concept is a backend for both time-of-flight and analyzer-based neutron spectrometers optimized for neutron spectroscopy with highly efficient mapping in the horizontal scattering plane. The design employs a series of several upward scattering analyzer arcs placed behind each other, which are set to different final energies allowing a wide angular coverage with multiple energies recorded simultaneously. For validation of the concept and the model calculations, a prototype was installed at the Swiss neutron source SINQ, Paul Scherrer Institut. The design of the prototype, alignment and calibration procedures, experimental results of background measurements, and proof-of-concept inelastic measurements on LiHoF4 and h-YMnO3 are presented here.

Small-Angle Neutron Scattering on Crosslink Distribution of Epoxy Networks.

DTIC Science & Technology

1985-10-01

distinct second phase or heterogeneity has been detected. Small- angle X-ray scattering (SAXS), 1 nuclear magnetic resonance (NMR) ,2 electron ... paramagnetic resonance (EPR),3 and glass transition 4temperature (Tg) measurements reveal a second phase which is attri- . buted to a heterogeneous...FUNDING/SPONSORING lab. OFFICE SYMBOL 9. PROCUREMENT INSTRUMENT IDENTIFICATION NUMBER * ORGANIZATION I (If applticable)j F3361 5-84-C-5020 * Bc ADDRESS

Fast, quantitative, and nondestructive evaluation of hydrided LWR fuel cladding by small angle incoherent neutron scattering of hydrogen

DOE PAGES

Yan, Y.; Qian, S.; Littrell, K.; ...

2015-02-13

A non-destructive neutron scattering method to precisely measure the uptake of hydrogen and the distribution of hydride precipitates in light water reactor (LWR) fuel cladding was developed. Zircaloy-4 cladding used in commercial LWRs was used to produce hydrided specimens. The hydriding apparatus consists of a closed stainless steel vessel that contains Zr alloy specimens and hydrogen gas. Following hydrogen charging, the hydrogen content of the hydrided specimens was measured using the vacuum hot extraction method, by which the samples with desired hydrogen concentration were selected for the neutron study. Optical microscopy shows that our hydriding procedure results in uniform distributionmore » of circumferential hydrides across the wall. Small angle neutron incoherent scattering was performed in the High Flux Isotope Reactor at Oak Ridge National Laboratory. This study demonstrates that the hydrogen in commercial Zircaloy-4 cladding can be measured very accurately in minutes by this nondestructive method over a wide range of hydrogen concentrations from a very small amount ( 20 ppm) to over 1000 ppm. The hydrogen distribution in a tube sample was obtained by scaling the neutron scattering rate with a factor determined by a calibration process using standard, destructive direct chemical analysis methods on the specimens. This scale factor will be used in future tests with unknown hydrogen concentrations, thus providing a nondestructive method for absolute hydrogen concentration determination.« less

Recent advances in polarized 3 He based neutron spin filter development

NASA Astrophysics Data System (ADS)

Chen, Wangchun; Gentile, Thomas; Erwin, Ross; Watson, Shannon; Krycka, Kathryn; Ye, Qiang; NCNR NIST Team; University of Maryland Team

2015-04-01

Polarized 3 He neutron spin filters (NSFs) are based on the strong spin-dependence of the neutron absorption cross section by 3 He. NSFs can polarize large area, widely divergent, and broadband neutron beams effectively and allow for combining a neutron polarizer and a spin flipper into a single polarizing device. The last capability utilizes 3 He spin inversion based on the adiabatic fast passage (AFP) nuclear magnetic resonance technique. Polarized 3 He NSFs are significantly expanding the polarized neutron measurement capabilities at the NIST Center for Neutron Research (NCNR). Here we present an overview of 3 He NSF applications to small-angle neutron scattering, thermal triple axis spectrometry, and wide-angle polarization analysis. We discuss a recent upgrade of our spin-exchange optical pumping (SEOP) systems that utilize chirped volume holographic gratings for spectral narrowing. The new capability allows us to polarize rubidium/potassium hybrid SEOP cells over a liter in volume within a day, with 3 He polarizations up to 88%, Finally we discuss how we can achieve nearly lossless 3 He polarization inversion with AFP.

Detection of vapor nanobubbles by small angle neutron scattering (SANS)

NASA Astrophysics Data System (ADS)

Popov, Emilian; He, Lilin; Dominguez-Ontiveros, Elvis; Melnichenko, Yuri

2018-04-01

Experiments using boiling water on untreated (roughness 100-300 nm) metal surfaces using small-angle neutron scattering (SANS) show the appearance of structures that are 50-70 nm in size when boiling is present. The scattering signal disappears when the boiling ceases, and no change in the signal is detected at any surface temperature condition below saturation. This confirms that the signal is caused by vapor nanobubbles. Two boiling regimes are evaluated herein that differ by the degree of subcooling (3-10 °C). A polydisperse spherical model with a log-normal distribution fits the SANS data well. The size distribution indicates that a large number of nanobubbles exist on the surface during boiling, and some of them grow into large bubbles.

A microstructural comparison of two nuclear-grade martensitic steels using small-angle neutron scattering

NASA Astrophysics Data System (ADS)

Coppola, R.; Fiori, F.; Little, E. A.; Magnani, M.

1997-06-01

Results are presented of a small-angle neutron scattering (SANS) study on two 10-13% Cr martensitic stainless steels of interest for nuclear applications, viz. DIN 1.4914 (MANET specification, for fusion reactors) and AISI 410. The investigation has focussed principally on microstructural effects associated with the differences in chromium content between the two alloys. The size distribution functions determined from nuclear and magnetic SANS components for the two steels given identical heat treatments are in accord with an interpretation based on the presence of ˜ 1 nm size CCr aggregates in the microstructure. Much larger (˜ 10 nm) scattering inhomogeneities with different magnetic contrast are also present and tentatively identified as carbides.

Structures and interactions among globular proteins above the isoelectric point in the presence of divalent ions: A small angle neutron scattering and dynamic light scattering study

NASA Astrophysics Data System (ADS)

Kundu, Sarathi; Pandit, Subhankar; Abbas, Sohrab; Aswal, V. K.; Kohlbrecher, J.

2018-02-01

Small angle neutron scattering study reveals that at pD ≈ 7.0, above the isoelectric point of the globular protein Bovine Serum Albumin (BSA), in the presence of different divalent ions (Mg2+, Ca2+, Sr2+ and Ba2+), the short-range attractive interaction remains nearly constant and the intermediate-range repulsive interaction decreases with increasing salt concentration up to a certain concentration value but after that remains unchanged. However, for the monovalent ion (Na+), repulsive interaction decreases gradually up to 1 M salt concentration. Dynamic light scattering study shows that for all ions, diffusion coefficient of BSA decreases with increasing salt concentration and then nearly saturates.

Characterization of oligomerization of a peptide from the ebola virus glycoprotein by small-angle neutron scattering

NASA Astrophysics Data System (ADS)

Egorov, V. V.; Gorshkov, A. N.; Murugova, T. N.; Vasin, A. V.; Lebedev, D. V.; Isaev-Ivanov, V. V.; Kiselev, O. I.

2016-01-01

Transmission electron microscopy (TEM) and small-angle neutron scattering (SANS) studies showed that model peptides QNALVCGLRQ (G33) and QNALVCGLRG (G31) corresponding to region 551-560 of the GP protein of the Sudan Ebola virus are prone to oligomerization in solution. Both peptides can form amyloid-like fibrills. The G33 peptide forms fibrils within one day of incubation, whereas the fibrillogenesis of the G31 peptide is observed only after incubation for several months. The possible role of the observed processes in the pathogenesis and the possibility of applying a combination of the TEM and SANS techniques to search for new compounds that are able to influence the protein oligomerization are discussed.

Modified interactions among globular proteins below isoelectric point in the presence of mono-, di- and tri-valent ions: A small angle neutron scattering study

NASA Astrophysics Data System (ADS)

Das, Kaushik; Kundu, Sarathi; Mehan, Sumit; Aswal, V. K.

2016-02-01

Both short range attraction and long range electrostatic repulsion exist among globular protein Bovine Serum Albumin in solution below its isoelectric point (pI ≈ 4.8). At pD ≈ 4.0, below pI, protein has a net positive surface charge although local charge inhomogeneity presents. Small angle neutron scattering study reveals that in the presence of both mono-(Na+) and di-(Ni2+) valent ions attractive interaction increases and repulsive interaction decreases with the increase of salt concentration. However, for tri-valent (Fe3+) ions, both attractive and repulsive interaction increases with increasing salt concentration but the relative strength of repulsion is more than the attraction.

Protein structure and interactions in the solid state studied by small-angle neutron scattering.

PubMed

Curtis, Joseph E; McAuley, Arnold; Nanda, Hirsh; Krueger, Susan

2012-01-01

Small-angle neutron scattering (SANS) is uniquely qualified to study the structure of proteins in liquid and solid phases that are relevant to food science and biotechnological applications. We have used SANS to study a model protein, lysozyme, in both the liquid and water ice phases to determine its gross-structure, interparticle interactions and other properties. These properties have been examined under a variety of solution conditions before, during, and after freezing. Results for lysozyme at concentrations of 50 mg mL(-1) and 100 mg mL(-1), with NaCl concentrations of 0.4 M and 0 M, respectively, both in the liquid and frozen states, are presented and implications for food science are discussed.

SUSANS With Polarized Neutrons

PubMed Central

Wagh, Apoorva G.; Rakhecha, Veer Chand; Strobl, Makus; Treimer, Wolfgang

2005-01-01

Super Ultra-Small Angle Neutron Scattering (SUSANS) studies over wave vector transfers of 10–4 nm–1 to 10–3 nm–1 afford information on micrometer-size agglomerates in samples. Using a right-angled magnetic air prism, we have achieved a separation of ≈10 arcsec between ≈2 arcsec wide up- and down-spin peaks of 0.54 nm neutrons. The SUSANS instrument has thus been equipped with the polarized neutron option. The samples are placed in a uniform vertical field of 8.8 × 104 A/m (1.1 kOe). Several magnetic alloy ribbon samples broaden the up-spin neutron peak significantly over the ±1.3 × 10–3 nm–1 range, while leaving the down-spin peak essentially unaltered. Fourier transforms of these SUSANS spectra corrected for the instrument resolution, yield micrometer-range pair distribution functions for up- and down-spin neutrons as well as the nuclear and magnetic scattering length density distributions in the samples. PMID:27308127

In-situ temperature-controllable shear flow device for neutron scattering measurement—An example of aligned bicellar mixtures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xia, Yan; Li, Ming; Kučerka, Norbert

We have designed and constructed a temperature-controllable shear flow cell for in-situ study on flow alignable systems. The device has been tested in the neutron diffraction and has the potential to be applied in the small angle neutron scattering configuration to characterize the nanostructures of the materials under flow. The required sample amount is as small as 1 ml. The shear rate on the sample is controlled by the flow rate produced by an external pump and can potentially vary from 0.11 to 3.8 × 10{sup 5} s{sup −1}. Both unidirectional and oscillational flows are achievable by the setting ofmore » the pump. The instrument is validated by using a lipid bicellar mixture, which yields non-alignable nanodisc-like bicelles at low T and shear-alignable membranes at high T. Using the shear cell, the bicellar membranes can be aligned at 31 °C under the flow with a shear rate of 11.11 s{sup −1}. Multiple high-order Bragg peaks are observed and the full width at half maximum of the “rocking curve” around the Bragg’s condition is found to be 3.5°–4.1°. It is noteworthy that a portion of the membranes remains aligned even after the flow stops. Detailed and comprehensive intensity correction for the rocking curve has been derived based on the finite rectangular sample geometry and the absorption of the neutrons as a function of sample angle [See supplementary material at http://dx.doi.org/10.1063/1.4908165 for the detailed derivation of the absorption correction]. The device offers a new capability to study the conformational or orientational anisotropy of the solvated macromolecules or aggregates induced by the hydrodynamic interaction in a flow field.« less

NIMROD: The Near and InterMediate Range Order Diffractometer of the ISIS second target station.

PubMed

Bowron, D T; Soper, A K; Jones, K; Ansell, S; Birch, S; Norris, J; Perrott, L; Riedel, D; Rhodes, N J; Wakefield, S R; Botti, A; Ricci, M-A; Grazzi, F; Zoppi, M

2010-03-01

NIMROD is the Near and InterMediate Range Order Diffractometer of the ISIS second target station. Its design is optimized for structural studies of disordered materials and liquids on a continuous length scale that extends from the atomic, upward of 30 nm, while maintaining subatomic distance resolution. This capability is achieved by matching a low and wider angle array of high efficiency neutron scintillation detectors to the broad band-pass radiation delivered by a hybrid liquid water and liquid hydrogen neutron moderator assembly. The capabilities of the instrument bridge the gap between conventional small angle neutron scattering and wide angle diffraction through the use of a common calibration procedure for the entire length scale. This allows the instrument to obtain information on nanoscale systems and processes that are quantitatively linked to the local atomic and molecular order of the materials under investigation.

Validating the performance of correlated fission multiplicity implementation in radiation transport codes with subcritical neutron multiplication benchmark experiments

DOE PAGES

Arthur, Jennifer; Bahran, Rian; Hutchinson, Jesson; ...

2018-06-14

Historically, radiation transport codes have uncorrelated fission emissions. In reality, the particles emitted by both spontaneous and induced fissions are correlated in time, energy, angle, and multiplicity. This work validates the performance of various current Monte Carlo codes that take into account the underlying correlated physics of fission neutrons, specifically neutron multiplicity distributions. The performance of 4 Monte Carlo codes - MCNP®6.2, MCNP®6.2/FREYA, MCNP®6.2/CGMF, and PoliMi - was assessed using neutron multiplicity benchmark experiments. In addition, MCNP®6.2 simulations were run using JEFF-3.2 and JENDL-4.0, rather than ENDF/B-VII.1, data for 239Pu and 240Pu. The sensitive benchmark parameters that in this workmore » represent the performance of each correlated fission multiplicity Monte Carlo code include the singles rate, the doubles rate, leakage multiplication, and Feynman histograms. Although it is difficult to determine which radiation transport code shows the best overall performance in simulating subcritical neutron multiplication inference benchmark measurements, it is clear that correlations exist between the underlying nuclear data utilized by (or generated by) the various codes, and the correlated neutron observables of interest. This could prove useful in nuclear data validation and evaluation applications, in which a particular moment of the neutron multiplicity distribution is of more interest than the other moments. It is also quite clear that, because transport is handled by MCNP®6.2 in 3 of the 4 codes, with the 4th code (PoliMi) being based on an older version of MCNP®, the differences in correlated neutron observables of interest are most likely due to the treatment of fission event generation in each of the different codes, as opposed to the radiation transport.« less

Validating the performance of correlated fission multiplicity implementation in radiation transport codes with subcritical neutron multiplication benchmark experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arthur, Jennifer; Bahran, Rian; Hutchinson, Jesson

Historically, radiation transport codes have uncorrelated fission emissions. In reality, the particles emitted by both spontaneous and induced fissions are correlated in time, energy, angle, and multiplicity. This work validates the performance of various current Monte Carlo codes that take into account the underlying correlated physics of fission neutrons, specifically neutron multiplicity distributions. The performance of 4 Monte Carlo codes - MCNP®6.2, MCNP®6.2/FREYA, MCNP®6.2/CGMF, and PoliMi - was assessed using neutron multiplicity benchmark experiments. In addition, MCNP®6.2 simulations were run using JEFF-3.2 and JENDL-4.0, rather than ENDF/B-VII.1, data for 239Pu and 240Pu. The sensitive benchmark parameters that in this workmore » represent the performance of each correlated fission multiplicity Monte Carlo code include the singles rate, the doubles rate, leakage multiplication, and Feynman histograms. Although it is difficult to determine which radiation transport code shows the best overall performance in simulating subcritical neutron multiplication inference benchmark measurements, it is clear that correlations exist between the underlying nuclear data utilized by (or generated by) the various codes, and the correlated neutron observables of interest. This could prove useful in nuclear data validation and evaluation applications, in which a particular moment of the neutron multiplicity distribution is of more interest than the other moments. It is also quite clear that, because transport is handled by MCNP®6.2 in 3 of the 4 codes, with the 4th code (PoliMi) being based on an older version of MCNP®, the differences in correlated neutron observables of interest are most likely due to the treatment of fission event generation in each of the different codes, as opposed to the radiation transport.« less

Neutrons measure phase behavior in pores at Angstrom size

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bardoel, Agatha A; Melnichenko, Yuri B

Researchers have measured the phase behavior of green house gases in pores at the Angstrom-level, using small angle neutron scattering (SANS) at the Oak Ridge National Laboratory's High Flux Isotope Reactor. Yuri Melnichenko, an instrument scientist on the General Purpose Small Angle Neutron Scattering (GP SANS) Diffractometer at ORNL's High Flux Isotope Reactor, his postdoctoral associate Lilin He and collaborators Nidia Gallego and Cristian Contescu from the Material Sciences Division (ORNL) were engaged in the work. They were studying nanoporous carbons to assess their attractiveness as storage media for hydrogen, with a view to potential use for on-board hydrogen storagemore » for transportation applications. Nanoporous carbons can also serve as electrode material for supercapacitors and batteries. The researchers successfully determined that the most efficiently condensing pore size in a carbon nanoporous material for hydrogen storage is less than one nanometer. In a paper recently published by the Journal of the American Chemical Society, the collaborators used small angle neutron scattering to study how hydrogen condenses in small pores at ambient temperature. They discovered that the surface-molecule interactions create internal pressures in pores that may exceed the external gas pressure by a factor of up to 50. 'This is an exciting result,' Melnichenko said, 'as you achieve extreme densification in pores 'for free', i.e. without spending any energy. These results can be used to guide the development of new carbon adsorbents tailored to maximize hydrogen storage capacities.' Another important factor that defines the adsorption capacity of sub-nanometer pores is their shape. In order to get accurate structural information and maximize sorption capacity, it is important that pores are small and of approximately uniform size. In collaboration with Drexel University's Yury Gogotsi who supplied the samples, Melnichenko and his collaborators used the GP SANS instrument to study how the size and shape of pores in sub-nanometer porous carbons varies, depending on the manufacturing conditions. While small angle X-ray scattering (SAXS) can do the job too, Melnichenko says, the SANS method broke new ground in analyzing the shape and behavior of pores at subnanometer size, when subjected to varying synthesis temperature. 'We found that these very small pores are in fact spherical, and that when we change the synthesis conditions, they become elongated, even 'slit-like', and all of this on a subnanometer scale,' Melnichenko said.« less

Hierarchical Pore Morphology of Cretaceous Shale: A Small-Angle Neutron Scattering and Ultrasmall-Angle Neutron Scattering Study

DOE PAGES

Bahadur, J.; Melnichenko, Y. B.; Mastalerz, Maria; ...

2014-09-25

Shale reservoirs are becoming an increasingly important source of oil and natural gas supply and a potential candidate for CO 2 sequestration. Understanding the pore morphology in shale may provide clues to making gas extraction more efficient and cost-effective. The porosity of Cretaceous shale samples from Alberta, Canada, collected from different depths with varying mineralogical compositions, has been investigated by small- and ultrasmall-angle neutron scattering. Moreover these samples come from the Second White Specks and Belle Fourche formations, and their organic matter content ranges between 2 and 3%. The scattering length density of the shale specimens has been estimated usingmore » the chemical composition of the different mineral components. Scattering experiments reveal the presence of fractal and non-fractal pores. It has been shown that the porosity and specific surface area are dominated by the contribution from meso- and micropores. The fraction of closed porosity has been calculated by comparing the porosities estimated by He pycnometry and scattering techniques. There is no correlation between total porosity and mineral components, a strong correlation has been observed between closed porosity and major mineral components in the studied specimens.« less

The Denaturation Transition of DNA in Mixed Solvents

PubMed Central

Hammouda, Boualem; Worcester, David

2006-01-01

The helix-to-coil denaturation transition in DNA has been investigated in mixed solvents at high concentration using ultraviolet light absorption spectroscopy and small-angle neutron scattering. Two solvents have been used: water and ethylene glycol. The “melting” transition temperature was found to be 94°C for 4% mass fraction DNA/d-water and 38°C for 4% mass fraction DNA/d-ethylene glycol. The DNA melting transition temperature was found to vary linearly with the solvent fraction in the mixed solvents case. Deuterated solvents (d-water and d-ethylene glycol) were used to enhance the small-angle neutron scattering signal and 0.1M NaCl (or 0.0058 g/g mass fraction) salt concentration was added to screen charge interactions in all cases. DNA structural information was obtained by small-angle neutron scattering, including a correlation length characteristic of the inter-distance between the hydrogen-containing (desoxyribose sugar-amine base) groups. This correlation length was found to increase from 8.5 to 12.3 Å across the melting transition. Ethylene glycol and water mixed solvents were found to mix randomly in the solvation region in the helix phase, but nonideal solvent mixing was found in the melted coil phase. In the coil phase, solvent mixtures are more effective solvating agents than either of the individual solvents. Once melted, DNA coils behave like swollen water-soluble synthetic polymer chains. PMID:16815902

Structured water in polyelectrolyte dendrimers: Understanding small angle neutron scattering results through atomistic simulation

NASA Astrophysics Data System (ADS)

Wu, Bin; Kerkeni, Boutheïna; Egami, Takeshi; Do, Changwoo; Liu, Yun; Wang, Yongmei; Porcar, Lionel; Hong, Kunlun; Smith, Sean C.; Liu, Emily L.; Smith, Gregory S.; Chen, Wei-Ren

2012-04-01

Based on atomistic molecular dynamics (MD) simulations, the small angle neutron scattering (SANS) intensity behavior of a single generation-4 polyelectrolyte polyamidoamine starburst dendrimer is investigated at different levels of molecular protonation. The SANS form factor, P(Q), and Debye autocorrelation function, γ(r), are calculated from the equilibrium MD trajectory based on a mathematical approach proposed in this work. The consistency found in comparison against previously published experimental findings (W.-R. Chen, L. Porcar, Y. Liu, P. D. Butler, and L. J. Magid, Macromolecules 40, 5887 (2007)) leads to a link between the neutron scattering experiment and MD computation, and fresh perspectives. The simulations enable scattering calculations of not only the hydrocarbons but also the contribution from the scattering length density fluctuations caused by structured, confined water within the dendrimer. Based on our computational results, we explore the validity of using radius of gyration RG for microstructure characterization of a polyelectrolyte dendrimer from the scattering perspective.

Effect of annealing conditions on the microstructure and magnetic properties of sintered Nd-Fe-B magnets as seen by magnetic small-angle neutron scattering

NASA Astrophysics Data System (ADS)

Périgo, Élio A.; Titov, Ivan; Weber, Raoul; Mettus, Denis; Peral, Inma; Vallcorba, Oriol; Honecker, Dirk; Feoktystov, Artem; Michels, Andreas

2018-03-01

We have investigated the effect of the annealing conditions (heating rate and temperature) on the magnetic microstructure of sintered Nd-Fe-B magnets by means of magnetometry, scanning electron microscopy, high-energy synchrotron x-ray diffraction, and small-angle neutron scattering (SANS). While the temperature treatment has a strong effect on the coercivity (reduction by about 50% on annealing), the associated changes in the microstructure do surprisingly not show up (or at best only very weakly) in the neutron-scattering signal, which probes a mesoscopic real-space length scale ranging between about 1–300 nm. On the other hand, the x-ray data reveal microstructural changes in the Nd-rich phases, presumably due to modifications in grain-boundary regions. Moreover, we observe an unusual diamond-shaped angular anisotropy in the SANS cross section, which strongly points towards the existence of texture in the nuclear microstructure.

Small angle neutron scattering study of the gemini nonionic surfactant in heavy water solutions

NASA Astrophysics Data System (ADS)

Rajewska, A.

2012-03-01

The nonionic gemini surfactant α α'-[2,4,7,9-tetramethyl-5-decyne-4,7diyl]bis[ω hydroxyl-polyoxyethylene] (S-10) was investigated in heavy water solutions only for concentrations: 2.3%, 2.5%,3%, 3.4%, 4% and 5% at temperature 25°C with small angle neutron scattering (SANS) method. All of surfactants solutions were prepared using D2O (99.9% deuterated, Prikladnaia Chimia, St. Petersburg, Russia) as a solvent. The nonionic gemini surfactant S-10 was obtained from Air Products & Chemicals, Inc., and used without further purification. All SANS measurements were performed on V-4 SANS spectrometer at BENSC, Berlin (Germany). Neutrons were used in wavelength range of 0.02 - 4 nm-1. For the measurements quartz cells of were used during experiment. Up to 14 such cells were placed in a holder. Results from experiment was calculated and evaluated with PCG 2.0 program from Graz University (Austria). In the investigated solutions two axis ellipsoidal micelles was observed.

Non-destructive evaluation of nano-sized structure of thin film devices by using small angle neutron scattering.

PubMed

Shin, E J; Seong, B S; Choi, Y; Lee, J K

2011-01-01

Nano-sized multi-layers copper-doped SrZrO3, platinum (Pt) and silicon oxide (SiO2) on silicon substrates were prepared by dense plasma focus (DPF) device with the high purity copper anode tip and analyzed by using small angle neutron scattering (SANS) to establish a reliable method for the non-destructive evaluation of the under-layer structure. Thin film was well formed at the time-to-dip of 5 microsec with stable plasma of DPF. Several smooth intensity peaks were periodically observed when neutron beam penetrates the thin film with multi-layers perpendicularly. The platinum layer is dominant to intensity peaks, where the copper-doped SrZnO3 layer next to the platinum layer causes peak broadening. The silicon oxide layer has less effect on the SANS spectra due to its relative thick thickness. The SANS spectra shows thicknesses of platinum and copper-doped SrZnO3 layers as 53 and 25 nm, respectively, which are well agreement with microstructure observation.

Performance of SMARTer at Very Low Scattering Vector q-Range Revealed by Monodisperse Nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Putra, E. Giri Rachman; Ikram, A.; Bharoto

2008-03-17

A monodisperse nanoparticle sample of polystyrene has been employed to determine performance of the 36 meter small-angle neutron scattering (SANS) BATAN spectrometer (SMARTer) at the Neutron Scattering Laboratory (NSL)--Serpong, Indonesia, in a very low scattering vector q-range. Detector position at 18 m from sample position, beam stopper of 50 mm in diameter, neutron wavelength of 5.66 A as well as 18 m-long collimator had been set up to achieve very low scattering vector q-range of SMARTer. A polydisperse smeared-spherical particle model was applied to fit the corrected small-angle scattering data of monodisperse polystyrene nanoparticle sample. The mean average of particlemore » radius of 610 A, volume fraction of 0.0026, and polydispersity of 0.1 were obtained from the fitting results. The experiment results from SMARTer are comparable to SANS-J, JAEA - Japan and it is revealed that SMARTer is powerfully able to achieve the lowest scattering vector down to 0.002 A{sup -1}.« less

Bending moduli of microemulsions; comparison of results from small angle neutron scattering and neutron spin-echo spectroscopy

NASA Astrophysics Data System (ADS)

Monkenbusch, M.; Holderer, O.; Frielinghaus, H.; Byelov, D.; Allgaier, J.; Richter, D.

2005-08-01

The properties of bicontinuous microemulsions, consisting of water, oil and a surfactant, depend to a large extent on the bending moduli of the surfactant containing oil-water interface. In systems with CiEj as surfactant these moduli can be modified by the addition of diblock copolymers (boosting effect) and homopolymers (inverse boosting effect) or a combination of both. The influence of the addition of homopolymers (PEPX and PEOX, X = 5 or 10 kg/mol molecular weight) on the structure, bending modulus and dynamics of the surfactant layer is studied with small angle neutron scattering (SANS) and neutron spin-echo spectroscopy (NSE). Besides providing information on the microemulsion structure, neutron scattering is a microscopic probe that can be used to measure the local bending modulus κ. The polymer addition gives access to a homologous series of microemulsions with changing κ values. We relate the results obtained by analysis of SANS to those from NSE experiments. Comparison of the bending moduli obtained sheds light on the different renormalization length scales for NSE and SANS. Comparison of SANS and NSE derived κ values yields a consistent picture if renormalization properties are observed. Finally a ready to use method for converting NSE data into reliable values for κ is presented.

NIST Standard Reference Material 3600: Absolute Intensity Calibration Standard for Small-Angle X-ray Scattering

DOE PAGES

Allen, Andrew J.; Zhang, Fan; Kline, R. Joseph; ...

2017-03-07

The certification of a new standard reference material for small-angle scattering [NIST Standard Reference Material (SRM) 3600: Absolute Intensity Calibration Standard for Small-Angle X-ray Scattering (SAXS)], based on glassy carbon, is presented. Creation of this SRM relies on the intrinsic primary calibration capabilities of the ultra-small-angle X-ray scattering technique. This article describes how the intensity calibration has been achieved and validated in the certified Q range, Q = 0.008–0.25 Å –1, together with the purpose, use and availability of the SRM. The intensity calibration afforded by this robust and stable SRM should be applicable universally to all SAXS instruments thatmore » employ a transmission measurement geometry, working with a wide range of X-ray energies or wavelengths. As a result, the validation of the SRM SAXS intensity calibration using small-angle neutron scattering (SANS) is discussed, together with the prospects for including SANS in a future renewal certification.« less

NIST Standard Reference Material 3600: Absolute Intensity Calibration Standard for Small-Angle X-ray Scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allen, Andrew J.; Zhang, Fan; Kline, R. Joseph

The certification of a new standard reference material for small-angle scattering [NIST Standard Reference Material (SRM) 3600: Absolute Intensity Calibration Standard for Small-Angle X-ray Scattering (SAXS)], based on glassy carbon, is presented. Creation of this SRM relies on the intrinsic primary calibration capabilities of the ultra-small-angle X-ray scattering technique. This article describes how the intensity calibration has been achieved and validated in the certified Q range, Q = 0.008–0.25 Å –1, together with the purpose, use and availability of the SRM. The intensity calibration afforded by this robust and stable SRM should be applicable universally to all SAXS instruments thatmore » employ a transmission measurement geometry, working with a wide range of X-ray energies or wavelengths. As a result, the validation of the SRM SAXS intensity calibration using small-angle neutron scattering (SANS) is discussed, together with the prospects for including SANS in a future renewal certification.« less

NIST Standard Reference Material 3600: Absolute Intensity Calibration Standard for Small-Angle X-ray Scattering.

PubMed

Allen, Andrew J; Zhang, Fan; Kline, R Joseph; Guthrie, William F; Ilavsky, Jan

2017-04-01

The certification of a new standard reference material for small-angle scattering [NIST Standard Reference Material (SRM) 3600: Absolute Intensity Calibration Standard for Small-Angle X-ray Scattering (SAXS)], based on glassy carbon, is presented. Creation of this SRM relies on the intrinsic primary calibration capabilities of the ultra-small-angle X-ray scattering technique. This article describes how the intensity calibration has been achieved and validated in the certified Q range, Q = 0.008-0.25 Å -1 , together with the purpose, use and availability of the SRM. The intensity calibration afforded by this robust and stable SRM should be applicable universally to all SAXS instruments that employ a transmission measurement geometry, working with a wide range of X-ray energies or wavelengths. The validation of the SRM SAXS intensity calibration using small-angle neutron scattering (SANS) is discussed, together with the prospects for including SANS in a future renewal certification.

Characterization of oligomerization of a peptide from the ebola virus glycoprotein by small-angle neutron scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Egorov, V. V., E-mail: vlaegur@omrb.pnpi.spb.ru; Gorshkov, A. N.; Murugova, T. N.

2016-01-15

Transmission electron microscopy (TEM) and small-angle neutron scattering (SANS) studies showed that model peptides QNALVCGLRQ (G33) and QNALVCGLRG (G31) corresponding to region 551–560 of the GP protein of the Sudan Ebola virus are prone to oligomerization in solution. Both peptides can form amyloid-like fibrills. The G33 peptide forms fibrils within one day of incubation, whereas the fibrillogenesis of the G31 peptide is observed only after incubation for several months. The possible role of the observed processes in the pathogenesis and the possibility of applying a combination of the TEM and SANS techniques to search for new compounds that are ablemore » to influence the protein oligomerization are discussed.« less

Small angle neutron scattering study on the structural variation of lysozyme in bioprotectants

NASA Astrophysics Data System (ADS)

Koda, Shota; Takayama, Haruki; Shibata, Tomohiko; Mori, Tatsuya; Kojima, Seiji; Park, In-Sung; Shin, Tae-Gyu

2015-05-01

The thermal denaturation and subsequent structural variation of lysozyme in various bioprotectant candidate solutions such as trehalose and choline acetate have been investigated by using small angle neutron scattering and differential scanning calorimetry. The gyration radius shows little change with the addition of additives in a native state at room temperature. On heating the lysozyme solution, a remarkable increase in the gyration radius is observed at temperatures above the denaturation temperature without any bioprotectants. Such an increase is suppressed by the additives owing to the intermolecular interactions between the lysozyme molecules and the bioprotectants of trehalose and choline acetate. The fractal dimension of lysozyme varies slightly with the addition of the bioprotectant solutions, and shows a remarkable drop in the vicinity of the denaturation temperature for all the solutions.

Small-angle neutron scattering study of a monoclonal antibody using free-energy constraints.

PubMed

Clark, Nicholas J; Zhang, Hailiang; Krueger, Susan; Lee, Hyo Jin; Ketchem, Randal R; Kerwin, Bruce; Kanapuram, Sekhar R; Treuheit, Michael J; McAuley, Arnold; Curtis, Joseph E

2013-11-14

Monoclonal antibodies (mAbs) contain hinge-like regions that enable structural flexibility of globular domains that have a direct effect on biological function. A subclass of mAbs, IgG2, have several interchain disulfide bonds in the hinge region that could potentially limit structural flexibility of the globular domains and affect the overall configuration space available to the mAb. We have characterized human IgG2 mAb in solution via small-angle neutron scattering (SANS) and interpreted the scattering data using atomistic models. Molecular Monte Carlo combined with molecular dynamics simulations of a model mAb indicate that a wide range of structural configurations are plausible, spanning radius of gyration values from ∼39 to ∼55 Å. Structural ensembles and representative single structure solutions were derived by comparison of theoretical SANS profiles of mAb models to experimental SANS data. Additionally, molecular mechanical and solvation free-energy calculations were carried out on the ensemble of best-fitting mAb structures. The results of this study indicate that low-resolution techniques like small-angle scattering combined with atomistic molecular simulations with free-energy analysis may be helpful to determine the types of intramolecular interactions that influence function and could lead to deleterious changes to mAb structure. This methodology will be useful to analyze small-angle scattering data of many macromolecular systems.

Very High Reflectivity Supermirrors And Their Applications

NASA Astrophysics Data System (ADS)

Mezei, F.

1989-01-01

Very high reflectivity (some 95 % or better) supermirrors, with cut-off angles up to 2 times the critical angle of Ni coated simple total reflection neutron mirrors, can be produced using well established conventional deposition techniques. This performance makes applications involving multiple reflections and transmission geometries feasible, which in turn allow us to use more sophisticated neutron optical systems in order to optimize performance and minimize the amount a scarce supermirrors required. A key feature of several of these novel systems is the distribution of tasks between the several optical components achieving the desired performance by multiple action. The design and characteristics of a series of novel applications, such as polarizing cavities, collimators and guides, non-polarizing guides, beam compressors, deflectors and splitters (most of them tested or being implemented) are the main subjects of the present paper.

Neutron Star Natal Kick and Jets in Core Collapse Supernovae

NASA Astrophysics Data System (ADS)

Bear, Ealeal; Soker, Noam

2018-03-01

We measure the angle between the neutron star (NS) natal kick direction and the inferred direction of jets according to the morphology of 12 core collapse supernova remnants (SNR), and find that the distribution is almost random, but missing small angles. The 12 SNRs are those for which we could both identify morphological features that we can attribute to jets and for which the direction of the NS natal kick is given in the literature. Unlike some claims for spin-kick alignment, here we rule out jet-kick alignment. We discuss the cumulative distribution function of the jet-kick angles under the assumption that dense clumps that are ejected by the explosion accelerate the NS by the gravitational attraction, and suggest that the jet feedback explosion mechanism might in principle account for the distribution of jet-kick angles.

PREFACE: SANS-YuMO User Meeting at the Start-up of Scientific Experiments on the IBR-2M Reactor: Devoted to the 75th anniversary of Yu M Ostanevich's birth

NASA Astrophysics Data System (ADS)

Gordely, Valentin; Kuklin, Alexander; Balasoiu, Maria

2012-03-01

The Second International Workshop 'SANS-YuMO User Meeting at the Start-up of Scientific Experiments on the IBR-2M Reactor', devoted to the 75th anniversary of the birth of Professor Yu M Ostanevich (1936-1992), an outstanding neutron physicist and the founder of small-angle neutron scattering (field, group, and instrument) at JINR FLNPh, was held on 27-30 May at the Frank Laboratory of Neutron Physics. The first Workshop was held in October 2006. Research groups from different neutron centers, universities and research institutes across Europe presented more than 35 oral and poster presentations describing scientific and methodological results. Most of them were obtained with the help of the YuMO instrument before the IBR-2 shutdown in 2006. For the last four years the IBR-2 reactor has been shut down for refurbishment. At the end of 2010 the physical launch of the IBR-2M reactor was finally realized. Nowadays the small-angle neutron scattering (SANS) technique is applied to a wide range of scientific problems in condensed matter, soft condensed matter, biology and nanotechnology, and despite the fact that there are currently over 30 SANS instruments in operation worldwide at both reactor and spallation sources, the demand for beam-time is considerably higher than the time available. It must be remembered, however, that as the first SANS machine on a steady-state reactor was constructed at the Institute Laue Langevin, Grenoble, the first SANS instrument on a 'white' neutron pulsed beam was accomplished at the Joint Institute for Nuclear Research at the IBR-30 reactor, beamline N5. During the meeting Yu M Ostanevich's determinative and crucial contribution to the construction of spectrometers at the IBR-2 high-pulsed reactor was presented, as well as his contribution to the development of the time-of-flight (TOF) small-angle scattering technique, and a selection of other scientific areas. His leadership and outstanding scientific achievements in applications of the Mossbauer effect in physics and chemistry, in SANS studies of polyelectrolytes, small molecules, fractals, metallic glasses, macromolecules, polymers, etc., were recognized by a number of awards including the State Prize of the Russian Federation in 2000. The scientific program of the workshop focused on fundamental and methodical research at the YuMO spectrometer and developments of the SANS instrument at the modernized IBR-2M reactor. We recall that the acronym YuMO of the small-angle neutron scattering spectrometer (MURN), was given in honor of Yu M Ostanevich. One of the most important objectives of this user meeting was to discuss the further development possibilities of the YuMO spectrometer with experts, in the frame of a SANS YuMO Round Table, taking into account the specific performance of the modernized YuMO SANS instrument, and the scientific and technical requests of the instrument's users. Highlights on modern achievements in nanoscience, polymers and biology were other significant goals of the meeting. The plenary invited talks were presented by leading scientists in small-angle neutron scattering and soft condensed matter, including members of the Russian Academy of Sciences: Prof. Heinrich Stuhrmann, Prof. Alexei Khokhlov, Prof. Jose Teixeira, Prof. Alexander Ozerin, Prof. Albrecht Wiedenmann, etc. There were 27 oral talks given and 32 posters presented by 92 participants from 12 countries: Czech Republic, Egypt, France, Germany, Hungary, Moldova, Mongolia, Poland, Romania, Russian Federation, Slovak Republic, and Ukraine. The workshop was organized with the financial support of the Frank Laboratory of Neutron Physics (Joint Institute for Nuclear Research), Horia Hulubei National Institute of Physics and Nuclear Engineering - IFIN HH (Romania), Institute of Macromolecular Chemistry AS CR (Czech Republic), and Comenius University (Slovakia). V Gordeliy, A Kuklin and M Balasoiu SANSgroup Participants of the meeting The PDF also contains additional photographs from the meeting.

Small-angle neutron scattering study of the short-range organization of dispersed CsNi[Cr(CN){sub 6}] nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ridier, Karl; Gillon, Béatrice; André, Gilles

2015-09-21

Prussian blue analogues magnetic nanoparticles (of radius R{sub 0} = 2.4–8.6 nm) embedded in PVP (polyvinylpyrrolidone) or CTA{sup +} (cetyltrimethylammonium) matrices have been studied using neutron diffraction and small angle neutron scattering (SANS) at several concentrations. For the most diluted particles in neutral PVP, the SANS signal is fully accounted for by a “single-particle” spherical form factor with no structural correlations between the nanoparticles and with radii comparable to those inferred from neutron diffraction. For higher concentration in PVP, structural correlations modify the SANS signal with the appearance of a structure factor peak, which is described using an effective “mean-field” model. A newmore » length scale R{sup * }≈ 3R{sub 0}, corresponding to an effective repulsive interaction radius, is evidenced in PVP samples. In CTA{sup +}, electrostatic interactions play a crucial role and lead to a dense layer of CTA{sup +} around the nanoparticles, which considerably alter the SANS patterns as compared to PVP. The SANS data of nanoparticles in CTA{sup +} are best described by a core-shell model without visible inter-particle structure factor.« less

Cosmic Rays In The Magnetosphere, 2. Apparent Cut-off Rigidities and Coupling Functions

NASA Astrophysics Data System (ADS)

Dorman, L. I.; Danilova, O. A.; Iucci, N.; Parisi, M.; Ptitsyna, N. G.; Tyasto, M. I.; Villoresi, G.

We calculate the apparent cut-off rigidities along the survey Italy-Antarctica-Italy** on the basis of results of Danilova et al. (2001) on trajectory calculations for inclined cut- off rigidities at eight azimuths (through 45?) and five zeniths angles (through 15?) along the survey. For calculations of apparent cut-off rigidities we use also the infor- mation on integral multiplicities of secondary neutrons in dependence of zenith angle of incident primary cosmic ray particles, as theoretically computed. This information is based on the theoretical calculations of meson-nuclear cascades for primary protons with different rigidities arriving to the EarthSs atmosphere at different zenith angles (Dorman and Pakhomov, 1979). These results have been checked and normalized by using coupling functions obtained in the same survey [Dorman et al. (2000)]. The determined apparent cut-off rigidities have been compared with results obtained by Clem et al. (1997) and with those used by Dorman et al. (2000) computed by using vertical cut-off rigidities, for trajectories especially calculated for the survey. On the basis of the apparent cut-off rigidities along the latitude survey, the coupling functions for neutron monitor and bare neutron counters found by Dorman et al. (2000) are now determined more accurately. **Survey realized with logistic and financial support of the Italian Antarctic Program (PNRA) and with the co-operation of IFSI-CNR. REFERENCES: Clem, J.M., et al. J. Geophys. Res., 102, 26,919 (1997). Danilova, O.A., et al., Latitude survey in December 1996-March 1997, 1. Cut-off rigidities for different azimuth and zenith angles, Paper ST13, This issue (2001) Dorman L.I. and Pakhomov N.I., "The dependence of the integral generation multiplicity of neutron component at various depths in the atmosphere on zenith angle on primary particle in- cidence". Proc. 16-th ICRC, Kyoto, 4, 416-420 (1979) Dorman, L.I., et al., J. Geophys. Res. 105 , 21,047 (2000).

Detection of submicron-sized raft-like domains in membranes by small-angle neutron scattering

NASA Astrophysics Data System (ADS)

Pencer, J.; Mills, T.; Anghel, V.; Krueger, S.; Epand, R. M.; Katsaras, J.

2005-12-01

Using coarse grained models of heterogeneous vesicles we demonstrate the potential for small-angle neutron scattering (SANS) to detect and distinguish between two different categories of lateral segregation: 1) unilamellar vesicles (ULV) containing a single domain and 2) the formation of several small domains or “clusters” (~10 nm in radius) on a ULV. Exploiting the unique sensitivity of neutron scattering to differences between hydrogen and deuterium, we show that the liquid ordered (lo) DPPC-rich phase can be selectively labeled using chain deuterated dipalymitoyl phosphatidylcholine (dDPPC), which greatly facilitates the use of SANS to detect membrane domains. SANS experiments are then performed in order to detect and characterize, on nanometer length scales, lateral heterogeneities, or so-called “rafts”, in ~30 nm radius low polydispersity ULV made up of ternary mixtures of phospholipids and cholesterol. For 1:1:1 DOPC:DPPC:cholesterol (DDC) ULV we find evidence for the formation of lateral heterogeneities on cooling below 30 °C. These heterogeneities do not appear when DOPC is replaced by SOPC. Fits to the experimental data using coarse grained models show that, at room temperature, DDC ULV each exhibit approximately 30 domains with average radii of ~10 nm.

Visualization of oil behavior in a small 4-cycle engine with electrical motoring by neutron radiography

NASA Astrophysics Data System (ADS)

Nakamura, M.; Sugimoto, K.; Asano, H.; Murakawa, H.; Takenaka, N.; Mochiki, K.

2009-06-01

Neutron radiography is suitable for the visualization of liquid behavior in a metallic machine. Observation of oil behavior in a small 4-cycle engine on operating was carried out by using the neutron radiography facility at JRR-3 in JAEA. The engine was not fired but operated by an electrical motor. Movies were taken by a neutron image intensifier with a color CCD camera of 8-bit resolution, 30 frames/s and 640×480 pixels developed by Toshiba Corp. The engine was placed on a turn table and was rotated, so the movie could be taken from any angle. Numbers of revolution of the engine were changed from 260 to 1200 rpm. Visualized images of the mechanism and the oil behavior in the engine were obtained.

Neutron Capture Experiments Using the DANCE Array at Los Alamos

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dashdorj, D.; MonAme Scientific Research Center, Ulaanbaatar; Mitchell, G. E.

2009-03-31

The Detector for Advanced Neutron Capture Experiments (DANCE) is designed for neutron capture measurements on very small and/or radioactive targets. The DANCE array of 160 BaF{sub 2} scintillation detectors is located at the Lujan Center at the Los Alamos Neutron Science Center (LANSCE). Accurate measurements of neutron capture data are important for many current applications as well as for basic understanding of neutron capture. The gamma rays following neutron capture reactions have been studied by the time-of-flight technique using the DANCE array. The high granularity of the array allows measurements of the gamma-ray multiplicity. The gamma-ray multiplicities and energy spectramore » for different multiplicities can be measured and analyzed for spin and parity determination of the resolved resonances.« less

Effects of macromolecular crowding on the structure of a protein complex: A small-angle scattering study of superoxide dismutase

DOE PAGES

Rajapaksha, Ajith; Stanley, Christopher B.; Todd, Brian A.

2015-02-17

Macromolecular crowding can alter the structure and function of biological macromolecules. We used small angle scattering (SAS) to measure the change in size of a protein complex, superoxide dismutase (SOD), induced by macromolecular crowding. Crowding was induced using 400 MW polyethylene glycol (PEG), triethylene glycol (TEG), methyl- -glucoside ( -MG) and trimethylamine N-oxide (TMAO). Parallel small angle neutron scattering (SANS) and small angle x-ray scattering (SAXS) allowed us to unambiguously attribute apparent changes in radius of gyration to changes in the structure of SOD. For a 40% PEG solution, we find that the volume of SOD was reduced by 9%.more » Considering the osmotic pressure due to PEG, this deformation corresponds to a highly compressible structure. SAXS done in the presence of TEG suggests that for further deformation beyond a 9% decrease in volume the resistance to deformation may increase dramatically.« less

Small-Angle X-ray Scattering (SAXS) Instrument Performance and Validation Using Silver Nanoparticles

DTIC Science & Technology

2016-12-01

Intercalibration of small-angle X- Ray and neutron-scattering data. Journal of Applied Crystallography . 1988;21:629–638. 7. Zhang F, Ilavsky J, Long GG...Materials Transactions A. 2009;41:1151–1158. 8. Kusz J, Bohm H. Performance of a confocal multilayer X-ray optic. Journal of Applied Crystallography ...Journal of Applied Crystallography . 2004;37:369–380. 10. Orthaber D, Bergmann A, Glatter O. SAXS experiments on absolute scale with Kratky systems using

Small Angle X ray Scattering (SAXS) Instrument Performance and Validation Using Silver Nanoparticles

DTIC Science & Technology

2016-12-01

Intercalibration of small-angle X- Ray and neutron-scattering data. Journal of Applied Crystallography . 1988;21:629–638. 7. Zhang F, Ilavsky J, Long GG...Materials Transactions A. 2009;41:1151–1158. 8. Kusz J, Bohm H. Performance of a confocal multilayer X-ray optic. Journal of Applied Crystallography ...Journal of Applied Crystallography . 2004;37:369–380. 10. Orthaber D, Bergmann A, Glatter O. SAXS experiments on absolute scale with Kratky systems using

Nodal gap structure and order parameter symmetry of the unconventional superconductor UPt₃

DOE PAGES

Gannon, W. J.; Halperin, W. P.; Rastovski, C.; ...

2015-02-01

Spanning a broad range of physical systems, complex symmetry breaking is widely recognized as a hallmark of competing interactions. This is exemplified in superfluid ³He which has multiple thermodynamic phases with spin and orbital quantum numbers S = 1 and L = 1, that emerge on cooling from a nearly ferromagnetic Fermi liquid. The heavy fermion compound UPt₃ exhibits similar behavior clearly manifest in its multiple superconducting phases. However, consensus as to its order parameter symmetry has remained elusive. Our small angle neutron scattering measurements indicate a linear temperature dependence of the London penetration depth characteristic of nodal structure ofmore » the order parameter. Our theoretical analysis is consistent with assignment of its symmetry to an L = 3 odd parity state for which one of the three thermodynamic phases in non-zero magnetic field is chiral.« less

Nodal gap structure and order parameter symmetry of the unconventional superconductor UPt₃

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gannon, W. J.; Halperin, W. P.; Rastovski, C.

Spanning a broad range of physical systems, complex symmetry breaking is widely recognized as a hallmark of competing interactions. This is exemplified in superfluid ³He which has multiple thermodynamic phases with spin and orbital quantum numbers S = 1 and L = 1, that emerge on cooling from a nearly ferromagnetic Fermi liquid. The heavy fermion compound UPt₃ exhibits similar behavior clearly manifest in its multiple superconducting phases. However, consensus as to its order parameter symmetry has remained elusive. Our small angle neutron scattering measurements indicate a linear temperature dependence of the London penetration depth characteristic of nodal structure ofmore » the order parameter. Our theoretical analysis is consistent with assignment of its symmetry to an L = 3 odd parity state for which one of the three thermodynamic phases in non-zero magnetic field is chiral.« less

Polyhydroxyalkanoate-based natural synthetic hybrid copolymer films: A small-angle neutron scattering study

NASA Astrophysics Data System (ADS)

Foster, L. John R.; Knott, Robert; Sanguanchaipaiwong, Vorapat; Holden, Peter J.

2006-11-01

Polyhydroxyalkanoates have attracted attention as biodegradable alternatives to conventional thermoplastics and as biomaterials. Through modification of their biosynthesis using Pseudomonas oleovorans, we have manipulated the material properties of these biopolyesters and produced a natural-synthetic hybrid copolymer of polyhydroxyoctanoate- block-diethylene glycol (PHO- b-DEG). A mixture of PHO and PHO-DEG were solvent cast from analytical grade chloroform and analysed using small-angle neutron scattering. A scattering pattern, easily distinguished above the background, was displayed by the films with a diffraction ring at q∼0.12 Å -1. This narrow ring of intensity is suggestive of a highly ordered system. Analysis of the diffraction pattern supported this concept and showed a d-spacing of approximately 50 Å. In addition, conformation of the hybrid polymer chains can be manipulated to support their self-assembly into ordered microporous films.

Evolution of the pore structure during the early stages of the alkali-activation reaction: An in situ small-angle neutron scattering investigation

DOE PAGES

White, Claire E.; Olds, Daniel P.; Hartl, Monika; ...

2017-02-01

The long-term durability of cement-based materials is influenced by the pore structure and associated permeability at the sub-micrometre length scale. With the emergence of new types of sustainable cements in recent decades, there is a pressing need to be able to predict the durability of these new materials, and therefore nondestructive experimental techniques capable of characterizing the evolution of the pore structure are increasingly crucial for investigating cement durability. Here, small-angle neutron scattering is used to analyze the evolution of the pore structure in alkali-activated materials over the initial 24 h of reaction in order to assess the characteristic poremore » sizes that emerge during these short time scales. By using a unified fitting approach for data modeling, information on the pore size and surface roughness is obtained for a variety of precursor chemistries and morphologies (metakaolin- and slag-based pastes). Furthermore, the impact of activator chemistry is elucidatedviathe analysis of pastes synthesized using hydroxide- and silicate-based activators. It is found that the main aspect influencing the size of pores that are accessible using small-angle neutron scattering analysis (approximately 10–500 Å in diameter) is the availability of free silica in the activating solution, which leads to a more refined pore structure with smaller average pore size. Furthermore, as the reaction progresses the gel pores visible using this scattering technique are seen to increase in size.« less

Conceptual design of the early implementation of the NEutron Detector Array (NEDA) with AGATA

NASA Astrophysics Data System (ADS)

Hüyük, Tayfun; Di Nitto, Antonio; Jaworski, Grzegorz; Gadea, Andrés; Javier Valiente-Dobón, José; Nyberg, Johan; Palacz, Marcin; Söderström, Pär-Anders; Jose Aliaga-Varea, Ramon; de Angelis, Giacomo; Ataç, Ayşe; Collado, Javier; Domingo-Pardo, Cesar; Egea, Francisco Javier; Erduran, Nizamettin; Ertürk, Sefa; de France, Gilles; Gadea, Rafael; González, Vicente; Herrero-Bosch, Vicente; Kaşkaş, Ayşe; Modamio, Victor; Moszynski, Marek; Sanchis, Enrique; Triossi, Andrea; Wadsworth, Robert

2016-03-01

The NEutron Detector Array (NEDA) project aims at the construction of a new high-efficiency compact neutron detector array to be coupled with large γ-ray arrays such as AGATA. The application of NEDA ranges from its use as selective neutron multiplicity filter for fusion-evaporation reaction to a large solid angle neutron tagging device. In the present work, possible configurations for the NEDA coupled with the Neutron Wall for the early implementation with AGATA has been simulated, using Monte Carlo techniques, in order to evaluate their performance figures. The goal of this early NEDA implementation is to improve, with respect to previous instruments, efficiency and capability to select multiplicity for fusion-evaporation reaction channels in which 1, 2 or 3 neutrons are emitted. Each NEDA detector unit has the shape of a regular hexagonal prism with a volume of about 3.23l and it is filled with the EJ301 liquid scintillator, that presents good neutron- γ discrimination properties. The simulations have been performed using a fusion-evaporation event generator that has been validated with a set of experimental data obtained in the 58Ni + 56Fe reaction measured with the Neutron Wall detector array.

Structure-Property Relationships of Architectural Coatings by Neutron Methods

NASA Astrophysics Data System (ADS)

Nakatani, Alan

2015-03-01

Architectural coatings formulations are multi-component mixtures containing latex polymer binder, pigment, rheology modifiers, surfactants, and colorants. In order to achieve the desired flow properties for these formulations, measures of the underlying structure of the components as a function of shear rate and the impact of formulation variables on the structure is necessary. We have conducted detailed measurements to understand the evolution under shear of local microstructure and larger scale mesostructure in model architectural coatings formulations by small angle neutron scattering (SANS) and ultra small angle neutron scattering (USANS), respectively. The SANS results show an adsorbed layer of rheology modifier molecules exist on the surface of the latex particles. However, the additional hydrodynamic volume occupied by the adsorbed surface layer is insufficient to account for the observed viscosity by standard hard sphere suspension models (Krieger-Dougherty). The USANS results show the presence of latex aggregates, which are fractal in nature. These fractal aggregates are the primary structures responsible for coatings formulation viscosity. Based on these results, a new model for the viscosity of coatings formulations has been developed, which is capable of reproducing the observed viscosity behavior.

X-ray and Neutron Scattering Study of the Formation of Core–Shell-Type Polyoxometalates

DOE PAGES

Yin, Panchao; Wu, Bin; Mamontov, Eugene; ...

2016-02-05

A typical type of core-shell polyoxometalates can be obtained through the Keggin-type polyoxometalate-templated growth of a layer of spherical shell structure of {Mo 72Fe 30}. Small angle X-ray scattering is used to study the structural features and stability of the core-shell structures in aqueous solutions. Time-resolved small angle X-ray scattering is applied to monitor the synthetic reactions and a three-stage formation mechanism is proposed to describe the synthesis of the core-shell polyoxometalates based on the monitoring results. Quasi-elastic and inelastic neutron scattering are used to probe the dynamics of water molecules in the core-shell structures and two different types ofmore » water molecules, the confined and structured water, are observed. These water molecules play an important role in bridging core and shell structures and stabilizing the cluster structures. A typical type of core shell polyoxometalates can be obtained through the Keggin-type polyoxometalate-templated growth of a layer of spherical shell structure of {Mo 72Fe 30}. Small-angle X-ray scattering is used to study the structural features and stability of the core shell structures in aqueous solutions. Time-resolved small-angle X-ray scattering is applied to monitor the synthetic reactions, and a three-stage formation mechanism is proposed to describe the synthesis of the core shell polyoxometalates based on the monitoring results. New protocols have been developed by fitting the X-ray data with custom physical models, which provide more convincing, objective, and completed data interpretation. Quasi-elastic and inelastic neutron scattering are used to probe the dynamics of water molecules in the core shell structures, and two different types of water molecules, the confined and structured water, are observed. These water molecules play an important role in bridging core and shell structures and stabilizing the cluster structures.« less

Proposed low-energy absolute calibration of nuclear recoils in a dual-phase noble element TPC using D-D neutron scattering kinematics

NASA Astrophysics Data System (ADS)

Verbus, J. R.; Rhyne, C. A.; Malling, D. C.; Genecov, M.; Ghosh, S.; Moskowitz, A. G.; Chan, S.; Chapman, J. J.; de Viveiros, L.; Faham, C. H.; Fiorucci, S.; Huang, D. Q.; Pangilinan, M.; Taylor, W. C.; Gaitskell, R. J.

2017-04-01

We propose a new technique for the calibration of nuclear recoils in large noble element dual-phase time projection chambers used to search for WIMP dark matter in the local galactic halo. This technique provides an in situ measurement of the low-energy nuclear recoil response of the target media using the measured scattering angle between multiple neutron interactions within the detector volume. The low-energy reach and reduced systematics of this calibration have particular significance for the low-mass WIMP sensitivity of several leading dark matter experiments. Multiple strategies for improving this calibration technique are discussed, including the creation of a new type of quasi-monoenergetic neutron source with a minimum possible peak energy of 272 keV. We report results from a time-of-flight-based measurement of the neutron energy spectrum produced by an Adelphi Technology, Inc. DD108 neutron generator, confirming its suitability for the proposed nuclear recoil calibration.

Detecting neutrons by forward recoil protons at the Energy & Transmutation facility: Detector development and calibration with 14.1-MeV neutrons

NASA Astrophysics Data System (ADS)

Afanasev, S.; Vishnevskiy, A.; Vishnevskiy, D.; Rogachev, A.; Tyutyunnikov, S.

2017-05-01

As part of the Energy & Transmutation project, we are developing a detector for neutrons with energies in the 10-100 MeV range emitted from the target irradiated by a charged-particle beam. The neutron is detected by measuring the time-of-flight and total kinetic energy of the forward-going recoil proton [1] knocked out at a small angle from a thin layer of plastic scintillator, which has to be selected against an intense background created by γ quanta, scattered neutrons, and charged particles. On the other hand, neutron energy has to be measured over the full range with no extra tuning of the detector operation regime. Initial measurements with a source of 14.1-MeV neutrons are reported.

The effect of amphiphilic polymers with a continuous amphiphilicity profile on the membrane properties in a bicontinuous microemulsions studied by neutron scattering

NASA Astrophysics Data System (ADS)

Klemmer, Helge F. M.; Frielinghaus, Henrich; Allgaier, Jürgen; Ohl, Michael; Holderer, Olaf

2017-06-01

Microemulsion systems consisting of oil, water and surfactant have been studied with neutron scattering techniques. The amount of surfactant needed to form a microemulsion can be dramatically reduced by the addition of small amounts of amphiphilic block copolymers (boosting effect). Here, we studied the influence of block copolymers with gradually changing amphiphilicity from hydrophilic to hydrophobic. Small angle neutron scattering (SANS), neutron spin echo spectroscopy (NSE) and phase diagram measurements in combination give access to the elastic properties of the membrane. The underlying NSE experiments for this interpretation rely on smallest changes of the relaxation curves (of ca. 1% steps) for still small changes of the bending rigidity (of ca. 10% steps). This high reliability of the experiments conducted at the SNS-NSE displays the accuracy of the instrument itself and the latest developments of the evaluation software, which were necessary to interpret such tiny changes of the bending rigidity reliably.

GUIDE FOR POLARIZED NEUTRONS

DOEpatents

Sailor, V.L.; Aichroth, R.W.

1962-12-01

The plane of polarization of a beam of polarized neutrons is changed by this invention, and the plane can be flipped back and forth quicitly in two directions in a trouble-free manner. The invention comprises a guide having a plurality of oppositely directed magnets forming a gap for the neutron beam and the gaps are spaced longitudinally in a spiral along the beam at small stepped angles. When it is desired to flip the plane of polarization the magnets are suitably rotated to change the direction of the spiral of the gaps. (AEC)

Neutron reflecting supermirror structure

DOEpatents

Wood, J.L.

1992-12-01

An improved neutron reflecting supermirror structure comprising a plurality of stacked sets of bilayers of neutron reflecting materials. The improved neutron reflecting supermirror structure is adapted to provide extremely good performance at high incidence angles, i.e. up to four time the critical angle of standard neutron mirror structures. The reflection of neutrons striking the supermirror structure at a high critical angle provides enhanced neutron throughput, and hence more efficient and economical use of neutron sources. 2 figs.

Neutron reflecting supermirror structure

DOEpatents

Wood, James L.

1992-01-01

An improved neutron reflecting supermirror structure comprising a plurality of stacked sets of bilayers of neutron reflecting materials. The improved neutron reflecting supermirror structure is adapted to provide extremely good performance at high incidence angles, i.e. up to four time the critical angle of standard neutron mirror structures. The reflection of neutrons striking the supermirror structure at a high critical angle provides enhanced neutron throughput, and hence more efficient and economical use of neutron sources.

Spin-wave dynamics in the helimagnet FeGe studied by small-angle neutron scattering

NASA Astrophysics Data System (ADS)

Siegfried, S.-A.; Sukhanov, A. S.; Altynbaev, E. V.; Honecker, D.; Heinemann, A.; Tsvyashchenko, A. V.; Grigoriev, S. V.

2017-04-01

We have studied the spin-wave stiffness of the Dzyaloshinskii-Moriya helimagnet FeGe in a temperature range from 225 K up to TC≈278.7 K by small-angle neutron scattering. The method we have used is based on [Grigoriev et al., Phys. Rev. B 92, 220415(R) (2015), 10.1103/PhysRevB.92.220415] and was extended here for the application in polycrystalline samples. We confirm the validity of the anisotropic spin-wave dispersion for FeGe caused by the Dzyaloshinskii-Moriya interaction. We have shown that the spin-wave stiffness A for the FeGe helimagnet decreases with a temperature as A (T ) =194 [1 -0.7 (T/TC) 4.2] meVÅ 2 . The finite value of the spin-wave stiffness A =58 meVÅ 2 at TC classifies the order-disorder phase transition in FeGe as being the first-order one.

Small angle neutron scattering analyses and high temperature mechanical properties of nano-structured oxide dispersion strengthened steels produced via cryomilling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Jeoung Han; Byun, Thak Sang; Shin, Eunjoo

2015-08-17

Three oxide dispersion-strengthened (ODS) steels are produced in order to investigate the effect of the mechanical alloying (MA) temperature on the microstructural evolution and high temperature mechanical properties. The microstructural evolution with different MA conditions is examined using small angle neutron scattering. As the MA temperature decreases, the density of the nanoclusters below 10 nm increases and their mean diameter decreases. A low temperature during MA leads to a high strength in the compression tests performed at 500 *C; however, this effect disappears in testing at 900 *C. The milling process at *70 *C exhibits excellent high fracture toughness, whichmore » is better than the benchmark material 14YWT-SM10. However, the *150 *C milling process results in significantly worse fracture toughness properties. The reasons for this strong temperature dependency are discussed.« less

Feasibility and applications of the spin-echo modulation option for a small angle neutron scattering instrument at the European Spallation Source

NASA Astrophysics Data System (ADS)

Kusmin, A.; Bouwman, W. G.; van Well, A. A.; Pappas, C.

2017-06-01

We describe theoretical and practical aspects of spin-echo modulated small-angle neutron scattering (SEMSANS) as well as the potential combination with SANS. Based on the preliminary technical designs of SKADI (a SANS instrument proposed for the European Spallation Source) and a SEMSANS add-on, we assess the practicability, feasibility and scientific merit of a combined SANS and SEMSANS setup by calculating tentative SANS and SEMSANS results for soft matter, geology and advanced material samples that have been previously studied by scattering methods. We conclude that lengths from 1 nm up to 0.01 mm can be observed simultaneously in a single measurement. Thus, the combination of SANS and SEMSANS instrument is suited for the simultaneous observation of a wide range of length scales, e.g. for time-resolved studies of kinetic processes in complex multiscale systems.

The study of the structural properties of very low viscosity sodium alginate by small-angle neutron scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Badita, C. R., E-mail: ramona@tandem.nipne.ro; University of Bucharest, Faculty of Physics, Atomiştilor 405, CP MG - 11, RO – 077125, Bucharest-Magurele; Aranghel, D., E-mail: daranghe@nipne.ro

2016-03-25

Sodium alginate is a linear polymer extract from brown algae and it is used in the biomedical, food, cosmetics and pharmaceutical industries as solution property modifiers and gelling agents. But despite the extensive studies of the alginate gelation process, still some fundamental questions remain unresolved. The fractal behavior of very low viscosity sodium alginate solutions and their influence on the critical gelation of alginate induced by Ca{sup 2+} ions were investigated using Small-Angle Neutron Scattering (SANS) measurements. SANS data are interpreted using both standard linear plots and the Beaucage model. The scattering intensity is dependent by alginate concentration and Ca{supmore » 2+} concentration. From a critical concentration of 1.0 % w/w our polymer swelled forming spherical structures with rough surfaces. Also the addition of the salt induces the collapse and the appearance of the aggregation and clusters formation.« less

The study of the structural properties of very low viscosity sodium alginate by small-angle neutron scattering

NASA Astrophysics Data System (ADS)

Badita, C. R.; Aranghel, D.; Radulescu, A.; Anitas, E. M.

2016-03-01

Sodium alginate is a linear polymer extract from brown algae and it is used in the biomedical, food, cosmetics and pharmaceutical industries as solution property modifiers and gelling agents. But despite the extensive studies of the alginate gelation process, still some fundamental questions remain unresolved. The fractal behavior of very low viscosity sodium alginate solutions and their influence on the critical gelation of alginate induced by Ca2+ ions were investigated using Small-Angle Neutron Scattering (SANS) measurements. SANS data are interpreted using both standard linear plots and the Beaucage model. The scattering intensity is dependent by alginate concentration and Ca2+ concentration. From a critical concentration of 1.0 % w/w our polymer swelled forming spherical structures with rough surfaces. Also the addition of the salt induces the collapse and the appearance of the aggregation and clusters formation.

Development of a lithium fluoride zinc sulfide based neutron multiplicity counter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cowles, Christian; Behling, Spencer; Baldez, Phoenix

Here, the feasibility of a full-scale lithium fluoride zinc sulfide (LiF/ZnS) based neutron multiplicity counter has been demonstrated. The counter was constructed of modular neutron detecting stacks that each contain five sheets of LiF/ZnS interleaved between six sheets of wavelength shifting plastic with a photomultiplier tube on each end. Twelve such detector stacks were placed around a sample chamber in a square arrangement with lithiated high-density polyethylene blocks in the corners to reflect high-energy neutrons and capture low-energy neutrons. The final system design was optimized via modeling and small-scale test. Measuring neutrons from a 252Cf source, the counter achieved amore » 36% neutron detection efficiency (ϵϵ) and an View the MathML source11.7μs neutron die-away time (ττ) for a doubles figure-of-merit (ϵ 2/τ) of 109. This is the highest doubles figure-of-merit measured to-date for a 3He-free neutron multiplicity counter.« less

Development of a lithium fluoride zinc sulfide based neutron multiplicity counter

NASA Astrophysics Data System (ADS)

Cowles, Christian; Behling, Spencer; Baldez, Phoenix; Folsom, Micah; Kouzes, Richard; Kukharev, Vladislav; Lintereur, Azaree; Robinson, Sean; Siciliano, Edward; Stave, Sean; Valdez, Patrick

2018-04-01

The feasibility of a full-scale lithium fluoride zinc sulfide (LiF/ZnS) based neutron multiplicity counter has been demonstrated. The counter was constructed of modular neutron detecting stacks that each contain five sheets of LiF/ZnS interleaved between six sheets of wavelength shifting plastic with a photomultiplier tube on each end. Twelve such detector stacks were placed around a sample chamber in a square arrangement with lithiated high-density polyethylene blocks in the corners to reflect high-energy neutrons and capture low-energy neutrons. The final system design was optimized via modeling and small-scale test. Measuring neutrons from a 252Cf source, the counter achieved a 36% neutron detection efficiency (ɛ) and an 11 . 7 μs neutron die-away time (τ) for a doubles figure-of-merit (ɛ2 / τ) of 109. This is the highest doubles figure-of-merit measured to-date for a 3He-free neutron multiplicity counter.

Development of a lithium fluoride zinc sulfide based neutron multiplicity counter

DOE PAGES

Cowles, Christian; Behling, Spencer; Baldez, Phoenix; ...

2018-01-12

Here, the feasibility of a full-scale lithium fluoride zinc sulfide (LiF/ZnS) based neutron multiplicity counter has been demonstrated. The counter was constructed of modular neutron detecting stacks that each contain five sheets of LiF/ZnS interleaved between six sheets of wavelength shifting plastic with a photomultiplier tube on each end. Twelve such detector stacks were placed around a sample chamber in a square arrangement with lithiated high-density polyethylene blocks in the corners to reflect high-energy neutrons and capture low-energy neutrons. The final system design was optimized via modeling and small-scale test. Measuring neutrons from a 252Cf source, the counter achieved amore » 36% neutron detection efficiency (ϵϵ) and an View the MathML source11.7μs neutron die-away time (ττ) for a doubles figure-of-merit (ϵ 2/τ) of 109. This is the highest doubles figure-of-merit measured to-date for a 3He-free neutron multiplicity counter.« less

Virtual Excitation and Multiple Scattering Correction Terms to the Neutron Index of Refraction for Hydrogen.

PubMed

Schoen, K; Snow, W M; Kaiser, H; Werner, S A

2005-01-01

The neutron index of refraction is generally derived theoretically in the Fermi approximation. However, the Fermi approximation neglects the effects of the binding of the nuclei of a material as well as multiple scattering. Calculations by Nowak introduced correction terms to the neutron index of refraction that are quadratic in the scattering length and of order 10(-3) fm for hydrogen and deuterium. These correction terms produce a small shift in the final value for the coherent scattering length of H2 in a recent neutron interferometry experiment.

Tea Derived Galloylated Polyphenols Cross-Link Purified Gastrointestinal Mucins

PubMed Central

Georgiades, Pantelis; Pudney, Paul D. A.; Rogers, Sarah; Thornton, David J.; Waigh, Thomas A.

2014-01-01

Polyphenols derived from tea are thought to be important for human health. We show using a combination of particle tracking microrheology and small-angle neutron scattering that polyphenols acts as cross-linkers for purified gastrointestinal mucin, derived from the stomach and the duodenum. Both naturally derived purified polyphenols, and green and black tea extracts are shown to act as cross-linkers. The main active cross-linking component is found to be the galloylated forms of catechins. The viscosity, elasticity and relaxation time of the mucin solutions experience an order of magnitude change in value upon addition of the polyphenol cross-linkers. Similarly small-angle neutron scattering experiments demonstrate a sol-gel transition with the addition of polyphenols, with a large increase in the scattering at low angles, which is attributed to the formation of large scale (>10 nm) heterogeneities during gelation. Cross-linking of mucins by polyphenols is thus expected to have an impact on the physicochemical environment of both the stomach and duodenum; polyphenols are expected to modulate the barrier properties of mucus, nutrient absorption through mucus and the viscoelastic microenvironments of intestinal bacteria. PMID:25162539

Digenetic Changes in Macro- to Nano-Scale Porosity in the St. Peter Sandstone:L An (Ultra) Small Angle Neutron Scattering and Backscattered Electron Imagining Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anovitz, Lawrence; Cole, David; Rother, Gernot

2013-01-01

Small- and Ultra-Small Angle Neutron Scattering (SANS and USANS) provide powerful tools for quantitative analysis of porous rocks, yielding bulk statistical information over a wide range of length scales. This study utilized (U)SANS to characterize shallowly buried quartz arenites from the St. Peter Sandstone. Backscattered electron imaging was also used to extend the data to larger scales. These samples contain significant volumes of large-scale porosity, modified by quartz overgrowths, and neutron scattering results show significant sub-micron porosity. While previous scattering data from sandstones suggest scattering is dominated by surface fractal behavior over many orders of magnitude, careful analysis of ourmore » data shows both fractal and pseudo-fractal behavior. The scattering curves are composed of subtle steps, modeled as polydispersed assemblages of pores with log-normal distributions. However, in some samples an additional surface-fractal overprint is present, while in others there is no such structure, and scattering can be explained by summation of non-fractal structures. Combined with our work on other rock-types, these data suggest that microporosity is more prevalent, and may play a much more important role than previously thought in fluid/rock interactions.« less

Small-angle neutron scattering study of micropore collapse in amorphous solid water.

PubMed

Mitterdorfer, Christian; Bauer, Marion; Youngs, Tristan G A; Bowron, Daniel T; Hill, Catherine R; Fraser, Helen J; Finney, John L; Loerting, Thomas

2014-08-14

Vapor-deposited amorphous solid water (ASW) is the most abundant solid molecular material in space, where it plays a direct role in both the formation of more complex chemical species and the aggregation of icy materials in the earliest stages of planet formation. Nevertheless, some of its low temperature physics such as the collapse of the micropore network upon heating are still far from being understood. Here we characterize the nature of the micropores and their collapse using neutron scattering of gram-quantities of D2O-ASW of internal surface areas up to 230 ± 10 m(2) g(-1) prepared at 77 K. The model-free interpretation of the small-angle scattering data suggests micropores, which remain stable up to 120-140 K and then experience a sudden collapse. The exact onset temperature to pore collapse depends on the type of flow conditions employed in the preparation of ASW and, thus, the specific surface area of the initial deposit, whereas the onset of crystallization to cubic ice is unaffected by the flow conditions. Analysis of the small-angle neutron scattering signal using the Guinier-Porod model suggests that a sudden transition from three-dimensional cylindrical pores with 15 Å radius of gyration to two-dimensional lamellae is the mechanism underlying the pore collapse. The rather high temperature of about 120-140 K of micropore collapse and the 3D-to-2D type of the transition unraveled in this study have implications for our understanding of the processing and evolution of ices in various astrophysical environments.

Small-angle neutron scattering reveals the assembly mode and oligomeric architecture of TET, a large, dodecameric aminopeptidase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Appolaire, Alexandre; Girard, Eric; Colombo, Matteo

2014-11-01

The present work illustrates that small-angle neutron scattering, deuteration and contrast variation, combined with in vitro particle reconstruction, constitutes a very efficient approach to determine subunit architectures in large, symmetric protein complexes. In the case of the 468 kDa heterododecameric TET peptidase machine, it was demonstrated that the assembly of the 12 subunits is a highly controlled process and represents a way to optimize the catalytic efficiency of the enzyme. The specific self-association of proteins into oligomeric complexes is a common phenomenon in biological systems to optimize and regulate their function. However, de novo structure determination of these important complexesmore » is often very challenging for atomic-resolution techniques. Furthermore, in the case of homo-oligomeric complexes, or complexes with very similar building blocks, the respective positions of subunits and their assembly pathways are difficult to determine using many structural biology techniques. Here, an elegant and powerful approach based on small-angle neutron scattering is applied, in combination with deuterium labelling and contrast variation, to elucidate the oligomeric organization of the quaternary structure and the assembly pathways of 468 kDa, hetero-oligomeric and symmetric Pyrococcus horikoshii TET2–TET3 aminopeptidase complexes. The results reveal that the topology of the PhTET2 and PhTET3 dimeric building blocks within the complexes is not casual but rather suggests that their quaternary arrangement optimizes the catalytic efficiency towards peptide substrates. This approach bears important potential for the determination of quaternary structures and assembly pathways of large oligomeric and symmetric complexes in biological systems.« less

Neutron Scattering Measurements of Carbon Dioxide Adsorption in Pores within the Marcellus Shale: Implications for Sequestration.

PubMed

Stefanopoulos, Konstantinos L; Youngs, Tristan G A; Sakurovs, Richard; Ruppert, Leslie F; Bahadur, Jitendra; Melnichenko, Yuri B

2017-06-06

Shale is an increasingly viable source of natural gas and a potential candidate for geologic CO 2 sequestration. Understanding the gas adsorption behavior on shale is necessary for the design of optimal gas recovery and sequestration projects. In the present study neutron diffraction and small-angle neutron scattering measurements of adsorbed CO 2 in Marcellus Shale samples were conducted on the Near and InterMediate Range Order Diffractometer (NIMROD) at the ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory along an adsorption isotherm of 22 °C and pressures of 25 and 40 bar. Additional measurements were conducted at approximately 22 and 60 °C at the same pressures on the General-Purpose Small-Angle Neutron Scattering (GP-SANS) instrument at Oak Ridge National Laboratory. The structures investigated (pores) for CO 2 adsorption range in size from Å level to ∼50 nm. The results indicate that, using the conditions investigated densification or condensation effects occurred in all accessible pores. The data suggest that at 22 °C the CO 2 has liquid-like properties when confined in pores of around 1 nm radius at pressures as low as 25 bar. Many of the 2.5 nm pores, 70% of 2 nm pores, most of the <1 nm pores, and all pores <0.25 nm, are inaccessible or closed to CO 2 , suggesting that despite the vast numbers of micropores in shale, the micropores will be unavailable for storage for geologic CO 2 sequestration.

Structural analysis of Fe–Mn–O nanoparticles in glass ceramics by small angle scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raghuwanshi, Vikram Singh, E-mail: vikram.raghuwanshi@helmholtz-berlin.de; Harizanova, Ruzha; Tatchev, Dragomir

2015-02-15

Magnetic nanocrystals containing Fe and Mn were obtained by annealing of silicate glasses with the composition 13.6Na{sub 2}O–62.9SiO{sub 2}–8.5MnO–15.0Fe{sub 2}O{sub 3−x} (mol%) at 580 °C for different periods of time. Here, we present Small Angle Neutron Scattering using Polarized neutrons (SANSPOL) and Anomalous Small Angle X-ray Scattering (ASAXS) investigation on these glass ceramic samples. Analysis of scattering data from both methods reveals the formation of spherical core–shell type of nanoparticles with mean sizes between 10 nm and 100 nm. ASAXS investigation shows the particles have higher concentration of iron atoms and the shell like region surrounding the particles is enrichedmore » in SiO{sub 2}. SANSPOL investigation shows the particles are found to be magnetic and are surrounded by a non-magnetic shell-like region. - Graphical abstract: Magnetic spherical core–shell nanoparticles in glass ceramics: SANSPOL and ASAXS investigations. - Highlights: • Formation and growth mechanisms of magnetic nanoparticles in silicate glass. • SANSPOL and ASAXS methods employed to evaluate quantitative information. • Analyses showed formation of nanoparticles with spherical core–shell structures. • Core of the particle is magnetic and surrounded by weak magnetic shell like region.« less

Structural characterization of the phospholipid stabilizer layer at the solid-liquid interface of dispersed triglyceride nanocrystals with small-angle x-ray and neutron scattering

NASA Astrophysics Data System (ADS)

Schmiele, Martin; Schindler, Torben; Unruh, Tobias; Busch, Sebastian; Morhenn, Humphrey; Westermann, Martin; Steiniger, Frank; Radulescu, Aurel; Lindner, Peter; Schweins, Ralf; Boesecke, Peter

2013-06-01

Dispersions of crystalline nanoparticles with at least one sufficiently large unit cell dimension can give rise to Bragg reflections in the small-angle scattering range. If the nanocrystals possess only a small number of unit cells along these particular crystallographic directions, the corresponding Bragg reflections will be broadened. In a previous study of phospholipid stabilized dispersions of β-tripalmitin platelets [Unruh, J. Appl. Crystallogr.JACGAR0021-889810.1107/S0021889807044378 40, 1008 (2007)], the x-ray powder pattern simulation analysis (XPPSA) was developed. The XPPSA method facilitates the interpretation of the rather complicated small-angle x-ray scattering (SAXS) curves of such dispersions of nanocrystals. The XPPSA method yields the distribution function of the platelet thicknesses and facilitates a structural characterization of the phospholipid stabilizer layer at the solid-liquid interface between the nanocrystals and the dispersion medium from the shape of the broadened 001 Bragg reflection. In this contribution an improved and extended version of the XPPSA method is presented. The SAXS and small-angle neutron scattering patterns of dilute phospholipid stabilized tripalmitin dispersions can be reproduced on the basis of a consistent simulation model for the particles and their phospholipid stabilizer layer on an absolute scale. The results indicate a surprisingly flat arrangement of the phospholipid molecules in the stabilizer layer with a total thickness of only 12 Å. The stabilizer layer can be modeled by an inner shell for the fatty acid chains and an outer shell including the head groups and additional water. The experiments support a dense packing of the phospholipid molecules on the nanocrystal surfaces rather than isolated phospholipid domains.

Anisotropy of the neutron fluence from a plasma focus.

NASA Technical Reports Server (NTRS)

Lee, J. H.; Shomo, L. P.; Kim, K. H.

1972-01-01

The fluence of neutrons from a plasma focus was measured by gamma spectrometry of an activated silver target. This method results in a significant increase in accuracy over the beta-counting method. Multiple detectors were used in order to measure the anisotropy of the fluence of neutrons. The fluence was found to be concentrated in a cone with a half-angle of 30 deg about the axis, and to drop off rapidly outside of this cone; the anisotropy was found to depend upon the total yield of neutrons. This dependence was strongest on the axis. Neither the axial concentration of the fluence of neutrons nor its dependence on the total yield of neutrons is explained by any of the currently proposed models. Some other explanations, including the possibility of an axially distributed source, are considered.

The ultrastructure and flexibility of thylakoid membranes in leaves and isolated chloroplasts as revealed by small-angle neutron scattering.

PubMed

Unnep, R; Zsiros, O; Solymosi, K; Kovács, L; Lambrev, P H; Tóth, T; Schweins, R; Posselt, D; Székely, N K; Rosta, L; Nagy, G; Garab, G

2014-09-01

We studied the periodicity of the multilamellar membrane system of granal chloroplasts in different isolated plant thylakoid membranes, using different suspension media, as well as on different detached leaves and isolated protoplasts-using small-angle neutron scattering. Freshly isolated thylakoid membranes suspended in isotonic or hypertonic media, containing sorbitol supplemented with cations, displayed Bragg peaks typically between 0.019 and 0.023Å(-1), corresponding to spatially and statistically averaged repeat distance values of about 275-330 Å⁻¹. Similar data obtained earlier led us in previous work to propose an origin from the periodicity of stroma thylakoid membranes. However, detached leaves, of eleven different species, infiltrated with or soaked in D2O in dim laboratory light or transpired with D2O prior to measurements, exhibited considerably smaller repeat distances, typically between 210 and 230 Å⁻¹, ruling out a stromal membrane origin. Similar values were obtained on isolated tobacco and spinach protoplasts. When NaCl was used as osmoticum, the Bragg peaks of isolated thylakoid membranes almost coincided with those in the same batch of leaves and the repeat distances were very close to the electron microscopically determined values in the grana. Although neutron scattering and electron microscopy yield somewhat different values, which is not fully understood, we can conclude that small-angle neutron scattering is a suitable technique to study the periodic organization of granal thylakoid membranes in intact leaves under physiological conditions and with a time resolution of minutes or shorter. We also show here, for the first time on leaves, that the periodicity of thylakoid membranes in situ responds dynamically to moderately strong illumination. This article is part of a special issue entitled: photosynthesis research for sustainability: keys to produce clean energy. Copyright © 2014 Elsevier B.V. All rights reserved.

Incorporation and Effects of Nanoparticles in a Supramolecular Polymer

DTIC Science & Technology

2016-05-01

Oak Ridge, TN Robert H Lambeth and Frederick L Beyer Weapons and Materials Research Directorate, ARL Approved for...nanocomposites: phase diagram, rheology and structure using a combined small angle neutron scattering and reverse Monte Carlo approach. Soft Matter. 2010;6

Investigation of Monodisperse Dendrimeric Polysaccharide Nanoparticle Dispersions Using Small Angle Neutron Scattering

NASA Astrophysics Data System (ADS)

Atkinson, John; Nickels, Jonathan; Papp-Szabo, Erzsi; Katsaras, John; Dutcher, John

2015-03-01

Phytoglycogen is a highly branched polysaccharide that is very similar to the energy storage molecule glycogen. We have isolated monodisperse phytoglycogen nanoparticles from corn and these particles are attractive for applications in the cosmetic, food and beverage, and biomedical industries. Many of these promising applications are due to the special interaction between the nanoparticles and water, which results in: (1) high solubility; (2) low viscosity and high stability in aqueous dispersions; and (3) a remarkable capacity to sequester and retain water. Our rheology measurements indicate that the nanoparticles behave like hard spheres in water, with the viscosity diverging for concentrations >25% (w/w). Because of this, aqueous suspensions of phytoglycogen provide an ideal platform for detailed testing of theories of colloidal glasses and jamming. To further explore the interaction of the phytoglycogen particles and water, we have performed small angle neutron scattering (SANS) measurements on the Extended Q-Range SANS (EQ-SANS) diffractometer at the Spallation Neutron Source at Oak Ridge National Laboratory. Measurements performed on phytoglycogen dispersions in mixtures of hydrogenated and deuterated water have allowed us to determine the particle size and average particle spacing as a function of the phytoglycogen concentration in the limits of dilute and concentrated dispersions.

Neutron diffraction study of aqueous Laponite suspensions at the NIMROD diffractometer.

PubMed

Tudisca, V; Bruni, F; Scoppola, E; Angelini, R; Ruzicka, B; Zulian, L; Soper, A K; Ricci, M A

2014-09-01

The process of dynamical arrest, leading to formation of different arrested states such as glasses and gels, along with the closely related process of aging, is central for both basic research and technology. Here we report on a study of the time-dependent structural evolution of two aqueous Laponite clay suspensions at different weight concentrations. Neutron diffraction experiments have been performed with the near and intermediate range order diffractometer (NIMROD) that allows studies of the structure of liquids and disordered materials over a continuous length scale ranging from 1 to 300 Å, i.e., from the atomistic to the mesoscopic scales. NIMROD is presently a unique diffractometer, bridging the length scales traditionally investigated by small angle neutron scattering or small angle x-ray scattering with that accessible by traditional diffractometers for liquids. Interestingly, we have unveiled a signature of aging of both suspensions in the length scale region of NIMROD. This phenomenon, ascribed to sporadic contacts between Laponite platelets at long times, has been observed with the sample arrested as gel or as repulsive glass. Moreover, water molecules within the layers closest to Laponite platelets surface show orientational and translational order, which maps into the crystalline structure of Laponite.

Determination of neutron multiplication coefficients for fuel elements irradiated by spallation neutrons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhatia, Chitra; Kumar, V.

2010-02-15

A neutron multiplication coefficient, k{sub eff}, has been estimated for spallation neutron flux using the data of spectrum average cross sections of all absorption, fission, and nonelastic reaction channels of {sup 232}Th, {sup 238}U, {sup 235}U, and {sup 233}U fuel elements. It has been revealed that in spallation neutron flux (i) nonfission, nonabsorption reactions play an important role in the calculation of k{sub eff}, (ii) one can obtain a high value of k{sub eff} even for fertile {sup 232}Th fuel, which is hardly possible in a conventional fast reactor, and (iii) spectrum average absorption cross sections of neutron poisons ofmore » a conventional reactor are relatively very small.« less

Curved Waveguide Based Nuclear Fission for Small, Lightweight Reactors

NASA Technical Reports Server (NTRS)

Coker, Robert; Putnam, Gabriel

2012-01-01

The focus of the presented work is on the creation of a system of grazing incidence, supermirror waveguides for the capture and reuse of fission sourced neutrons. Within research reactors, neutron guides are a well known tool for directing neutrons from the confined and hazardous central core to a more accessible testing or measurement location. Typical neutron guides have rectangular, hollow cross sections, which are crafted as thin, mirrored waveguides plated with metal (commonly nickel). Under glancing angles with incoming neutrons, these waveguides can achieve nearly lossless transport of neutrons to distant instruments. Furthermore, recent developments have created supermirror surfaces which can accommodate neutron grazing angles up to four times as steep as nickel. A completed system will form an enclosing ring or spherical resonator system to a coupled neutron source for the purpose of capturing and reusing free neutrons to sustain and/or accelerate fission. While grazing incidence mirrors are a known method of directing and safely using neutrons, no method has been disclosed for capture and reuse of neutrons or sustainment of fission using a circular waveguide structure. The presented work is in the process of fabricating a functional, highly curved, neutron supermirror using known methods of Ni-Ti layering capable of achieving incident reflection angles up to four times steeper than nickel alone. Parallel work is analytically investigating future geometries, mirror compositions, and sources for enabling sustained fission with applicability to the propulsion and energy goals of NASA and other agencies. Should research into this concept prove feasible, it would lead to development of a high energy density, low mass power source potentially capable of sustaining fission with a fraction of the standard critical mass for a given material and a broadening of feasible materials due to reduced rates of release, absorption, and non-fission for neutrons. This advance could be applied to direct propulsion through guided fission products or as a secondary energy source for high impulse electric propulsion. It would help meet national needs for highly efficient energy sources with limited dependence on fossil fuels or conflict materials, and it would improve the use of low grade fissile materials which would help reduce national stockpiles and waste.

Solid state neutron detector array

DOEpatents

Seidel, John G.; Ruddy, Frank H.; Brandt, Charles D.; Dulloo, Abdul R.; Lott, Randy G.; Sirianni, Ernest; Wilson, Randall O.

1999-01-01

A neutron detector array is capable of measuring a wide range of neutron fluxes. The array includes multiple semiconductor neutron detectors. Each detector has a semiconductor active region that is resistant to radiation damage. In one embodiment, the array preferably has a relatively small size, making it possible to place the array in confined locations. The ability of the array to detect a wide range of neutron fluxes is highly advantageous for many applications such as detecting neutron flux during start up, ramp up and full power of nuclear reactors.

Smectic C chevrons in nanocylinders

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lefort, R., E-mail: ronan.lefort@univ-rennes1.fr; Morineau, D.; Jean, F.

2014-11-17

The structure of an achiral smectic-C liquid crystal confined in nanocylinders with a planar surface anchoring is studied by small angle neutron scattering. We observe an invariant alignment of the nematic director with the pore axis, that promotes an original chevron structure with revolution symmetry.

Recent results from the NN-interaction studies with polarized beams and targets at ANKE-COSY

NASA Astrophysics Data System (ADS)

Dymov, Sergey

2016-02-01

Adding to the nucleon-nucleon scattering database is one of the major priorities of the ANKE collaboration. Such data are necessary ingredients, not only for the understanding of nuclear forces, but also for the description of meson production and other nuclear reactions at intermediate energies. By measuring the cross section, deuteron analysing powers, and spin-correlation parameters in the dp → {pp}sn reaction, where {pp}s represents the 1S0 state, information has been obtained on small-angle neutron-proton spin-flip charge-exchange amplitudes. The measurements of pp elastic scattering by the COSY-EDDA have had a major impact on the partial wave analysis of this reaction above 1 GeV. However, these experiments only extended over the central region of c.m. angles, 300 < θcm < 1500, that has left major ambiguities in the phase shift analysis by the SAID group. In contrast, the small angle region is accessible at ANKE-COSY, that allowed measurement of the differential cross section and the analysing power at 50 < θcm < 300 in the 0.8 — 2.8 GeV energy range. The data on the pn elastic scattering are much more scarce than those of pp, especially in the region above 1.15 GeV. The study of the dp → {pp}s n reaction provides the information about the pn elastic scattering at large angles. The small angle scattering was studied with the polarized proton COSY beam and an unpolarised deuterium gas target. The detection the spectator proton in the ANKE vertex silicon detector allowed to use the deuterium target as an effective neutron one. The analysing powers of the process were obtained at six beam energies from 0.8 to 2.4 GeV.

Influence of ceramide on the internal structure and hydration of the phospholipid bilayer studied by neutron and X-ray scattering

NASA Astrophysics Data System (ADS)

Kiselev, M. A.; Zemlyanaya, E. V.; Ryabova, N. Y.; Hauss, T.; Almasy, L.; Funari, S. S.; Zbytovska, J.; Lombardo, D.

2014-07-01

Small angle neutron scattering (SANS), neutron diffraction and X-ray powder diffraction were used to investigate influence of N-stearoyl phytosphingosine (CER[NP]) and α-hydroxy- N-stearoyl phytosphingosine (CER[AP]) on the internal structure and hydration of DMPC membrane in fully and partly hydrated states at T = 30 °C. Application of Fourier analysis for diffraction data and model calculations for the SANS data evidence that addition of both CER[NP] and CER[AP] in small concentrations promotes significant changes in the organization of DMPC bilayers, such as the increase of the hydrophobic core region. SANS data evidence a decrease in the average radius and polydispersity of the vesicles that can be ascribed to hydrogen bonds interactions that favor tight lipid packing with a compact, more rigid character.

Structure of biodiesel based bicontinuous microemulsions for environmentally compatible decontamination: A small angle neutron scattering and freeze fracture electron microscopy study.

PubMed

Wellert, S; Karg, M; Imhof, H; Steppin, A; Altmann, H-J; Dolle, M; Richardt, A; Tiersch, B; Koetz, J; Lapp, A; Hellweg, T

2008-09-01

Most toxic industrial chemicals and chemical warfare agents are hydrophobic and can only be solubilized in organic solvents. However, most reagents employed for the degradation of these toxic compounds can only be dissolved in water. Hence, microemulsions are auspicious media for the decontamination of a variety of chemical warfare agents and pesticides. They allow for the solubilization of both the lipophilic toxics and the hydrophilic reagent. Alkyl oligoglucosides and plant derived solvents like rapeseed methyl ester enable the formulation of environmentally compatible bicontinuous microemulsions. In the present article the phase behavior of such a microemulsion is studied and the bicontinuous phase is identified. Small angle neutron scattering (SANS) and freeze fracture electron microscopy (FFEM) measurements are used to characterize the structure of the bicontinuous phase and allow for an estimation of the total internal interface. Moreover, also the influence of the co-surfactant (1-pentanol) on the structural parameters of the bicontinuous phase is studied with SANS.

Probing the anisotropic vortex lattice in the Fe-based superconductor KFe2As2 using small angle neutron scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Debeer-Schmitt, Lisa M; Dewhurst, Charles; Kikuchi, Hiroko

Using small angle neutron scattering, the anisotropy of the magnetic vortex lattice (VL), in the heavily hole-doped pnictide superconductor, KFe2As2, was studied. Well-ordered VL scattering patterns were measured with elds applied in directions between B k c and the basal plane, rotating either towards [100] or [110]. Slightly distorted hexagonal patterns were observed when B k c. However, the scattering pattern distorted strongly as the eld was rotated away from the c- axis. At low eld, the arrangement of vortices is strongly aected by the anisotropy of penetration depth in the plane perpendicular to the eld. By tting the distortionmore » with the anisotropic London model, we obtained an estimate of 3:4 for the anisotropy factor, , between the in-plane and c-axis penetration depths at the lowest temperature studied. The results further reveal VL phase transitions as a function of eld direction. We discuss these transitions using the "Hairy Ball" theorem.« less

Characterization of nanoparticles of lidocaine in w/o microemulsions using small-angle neutron scattering and dynamic light scattering

NASA Astrophysics Data System (ADS)

Shukla, A.; Kiselev, M. A.; Hoell, A.; Neubert, R. H. H.

2004-08-01

Microemulsions (MEs) are of special interest because a variety of Reactants can be introduced into the nanometer-sized aqueous domains, leading to materials with controlled size and shape [1,2]. In the past few years, significant research has been conducted in the reverse ME-mediated synthesis of organic nanoparticles [3,4]. In this study, a w/o ME medium was employed for the synthesis of lidocaine by direct precipitation in w/o microemulsion systems: water/isopropylpalmitat/Tween80/Span80. The particle size as well as the location of nanoparticles in the ME droplet were characterized by means of dynamic light scattering (DLS) and small angle neutron scattering (SANS). It is observed that lidocaine precipitated in the aqueous cores because of its insolubility in water. Hydrodynamic radius and gyration radius of microemulsion droplets were estimated as ~15 nm and ~4.50 nm from DLS and SANS respectively. Furthermore, different size parameters obtained by DLS and SANS experiments were compared

Characterization of white poplar and eucalyptus after ionic liquid pretreatment as a function of biomass loading using X-ray diffraction and small angle neutron scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yuan, Xueming; Duan, Yonghao; He, Lilin

A systematic study was done to understand interactions among biomass loading during ionic liquid (IL) pretreatment, biomass type and biomass structures. White poplar and eucalyptus samples were pretreated using 1-ethyl-3-methylimidazolium acetate (EmimOAc) at 110 °C for 3 h at biomass loadings of 5, 10, 15, 20 and 25 wt%. All of the samples were chemically characterized and tested for enzymatic hydrolysis. Physical structures including biomass crystallinity and porosity were measured by X-ray diffraction (XRD) and small angle neutron scattering (SANS), respectively. SANS detected pores of radii ranging from ~25 to 625 Å, enabling assessment of contributions of pores with different sizes to increased porositymore » after pretreatment. Contrasting dependences of sugar conversion on white poplar and eucalyptus as a function of biomass loading were observed and cellulose crystalline structure was found to play an important role.« less

Characterization of white poplar and eucalyptus after ionic liquid pretreatment as a function of biomass loading using X-ray diffraction and small angle neutron scattering.

PubMed

Yuan, Xueming; Duan, Yonghao; He, Lilin; Singh, Seema; Simmons, Blake; Cheng, Gang

2017-05-01

A systematic study was performed to understand interactions among biomass loading during ionic liquid (IL) pretreatment, biomass type and biomass structures. White poplar and eucalyptus samples were pretreated using 1-ethyl-3-methylimidazolium acetate (EmimOAc) at 110°C for 3h at biomass loadings of 5, 10, 15, 20 and 25wt%. All of the samples were chemically characterized and tested for enzymatic hydrolysis. Physical structures including biomass crystallinity and porosity were measured by X-ray diffraction (XRD) and small angle neutron scattering (SANS), respectively. SANS detected pores of radii ranging from ∼25 to 625Å, enabling assessment of contributions of pores with different sizes to increased porosity after pretreatment. Contrasting dependences of sugar conversion on white poplar and eucalyptus as a function of biomass loading were observed and cellulose crystalline structure was found to play an important role. Copyright © 2017 Elsevier Ltd. All rights reserved.

Neutron reflecting supermirror structure

DOEpatents

Wood, James L.

1992-01-01

An improved neutron reflecting supermirror structure comprising a plurality of stacked sets of bilayers of neutron reflecting materials. The improved neutron reflecting supermirror structure is adapted to provide extremely good performance at high incidence angles, i.e. up to four time the critical angle of standard neutron mirror structures. The reflection of neutrons striking the supermirror structure at a high critical angle provides enhanced neutron throughput, and hence more efficient and economical use of neutron sources. One layer of each set of bilayers consist of titanium, and the second layer of each set of bilayers consist of an alloy of nickel with carbon interstitially present in the nickel alloy.

Nonuniformity in natural rubber as revealed by small-angle neutron scattering, small-angle X-ray scattering, and atomic force microscopy.

PubMed

Karino, Takeshi; Ikeda, Yuko; Yasuda, Yoritaka; Kohjiya, Shinzo; Shibayama, Mitsuhiro

2007-02-01

The microscopic structures of natural rubber (NR) and deproteinized NR (DPNR) were investigated by means of small-angle neutron scattering (SANS), small-angle X-ray scattering (SAXS), and atomic force microscopy (AFM). They were compared to those of isoprene rubber (IR), which is a synthetic analogue of NR in terms of chemical structure without any non-rubber components like proteins. Comparisons of the structure and mechanical properties of NR, DPNR, and IR lead to the following conclusions. (i) The well-known facts, for example, the outstanding green strength of NR and strain-induced crystallization, are due not much to the presence of proteins but to other components such as the presence of phospholipids and/or the higher stereoregularity of NR. It also became clear the naturally residing proteins accelerate the upturn of stress at low strain. The protein phases work as cross-linking sites and reinforcing fillers in the rubbery matrix. (ii) The microscopic structures of NR were successfully reproduced by SANS intensity functions consisting of squared-Lorentz and Lorentz functions, indicating the presence of inhomogeneities in bulk and thermal concentration fluctuations in swollen state, respectively. On the other hand, IR rubbers were homogeneous in bulk. (iii) The inhomogeneities in NR are assigned to protein aggregates of the order of 200 A or larger. Although these aggregates are larger in size as well as in volume fraction than those of cross-link inhomogeneities introduced by cross-linking, they are removed by deproteinization. (iv) Swelling of both NR and IR networks introduces gel-like concentration fluctuations whose mesh size is of the order of 20 A.

Biological Small Angle Scattering: Techniques, Strategies and Tips

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chaudhuri, Barnali; Muñoz, Inés G.; Urban, Volker S.

This book provides a clear, comprehensible and up-to-date description of how Small Angle Scattering (SAS) can help structural biology researchers. SAS is an efficient technique that offers structural information on how biological macromolecules behave in solution. SAS provides distinct and complementary data for integrative structural biology approaches in combination with other widely used probes, such as X-ray crystallography, Nuclear magnetic resonance, Mass spectrometry and Cryo-electron Microscopy. The development of brilliant synchrotron small-angle X-ray scattering (SAXS) beam lines has increased the number of researchers interested in solution scattering. SAS is especially useful for studying conformational changes in proteins, highly flexible proteins,more » and intrinsically disordered proteins. Small-angle neutron scattering (SANS) with neutron contrast variation is ideally suited for studying multi-component assemblies as well as membrane proteins that are stabilized in surfactant micelles or vesicles. SAS is also used for studying dynamic processes of protein fibrillation in amyloid diseases, and pharmaceutical drug delivery. The combination with size-exclusion chromatography further increases the range of SAS applications.The book is written by leading experts in solution SAS methodologies. The principles and theoretical background of various SAS techniques are included, along with practical aspects that range from sample preparation to data presentation for publication. Topics covered include techniques for improving data quality and analysis, as well as different scientific applications of SAS. With abundant illustrations and practical tips, we hope the clear explanations of the principles and the reviews on the latest progresses will serve as a guide through all aspects of biological solution SAS.The scope of this book is particularly relevant for structural biology researchers who are new to SAS. Advanced users of the technique will find it helpful for exploring the diversity of solution SAS methods and applications.« less

Micro-focused Small Angle Neutron Scattering and Imaging for Science and Engineering Using RTP--A Preliminary Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohamed, Abdul Aziz; Al Rashid Megat Ahmad, Megat Harun; Md Idris, Faridah

2010-01-05

Malaysian Nuclear Agency's (Nuclear Malaysia) Small Angle Neutron Scattering (SANS) facility--(MYSANS)--is utilizing low flux of thermal neutron at the agency's 1 MW TRIGA reactor. As the design nature of the 8 m SANS facility can allow object resolution in the range between 5 and 80 nm to be obtained. It can be used to study alloys, ceramics and polymers in certain area of problems that relate to samples containing strong scatterers or contrast. The current SANS system at Malaysian Nuclear Agency is only capable to measure Q in limited range with a PSD (128x128) fixed at 4 m from themore » sample. The existing reactor hall that incorporate this MYSANS facility has a layout that prohibits the rebuilding of MYSANS therefore the position between the wavelength selector (HOPG) and sample and the PSD cannot be increased for wider Q range. The flux of the neutron at current sample holder is very low which around 10{sup 3} n/cm{sup 2}/sec. Thus it is important to rebuild the MYSANS to maximize the utilization of neutron. Over the years, the facility has undergone maintenance and some changes have been made. Modification on secondary shutter and control has been carried out to improve the safety level of the instrument. A compact micro-focus SANS method can suit this objective together with an improve cryostat system. This paper will explain some design concept and approaches in achieving higher flux and the modification needs to establish the micro-focused SANS.« less

Neutron scattering measurements of carbon dioxide adsorption in pores within the Marcellus Shale: Implications for sequestration

USGS Publications Warehouse

Stefanopoulos, Konstantinos L.; Youngs, Tristan G. A.; Sakurovs, Richard; Ruppert, Leslie F.; Bahadur, Jitendra; Melnichenko, Yuri B.

2017-01-01

Shale is an increasingly viable source of natural gas and a potential candidate for geologic CO2sequestration. Understanding the gas adsorption behavior on shale is necessary for the design of optimal gas recovery and sequestration projects. In the present study neutron diffraction and small-angle neutron scattering measurements of adsorbed CO2 in Marcellus Shale samples were conducted on the Near and InterMediate Range Order Diffractometer (NIMROD) at the ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory along an adsorption isotherm of 22 °C and pressures of 25 and 40 bar. Additional measurements were conducted at approximately 22 and 60 °C at the same pressures on the General-Purpose Small-Angle Neutron Scattering (GP-SANS) instrument at Oak Ridge National Laboratory. The structures investigated (pores) for CO2 adsorption range in size from Å level to ∼50 nm. The results indicate that, using the conditions investigated densification or condensation effects occurred in all accessible pores. The data suggest that at 22 °C the CO2 has liquid-like properties when confined in pores of around 1 nm radius at pressures as low as 25 bar. Many of the 2.5 nm pores, 70% of 2 nm pores, most of the <1 nm pores, and all pores <0.25 nm, are inaccessible or closed to CO2, suggesting that despite the vast numbers of micropores in shale, the micropores will be unavailable for storage for geologic CO2 sequestration.

Monte Carlo calculation of large and small-angle electron scattering in air

NASA Astrophysics Data System (ADS)

Cohen, B. I.; Higginson, D. P.; Eng, C. D.; Farmer, W. A.; Friedman, A.; Grote, D. P.; Larson, D. J.

2017-11-01

A Monte Carlo method for angle scattering of electrons in air that accommodates the small-angle multiple scattering and larger-angle single scattering limits is introduced. The algorithm is designed for use in a particle-in-cell simulation of electron transport and electromagnetic wave effects in air. The method is illustrated in example calculations.

SCATTERING OF NEUTRONS BY $alpha$-PARTICLES AT 14.1 Mev

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fasoli, U.; Zago, G.

1963-12-01

The angular distribution of 14.1-Mev neutrons elastically scattered by alpha particles was measured by observing the alpha recoils in a helium-filled cloud chamber. The results are in satisfactory agreement with those previously obtained by others. Inspection of the small-angle region of the measured distribution shows that phase shifts of orbital angular momentum higher than L = 1 are not negligible, although, according to the present experiment, quantitative information on D-waves turns out to be somewhat elusive. The azimuthal angular distribution agrees well with the value P = 0.02 of the neutron beam polarization, as measured by Perkins. (auth)

Precipitation of α' in neutron irradiated commercial FeCrAl alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Field, Kevin G.; Littrell, Kenneth C.; Briggs, Samuel A.

2017-08-17

In this paper, Alkrothal 720 and Kanthal APMT™, two commercial FeCrAl alloys, were neutron irradiated up to damage doses of 7.0 displacements per atom (dpa) in the temperature range of 320 to 382 °C to characterize the α' precipitation in these alloys using small-angle neutron scattering. Both alloys exhibited α' precipitation. Kanthal APMT™ exhibited higher number densities and volume fraction, a result attributed to its higher Cr content compared with Alkrothal 720. Finally, trends observed as a function of damage dose (dpa) are consistent with literature trends for both FeCr and FeCrAl alloys

Charge-dependent conformations and dynamics of pamam dendrimers revealed by neutron scattering and molecular dynamics

NASA Astrophysics Data System (ADS)

Wu, Bin

Neutron scattering and fully atomistic molecular dynamics (MD) are employed to investigate the structural and dynamical properties of polyamidoamine (PAMAM) dendrimers with ethylenediamine (EDA) core under various charge conditions. Regarding to the conformational characteristics, we focus on scrutinizing density profile evolution of PAMAM dendrimers as the molecular charge of dendrimer increases from neutral state to highly charged condition. It should be noted that within the context of small angle neutron scattering (SANS), the dendrimers are composed of hydrocarbon component (dry part) and the penetrating water molecules. Though there have been SANS experiments that studied the charge-dependent structural change of PAMAM dendrimers, their results were limited to the collective behavior of the aforementioned two parts. This study is devoted to deepen the understanding towards the structural responsiveness of intra-molecular polymeric and hydration parts separately through advanced contrast variation SANS data analysis scheme available recently and unravel the governing principles through coupling with MD simulations. Two kinds of acids, namely hydrochloric and sulfuric acids, are utilized to tune the pH condition and hence the molecular charge. As far as the dynamical properties, we target at understanding the underlying mechanism that leads to segmental dynamic enhancement observed from quasielstic neutron scattering (QENS) experiment previously. PAMAM dendrimers have a wealth of potential applications, such as drug delivery agency, energy harvesting medium, and light emitting diodes. More importantly, it is regarded as an ideal system to test many theoretical predictions since dendrimers conjugate both colloid-like globular shape and polymer-like flexible chains. This Ph.D. research addresses two main challenges in studying PAMAM dendrimers. Even though neutron scattering is an ideal tool to study this PAMAM dendrimer solution due to its matching temporal and spatial instrumental scales, understanding experimental results involves extensive and difficult data analysis based on liquid theory and condensed matter physics. Therefore, a model that successfully describes the inter- and intra-dendrimer correlations is crucial in obtaining and delivering reliable information. On the other hand, making meaningful comparisons between molecular dynamics and neutron scattering is a fundamental challenge to link simulations and experiments at the nano-scale. This challenge stems from our approach to utilize MD simulation to explain the underlying mechanism of experimental observation. The SANS measurements were conducted on a series of SANS spectrometers including the Extended Q-Range Small-Angle Neutron Scattering Diffractometer (EQ-SANS) and the General-Purpose Small-Angle Neutron Scattering Diffractometer (GP-SANS) at the Oak Ridge National Laboratory (ORNL), and NG7 Small Angle Neutron Scattering Spectrometer at National Institute of Standards (NIST) and Technology in U.S.A., large dynamic range small-angle diffractometer D22 at Institut Laue-Langevin (ILL) in France, and 40m-SANS Spectrometer at Korea Atomic Energy Research Institute (KAERI) in Korea. On the other hand, the Amber molecular dynamics simulation package is utilized to carry out the computational study. In this dissertation, the following observations have been revealed. The previously developed theoretical model for polyelectrolyte dendrimers are adopted to analyze SANS measurements and superb model fitting quality is found. Coupling with advanced contrast variation small angle neutron scattering (CVSANS) data analysis scheme reported recently, the intra-dendrimer hydration and hydrocarbon components distributions are revealed experimentally. The results indeed indicate that the maximum density is located in the molecular center rather than periphery, which is consistent to previous SANS studies and the back-folding picture of PAMAM dendrimers. According to this picture, at neutral condition, the exterior residues folding back into interior would necessarily lead to higher entropy and equivalently lower free energy and thereby is energetically favored. As one decreases the pH condition of PAMAM dendrimers, the constituent residues would carry positive charges. The resultant inter-residue Coulomb repulsion would naturally result in conformational evolution. We found from CVSANS analysis that when dendrimers are charged by different acids, this conformational evolution is not the same. For dendrimers charged by DCl, the mass is seen to relocate from molecular interior to periphery. Nevertheless, those acidified by D 2SO4 exhibit surprisingly minor structural change under variation of molecular charge. To explain the above observation, we performed MD simulations and calculated the excess free energy of Cl- and SO 42- counterions. The binding between sulfate ions and charged amines of PAMAM dendrimers are found to be much stronger than the case for chlorides. This more energetic binding would serve as better screening effect among charged residues. Consequently, electrostatic repulsion triggered outstretching tendency is effectively diminished. In order to make direct comparison between MD simulations and neutron scattering experiments, we proposed and implemented a rigorous method, which incorporates the contribution from those invasive water molecules, to calculate scattering functions of a single PAMAM dendrimer using equilibrium MD trajectories. The bridge between neutron scattering experiments and MD simulation is successfully established. Aside from structural comparisons between MD simulations and experiments, we utilized MD simulation to decipher the previously reported QENS experimental observation that the segmental dynamics of PAMAM dendrimer would enhance with increasing molecular charge. We pursued the mechanism from the perspective of hydrocarbon component of dendrimer and solvent (water) interaction as a form similar to hydrogen bonding. It is found that the population of this bonding would increase and the corresponding relaxation would slow down as molecular charge increases. We perceive that through more and longer interaction between penetrating water molecules and polymeric part of dendrimer, the dynamics of latter could be enhanced.

Multiple-Fiber-Optic Probe For Light-Scattering Measurements

NASA Technical Reports Server (NTRS)

Dhadwal, Harbans Singh; Ansari, Rafat R.

1996-01-01

Multiple-fiber-optical probe developed for use in measuring light scattered at various angles from specimens of materials. Designed for both static and dynamic light-scattering measurements of colloidal dispersions. Probe compact, rugged unit containing no moving parts and remains stationary during operation. Not restricted to operation in controlled, research-laboratory environment. Positioned inside or outside light-scattering chamber. Provides simultaneous measurements at small angular intervals over range of angles, made to include small scattering angles by orienting probe in appropriate direction.

MCNP simulation to optimise in-pile and shielding parts of the Portuguese SANS instrument.

PubMed

Gonçalves, I F; Salgado, J; Falcão, A; Margaça, F M A; Carvalho, F G

2005-01-01

A Small Angle Neutron Scattering instrument is being installed at one end of the tangential beam tube of the Portuguese Research Reactor. The instrument is fed using a neutron scatterer positioned in the middle of the beam tube. The scatterer consists of circulating H2O contained in a hollow disc of Al. The in-pile shielding components and the shielding installed around the neutron selector have been the object of an MCNP simulation study. The quantities calculated were the neutron and gamma-ray fluxes in different positions, the energy deposited in the material by the neutron and gamma-ray fields, the material activation resulting from the neutron field and radiation doses at the exit wall of the shutter and around the shielding. The MCNP results are presented and compared with results of an analytical approach and with experimental data collected after installation.

Solid state neutron detector array

DOEpatents

Seidel, J.G.; Ruddy, F.H.; Brandt, C.D.; Dulloo, A.R.; Lott, R.G.; Sirianni, E.; Wilson, R.O.

1999-08-17

A neutron detector array is capable of measuring a wide range of neutron fluxes. The array includes multiple semiconductor neutron detectors. Each detector has a semiconductor active region that is resistant to radiation damage. In one embodiment, the array preferably has a relatively small size, making it possible to place the array in confined locations. The ability of the array to detect a wide range of neutron fluxes is highly advantageous for many applications such as detecting neutron flux during start up, ramp up and full power of nuclear reactors. 7 figs.

SNM detection with an optimized water Cherenkov neutron detector

NASA Astrophysics Data System (ADS)

Dazeley, S.; Sweany, M.; Bernstein, A.

2012-11-01

Special Nuclear Material (SNM) can either spontaneously fission or be induced to do so: either case results in neutron emission. For this reason, neutron detection performs a crucial role in the functionality of Radiation Portal Monitoring (RPM) devices. Since neutrons are highly penetrating and difficult to shield, they could potentially be detected escaping even a well-shielded cargo container. If the shielding were sophisticated, detecting escaping neutrons would require a highly efficient detector with close to full solid angle coverage. In 2008, we reported the successful detection of neutrons with a 250 liter (l) gadolinium doped water Cherenkov prototype [1]—a technology that could potentially be employed cost effectively with full solid angle coverage. More recently we have built and tested both 1-kl and 3.5-kl versions [2], demonstrating that very large, cost effective, non-flammable and environmentally benign neutron detectors can be operated efficiently without being overwhelmed by background. In this paper, we present a new design for a modular system of water-based neutron detectors that could be deployed as a real RPM. The modules contain a number of optimizations that have not previously been combined within a single system. We present simulations of the new system, based on the performance of our previous detectors. Our simulations indicate that an optimized system such as is presented here could achieve SNM sensitivity competitive with a large 3He-based system. Moreover, the realization of large, cost effective neutron detectors could, for the first time, enable the detection of multiple neutrons per fission from within a large object such as a cargo container. Such a signal would provide a robust indication of the presence of fissioning material, reducing the frequency of false alarms while increasing sensitivity.

SNM Detection with an Optimized Water Cherenkov Neutron Detector

DOE PAGES

Dazeley, S.; Sweany, M.; Bernstein, A.

2012-07-23

Special Nuclear Material (SNM) can either spontaneously fission or be induced to do so: either case results in neutron emission. For this reason, neutron detection performs a crucial role in the functionality of Radiation Portal Monitoring (RPM) devices. Since neutrons are highly penetrating and difficult to shield, they could potentially be detected escaping even a well-shielded cargo container. If the shielding were sophisticated, detecting escaping neutrons would require a highly efficient detector with close to full solid angle coverage. In 2008, we reported the successful detection of neutrons with a 250 liter (l) gadolinium doped water Cherenkov prototype—a technology thatmore » could potentially be employed cost effectively with full solid angle coverage. More recently we have built and tested both 1-kl and 3.5-kl versions, demonstrating that very large, cost effective, non-flammable and environmentally benign neutron detectors can be operated efficiently without being overwhelmed by background. In our paper, we present a new design for a modular system of water-based neutron detectors that could be deployed as a real RPM. The modules contain a number of optimizations that have not previously been combined within a single system. We present simulations of the new system, based on the performance of our previous detectors. These simulations indicate that an optimized system such as is presented here could achieve SNM sensitivity competitive with a large 3He-based system. Moreover, the realization of large, cost effective neutron detectors could, for the first time, enable the detection of multiple neutrons per fission from within a large object such as a cargo container. Such a signal would provide a robust indication of the presence of fissioning material, reducing the frequency of false alarms while increasing sensitivity.« less

CORRECTIONS ASSOCIATED WITH ON-PHANTOM CALIBRATIONS OF NEUTRON PERSONAL DOSEMETERS.

PubMed

Hawkes, N P; Thomas, D J; Taylor, G C

2016-09-01

The response of neutron personal dosemeters as a function of neutron energy and angle of incidence is typically measured by mounting the dosemeters on a slab phantom and exposing them to neutrons from an accelerator-based or radionuclide source. The phantom is placed close to the source (75 cm) so that the effect of scattered neutrons is negligible. It is usual to mount several dosemeters on the phantom together. Because the source is close, the source distance and the neutron incidence angle vary significantly over the phantom face, and each dosemeter may receive a different dose equivalent. This is particularly important when the phantom is angled away from normal incidence. With accelerator-produced neutrons, the neutron energy and fluence vary with emission angle relative to the charged particle beam that produces the neutrons, contributing further to differences in dose equivalent, particularly when the phantom is located at other than the straight-ahead position (0° to the beam). Corrections for these effects are quantified and discussed in this article. © Crown copyright 2015.

Magnetic compound refractive lens for focusing and polarizing cold neutron beams.

PubMed

Littrell, K C; te Velthuis, S G E; Felcher, G P; Park, S; Kirby, B J; Fitzsimmons, M R

2007-03-01

Biconcave cylindrical lenses are used to focus beams of x rays or neutrons using the refractive properties of matter. In the case of neutrons, the refractive properties of magnetic induction can similarly focus and simultaneously polarize the neutron beam without the concomitant attenuation of matter. This concept of a magnetic refractive lens was tested using a compound lens consisting of 99 pairs of cylindrical permanent magnets. The assembly successfully focused the intensity of a white beam of cold neutrons of one spin state at the detector, while defocusing the other. This experiment confirmed that a lens of this nature may boost the intensity locally by almost an order of magnitude and create a polarized beam. An estimate of the performance of a more practically dimensioned device suitable for incorporation in reflectometers and slit-geometry small angle scattering instruments is given.

Magnetic small-angle neutron scattering of bulk ferromagnets.

PubMed

Michels, Andreas

2014-09-24

We summarize recent theoretical and experimental work in the field of magnetic small-angle neutron scattering (SANS) of bulk ferromagnets. The response of the magnetization to spatially inhomogeneous magnetic anisotropy and magnetostatic stray fields is computed using linearized micromagnetic theory, and the ensuing spin-misalignment SANS is deduced. Analysis of experimental magnetic-field-dependent SANS data of various nanocrystalline ferromagnets corroborates the usefulness of the approach, which provides important quantitative information on the magnetic-interaction parameters such as the exchange-stiffness constant, the mean magnetic anisotropy field, and the mean magnetostatic field due to jumps ΔM of the magnetization at internal interfaces. Besides the value of the applied magnetic field, it turns out to be the ratio of the magnetic anisotropy field Hp to ΔM, which determines the properties of the magnetic SANS cross-section of bulk ferromagnets; specifically, the angular anisotropy on a two-dimensional detector, the asymptotic power-law exponent, and the characteristic decay length of spin-misalignment fluctuations. For the two most often employed scattering geometries where the externally applied magnetic field H0 is either perpendicular or parallel to the wave vector k0 of the incoming neutron beam, we provide a compilation of the various unpolarized, half-polarized (SANSPOL), and uniaxial fully-polarized (POLARIS) SANS cross-sections of magnetic materials.

FASTER 3: A generalized-geometry Monte Carlo computer program for the transport of neutrons and gamma rays. Volume 1: Summary report

NASA Technical Reports Server (NTRS)

Jordan, T. M.

1970-01-01

The theory used in FASTER-III, a Monte Carlo computer program for the transport of neutrons and gamma rays in complex geometries, is outlined. The program includes the treatment of geometric regions bounded by quadratic and quadric surfaces with multiple radiation sources which have specified space, angle, and energy dependence. The program calculates, using importance sampling, the resulting number and energy fluxes at specified point, surface, and volume detectors. It can also calculate minimum weight shield configuration meeting a specified dose rate constraint. Results are presented for sample problems involving primary neutron, and primary and secondary photon, transport in a spherical reactor shield configuration.

Monte Carlo calculation of large and small-angle electron scattering in air

DOE PAGES

Cohen, B. I.; Higginson, D. P.; Eng, C. D.; ...

2017-08-12

A Monte Carlo method for angle scattering of electrons in air that accommodates the small-angle multiple scattering and larger-angle single scattering limits is introduced. In this work, the algorithm is designed for use in a particle-in-cell simulation of electron transport and electromagnetic wave effects in air. The method is illustrated in example calculations.

Summary of the Effort to Use Active-induced Time Correlation Techniques to Measure the Enrichment of HEU

DOE Office of Scientific and Technical Information (OSTI.GOV)

McConchie, Seth M.; Crye, Jason Michael; Pena, Kirsten

2015-09-30

This document summarizes the effort to use active-induced time correlation techniques to measure the enrichment of bulk quantities of enriched uranium. In summary, these techniques use an external source to initiate fission chains, and the time distribution of the detected fission chain neutrons is sensitive to the fissile material enrichment. The number of neutrons emitted from a chain is driven by the multiplication of the item, and the enrichment is closely coupled to the multiplication of the item. As the enrichment increases (decreases), the multiplication increases (decreases) if the geometry is held constant. The time distribution of fission chain neutronsmore » is a complex function of the enrichment and material configuration. The enrichment contributes to the probability of a subsequent fission in a chain via the likelihood of fissioning on an even-numbered isotope versus an odd-numbered isotope. The material configuration contributes to the same probability via solid angle effects for neutrons inducing subsequent fissions and the presence of any moderating material. To simplify the ability to accurately measure the enrichment, an associated particle imaging (API) D-T neutron generator and an array of plastic scintillators are used to simultaneously image the item and detect the fission chain neutrons. The image is used to significantly limit the space of enrichment and material configuration and enable the enrichment to be determined unambiguously.« less

Structural changes in C–S–H gel during dissolution: Small-angle neutron scattering and Si-NMR characterization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trapote-Barreira, Ana, E-mail: anatrapotebarreira@gmail.com; Porcar, Lionel; Large Scale Structure Group, Institut Laue Langevin, Grenoble

2015-06-15

Flow-through experiments were conducted to study the calcium–silicate–hydrate (C–S–H) gel dissolution kinetics. During C–S–H gel dissolution the initial aqueous Ca/Si ratio decreases to reach the stoichiometric value of the Ca/Si ratio of a tobermorite-like phase (Ca/Si = 0.83). As the Ca/Si ratio decreases, the solid C–S–H dissolution rate increases from (4.5 × 10{sup −} {sup 14} to 6.7 × 10{sup −} {sup 12}) mol m{sup −} {sup 2} s{sup −} {sup 1}. The changes in the microstructure of the dissolving C–S–H gel were characterized by small-angle neutron scattering (SANS) and {sup 29}Si magic-angle-spinning nuclear magnetic resonance ({sup 29}Si-MAS NMR). Themore » SANS data were fitted using a fractal model. The SANS specific surface area tends to increase with time and the obtained fit parameters reflect the changes in the nanostructure of the dissolving solid C–S–H within the gel. The {sup 29}Si MAS NMR analyses show that with dissolution the solid C–S–H structure tends to a more ordered tobermorite structure, in agreement with the Ca/Si ratio evolution.« less

SANS contrast variation study of magnetoferritin structure at various iron loading

NASA Astrophysics Data System (ADS)

Melnikova, Lucia; Petrenko, Viktor I.; Avdeev, Mikhail V.; Ivankov, Oleksandr I.; Bulavin, Leonid A.; Garamus, Vasil M.; Almásy, László; Mitroova, Zuzana; Kopcansky, Peter

2015-03-01

Magnetoferritin, a synthetic derivate of iron storage protein - ferritin, has been synthesized with different iron oxide loading values. Small-angle neutron scattering experiments were applied to study the structure of magnetoferritin solutions using contrast variation method by varying the light to heavy water ratio of the solvent. Higher iron loading leads to increase of the neutron scattering length density of magnetoferritin and also to the increase of the polydispersity of complexes. The formation of the magnetic core and the variation of the protein shell structure upon iron loading are concluded.

Observation of events with an energetic forward neutron in deep inelastic scattering at HERA

NASA Astrophysics Data System (ADS)

Derrick, M.; Krakauer, D.; Magill, S.; Mikunas, D.; Musgrave, B.; Okrasinski, J. R.; Repond, J.; Stanek, R.; Talaga, R. L.; Zhang, H.; Mattingly, M. C. K.; Bari, G.; Basile, M.; Bellagamba, L.; Boscherini, D.; Bruni, A.; Bruni, G.; Bruni, P.; Cara Romeo, G.; Castellini, G.; Cifarelli, L.; Cindolo, F.; Contin, A.; Corradi, M.; Gialas, I.; Giusti, P.; Iacobucci, G.; Laurenti, G.; Levi, G.; Margotti, A.; Massam, T.; Nania, R.; Palmonari, F.; Polini, A.; Sartorelli, G.; Zamora Garcia, Y.; Zichichi, A.; Amelung, C.; Bornheim, A.; Crittenden, J.; Deffner, R.; Doeker, T.; Eckert, M.; Feld, L.; Frey, A.; Geerts, M.; Grothe, M.; Hartmann, H.; Heinloth, K.; Heinz, L.; Hilger, E.; Jakob, H.-P.; Katz, U. F.; Mengel, S.; Paul, E.; Pfeiffer, M.; Rembser, Ch.; Schramm, D.; Stamm, J.; Wedemeyer, R.; Campbell-Robson, S.; Cassidy, A.; Cottingham, W. N.; Dyce, N.; Foster, B.; George, S.; Hayes, M. E.; Heath, G. P.; Heath, H. F.; Piccioni, D.; Roff, D. G.; Tapper, R. J.; Yoshida, R.; Arneodo, M.; Ayad, R.; Capua, M.; Garfagnini, A.; Iannotti, L.; Schioppa, M.; Susinno, G.; Caldwell, A.; Cartiglia, N.; Jing, Z.; Liu, W.; Parsons, J. A.; Titz, S.; Sciulli, F.; Straub, P. B.; Wai, L.; Yang, S.; Zhu, Q.; Borzemski, P.; Chwastowski, J.; Eskreys, A.; Jakubowski, Z.; Przybycień, M. B.; Zachara, M.; Zawiejski, L.; Adamczyk, L.; Bednarek, B.; Jeleń, K.; Kisielewska, D.; Kowalski, T.; Przybycień, M.; Rulikowska-Zarȩbska, E.; Suszycki, L.; Zajaç, J.; Duliński, Z.; Kotański, A.; Abbiendi, G.; Bauerdick, L. A. T.; Behrens, U.; Beier, H.; Bienlein, J. K.; Cases, G.; Deppe, O.; Desler, K.; Drews, G.; Flasiński, M.; Gilkinson, D. J.; Glasman, C.; Göttlicher, P.; Große-Knetter, J.; Haas, T.; Hain, W.; Hasell, D.; Heßling, H.; Iga, Y.; Johnson, K. F.; Joos, P.; Kasemann, M.; Klanner, R.; Koch, W.; Kötz, U.; Kowalski, H.; Labs, J.; Ladage, A.; Löhr, B.; Löwe, M.; Lüke, D.; Mainusch, J.; Mańczak, O.; Milewski, J.; Monteiro, T.; Ng, J. S. T.; Notz, D.; Ohrenberg, K.; Poitrzkowski, K.; Roco, M.; Rohde, M.; Roldán, J.; Schneekloth, U.; Schulz, W.; Selonke, F.; Surrow, B.; Voß, T.; Westphal, D.; Wolf, G.; Wollmer, U.; Youngman, C.; Zeuner, W.; Grabosch, H. J.; Kharchilava, A.; Mari, S. M.; Meyer, A.; Schlenstedt, S.; Wulff, N.; Barbagli, G.; Gallo, E.; Pelfer, P.; Maccarrone, G.; De Pasquale, S.; Votano, L.; Bamberger, A.; Eisenhardt, S.; Trefzger, T.; Wölfle, S.; Bromley, J. T.; Brook, N. H.; Bussey, P. J.; Doyle, A. T.; Saxon, D. H.; Sinclair, L. E.; Utley, M. L.; Wilson, A. S.; Dannemann, A.; Holm, U.; Horstmann, D.; Sinkus, R.; Wick, K.; Burow, B. D.; Hagge, L.; Lohrmann, E.; Poelz, G.; Schott, W.; Zetsche, F.; Bacon, T. C.; Brümmer, N.; Butterworth, I.; Harris, V. L.; Howell, G.; Hung, B. H. Y.; Lamberti, L.; Long, K. R.; Miller, D. B.; Pavel, N.; Prinias, A.; Sedgbeer, J. K.; Sideris, D.; Whitfield, A. F.; Mallik, U.; Wang, M. Z.; Wang, S. M.; Wu, J. T.; Cloth, P.; Filges, D.; An, S. H.; Cho, G. H.; Ko, B. J.; Lee, S. B.; Nam, S. W.; Park, H. S.; Park, S. K.; Kartik, S.; Kim, H.-J.; McNeil, R. R.; Metcalf, W.; Nadendla, V. K.; Barreiro, F.; Fernandez, J. P.; Graciani, R.; Hernández, J. M.; Hervás, L.; Labarga, L.; Martinez, M.; del Peso, J.; Puga, J.; Terron, J.; de Trocóniz, J. F.; Corriveau, F.; Hanna, D. S.; Hartmann, J.; Hung, L. W.; Lim, J. N.; Matthews, C. G.; Patel, P. M.; Riveline, M.; Stairs, D. G.; St-Laurent, M.; Ullmann, R.; Zacek, G.; Tsurugai, T.; Bashkirov, V.; Dolgoshein, B. A.; Stifutkin, A.; Bashindzhagyan, G. L.; Ermolov, P. F.; Gladilin, L. K.; Golubkov, Yu. A.; Kobrin, V. D.; Korzhavina, I. A.; Kuzmin, V. A.; Lukina, O. Yu.; Proskuryakov, A. S.; Savin, A. A.; Shcheglova, L. M.; Solomin, A. N.; Zotov, N. P.; Botje, M.; Chlebana, F.; Engelen, J.; de Kamps, M.; Kooijman, P.; Kruse, A.; van Sighem, A.; Tiecke, H.; Verkerke, W.; Vossebeld, J.; Vreeswijk, M.; Wiggers, L.; de Wolf, E.; van Woudenberg, R.; Acosta, D.; Bylsma, B.; Durkin, L. S.; Gilmore, J.; Li, C.; Ling, T. Y.; Nylander, P.; Park, I. H.; Romanowski, T. A.; Bailey, D. S.; Cashmore, R. J.; Cooper-Sarkar, A. M.; Devenish, R. C. E.; Harnew, N.; Lancaster, M.; Lindemann, L.; McFall, J. D.; Nath, C.; Noyes, V. A.; Quadt, A.; Tickner, J. R.; Uijterwaal, H.; Walczak, R.; Waters, D. S.; Wilson, F. F.; Yip, T.; Bertolin, A.; Brugnera, R.; Carlin, R.; Dal Corso, F.; De Giorgi, M.; Dosselli, U.; Limentani, S.; Morandin, M.; Posocco, M.; Stanco, L.; Stroili, R.; Voci, C.; Zuin, F.; Bulmahn, J.; Feild, R. G.; Oh, B. Y.; Whitmore, J. J.; D'Agostini, G.; Marini, G.; Nigro, A.; Tassi, E.; Hart, J. C.; McCubbin, N. A.; Shah, T. P.; Barberis, E.; Dubbs, T.; Heusch, C.; Van Hook, M.; Lockman, W.; Rahn, J. T.; Sadrozinski, H. F.-W.; Seiden, A.; Williams, D. C.; Biltzinger, J.; Seifert, R. J.; Schwarzer, O.; Walenta, A. H.; Zech, G.; Abramowicz, H.; Briskin, G.; Dagan, S.; Levy, A.; Fleck, J. I.; Inuzuka, M.; Ishii, T.; Kuze, M.; Mine, S.; Nakao, M.; Suzuki, I.; Tokushuku, K.; Umemori, K.; Yamada, S.; Yamazaki, Y.; Chiba, M.; Hamatsu, R.; Hirose, T.; Homma, K.; Kitamura, S.; Matsushita, T.; Yamauchi, K.; Cirio, R.; Costa, M.; Ferrero, M. I.; Maselli, S.; Peroni, C.; Sacchi, R.; Solano, A.; Staiano, A.; Dardo, M.; Bailey, D. C.; Benard, F.; Brkic, M.; Fagerstroem, C.-P.; Hartner, G. F.; Joo, K. K.; Levman, G. M.; Martin, J. F.; Orr, R. S.; Polenz, S.; Sampson, C. R.; Simmons, D.; Teuscher, R. J.; Butterworth, J. M.; Catterall, C. D.; Jones, T. W.; Kaziewicz, P. B.; Lane, J. B.; Saunders, R. L.; Shulman, J.; Sutton, M. R.; Lu, B.; Mo, L. W.; Bogusz, W.; Ciborowski, J.; Gajewski, J.; Grzelak, G.; Kasprzak, M.; Krzyżanowski, M.; Muchorowski, K.; Nowak, R. J.; Pawlak, J. M.; Tymieniecka, T.; Wróblewski, A. K.; Zakrzewski, J. A.; Żarnecki, A. F.; Adamus, M.; Coldewey, C.; Eisenberg, Y.; Hochman, D.; Karshon, U.; Revel, D.; Zer-Zion, D.; Badgett, W. F.; Breitweg, J.; Chapin, D.; Cross, R.; Dasu, S.; Foudas, C.; Loveless, R. J.; Mattingly, S.; Reeder, D. D.; Silverstein, S.; Smith, W. H.; Vaiciulis, A.; Wodarczyk, M.; Bhadra, S.; Cardy, M. L.; Fagerstroem, C.-P.; Frisken, W. R.; Furutani, K. M.; Khakzad, M.; Murray, W. N.; Schmidke, W. B.; ZEUS Collaboration

1996-02-01

In deep inelastic neutral current scattering of positrons and protons at the center of mass energy of 300 GeV, we observe, with the ZEUS detector, events with a high energy neutron produced at very small scattering angles with respect to the proton direction. The events constitute a fixed fraction of the deep inelastic, neutral current event sample independent of Bjorken x and Q2 in the range 3 · 10 -4 < xBJ < 6 · 10 -3 and 10 < Q2 < 100 GeV 2.

A Search for Point Sources of EeV Neutrons

NASA Astrophysics Data System (ADS)

Pierre Auger Collaboration; Abreu, P.; Aglietta, M.; Ahlers, M.; Ahn, E. J.; Albuquerque, I. F. M.; Allard, D.; Allekotte, I.; Allen, J.; Allison, P.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Alves Batista, R.; Ambrosio, M.; Aminaei, A.; Anchordoqui, L.; Andringa, S.; Antiči'c, T.; Aramo, C.; Arganda, E.; Arqueros, F.; Asorey, H.; Assis, P.; Aublin, J.; Ave, M.; Avenier, M.; Avila, G.; Badescu, A. M.; Balzer, M.; Barber, K. B.; Barbosa, A. F.; Bardenet, R.; Barroso, S. L. C.; Baughman, B.; Bäuml, J.; Baus, C.; Beatty, J. J.; Becker, K. H.; Bellétoile, A.; Bellido, J. A.; BenZvi, S.; Berat, C.; Bertou, X.; Biermann, P. L.; Billoir, P.; Blanco, F.; Blanco, M.; Bleve, C.; Blümer, H.; Boháčová, M.; Boncioli, D.; Bonifazi, C.; Bonino, R.; Borodai, N.; Brack, J.; Brancus, I.; Brogueira, P.; Brown, W. C.; Bruijn, R.; Buchholz, P.; Bueno, A.; Buroker, L.; Burton, R. E.; Caballero-Mora, K. S.; Caccianiga, B.; Caramete, L.; Caruso, R.; Castellina, A.; Catalano, O.; Cataldi, G.; Cazon, L.; Cester, R.; Chauvin, J.; Cheng, S. H.; Chiavassa, A.; Chinellato, J. A.; Chirinos Diaz, J.; Chudoba, J.; Cilmo, M.; Clay, R. W.; Cocciolo, G.; Collica, L.; Coluccia, M. R.; Conceição, R.; Contreras, F.; Cook, H.; Cooper, M. J.; Coppens, J.; Cordier, A.; Coutu, S.; Covault, C. E.; Creusot, A.; Criss, A.; Cronin, J.; Curutiu, A.; Dagoret-Campagne, S.; Dallier, R.; Daniel, B.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; De Domenico, M.; De Donato, C.; de Jong, S. J.; De La Vega, G.; de Mello Junior, W. J. M.; de Mello Neto, J. R. T.; De Mitri, I.; de Souza, V.; de Vries, K. D.; del Peral, L.; del Río, M.; Deligny, O.; Dembinski, H.; Dhital, N.; Di Giulio, C.; Díaz Castro, M. L.; Diep, P. N.; Diogo, F.; Dobrigkeit, C.; Docters, W.; D'Olivo, J. C.; Dong, P. N.; Dorofeev, A.; dos Anjos, J. C.; Dova, M. T.; D'Urso, D.; Dutan, I.; Ebr, J.; Engel, R.; Erdmann, M.; Escobar, C. O.; Espadanal, J.; Etchegoyen, A.; Facal San Luis, P.; Falcke, H.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Ferguson, A. P.; Fick, B.; Figueira, J. M.; Filevich, A.; Filipčič, A.; Fliescher, S.; Fracchiolla, C. E.; Fraenkel, E. D.; Fratu, O.; Fröhlich, U.; Fuchs, B.; Gaior, R.; Gamarra, R. F.; Gambetta, S.; García, B.; Garcia Roca, S. T.; Garcia-Gamez, D.; Garcia-Pinto, D.; Gascon Bravo, A.; Gemmeke, H.; Ghia, P. L.; Giller, M.; Gitto, J.; Glass, H.; Gold, M. S.; Golup, G.; Gomez Albarracin, F.; Gómez Berisso, M.; Gómez Vitale, P. F.; Gonçalves, P.; Gonzalez, J. G.; Gookin, B.; Gorgi, A.; Gouffon, P.; Grashorn, E.; Grebe, S.; Griffith, N.; Grigat, M.; Grillo, A. F.; Guardincerri, Y.; Guarino, F.; Guedes, G. P.; Hansen, P.; Harari, D.; Harrison, T. A.; Harton, J. L.; Haungs, A.; Hebbeker, T.; Heck, D.; Herve, A. E.; Hojvat, C.; Hollon, N.; Holmes, V. C.; Homola, P.; Hörandel, J. R.; Horvath, P.; Hrabovský, M.; Huber, D.; Huege, T.; Insolia, A.; Ionita, F.; Italiano, A.; Jansen, S.; Jarne, C.; Jiraskova, S.; Josebachuili, M.; Kadija, K.; Kampert, K. H.; Karhan, P.; Kasper, P.; Katkov, I.; Kégl, B.; Keilhauer, B.; Keivani, A.; Kelley, J. L.; Kemp, E.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Knapp, J.; Koang, D.-H.; Kotera, K.; Krohm, N.; Krömer, O.; Kruppke-Hansen, D.; Kuempel, D.; Kulbartz, J. K.; Kunka, N.; La Rosa, G.; Lachaud, C.; LaHurd, D.; Latronico, L.; Lauer, R.; Lautridou, P.; Le Coz, S.; Leão, M. S. A. B.; Lebrun, D.; Lebrun, P.; Leigui de Oliveira, M. A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; López, R.; Lopez Agüera, A.; Louedec, K.; Lozano Bahilo, J.; Lu, L.; Lucero, A.; Ludwig, M.; Lyberis, H.; Maccarone, M. C.; Macolino, C.; Maldera, S.; Maller, J.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Marin, J.; Marin, V.; Maris, I. C.; Marquez Falcon, H. R.; Marsella, G.; Martello, D.; Martin, L.; Martinez, H.; Martínez Bravo, O.; Martraire, D.; Masías Meza, J. J.; Mathes, H. J.; Matthews, J.; Matthews, J. A. J.; Matthiae, G.; Maurel, D.; Maurizio, D.; Mazur, P. O.; Medina-Tanco, G.; Melissas, M.; Melo, D.; Menichetti, E.; Menshikov, A.; Mertsch, P.; Meurer, C.; Meyhandan, R.; Mi'canovi'c, S.; Micheletti, M. I.; Minaya, I. A.; Miramonti, L.; Molina-Bueno, L.; Mollerach, S.; Monasor, M.; Monnier Ragaigne, D.; Montanet, F.; Morales, B.; Morello, C.; Moreno, E.; Moreno, J. C.; Mostafá, M.; Moura, C. A.; Muller, M. A.; Müller, G.; Münchmeyer, M.; Mussa, R.; Navarra, G.; Navarro, J. L.; Navas, S.; Necesal, P.; Nellen, L.; Nelles, A.; Neuser, J.; Nhung, P. T.; Niechciol, M.; Niemietz, L.; Nierstenhoefer, N.; Nitz, D.; Nosek, D.; Nožka, L.; Oehlschläger, J.; Olinto, A.; Ortiz, M.; Pacheco, N.; Pakk Selmi-Dei, D.; Palatka, M.; Pallotta, J.; Palmieri, N.; Parente, G.; Parizot, E.; Parra, A.; Pastor, S.; Paul, T.; Pech, M.; Peķala, J.; Pelayo, R.; Pepe, I. M.; Perrone, L.; Pesce, R.; Petermann, E.; Petrera, S.; Petrolini, A.; Petrov, Y.; Pfendner, C.; Piegaia, R.; Pierog, T.; Pieroni, P.; Pimenta, M.; Pirronello, V.; Platino, M.; Plum, M.; Ponce, V. H.; Pontz, M.; Porcelli, A.; Privitera, P.; Prouza, M.; Quel, E. J.; Querchfeld, S.; Rautenberg, J.; Ravel, O.; Ravignani, D.; Revenu, B.; Ridky, J.; Riggi, S.; Risse, M.; Ristori, P.; Rivera, H.; Rizi, V.; Roberts, J.; Rodrigues de Carvalho, W.; Rodriguez, G.; Rodriguez Cabo, I.; Rodriguez Martino, J.; Rodriguez Rojo, J.; Rodríguez-Frías, M. D.; Ros, G.; Rosado, J.; Rossler, T.; Roth, M.; Rouillé-d'Orfeuil, B.; Roulet, E.; Rovero, A. C.; Rühle, C.; Saftoiu, A.; Salamida, F.; Salazar, H.; Salesa Greus, F.; Salina, G.; Sánchez, F.; Santo, C. E.; Santos, E.; Santos, E. M.; Sarazin, F.; Sarkar, B.; Sarkar, S.; Sato, R.; Scharf, N.; Scherini, V.; Schieler, H.; Schiffer, P.; Schmidt, A.; Scholten, O.; Schoorlemmer, H.; Schovancova, J.; Schovánek, P.; Schröder, F.; Schulte, S.; Schuster, D.; Sciutto, S. J.; Scuderi, M.; Segreto, A.; Settimo, M.; Shadkam, A.; Shellard, R. C.; Sidelnik, I.; Sigl, G.; Silva Lopez, H. H.; Sima, O.; 'Smiałkowski, A.; Šmída, R.; Snow, G. R.; Sommers, P.; Sorokin, J.; Spinka, H.; Squartini, R.; Srivastava, Y. N.; Stanic, S.; Stapleton, J.; Stasielak, J.; Stephan, M.; Stutz, A.; Suarez, F.; Suomijärvi, T.; Supanitsky, A. D.; Šuša, T.; Sutherland, M. S.; Swain, J.; Szadkowski, Z.; Szuba, M.; Tapia, A.; Tartare, M.; Taşcău, O.; Tcaciuc, R.; Thao, N. T.; Thomas, D.; Tiffenberg, J.; Timmermans, C.; Tkaczyk, W.; Todero Peixoto, C. J.; Toma, G.; Tomankova, L.; Tomé, B.; Tonachini, A.; Travnicek, P.; Tridapalli, D. B.; Tristram, G.; Trovato, E.; Tueros, M.; Ulrich, R.; Unger, M.; Urban, M.; Valdés Galicia, J. F.; Valiño, I.; Valore, L.; van Aar, G.; van den Berg, A. M.; van Vliet, A.; Varela, E.; Vargas Cárdenas, B.; Vázquez, J. R.; Vázquez, R. A.; Veberič, D.; Verzi, V.; Vicha, J.; Videla, M.; Villaseñor, L.; Wahlberg, H.; Wahrlich, P.; Wainberg, O.; Walz, D.; Watson, A. A.; Weber, M.; Weidenhaupt, K.; Weindl, A.; Werner, F.; Westerhoff, S.; Whelan, B. J.; Widom, A.; Wieczorek, G.; Wiencke, L.; Wilczyńska, B.; Wilczyński, H.; Will, M.; Williams, C.; Winchen, T.; Wommer, M.; Wundheiler, B.; Yamamoto, T.; Yapici, T.; Younk, P.; Yuan, G.; Yushkov, A.; Zamorano Garcia, B.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zaw, I.; Zepeda, A.; Zhou, J.; Zhu, Y.; Zimbres Silva, M.; Ziolkowski, M.

2012-12-01

A thorough search of the sky exposed at the Pierre Auger Cosmic Ray Observatory reveals no statistically significant excess of events in any small solid angle that would be indicative of a flux of neutral particles from a discrete source. The search covers from -90° to +15° in declination using four different energy ranges above 1 EeV (1018 eV). The method used in this search is more sensitive to neutrons than to photons. The upper limit on a neutron flux is derived for a dense grid of directions for each of the four energy ranges. These results constrain scenarios for the production of ultrahigh energy cosmic rays in the Galaxy.

MONDO: A neutron tracker for particle therapy secondary emission fluxes measurements

NASA Astrophysics Data System (ADS)

Marafini, M.; Patera, V.; Pinci, D.; Sarti, A.; Sciubba, A.; Spiriti, E.

2016-07-01

Cancer treatment is performed, in Particle Therapy, using accelerated charged particles whose high irradiation precision and conformity allows the tumor destruction while sparing the surrounding healthy tissues. Dose release monitoring devices using photons and charged particles produced by the beam interaction with the patient body have already been proposed, but no attempt based on the detection of the abundant secondary radiation neutron component has been made yet. The reduced attenuation length of neutrons yields a secondary particle sample that is larger in number when compared to photons and charged particles. Furthermore, neutrons allow for a backtracking of the emission point that is not affected by multiple scattering. Since neutrons can release a significant dose far away from the tumor region, a precise measurement of their flux, production energy and angle distributions is eagerly needed in order to improve the Treatment Planning Systems (TPS) software, so to predict not only the normal tissue toxicity in the target region but also the risk of late complications in the whole body. All the aforementioned issues underline the importance for an experimental effort devoted to the precise characterization of the neutron production gaining experimental access both to the emission point and production energy. The technical challenges posed by a neutron detector aiming for a high detection efficiency and good backtracking precision will be addressed within the MONDO (MOnitor for Neutron Dose in hadrOntherapy) project. The MONDO's main goal is to develop a tracking detector targeting fast and ultrafast secondary neutrons. The tracker is composed by a scintillating fiber matrix (4 × 4 × 8cm3). The full reconstruction of protons, produced in elastic interactions, will be used to measure energy and direction of the impinging neutron. The neutron tracker will measure the neutron production yields, as a function of production angle and energy, using different therapeutic beams at CNAO in Pavia (protons, 12C ions and possibly 4He and 16O ions).

Grating-based holographic diffraction methods for X-rays and neutrons: phase object approximation and dynamical theory

DOE PAGES

Feng, Hao; Ashkar, Rana; Steinke, Nina; ...

2018-02-01

A method dubbed grating-based holography was recently used to determine the structure of colloidal fluids in the rectangular grooves of a diffraction grating from X-ray scattering measurements. Similar grating-based measurements have also been recently made with neutrons using a technique called spin-echo small-angle neutron scattering. The analysis of the X-ray diffraction data was done using an approximation that treats the X-ray phase change caused by the colloidal structure as a small perturbation to the overall phase pattern generated by the grating. In this paper, the adequacy of this weak phase approximation is explored for both X-ray and neutron grating holography.more » Additionally, it is found that there are several approximations hidden within the weak phase approximation that can lead to incorrect conclusions from experiments. In particular, the phase contrast for the empty grating is a critical parameter. Finally, while the approximation is found to be perfectly adequate for X-ray grating holography experiments performed to date, it cannot be applied to similar neutron experiments because the latter technique requires much deeper grating channels.« less

Characterization of Polystyrene Soft Nanoparticles Using Small Angle Neutron Scattering

NASA Astrophysics Data System (ADS)

Martin, Halie; White, Tyler; Saito, Tomonori; Dadmun, Mark

Polymer nanocomposites have become a prominent area of research recently. With a growing variety of nanoparticles available, research probing the influence of particle morphology on the overall nanocomposite properties is also increasing. Nanoparticle dispersion is controlled by both the chemical nature and morphology of the nanoparticle where a crosslinked, fuzzy organic nanoparticle is anticipated to enhance the overall miscibility and create a homogenous dispersion within a like-polymer matrix. A semi-batch microemulsion polymerization forms organic, soft nanoparticles where the precise structure of the nanoparticle is controlled by monomer rate of addition and crosslinking density. We will report small angle neutron scattering results that correlate synthetic conditions to the structural characteristics of soft nanoparticles. This analysis provides characterization of the individual nanoparticle molecular weight, the radius of the crosslinked core, the thickness of the fuzzy interfacial layer, and provides insight into the overall topography of the soft nanoparticle. This research provides a pathway to investigate the effect of nanoscale structural features of the nanoparticle on their individual properties and those of nanocomposites that contain these soft nanoparticles. DOE-BES, Division of Materials Sciences and Engineering.

Internal Structure of 15 nm 3-Helix Micelle Revealed by Small-Angle Neutron Scattering and Coarse-Grained MD Simulation.

PubMed

Ang, JooChuan; Ma, Dan; Lund, Reidar; Keten, Sinan; Xu, Ting

2016-10-10

3-Helix micelles (3HM) formed by self-assembly of peptide-polymer conjugate amphiphiles have shown promise as a nanocarrier platform due to their long-circulation, deep tumor penetration, selective accumulation in tumor, and ability to cross the blood-brain barrier (BBB) for glioblastoma therapy. There is a need to understand the structural contribution to the high in vivo stability and performance of 3HM. Using selective deuteration, the contrast variation technique in small-angle neutron scattering, and coarse-grained molecular dynamics simulation, we determined the spatial distribution of each component within 3HM. Our results show a slightly deformed polyethylene glycol (PEG) conformation within the micelle that is radially offset from its conjugation site toward the exterior of the micelle and a highly solvated shell. Surprisingly, ∼85 v/v % of 3HM is water, unusually higher than any micellar nanocarrier based on our knowledge. The result will provide important structural insights for future studies to uncover the molecular origin of 3HM's in vivo performance, and development of the nanocarriers.

Ultra-small-angle neutron scattering with azimuthal asymmetry

DOE PAGES

Gu, X.; Mildner, D. F. R.

2016-05-16

Small-angle neutron scattering (SANS) measurements from thin sections of rock samples such as shales demand as great a scattering vector range as possible because the pores cover a wide range of sizes. The limitation of the scattering vector range for pinhole SANS requires slit-smeared ultra-SANS (USANS) measurements that need to be converted to pinhole geometry. The desmearing algorithm is only successful for azimuthally symmetric data. Scattering from samples cut parallel to the plane of bedding is symmetric, exhibiting circular contours on a two-dimensional detector. Samples cut perpendicular to the bedding show elliptically dependent contours with the long axis corresponding tomore » the normal to the bedding plane. A method is given for converting such asymmetric data collected on a double-crystal diffractometer for concatenation with the usual pinhole-geometry SANS data. Furthermore, the aspect ratio from the SANS data is used to modify the slit-smeared USANS data to produce quasi-symmetric contours. Rotation of the sample about the incident beam may result in symmetric data but cannot extract the same information as obtained from pinhole geometry.« less

Ultra-small-angle neutron scattering with azimuthal asymmetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gu, X.; Mildner, D. F. R.

Small-angle neutron scattering (SANS) measurements from thin sections of rock samples such as shales demand as great a scattering vector range as possible because the pores cover a wide range of sizes. The limitation of the scattering vector range for pinhole SANS requires slit-smeared ultra-SANS (USANS) measurements that need to be converted to pinhole geometry. The desmearing algorithm is only successful for azimuthally symmetric data. Scattering from samples cut parallel to the plane of bedding is symmetric, exhibiting circular contours on a two-dimensional detector. Samples cut perpendicular to the bedding show elliptically dependent contours with the long axis corresponding tomore » the normal to the bedding plane. A method is given for converting such asymmetric data collected on a double-crystal diffractometer for concatenation with the usual pinhole-geometry SANS data. Furthermore, the aspect ratio from the SANS data is used to modify the slit-smeared USANS data to produce quasi-symmetric contours. Rotation of the sample about the incident beam may result in symmetric data but cannot extract the same information as obtained from pinhole geometry.« less

Fractal Structures on Fe3O4 Ferrofluid: A Small-Angle Neutron Scattering Study

NASA Astrophysics Data System (ADS)

Giri Rachman Putra, Edy; Seong, Baek Seok; Shin, Eunjoo; Ikram, Abarrul; Ani, Sistin Ari; Darminto

2010-10-01

A small-angle neutron scattering (SANS) which is a powerful technique to reveal the large scale structures was applied to investigate the fractal structures of water-based Fe3O4ferrofluid, magnetic fluid. The natural magnetite Fe3O4 from iron sand of several rivers in East Java Province of Indonesia was extracted and purified using magnetic separator. Four different ferrofluid concentrations, i.e. 0.5, 1.0, 2.0 and 3.0 Molar (M) were synthesized through a co-precipitation method and then dispersed in tetramethyl ammonium hydroxide (TMAH) as surfactant. The fractal aggregates in ferrofluid samples were observed from their SANS scattering distributions confirming the correlations to their concentrations. The mass fractal dimension changed from about 3 to 2 as ferrofluid concentration increased showing a deviation slope at intermediate scattering vector q range. The size of primary magnetic particle as a building block was determined by fitting the scattering profiles with a log-normal sphere model calculation. The mean average size of those magnetic particles is about 60 - 100 Å in diameter with a particle size distribution σ = 0.5.

Small Angle X-ray and Neutron Scattering: Powerful Tools for Studying the Structure of Drug-Loaded Liposomes

PubMed Central

Di Cola, Emanuela; Grillo, Isabelle; Ristori, Sandra

2016-01-01

Nanovectors, such as liposomes, micelles and lipid nanoparticles, are recognized as efficient platforms for delivering therapeutic agents, especially those with low solubility in water. Besides being safe and non-toxic, drug carriers with improved performance should meet the requirements of (i) appropriate size and shape and (ii) cargo upload/release with unmodified properties. Structural issues are of primary importance to control the mechanism of action of loaded vectors. Overall properties, such as mean diameter and surface charge, can be obtained using bench instruments (Dynamic Light Scattering and Zeta potential). However, techniques with higher space and time resolution are needed for in-depth structural characterization. Small-angle X-ray (SAXS) and neutron (SANS) scattering techniques provide information at the nanoscale and have therefore been largely used to investigate nanovectors loaded with drugs or other biologically relevant molecules. Here we revise recent applications of these complementary scattering techniques in the field of drug delivery in pharmaceutics and medicine with a focus to liposomal carriers. In particular, we highlight those aspects that can be more commonly accessed by the interested users. PMID:27043614

Small angle neutron scattering study of sodium dodecyl sulfate micellar growth driven by addition of a hydrotropic salt.

PubMed

Hassan, P A; Fritz, Gerhard; Kaler, Eric W

2003-01-01

The structures of aggregates formed in aqueous solutions of an anionic surfactant, sodium dodecyl sulfate (SDS), with the addition of a cationic hydrotropic salt, p-toluidine hydrochloride (PTHC), have been investigated by small angle neutron scattering (SANS). The SANS spectra exhibit a pronounced peak at low salt concentration, indicating the presence of repulsive intermicellar interactions. Model-independent real space information about the structure is obtained from a generalized indirect Fourier transformation (GIFT) technique in combination with a suitable model for the interparticle structure factor. The interparticle interaction is captured using the rescaled mean spherical approximation (RMSA) closure relation and a Yukawa form of the interaction potential. Further quantification of the geometrical parameters of the micelles was achieved by a complete fit of the SANS data using a prolate ellipsoidal form factor and the RMSA structure factor. The present study shows that PTHC induces a decrease in the fractional charge of the micelles due to adsorption at the micellar surface and consequent growth of the SDS micelles from nearly globular to rodlike as the concentration of PTHC increases.

Characterization of Nanoparticles and Colloids in Aquatic Systems 1. Small Angle Neutron Scattering Investigations of Suwannee River Fulvic Acid Aggregates in Aqueous Solutions

NASA Astrophysics Data System (ADS)

Diallo, Mamadou S.; Glinka, Charles J.; Goddard, William A.; Johnson, James H.

2005-10-01

Fulvic acids (FA) and humic acids (HA) constitute 30-50% of dissolved organic matter in natural aquatic systems. In aqueous solutions, a commonly accepted view is that FA and HA exist as soluble macroligands at low concentration and as supramolecular aggregates at higher concentration. The size, shape and structure of these aggregates are still the subject of ongoing debate in the environmental chemistry literature. In this article, we use small angle neutron scattering (SANS) to assess the effects of solute concentration, solution pH and background electrolyte (NaCl) concentration on the structures of Suwannee River FA (SRFA) aggregates in D2O. The qualitative features of the SANS curves and data analysis are not consistent with the view point that SRFA forms micelle-like aggregates as its concentration in aqueous solution increases. We find that SRFA forms fractal aggregates in D20 with size greater than 242 nm. The SRFA aggregates undergo a significant degree of restructuring in compactness as solution pH, solute concentration and NaCl concentration increase.

Joint small-angle X-ray and neutron scattering data analysis of asymmetric lipid vesicles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eicher, Barbara; Heberle, Frederick A.; Marquardt, Drew T.

2017-02-28

Low- and high-resolution models describing the internal transbilayer structure of asymmetric lipid vesicles have been developed. These models can be used for the joint analysis of small-angle neutron and X-ray scattering data. The models describe the underlying scattering length density/electron density profiles either in terms of slabs or through the so-called scattering density profile, previously applied to symmetric lipid vesicles. Both models yield structural details of asymmetric membranes, such as the individual area per lipid, and the hydrocarbon thickness of the inner and outer bilayer leaflets. The scattering density profile model, however, comes at a cost of increased computational effortmore » but results in greater structural resolution, showing a slightly lower packing of lipids in the outer bilayer leaflet of ~120 nm diameter palmitoyloleoyl phosphatidylcholine (POPC) vesicles, compared to the inner leaflet. Here, analysis of asymmetric dipalmitoyl phosphatidylcholine/POPC vesicles did not reveal evidence of transbilayer coupling between the inner and outer leaflets at 323 K, i.e.above the melting transition temperature of the two lipids.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Hao; Ashkar, Rana; Steinke, Nina

A method dubbed grating-based holography was recently used to determine the structure of colloidal fluids in the rectangular grooves of a diffraction grating from X-ray scattering measurements. Similar grating-based measurements have also been recently made with neutrons using a technique called spin-echo small-angle neutron scattering. The analysis of the X-ray diffraction data was done using an approximation that treats the X-ray phase change caused by the colloidal structure as a small perturbation to the overall phase pattern generated by the grating. In this paper, the adequacy of this weak phase approximation is explored for both X-ray and neutron grating holography.more » Additionally, it is found that there are several approximations hidden within the weak phase approximation that can lead to incorrect conclusions from experiments. In particular, the phase contrast for the empty grating is a critical parameter. Finally, while the approximation is found to be perfectly adequate for X-ray grating holography experiments performed to date, it cannot be applied to similar neutron experiments because the latter technique requires much deeper grating channels.« less

Periodic magnetic field as a polarized and focusing thermal neutron spectrometer and monochromator.

PubMed

Cremer, J T; Williams, D L; Fuller, M J; Gary, C K; Piestrup, M A; Pantell, R H; Feinstein, J; Flocchini, R G; Boussoufi, M; Egbert, H P; Kloh, M D; Walker, R B

2010-01-01

A novel periodic magnetic field (PMF) optic is shown to act as a prism, lens, and polarizer for neutrons and particles with a magnetic dipole moment. The PMF has a two-dimensional field in the axial direction of neutron propagation. The PMF alternating magnetic field polarity provides strong gradients that cause separation of neutrons by wavelength axially and by spin state transversely. The spin-up neutrons exit the PMF with their magnetic spins aligned parallel to the PMF magnetic field, and are deflected upward and line focus at a fixed vertical height, proportional to the PMF period, at a downstream focal distance that increases with neutron energy. The PMF has no attenuation by absorption or scatter, as with material prisms or crystal monochromators. Embodiments of the PMF include neutron spectrometer or monochromator, and applications include neutron small angle scattering, crystallography, residual stress analysis, cross section measurements, and reflectometry. Presented are theory, experimental results, computer simulation, applications of the PMF, and comparison of its performance to Stern-Gerlach gradient devices and compound material and magnetic refractive prisms.

Periodic magnetic field as a polarized and focusing thermal neutron spectrometer and monochromator

PubMed Central

Cremer, J. T.; Williams, D. L.; Fuller, M. J.; Gary, C. K.; Piestrup, M. A.; Pantell, R. H.; Feinstein, J.; Flocchini, R. G.; Boussoufi, M.; Egbert, H. P.; Kloh, M. D.; Walker, R. B.

2010-01-01

A novel periodic magnetic field (PMF) optic is shown to act as a prism, lens, and polarizer for neutrons and particles with a magnetic dipole moment. The PMF has a two-dimensional field in the axial direction of neutron propagation. The PMF alternating magnetic field polarity provides strong gradients that cause separation of neutrons by wavelength axially and by spin state transversely. The spin-up neutrons exit the PMF with their magnetic spins aligned parallel to the PMF magnetic field, and are deflected upward and line focus at a fixed vertical height, proportional to the PMF period, at a downstream focal distance that increases with neutron energy. The PMF has no attenuation by absorption or scatter, as with material prisms or crystal monochromators. Embodiments of the PMF include neutron spectrometer or monochromator, and applications include neutron small angle scattering, crystallography, residual stress analysis, cross section measurements, and reflectometry. Presented are theory, experimental results, computer simulation, applications of the PMF, and comparison of its performance to Stern–Gerlach gradient devices and compound material and magnetic refractive prisms. PMID:20113108

Investigations on neutron irradiated 3D carbon fibre reinforced carbon composite material

NASA Astrophysics Data System (ADS)

Venugopalan, Ramani; Alur, V. D.; Patra, A. K.; Acharya, R.; Srivastava, D.

2018-04-01

As against conventional graphite materials carbon-carbon (C/C) composite materials are now being contemplated as the promising candidate materials for the high temperature and fusion reactor owing to their high thermal conductivity and high thermal resistance, better mechanical/thermal properties and irradiation stability. The current need is for focused research on novel carbon materials for future new generation nuclear reactors. The advantage of carbon-carbon composite is that the microstructure and the properties can be tailor made. The present study encompasses the irradiation of 3D carbon composite prepared by reinforcement using PAN carbon fibers for nuclear application. The carbon fiber reinforced composite was subjected to neutron irradiation in the research reactor DHRUVA. The irradiated samples were characterized by Differential Scanning Calorimetry (DSC), small angle neutron scattering (SANS), XRD and Raman spectroscopy. The DSC scans were taken in argon atmosphere under a linear heating program. The scanning was carried out at temperature range from 30 °C to 700 °C at different heating rates in argon atmosphere along with reference as unirradiated carbon composite. The Wigner energy spectrum of irradiated composite showed two peaks corresponding to 200 °C and 600 °C. The stored energy data for the samples were in the range 110-170 J/g for temperature ranging from 30 °C to 700 °C. The Wigner energy spectrum of irradiated carbon composite did not indicate spontaneous temperature rise during thermal annealing. Small angle neutron scattering (SANS) experiments have been carried out to investigate neutron irradiation induced changes in porosity of the composite samples. SANS data were recorded in the scattering wave vector range of 0.17 nm-1 to 3.5 nm-1. Comparison of SANS profiles of irradiated and unirradiated samples indicates significant change in pore morphology. Pore size distributions of the samples follow power law size distribution with different exponent. Narrowing of SANS profile of the irradiated sample indicates creation of significant number of larger pores due to neutron irradiation.

Recent applications of small-angle neutron scattering in strongly interacting soft condensed matter

NASA Astrophysics Data System (ADS)

Wignall, G. D.; Melnichenko, Y. B.

2005-08-01

Before the application of small-angle neutron scattering (SANS) to the study of polymer structure, chain conformation studies were limited to light and small-angle x-ray scattering techniques, usually conducted in dilute solution owing to the difficulties of separating the inter- and intrachain contributions to the structure. The unique role of neutron scattering in soft condensed matter arises from the difference in the coherent scattering length between deuterium (bD = 0.67 × 10-12 cm) and hydrogen (bH = -0.37 × 10-12 cm), which results in a marked difference in scattering power (contrast) between molecules synthesized from normal (hydrogeneous) and deuterated monomer units. Thus, deuterium labelling techniques may be used to 'stain' molecules and make them 'visible' in the condensed state and other crowded environments, such as concentrated solutions of overlapping chains. For over two decades, SANS has proved to be a powerful tool for studies of structure-property relationships in polymeric systems and has made it possible to extract unique information about their size, shape, conformational changes and molecular associations. These applications are now so numerous that an exhaustive review of the field is no longer practical, so the authors propose to focus on the use of SANS for studies of strongly interacting soft matter systems. This paper will therefore discuss basic theory and practical aspects of the technique and will attempt to explain the physics of scattering with the minimum of unnecessary detail and mathematical rigour. Examples will be given to demonstrate the power of SANS and to show how it has helped to unveil universal aspects of the behaviour of macromolecules in such apparently diverse systems as polymer solutions, blends, polyelectrolytes and supercritical mixtures. The aim of the authors is to aid potential users who have a general scientific background, but no specialist knowledge of scattering, to understand the potential of the technique and, if they so choose, to apply it to provide new information in areas of their own particular research interests.

Model-based Approaches for the Determination of Lipid Bilayer Structure from Small-Angle Neutron and X-ray Scattering Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heberle, Frederick A; Pan, Jianjun; Standaert, Robert F

2012-01-01

Some of our recent work has resulted in the detailed structures of fully hydrated, fluid phase phosphatidylcholine (PC) and phosphatidylglycerol (PG) bilayers. These structures were obtained from the joint refinement of small-angle neutron and X-ray data using the scattering density profile (SDP) models developed by Ku erka et al. (Ku erka et al. 2012; Ku erka et al. 2008). In this review, we first discuss models for the standalone analysis of neutron or X-ray scattering data from bilayers, and assess the strengths and weaknesses inherent in these models. In particular, it is recognized that standalone data do not contain enoughmore » information to fully resolve the structure of inherently disordered fluid bilayers, and therefore may not provide a robust determination of bilayer structural parameters, including the much sought after area per lipid. We then discuss the development of matter density-based models (including the SDP model) that allow for the joint refinement of different contrast neutron and X-ray data sets, as well as the implementation of local volume conservation in the unit cell (i.e., ideal packing). Such models provide natural definitions of bilayer thicknesses (most importantly the hydrophobic and Luzzati thicknesses) in terms of Gibbs dividing surfaces, and thus allow for the robust determination of lipid areas through equivalent slab relationships between bilayer thickness and lipid volume. In the final section of this review, we discuss some of the significant findings/features pertaining to structures of PC and PG bilayers as determined from SDP model analyses.« less

Application of X-ray and neutron small angle scattering techniques to study the hierarchical structure of plant cell walls: a review.

PubMed

Martínez-Sanz, Marta; Gidley, Michael J; Gilbert, Elliot P

2015-07-10

Plant cell walls present an extremely complex structure of hierarchically assembled cellulose microfibrils embedded in a multi-component matrix. The biosynthesis process determines the mechanism of cellulose crystallisation and assembly, as well as the interaction of cellulose with other cell wall components. Thus, a knowledge of cellulose microfibril and bundle architecture, and the structural role of matrix components, is crucial for understanding cell wall functional and technological roles. Small angle scattering techniques, combined with complementary methods, provide an efficient approach to characterise plant cell walls, covering a broad and relevant size range while minimising experimental artefacts derived from sample treatment. Given the system complexity, approaches such as component extraction and the use of plant cell wall analogues are typically employed to enable the interpretation of experimental results. This review summarises the current research status on the characterisation of the hierarchical structure of plant cell walls using small angle scattering techniques. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

Spontaneous imbibition of water and determination of effective contact angles in the Eagle Ford Shale Formation using neutron imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

DiStefano, Victoria H.; Cheshire, Michael C.; McFarlane, Joanna

Understanding of fundamental processes and prediction of optimal parameters during the horizontal drilling and hydraulic fracturing process results in economically effective improvement of oil and natural gas extraction. Although, the modern analytical and computational models can capture fracture growth, there is a lack of experimental data on spontaneous imbibition and wettability in oil and gas reservoirs for the validation of further model development. In this work, we used neutron imaging to measure the spontaneous imbibition of water into fractures of Eagle Ford Shale with known geometries and fracture orientations. An analytical solution for a set of nonlinear second-order differential equationsmore » was applied to the measured imbibition data to determine effective contact angles. The analytical solution fit the measured imbibition data reasonably well and determined effective contact angles were slightly higher than static contact angles due to effects of in-situ changes in velocity, surface roughness, and heterogeneity of mineral surfaces on the fracture surface. Additionally, small fracture widths may have retarded imbibition and affected model fits, which suggests that average fracture widths are not satisfactory for modeling imbibition in natural systems.« less

Studying Soft-matter and Biological Systems over a Wide Length-scale from Nanometer and Micrometer Sizes at the Small-angle Neutron Diffractometer KWS-2

PubMed Central

Radulescu, Aurel; Szekely, Noemi Kinga; Appavou, Marie-Sousai; Pipich, Vitaliy; Kohnke, Thomas; Ossovyi, Vladimir; Staringer, Simon; Schneider, Gerald J.; Amann, Matthias; Zhang-Haagen, Bo; Brandl, Georg; Drochner, Matthias; Engels, Ralf; Hanslik, Romuald; Kemmerling, Günter

2016-01-01

The KWS-2 SANS diffractometer is dedicated to the investigation of soft matter and biophysical systems covering a wide length scale, from nm to µm. The instrument is optimized for the exploration of the wide momentum transfer Q range between 1x10-4 and 0.5 Å-1 by combining classical pinhole, focusing (with lenses), and time-of-flight (with chopper) methods, while simultaneously providing high-neutron intensities with an adjustable resolution. Because of its ability to adjust the intensity and the resolution within wide limits during the experiment, combined with the possibility to equip specific sample environments and ancillary devices, the KWS-2 shows a high versatility in addressing the broad range of structural and morphological studies in the field. Equilibrium structures can be studied in static measurements, while dynamic and kinetic processes can be investigated over time scales between minutes to tens of milliseconds with time-resolved approaches. Typical systems that are investigated with the KWS-2 cover the range from complex, hierarchical systems that exhibit multiple structural levels (e.g., gels, networks, or macro-aggregates) to small and poorly-scattering systems (e.g., single polymers or proteins in solution). The recent upgrade of the detection system, which enables the detection of count rates in the MHz range, opens new opportunities to study even very small biological morphologies in buffer solution with weak scattering signals close to the buffer scattering level at high Q. In this paper, we provide a protocol to investigate samples with characteristic size levels spanning a wide length scale and exhibiting ordering in the mesoscale structure using KWS-2. We present in detail how to use the multiple working modes that are offered by the instrument and the level of performance that is achieved. PMID:28060296

High intensity multi beam design of SANS instrument for Dhruva reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abbas, Sohrab, E-mail: abbas@barc.gov.in; Aswal, V. K.; Désert, S.

A new and versatile design of Small Angle Neutron Scattering (SANS) instrument based on utilization of multi-beam is presented. The multi-pinholes and multi-slits as SANS collimator for medium flux Dhruva rearctor have been proposed and their designs have been validated using McStas simulations. Various instrument configurations to achieve different minimum wave vector transfers in scattering experiments are envisioned. These options enable smooth access to minimum wave vector transfers as low as ~ 6×10{sup −4} Å{sup −1} with a significant improvement in neutron intensity, allowing faster measurements. Such angularly well defined and intense neutron beam will allow faster SANS studies ofmore » agglomerates larger than few tens of nm.« less

Structural formation of huntingtin-like aggregates probed by small-angle neutron scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stanley, Christopher B; Perevozchikova, Tatiana; Berthelier-Jung, Valerie M

2011-01-01

In several neurodegenerative disorders, including Huntington s disease (HD), aspects concerning the earliest of protein structures that form along the aggregation pathway have increasingly gained attention since these particular species are likely to be neurotoxic. We used time-resolved small-angle neutron scattering (SANS) to probe in solution these transient structures formed by peptides having the N-terminal sequence context of mutant huntingtin (Htt) exon 1. We obtained snapshots of the formed aggregates as the kinetic reaction ensued to yield quantitative information on their size and mass. At the early stage, small precursor species with an initial radius of gyration (Rg) of 16.1more » 5.9 and average mass of a dimer to trimer were monitored. Structural growth was treated as two modes with a transition from three-dimensional early aggregate formation to two-dimensional fibril growth and association. Our SANS results on the internal structure of the mature fibrils demonstrate loose packing with about 1 peptide per 4.75 -sheet repeat distance, which is shown to be quantitatively consistent with a -helix model. This research provides new insights into the structures forming along the pathway of Htt exon 1 aggregation and should assist in determining the role that precursors play in neuronal toxicity.« less

Combination of acoustic levitation with small angle scattering techniques and synchrotron radiation circular dichroism. Application to the study of protein solutions.

PubMed

Cristiglio, Viviana; Grillo, Isabelle; Fomina, Margarita; Wien, Frank; Shalaev, Evgenyi; Novikov, Alexey; Brassamin, Séverine; Réfrégiers, Matthieu; Pérez, Javier; Hennet, Louis

2017-01-01

The acoustic levitation technique is a useful sample handling method for small solid and liquids samples, suspended in air by means of an ultrasonic field. This method was previously used at synchrotron sources for studying pharmaceutical liquids and protein solutions using x-ray diffraction and small angle x-ray scattering (SAXS). In this work we combined for the first time this containerless method with small angle neutron scattering (SANS) and synchrotron radiation circular dichroism (SRCD) to study the structural behavior of proteins in solutions during the water evaporation. SANS results are also compared with SAXS experiments. The aggregation behavior of 45μl droplets of lysozyme protein diluted in water was followed during the continuous increase of the sample concentration by evaporating the solvent. The evaporation kinetics was followed at different drying stage by SANS and SAXS with a good data quality. In a prospective work using SRCD, we also studied the evolution of the secondary structure of the myoglobin protein in water solution in the same evaporation conditions. Acoustic levitation was applied for the first time with SANS and the high performances of the used neutron instruments made it possible to monitor fast container-less reactions in situ. A preliminary work using SRCD shows the potentiality of its combination with acoustic levitation for studying the evolution of the protein structure with time. This multi-techniques approach could give novel insights into crystallization and self-assembly phenomena of biological compound with promising potential applications in pharmaceutical, food and cosmetics industry. This article is part of a Special Issue entitled "Science for Life" Guest Editor: Dr. Austen Angell, Dr. Salvatore Magazù and Dr. Federica Migliardo. Copyright © 2016 Elsevier B.V. All rights reserved.

Neutron scattering studies of crude oil viscosity reduction with electric field

NASA Astrophysics Data System (ADS)

Du, Enpeng

Small-angle neutron scattering (SANS) is a very powerful laboratory technique for micro structure research which is similar to the small angle X-ray scattering (SAXS) and light scattering for microstructure investigations in various materials. In small-angle neutron scattering (SANS) technique, the neutrons are elastically scattered by changes of refractive index on a nanometer scale inside the sample through the interaction with the nuclei of the atoms present in the sample. Because the nuclei of all atoms are compact and of comparable size, neutrons are capable of interacting strongly with all atoms. This is in contrast to X-ray techniques where the X-rays interact weakly with hydrogen, the most abundant element in most samples. The SANS refractive index is directly related to the scattering length density and is a measure of the strength of the interaction of a neutron wave with a given nucleus. It can probe inhomogeneities in the nanometer scale from 1nm to 1000nm. Since the SANS technique probes the length scale in a very useful range, this technique provides valuable information over a wide variety of scientific and technological applications, including chemical aggregation, defects in materials, surfactants, colloids, ferromagnetic correlations in magnetism, alloy segregation, polymers, proteins, biological membranes, viruses, ribosome and macromolecules. Quoting the Nobel committee, when awarding the prize to C. Shull and B. Brockhouse in 1994: "Neutrons tell you where the atoms are and what the atoms do". At NIST, there is a single beam of neutrons generated from either reactor or pulsed neutron source and selected by velocity selector. The beam passes through a neutron guide then scattered by the sample. After the sample chamber, there are 2D gas detectors to collect the elastic scattering information. SANS usually uses collimation of the neutron beam to determine the scattering angle of a neutron, which results in an even lower signal-to-noise ratio for data that contains information on the properties of a sample. We can analyze the data acquisition from the detectors and get the information on size, shape, etc. This is why we choose SANS as our research tool. The world's top energy problems are security concerns, climate concerns and environmental concerns. So far, oil (37%) is still the No.1 fuel in world energy consumption (Oil 37%, Coal 25%, Bio-fuels 0.2%, Gas 23%, Nuclear 6%, Biomass 4%, Hydro 3%, Solar heat 0.5%, Wind 0.3%, Geothermal 0.2% and Solar photovoltaic 0.04%). Even more and more alternative energy: bio-fuels, nuclear and solar energy will be used in the future, but nuclear energy has a major safety issue after the Japanese Fukushima I nuclear accidents, and other energies contribute only a small percent. Thus, it is very important to improve the efficiency and reduce the population of petroleum products. There is probably one thing that we can all agree on: the world's energy reserves are not unlimited. Even though it is limited, only 30% of the oil reserves is conventional oil, so in order to produce, transport, and refine of heavy crude oil without wasting huge amounts of energy, we need to reduce the viscosity without using high temperature stream heating or diluent; As more and more off-shore oil is exploited at that we need reduce the viscosity without increasing temperature. The whole petroleum consumed in U.S. in 2009 was 18.7 million barrels per day and 35% of all the energy we consumed. Diesel is one of the very important fossil fuel which is about 20% of petroleum consumed. Most of the world's oils are non-conventional, 15 % of heavy oil, 25 % of extra heavy oil, 30 % of the oil sands and bitumen, and the conventional oil reserves is only 30%. The oil sand is closely related to the heavy crude oil, the main difference being that oil sands generally do not flow at all. For efficient energy production and conservation, how to lower the liquated fuel and crude oil viscosity is a very important topic. Dr. Tao with his group at Temple University, using his electro or magnetic rheological viscosity theory has developed a new technology, which utilizes electric or magnetic fields to change the rheology of complex fluids to reduce the viscosity, while keeping the temperature unchanged. After we successfully reduced the viscosity of crude oil with field and investigated the microstructure changing in various crude oil samples with SANS, we have continued to reduce the viscosity of heavy crude oil, bunker diesel, ultra low sulfur diesel, bio-diesel and crude oil and ultra low temperature with electric field treatment. Our research group developed the viscosity electrorheology theory and investigated flow rate with laboratory and field pipeline. But we never visualize this aggregation. The small angle neutron scattering experiment has confirmed the theoretical prediction that a strong electric field induces the suspended nano-particles inside crude oil to aggregate into short chains along the field direction. This aggregation breaks the symmetry, making the viscosity anisotropic: along the field direction, the viscosity is significantly reduced. The experiment enables us to determine the induced chain size and shape, verifies that the electric field works for all kinds of crude oils, paraffin-based, asphalt-based, and mix-based. The basic physics of such field induced viscosity reduction is applicable to all kinds of suspensions.

Research on a Neutron Detector With a Boron-Lined Honeycomb Neutron Converter

NASA Astrophysics Data System (ADS)

Fang, Zhujun; Yang, Yigang; Li, Yulan; Zhang, Zhi; Wang, Xuewu

2017-04-01

A new design of the boron-lined gaseous neutron detector composed of a boron-lined honeycomb neutron converter and an electron multiplier is proposed in this paper. The motivation for this research was to decrease the manufacturing difficulty and improve the robustness of the boron-lined gaseous neutron detector. The numerous anode wires in the traditional designs were removed, and the gas electron multiplier (GEM) was used as the electron multiplier. To drive the ionized electrons produced inside the honeycomb structure out to the incident surface of the GEM, a drift electric field was applied inside the holes of the honeycomb structure. The design principles of this detector were discussed. Geant4, Maxwell11, and Garfield9 were used to estimate the neutron absorption efficiency and the electron migration process. A prototype detector was constructed and experimentally evaluated. Both the simulation and experimental results indicate that this detector has the potential to be used in the applications of small angle neutron scattering for scientific research, and to replace the currently used 3He detectors, which have the trouble of very limited supply of 3He gas.

Random coil negative control reproduces the discrepancy between scattering and FRET measurements of denatured protein dimensions

PubMed Central

Watkins, Herschel M.; Simon, Anna J.; Sosnick, Tobin R.; Lipman, Everett A.; Hjelm, Rex P.; Plaxco, Kevin W.

2015-01-01

Small-angle scattering studies generally indicate that the dimensions of unfolded single-domain proteins are independent (to within experimental uncertainty of a few percent) of denaturant concentration. In contrast, single-molecule FRET (smFRET) studies invariably suggest that protein unfolded states contract significantly as the denaturant concentration falls from high (∼6 M) to low (∼1 M). Here, we explore this discrepancy by using PEG to perform a hitherto absent negative control. This uncharged, highly hydrophilic polymer has been shown by multiple independent techniques to behave as a random coil in water, suggesting that it is unlikely to expand further on the addition of denaturant. Consistent with this observation, small-angle neutron scattering indicates that the dimensions of PEG are not significantly altered by the presence of either guanidine hydrochloride or urea. smFRET measurements on a PEG construct modified with the most commonly used FRET dye pair, however, produce denaturant-dependent changes in transfer efficiency similar to those seen for a number of unfolded proteins. Given the vastly different chemistries of PEG and unfolded proteins and the significant evidence that dye-free PEG is well-described as a denaturant-independent random coil, this similarity raises questions regarding the interpretation of smFRET data in terms of the hydrogen bond- or hydrophobically driven contraction of the unfolded state at low denaturant. PMID:25964362

Direct Measure of the Dense Methane Phase in Gas Shale Organic Porosity by Neutron Scattering

DOE PAGES

Eberle, Aaron P. R.; King, Hubert E.; Ravikovitch, Peter I.; ...

2016-08-30

Here, we report the first direct measurements of methane density in shale gas using small-angle neutron scattering. At a constant pressure, the density of methane in the inorganic pores is similar to the gas bulk density of the system conditions. Conversely, the methane density is 2.1 ± 0.2 times greater in the organic mesopores. Furthermore, classical density functional theory calculations show that this excess density in the organic pores persists to elevated temperatures, typical of shale gas reservoir conditions, providing new insight into the hydrocarbon storage mechanisms within these reservoirs.

Scaling beta-delayed neutron measurements to large detector areas

NASA Astrophysics Data System (ADS)

Sutanto, F.; Nattress, J.; Jovanovic, I.

2017-08-01

We explore the performance of a cargo screening system that consists of two large-sized composite scintillation detectors and a high-energy neutron interrogation source by modeling and simulation. The goal of the system is to measure β-delayed neutron emission from an illicit special nuclear material by use of active interrogation. This task is challenging because the β-delayed neutron yield is small in comparison with the yield of the prompt fission secondary products, β-delayed neutrons are emitted with relatively low energies, and high neutron and gamma backgrounds are typically present. Detectors used to measure delayed neutron emission must exhibit high intrinsic efficiency and cover a large solid angle, which also makes them sensitive to background neutron radiation. We present a case study where we attempt to detect the presence of 5 kg-scale quantities of 235U in a standard air-filled cargo container using 14 MeV neutrons as a probe. We find that by using a total measurement time of ˜11.6 s and a dose equivalent of ˜1.7 mrem, the presence of 235U can be detected with false positive and false negative probabilities that are both no larger than 0.1%.

Evidence for a jacketed nematic polymer

NASA Astrophysics Data System (ADS)

Hardouin, F.; Mery, S.; Achard, M. F.; Noirez, L.; Keller, P.

1991-05-01

The evidence for a “jacketed” structure at the scale of the chain dimensions in the nematic phase of a “side-on fixed” liquid crystal polysiloxane is reported by using small angle neutron scattering. We relate this anisotropy of chain conformation to the first measurements of the rotational viscosity coefficient in this new type of liquid crystal side-chain polymer. Par des mesures de diffusion des neutrons aux petits angles nous montrons l'existence, pour un polysiloxane “ en haltère ”, d'une structure “ chemisée ” à l'échelle de l'organisation global d'une chaîne en phase nématique. On constate que cette anisotropie de forme du polymère a des conséquences sur l'évolution du coefficient de viscosité de torsion mesuré pour la première fois dans ce nouveau type de polymère à chaînes latérales.

On the adsorption properties of magnetic fluids: Impact of bulk structure

NASA Astrophysics Data System (ADS)

Kubovcikova, Martina; Gapon, Igor V.; Zavisova, Vlasta; Koneracka, Martina; Petrenko, Viktor I.; Soltwedel, Olaf; Almasy, László; Avdeev, Mikhail V.; Kopcansky, Peter

2017-04-01

Adsorption of nanoparticles from magnetic fluids (MFs) on solid surface (crystalline silicon) was studied by neutron reflectometry (NR) and related to the bulk structural organization of MFs concluded from small-angle neutron scattering (SANS). The initial aqueous MF with nanomagnetite (co-precipitation reaction) stabilized by sodium oleate and MF modified by a biocompatible polymer, poly(ethylene glycol) (PEG), were considered. Regarding the bulk structure it was confirmed in the SANS experiment that comparatively small and compact (size 30 nm) aggregates of nanoparticle in the initial sample transfer to large and developed (size>130 nm, fractal dimension 2.7) associates in the PEG modified MF. This reorganization in the aggregates correlates with the changes in the neutron reflectivity that showed that a single adsorption layer of individual nanoparticles on the oxidized silicon surface for the initial MF disappears after the PEG modification. It is concluded that all particles in the modified fluid are in the aggregates that are not adsorbed by silicon.

Small angle scattering from protein/sugar conjugates

NASA Astrophysics Data System (ADS)

Jackson, Andrew; White, John

2006-11-01

The Maillard reaction between free amine groups on proteins and sugars is well known. We have examined the effect of the reaction of the casein group of milk proteins with sugars on their nanoscale structure and aggregation. The small angle neutron scattering from beta casein and sodium caseinate and their sugar conjugates have been studied as a function of solution concentration. At high conjugate concentration (greater than ca. 5 mg/ml) the addition of sugar reduces supra-micellar aggregation of the protein whilst at lower concentration, where the protein is expected to be deaggregated already, little effect is seen. Guinier analysis of the scattering data show a radius of gyration of around 75 A˚ for beta casein in solution and around 80 A˚ for the sucrose conjugate.

Neutron measurements in near-Earth orbit with COMPTEL

NASA Technical Reports Server (NTRS)

Morris, D. J.; Aarts, H.; Bennett, K.; Lockwood, J. A.; Mcconnell, M. L.; Ryan, J. M.; Schoenfelder, V.; Steinle, H.; Peng, X.

1995-01-01

The fast neutron flux in near-Earth orbit has been measured with the COMPTEL instrument on the Compton Gamma Ray Observatory (CGRO). For this measurement one of COMPTEL's seven liquid scintillator modules was used as an uncollimated neutron detector with threshold of 12.8 MeV. The measurements cover a range of 4.8 to 15.5 GV in vertical cutoff rigidity and 3 deg to 177 deg in spacecraft geocenter zenith angle. One of the measurements occurred near the minimum of the deepest Forbush decrease ever observed by ground-level neutron monitors. After correction for solar modulation, the total flux is well fitted by separable functions in rigidity and zenith angle. With the spacecraft pointed near the nadir the flux is consistent with balloon measurements of the atmospheric neutron albedo. The flux varies by about a factor of 4 between the extremes of rigidity and a factor of 2 between the extremes of zenith angle. The effect of the spacecraft mass in shielding the detector from the atmospheric neutron albedo is much more important than its role as a source of additional secondary neutrons. The neutron spectral hardness varies little with rigidity or zenith angle and lies in the range spanned by earlier atmospheric neutron albedo measurements.

A Hierarchical Algorithm for Fast Debye Summation with Applications to Small Angle Scattering

PubMed Central

Gumerov, Nail A.; Berlin, Konstantin; Fushman, David; Duraiswami, Ramani

2012-01-01

Debye summation, which involves the summation of sinc functions of distances between all pair of atoms in three dimensional space, arises in computations performed in crystallography, small/wide angle X-ray scattering (SAXS/WAXS) and small angle neutron scattering (SANS). Direct evaluation of Debye summation has quadratic complexity, which results in computational bottleneck when determining crystal properties, or running structure refinement protocols that involve SAXS or SANS, even for moderately sized molecules. We present a fast approximation algorithm that efficiently computes the summation to any prescribed accuracy ε in linear time. The algorithm is similar to the fast multipole method (FMM), and is based on a hierarchical spatial decomposition of the molecule coupled with local harmonic expansions and translation of these expansions. An even more efficient implementation is possible when the scattering profile is all that is required, as in small angle scattering reconstruction (SAS) of macromolecules. We examine the relationship of the proposed algorithm to existing approximate methods for profile computations, and show that these methods may result in inaccurate profile computations, unless an error bound derived in this paper is used. Our theoretical and computational results show orders of magnitude improvement in computation complexity over existing methods, while maintaining prescribed accuracy. PMID:22707386

Dielectric RheoSANS - Simultaneous Interrogation of Impedance, Rheology and Small Angle Neutron Scattering of Complex Fluids.

PubMed

Richards, Jeffrey J; Gagnon, Cedric V L; Krzywon, Jeffery R; Wagner, Norman J; Butler, Paul D

2017-04-10

A procedure for the operation of a new dielectric RheoSANS instrument capable of simultaneous interrogation of the electrical, mechanical and microstructural properties of complex fluids is presented. The instrument consists of a Couette geometry contained within a modified forced convection oven mounted on a commercial rheometer. This instrument is available for use on the small angle neutron scattering (SANS) beamlines at the National Institute of Standards and Technology (NIST) Center for Neutron Research (NCNR). The Couette geometry is machined to be transparent to neutrons and provides for measurement of the electrical properties and microstructural properties of a sample confined between titanium cylinders while the sample undergoes arbitrary deformation. Synchronization of these measurements is enabled through the use of a customizable program that monitors and controls the execution of predetermined experimental protocols. Described here is a protocol to perform a flow sweep experiment where the shear rate is logarithmically stepped from a maximum value to a minimum value holding at each step for a specified period of time while frequency dependent dielectric measurements are made. Representative results are shown from a sample consisting of a gel composed of carbon black aggregates dispersed in propylene carbonate. As the gel undergoes steady shear, the carbon black network is mechanically deformed, which causes an initial decrease in conductivity associated with the breaking of bonds comprising the carbon black network. However, at higher shear rates, the conductivity recovers associated with the onset of shear thickening. Overall, these results demonstrate the utility of the simultaneous measurement of the rheo-electro-microstructural properties of these suspensions using the dielectric RheoSANS geometry.

THE POLARIZATION OF NEUTRONS FROM THE STRIPPING OF DEUTERONS ON C$sup 1$$sup 2$

DOE Office of Scientific and Technical Information (OSTI.GOV)

Budzanowski, A.; Grotowski, K.; Niewodniczanski, H.

1961-01-01

The neutron polarization in the reaction C/sup 12/(d,n)N/sup 13/ at 12.9 Mev is measured as a function of the neutron emission angle. In addition, the neutron energy spectrum is measured at a fixed angle, in order to find the relative numbers of neutrons associated with various energy levels of N/sup 13/. The measured data are used to induce the properties of the N/sup 13/ energy levels studied. (T.F.H.)

Small Angle Neutron Scattering (SANS) Characterization of Electrically Conducting Polyaniline Nanofiber/Polyimide Nanocomposites

DTIC Science & Technology

2011-10-25

range, neither the D-B nor the IPL model could be used to characterize the size and shape of all PANI-0.5-CSA (polyaniline camphor sulfonic acid doped...be used to characterize the size and shape of all PANI-0.5-CSA (polyaniline camphor sulfonic acid doped polymer)/polyimide blend systems. At 1 and 2

A Small Angle Polarized Neutron Scattering Investigation of Magnetic Correlations in Nanocrystalline Fe89Zr7B3Cu1

DTIC Science & Technology

2003-01-01

INFM - S3, Dipartimento di Fisica, UniversitA degli Studi di Modena e Reggio Emilia , Italy. ’School of Physics, University of New South Wales, Sydney...the PNFM Research Center - S3 (Nanostructures and Biosysters at Surfaces), University of Modena and Reggio Emilia , Italy and the Australian Research

Estimation and modeling of coal pore accessibility using small angle neutron scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Rui; Liu, Shimin; Bahadur, Jitendra

Gas diffusion in coal is controlled by nano-structure of the pores. The interconnectivity of pores not only determines the dynamics of gas transport in the coal matrix but also influences the mechanical strength. In this study, small angle neutron scattering (SANS) was employed to quantify pore accessibility for two coal samples, one of sub-bituminous rank and the other of anthracite rank. Moreover, a theoretical pore accessibility model was proposed based on scattering intensities under both vacuum and zero average contrast (ZAC) conditions. Our results show that scattering intensity decreases with increasing gas pressure using deuterated methane (CD 4) at lowmore » Q values for both coals. Pores smaller than 40 nm in radius are less accessible for anthracite than sub-bituminous coal. On the contrary, when the pore radius is larger than 40 nm, the pore accessibility of anthracite becomes larger than that of sub-bituminous coal. Only 20% of pores are accessible to CD 4 for anthracite and 37% for sub-bituminous coal, where the pore radius is 16 nm. For these two coals, pore accessibility and pore radius follows a power-law relationship.« less

Estimation and modeling of coal pore accessibility using small angle neutron scattering

DOE PAGES

Zhang, Rui; Liu, Shimin; Bahadur, Jitendra; ...

2015-09-04

Gas diffusion in coal is controlled by nano-structure of the pores. The interconnectivity of pores not only determines the dynamics of gas transport in the coal matrix but also influences the mechanical strength. In this study, small angle neutron scattering (SANS) was employed to quantify pore accessibility for two coal samples, one of sub-bituminous rank and the other of anthracite rank. Moreover, a theoretical pore accessibility model was proposed based on scattering intensities under both vacuum and zero average contrast (ZAC) conditions. Our results show that scattering intensity decreases with increasing gas pressure using deuterated methane (CD 4) at lowmore » Q values for both coals. Pores smaller than 40 nm in radius are less accessible for anthracite than sub-bituminous coal. On the contrary, when the pore radius is larger than 40 nm, the pore accessibility of anthracite becomes larger than that of sub-bituminous coal. Only 20% of pores are accessible to CD 4 for anthracite and 37% for sub-bituminous coal, where the pore radius is 16 nm. For these two coals, pore accessibility and pore radius follows a power-law relationship.« less

Magnetic small-angle neutron scattering on bulk metallic glasses: A feasibility study for imaging displacement fields

NASA Astrophysics Data System (ADS)

Mettus, Denis; Deckarm, Michael; Leibner, Andreas; Birringer, Rainer; Stolpe, Moritz; Busch, Ralf; Honecker, Dirk; Kohlbrecher, Joachim; Hautle, Patrick; Niketic, Nemanja; Fernández, Jesús Rodríguez; Barquín, Luis Fernández; Michels, Andreas

2017-12-01

Magnetic-field-dependent small-angle neutron scattering (SANS) has been utilized to study the magnetic microstructure of bulk metallic glasses (BMGs). In particular, the magnetic scattering from soft magnetic Fe70Mo5Ni5P12.5B2.5C5 and hard magnetic (Nd60Fe30Al10) 92Ni8 alloys in the as-prepared, aged, and mechanically deformed state is compared. While the soft magnetic BMGs exhibit a large field-dependent SANS response with perturbations originating predominantly from spatially varying magnetic anisotropy fields, the SANS cross sections of the hard magnetic BMGs are only weakly dependent on the field, and their angular anisotropy indicates the presence of scattering contributions due to spatially dependent saturation magnetization. Moreover, we observe an unusual increase in the magnetization of the rare-earth-based alloy after deformation. Analysis of the SANS cross sections in terms of the correlation function of the spin misalignment reveals the existence of field-dependent anisotropic long-wavelength magnetization fluctuations on a scale of a few tens of nanometers. We also give a detailed account of how the SANS technique relates to unraveling displacement fields on a mesoscopic length scale in disordered magnetic materials.

The conformation of Pluronic block copolymers adsorbed on carbon nanotubes and their interaction with water studied by small-angle neutron scattering

NASA Astrophysics Data System (ADS)

Cohen, Yachin; Granite, Meirav; Pyckhout-Hintzen, Wim; Radulescu, Aurel

2010-03-01

Amphiphilic block copolymers are particularly useful in dispersing single-walled carbon nanotubes (SWCNT) in water. Small-angle neutron scattering measurements conducted at different D2O/H2O content of the dispersing medium provide quantitative information on the adsorption density and conformation of the polymer interacting with the nanotube surface. Data is presented on Pluronic F108 - (EO)132(PO)50(EO)132 and F127 (EO)100(PO)65(EO)100, where EO-ethylene oxide and PO-propylene oxide, well below the critical micellization temperature of the polymer. A dense coating of the PPO blocks on the nanotube surface is determined with the PEO chains extended from the cylindrical core-shell structure. The data from the two Pluronic systems show minimal scattering at about 70% D2O in the dispersing water, which exhibit a q -1 power law of the scattering vector (q ). This indicates near matching of the polymer chains at a surprisingly high scattering length density. The model fit required considerations of tight association of water molecules around PEO chains and slight isotopic selectivity.

Effect of urea on heat-induced gelation of bovine serum albumin (BSA) studied by rheology and small angle neutron scattering (SANS)

NASA Astrophysics Data System (ADS)

Nnyigide, Osita Sunday; Oh, Yuna; Song, Hyeong Yong; Park, Eun-kyoung; Choi, Soo-Hyung; Hyun, Kyu

2017-05-01

This paper reports the effects of urea on the heat-induced gelation of bovine serum albumin (BSA), which was studied by the tube inversion method, rheological measurements, and small-angle neutron scattering (SANS). An increase in the urea concentration accelerated the rate of gelation because the protein molecules have already been unfolded to some extent during sample preparation in the urea solution. In addition, the BSA solution in the presence of urea underwent a sol-gel-sol transition during the time sweep test at a constant temperature of 80oC. On the other hand, the BSA solution without urea turned into a hard and brittle gel that did not return to the solution state during isothermal heating at a constant temperature of 80oC. Aggregation and re-bonding of the denatured and unfolded protein chains led to gel formation. Urea added to the protein denatures its tertiary and secondary structures by simultaneously disrupting the hydrogen bonds, hydrophobic interactions, and altering the solvent properties. Furthermore, urea induces thermoreversible chemical interactions in BSA solutions leading to the formation of a gel with dynamic properties under these experimental conditions.

On the role of block copolymer additives for calcium carbonate crystallization: small angle neutron scattering investigation by applying contrast variation.

PubMed

Endo, Hitoshi; Schwahn, Dietmar; Cölfen, Helmut

2004-05-15

The role of the double-hydrophilic block copolymer poly(ethylen glycol)-block-poly(methacrylic acid) (PEG-b-PMAA) on the morphogenesis of calcium carbonate (CaCO3) was studied by applying the contrast variation small angle neutron scattering technique. The morphology and size of CaCO3 crystals is strongly affected by the addition of PEG-b-PMAA. In order to determine the partial scattering functions of the polymer and CaCO3 mineral, we developed both an experimental and theoretical approach with a sophisticated method of their determination from the scattering intensity. Partial scattering functions give detailed information for each component. In particular, the partial scattering function of the polymer, Spp, shows a monotonic slope with Q(-2 to -3) where the scattering vector Q is low (Q < 0.01 Angstrom(-1)), which is a clear evidence that the polymer within the CaCO3 mineral has a mass fractal dimension. The other partial scattering functions reflected the geometry of the CaCO3 particles or the "interaction" of polymer and CaCO3 on a microscopic scale, which leads to a coherent view with Spp.

Structural and phase transition changes of sodium dodecyl sulfate micellar solution in alcohols probed by small-angle neutron scattering (SANS)

NASA Astrophysics Data System (ADS)

Putra, Edy Giri Rachman; Patriati, Arum

2015-04-01

Small-angle neutron scattering (SANS) measurements on 0.3M sodium dodecyl sulfate (SDS) micellar solutions have been performed in the presence of n-alcohols, from ethanol to decanol at different alcohol concentrations, 2-10 wt%. The ellipsoid micellar structure which occurred in the 0.3M SDS in aqueous solution with the size range of 30-50 Å has different behavior at various hydrocarbon chain length and concentration of alcohols. At low concentration and short chain-length of alcohols, such as ethanol, propanol, and butanol, the size of micelles reduced and had a spherical-like structure. The opposite effect occurred as medium to long chain alcohols, such as hexanol, octanol and decanol was added into the 0.3M SDS micellar solutions. The micelles structure changed to be more elongated in major axis and then crossed the critical phase transition from micellar solution into liquid crystal phase as lamellar structure emerged by further addition of alcohols. The inter-lamellar distances were also depending on the hydrocarbon chain length and concentration of alcohols. In the meantime, the persistent micellar structures occurred in addition of medium chain of n-alcohol, pentanol at all concentrations.

Structural hierarchy of chromatin in chicken erythrocyte nuclei based on small-angle neutron scattering: Fractal nature of the large-scale chromatin organization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lebedev, D. V., E-mail: isaev@omrb.pnpi.spb.ru; Filatov, M. V.; Kuklin, A. I.

The chromatin organization in chicken erythrocyte nuclei was studied by small-angle neutron scattering in the scattering-vector range from 1.5 x 10{sup -1} to 10{sup -4} A{sup -1} with the use of the contrast-variation technique. This scattering-vector range corresponds to linear dimensions from 4 nm to 6 {mu}m and covers the whole hierarchy of chromatin structures, from the nucleosomal structure to the entire nucleus. The results of the present study allowed the following conclusions to be drawn: (1) both the chromatin-protein structure and the structure of the nucleic acid component in chicken erythrocyte nuclei have mass-fractal properties, (2) the structure ofmore » the protein component of chromatin exhibits a fractal behavior on scales extending over two orders of magnitude, from the nucleosomal size to the size of an entire nucleus, and (3) the structure of the nucleic acid component of chromatin in chicken erythrocyte nuclei is likewise of a fractal nature and has two levels of organization or two phases with the crossover point at about 300-400 nm.« less

Morphological structure of Gluconacetobacter xylinus cellulose and cellulose-based organic-inorganic composite materials

NASA Astrophysics Data System (ADS)

Smyslov, R. Yu; Ezdakova, K. V.; Kopitsa, G. P.; Khripunov, A. K.; Bugrov, A. N.; Tkachenko, A. A.; Angelov, B.; Pipich, V.; Szekely, N. K.; Baranchikov, A. E.; Latysheva, E.; Chetverikov, Yu O.; Haramus, V.

2017-05-01

Scanning electron microscopy, ultra-small-angle neutron scattering (USANS), small-angle neutron and X-ray scattering (SANS and SAXS), as well as low-temperature nitrogen adsorption, were used in the studies of micro- and mesostructure of polymer matrix prepared from air-dry preliminarily disintegrated cellulose nano-gel film (synthesized by Gluconacetobacter xylinus) and the composites based on this bacterial cellulose. The composites included ZrO2 nanoparticles, Tb3+ in the form of low molecular weight salt and of metal-polymer complex with poly(vinylpyrrolydone)-poly(methacryloyl-o-aminobenzoic acid) copolymer. The combined analysis of the data obtained allowed revealing three levels of fractal organization in mesostructure of G. xylinus cellulose and its composites. It was shown that both the composition and an aggregation state of dopants have a significant impact on the structural characteristics of the organic-inorganic composites. The composites containing Tb3+ ions demonstrate efficient luminescence; its intensity is an order of magnitude higher in the case of the composites with the metal-polymer complex. It was found that there is the optimal content of ZrO2 nanoparticles in composites resulting in increased Tb3+ luminescence.

Electric Dipole Polarizability of ^{48}Ca and Implications for the Neutron Skin.

PubMed

Birkhan, J; Miorelli, M; Bacca, S; Bassauer, S; Bertulani, C A; Hagen, G; Matsubara, H; von Neumann-Cosel, P; Papenbrock, T; Pietralla, N; Ponomarev, V Yu; Richter, A; Schwenk, A; Tamii, A

2017-06-23

The electric dipole strength distribution in ^{48}Ca between 5 and 25 MeV has been determined at RCNP, Osaka from proton inelastic scattering experiments at forward angles. Combined with photoabsorption data at higher excitation energy, this enables the first extraction of the electric dipole polarizability α_{D}(^{48}Ca)=2.07(22)  fm^{3}. Remarkably, the dipole response of ^{48}Ca is found to be very similar to that of ^{40}Ca, consistent with a small neutron skin in ^{48}Ca. The experimental results are in good agreement with ab initio calculations based on chiral effective field theory interactions and with state-of-the-art density-functional calculations, implying a neutron skin in ^{48}Ca of 0.14-0.20 fm.

Neutron beam measurement of industrial polymer materials for composition and bulk integrity

NASA Astrophysics Data System (ADS)

Rogante, M.; Rosta, L.; Heaton, M. E.

2013-10-01

Neutron beam techniques, among other non-destructive diagnostics, are particularly irreplaceable in the complete analysis of industrial materials and components when supplying fundamental information. In this paper, nanoscale small-angle neutron scattering analysis and prompt gamma activation analysis for the characterization of industrial polymers are considered. The basic theoretical aspects are briefly introduced and some applications are presented. The investigations of the SU-8 polymer in axial airflow microturbines—i.e. microelectromechanical systems—are presented foremost. Also presented are full and feasibility studies on polyurethanes, composites based on cross-linked polymers reinforced by carbon fibres and polymer cement concrete. The obtained results have provided a substantial contribution to the improvement of the considered materials, and indeed confirmed the industrial applicability of the adopted techniques in the analysis of polymers.

Electric Dipole Polarizability of Ca 48 and Implications for the Neutron Skin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Birkhan, J.; Miorelli, M.; Bacca, S.

The electric dipole strength distribution in 48Ca between 5 and 25 MeV has been determined at RCNP, Osaka, from proton inelastic scattering experiments at forward angles. Combined with photoabsorption data at higher excitation energy, this enables the rst extraction of the electric dipole polarizability D( 48Ca) = 2:07(22) fm 3. Remarkably, the dipole response of 48Ca is found to be very similar to that of 40Ca, consistent with a small neutron skin in 48Ca. The experimental results are in good agreement with ab initio calculations based on chiral e ective eld theory interactions and with state-of-the-art density-functional calculations, implying amore » neutron skin in 48Ca of 0:14 - 0:20 fm.« less

Total variation-based neutron computed tomography

NASA Astrophysics Data System (ADS)

Barnard, Richard C.; Bilheux, Hassina; Toops, Todd; Nafziger, Eric; Finney, Charles; Splitter, Derek; Archibald, Rick

2018-05-01

We perform the neutron computed tomography reconstruction problem via an inverse problem formulation with a total variation penalty. In the case of highly under-resolved angular measurements, the total variation penalty suppresses high-frequency artifacts which appear in filtered back projections. In order to efficiently compute solutions for this problem, we implement a variation of the split Bregman algorithm; due to the error-forgetting nature of the algorithm, the computational cost of updating can be significantly reduced via very inexact approximate linear solvers. We present the effectiveness of the algorithm in the significantly low-angular sampling case using synthetic test problems as well as data obtained from a high flux neutron source. The algorithm removes artifacts and can even roughly capture small features when an extremely low number of angles are used.

Electric Dipole Polarizability of Ca 48 and Implications for the Neutron Skin

DOE PAGES

Birkhan, J.; Miorelli, M.; Bacca, S.; ...

2017-06-23

The electric dipole strength distribution in 48Ca between 5 and 25 MeV has been determined at RCNP, Osaka, from proton inelastic scattering experiments at forward angles. Combined with photoabsorption data at higher excitation energy, this enables the rst extraction of the electric dipole polarizability D( 48Ca) = 2:07(22) fm 3. Remarkably, the dipole response of 48Ca is found to be very similar to that of 40Ca, consistent with a small neutron skin in 48Ca. The experimental results are in good agreement with ab initio calculations based on chiral e ective eld theory interactions and with state-of-the-art density-functional calculations, implying amore » neutron skin in 48Ca of 0:14 - 0:20 fm.« less

Preparing Monodisperse Macromolecular Samples for Successful Biological Small-Angle X-ray and Neutron Scattering Experiments

PubMed Central

Jeffries, Cy M.; Graewert, Melissa A.; Blanchet, Clément E.; Langley, David B.; Whitten, Andrew E.; Svergun, Dmitri I

2017-01-01

Small-angle X-ray and neutron scattering (SAXS and SANS) are techniques used to extract structural parameters and determine the overall structures and shapes of biological macromolecules, complexes and assemblies in solution. The scattering intensities measured from a sample contain contributions from all atoms within the illuminated sample volume including the solvent and buffer components as well as the macromolecules of interest. In order to obtain structural information, it is essential to prepare an exactly matched solvent blank so that background scattering contributions can be accurately subtracted from the sample scattering to obtain the net scattering from the macromolecules in the sample. In addition, sample heterogeneity caused by contaminants, aggregates, mismatched solvents, radiation damage or other factors can severely influence and complicate data analysis so it is essential that the samples are pure and monodisperse for the duration of the experiment. This Protocol outlines the basic physics of SAXS and SANS and reveals how the underlying conceptual principles of the techniques ultimately ‘translate’ into practical laboratory guidance for the production of samples of sufficiently high quality for scattering experiments. The procedure describes how to prepare and characterize protein and nucleic acid samples for both SAXS and SANS using gel electrophoresis, size exclusion chromatography and light scattering. Also included are procedures specific to X-rays (in-line size exclusion chromatography SAXS) and neutrons, specifically preparing samples for contrast matching/variation experiments and deuterium labeling of proteins. PMID:27711050

Interaction of the Full-length Bax Protein with Biomimetic Mitochondrial Liposomes: A Small-Angle Neutron Scattering and Fluorescence Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Satsoura, D; Kucerka, Norbert; Shivakumar, S

2012-01-01

In response to apoptotic stimuli, the pro-apoptotic protein Bax inserts in the outer mitochondrial membrane, resulting in the formation of pores and the release of several mitochondrial components, and sealing the cell's fate. To study the binding of Bax to membranes, we used an in vitro system consisting of 50 nm diameter liposomes prepared with a lipid composition mimicking that of mitochondrial membranes in which recombinant purified full-length Bax was inserted via activation with purified tBid. We detected the association of the protein with the membrane using fluorescence fluctuation methods, and found that it could well be described by anmore » equilibrium between soluble and membrane-bound Bax and that at a high protein-toliposome ratio the binding seemed to saturate at about 15 Bax proteins per 50 nm diameter liposome. We then obtained structural data for samples in this saturated binding regime using small-angle neutron scattering under different contrast matching conditions. Utilizing a simple model to fit the neutron data, we observed that a significant amount of the protein mass protrudes above the membrane, in contrast to the conjecture that all of the membrane-associated Bax states are umbrella-like. Upon protein binding, we also observed a thinning of the lipid bilayer accompanied by an increase in liposome radius, an effect reminiscent of the action of antimicrobial peptides on membranes.« less

Small Angle Neutron Scattering Studies on Blends of Poly (Styrene-ran-Vinyl Phenol) with Liquid Crystalline Polyurethane

NASA Astrophysics Data System (ADS)

Mehta, Rujul

2005-03-01

Molecular composites, composed of uniformly dispersed rigid-rod liquid crystalline polymer (LCP) molecules in a flexible amorphous polymer matrix, have remained hitherto elusive due to a scarcity of miscible systems containing a LCP and an amorphous polymer. The production of such a blend, with an experimentally accessible miscibility window, has become possible by modifying the architecture of the flexible polymer, so as to induce favorable intermolecular hydrogen bonding. Specifically, liquid crystalline polyurethanes (LCPU) are found to be miscible with a copolymer of styrene and vinyl phenol; with optimum hydrogen bonding between the carbonyl groups of the urethane linkages and the hydroxyl groups present in the styrenic matrix. Availability of a truly miscible molecular composite presents a unique opportunity of studying the confirmation of polymer chains containing rigid-rods that are uniformly dispersed in a flexible coil matrix. A system consisting of the LCPU and the deuterated styrenic copolymer containing 20% vinyl phenol is examined by Small Angle Neutron Scattering at the National Center for Neutron Research at Gaithersburg and Technology, and the Institute of Solid State Research (IFF) at Jülich. Scattering curves for neat dPS-VPh did not fit the Debye-Bueche model; indicating complex structure. A two correlation length Debye-Bueche model was considered to accommodate for this nonlinear behavior. This model utilizes four fitting parameters, including two correlation lengths a1 and a2, corresponding to a Debye-Bueche model and Guinier model.

Three-dimensional simulations of National Ignition Facility implosions: Insight into experimental observablesa)

NASA Astrophysics Data System (ADS)

Spears, Brian K.; Munro, David H.; Sepke, Scott; Caggiano, Joseph; Clark, Daniel; Hatarik, Robert; Kritcher, Andrea; Sayre, Daniel; Yeamans, Charles; Knauer, James; Hilsabeck, Terry; Kilkenny, Joe

2015-05-01

We simulate in 3D both the hydrodynamics and, simultaneously, the X-ray and neutron diagnostic signatures of National Ignition Facility (NIF) implosions. We apply asymmetric radiation drive to study the impact of low mode asymmetry on diagnostic observables. We examine X-ray and neutron images as well as neutron spectra for these perturbed implosions. The X-ray images show hot spot evolution on small length scales and short time scales, reflecting the incomplete stagnation seen in the simulation. The neutron images show surprising differences from the X-ray images. The neutron spectra provide additional measures of implosion asymmetry. Flow in the hot spot alters the neutron spectral peak, namely, the peak location and width. The changes in the width lead to a variation in the apparent temperature with viewing angle that signals underlying hot spot asymmetry. We compare our new expectations based on the simulated data with NIF data. We find that some recent cryogenic layered experiments show appreciable temperature anisotropy indicating residual flow in the hot spot. We also find some trends in the data that do not reflect our simulation and theoretical understanding.

Neutron Polarization Analysis for Biphasic Solvent Extraction Systems

DOE PAGES

Motokawa, Ryuhei; Endo, Hitoshi; Nagao, Michihiro; ...

2016-06-16

Here we performed neutron polarization analysis (NPA) of extracted organic phases containing complexes, comprised of Zr(NO 3) 4 and tri-n-butyl phosphate, which enabled decomposition of the intensity distribution of small-angle neutron scattering (SANS) into the coherent and incoherent scattering components. The coherent scattering intensity, containing structural information, and the incoherent scattering compete over a wide range of magnitude of scattering vector, q, specifically when q is larger than q* ≈ 1/R g, where R g is the radius of gyration of scatterer. Therefore, it is important to determine the incoherent scattering intensity exactly to perform an accurate structural analysis frommore » SANS data when R g is small, such as the aforementioned extracted coordination species. Although NPA is the best method for evaluating the incoherent scattering component for accurately determining the coherent scattering in SANS, this method is not used frequently in SANS data analysis because it is technically challenging. In this study, we successfully demonstrated that experimental determination of the incoherent scattering using NPA is suitable for sample systems containing a small scatterer with a weak coherent scattering intensity, such as extracted complexes in biphasic solvent extraction systems.« less

Probing the possibility of hotspots on the central neutron star in HESS J1731-347

NASA Astrophysics Data System (ADS)

Suleimanov, V. F.; Klochkov, D.; Poutanen, J.; Werner, K.

2017-04-01

The X-ray spectra of the neutron stars located in the centers of supernova remnants Cas A and HESS J1731-347 are well fit with carbon atmosphere models. These fits yield plausible neutron star sizes for the known or estimated distances to these supernova remnants. The evidence in favor of the presence of a pure carbon envelope at the neutron star surface is rather indirect and is based on the assumption that the emission is generated uniformly by the entire stellar surface. Although this assumption is supported by the absence of pulsations, the observational upper limit on the pulsed fraction is not very stringent. In an attempt to quantify this evidence, we investigate the possibility that the observed spectrum of the neutron star in HESS J1731-347 is a combination of the spectra produced in a hydrogen atmosphere of the hotspots and of the cooler remaining part of the neutron star surface. The lack of pulsations in this case has to be explained either by a sufficiently small angle between the neutron star spin axis and the line of sight, or by a sufficiently small angular distance between the hotspots and the neutron star rotation poles. As the observed flux from a non-uniformly emitting neutron star depends on the angular distribution of the radiation emerging from the atmosphere, we have computed two new grids of pure carbon and pure hydrogen atmosphere model spectra accounting for Compton scattering. Using new hydrogen models, we have evaluated the probability of a geometry that leads to a pulsed fraction below the observed upper limit to be about 8.2%. Such a geometry thus seems to be rather improbable but cannot be excluded at this stage.

A NARROW SHORT-DURATION GRB JET FROM A WIDE CENTRAL ENGINE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duffell, Paul C.; Quataert, Eliot; MacFadyen, Andrew I., E-mail: duffell@berkeley.edu

2015-11-01

We use two-dimensional relativistic hydrodynamic numerical calculations to show that highly collimated relativistic jets can be produced in neutron star merger models of short-duration gamma-ray bursts (GRBs) without the need for a highly directed engine or a large net magnetic flux. Even a hydrodynamic engine generating a very wide sustained outflow on small scales can, in principle, produce a highly collimated relativistic jet, facilitated by a dense surrounding medium that provides a cocoon surrounding the jet core. An oblate geometry to the surrounding gas significantly enhances the collimation process. Previous numerical simulations have shown that the merger of two neutronmore » stars produces an oblate, expanding cloud of dynamical ejecta. We show that this gas can efficiently collimate the central engine power much like the surrounding star does in long-duration GRB models. For typical short-duration GRB central engine parameters, we find jets with opening angles of an order of 10° in which a large fraction of the total outflow power of the central engine resides in highly relativistic material. These results predict large differences in the opening angles of outflows from binary neutron star mergers versus neutron star–black hole mergers.« less

Elastic and Inelastic Scattering of Neutrons using a CLYC array

NASA Astrophysics Data System (ADS)

Brown, Tristan; Doucet, E.; Chowdhury, P.; Lister, C. J.; Wilson, G. L.; Devlin, M.; Mosby, S.

2015-10-01

CLYC scintillators, which have dual neutron and gamma response, have recently ushered in the possibility of fast neutron spectroscopy without time-of-flight (TOF). A 16-element array of 1'' x 1'' 6Li-depleted CLYC crystals, where pulse-shape-discrimination is achieved via digital pulse processing, has been commissioned at UMass Lowell. In an experiment at LANSCE, high energy neutrons were used to bombard 56Fe and 238U targets, in order to measure elastic and inelastic neutron scattering cross sections as a function of energy and angle with the array. The array is placed very close to the targets for enhanced geometrical solid angles for scattered neutrons compared to standard neutron-TOF measurements. A pulse-height spectrum of scattered neutrons in the detectors is compared to the energy of the incident neutrons, which is measured via the TOF of the pulsed neutrons from the source to the detectors. Recoil corrections are necessary to combine the energy spectra from all the detectors to obtain angle-integrated elastic and inelastic cross-sections. The detection techniques, analysis procedures and results will be presented. Supported by NNSA-SSAA program through DOE Grant DE-NA00013008.

Neutron Reflectivity and Grazing Angle Diffraction

PubMed Central

Ankner, J. F.; Majkrzak, C. F.; Satija, S. K.

1993-01-01

Over the last 10 years, neutron reflectivity has emerged as a powerful technique for the investigation of surface and interfacial phenomena in many different fields. In this paper, a short review of some of the work on neutron reflectivity and grazing-angle diffraction as well as a description of the current and planned neutron rcflectometers at NIST is presented. Specific examples of the characterization of magnetic, superconducting, and polymeric surfaces and interfaces are included. PMID:28053457

Study of nanoscale structures in hydrated biomaterials using small-angle neutron scattering

PubMed Central

Luk, Arnold; Murthy, N. Sanjeeva; Wang, Wenjie; Rojas, Ramiro; Kohn, Joachim

2012-01-01

Distribution of water in three classes of biomedically relevant and degradable polymers was investigated using small-angle neutron scattering. In semicrystalline polymers, such as poly(lactic acid) and poly(glycolic acid), water was found to diffuse preferentially into the noncrystalline regions. In amorphous polymers, such as poly(D,L-lactic acid) and poly(lactic-co-glycolic acid), the scattering after 7-days of incubation was attributed to water in microvoids that form following the hydrolytic degradation of the polymer. In amorphous copolymers containing hydrophobic segments (desaminotyrosyl-tyrosine ethyl ester) and hydrophilic blocks (poly(ethylene glycol) PEG), a sequence of distinct regimes of hydration were observed: homogeneous distribution (~ 10 Å length scales) at <13 wt% PEG (~ 1 water per EG), clusters of hydrated domains (~50 Å radius) separated at 24 wt% PEG (1 to 2 water per EG), uniformly distributed hydrated domains at 41 wt% PEG (~ 4 water per EG), and phase inversion at > 50 wt% PEG ( > 6 water per EG ). Increasing PEG content increased the number of these domains with only a small decrease in distance between the domains. These discrete domains appeared to coalesce to form submicron droplets at ~60 °C, above the melting temperature of crystalline PEG. Significance of such observations on the evolution of μm size channels that form during hydrolytic erosion is discussed. PMID:22227373

DHS Summary Report -- Robert Weldon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weldon, Robert A.

This summer I worked on benchmarking the Lawrence Livermore National Laboratory fission multiplicity capability used in the Monte Carlo particle transport code MCNPX. This work involved running simulations and then comparing the simulation results with experimental experiments. Outlined in this paper is a brief description of the work completed this summer, skills and knowledge gained, and how the internship has impacted my planning for the future. Neutron multiplicity counting is a neutron detection technique that leverages the multiplicity emissions of neutrons from fission to identify various actinides in a lump of material. The identification of individual actinides in lumps ofmore » material crossing our boarders, especially U-235 and Pu-239, is a key component for maintaining the safety of the country from nuclear threats. Several multiplicity emission options from spontaneous and induced fission already existed in MCNPX 2.4.0. These options can be accessed through use of the 6th entry on the PHYS:N card. Lawrence Livermore National Laboratory (LLNL) developed a physics model for the simulation of neutron and gamma ray emission from fission and photofission that was included in MCNPX 2.7.B as an undocumented feature and then was documented in MCNPX 2.7.C. The LLNL multiplicity capability provided a different means for MCNPX to simulate neutron and gamma-ray distributions for neutron induced, spontaneous and photonuclear fission reactions. The original testing on the model for implementation into MCNPX was conducted by Gregg McKinney and John Hendricks. The model is an encapsulation of measured data of neutron multiplicity distributions from Gwin, Spencer, and Ingle, along with the data from Zucker and Holden. One of the founding principles of MCNPX was that it would have several redundant capabilities, providing the means of testing and including various physics packages. Though several multiplicity sampling methodologies already existed within MCNPX, the LLNL fission multiplicity was included to provide a separate capability for computing multiplicity as well as including several new features not already included in MCNPX. These new features include: (1) prompt gamma emission/multiplicity from neutron-induced fission; (2) neutron multiplicity and gamma emission/multiplicity from photofission; and (3) an option to enforce energy correlation for gamma neutron multiplicity emission. These new capabilities allow correlated signal detection for identifying presence of special nuclear material (SNM). Therefore, these new capabilities help meet the missions of the Domestic Nuclear Detection Office (DNDO), which is tasked with developing nuclear detection strategies for identifying potential radiological and nuclear threats, by providing new simulation capability for detection strategies that leverage the new available physics in the LLNL multiplicity capability. Two types of tests were accomplished this summer to test the default LLNL neutron multiplicity capability: neutron-induced fission tests and spontaneous fission tests. Both cases set the 6th entry on the PHYS:N card to 5 (i.e. use LLNL multiplicity). The neutron-induced fission tests utilized a simple 0.001 cm radius sphere where 0.0253 eV neutrons were released at the sphere center. Neutrons were forced to immediately collide in the sphere and release all progeny from the sphere, without further collision, using the LCA card, LCA 7j -2 (therefore density and size of the sphere were irrelevant). Enough particles were run to ensure that the average error of any specific multiplicity did not exceed 0.36%. Neutron-induced fission multiplicities were computed for U-233, U-235, Pu-239, and Pu-241. The spontaneous fission tests also used the same spherical geometry, except: (1) the LCA card was removed; (2) the density of the sphere was set to 0.001 g/cm3; and (3) instead of emitting a thermal neutron, the PAR keyword was set to PAR=SF. The purpose of the small density was to ensure that the spontaneous fission neutrons would not further interact and induce fissions (i.e. the mean free path greatly exceeded the size of the sphere). Enough particles were run to ensure that the average error of any specific spontaneous multiplicity did not exceed 0.23%. Spontaneous fission multiplicities were computed for U-238, Pu-238, Pu-240, Pu-242, Cm-242, and Cm-244. All of the computed results were compared against experimental results compiled by Holden at Brookhaven National Laboratory.« less

Crystallization in Micellar Cores: confinement effects and dynamics

NASA Astrophysics Data System (ADS)

Lund, Reidar; Zinn, Thomas; Willner, Lutz; Department of Chemistry, University of Oslo Team; Forschungszentrum Jülich Collaboration

It is well known that liquids confined to small nanoscopic pores and droplets exhibit thermal behavior very different from bulk samples. Here we demonstrate that n-alkanes forming 2-3 nm small micellar cores are considerably affected by confinement in analogue with hard confined systems. We study micelles form by self-assembly of a series of well-defined n-Alkyl-PEO polymers in aqueous solutions. By using small-angle X-ray scattering (SAXS), densiometry and differential scanning calorimetry (DSC), we show that n-alkane exhibit a first-order phase transition i.e. melting. Correlating the structural and thermodynamic data, we find that a melting depression can be accurately described by the Gibbs-Thomson equation. ∖f1 The effect of core crystallinity on the molecular exchange kinetics is investigated using time-resolved small-angle neutron scattering (TR-SANS). We show that there are considerable entropic and enthalpic contributions from the chain packing that affect the kinetic stability of micelles. ∖pard

Thermal expansion of monogermanides of 3d-metals

NASA Astrophysics Data System (ADS)

Valkovskiy, G. A.; Altynbaev, E. V.; Kuchugura, M. D.; Yashina, E. G.; Sukhanov, A. S.; Dyadkin, V. A.; Tsvyashchenko, A. V.; Sidorov, V. A.; Fomicheva, L. N.; Bykova, E.; Ovsyannikov, S. V.; Chernyshov, D. Yu; Grigoriev, S. V.

2016-09-01

Temperature dependent powder and single-crystal synchrotron diffraction, specific heat, magnetic susceptibility and small-angle neutron scattering experiments have revealed an anomalous response of MnGe. The anomaly becomes smeared out with decreasing Mn content in Mn1-x Co x Ge and Mn1-x Fe x Ge solid solutions. Mn spin state instability is discussed as a possible candidate for the observed effects.

The roles of RIIbeta linker and N-terminal cyclic nucleotide-binding domain in determining the unique structures of Type IIbeta Protein Kinase A. A small angle X-ray and neutron scattering study

DOE PAGES

Blumenthal, Donald K.; Copps, Jeffrey; Smith-Nguyen, Eric V.; ...

2014-08-11

Protein kinase A (PKA) is ubiquitously expressed and is responsible for regulating many important cellular functions in response to changes in intracellular cAMP concentrations. Moreover, the PKA holoenzyme is a tetramer (R 2:C 2), with a regulatory subunit homodimer (R 2) that binds and inhibits two catalytic (C) subunits; binding of cAMP to the regulatory subunit homodimer causes activation of the catalytic subunits. Four different R subunit isoforms exist in mammalian cells, and these confer different structural features, subcellular localization, and biochemical properties upon the PKA holoenzymes they form. The holoenzyme containing RIIβ is structurally unique in that the typemore » IIβ holoenzyme is much more compact than the free RIIβ homodimer. We have used small angle x-ray scattering and small angle neutron scattering to study the solution structure and subunit organization of a holoenzyme containing an RIIβ C-terminal deletion mutant (RIIβ(1–280)), which is missing the C-terminal cAMP-binding domain to better understand the structural organization of the type IIβ holoenzyme and the RIIβ domains that contribute to stabilizing the holoenzyme conformation. These results demonstrate that compaction of the type IIβ holoenzyme does not require the C-terminal cAMP-binding domain but rather involves large structural rearrangements within the linker and N-terminal cyclic nucleotide-binding domain of the RIIβ homodimer. The structural rearrangements are significantly greater than seen previously with RIIα and are likely to be important in mediating short range and long range interdomain and intersubunit interactions that uniquely regulate the activity of the type IIβ isoform of PKA.« less

The roles of the RIIβ linker and N-terminal cyclic nucleotide-binding domain in determining the unique structures of the type IIβ protein kinase A: a small angle x-ray and neutron scattering study.

PubMed

Blumenthal, Donald K; Copps, Jeffrey; Smith-Nguyen, Eric V; Zhang, Ping; Heller, William T; Taylor, Susan S

2014-10-10

Protein kinase A (PKA) is ubiquitously expressed and is responsible for regulating many important cellular functions in response to changes in intracellular cAMP concentrations. The PKA holoenzyme is a tetramer (R2:C2), with a regulatory subunit homodimer (R2) that binds and inhibits two catalytic (C) subunits; binding of cAMP to the regulatory subunit homodimer causes activation of the catalytic subunits. Four different R subunit isoforms exist in mammalian cells, and these confer different structural features, subcellular localization, and biochemical properties upon the PKA holoenzymes they form. The holoenzyme containing RIIβ is structurally unique in that the type IIβ holoenzyme is much more compact than the free RIIβ homodimer. We have used small angle x-ray scattering and small angle neutron scattering to study the solution structure and subunit organization of a holoenzyme containing an RIIβ C-terminal deletion mutant (RIIβ(1-280)), which is missing the C-terminal cAMP-binding domain to better understand the structural organization of the type IIβ holoenzyme and the RIIβ domains that contribute to stabilizing the holoenzyme conformation. Our results demonstrate that compaction of the type IIβ holoenzyme does not require the C-terminal cAMP-binding domain but rather involves large structural rearrangements within the linker and N-terminal cyclic nucleotide-binding domain of the RIIβ homodimer. The structural rearrangements are significantly greater than seen previously with RIIα and are likely to be important in mediating short range and long range interdomain and intersubunit interactions that uniquely regulate the activity of the type IIβ isoform of PKA. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

In situ assessment of the contact angles of nanoparticles adsorbed at fluid interfaces by multiple angle of incidence ellipsometry.

PubMed

Stocco, Antonio; Su, Ge; Nobili, Maurizio; In, Martin; Wang, Dayang

2014-09-28

Here multiple angle of incidence ellipsometry was successfully applied to in situ assess the contact angle and surface coverage of gold nanoparticles as small as 18 nm, coated with stimuli-responsive polymers, at water-oil and water-air interfaces in the presence of NaCl and NaOH, respectively. The interfacial adsorption of the nanoparticles was found to be very slow and took days to reach a fairly low surface coverage. For water-oil interfaces, in situ nanoparticle contact angles agree with the macroscopic equilibrium contact angles of planar gold surfaces with the same polymer coatings, whilst for water-air interfaces, significant differences have been observed.

Associated-particle sealed-tube neutron probe for nonintrusive inspection

NASA Astrophysics Data System (ADS)

Rhodes, E.; Dickerman, C. E.

1997-02-01

The development and investigation of a small associated-particle sealed-tube neutron generator (APSTNG) show potential for the associated-particle method to move out of the laboratory into field applications. This paper is a review of ANL investigations of this technology. Alpha particles associated with 14-MeV neutrons generated from the D-T reaction travel in the opposite direction and are detected inside the sealed tube. Gamma-ray spectra of resulting neutron reactions in the inspected volume encompassed by the alpha-detector solid angle identify many nuclides. Flight-times determined from detection times of the gamma rays and alpha particles separate the prompt and delayed gamma-rays and can yield a separate coarse tomographic image of each identified nuclide, from a single orientation without collimation. A continuous ion beam allows data acquisition by relatively low-bandwidth electronics. When a compact sealed-tube neutron generator is used, a relatively small and easily maintainable inspection system can be developed, that is rugged enough to be transportable. Proof-of-concept laboratory experiments have been performed for simulated explosives, drugs, special nuclear materials, and chemical warfare agents. Efficient collection of maximum information from each detected neutron with low background rates can allow a much lower source intensity than pulsed accelerator methods and yield a preference for an APSTNG system, when it can provide adequate usable source intensity. Based on lessons learned with the present system, an advanced APSTNG system is being designed and built that will be transportable and yield substantial increases in neutron output and target lifetime.

Effects of Pressure on Stability of Biomolecules in Solutions Studied by Neutron Scattering

NASA Astrophysics Data System (ADS)

Bellissent-Funel, Marie-Claire-; Appavou, Marie-Sousai; Gibrat, Gabriel

Studies of the pressure dependence on protein structure and dynamics contribute not only to the basic knowledge of biological molecules but have also a considerable relevance in full technology, like in food sterilization and pharmacy. Conformational changes induced by pressure as well as the effects on the protein stability have been mostly studied by optical techniques (optical absorption, fluorescence, phosphorescence), and by NMR. Most optical techniques used so far give information related to the local nature of the used probe (fluorescent or phosphorescent tryptophan). Small angle neutron scattering and quasi-elastic neutron scattering provide essential complementary information to the optical data, giving quantitative data on change of conformation of soluble globular proteins such as bovine pancreatic trypsin inhibitor (BPTI) and on the mobility of protons belonging to the protein surface residues.

Aggregation study in mixture surfactant system TX-100+SDS in heavy water solutions by SANS method

NASA Astrophysics Data System (ADS)

Rajewska, A.; Islamov, A. Kh.; Bakeeva, R. F.

2018-03-01

The mixing of amphiphiles in water may lead to the formation of mixed micelles which often present new properties with respect to the pure component solutions [1,2]. The mixture system of classic surfactants SDS (sodium dodecyl sulfate)+TX-100(p-(1,1,3,3- tetramethyl) poly(oxyethylene) (anionic + non-ionic) in heavy water solutions was investigated at temperatures 30°, 50°, 70°C for compositions 1:1, 2:1, 3:1 by the small-angle neutron scattering(SANS) method on spectrometer (‘YuMO’) at the IBR-2 pulsed neutron source at FLNP, JINR in Dubna (Russia). Measurements have covered Q range from 8x10-3 to 0.4 Å-1. From the measured dependence of the scattered intensity on the scattering angle, we derived the size, shape of micelles, aggregation number at various compositions and temperatures. The size of mixed micelle is a weak function of the mixing ratio between the two components.

Future directions in high-pressure neutron diffraction

NASA Astrophysics Data System (ADS)

Guthrie, M.

2015-04-01

The ability to manipulate structure and properties using pressure has been well known for many centuries. Diffraction provides the unique ability to observe these structural changes in fine detail on lengthscales spanning atomic to nanometre dimensions. Amongst the broad suite of diffraction tools available today, neutrons provide unique capabilities of fundamental importance. However, to date, the growth of neutron diffraction under extremes of pressure has been limited by the weakness of available sources. In recent years, substantial government investments have led to the construction of a new generation of neutron sources while existing facilities have been revitalized by upgrades. The timely convergence of these bright facilities with new pressure-cell technologies suggests that the field of high-pressure (HP) neutron science is on the cusp of substantial growth. Here, the history of HP neutron research is examined with the hope of gleaning an accurate prediction of where some of these revolutionary capabilities will lead in the near future. In particular, a dramatic expansion of current pressure-temperature range is likely, with corresponding increased scope for extreme-conditions science with neutron diffraction. This increase in coverage will be matched with improvements in data quality. Furthermore, we can also expect broad new capabilities beyond diffraction, including in neutron imaging, small angle scattering and inelastic spectroscopy.

Calculation of Spectra of Neutrons and Charged Particles Produced in a Target of a Neutron Generator

NASA Astrophysics Data System (ADS)

Gaganov, V. V.

2017-12-01

An algorithm for calculating the spectra of neutrons and associated charged particles produced in the target of a neutron generator is detailed. The products of four nuclear reactions 3H( d, n)4He, 2H( d, n)3He, 2H( d, p)3H, and 3He( d, p)4He are analyzed. The results of calculations are presented in the form of neutron spectra for several emission angles and spectra of associated charged particles emitted at an angle of 180° for a deuteron initial energy of 0.13 MeV.

New opportunities for quasielastic and inelastic neutron scattering at steady-state sources using mechanical selection of the incident and final neutron energy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mamantov, Eugene

2015-06-12

We propose a modification of the neutron wide-angle velocity selector (WAVES) device that enables inelastic (in particular, quasielastic) scattering measurements not relying on the neutron time-of-flight. The proposed device is highly suitable for a steady-state neutron source, somewhat similar to a triple-axis spectrometer, but with simultaneous selection of the incident and final neutron energy over a broad range of scattering momentum transfer. Both the incident and final neutron velocities are defined by the WAVES geometry and rotation frequency. The variable energy transfer is achieved through the natural variation of the velocity of the transmitted neutrons as a function of themore » scattering angle component out of the equatorial plane.« less

A versatile UHV transport and measurement chamber for neutron reflectometry under UHV conditions

NASA Astrophysics Data System (ADS)

Syed Mohd, A.; Pütter, S.; Mattauch, S.; Koutsioubas, A.; Schneider, H.; Weber, A.; Brückel, T.

2016-12-01

We report on a versatile mini ultra-high vacuum (UHV) chamber which is designed to be used on the MAgnetic Reflectometer with high Incident Angle of the Jülich Centre for Neutron Science at Heinz Maier-Leibnitz Zentrum in Garching, Germany. Samples are prepared in the adjacent thin film laboratory by molecular beam epitaxy and moved into the compact chamber for transfer without exposure to ambient air. The chamber is based on DN 40 CF flanges and equipped with sapphire view ports, a small getter pump, and a wobble stick, which serves also as sample holder. Here, we present polarized neutron reflectivity measurements which have been performed on Co thin films at room temperature in UHV and in ambient air in a magnetic field of 200 mT and in the Q-range of 0.18 Å-1. The results confirm that the Co film is not contaminated during the polarized neutron reflectivity measurement. Herewith it is demonstrated that the mini UHV transport chamber also works as a measurement chamber which opens new possibilities for polarized neutron measurements under UHV conditions.

A versatile UHV transport and measurement chamber for neutron reflectometry under UHV conditions.

PubMed

Syed Mohd, A; Pütter, S; Mattauch, S; Koutsioubas, A; Schneider, H; Weber, A; Brückel, T

2016-12-01

We report on a versatile mini ultra-high vacuum (UHV) chamber which is designed to be used on the MAgnetic Reflectometer with high Incident Angle of the Jülich Centre for Neutron Science at Heinz Maier-Leibnitz Zentrum in Garching, Germany. Samples are prepared in the adjacent thin film laboratory by molecular beam epitaxy and moved into the compact chamber for transfer without exposure to ambient air. The chamber is based on DN 40 CF flanges and equipped with sapphire view ports, a small getter pump, and a wobble stick, which serves also as sample holder. Here, we present polarized neutron reflectivity measurements which have been performed on Co thin films at room temperature in UHV and in ambient air in a magnetic field of 200 mT and in the Q-range of 0.18 Å -1 . The results confirm that the Co film is not contaminated during the polarized neutron reflectivity measurement. Herewith it is demonstrated that the mini UHV transport chamber also works as a measurement chamber which opens new possibilities for polarized neutron measurements under UHV conditions.

Designing Mixed Detergent Micelles for Uniform Neutron Contrast

DOE PAGES

Oliver, Ryan C.; Pingali, Sai Venkatesh; Urban, Volker S.

2017-09-29

Micelle-forming detergents provide an amphipathic environment that mimics lipid bilayers and are important tools used to solubilize and stabilize membrane proteins in solution for in vitro structural investigations. Small-angle neutron scattering (SANS) performed at the neutron contrast match point of detergent molecules allows observing the scattering signal from membrane proteins unobstructed by contributions from the detergent. However, we show here that even for a perfectly average-contrast matched detergent there arises significant core-shell scattering from the contrast difference between aliphatic detergent tails and hydrophilic head groups. This residual signal at the average detergent contrast match point interferes with interpreting structural datamore » of membrane proteins. This complication is often made worse by the presence of excess empty (protein-free) micelles. Here, we present an approach for the rational design of mixed micelles containing a deuterated detergent analog, which eliminates neutron contrast between core and shell, and allows the micelle scattering to be fully contrast matched to unambiguously resolve membrane protein structure using solution SANS.« less

Designing Mixed Detergent Micelles for Uniform Neutron Contrast

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oliver, Ryan C.; Pingali, Sai Venkatesh; Urban, Volker S.

Micelle-forming detergents provide an amphipathic environment that mimics lipid bilayers and are important tools used to solubilize and stabilize membrane proteins in solution for in vitro structural investigations. Small-angle neutron scattering (SANS) performed at the neutron contrast match point of detergent molecules allows observing the scattering signal from membrane proteins unobstructed by contributions from the detergent. However, we show here that even for a perfectly average-contrast matched detergent there arises significant core-shell scattering from the contrast difference between aliphatic detergent tails and hydrophilic head groups. This residual signal at the average detergent contrast match point interferes with interpreting structural datamore » of membrane proteins. This complication is often made worse by the presence of excess empty (protein-free) micelles. Here, we present an approach for the rational design of mixed micelles containing a deuterated detergent analog, which eliminates neutron contrast between core and shell, and allows the micelle scattering to be fully contrast matched to unambiguously resolve membrane protein structure using solution SANS.« less

Neutron scattering shows a droplet of oleic acid at the center of the BAMLET complex.

PubMed

Rath, Emma M; Duff, Anthony P; Gilbert, Elliot P; Doherty, Greg; Knott, Robert B; Church, W Bret

2017-07-01

The anti-cancer complex, Bovine Alpha-lactalbumin Made LEthal to Tumors (BAMLET), has intriguing broad-spectrum anti-cancer activity. Although aspects of BAMLET's anti-cancer mechanism are still not known, it is understood that it involves the oleic acid or oleate component of BAMLET being preferentially released into cancer cell membranes leading to increased membrane permeability and lysis. The structure of the protein component of BAMLET has previously been elucidated by small angle X-ray scattering (SAXS) to be partially unfolded and dramatically enlarged. However, the structure of the oleic acid component of BAMLET and its disposition with respect to the protein component was not revealed as oleic acid has the same X-ray scattering length density (SLD) as water. Employing the difference in the neutron SLDs of hydrogen and deuterium, we carried out solvent contrast variation small angle neutron scattering (SANS) experiments of hydrogenated BAMLET in deuterated water buffers, to reveal the size, shape, and disposition of the oleic acid component of BAMLET. Our resulting analysis and models generated from SANS and SAXS data indicate that oleic acid forms a spherical droplet of oil incompletely encapsulated by the partially unfolded protein component. This model provides insight into the anti-cancer mechanism of this cache of lipid. The model also reveals a protein component "tail" not associated with the oleic acid component that is able to interact with the tail of other BAMLET molecules, providing a plausible explanation of how BAMLET readily forms aggregates. Proteins 2017; 85:1371-1378. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Small angle neutron scattering from 1-alkyl-3-methylimidazolium hexafluorophosphate ionic liquids ([Cnmim][PF6], n=4, 6, and 8)

NASA Astrophysics Data System (ADS)

Hardacre, Christopher; Holbrey, John D.; Mullan, Claire L.; Youngs, Tristan G. A.; Bowron, Daniel T.

2010-08-01

The presence of local anisotropy in the bulk, isotropic, and ionic liquid phases—leading to local mesoscopic inhomogeneity—with nanoscale segregation and expanding nonpolar domains on increasing the length of the cation alkyl-substituents has been proposed on the basis of molecular dynamics (MD) simulations. However, there has been little conclusive experimental evidence for the existence of intermediate mesoscopic structure between the first/second shell correlations shown by neutron scattering on short chain length based materials and the mesophase structure of the long chain length ionic liquid crystals. Herein, small angle neutron scattering measurements have been performed on selectively H/D-isotopically substituted 1-alkyl-3-methylimidazolium hexafluorophosphate ionic liquids with butyl, hexyl, and octyl substituents. The data show the unambiguous existence of a diffraction peak in the low-Q region for all three liquids which moves to longer distances (lower Q), sharpens, and increases in intensity with increasing length of the alkyl substituent. It is notable, however, that this peak occurs at lower values of Q (longer length scale) than predicted in any of the previously published MD simulations of ionic liquids, and that the magnitude of the scattering from this peak is comparable with that from the remainder of the amorphous ionic liquid. This strongly suggests that the peak arises from the second coordination shells of the ions along the vector of alkyl-chain substituents as a consequence of increasing the anisotropy of the cation, and that there is little or no long-range correlated nanostructure in these ionic liquids.

Beyond simple small-angle X-ray scattering: developments in online complementary techniques and sample environments.

PubMed

Bras, Wim; Koizumi, Satoshi; Terrill, Nicholas J

2014-11-01

Small- and wide-angle X-ray scattering (SAXS, WAXS) are standard tools in materials research. The simultaneous measurement of SAXS and WAXS data in time-resolved studies has gained popularity due to the complementary information obtained. Furthermore, the combination of these data with non X-ray based techniques, via either simultaneous or independent measurements, has advanced understanding of the driving forces that lead to the structures and morphologies of materials, which in turn give rise to their properties. The simultaneous measurement of different data regimes and types, using either X-rays or neutrons, and the desire to control parameters that initiate and control structural changes have led to greater demands on sample environments. Examples of developments in technique combinations and sample environment design are discussed, together with a brief speculation about promising future developments.

Beyond simple small-angle X-ray scattering: developments in online complementary techniques and sample environments

PubMed Central

Bras, Wim; Koizumi, Satoshi; Terrill, Nicholas J

2014-01-01

Small- and wide-angle X-ray scattering (SAXS, WAXS) are standard tools in materials research. The simultaneous measurement of SAXS and WAXS data in time-resolved studies has gained popularity due to the complementary information obtained. Furthermore, the combination of these data with non X-ray based techniques, via either simultaneous or independent measurements, has advanced understanding of the driving forces that lead to the structures and morphologies of materials, which in turn give rise to their properties. The simultaneous measurement of different data regimes and types, using either X-rays or neutrons, and the desire to control parameters that initiate and control structural changes have led to greater demands on sample environments. Examples of developments in technique combinations and sample environment design are discussed, together with a brief speculation about promising future developments. PMID:25485128

PASTIS2 and CROCODILE: XYZ-wide angle polarisation analysis for thermal neutrons

NASA Astrophysics Data System (ADS)

Enderle, Mechthild; Jullien, David; Petoukhov, Alexander; Mouveau, Pascal; Andersen, Ken; Courtois, Pierre

2017-06-01

We present a wide-angle device for inelastic neutron scattering with XYZ-polarisation analysis (PASTIS2). PASTIS2 employs a banana-shaped Si-walled 3He-filter for the polarisation analysis and allows pillar-free neutron scattering for horizontal scattering angles 0-100◦. The guide field direction at the sample can be chosen vertical or with 45◦ incremental steps in the horizontal scattering plane. When PASTIS2 is implemented on a polarised neutron beam, the incident neutron spin can be flipped with an easy-to-optimise broad-band adiabatic resonant flipper (CROCODILE) independent of the guide field direction at the sample position. We have tested the performance of this new device on the polarised thermal triple-axis spectrometer IN20 at the Institut Laue-Langevin, equipped with Heusler monochromator and the FlatCone multi-analyser, and discuss its potential for future instruments.

Cation-containing lipid membranes – experiment and md simulations

DOE PAGES

Kučerka, Norbert; Dushanov, Ermuhammas; Kholmurodov, Kholmirzo T.; ...

2017-11-27

Here, using small angle neutron diffraction and molecular dynamics simulations we studied the interactions between calcium (Ca 2+) or zinc (Zn 2+) cations, and oriented gel phase dipalmitoyl-phosphatidylcholine (DPPC) bilayers. For both cations studied at ~1:7 divalent metal ion to lipid molar ratio (Me2+:DPPC), bilayer thickness increased. Simulation results helped reveal subtle differences in the effects of the two cations on gel phase membranes.

Structure functions in decomposing Au-Pt systems

NASA Astrophysics Data System (ADS)

Glas, R.; Blaschko, O.; Rosta, L.

1992-09-01

The evolution of Au-Pt alloys quenched within the miscibility gap is investigated by small-angle neutron-scattering techniques. Moreover, in the vicinity of fundamental Bragg reflections the evolution of ``sideband'' satellites induced by a lattice-parameter modulation connected with the precipitation pattern is investigated by diffuse scattering methods. Structure functions are evaluated for a series of concentrations within the miscibility gap and compared to recent results of the literature.

Small angle neutron scattering as a tool to evaluate moisture-induced swelling in the nanostructure of chemically modified wood cell walls

Treesearch

Nayomi Z. Plaza; Joseph E. Jakes; Charles R. Frihart; Christopher G. Hunt; Daniel J. Yelle; Linda F. Lorenz

2017-01-01

Wood-based products can be a sustainable and more environmentally friendly alternative to traditional construction materials because of their reduced contribution to air and water pollution. An integral component of these products is often an adhesive. Because wood is hygroscopic, moisture-induced swelling in the cell walls near the wood– adhesive bondlines can lead to...

Elucidation of spin echo small angle neutron scattering correlation functions through model studies.

PubMed

Shew, Chwen-Yang; Chen, Wei-Ren

2012-02-14

Several single-modal Debye correlation functions to approximate part of the overall Debey correlation function of liquids are closely examined for elucidating their behavior in the corresponding spin echo small angle neutron scattering (SESANS) correlation functions. We find that the maximum length scale of a Debye correlation function is identical to that of its SESANS correlation function. For discrete Debye correlation functions, the peak of SESANS correlation function emerges at their first discrete point, whereas for continuous Debye correlation functions with greater width, the peak position shifts to a greater value. In both cases, the intensity and shape of the peak of the SESANS correlation function are determined by the width of the Debye correlation functions. Furthermore, we mimic the intramolecular and intermolecular Debye correlation functions of liquids composed of interacting particles based on a simple model to elucidate their competition in the SESANS correlation function. Our calculations show that the first local minimum of a SESANS correlation function can be negative and positive. By adjusting the spatial distribution of the intermolecular Debye function in the model, the calculated SESANS spectra exhibit the profile consistent with that of hard-sphere and sticky-hard-sphere liquids predicted by more sophisticated liquid state theory and computer simulation. © 2012 American Institute of Physics

Small-angle neutron scattering study of specific interaction and coordination structure formed by mono-acetyl-substituted dibenzo-20-crown-6-ether and cesium ions

DOE PAGES

Motokawa, Ryuhei; Kobayashi, Tohru; Endo, Hitoshi; ...

2015-10-26

This study uses small-angle neutron scattering (SANS) to elucidate the coordination structure of the complex of mono-acetyl-substituted dibenzo-20-crown-6-ether (ace-DB20C6) with cesium ions (Cs +). SANS profiles obtained for the complex of ace-DB20C6 and Cs + (ace-DB20C6/Cs) in deuterated dimethyl sulfoxide indicated that Cs + coordination resulted in a more compact structure than the free ace-DB20C6. The data were fitted well with SANS profiles calculated using Debye function for scattering on an absolute scattering intensity scale. For this theoretical calculation of the scattering profiles, the coordination structure proposed based on density functional theory calculation was used. Furthermore, we conclude that themore » SANS analysis experimentally supports the proposed coordination structure of ace-DB20C6/Cs and suggests the following: (1) the complex of ace-DB20C6 and Cs + is formed with an ace-DB20C6/Cs molar ratio of 1/1 and (2) the two benzene rings of ace-DB20C6 fold around Cs + above the center of the crown ether ring of ace-DB20C6.« less

Core-shell structure of Miglyol/poly(D,L-lactide)/Poloxamer nanocapsules studied by small-angle neutron scattering.

PubMed

Rübe, Andrea; Hause, Gerd; Mäder, Karsten; Kohlbrecher, Joachim

2005-10-03

The contrast variation technique in small angle neutron scattering (SANS) was used to investigate the inner structure of nanocapsules on the example of poly(D,L-lactide) (PLA) nanocapsules. The determination of the PLA and Poloxamer shell thickness was the focus of this study. Highest sensitivity on the inner structure of the nanocapsules was obtained when the scattering length density of the solvent was varied between the one of the Miglyol core and the PLA shell. According to the fit data the PLA shell thickness was 9.8 nm. The z-averaged radius determined by SANS experiments correlated well with dynamic light scattering (DLS) results, although DLS values were systematically slightly higher than the ones measured by SANS. This could be explained by taking into account the influence of Poloxamer attached to the nanocapsules surface. For a refined fit model with a second shell consisting of Poloxamer, SANS values and DLS values fitted well with each other. The characterization method presented here is significant because detailed insights into the nanocapsule and the Poloxamer shell were gained for the first time. This method could be used to develop strategies for the optimization of the shell properties concerning controlled release and to study changes in the shell structure during degradation processes.

Small angle neutron scattering study of polyelectrolyte brushes grafted to well-defined gold nanoparticle interfaces.

PubMed

Jia, Haidong; Grillo, Isabelle; Titmuss, Simon

2010-05-18

Small angle neutron scattering (SANS) has been used to study the conformations, and response to added salt, of a polyelectrolyte layer grafted to the interfaces of well-defined gold nanoparticles. The polyelectrolyte layer is prepared at a constant coverage by grafting thiol-functionalized polystyrene (M(w) = 53k) to gold nanoparticles of well-defined interfacial curvature (R(c) = 26.5 nm) followed by a soft-sulfonation of 38% of the segments to sodium polystyrene sulfonate (NaPSS). The SANS profiles can be fit by Fermi-Dirac distributions that are consistent with a Gaussian distribution but are better described by a parabolic distribution plus an exponential tail, particularly in the high salt regime. These distributions are consistent with the predictions and measurements for osmotic and salted brushes at interfaces of low curvature. When the concentration of added salt exceeds the concentration of counterions inside the brush, there is a salt-induced deswelling, but even at the highest salt concentration the brush remains significantly swollen due to a short-ranged excluded volume interaction. This is responsible for the observed resistance to aggregation of these comparatively high concentration polyelectrolyte stabilized gold nanoparticle dispersions even in the presence of a high concentration of added salt.

Small-angle neutron scattering study of specific interaction and coordination structure formed by mono-acetyl-substituted dibenzo-20-crown-6-ether and cesium ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Motokawa, Ryuhei; Kobayashi, Tohru; Endo, Hitoshi

This study uses small-angle neutron scattering (SANS) to elucidate the coordination structure of the complex of mono-acetyl-substituted dibenzo-20-crown-6-ether (ace-DB20C6) with cesium ions (Cs +). SANS profiles obtained for the complex of ace-DB20C6 and Cs + (ace-DB20C6/Cs) in deuterated dimethyl sulfoxide indicated that Cs + coordination resulted in a more compact structure than the free ace-DB20C6. The data were fitted well with SANS profiles calculated using Debye function for scattering on an absolute scattering intensity scale. For this theoretical calculation of the scattering profiles, the coordination structure proposed based on density functional theory calculation was used. Furthermore, we conclude that themore » SANS analysis experimentally supports the proposed coordination structure of ace-DB20C6/Cs and suggests the following: (1) the complex of ace-DB20C6 and Cs + is formed with an ace-DB20C6/Cs molar ratio of 1/1 and (2) the two benzene rings of ace-DB20C6 fold around Cs + above the center of the crown ether ring of ace-DB20C6.« less

Molecular conformation of the full-length tumor suppressor NF2/Merlin—a small angle neutron scattering study

PubMed Central

Khajeh, Jahan Ali; Ju, Jeong Ho; Atchiba, Moussoubaou; Allaire, Marc; Stanley, Christopher; Heller, William T.; Callaway, David J.E.; Bu, Zimei

2014-01-01

Summary The tumor suppressor protein Merlin inhibits cell proliferation upon establishing cell-cell contacts. Because Merlin has high sequence similarity to the Ezrin-Radixin-Moesin (ERM) family of proteins, the structural model of ERM protein autoinhibition and cycling between closed/resting and open/active conformational states is often employed to explain Merlin function. However, recent biochemical studies suggest alternative molecular models of Merlin function. Here, we have determined the low resolution molecular structure and binding activity of Merlin and a Merlin(S518D) mutant that mimics the inactivating phosphorylation at S518 using small angle neutron scattering (SANS) and binding experiments. SANS shows that in solution both Merlin and Merlin(S518D) adopt a closed conformation, but binding experiments indicate that a significant fraction of either Merlin or Merlin(S518D) is capable of binding to the target protein NHERF1. Upon binding to the phosphatidylinositol 4,5-bisphosphate lipid, the wild-type Merlin adopts a more open conformation than in solution, but Merlin(S518D) remains in a closed conformation. This study supports a rheostat model of Merlin in NHERF1 binding, and contributes to resolve a controversy about the molecular conformation and binding activity of Merlin. PMID:24882693

Solution Structure of an Amyloid-Forming Protein During Photoinitiated Hexamer-Dodecamer Transitions Revealed Through Small-Angle Neutron Scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamill,A.; Wang, S.; Lee, Jr., C.

2007-01-01

Shape-reconstruction analysis applied to small angle neutron scattering (SANS) data is used to determine the in vitro conformations of {alpha}-chymotrypsin oligomers that form as a result of partial unfolding with a photoresponsive surfactant. In the presence of the photoactive surfactant under visible light, the native oligomers (dimers or compact hexamers) rearrange into expanded corkscrew-like hexamers. Converting the surfactant to the photopassive form with UV light illumination causes the hexamers to laterally aggregate and intertwine into dodecamers with elongated, twisted conformations containing cross-sectional dimensions similar to amyloid protofilaments. Secondary-structure measurements with FT-IR indicate that this photoinduced hexamer-to-dodecamer association occurs through intermolecularmore » {beta} sheets stabilized with hydrogen bonds, similar to amyloid formation. Traditional structural characterization techniques such as X-ray crystallography and NMR are not easily amenable to the study of these non-native protein conformations; however, SANS is ideally suited to the study of these associated intermediates, providing direct observation of the mechanism of oligomeric formation in an amyloid-forming protein. Combined with photoinitiated hexamer-to-dodecamer associations in the presence of the photoresponsive surfactant, this study could provide unique insight into the amyloidosis disease pathway, as well as novel disease treatment strategies.« less

Protein crowding in solution, frozen and freeze-dried states: small-angle neutron and X-ray scattering study of lysozyme/sorbitol/water systems

NASA Astrophysics Data System (ADS)

Krueger, Susan; Khodadadi, Sheila; Clark, Nicholas; McAuley, Arnold; Cristiglio, Viviana; Theyencheri, Narayanan; Curtis, Joseph; Shalaev, Evgenyi

2015-03-01

For effective preservation, proteins are often stored as frozen solutions or in glassy states using a freeze-drying process. However, aggregation is often observed after freeze-thaw or reconstitution of freeze-dried powder and the stability of the protein is no longer assured. In this study, small-angle neutron and X-ray scattering (SANS and SAXS) have been used to investigate changes in protein-protein interaction distances of a model protein/cryoprotectant system of lysozyme/sorbitol/water, under representative pharmaceutical processing conditions. The results demonstrate the utility of SAXS and SANS methods to monitor protein crowding at different stages of freezing and drying. The SANS measurements of solution samples showed at least one protein interaction peak corresponding to an interaction distance of ~ 90 Å. In the frozen state, two protein interaction peaks were observed by SANS with corresponding interaction distances at 40 Å as well as 90 Å. On the other hand, both SAXS and SANS data for freeze-dried samples showed three peaks, suggesting interaction distances ranging from ~ 15 Å to 170 Å. Possible interpretations of these interaction peaks will be discussed, as well as the role of sorbitol as a cryoprotectant during the freezing and drying process.

Phosphatidylinositol 4,5-Bisphosphate Clusters the Cell Adhesion Molecule CD44 and Assembles a Specific CD44-Ezrin Heterocomplex, as Revealed by Small Angle Neutron Scattering

DOE PAGES

Khajeh, Jahan Ali; Ju, Jeong Ho; Gupta, Yogesh K.; ...

2015-01-08

The cell adhesion molecule CD44 regulates diverse cellular functions, including cell-cell and cell-matrix interaction, cell motility, migration, differentiation, and growth. In cells, CD44 co-localizes with the membrane-cytoskeleton adapter protein Ezrin, which links the CD44 assembled receptor signaling complexes to the cytoskeletal actin and organizes the spatial and temporal localization of signaling events. Here we report that the cytoplasmic tail of CD44 (CD44ct) is largely disordered and adopts an autoinhibited conformation, which prevents CD44ct from binding directly to activated Ezrin in solution. Binding to the signaling lipid phosphatidylinositol 4,5-biphosphlate (PIP2) disrupts autoinhibition in CD44ct, and activates CD44ct to associate with Ezrin.more » Further, using contrast variation small angle neutron scattering, we show that PIP2 mediates the assembly of a specific hetero-tetramer complex of CD44ct with Ezrin. This study reveals a novel autoregulation mechanism in the cytoplasmic tail of CD44 and the role of PIP2 in mediating the assembly of multimeric CD44ct-Ezrin complexes. We hypothesize that polyvalent electrostatic interactions are responsible for the assembly of multimeric PIP2-CD44-Ezrin complexes.« less

Structural and phase transition changes of sodium dodecyl sulfate micellar solution in alcohols probed by small-angle neutron scattering (SANS)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Putra, Edy Giri Rachman; Patriati, Arum; Department of Chemistry, Faculty of Mathematics and Natural Sciences, University of Gadjah Mada, Bulaksumur, Yogyakarta 55281, Indonesia giri@batan.go.id

2015-04-16

Small-angle neutron scattering (SANS) measurements on 0.3M sodium dodecyl sulfate (SDS) micellar solutions have been performed in the presence of n-alcohols, from ethanol to decanol at different alcohol concentrations, 2–10 wt%. The ellipsoid micellar structure which occurred in the 0.3M SDS in aqueous solution with the size range of 30–50 Å has different behavior at various hydrocarbon chain length and concentration of alcohols. At low concentration and short chain-length of alcohols, such as ethanol, propanol, and butanol, the size of micelles reduced and had a spherical-like structure. The opposite effect occurred as medium to long chain alcohols, such as hexanol,more » octanol and decanol was added into the 0.3M SDS micellar solutions. The micelles structure changed to be more elongated in major axis and then crossed the critical phase transition from micellar solution into liquid crystal phase as lamellar structure emerged by further addition of alcohols. The inter-lamellar distances were also depending on the hydrocarbon chain length and concentration of alcohols. In the meantime, the persistent micellar structures occurred in addition of medium chain of n-alcohol, pentanol at all concentrations.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Birkhan, J.; Miorelli, M.; Bacca, S.

The electric dipole strength distribution in 48Ca between 5 and 25 MeV has been determined at RCNP, Osaka, from proton inelastic scattering experiments at forward angles. Combined with photoabsorption data at higher excitation energy, this enables the rst extraction of the electric dipole polarizability D( 48Ca) = 2:07(22) fm 3. Remarkably, the dipole response of 48Ca is found to be very similar to that of 40Ca, consistent with a small neutron skin in 48Ca. The experimental results are in good agreement with ab initio calculations based on chiral e ective eld theory interactions and with state-of-the-art density-functional calculations, implying amore » neutron skin in 48Ca of 0:14 - 0:20 fm.« less

Strain heterogeneity in sheared colloids revealed by neutron scattering

DOE PAGES

Chen, Kevin; Wu, Bin; He, Lilin; ...

2018-02-07

Recent computational and theoretical studies have shown that the deformation of colloidal suspensions under a steady shear is highly heterogeneous at the particle level and demonstrate a critical influence on the macroscopic deformation behavior. Despite its relevance to a wide variety of industrial applications of colloidal suspensions, scattering studies focusing on addressing the heterogeneity of the non-equilibrium colloidal structure are scarce thus far. Here in this paper, we report the first experimental result using small-angle neutron scattering. From the evolution of strain heterogeneity, we conclude that the shear-induced deformation transforms from nearly affine behavior at low shear rates, to plasticmore » rearrangements when the shear rate is high.« less

Pulsed-neutron monochromator

DOEpatents

Mook, H.A. Jr.

1984-01-01

In one aspect, the invention is an improved pulsed-neutron monochromator of the vibrated-crystal type. The monochromator is designed to provide neutron pulses which are characterized both by short duration and high density. A row of neutron-reflecting crystals is disposed in a neutron beam to reflect neutrons onto a common target. The crystals in the row define progressively larger neutron-scattering angles and are vibrated sequentially in descending order with respect to the size of their scattering angles, thus generating neutron pulses which arrive simultaneously at the target. Transducers are coupled to one end of the crystals to vibrate them in an essentially non-resonant mode. The transducers propagate transverse waves in the crystal which progress longitudinally therein. The waves are absorbed at the undriven ends of the crystals by damping material mounted thereon. In another aspect, the invention is a method for generating neutron pulses characterized by high intensity and short duration.

Pulsed-neutron monochromator

DOEpatents

Mook, Jr., Herbert A.

1985-01-01

In one aspect, the invention is an improved pulsed-neutron monochromator of the vibrated-crystal type. The monochromator is designed to provide neutron pulses which are characterized both by short duration and high density. A row of neutron-reflecting crystals is disposed in a neutron beam to reflect neutrons onto a common target. The crystals in the row define progressively larger neutron-scattering angles and are vibrated sequentially in descending order with respect to the size of their scattering angles, thus generating neutron pulses which arrive simultaneously at the target. Transducers are coupled to one end of the crystals to vibrate them in an essentially non-resonant mode. The transducers propagate transverse waves in the crystal which progress longitudinally therein. The wave are absorbed at the undriven ends of the crystals by damping material mounted thereon. In another aspect, the invention is a method for generating neutron pulses characterized by high intensity and short duration.

Two neutron correlations in photo-fission

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dale, D. S.; Kosinov, O.; Forest, T.

2016-01-01

A large body of experimental work has established the strong kinematical correlation between fission fragments and fission neutrons. Here, we report on the progress of investigations of the potential for strong two neutron correlations arising from the nearly back-to-back nature of the two fission fragments that emit these neutrons in the photo-fission process. In initial measurements, a pulsed electron linear accelerator was used to generate bremsstrahlung photons that impinged upon an actinide target, and the energy and opening angle distributions of coincident neutrons were measured using a large acceptance neutron detector array. A planned comprehensive set of measurements of twomore » neutron correlations in the photo-fission of actinides is expected to shed light on several fundamental aspects of the fission process including the multiplicity distributions associated with the light and heavy fission fragments, the nuclear temperatures of the fission fragments, and the mass distribution of the fission fragments as a function of energy released. In addition to these measurements providing important nuclear data, the unique kinematics of fission and the resulting two neutron correlations have the potential to be the basis for a new tool to detect fissionable materials. A key technical challenge of this program arises from the need to perform coincidence measurements with a low duty factor, pulsed electron accelerator. This has motivated the construction of a large acceptance neutron detector array, and the development of data analysis techniques to directly measure uncorrelated two neutron backgrounds.« less

Quantitative NDA measurements of advanced reprocessing product materials containing uranium, neptunium, plutonium, and americium

NASA Astrophysics Data System (ADS)

Goddard, Braden

The ability of inspection agencies and facility operators to measure powders containing several actinides is increasingly necessary as new reprocessing techniques and fuel forms are being developed. These powders are difficult to measure with nondestructive assay (NDA) techniques because neutrons emitted from induced and spontaneous fission of different nuclides are very similar. A neutron multiplicity technique based on first principle methods was developed to measure these powders by exploiting isotope-specific nuclear properties, such as the energy-dependent fission cross sections and the neutron induced fission neutron multiplicity. This technique was tested through extensive simulations using the Monte Carlo N-Particle eXtended (MCNPX) code and by one measurement campaign using the Active Well Coincidence Counter (AWCC) and two measurement campaigns using the Epithermal Neutron Multiplicity Counter (ENMC) with various (alpha,n) sources and actinide materials. Four potential applications of this first principle technique have been identified: (1) quantitative measurement of uranium, neptunium, plutonium, and americium materials; (2) quantitative measurement of mixed oxide (MOX) materials; (3) quantitative measurement of uranium materials; and (4) weapons verification in arms control agreements. This technique still has several challenges which need to be overcome, the largest of these being the challenge of having high-precision active and passive measurements to produce results with acceptably small uncertainties.

?-BiPd: a clean noncentrosymmetric superconductor

NASA Astrophysics Data System (ADS)

Ramakrishnan, Srinivasan; Joshi, Bhanu; Thamizhavel, A.

2017-12-01

We present a comprehensive review of the normal and superconducting state properties of a high-quality single crystal of monoclinic BiPd (?-BiPd, space group ?). The superconductivity of this crystal below 3.8 K is established by measuring its properties using bulk as well as spectroscopic techniques. BiPd is one of the cleanest noncentrosymmetric superconductors that display superconductivity with multiple energy gaps. Evidence of multiple energy gaps was found in heat capacity, point contact (PC) spectroscopy, penetration depth, muon spin rotation, small angle neutron scattering and NMR/NQR measurements. Moreover, Muon spin rotation measurements also suggest strong field dependence of the penetration depth of this superconductor. Unusual superconducting properties due to possible s and p wave mixing are shown by the observation of Andreev bound state in PC measurements as well as the suppressed coherence peak in the temperature dependence of the spin-lattice relaxation in the NQR measurements. This surmise is at variance with the recent STM measurements (different crystal). The observed unusual properties and multiband superconductivity are extremely sensitive to disorder in BiPd. Finally, there is a possibility of tuning the electron correlations by selective substitution in BiPd, thus making it an important system for further investigations.

Recent skyshine calculations at Jefferson Lab

DOE Office of Scientific and Technical Information (OSTI.GOV)

Degtyarenko, P.

1997-12-01

New calculations of the skyshine dose distribution of neutrons and secondary photons have been performed at Jefferson Lab using the Monte Carlo method. The dose dependence on neutron energy, distance to the neutron source, polar angle of a source neutron, and azimuthal angle between the observation point and the momentum direction of a source neutron have been studied. The azimuthally asymmetric term in the skyshine dose distribution is shown to be important in the dose calculations around high-energy accelerator facilities. A parameterization formula and corresponding computer code have been developed which can be used for detailed calculations of the skyshinemore » dose maps.« less

New compact neutron supermirror transmission polarizer

NASA Astrophysics Data System (ADS)

Syromyatnikov, V. G.; Pusenkov, V. M.

2017-06-01

A new compact neutron supermirror transmission polarizer is suggested. The polarizer consists of a set of plates transparent to neutrons placed in the magnet gap. There are no air gaps between the plates. Polarizing supermirror coating without absorbing underlayer is deposited on the polished surfaces of the plates. Magnetic and nonmagnetic layers of the supermirror coating as well as the material of the plates have nearly equal neutron-optical potentials for spin-down neutrons. There is a considerable difference between neutron-optical potentials of layers in the supermirror structure for spin-up neutrons. As a result, spin-up neutrons reflect from the supermirror coating and deviate from their initial trajectories whereas spin-down neutrons do not practically reflect from the coating and, consequently, do not deviate from their initial trajectories. Thus, spin-down neutrons dominate near the axis of distribution of intensity on the angle for the beam transmitted through this polarizer, i.e., the beam is substantially polarized. Application is discussed of this polarizer in a research facility for small angle scattering of monochromatic neutrons with wavelengths λ = 4.5÷20 Å. The polarizing cross section of the beam of this facility is 30×30 mm2. Calculated parameters are presented of a polarizer on silicon plates with supermirror CoFe/TiZr (m = 2) coating. The suggested polarizer is compared with solid state bender, S-bender and widely known transmission neutron polarizer V- cavity in the same spectral range. Two polarizers are used to cover the wavelength range λ = 4.5 ÷20 Å: the first one whose length is 50 мм covers the range λ = 4.5 ÷10 Å and the second one whose length is 21.2 мм covers the range λ = 10 ÷20 Å. The length of each of these polarizers is more than 30 times smaller than that of V-cavity! On the other hand, basic parameters of the proposed polarizer, polarization of the beam falling on the sample P and transmission coefficient T- of the main spin component, exceed those of V-cavity. T- = 0.8 - 0.9 for both polarizers and for each wavelength range. Polarization P is very high. P is better than -0.99 for wavelength range λ = 12.5 ÷ 20 Å at the beam divergence of 24 mrad.

Investigating Structure and Dynamics of Proteins in Amorphous Phases Using Neutron Scattering.

PubMed

Castellanos, Maria Monica; McAuley, Arnold; Curtis, Joseph E

2017-01-01

In order to increase shelf life and minimize aggregation during storage, many biotherapeutic drugs are formulated and stored as either frozen solutions or lyophilized powders. However, characterizing amorphous solids can be challenging with the commonly available set of biophysical measurements used for proteins in liquid solutions. Therefore, some questions remain regarding the structure of the active pharmaceutical ingredient during freezing and drying of the drug product and the molecular role of excipients. Neutron scattering is a powerful technique to study structure and dynamics of a variety of systems in both solid and liquid phases. Moreover, neutron scattering experiments can generally be correlated with theory and molecular simulations to analyze experimental data. In this article, we focus on the use of neutron techniques to address problems of biotechnological interest. We describe the use of small-angle neutron scattering to study the solution structure of biological molecules and the packing arrangement in amorphous phases, that is, frozen glasses and freeze-dried protein powders. In addition, we discuss the use of neutron spectroscopy to measure the dynamics of glassy systems at different time and length scales. Overall, we expect that the present article will guide and prompt the use of neutron scattering to provide unique insights on many of the outstanding questions in biotechnology.

Technical Report: Understanding Functional Lyotropic Liquid Crystal Network Phase Self-Assembly and the Properties of Nanoconfined Water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mahanthappa, Mahesh K; Yethiraj, Arun

Through the synergistic interplay of molecular dynamics (MD) simulations, chemical synthesis, and materials characterization by X-ray and neutron scattering techniques, this project investigated the phase behaviors of new classes of aqueous lyotropic liquid crystals (LLCs) and the properties of water nanoconfined within their pores. A portion of our studies focused on the synthesis of new classes of alkylsulfonic acid and alkylphosphonate amphiphiles, which were shown to undergo water-induced self-assembly to form a wide variety of nanostructured morphologies with unusually high degrees of long-range translational order observed by small- angle X-ray scattering (SAXS). Sample LLC morphologies that were observed include themore » lamellar (L!), tricontinuous double gyroid (G), hexagonally-packed cylinders (H), and low symmetry discontinuous micellar (I) Frank-Kasper phases. Since the G and H phases are the most promising for the development of selective ion transporting membranes for energy applications, we sought the characterize the structure and dynamics of water confined within the sub-3 nm pores of these LLCs using wide-angle neutron diffraction (WAND) and quasielastic neutron scattering (QENS) experiments performed at the Spallation Neutron Source at Oak Ridge National Laboratory. Using molecular dynamics (MD) simulations, we validated models for analyzing this QENS data to obtain water self-diffusion coefficients in LLC G and H phases of carboxylate and sulfonate surfactant LLCs as a function of the identities of their charge compensating counterions.« less

Multiple Approaches to Characterizing Nano-Pore Structure of Barnett Shale

NASA Astrophysics Data System (ADS)

Hu, Q.; Gao, Z.; Ewing, R. P.; Dultz, S.; Kaufmann, J.; Hamamoto, S.; Webber, B.; Ding, M.

2013-12-01

Microscopic characteristics of porous media - pore shape, pore-size distribution, and pore connectivity - control fluid flow and mass transport. This presentation discusses various approaches to investigating nano-pore structure of Barnett shale, with its implications in gas production behavior. The innovative approaches include imbibition, tracer diffusion, edge-accessible porosity, porosimetry (mercury intrusion porosimetry, nitrogen and water vapor sorption isotherms, and nuclear magnetic resonance cyroporometry), and imaging (Wood's metal impregnation followed with laser ablation-inductively coupled plasma-mass spectrometry, focused ion beam/scanning electron microscopy, and small angle neutron scattering). Results show that the shale pores are predominantly in the nm size range, with measured median pore-throat diameters about 5 nm. But small pore size is not the major contributor to low gas recovery; rather, the low mass diffusivity appears to be caused by low pore connectivity of Barnett shale. Chemical diffusion in sparsely-connected pore spaces is not well described by classical Fickian behavior; anomalous behavior is suggested by percolation theory, and confirmed by results of imbibition and diffusion tests. Our evolving complementary approaches, with their several advantages and disadvantages, provide a rich toolbox for tackling the nano-pore structure characteristics of shales and other natural rocks.

A small-angle neutron scattering study of the kinetics of phase separation in a supersaturated Ni-12.5 at. pct Si alloy

NASA Astrophysics Data System (ADS)

Polat, S.; Chen, Haydn; Epperson, J. E.

1989-04-01

The kinetic behavior of precipitation in a supersaturated Ni-12.5 at. pct Si alloy single crystal has been studied by the small-angle neutron scattering (SANS) technique to supplement earlier transmission electron microscopy (TEM) and wide-angle X-ray diffraction (XRD) work. The SANS measurements performed at room temperature on quenched specimens subjected to isothermal anneals at 400, 450, 505, and 550 °C for various amounts of time have revealed the presence of an interference peak in the scattering function. The particle size, determined according to the Guinier approximation, is found to grow in accordance with the diffusion controlled model put forth by Lifshitz and Slyozov, and independently by Wagner. The activation energy for solute diffusion is determined using the rate constants governing the growth of particle size and the variation of the mean interparticle distance. Results are in agreement with the values given in the literature. Transition from an earlier growth stage has been observed, and enhanced diffusion is noted at temperatures below 505 °C; both observations are consistent with the previous X-ray results. The dynamical scaling law appears to be followed by the data obtained in the coarsening stage. A disruption of scaling occurs at the point when the particle growth changes from a parabolic rate behavior to a cubic coarsening rate. Dynamical scaling offers the potential for projecting the service lifetimes for components from experimental measurements carried out over a much shorter time interval. Discrepancies in the size parameters determined by different techniques are discussed.

Magnetic topology of Co-based inverse opal-like structures

NASA Astrophysics Data System (ADS)

Grigoryeva, N. A.; Mistonov, A. A.; Napolskii, K. S.; Sapoletova, N. A.; Eliseev, A. A.; Bouwman, W.; Byelov, D. V.; Petukhov, A. V.; Chernyshov, D. Yu.; Eckerlebe, H.; Vasilieva, A. V.; Grigoriev, S. V.

2011-08-01

The magnetic and structural properties of a cobalt inverse opal-like crystal have been studied by a combination of complementary techniques ranging from polarized neutron scattering and superconducting quantum interference device (SQUID) magnetometry to x-ray diffraction. Microradian small-angle x-ray diffraction shows that the inverse opal-like structure (OLS) synthesized by the electrochemical method fully duplicates the three-dimensional net of voids of the template artificial opal. The inverse OLS has a face-centered cubic (fcc) structure with a lattice constant of 640±10 nm and with a clear tendency to a random hexagonal close-packed structure along the [111] axes. Wide-angle x-ray powder diffraction shows that the atomic cobalt structure is described by coexistence of 95% hexagonal close-packed and 5% fcc phases. The SQUID measurements demonstrate that the inverse OLS film possesses easy-plane magnetization geometry with a coercive field of 14.0 ± 0.5 mT at room temperature. The detailed picture of the transformation of the magnetic structure under an in-plane applied field was detected with the help of small-angle diffraction of polarized neutrons. In the demagnetized state the magnetic system consists of randomly oriented magnetic domains. A complex magnetic structure appears upon application of the magnetic field, with nonhomogeneous distribution of magnetization density within the unit element of the OLS. This distribution is determined by the combined effect of the easy-plane geometry of the film and the crystallographic geometry of the opal-like structure with respect to the applied field direction.

Ordered arrays of Ni magnetic nanowires: Synthesis and investigation

NASA Astrophysics Data System (ADS)

Napolskii, K. S.; Eliseev, A. A.; Yesin, N. V.; Lukashin, A. V.; Tretyakov, Yu. D.; Grigorieva, N. A.; Grigoriev, S. V.; Eckerlebe, H.

2007-03-01

The present study is focused on the synthesis and investigation of anodic aluminum oxide (AAO) films and magnetic nanocomposites Ni/AAO obtained by Ni electrodeposition into porous matrix. AAO membranes and magnetic nanocomposites were investigated by HRSEM, EDX microanalysis, XRD, nitrogen capillary adsorption method, SQUID magnetometry, and polarized small-angle neutron scattering (SANS). The influence of synthesis conditions and form factor effect on the magnetic properties of nanowire arrays is reported.

Direct observation of the flux-line vortex glass phase in a type II superconductor.

PubMed

Divakar, U; Drew, A J; Lee, S L; Gilardi, R; Mesot, J; Ogrin, F Y; Charalambous, D; Forgan, E M; Menon, G I; Momono, N; Oda, M; Dewhurst, C D; Baines, C

2004-06-11

The order of the vortex state in La1.9Sr0.1CuO4 is probed using muon-spin rotation and small-angle neutron scattering. A transition from a Bragg glass to a vortex glass is observed, where the latter is composed of disordered vortex lines. In the vicinity of the transition the microscopic behavior reflects a delicate interplay of thermally induced and pinning-induced disorder.

Evolution of Microstructure in a Nickel-based Superalloy as a Function of Ageing Time

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Wei-Ren; Smith, Gregory Scott; Porcar, L.

2011-01-01

An experimental investigation, combining synchrotron X-ray powder diffraction, small-angle neutron-scattering, and transmission electron microscopy, has been undertaken to study the microstructure of nanoprecipitates in a nickel-based superalloy. Upon increasing the ageing time during a heat-treatment process, the average size of the precipitates first decreases before changing to a monotonical growth stage. Possible reasons for this observed structural evolution, which is predicted thermodynamically, are suggested.

Using Neutron Spin Echo Resolved Grazing Incidence Scattering to Investigate Organic Solar Cell Materials

PubMed Central

Parnell, Andrew J.; Hobson, Adam; Dalgliesh, Robert M.; Jones, Richard A. L.; Dunbar, Alan D. F.

2014-01-01

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped crystallites. Neutrons are passed through two well defined regions of magnetic field; one before and one after the sample. The two magnetic field regions have opposite polarity and are tuned such that neutrons travelling through both regions, without being perturbed, will undergo the same number of precessions in opposing directions. In this case the neutron precession in the second arm is said to "echo" the first, and the original polarization of the beam is preserved. If the neutron interacts with a sample and scatters elastically the path through the second arm is not the same as the first and the original polarization is not recovered. Depolarization of the neutron beam is a highly sensitive probe at very small angles (<50 μrad) but still allows a high intensity, divergent beam to be used. The decrease in polarization of the beam reflected from the sample as compared to that from the reference sample can be directly related to structure within the sample. In comparison to scattering observed in neutron reflection measurements the SERGIS signals are often weak and are unlikely to be observed if the in-plane structures within the sample under investigation are dilute, disordered, small in size and polydisperse or the neutron scattering contrast is low. Therefore, good results will most likely be obtained using the SERGIS technique if the sample being measured consist of thin films on a flat substrate and contain scattering features that contains a high density of moderately sized features (30 nm to 5 µm) which scatter neutrons strongly or the features are arranged on a lattice. An advantage of the SERGIS technique is that it can probe structures in the plane of the sample. PMID:24457355

Report detailing comparative analysis of results from high flux isotope reactor and national institute of standards technology small-angle neutron scattering experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sokolov, Mikhail A.; Littrell, Ken; Wells, Peter

The major issues regarding irradiation effects are discussed in [1-3] and have also been discussed in previous progress and milestone reports. As noted previously, of the many significant issues discussed, the issue considered to have the most impact on the current regulatory process is that associated with effects of neutron irradiation on RPV steels at high fluence, for long irradiation times, and as affected by neutron flux. It is clear that embrittlement of RPV steels is a critical issue that may limit LWR plant life extension. The primary objective of the LWRSP RPV task is to develop robust predictions ofmore » transition temperature shifts (TTS) at high fluence ( t) to at least 1020 n/cm 2 (>1 MeV) pertinent to plant operation of some pressurized water reactors (PWR) for 80 full power years. Correlations between the high flux test reactor results and low flux surveillance specimens must be established for proper RPV embrittlement predictions of the current nuclear power fleet. Additionally, a complete understanding of defect evolution for high nickel RPV steels is needed to characterize the embrittlement potential of Mn-Ni-enriched precipitates (MNPs), particularly for the high fluence regime. While understanding of copper-enriched precipitates (CRPs) have been fully developed, the recent discovery and experimental verification [4] of late blooming MNPs with little to no copper for nucleation has stimulated research efforts to understand the evolution of these phases. New and existing databases will be combined to support developing physically based models of TTS for high fluence-low flux ( < 10 11n/cm 2-s) conditions, beyond the existing surveillance database, to neutron fluences of at least 1 1020 n/cm2 (>1 MeV). Moreover, large number of various RPV materials have been irradiated in ATR-2 experiment and will be jointly studied by University of California Santa Barbara (UCSB) and ORNL to address majority of microstructural characteristics discussed above, see Ref. [5] and [6] for details. UCSB has performed a large number of SANS experiments in the past at the National Institute of Standards and Technology (NIST) Center for Neutron Research (NCNR). These data are taken from RPV steels irradiated in a wide range of flux-fluence space and will be very useful in comparing to the upcoming UCSB ATR-2 irradiation characterization since most of the SANS experiments with ATR-2 materials will be performed at ORNL High Flux Isotope Reactor (HFIR). However in the previous report [7], some discrepancies were observed between HFIR and NCNR generated data. One of the hypotheses was that there was some kind of extra scattering occurring off the sample holders that results in the HFIR curves falling above the NCNR curves. To test this hypothesis, UCSB provided thermally aged samples that have been previously run at NCNR to ORNL for testing at HFIR while ORNL performed some improvements to experimental set up at HFIR. This report provides the status for the Level 3 Milestone (M3LW-15OR0402013), Complete report detailing comparative analysis of results from High Flux Isotope Reactor and National Institute of Standards and Technology small-angle neutron scattering experiments. This milestone is associated with small-angle neutron scattering characterization at the High Flux Isotope Reactor of various model alloys that had been previously characterized at NCNR by UCSB.« less

Focusing adaptive-optics for neutron spectroscopy at extreme conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simeoni, G. G., E-mail: ggsimeoni@outlook.com; Physics Department E13, Technical University of Munich, D-85748 Garching; Valicu, R. G.

2015-12-14

Neutron Spectroscopy employing extreme-conditions sample environments is nowadays a crucial tool for the understanding of fundamental scientific questions as well as for the investigation of materials and chemical-physical properties. For all these kinds of studies, an increased neutron flux over a small sample area is needed. The prototype of a focusing neutron guide component, developed and produced completely at the neutron source FRM II in Garching (Germany), has been installed at the time-of-flight (TOF) disc-chopper neutron spectrometer TOFTOF and came into routine-operation. The design is based on the compressed Archimedes' mirror concept for finite-size divergent sources. It represents a uniquemore » device combining the supermirror technology with Adaptive Optics, suitable for broad-bandwidth thermal-cold TOF neutron spectroscopy (here optimized for 1.4–10 Å). It is able to squeeze the beam cross section down to a square centimeter, with a more than doubled signal-to-background ratio, increased efficiency at high scattering angles, and improved symmetry of the elastic resolution function. We present a comparison between the simulated and measured beam cross sections, as well as the performance of the instrument within real experiments. This work intends to show the unprecedented opportunities achievable at already existing instruments, along with useful guidelines for the design and construction of next-generation neutron spectrometers.« less

16O(n,α) cross section investigation using LENZ instrument at LANSCE

NASA Astrophysics Data System (ADS)

Lee, H. Y.; Mosby, S.; Haight, R. C.; White, M. C.

2016-06-01

Importance of studying the 16O(n,α) reaction is motivated by multiple nuclear applications. The Los Alamos Neutron Science Center (LANSCE) produces a white neutron spectrum ranging from thermal to several hundreds of MeV energies. We have recently developed the LENZ (Low Energy NZ-neutron induced charged particle detection) capability to measure high-precision (n,α) cross sections. In order to provide more reliable data, we have enhanced solid angle coverage, and improved signal-to-noise ratios and time-of-flight resolution by implementing digitizer waveform analysis. The LENZ was commissioned by studying the 59Co(n,α) reaction with neutron beams in early 2015. For the 16O(n,α) reaction, we investigate solid oxygen targets and make a relative measurement to a better known cross section, such as the 6Li(n,α) reaction in order to further reduce systematic uncertainty. We will discuss the progress of the 16O(n,α) study at LANSCE and the outlook for improving Hauser-Feshbah prediction on (n,p) reaction cross sections.

Lipid based drug delivery systems: Kinetics by SANS

NASA Astrophysics Data System (ADS)

Uhríková, D.; Teixeira, J.; Hubčík, L.; Búcsi, A.; Kondela, T.; Murugova, T.; Ivankov, O. I.

2017-05-01

N,N-dimethyldodecylamine-N-oxide (C12NO) is a surfactant that may exist either in a neutral or protonated form depending on the pH of aqueous solutions. Using small angle X-ray diffraction (SAXD) we demonstrate structural responsivity of C12NO/dioleoylphospha-tidylethanolamine (DOPE)/DNA complexes designed as pH sensitive gene delivery vectors. Small angle neutron scattering (SANS) was employed to follow kinetics of C12NO protonization and DNA binding into C12NO/DOPE/DNA complexes in solution of 150 mM NaCl at acidic condition. SANS data analyzed using paracrystal lamellar model show the formation of complexes with stacking up to ∼32 bilayers, spacing ∼ 62 Å, and lipid bilayer thickness ∼37 Å in 3 minutes after changing pH from 7 to 4. Subsequent structural reorganization of the complexes was observed along 90 minutes of SANS mesurements.

Small-angle scattering study of Aspergillus awamori glycoprotein glucoamylase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmidt, A. E., E-mail: schmidt@omrb.pnpi.spb.ru; Shvetsov, A. V.; Kuklin, A. I.

2016-01-15

Glucoamylase from fungus Aspergillus awamori is glycoside hydrolase that catalyzes the hydrolysis of α-1,4- and α-1,6-glucosidic bonds in glucose polymers and oligomers. This glycoprotein consists of a catalytic domain and a starch-binding domain connected by an O-glycosylated polypeptide chain. The conformation of the linker, the relative arrangement of the domains, and the structure of the full-length enzyme are unknown. The structure of the recombinant glucoamylase GA1 was studied by molecular modelling and small-angle neutron scattering (SANS) methods. The experimental SANS data provide evidence that glucoamylase exists as a monomer in solution and contains a glycoside component, which makes a substantialmore » contribution to the scattering. The model of full-length glucoamylase, which was calculated without taking into account the effect of glycosylation, is consistent with the experimental data and has a radius of gyration of 33.4 ± 0.6 Å.« less

SMALL-ANGLE NEUTRON SCATTERING CHARACTERIZATION OF THE STRUCTURE OF NANOPOROUS CARBONS FOR ENERGY-RELATED APPLICATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Lilin; Mavila Chathoth, Suresh; Melnichenko, Yuri B

2011-01-01

We used small-angle neutron scattering (SANS) and neutron contrast variation to study the structure of four nanoporouscarbons prepared by thermo-chemical etching of titanium carbide TiC in chlorine at 300, 400, 600, and 800 C with pore diameters ranging between -4 and -11 {angstrom}. SANS patterns were obtained from dry samples and samples saturated with deuterium oxide (D{sub 2}O) in order to delineate origin of the power law scattering in the low Q domain as well as to evaluate pore accessibility for D{sub 2}O molecules. SANS cross section of all samples was fitted to Debye-Anderson-Brumberger (DAB), DAB-Kirste-Porod models as well asmore » to the Guinier and modified Guinier formulae for cylindrical objects, which allowed for evaluating the radii of gyration as well as the radii and lengths of the pores under cylindrical shape approximation. SANS data from D{sub 2}O-saturated samples indicate that strong upturn in the low Q limit usually observed in the scattering patterns from microporous carbon powders is due to the scattering from outer surface of the powder particles. Micropores are only partially filled with D{sub 2}O molecules due to geometrical constraints and or partial hydrophobicity of the carbon matrix. Structural parameters of the dry carbons obtained using SANS are compared with the results of the gas sorption measurements and the values agree for carbide-derived carbons (CDCs) obtained at high chlorination temperatures (>600 C). For lower chlorination temperatures, pore radii obtained from gas sorption overestimate the actual pore size as calculated from SANS for two reasons: inaccessible small pores are present and the model-dependent fitting based on density functional theory models assumes non-spherical pores, whereas SANS clearly indicates that the pore shape in microporous CDC obtained at low chlorination temperatures is nearly spherical.« less

Corrections for the geometric distortion of the tube detectors on SANS instruments at ORNL

DOE PAGES

He, Lilin; Do, Changwoo; Qian, Shuo; ...

2014-11-25

Small-angle neutron scattering instruments at the Oak Ridge National Laboratory's High Flux Isotope Reactor were upgraded in area detectors from the large, single volume crossed-wire detectors originally installed to staggered arrays of linear position-sensitive detectors (LPSDs). The specific geometry of the LPSD array requires that approaches to data reduction traditionally employed be modified. Here, two methods for correcting the geometric distortion produced by the LPSD array are presented and compared. The first method applies a correction derived from a detector sensitivity measurement performed using the same configuration as the samples are measured. In the second method, a solid angle correctionmore » is derived that can be applied to data collected in any instrument configuration during the data reduction process in conjunction with a detector sensitivity measurement collected at a sufficiently long camera length where the geometric distortions are negligible. Furthermore, both methods produce consistent results and yield a maximum deviation of corrected data from isotropic scattering samples of less than 5% for scattering angles up to a maximum of 35°. The results are broadly applicable to any SANS instrument employing LPSD array detectors, which will be increasingly common as instruments having higher incident flux are constructed at various neutron scattering facilities around the world.« less

Multiple image x-radiography for functional lung imaging

NASA Astrophysics Data System (ADS)

Aulakh, G. K.; Mann, A.; Belev, G.; Wiebe, S.; Kuebler, W. M.; Singh, B.; Chapman, D.

2018-01-01

Detection and visualization of lung tissue structures is impaired by predominance of air. However, by using synchrotron x-rays, refraction of x-rays at the interface of tissue and air can be utilized to generate contrast which may in turn enable quantification of lung optical properties. We utilized multiple image radiography, a variant of diffraction enhanced imaging, at the Canadian light source to quantify changes in unique x-ray optical properties of lungs, namely attenuation, refraction and ultra small-angle scatter (USAXS or width) contrast ratios as a function of lung orientation in free-breathing or respiratory-gated mice before and after intra-nasal bacterial endotoxin (lipopolysaccharide) instillation. The lung ultra small-angle scatter and attenuation contrast ratios were significantly higher 9 h post lipopolysaccharide instillation compared to saline treatment whereas the refraction contrast decreased in magnitude. In ventilated mice, end-expiratory pressures result in an increase in ultra small-angle scatter contrast ratio when compared to end-inspiratory pressures. There were no detectable changes in lung attenuation or refraction contrast ratio with change in lung pressure alone. In effect, multiple image radiography can be applied towards following optical properties of lung air-tissue barrier over time during pathologies such as acute lung injury.

Neutron energy spectra from the laser-induced Dd,n3He reaction.

PubMed

Hilscher, D; Berndt, O; Enke, M; Jahnke, U; Nickles, P V; Ruhl, H; Sandner, W

2001-07-01

Detailed neutron energy spectra were measured for the D(d,n)3He reaction induced in solid (CD2)(n) targets by irradiation with 50-fs 2 x 10(18) W/cm(2) light pulses from a 10-TW Ti:Sapphire laser. The neutrons were observed at two angles 5 degrees and 112 degrees relative to the incident laser beam. The neutron spectra at the two angles are characterized by peaks with large widths of about 700 keV full width at half maximum and a shift of 300 keV between them. Neutron energies of up to about 4 MeV were observed indicating that deuterons are accelerated up to an energy of 1 MeV in the laser produced plasma. Simulation calculations can describe qualitatively the neutron spectra by assuming isotropic deuteron acceleration and a reduction of the reaction probability by a factor of 1/3 for deuterons emitted from the front of the target. These calculations indicate in particular that it is necessary to assume deuterons moving both into and out of the front of the target in order to describe the neutron energy spectra at the two angles. The highest recorded mean neutron yield was about 10(4) neutrons per pulse. The neutron yield increases with the number of electrons emitted from the front of the target and with the intensity of the prompt gamma flash induced by the bremsstrahlung of energetic electrons.

On the angular and energy distribution of solar neutrons generated in P-P reactions

NASA Technical Reports Server (NTRS)

Efimov, Y. E.; Kocharov, G. E.

1985-01-01

The problem of high energy neutron generation in P-P reactions in the solar atmosphere is reconsidered. It is shown that the angular distribution of emitted neutrons is anisotropic and the energy spectrum of neutrons depends on the angle of neutron emission.

Enhanced thermal conductivity oxide nuclear fuels by co-sintering with BeO: II. Fuel performance and neutronics

NASA Astrophysics Data System (ADS)

McCoy, Kevin; Mays, Claude

2008-04-01

The fuel rod performance and neutronics of enhanced thermal conductivity oxide (ECO) nuclear fuel with BeO have been compared to those of standard UO 2 fuel. The standards of comparison were that the ECO fuel should have the same infinite neutron-multiplication factor kinf at end of life and provide the same energy extraction per fuel assembly over its lifetime. The BeO displaces some uranium, so equivalence with standard UO 2 fuel was obtained by increasing the burnup and slightly increasing the enrichment. The COPERNIC fuel rod performance code was adapted to account for the effect of BeO on thermal properties. The materials considered were standard UO 2, UO 2 with 4.0 vol.% BeO, and UO 2 with 9.6 vol.% BeO. The smaller amount of BeO was assumed to provide increases in thermal conductivity of 0, 5, or 10%, whereas the larger amount was assumed to provide an increase of 50%. A significant improvement in performance was seen, as evidenced by reduced temperatures, internal rod pressures, and fission gas release, even with modest (5-10%) increases in thermal conductivity. The benefits increased monotonically with increasing thermal conductivity. Improvements in LOCA initialization performance were also seen. A neutronic calculation considered a transition from standard UO 2 fuel to ECO fuel. The calculation indicated that only a small increase in enrichment is required to maintain the kinf at end of life. The smallness of the change was attributed to the neutron-multiplication reaction of Be with fast neutrons and the moderating effect of BeO. Adoption of ECO fuel was predicted to provide a net reduction in uranium cost. Requirements for industrial hygiene were found to be comparable to those for processing of UO 2.

Characterizing Scintillator Response with Neutron Time-of-Flight

NASA Astrophysics Data System (ADS)

Palmisano, Kevin; Visca, Hannah; Caves, Louis; Wilkinson, Corey; McClow, Hannah; Padalino, Stephen; Forrest, Chad; Katz, Joe; Sangster, Craig; Regan, Sean

2017-10-01

Neutron scintillator diagnostics for ICF can be characterized using the neutron time-of-flight (nTOF) line on Geneseo's 1.7 MV Tandem Pelletron Accelerator. Neutron signals can be differentiated from gamma signals by employing a coincidence method called the associated particle technique (APT). In this measurement, a 2.1 MeV beam of deuterons incident on a deuterated polyethylene target produces neutrons via the d(d,n)3He reaction. A BC-412 plastic scintillator, placed at a scattering angle of 152º, detects 1.76 MeV neutrons in coincidence with the 2.56 MeV 3He ions at an associated angle of 10º. The APT is used to identify the 1.76 MeV neutron while the nTOF line determines its energy. By gating only mono-energetic neutrons, the instrument response function of the scintillator can be determined free from background scattered neutrons and gamma rays. Funded in part by a Grant from the DOE, through the Laboratory for Laser Energetics.

Spin disorder in maghemite nanoparticles investigated using polarized neutrons and nuclear resonant scattering

NASA Astrophysics Data System (ADS)

Herlitschke, M.; Disch, S.; Sergueev, I.; Schlage, K.; Wetterskog, E.; Bergström, L.; Hermann, R. P.

2016-04-01

The manuscript reports the investigation of spin disorder in maghemite nanoparticles of different shape by a combination of polarized small-angle neutron scattering (SANSPOL) and nuclear forward scattering (NFS) techniques. Both methods are sensitive to magnetization on the nanoscale. SANSPOL allows for investigation of the particle morphology and spatial magnetization distribution and NFS extends this nanoscale information to the atomic scale, namely the orientation of the hyperfine field experienced by the iron nuclei. The studied nanospheres and nanocubes with diameters of 7.4 nm and 10.6 nm, respectively, exhibit a significant spin disorder. This effect leads to a reduction of the magnetization to 44% and 58% of the theoretical maghemite bulk value, observed consistently by both techniques.

Physical particularities of nuclear reactors using heavy moderators of neutrons

NASA Astrophysics Data System (ADS)

Kulikov, G. G.; Shmelev, A. N.

2016-12-01

In nuclear reactors, thermal neutron spectra are formed using moderators with small atomic weights. For fast reactors, inserting such moderators in the core may create problems since they efficiently decelerate the neutrons. In order to form an intermediate neutron spectrum, it is preferable to employ neutron moderators with sufficiently large atomic weights, using 233U as a fissile nuclide and 232Th and 231Pa as fertile ones. The aim of the work is to investigate the properties of heavy neutron moderators and to assess their advantages. The analysis employs the JENDL-4.0 nuclear data library and the SCALE program package for simulating the variation of fuel composition caused by irradiation in the reactor. The following main results are obtained. By using heavy moderators with small neutron moderation steps, one is able to (1) increase the rate of resonance capture, so that the amount of fertile material in the fuel may be reduced while maintaining the breeding factor of the core; (2) use the vacant space for improving the fuel-element properties by adding inert, strong, and thermally conductive materials and by implementing dispersive fuel elements in which the fissile material is self-replenished and neutron multiplication remains stable during the process of fuel burnup; and (3) employ mixtures of different fertile materials with resonance capture cross sections in order to increase the resonance-lattice density and the probability of resonance neutron capture leading to formation of fissile material. The general conclusion is that, by forming an intermediate neutron spectrum with heavy neutron moderators, one can use the fuel more efficiently and improve nuclear safety.

Multiple Acquisition InSAR Analysis: Persistent Scatterer and Small Baseline Approaches

NASA Astrophysics Data System (ADS)

Hooper, A.

2006-12-01

InSAR techniques that process data from multiple acquisitions enable us to form time series of deformation and also allow us to reduce error terms present in single interferograms. There are currently two broad categories of methods that deal with multiple images: persistent scatterer methods and small baseline methods. The persistent scatterer approach relies on identifying pixels whose scattering properties vary little with time and look angle. Pixels that are dominated by a singular scatterer best meet these criteria; therefore, images are processed at full resolution to both increase the chance of there being only one dominant scatterer present, and to reduce the contribution from other scatterers within each pixel. In images where most pixels contain multiple scatterers of similar strength, even at the highest possible resolution, the persistent scatterer approach is less optimal, as the scattering characteristics of these pixels vary substantially with look angle. In this case, an approach that interferes only pairs of images for which the difference in look angle is small makes better sense, and resolution can be sacrificed to reduce the effects of the look angle difference by band-pass filtering. This is the small baseline approach. Existing small baseline methods depend on forming a series of multilooked interferograms and unwrapping each one individually. This approach fails to take advantage of two of the benefits of processing multiple acquisitions, however, which are usually embodied in persistent scatterer methods: the ability to find and extract the phase for single-look pixels with good signal-to-noise ratio that are surrounded by noisy pixels, and the ability to unwrap more robustly in three dimensions, the third dimension being that of time. We have developed, therefore, a new small baseline method to select individual single-look pixels that behave coherently in time, so that isolated stable pixels may be found. After correction for various error terms, the phase values of the selected pixels are unwrapped using a new three-dimensional algorithm. We apply our small baseline method to an area in southern Iceland that includes Katla and Eyjafjallajökull volcanoes, and retrieve a time series of deformation that shows transient deformation due to intrusion of magma beneath Eyjafjallajökull. We also process the data using the Stanford method for persistent scatterers (StaMPS) for comparison.

Release of Continuous Representation for S(α,β) ACE Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Conlin, Jeremy Lloyd; Parsons, Donald Kent

2014-03-20

For low energy neutrons, the default free gas model for scattering cross sections is not always appropriate. Molecular effects or crystalline structure effects can affect the neutron scattering cross sections. These effects are included in the S(α; β) thermal neutron scattering data and are tabulated in file 7 of the ENDF6 format files. S stands for scattering. α is a momentum transfer variable and is an energy transfer variable. The S(α; β) cross sections can include coherent elastic scattering (no E change for the neutron, but specific scattering angles), incoherent elastic scattering (no E change for the neutron, but continuousmore » scattering angles), and inelastic scattering (E change for the neutron, and change in angle as well). Every S(α; β) material will have inelastic scattering and may have either coherent or incoherent elastic scattering (but not both). Coherent elastic scattering cross sections have distinctive jagged-looking Bragg edges, whereas the other cross sections are much smoother. The evaluated files from the NNDC are processed locally in the THERMR module of NJOY. Data can be produced either for continuous energy Monte Carlo codes (using ACER) or embedded in multi-group cross sections for deterministic (or even multi-group Monte Carlo) codes (using GROUPR). Currently, the S(α; β) files available for MCNP use discrete energy changes for inelastic scattering. That is, the scattered neutrons can only be emitted at specific energies— rather than across a continuous spectrum of energies. The discrete energies are chosen to preserve the average secondary neutron energy, i.e., in an integral sense, but the discrete treatment does not preserve any differential quantities in energy or angle.« less

The Search for Nanobubbles by Using Specular and Off-Specular Neutron Reflectometry.

PubMed

Gutfreund, Philipp; Maccarini, Marco; Dennison, Andrew J C; Wolff, Max

2016-09-06

We apply specular and off-specular neutron reflection at the hydrophobic silicon/water interface to check for evidence of nanoscopic air bubbles whose presence is claimed after an ad hoc procedure of solvent exchange. Nanobubbles and/or a depletion layer at the hydrophobic/water interface have long been discussed and generated a plethora of controversial scientific results. By combining neutron reflectometry (NR), off-specular reflectometry (OSS), and grazing incidence small angle neutron scattering (GISANS), we studied the interface between hydrophobized silicon and heavy water before and after saturation with nitrogen gas. Our specular reflectometry results can be interpreted by assuming a submolecular sized depletion layer and the off-specular measurements show no change with nitrogen super saturated water. This picture is consistent with the assumption that, following the solvent exchange, no additional nanobubbles are introduced at significant concentrations (if present at all). Furthermore, we discuss the results in terms of the maximum surface coverage of nanobubbles that could be present on the hydrophobic surface compatibly with the sensitivity limit of these techniques.

Structural characterization of nanoscale intermetallic precipitates in highly neutron irradiated reactor pressure vessel steels

DOE PAGES

Sprouster, D. J.; Sinsheimer, J.; Dooryhee, E.; ...

2015-10-21

Here, massive, thick-walled pressure vessels are permanent nuclear reactor structures that are exposed to a damaging flux of neutrons from the adjacent core. The neutrons cause embrittlement of the vessel steel that increases with dose (fluence or service time), as manifested by an increasing temperature transition from ductile-to-brittle fracture. Moreover, extending reactor life requires demonstrating that large safety margins against brittle fracture are maintained at the higher neutron fluence associated with 60 to 80 years of service. Here synchrotron-based x-ray diffraction and small angle x-ray scattering measurements are used to characterize a new class of highly embrittling nm-scale Mn-Ni-Si precipitatesmore » that develop in the irradiated steels at high fluence. Furthermore, these precipitates can lead to severe embrittlement that is not accounted for in current regulatory models. Application of the complementarity techniques has, for the very first time, successfully characterized the crystal structures of the nanoprecipitates, while also yielding self-consistent compositions, volume fractions and size distributions.« less

Surface areas of fractally rough particles studied by scattering

NASA Astrophysics Data System (ADS)

Hurd, Alan J.; Schaefer, Dale W.; Smith, Douglas M.; Ross, Steven B.; Le Méhauté, Alain; Spooner, Steven

1989-05-01

The small-angle scattering from fractally rough surfaces has the potential to give information on the surface area at a given resolution. By use of quantitative neutron and x-ray scattering, a direct comparison of surface areas of fractally rough powders was made between scattering and adsorption techniques. This study supports a recently proposed correction to the theory for scattering from fractal surfaces. In addition, the scattering data provide an independent calibration of molecular adsorbate areas.

Observation of hairpin defects in a nematic main-chain polyester

NASA Astrophysics Data System (ADS)

Li, M. H.; Brûlet, A.; Davidson, P.; Keller, P.; Cotton, J. P.

1993-04-01

The conformation of a main-chain liquid crystalline polyester in its oriented nematic phase has been determined by small-angle neutron scattering. The data are fitted by a model of rigid cylinder with orientational fluctuations. For a low degree of polymerization (~9) the chain is almost completely elongated in the direction of the nematic field. For a polymer 3 times longer, the existence of two hairpins is shown at high temperature; this number decreases with decreasing temperature.

Interactions in micellar solutions of β-casein

NASA Astrophysics Data System (ADS)

Leclerc, E.; Calmettes, P.

1997-02-01

β-casein is a protein which forms micelles in aqueous solvents. The magnitude and the range of the weight-average interactions between the diverse solute particles are infrared from small-angle neutron scattering measurements made on various β-casein solutions. Well above the critical micelle concentration (CMC), these interactions are repulsive. They weaken with decreasing protein concentration, and finally become strongly attractive near the CMC. Although indispensable for micelle formation this fact has never been reported so far.

Small-angle neutron scattering study of a dense microemulsion system formed with an ionic liquid

DOE PAGES

Kang, T.; Qian, S.; Smith, G. S.; ...

2017-09-07

Mixtures of water, octane and 1-octanol with 1-tetradecyl-3-methylimidazolium chloride (C14MIM·Cl), often referred to as a surface active ionic liquid (SAIL), form water-in-oil microemulsions that have potential application as extraction media for various metal ions. Here in this work, we present a structural study by small-angle neutron scattering (SANS) of dense microemulsions formed by surfactant-rich mixtures of these four compounds to understand how the SAIL can be used to tune the structures and properties of the microemulsions. The SANS experiments revealed that the microemulsions formed are composed of two phases, a water-in-oil microemulsion and a bicontinuous microemulsion, which becomes the dominantmore » phase at high surfactant concentration. In this concentration regime, the surfactant film becomes more rigid, having a higher bending modulus that results from the parallel stacking of the imidazolium ring of the SAIL. At lower surfactant concentrations, the molecular packing of the SAIL does not change with the water content of the microemulsion. Finally, the results presented here correlate well with previously observed changes in the interaction between the IL cation and metal ions (Y. Tong, L. Han and Y. Yang, Ind. Eng. Chem. Res., 2012, 51, 16438–16443), while the capacity of the microemulsion system for water remains high enough for using the system as an extraction medium.« less

Small-angle neutron scattering study of a dense microemulsion system formed with an ionic liquid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kang, T.; Qian, S.; Smith, G. S.

Mixtures of water, octane and 1-octanol with 1-tetradecyl-3-methylimidazolium chloride (C14MIM·Cl), often referred to as a surface active ionic liquid (SAIL), form water-in-oil microemulsions that have potential application as extraction media for various metal ions. Here in this work, we present a structural study by small-angle neutron scattering (SANS) of dense microemulsions formed by surfactant-rich mixtures of these four compounds to understand how the SAIL can be used to tune the structures and properties of the microemulsions. The SANS experiments revealed that the microemulsions formed are composed of two phases, a water-in-oil microemulsion and a bicontinuous microemulsion, which becomes the dominantmore » phase at high surfactant concentration. In this concentration regime, the surfactant film becomes more rigid, having a higher bending modulus that results from the parallel stacking of the imidazolium ring of the SAIL. At lower surfactant concentrations, the molecular packing of the SAIL does not change with the water content of the microemulsion. Finally, the results presented here correlate well with previously observed changes in the interaction between the IL cation and metal ions (Y. Tong, L. Han and Y. Yang, Ind. Eng. Chem. Res., 2012, 51, 16438–16443), while the capacity of the microemulsion system for water remains high enough for using the system as an extraction medium.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Viani, Alberto, E-mail: viani@itam.cas.cz; Sotiriadis, Konstantinos; Len, Adél

Full characterization of fired-clay bricks is crucial for the improvement of process variables in manufacturing and, in case of old bricks, for restoration/replacement purposes. To this aim, five bricks produced in a plant in Czech Republic in the past have been investigated with a combination of analytical techniques in order to derive information on the firing process. An additional old brick from another brickyard was also used to study the influence of different raw materials on sample microstructure. The potential of X-ray diffraction with the Rietveld method and small angle neutron scattering technique has been exploited to describe the phasemore » transformations taking place during firing and characterize the brick microstructure. Unit-cell parameter of spinel and amount of hematite are proposed as indicators of the maximum firing temperature, although for the latter, limited to bricks produced from the same raw material. The fractal quality of the surface area of pores obtained from small angle neutron scattering is also suggested as a method to distinguish between bricks produced from different raw clays. - Highlights: • Rietveld method helps in describing microstructure and physical properties of bricks. • XRPD derived cell parameter of spinel is proposed as an indicator of firing temperature. • SANS effectively describes brick micro and nanostructure, including closed porosity. • Fractal quality of pore surface is proposed as ‘fingerprint’ of brick manufacturing.« less

Properties of surfactant films in water-in-CO2 microemulsions obtained by small-angle neutron scattering.

PubMed

Yan, Ci; Sagisaka, Masanobu; James, Craig; Rogers, Sarah; Alexander, Shirin; Eastoe, Julian

2014-12-01

The formation, stability and structural properties of normal liquid phase microemulsions, stabilized by hydrocarbon surfactants, comprising water and hydrocarbon oils can be interpreted in terms of the film bending rigidity (energy) model. Here, this model is tested for unusual water-in-CO2 (w/c) microemulsions, formed at high pressure with supercritical CO2 (sc-CO2) as a solvent and fluorinated surfactants as stabilizers. Hence, it is possible to explore the generality of this model for other types of microemulsions. High Pressure Small-Angle Neutron Scattering (HP-SANS) has been used to study w/c microemulsions, using contrast variation to highlight scattering from the stabilizing fluorinated surfactant films: these data show clear evidence for spherical core-shell structures for the microemulsion droplets. The results extend understanding of w/c microemulsions since previous SANS studies are based only on scattering from water core droplets. Here, detailed structural parameters for the surfactant films, such as thickness and film bending energy, have been extracted from the core-shell SANS profiles revealed by controlled contrast variation. Furthermore, at reduced CO2 densities (∼0.7gcm(-3)), elongated cylindrical droplet structures have been observed, which are uncommon for CO2 microemulsions/emulsions. The implications of the presence of cylindrical micelles and droplets for applications of CO2, and viscosity enhancements are discussed. Copyright © 2014 Elsevier Inc. All rights reserved.

Phosphatidylinositol 4,5-Bisphosphate Clusters the Cell Adhesion Molecule CD44 and Assembles a Specific CD44-Ezrin Heterocomplex, as Revealed by Small Angle Neutron Scattering*

PubMed Central

Chen, Xiaodong; Khajeh, Jahan Ali; Ju, Jeong Ho; Gupta, Yogesh K.; Stanley, Christopher B.; Do, Changwoo; Heller, William T.; Aggarwal, Aneel K.; Callaway, David J. E.; Bu, Zimei

2015-01-01

The cell adhesion molecule CD44 regulates diverse cellular functions, including cell-cell and cell-matrix interaction, cell motility, migration, differentiation, and growth. In cells, CD44 co-localizes with the membrane-cytoskeleton adapter protein Ezrin that links the CD44 assembled receptor signaling complexes to the cytoskeletal actin network, which organizes the spatial and temporal localization of signaling events. Here we report that the cytoplasmic tail of CD44 (CD44ct) is largely disordered. Upon binding to the signaling lipid phosphatidylinositol 4,5-bisphosphate (PIP2), CD44ct clusters into aggregates. Further, contrary to the generally accepted model, CD44ct does not bind directly to the FERM domain of Ezrin or to the full-length Ezrin but only forms a complex with FERM or with the full-length Ezrin in the presence of PIP2. Using contrast variation small angle neutron scattering, we show that PIP2 mediates the assembly of a specific heterotetramer complex of CD44ct with Ezrin. This study reveals the role of PIP2 in clustering CD44 and in assembling multimeric CD44-Ezrin complexes. We hypothesize that polyvalent electrostatic interactions are responsible for the assembly of CD44 clusters and the multimeric PIP2-CD44-Ezrin complexes. PMID:25572402

Phosphatidylinositol 4,5-bisphosphate clusters the cell adhesion molecule CD44 and assembles a specific CD44-Ezrin heterocomplex, as revealed by small angle neutron scattering.

PubMed

Chen, Xiaodong; Khajeh, Jahan Ali; Ju, Jeong Ho; Gupta, Yogesh K; Stanley, Christopher B; Do, Changwoo; Heller, William T; Aggarwal, Aneel K; Callaway, David J E; Bu, Zimei

2015-03-06

The cell adhesion molecule CD44 regulates diverse cellular functions, including cell-cell and cell-matrix interaction, cell motility, migration, differentiation, and growth. In cells, CD44 co-localizes with the membrane-cytoskeleton adapter protein Ezrin that links the CD44 assembled receptor signaling complexes to the cytoskeletal actin network, which organizes the spatial and temporal localization of signaling events. Here we report that the cytoplasmic tail of CD44 (CD44ct) is largely disordered. Upon binding to the signaling lipid phosphatidylinositol 4,5-bisphosphate (PIP2), CD44ct clusters into aggregates. Further, contrary to the generally accepted model, CD44ct does not bind directly to the FERM domain of Ezrin or to the full-length Ezrin but only forms a complex with FERM or with the full-length Ezrin in the presence of PIP2. Using contrast variation small angle neutron scattering, we show that PIP2 mediates the assembly of a specific heterotetramer complex of CD44ct with Ezrin. This study reveals the role of PIP2 in clustering CD44 and in assembling multimeric CD44-Ezrin complexes. We hypothesize that polyvalent electrostatic interactions are responsible for the assembly of CD44 clusters and the multimeric PIP2-CD44-Ezrin complexes. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Phase behavior of blends of linear and branched polyethylenes in the molten and solid states by small-angle neutron scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alamo, R.G.; Mandelkern, L.; Londono, J.D.

1994-01-17

The state of mixing in blends of high-density polyethylene (HDPE) and low-density polyethylene (LDPE) in the liquid and solid state has been examined by small-angle neutron scattering (SANS) in conjunction with deuterium labeling. In the melt, SANS results indicate that HDPE/LDPE mixtures from a single-phase solution for all concentrations, including blends containing high volume fractions ([phi] > 0.5) of branched polymer, for which multiphase melts have previously been suggested. Proper accounting for isotope effects is essential to avoid artifacts, because the H/D interaction parameter is sufficiently large ([sub [chi]HD] [approximately] 4 [times] 10[sup [minus]4]) to cause phase separation in themore » amorphous state for molecular weights (MW) >150,000. In the solid state, after slow cooling from the melt ([approximately]0.75 C/min), the HDPE/LDPE system shows extensive segregation into separate domains [approximately]100--300 [angstrom] in size. Both the shape and magnitude of the absolute scattering cross section are consistent with the conclusion that the components are extensively segregated into separate lamellae. Two-peak melting curves obtained for such mixtures support the SANS interpretation, and the segregation of components in the solid state is therefore a consequence of crystallization mechanisms rather than incompatibility in the liquid state.« less

Preliminary analysis of the distribution of water in human hair by small-angle neutron scattering.

PubMed

Kamath, Yash; Murthy, N Sanjeeva; Ramaprasad, Ram

2014-01-01

Diffusion and distribution of water in hair can reveal the internal structure of hair that determines the penetration of various products used to treat hair. The distribution of water into different morphological components in unmodified hair, cuticle-free hair, and hair saturated with oil at various levels of humidity was examined using small-angle neutron scattering (SANS) by substituting water with deuterium oxide (D(2)O). Infrared spectroscopy was used to follow hydrogen-deuterium exchange. Water present in hair gives basically two types of responses in SANS: (i) interference patterns, and (ii) central diffuse scattering (CDS) around the beam stop. The amount of water in the matrix between the intermediate filaments that gives rise to interference patterns remained essentially constant over the 50-98% humidity range without swelling this region of the fiber extensively. This observation suggests that a significant fraction of water in the hair, which contributes to the CDS, is likely located in a different morphological region of hair that is more like pores in a fibrous structure, which leads to significant additional swelling of the fiber. Comparison of the scattering of hair treated with oil shows that soybean oil, which diffuses less into hair, allows more water into hair than coconut oil. These preliminary results illustrate the utility of SANS for evaluating and understanding the diffusion of deuterated liquids into different morphological structures in hair.

Analysis of the solution structure of Thermosynechococcus elongatus photosystem I in n-dodecyl-β-d-maltoside using small-angle neutron scattering and molecular dynamics simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le, Rosemary K.; Harris, Bradley J.; Iwuchukwu, Ifeyinwa J.

2014-05-01

Small-angle neutron scattering (SANS) and molecular dynamics (MD) simulation were used to investigate the structure of trimeric photosystem I (PSI) from Thermosynechococcus elongatus (T. elongatus) stabilized in n-dodecyl-β-d-maltoside (DDM) detergent solution. Scattering curves of detergent and protein–detergent complexes were measured at 18% D2O, the contrast match point for the detergent, and 100% D2O, allowing observation of the structures of protein/detergent complexes. It was determined that the maximum dimension of the PSI–DDM complex was consistent with the presence of a monolayer belt of detergent around the periphery of PSI. A dummy-atom reconstruction of the shape of the complex from the SANSmore » data indicates that the detergent envelope has an irregular shape around the hydrophobic periphery of the PSI trimer rather than a uniform, toroidal belt around the complex. A 50 ns MD simulation model (a DDM ring surrounding the PSI complex with extra interstitial DDM) of the PSI–DDM complex was developed for comparison with the SANS data. The results suggest that DDM undergoes additional structuring around the membrane-spanning surface of the complex instead of a simple, relatively uniform belt, as is generally assumed for studies that use detergents to solubilize membrane proteins.« less

Response Functions for Neutron Skyshine Analyses

NASA Astrophysics Data System (ADS)

Gui, Ah Auu

Neutron and associated secondary photon line-beam response functions (LBRFs) for point monodirectional neutron sources and related conical line-beam response functions (CBRFs) for azimuthally symmetric neutron sources are generated using the MCNP Monte Carlo code for use in neutron skyshine analyses employing the internal line-beam and integral conical-beam methods. The LBRFs are evaluated at 14 neutron source energies ranging from 0.01 to 14 MeV and at 18 emission angles from 1 to 170 degrees. The CBRFs are evaluated at 13 neutron source energies in the same energy range and at 13 source polar angles (1 to 89 degrees). The response functions are approximated by a three parameter formula that is continuous in source energy and angle using a double linear interpolation scheme. These response function approximations are available for a source-to-detector range up to 2450 m and for the first time, give dose equivalent responses which are required for modern radiological assessments. For the CBRF, ground correction factors for neutrons and photons are calculated and approximated by empirical formulas for use in air-over-ground neutron skyshine problems with azimuthal symmetry. In addition, a simple correction procedure for humidity effects on the neutron skyshine dose is also proposed. The approximate LBRFs are used with the integral line-beam method to analyze four neutron skyshine problems with simple geometries: (1) an open silo, (2) an infinite wall, (3) a roofless rectangular building, and (4) an infinite air medium. In addition, two simple neutron skyshine problems involving an open source silo are analyzed using the integral conical-beam method. The results obtained using the LBRFs and the CBRFs are then compared with MCNP results and results of previous studies.

Improvement of the prompt-gamma neutron activation facility at Brookhaven National Laboratory.

PubMed

Dilmanian, F A; Lidofsky, L J; Stamatelatos, I; Kamen, Y; Yasumura, S; Vartsky, D; Pierson, R N; Weber, D A; Moore, R I; Ma, R

1998-02-01

The prompt-gamma neutron activation facility at Brookhaven National Laboratory was upgraded to improve both the precision and accuracy of its in vivo determinations of total body nitrogen. The upgrade, guided by Monte Carlo simulations, involved elongating and modifying the source collimator and its shielding, repositioning the system's two NaI(Tl) detectors, and improving the neutron and gamma shielding of these detectors. The new source collimator has a graphite reflector around the 238PuBe neutron source to enhance the low-energy region of the neutron spectrum incident on the patient. The gamma detectors have been relocated from positions close to the upward-emerging collimated neutron beam to positions close to and at the sides of the patient. These modifications substantially reduced spurious counts resulting from the capture of small-angle scattered neutrons in the NaI detectors. The pile-up background under the 10.8 MeV 14N(n, gamma)15N spectral peak has been reduced so that the nitrogen peak-to-background ratio has been increased by a factor of 2.8. The resulting reduction in the coefficient of variation of the total body nitrogen measurements from 3% to 2.2% has improved the statistical significance of the results possible for any given number of patient measurements. The new system also has a more uniform composite sensitivity.

Multi-scale characterization of pore evolution in a combustion metamorphic complex, Hatrurim basin, Israel: Combining (ultra) small-angle neutron scattering and image analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Hsiu-Wen; Anovitz, Lawrence; Burg, Avihu

Backscattered scanning electron micrograph and ultra small- and small-angle neutron scattering data have been combined to provide statistically meaningful data on the pore/grain structure and pore evolution of combustion metamorphic complexes from the Hatrurim basin, Israel. Three processes, anti-sintering roughening, alteration of protolith (dehydration, decarbonation, and oxidation) and crystallization of high-temperature minerals, occurred simultaneously, leading to significant changes in observed pore/grain structures. Pore structures in the protoliths, and in lowand high-grade metamorphic rocks show surface (Ds) and mass (Dm) pore fractal geometries with gradual increases in both Ds and Dm values as a function of metamorphic grade. This suggests thatmore » increases in pore volume and formation of less branching pore networks are accompanied by a roughening of pore/grain interfaces. Additionally, pore evolution during combustion metamorphism is also characterized by reduced contributions from small-scale pores to the cumulative porosity in the high-grade rocks. At high temperatures, small-scale pores may be preferentially closed by the formation of high-temperature minerals, producing a rougher morphology with increasing temperature. Alternatively, large-scale pores may develop at the expense of small-scale pores. These observations (pore fractal geometry and cumulative porosity) indicate that the evolution of pore/grain structures is correlated with the growth of high-temperature phases and is a consequence of the energy balance between pore/grain surface energy and energy arising from heterogeneous phase contacts. The apparent pore volume density further suggests that the localized time/temperature development of the high-grade Hatrurim rocks is not simply an extension of that of the low-grade rocks. The former likely represents the "hot spots (burning foci)" in the overall metamorphic terrain while the latter may represent contact aureoles.« less

Comparison of SANS instruments at reactors and pulsed sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thiyagarajan, P.; Epperson, J.E.; Crawford, R.K.

1992-09-01

Small angle neutron scattering is a general purpose technique to study long range fluctuations and hence has been applied in almost every field of science for material characterization. SANS instruments can be built at steady state reactors and at the pulsed neutron sources where time-of-flight (TOF) techniques are used. The steady state instruments usually give data over small q ranges and in order to cover a large q range these instruments have to be reconfigured several times and SANS measurements have to be made. These instruments have provided better resolution and higher data rates within their restricted q ranges untilmore » now, but the TOF instruments are now developing to comparable performance. The TOF-SANS instruments, by using a wide band of wavelengths, can cover a wide dynamic q range in a single measurement. This is a big advantage for studying systems that are changing and those which cannot be exactly reproduced. This paper compares the design concepts and performances of these two types of instruments.« less

Effects of Correlated and Uncorrelated Gamma Rays on Neutron Multiplicity Counting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cowles, Christian C.; Behling, Richard S.; Imel, George R.

Neutron multiplicity counting relies on time correlation between neutron events to assay the fissile mass, (α,n) to spontaneous fission neutron ratio, and neutron self-multiplication of samples. Gamma-ray sensitive neutron multiplicity counters may misidentify gamma rays as neutrons and therefore miscalculate sample characteristics. Time correlated and uncorrelated gamma-ray-like signals were added into gamma-ray free neutron multiplicity counter data to examine the effects of gamma ray signals being misidentified as neutron signals on assaying sample characteristics. Multiplicity counter measurements with and without gamma-ray-like signals were compared to determine the assay error associated with gamma-ray-like signals at various gamma-ray and neutron rates. Correlatedmore » and uncorrelated gamma-ray signals each produced consistent but different measurement errors. Correlated gamma-ray signals most strongly led to fissile mass overestimates, whereas uncorrelated gamma-ray signals most strongly lead to (α,n) neutron overestimates. Gamma-ray sensitive neutron multiplicity counters may be able to account for the effects of gamma-rays on measurements to mitigate measurement uncertainties.« less

Characterisation of large scale structures in starch granules via small-angle neutron and X-ray scattering.

PubMed

Doutch, James; Gilbert, Elliot P

2013-01-02

Small angle scattering (SAS) techniques have a distinguished track record in illuminating the semi-crystalline lamellar structure of the starch granule. To date, there have been few attempts to use SAS techniques to characterise larger-scale structures reported from imaging techniques such as growth rings, blocklets or pores, nor how these structures would modulate the well-known scattering arising from the semi-crystalline lamellar structure. In this study, SAS data collected over an extended q range were gathered from dry and hydrated starch powders from varied botanical sources. The use of neutrons and X-rays, as well as comparing dry and hydrated granules, allowed different levels of contrast in scattering length density to be probed and therefore selected structural regions to be highlighted. The lowest q range, 0.002-0.04 Å(-1), was found to be dominated by scattering from the starch granules themselves, especially in the dry powders; however an inflection point from a low contrast structure was observed at 0.035 Å(-1). The associated scattering was interpreted within a unified scattering framework with the inflexion point correlating with a structure with radius of gyration ~90 Å - a size comparable to small blocklets or superhelices. In hydrated starches, it is observed that there is an inflection point between lamellar and q(-4) power-law scattering regions at approximately 0.004 Å(-1) which may correlate with growth rings and large blocklets. The implications of these findings on existing models of starch lamellar scattering are discussed. Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.

Structural and magnetic properties of multi-core nanoparticles analysed using a generalised numerical inversion method

PubMed Central

Bender, P.; Bogart, L. K.; Posth, O.; Szczerba, W.; Rogers, S. E.; Castro, A.; Nilsson, L.; Zeng, L. J.; Sugunan, A.; Sommertune, J.; Fornara, A.; González-Alonso, D.; Barquín, L. Fernández; Johansson, C.

2017-01-01

The structural and magnetic properties of magnetic multi-core particles were determined by numerical inversion of small angle scattering and isothermal magnetisation data. The investigated particles consist of iron oxide nanoparticle cores (9 nm) embedded in poly(styrene) spheres (160 nm). A thorough physical characterisation of the particles included transmission electron microscopy, X-ray diffraction and asymmetrical flow field-flow fractionation. Their structure was ultimately disclosed by an indirect Fourier transform of static light scattering, small angle X-ray scattering and small angle neutron scattering data of the colloidal dispersion. The extracted pair distance distribution functions clearly indicated that the cores were mostly accumulated in the outer surface layers of the poly(styrene) spheres. To investigate the magnetic properties, the isothermal magnetisation curves of the multi-core particles (immobilised and dispersed in water) were analysed. The study stands out by applying the same numerical approach to extract the apparent moment distributions of the particles as for the indirect Fourier transform. It could be shown that the main peak of the apparent moment distributions correlated to the expected intrinsic moment distribution of the cores. Additional peaks were observed which signaled deviations of the isothermal magnetisation behavior from the non-interacting case, indicating weak dipolar interactions. PMID:28397851

Aggregation, adsorption, and surface properties of multiply end-functionalized polystyrenes.

PubMed

Ansari, Imtiyaz A; Clarke, Nigel; Hutchings, Lian R; Pillay-Narrainen, Amilcar; Terry, Ann E; Thompson, Richard L; Webster, John R P

2007-04-10

The properties of polystyrene blends containing deuteriopolystyrene, multiply end-functionalized with C8F17 fluorocarbon groups, are strikingly analogous to those of surfactants in solution. These materials, denoted FxdPSy, where x is the number of fluorocarbon groups and y is the molecular weight of the dPS chain in kg/mol, were blended with unfunctionalized polystyrene, hPS. Nuclear reaction analysis experiments show that FxdPSy polymers adsorb spontaneously to solution and blend surfaces, resulting in a reduction in surface energy inferred from contact angle analysis. Aggregation of functionalized polymers in the bulk was found to be sensitive to FxdPSy structure and closely related to surface properties. At low concentrations, the functionalized polymers are freely dispersed in the hPS matrix, and in this range, the surface excess concentration grows sharply with increasing bulk concentration. At higher concentrations, surface excess concentrations and contact angles reach a plateau, small-angle neutron scattering data indicate small micellar aggregates of six to seven F2dPS10 polymer chains and much larger aggregates of F4dPS10. Whereas F2dPS10 aggregates are miscible with the hPS matrix, F4dPS10 forms a separate phase of multilamellar vesicles. Using neutron reflectometry (NR), we found that the extent of the adsorbed layer was approximately half the lamellar spacing of the multilamellar vesicles. NR data were fitted using an error function profile to describe the concentration profile of the adsorbed layer, and reasonable agreement was found with concentration profiles predicted by the SCFT model. The thermodynamic sticking energy of the fluorocarbon-functionalized polymer chains to the blend surface increases from 5.3kBT for x = 2 to 6.6kBT for x = 4 but appears to be somewhat dependent upon the blend concentration.

Recent advancements of wide-angle polarization analysis with 3He neutron spin filters

NASA Astrophysics Data System (ADS)

Chen, W. C.; Gentile, T. R.; Ye, Q.; Kirchhoff, A.; Watson, S. M.; Rodriguez-Rivera, J. A.; Qiu, Y.; Broholm, C.

2016-09-01

Wide-angle polarization analysis with polarized 3He based neutron spin filters (NSFs) has recently been employed on the Multi-Axis Crystal Spectrometer (MACS) at the National Institute of Standards and Technology Center for Neutron Research (NCNR). Over the past several years, the apparatus has undergone many upgrades to address the fundamental requirements for wide angle polarization analysis using spin exchange optical pumping based 3He NSFs. In this paper, we report substantial improvements in the on-beam-line performance of the apparatus and progress toward routine user capability. We discuss new standard samples used for 3He NSF characterization and the flipping ratio measurement on MACS. We further discuss the management of stray magnetic fields produced by operation of superconducting magnets on the MACS instrument, which can significantly reduce the 3He polarization relaxation time. Finally, we present the results of recent development of horseshoe-shaped wide angle cells.

New Frontier in Probing Fluid Transport in Low-Permeability Geomedia: Applications of Elastic and Inelastic Neutron Scattering

NASA Astrophysics Data System (ADS)

Ding, M.; Hjelm, R.; Sussman, A. J.

2016-12-01

Low-permeability geomedia are prevalent in subsurface environments. They have become increasingly important in a wide range of applications such as CO2-sequestration, hydrocarbon recovery, enhanced geothermal systems, legacy waste stewardship, high-level radioactive waste disposal, and global security. The flow and transport characteristics of low-permeability geomedia are dictated by their exceedingly low permeability values ranging from 10-6 to 10-12 darcy with porosities dominated by nanoscale pores. Developing new characterization methods and robust computational models that allow estimation of transport properties of low-permeability geomedia has been identified as a critical basic research and technology development need for controlling subsurface and fluids flow. Due to its sensibility to hydrogen and flexible sample environment, neutron based elastic and inelastic scattering can, through various techniques, interrogate all the nanoscale pores in the sample whether they are fluid accessible or not, and readily characterize interfacial waters. In this presentation, we will present two studies revealing the effects of nanoscale pore confinement on fluid dynamics in geomedia. In one study, we use combined (ultra-small)/small-angle elastic neutron scatterings to probe nanoporous features responses in geological materials to transport processes. In the other study, incoherent inelastic neutron scattering was used to distingwish between intergranular pore water and fluid inclusion moisture in bedded rock salt, and to explore their thermal stablibility. Our work demonstrates that neutron based elastic and inelastic scatterings are techniques of choice for in situ probing hydrocarbon and water behavior in nanoporous materials, providing new insights into water-rock interaction and fluids transport in low-permeability geomaterials.

A large 2D PSD for thermal neutron detection

NASA Astrophysics Data System (ADS)

Knott, R. B.; Smith, G. C.; Watt, G.; Boldeman, J. W.

1997-02-01

A 2D PSD based on a MWPC has been constructed for a small angle neutron scattering instrument. The active area of the detector was 640 × 640 mm 2. To meet the specifications for neutron detection efficiency and spatial resolution, and to minimise parallax, the gas mixture was 190 kPa 3He plus 100 kPa CF 4, and the active volume had a thickness of 30 mm. The design maximum neutron count rate of the detector was 10 5 events per secod. The (calculated) neutron detection efficiency was 60% for 2 Å neutrons and the (measured) neutron energy resolution on the anode grid was typically 20% (fwhm). The location of a neutron detection event within the active area was determined using the wire-by-wire method: the spatial resolution (5 × 5 mm 2) was thereby defined by the wire geometry. A 16-channel charge-sensitive preamplifier/amplifier/comparator module has been developed with a channel sensitivity of 0.1 V/fC, noise line width of 0.4 fC (fwhm) and channel-to-channel cross-talk of less than 5%. The Proportional Counter Operating System (PCOS III) (LeCroy Corp, USA) was used for event encoding. The ECL signals produced by the 16 channel modules were latched in PCOS III by a trigger pulse from the anode and the fast encoders produce a position and width for each event. The information was transferred to a UNIX workstation for accumulation and online display.

Physical particularities of nuclear reactors using heavy moderators of neutrons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kulikov, G. G., E-mail: ggkulikov@mephi.ru; Shmelev, A. N.

2016-12-15

In nuclear reactors, thermal neutron spectra are formed using moderators with small atomic weights. For fast reactors, inserting such moderators in the core may create problems since they efficiently decelerate the neutrons. In order to form an intermediate neutron spectrum, it is preferable to employ neutron moderators with sufficiently large atomic weights, using {sup 233}U as a fissile nuclide and {sup 232}Th and {sup 231}Pa as fertile ones. The aim of the work is to investigate the properties of heavy neutron moderators and to assess their advantages. The analysis employs the JENDL-4.0 nuclear data library and the SCALE program packagemore » for simulating the variation of fuel composition caused by irradiation in the reactor. The following main results are obtained. By using heavy moderators with small neutron moderation steps, one is able to (1) increase the rate of resonance capture, so that the amount of fertile material in the fuel may be reduced while maintaining the breeding factor of the core; (2) use the vacant space for improving the fuel-element properties by adding inert, strong, and thermally conductive materials and by implementing dispersive fuel elements in which the fissile material is self-replenished and neutron multiplication remains stable during the process of fuel burnup; and (3) employ mixtures of different fertile materials with resonance capture cross sections in order to increase the resonance-lattice density and the probability of resonance neutron capture leading to formation of fissile material. The general conclusion is that, by forming an intermediate neutron spectrum with heavy neutron moderators, one can use the fuel more efficiently and improve nuclear safety.« less

Pair Production and Gamma-Ray Emission in the Outer Magnetospheres of Rapidly Spinning Young Pulsars

NASA Technical Reports Server (NTRS)

Ruderman, Malvin; Chen, Kaiyou

1997-01-01

Electron-positron pair production and acceleration in the outer magnetosphere may be crucial for a young rapidly spinning canonical pulsar to be a strong Gamma-ray emitter. Collision between curvature radiated GeV photons and soft X-ray photons seems to be the only efficient pair production mechanism. For Crib-like pulsars, the magnetic field near the light cylinder is so strong, such that the synchrotron radiation of secondary pairs will be in the needed X-ray range. However, for majority of the known Gamma-ray pulsars, surface emitted X-rays seem to work as the matches and fuels for a gamma-ray generation fireball in the outer magnetosphere. The needed X-rays could come from thermal emission of a cooling neutron star or could be the heat generated by bombardment of the polar cap by energetic particles generated in the outer magnetosphere. With detection of more Gamma-ray pulsars, it is becoming evident that the neutron star's intrisic geometry (the inclination angle between the rotation and magnetic axes) and observational geometry (the viewing angle with respect to the rotation axis) are crucial to the understanding of varieties of observational properties exhibited by these pulsars. Inclination angles for many known high energy Gamma-ray pulsars appear to be large and the distribution seems to be consistent with random orientation. However, all of them except Geminga are pre-selected from known radio pulsars. The viewing angles are thus limited to be around the respective inclination angles for beamed radio emission, which may induce strong selection effect. The viewing angles as well as the inclination angles of PSR 1509-58 and PSB 0656+14 may be small such that most of the high energy Gamma-rays produced in the outer accelerators may not reach the observer's direction. The observed Gamma-rays below 5 MeV from this pulsar may be synchrotron radiation of secondary electron-positron pairs produced outside the accelerating regions.

Character of the opposition effect and negative polarization

NASA Technical Reports Server (NTRS)

Pieters, Carle M.; Shkuratov, Yu. G.; Stankevich, D. G.

1991-01-01

Photometric and polarimetric properties at small phase angles were measured for silicates with controlled surface properties in order to distinguish properties that are associated with surface reflection from those that are associated with multiple scattering from internal grain boundaries. These data provide insight into the causes and conditions of photometric properties observed at small phase angles for dark bodies of the solar system. Obsidian was chosen to represent a silicate dielectric with no internal scattering boundaries. Because obsidian is free of internal scatterers, light reflected from both the rough and smooth obsidian samples is almost entirely single and multiple Fresnel reflections form surface facets with no body component. Surface structure alone cannot produce an opposition effect. Comparison of the obsidian and basalt results indicates that for an opposition effect to occur, surface texture must be both rough and contain internal scattering interfaces. Although the negative polarization observed for the obsidian samples indicates single and multiple reflections are part of negative polarization, the longer inversion angle of the multigrain inversion samples implies that internal reflections must also contribute a significant negative polarization component.

Effect of high intensity ultrasound on the mesostructure of hydrated zirconia

NASA Astrophysics Data System (ADS)

Kopitsa, G. P.; Baranchikov, A. E.; Ivanova, O. S.; Yapryntsev, A. D.; Grigoriev, S. V.; Pranzas, P. Klaus; Ivanov, V. K.

2012-02-01

We report structural changes in amorphous hydrated zirconia caused by high intensity ultrasonic treatment studied by means of small-angle neutron scattering (SANS) and X-ray diffraction (XRD). It was established that sonication affects the mesostructure of ZrO2×xH2O gels (i.e. decreases their homogeneity, increases surface fractal dimension and the size of monomer particles). Ultrasound induced structural changes in hydrated zirconia governs its thermal behaviour, namely decreases the rate of tetragonal to monoclinic zirconia phase transition.

Effects of Sample Impurities on the Analysis of MS2 Bacteriophage by Small-Angle Neutron Scattering

DTIC Science & Technology

2005-08-01

and the efficiency of water treatment plants and filtration devices (Jolis et al., 1999;3 Oppenheimer et al., 1997;4 Woolwine and Gerberding, 1995;5...the solvent water to deuterated water ratio so that structural information about the protein and nucleic acid components can be obtained separately...de-stained in a 30% methanol: 10% acetic acid:60% (v/v) water solution for 8 hr (Maniatis, Fritsch et al., 1982).37 2.4 SANS Measurements. SANS

Interactions in Micellar Solutions of β-Casein

NASA Astrophysics Data System (ADS)

Leclerc, E.; Calmettes, P.

1997-01-01

β-casein is a flexible amphiphilic milk protein which forms spherical micelles in very dilute solution. The magnitude of the weight-average interactions between the solute particles has been inferred from small-angle neutron scattering experiments. At relatively high protein concentrations the interactions between micelles are repulsive, whatever the temperature. At lower concentration these interactions vanish and become more and more attractive when the critical micelle concentration is approached. Although indispensable for micelle formation, this fact seems to have not been previously reported.

The very low angle detector for high-energy inelastic neutron scattering on the VESUVIO spectrometer

NASA Astrophysics Data System (ADS)

Perelli Cippo, E.; Gorini, G.; Tardocchi, M.; Pietropaolo, A.; Andreani, C.; Senesi, R.; Rhodes, N. J.; Schooneveld, E. M.

2008-05-01

The Very Low Angle Detector (VLAD) bank has been installed on the VESUVIO spectrometer at the ISIS spallation neutron source. The new device allows for high-energy inelastic neutron scattering measurements, at energies above 1 eV, maintaining the wave vector transfer lower than 10Å-1. This opens a still unexplored region of the kinematical (q, ω) space, enabling new and challenging experimental investigations in condensed matter. This paper describes the main instrumental features of the VLAD device, including instrument design, detector response, and calibration procedure.

Comparing results of X-ray diffraction, µ-Raman spectroscopy and neutron diffraction when identifying chemical phases in seized nuclear material, during a comparative nuclear forensics exercise.

PubMed

Rondahl, Stina Holmgren; Pointurier, Fabien; Ahlinder, Linnea; Ramebäck, Henrik; Marie, Olivier; Ravat, Brice; Delaunay, François; Young, Emma; Blagojevic, Ned; Hester, James R; Thorogood, Gordon; Nelwamondo, Aubrey N; Ntsoane, Tshepo P; Roberts, Sarah K; Holliday, Kiel S

2018-01-01

This work presents the results for identification of chemical phases obtained by several laboratories as a part of an international nuclear forensic round-robin exercise. In this work powder X-ray diffraction (p-XRD) is regarded as the reference technique. Neutron diffraction produced a superior high-angle diffraction pattern relative to p-XRD. Requiring only small amounts of sample, µ-Raman spectroscopy was used for the first time in this context as a potentially complementary technique to p-XRD. The chemical phases were identified as pure UO 2 in two materials, and as a mixture of UO 2 , U 3 O 8 and an intermediate species U 3 O 7 in the third material.

Spin disorder in maghemite nanoparticles investigated using polarized neutrons and nuclear resonant scattering

DOE PAGES

Herlitschke, Marcus; Disch, Sabrina; Sergueev, I.; ...

2016-05-11

The manuscript reports the investigation of spin disorder in maghemite nanoparticles of different shape by a combination of polarized small-angle neutron scattering (SANSPOL) and nuclear forward scattering (NFS) techniques. Both methods are sensitive to magnetization on the nanoscale. SANSPOL allows for investigation of the particle morphology and spatial magnetization distribution and NFS extends this nanoscale information to the atomic scale, namely the orientation of the hyperfine field experienced by the iron nuclei. The studied nanospheres and nanocubes with diameters of 7.4nm and 10.6 nm, respectively, exhibit a significant spin disorder. This effect leads to a reduction of the magnetization tomore » 44% and 58% of the theoretical maghemite bulk value, observed consistently by both techniques.« less

Neutron scattering studies of molecular conformations in liquid crystal polymers

NASA Astrophysics Data System (ADS)

Noirez, L.; Moussa, F.; Cotton, J. P.; Keller, P.; Pépy, G.

1991-03-01

A comblike liquid crystal polymer (LPC) is a polymer on which mesogenic molecules have been grafted. It exhibits a succession of liquid crystal phases. Usually the equilibrium conformation of an ordinary polymeric chain corresponds to a maximum entropy, i.e., to an isotropic spherical coil. How does the backbone of a LCP behave in the nematic and smectic field? Small-angle neutron scattering may answer this question. Such measurements are presented here on four different polymers as a function of temperature. An anisotropy of the backbone conformation is found in all these studied compounds, much more pronounced in the smectic phase than in the nematic phase: the backbone spreads more or less perpendicularly to its hanging cores. A comparison with existing theories and a discussion of these results is outlined.

Spin disorder in maghemite nanoparticles investigated using polarized neutrons and nuclear resonant scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Herlitschke, Marcus; Disch, Sabrina; Sergueev, I.

The manuscript reports the investigation of spin disorder in maghemite nanoparticles of different shape by a combination of polarized small-angle neutron scattering (SANSPOL) and nuclear forward scattering (NFS) techniques. Both methods are sensitive to magnetization on the nanoscale. SANSPOL allows for investigation of the particle morphology and spatial magnetization distribution and NFS extends this nanoscale information to the atomic scale, namely the orientation of the hyperfine field experienced by the iron nuclei. The studied nanospheres and nanocubes with diameters of 7.4nm and 10.6 nm, respectively, exhibit a significant spin disorder. This effect leads to a reduction of the magnetization tomore » 44% and 58% of the theoretical maghemite bulk value, observed consistently by both techniques.« less

High yield neutron generators using the DD reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vainionpaa, J. H.; Harris, J. L.; Piestrup, M. A.

2013-04-19

A product line of high yield neutron generators has been developed at Adelphi technology inc. The generators use the D-D fusion reaction and are driven by an ion beam supplied by a microwave ion source. Yields of up to 5 Multiplication-Sign 10{sup 9} n/s have been achieved, which are comparable to those obtained using the more efficient D-T reaction. The microwave-driven plasma uses the electron cyclotron resonance (ECR) to produce a high plasma density for high current and high atomic ion species. These generators have an actively pumped vacuum system that allows operation at reduced pressure in the target chamber,more » increasing the overall system reliability. Since no radioactive tritium is used, the generators can be easily serviced, and components can be easily replaced, providing essentially an unlimited lifetime. Fast neutron source size can be adjusted by selecting the aperture and target geometries according to customer specifications. Pulsed and continuous operation has been demonstrated. Minimum pulse lengths of 50 {mu}s have been achieved. Since the generators are easily serviceable, they offer a long lifetime neutron generator for laboratories and commercial systems requiring continuous operation. Several of the generators have been enclosed in radiation shielding/moderator structures designed for customer specifications. These generators have been proven to be useful for prompt gamma neutron activation analysis (PGNAA), neutron activation analysis (NAA) and fast neutron radiography. Thus these generators make excellent fast, epithermal and thermal neutron sources for laboratories and industrial applications that require neutrons with safe operation, small footprint, low cost and small regulatory burden.« less

Morphological changes in the cellulose and lignin components of biomass occur at different stages of steam pretreatment

DOE PAGES

Pingali, Sai Venkatesh; O'Neill, Hugh Michael; Nishiyama, Yoshiharu; ...

2014-01-09

Morphological changes to the different components of lignocellulosic biomass were observed as they occurred during steam pretreatment by placing a pressure reaction cell in a neutron beam and collecting time-resolved neutron scattering data. Changes to cellulose morphology occurred mainly in the heating phase, whereas changes in lignin morphology occurred mainly in the holding and cooling phases. During the heating stage, water is irreversibly expelled from cellulose microfibrils as the elementary fibrils coalesce. During the holding phase lignin aggregates begin to appear and they increase in size most noticeably during the cooling phase. This experiment demonstrates the unique information that inmore » situ small angle neutron scattering studies of pretreatment can provide. This approach is potentially useful in optimizing the heating, holding and cooling stages of pretreatments to allow the exact size and nature of lignin aggregates to be controlled in order to enhance enzyme accessibility to cellulose and therefore the efficiency of biomass conversion.« less

Supercooling of water confined in reverse micelles

NASA Astrophysics Data System (ADS)

Spehr, T.; Frick, B.; Grillo, I.; Stühn, B.

2008-03-01

We report on the temperature dependence of the nanosecond-timescale dynamics of the ternary mixture water/AOT/oil with deuterated heptane, toluene or decane as the oil. Water-swollen reverse micelles as formed in such microemulsions allow us to investigate the freezing behaviour of water confined in a soft environment. We report here on the first neutron scattering studies in which the freezing of the confined water and of the oil is followed down to temperatures at which the whole system is frozen. We focus on studies of water confined in three different droplet sizes: by means of small-angle neutron scattering we have determined the radii to be 46, 18, and 7 Å for water to surfactant ratios ω = 40, 12, and 3. From elastic temperature scans by neutron backscattering we deduce a strong supercooling of water confined in the reverse swollen micelles which increases with decreasing droplet size. For the smallest droplets we find a supercooling of more than 45 K compared to bulk water.

Application of the BINS superheated drop detector spectrometer to the 9Be(p,xn) neutron energy spectrum determination

NASA Astrophysics Data System (ADS)

Di Fulvio, A.; Ciolini, R.; Mirzajani, N.; Romei, C.; d'Errico, F.; Bedogni, R.; Esposito, J.; Zafiropoulos, D.; Colautti, P.

2013-07-01

In the framework of TRASCO-BNCT project, a Bubble Interactive Neutron Spectrometer (BINS) device was applied to the characterization of the angle-and energy-differential neutron spectra generated by the 9Be(p,xn)reaction. The BINS spectrometer uses two superheated emulsion detectors, sequentially operated at different temperatures and thus provides a series of six sharp threshold responses, covering the 0.1-10 MeV neutron energy range. Spectrum unfolding of the data was performed by means of MAXED code. The obtained angle, energy-differential spectra were compared with those measured with a Bonner sphere spectrometer, a silicon telescope spectrometer and literature data.

Ambient neutron dose equivalent during proton therapy using wobbling scanning system: Measurements and calculations

NASA Astrophysics Data System (ADS)

Lin, Yung-Chieh; Lee, Chung-Chi; Chao, Tsi-Chian; Tsai, Hui-Yu

2017-11-01

Neutron production is a concern in proton therapy, particularly in scattering proton beam delivery systems. Despite this fact, little is known about the effects of secondary neutron exposure around wobbling scattered proton treatment nozzles. The objective of this study was to estimate the neutron dose level resulting from the use of a wobbling scattered proton treatment unit. We applied the Monte Carlo method for predict the ambient neutron dose equivalent, H*(10), per absorbed dose at the treatment isocenter, D, in the proton therapy center of Chang Gung Memorial Hospital, Linkou, Taiwan. For a 190-MeV proton beam, H* (10) / D values typically decreased with the distance from the isocenter, being 1.106 mSv/Gy at the isocenter versus 0.112 mSv/Gy at a distance of 150 cm from the isocenter. The H* (10) / D values generally decreased as the neutron receptors moved away from the isocenter, and increased when the angle from the initial beam axis increased. The ambient neutron dose equivalents were observed to be slightly lower in the direction of multileaf collimator movement. For radiation protection, the central axis of a proton-treated patient is suggested to be at the 0° angle of the beam. If the beam direction at the 90° angle is necessary, the patient axis is suggested to be along with the direction of MLC movement. Our study provides the neutron dose level and neutron energy fluence for the first wobbling proton system at the proton therapy center of Chang Gung Memorial Hospital.

Comprehensive approach to fast ion measurements in the beam-driven FRC

NASA Astrophysics Data System (ADS)

Magee, Richard; Smirnov, Artem; Onofri, Marco; Dettrick, Sean; Korepanov, Sergey; Knapp, Kurt; the TAE Team

2015-11-01

The C-2U experiment combines tangential neutral beam injection, edge biasing, and advanced recycling control to explore the sustainment of field-reversed configuration (FRC) plasmas. To study fast ion confinement in such advanced, beam-driven FRCs, a synergetic technique was developed that relies on the measurements of the DD fusion reaction products and the hybrid code Q2D, which treats the plasma as a fluid and the fast ions kinetically. Data from calibrated neutron and proton detectors are used in a complementary fashion to constrain the simulations: neutron detectors measure the volume integrated fusion rate to constrain the total number of fast ions, while proton detectors with multiple lines of sight through the plasma constrain the axial profile of fast ions. One application of this technique is the diagnosis of fast ion energy transfer and pitch angle scattering. A parametric numerical study was conducted, in which additional ad hoc loss and scattering terms of varying strengths were introduced in the code and constrained with measurement. Initial results indicate that the energy transfer is predominantly classical, while, in some cases, non-classical pitch angle scattering can be observed.

Inspection of 56Fe γ-Ray angular distributions as a function of incident neutron energy using optical model approaches

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vanhoy, J. R.; Ramirez, A. P.; Alcorn-Dominguez, D. K.

Neutron inelastic scattering cross sections measured directly through (n,n) or deduced from g-ray production cross sections following inelastic neutron scattering (n,n0) are a focus of basic and applied research at the University of Kentucky Accelerator Laboratory (www.pa.uky.edu/accelerator). For nuclear data applications, angle-integrated cross sections are desired over a wide range of fast neutron energies. Several days of experimental beam time are required for a data set at each incident neutron energy, which limits the number of angular distributions that can be measured in a reasonable amount of time. Approximations can be employed to generate cross sections with a higher energymore » resolution, since at 125°, the a 2P 2 term of the Legendre expansion is identically zero and the a 4P 4 is assumed to be very small. Provided this assumption is true, a single measurement at 125o would produce the g-ray production cross section. Finally, this project tests these assumptions and energy dependences using the codes CINDY/SCAT and TALYS/ECIS06/SCAT. It is found that care must be taken when interpreting g-ray excitation functions as cross sections when the incident neutron energy is <1000 keV above threshold or before the onset of feeding.« less

Inspection of 56Fe γ-Ray angular distributions as a function of incident neutron energy using optical model approaches

DOE PAGES

Vanhoy, J. R.; Ramirez, A. P.; Alcorn-Dominguez, D. K.; ...

2017-09-13

Neutron inelastic scattering cross sections measured directly through (n,n) or deduced from g-ray production cross sections following inelastic neutron scattering (n,n0) are a focus of basic and applied research at the University of Kentucky Accelerator Laboratory (www.pa.uky.edu/accelerator). For nuclear data applications, angle-integrated cross sections are desired over a wide range of fast neutron energies. Several days of experimental beam time are required for a data set at each incident neutron energy, which limits the number of angular distributions that can be measured in a reasonable amount of time. Approximations can be employed to generate cross sections with a higher energymore » resolution, since at 125°, the a 2P 2 term of the Legendre expansion is identically zero and the a 4P 4 is assumed to be very small. Provided this assumption is true, a single measurement at 125o would produce the g-ray production cross section. Finally, this project tests these assumptions and energy dependences using the codes CINDY/SCAT and TALYS/ECIS06/SCAT. It is found that care must be taken when interpreting g-ray excitation functions as cross sections when the incident neutron energy is <1000 keV above threshold or before the onset of feeding.« less

Inspection of 56Fe γ-Ray angular distributions as a function of incident neutron energy using optical model approaches

NASA Astrophysics Data System (ADS)

Vanhoy, J. R.; Ramirez, A. P.; Alcorn-Dominguez, D. K.; Hicks, S. F.; Peters, E. E.; McEllistrem, M. T.; Mukhopadhyay, S.; Yates, S. W.

2017-09-01

Neutron inelastic scattering cross sections measured directly through (n,n) or deduced from γ-ray production cross sections following inelastic neutron scattering (n,n'γ) are a focus of basic and applied research at the University of Kentucky Accelerator Laboratory (www.pa.uky.edu/accelerator). For nuclear data applications, angle-integrated cross sections are desired over a wide range of fast neutron energies. Several days of experimental beam time are required for a data set at each incident neutron energy, which limits the number of angular distributions that can be measured in a reasonable amount of time. Approximations can be employed to generate cross sections with a higher energy resolution, since at 125o, the a2P2 term of the Legendre expansion is identically zero and the a4P4 is assumed to be very small. Provided this assumption is true, a single measurement at 125o would produce the γ-ray production cross section. This project tests these assumptions and energy dependences using the codes CINDY/SCAT and TALYS/ECIS06/SCAT. It is found that care must be taken when interpreting γ-ray excitation functions as cross sections when the incident neutron energy is < 1000 keV above threshold or before the onset of feeding.

The physics of photons and neutrons with applications of deuterium labeling methods to polymers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wignall, G.D.

1986-12-01

Over the past decade small-angle neutron scattering (SANS), has found numerous applications in the fields of biology, polymer science, physical chemistry, materials science, metallurgy, colloids, and solid state physics. A number of excellent references are available which contain basic neutron scattering theory though these text books reflect the origins of the technique and the examples are largely drawn from physics e.g., single crystals, simple liquids, monatomic gases, liquid metals, magnetic materials, etc. in view of the large numbers of nonspecialists who are increasingly using neutron scattering, the need has become apparent for presentations which can provide rapid access to themore » method without unnecessary detail and mathematical rigor. This article is meant to serve as a general introduction to the symposium ''Scattering Deformation and Fracture in Polymers,'' and is intended to aid potential users who have a general scientific background, but no specialist knowledge of scattering, to apply the technique to provide new information in areas of their own particular interests. In view of space limitations, the general theory will be given in the case for neutron scattering and analogies and differences with photon scattering (x-rays) will be pointed out at the appropriate point. 90 refs., 6 figs.« less

Suggestions for improving the efficiency of ground-based neutron monitors for detecting solar neutrons

NASA Technical Reports Server (NTRS)

Iucci, N.; Parisi, M.; Signorini, C.; Storini, M.; Villoresi, G.

1985-01-01

On the occasion of the June 3, 1982 intense gamma-ray solar flare a significant increase in counting rate due to solar neutrons was observed by the neutron monitors of Junsfraujoch and Lomnicky Stit located at middle latitudes and high altitudes. In spite of a larger detector employed and of the smaller solar zenith angle, the amplitude of the same event observed at Rome was much smaller and the statistical fluctuations of the salactic cosmic ray background higher than the ones registered at the two mountain stations, because of the greater atmospheric depth at which the Rome monitor is located. The effeciency for detecting a solar neutron event by a NM-64 monitor as a function of the Sun zenith angle, atmospheric depth and threshold rigidity of the station was studied.

Long wavelength undulations dominate dynamics in large surfactant membrane patches

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lipfert, Frederik; Holderer, Olaf; Frielinghaus, Henrich

2014-12-03

In this study, by exposing microemulsions to small (80 nm diameter) and large (500 nm) disk shaped clay particles we were able to show the presence of long wavelength undulations that only occur for large membrane patches. A combination of small angle neutron scattering (SANS) and neutron spin echo (NSE) experiments have been applied to study microemulsions. These, consisting of D 2O, d-decane and the surfactant C 10E 4, were used in connection with Laponite (small) and Nanofil (large) clay. To our knowledge our experiments show for the first time that the clay platelets induce lamellar ordering adjacent to themore » clay discs in the otherwise bicontinuous microemulsion. This is due to the fact that in purely structural investigations, radial averaging smears out the signature of the lamellar phase. For thermodynamically fluctuating membranes near interfaces the theory of Seifert predicts a cross-over of the dispersion relationship from k 2 to a k 3-dependence. Lastly, with the correlation length of the membrane patches being confined by the dimension of the clay platelets we were able to show that this in fact takes place but is only present for the larger Nanofil particles.« less

Forward multiple scattering corrections as function of detector field of view

NASA Astrophysics Data System (ADS)

Zardecki, A.; Deepak, A.

1983-06-01

The theoretical formulations are given for an approximate method based on the solution of the radiative transfer equation in the small angle approximation. The method is approximate in the sense that an approximation is made in addition to the small angle approximation. Numerical results were obtained for multiple scattering effects as functions of the detector field of view, as well as the size of the detector's aperture for three different values of the optical depth tau (=1.0, 4.0 and 10.0). Three cases of aperture size were considered--namely, equal to or smaller or larger than the laser beam diameter. The contrast between the on-axis intensity and the received power for the last three cases is clearly evident.

Neutron Scattering Studies on Large Length Scale Sample Structures

NASA Astrophysics Data System (ADS)

Feng, Hao

Neutron scattering can be used to study structures of matter. Depending on the interested sample properties, different scattering techniques can be chosen. Neutron reflectivity is more often used to detect in-depth profile of layered structures and the interfacial roughness while transmission is more sensitive to sample bulk properties. Neutron Reflectometry (NR) technique, one technique in neutron reflectivity, is first discussed in this thesis. Both specular reflectivity and the first order Bragg intensity were measured in the NR experiment with a diffraction grating in order to study the in-depth and the lateral structure of a sample (polymer) deposited on the grating. However, the first order Bragg intensity solely is sometimes inadequate to determine the lateral structure and high order Bragg intensities are difficult to measure using traditional neutron scattering techniques due to the low brightness of the current neutron sources. Spin Echo Small Angle Neutron Scattering (SESANS) technique overcomes this resolution problem by measuring the Fourier transforms of all the Bragg intensities, resulting in measuring the real-space density correlations of samples and allowing the accessible length scale from few-tens of nanometers to several microns. SESANS can be implemented by using two pairs of magnetic Wollaston prims (WP) and the accessible length scale is proportional to the magnetic field intensity in WPs. To increase the magnetic field and thus increase the accessible length scale, an apparatus named Superconducting Wollaston Prisms (SWP) which has a series of strong, well-defined shaped magnetic fields created by superconducting coils was developed in Indiana University in 2016. Since then, various kinds of optimization have been implemented, which are addressed in this thesis. Finally, applications of SWPs in other neutron scattering techniques like Neutron Larmor Diffraction (NLD) are discussed.

Initial characterization of mudstone nanoporosity with small angle neutron scattering using caprocks from carbon sequestration sites.

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCray, John; Navarre-Sitchler, Alexis; Mouzakis, Katherine

Geological carbon sequestration relies on the principle that CO{sub 2} injected deep into the subsurface is unable to leak to the atmosphere. Structural trapping by a relatively impermeable caprock (often mudstone such as a shale) is the main trapping mechanism that is currently relied on for the first hundreds of years. Many of the pores of the caprock are of micrometer to nanometer scale. However, the distribution, geometry and volume of porosity at these scales are poorly characterized. Differences in pore shape and size can cause variation in capillary properties and fluid transport resulting in fluid pathways with different capillarymore » entry pressures in the same sample. Prediction of pore network properties for distinct geologic environments would result in significant advancement in our ability to model subsurface fluid flow. Specifically, prediction of fluid flow through caprocks of geologic CO{sub 2} sequestration reservoirs is a critical step in evaluating the risk of leakage to overlying aquifers. The micro- and nanoporosity was analyzed in four mudstones using small angle neutron scattering (SANS). These mudstones are caprocks of formations that are currently under study or being used for carbon sequestration projects and include the Marine Tuscaloosa Group, the Lower Tuscaloosa Group, the upper and lower shale members of the Kirtland Formation, and the Pennsylvanian Gothic shale. Total organic carbon varies from <0.3% to 4% by weight. Expandable clay contents range from 10% to {approx}40% in the Gothic shale and Kirtland Formation, respectively. Neutrons effectively scatter from interfaces between materials with differing scattering length density (i.e. minerals and pores). The intensity of scattered neutrons, I(Q), where Q is the scattering vector, gives information about the volume of pores and their arrangement in the sample. The slope of the scattering data when plotted as log I(Q) vs. log Q provides information about the fractality or geometry of the pore network. Results from this study, combined with high-resolution TEM imaging, provide insight into the differences in volume and geometry of porosity between these various mudstones.« less

Photodetection Characterization of SiPM Technologies for their Application in Scintillator based Neutron Detectors

NASA Astrophysics Data System (ADS)

Kumar, S.; Durini, D.; Degenhardt, C.; van Waasen, S.

2018-01-01

Small-angle neutron scattering (SANS) experiments have become one of the most important techniques in the investigation of the properties of material on the atomic scale. Until 2001, nearly exclusively 3He-based detectors were used for neutron detection in these experiments, but due to the scarcity of 3He and its steeply rising price, researchers started to look for suitable alternatives. Scintillation based solid state detectors appeared as a prominent alternative. Silicon photomultipliers (SiPM), having single photon resolution, lower bias voltages compared to photomultiplier tubes (PMT), insensitivity to magnetic fields, low cost, possibility of modular design and higher readout rates, have the potential of becoming a photon detector of choice in scintillator based neutron detectors. The major concerns for utilizing the SiPM technology in this kind of applications are the increase in their noise performance and the decrease in their photon detection efficiency (PDE) due to direct exposure to neutrons. Here, a detailed comparative analysis of the PDE performance in the range between UV and NIR parts of the spectra for three different SiPM technologies, before and after irradiation with cold neutrons, has been carried out. For this investigation, one digital and two analog SiPM arrays were irradiated with 5Å wavelength cold neutrons and up to a dose of 6×1012 n/cm2 at the KWS-1 instrument of the Heinz Maier-Leibnitz Zentrum (MLZ) in Garching, Germany.

Infrastructure development for radioactive materials at the NSLS-II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sprouster, D. J.; Weidner, R.; Ghose, S. K.

2018-02-01

The X-ray Powder Diffraction (XPD) Beamline at the National Synchrotron Light Source-II is a multipurpose instrument designed for high-resolution, high-energy X-ray scattering techniques. In this article, the capabilities, opportunities and recent developments in the characterization of radioactive materials at XPD are described. The overarching goal of this work is to provide researchers access to advanced synchrotron techniques suited to the structural characterization of materials for advanced nuclear energy systems. XPD is a new beamline providing high photon flux for X-ray Diffraction, Pair Distribution Function analysis and Small Angle X-ray Scattering. The infrastructure and software described here extend the existing capabilitiesmore » at XPD to accommodate radioactive materials. Such techniques will contribute crucial information to the characterization and quantification of advanced materials for nuclear energy applications. We describe the automated radioactive sample collection capabilities and recent X-ray Diffraction and Small Angle X-ray Scattering results from neutron irradiated reactor pressure vessel steels and oxide dispersion strengthened steels.« less

Manufacturing and characterization of Ni-free N-containing ODS austenitic alloy

NASA Astrophysics Data System (ADS)

Mori, A.; Mamiya, H.; Ohnuma, M.; Ilavsky, J.; Ohishi, K.; Woźniak, Jarosław; Olszyna, A.; Watanabe, N.; Suzuki, J.; Kitazawa, H.; Lewandowska, M.

2018-04-01

Ni-free N-containing oxide dispersion strengthened (ODS) austenitic alloys were manufactured by mechanical alloying (MA) followed by spark plasma sintering (SPS). The phase evolutions during milling under a nitrogen atmosphere and after sintering were studied by X-ray diffraction (XRD). Transmission electron microcopy (TEM) and alloy contrast variation analysis (ACV), including small-angle neutron scattering (SANS) and ultra-small-angle X-ray scattering (USAXS), revealed the existence of nanoparticles with a diameter of 3-51 nm for the samples sintered at 950 °C. Sintering at 1000 °C for 5 and 15 min caused slight growth and a significant coarsening of the nanoparticles, up to 70 nm and 128 nm, respectively. The ACV analysis indicated the existence of two populations of Y2O3, ε-martensite and MnO. The dispersive X-ray spectrometry (EDS) confirmed two kinds of nanoparticles, Y2O3 and MnO. The material was characterized by superior micro-hardness, of above 500 HV0.1.

Spatial distribution of intra-molecular water and polymeric components in polyelectrolyte dendrimers revealed by small angle scattering investigations

NASA Astrophysics Data System (ADS)

Wu, Bin; Li, Xin; Do, Changwoo; Kim, Tae-Hwan; Shew, Chwen-Yang; Liu, Yun; Yang, Jun; Hong, Kunlun; Porcar, Lionel; Chen, Chun-Yu; Liu, Emily L.; Smith, Gregory S.; Herwig, Kenneth W.; Chen, Wei-Ren

2011-10-01

An experimental scheme using contrast variation small angle neutron scattering technique is developed to investigate the structural characteristics of amine-terminated poly(amidoamine) dendrimers solutions. Using this methodology, we present the dependence of both the intra-dendrimer water and the polymer distribution on molecular protonation, which can be precisely adjusted by tuning the pH of the solution. Assuming spherical symmetry of the spatial arrangement of the constituent components of dendrimer, and that the atomic ratio of hydrogen-to-deuterium for the solvent residing within the cavities of dendrimer is identical to that for the solvent outside the dendrimer, the intra-dendrimer water distribution along the radial direction is determined. Our result clearly reveals an outward relocation of the peripheral groups, as well as enhanced intra-dendrimer hydration, upon increasing the molecular protonation and, therefore, allows the determination of segmental backfolding in a quantitative manner. The connection between these charge-induced structural changes and our recently observed progressively active segmental dynamics is also discussed.

Resolution of ab initio shapes determined from small-angle scattering.

PubMed

Tuukkanen, Anne T; Kleywegt, Gerard J; Svergun, Dmitri I

2016-11-01

Spatial resolution is an important characteristic of structural models, and the authors of structures determined by X-ray crystallography or electron cryo-microscopy always provide the resolution upon publication and deposition. Small-angle scattering of X-rays or neutrons (SAS) has recently become a mainstream structural method providing the overall three-dimensional structures of proteins, nucleic acids and complexes in solution. However, no quantitative resolution measure is available for SAS-derived models, which significantly hampers their validation and further use. Here, a method is derived for resolution assessment for ab initio shape reconstruction from scattering data. The inherent variability of the ab initio shapes is utilized and it is demonstrated how their average Fourier shell correlation function is related to the model resolution. The method is validated against simulated data for proteins with known high-resolution structures and its efficiency is demonstrated in applications to experimental data. It is proposed that henceforth the resolution be reported in publications and depositions of ab initio SAS models.

Resolution of ab initio shapes determined from small-angle scattering

PubMed Central

Tuukkanen, Anne T.; Kleywegt, Gerard J.; Svergun, Dmitri I.

2016-01-01

Spatial resolution is an important characteristic of structural models, and the authors of structures determined by X-ray crystallography or electron cryo-microscopy always provide the resolution upon publication and deposition. Small-angle scattering of X-rays or neutrons (SAS) has recently become a mainstream structural method providing the overall three-dimensional structures of proteins, nucleic acids and complexes in solution. However, no quantitative resolution measure is available for SAS-derived models, which significantly hampers their validation and further use. Here, a method is derived for resolution assessment for ab initio shape reconstruction from scattering data. The inherent variability of the ab initio shapes is utilized and it is demonstrated how their average Fourier shell correlation function is related to the model resolution. The method is validated against simulated data for proteins with known high-resolution structures and its efficiency is demonstrated in applications to experimental data. It is proposed that henceforth the resolution be reported in publications and depositions of ab initio SAS models. PMID:27840683

Infrastructure development for radioactive materials at the NSLS-II

DOE PAGES

Sprouster, David J.; Weidner, R.; Ghose, S. K.; ...

2017-11-04

The X-ray Powder Diffraction (XPD) Beamline at the National Synchrotron Light Source-II is a multipurpose instrument designed for high-resolution, high-energy X-ray scattering techniques. In this paper, the capabilities, opportunities and recent developments in the characterization of radioactive materials at XPD are described. The overarching goal of this work is to provide researchers access to advanced synchrotron techniques suited to the structural characterization of materials for advanced nuclear energy systems. XPD is a new beamline providing high photon flux for X-ray Diffraction, Pair Distribution Function analysis and Small Angle X-ray Scattering. The infrastructure and software described here extend the existing capabilitiesmore » at XPD to accommodate radioactive materials. Such techniques will contribute crucial information to the characterization and quantification of advanced materials for nuclear energy applications. Finally, we describe the automated radioactive sample collection capabilities and recent X-ray Diffraction and Small Angle X-ray Scattering results from neutron irradiated reactor pressure vessel steels and oxide dispersion strengthened steels.« less

Accreting X-ray pulsar atmospheres heated by Coulomb deceleration of protons

NASA Technical Reports Server (NTRS)

Meszaros, P.; Harding, A. K.; Kirk, J. G.; Galloway, D. J.

1983-01-01

Results are presented from detailed self-consistent models of accreting magnetized neutron star atmospheres, heated by the gradual deceleration of infalling protons via Coulomb encounters. The temperature and density gradients are calculated assuming momentum and energy balance, coupled with the radiative transfer for two polarizations. The cyclotron resonance effects were treated approximately. These models are characterized by power-law energy spectra, with single pulses at higher frequencies and multiple pulses at lower ones for some aspect angles, as well as a phase-dependent spectral index.

Study of DD Neutrons and their Transmission in Iron Spheres

NASA Astrophysics Data System (ADS)

Dhakal, Sushil

The Deuterium-Deuteron (DD) reaction has been used as a neutron source to study the transport of neutrons in natural iron. The scattering targets are used in the form of spheres and the neutron transmission measurement has been done at 7-MeV incident deuteron beam energy. The purpose of this study is to test the elastic and non-elastic neutron scattering cross sections for iron in the ENDF/B-VII data library, as some indications about the inaccuracy of those cross sections have been found from previous studies. The experiment has been carried out using the 4.5-MV tandem accelerator at Edwards Accelerator Laboratory at Ohio University, Athens, Ohio. The DD source reaction has been measured at 5- and 7-MeV deuteron beam energy. The D(d,n)3He monoenergetic reaction cross section has been measured from 0° to 135° at both 5- and 7-MeV beam energy and the D(d,np)D breakup reaction cross section has been measured up to 60° laboratory angles at 7-MeV beam energy. The target used is a deuterium gas cell of 3-cm length at approximately 2 atmosphere absolute pressure. The neutron energy is determined using the time of flight method. A NE213 liquid scintillation detector is used for neutron detection and the thick-target 27Al(d,n) reaction is used for the determination of neutron detector efficiency. The monoenergetic reaction cross section has been found to be in reasonable agreement with previous evaluations. The neutron transmission studies through iron spheres is done using two natural iron spheres with thicknesses of 3 and 8 cm. The DD source measurement (sphere-off) were repeated for the transmission studies and the neutron source was covered with the spheres for the transmission measurements. The experimental transmitted neutron spectrum is compared with the calculation done using Monte Carlo simulation code MCNP6.1 developed by Los Alamos National Laboratory. MCNP uses ENDF/B-VII.1 evaluated iron cross section for the simulation. The calculated and experimental neutron spectrum in time of flight has been compared at various laboratory angles from 0° to 150°. The calculated and experimental neutron time of flight spectra for neutron counts under the main peak (D(d,n)3He peak region) agree within the error bars for angles 90°, 135° and 150° for larger sphere (8-cm thickness) whereas they agree for all angles 0°, 15°, 30°, 45°, 90°, 135° and 150° for smaller sphere (3-cm thickness). However, the calculated and experimental neutron spectra show a difference of 12%, 11.80%, 16.85% and 19.67% in the main peak neutron counts for larger sphere at angles 0°, 15°, 30° and 45° respectively which can not be accounted for by the systematic uncertainty in our measurement (the 5% uncertainty in the target thickness and the 5% efficiency systematics are the main contributors). The sphere-off to on ratios for the calculation and the experiment also show a significant difference at those angles and this comparison is more robust as it avoids most of the systematic uncertainties including the efficiency. These differences likely come from the uncertainty in the ENDF cross section used. To test the ENDF cross section sensitivity, elastic cross section is decreased by 10% and inelastic cross section is increased by 14.78% in the energy range 7.2 to 11 MeV which corresponds to the energy range of the monoenergetic neutron peak for angles between 0° to 45°. This cross section modification keeps the total cross section constant on average in that energy range as the total in the library is assumed to be correct. This modification reduces the difference between the calculation and the experiment and brings it in agreement within the error bars. This result implies the possibility of underestimation of inelastic cross section in the above energy range and hence the overestimation of elastic cross section in the ENDF library.

New generation high performance in situ polarized 3He system for time-of-flight beam at spallation sources.

PubMed

Jiang, C Y; Tong, X; Brown, D R; Glavic, A; Ambaye, H; Goyette, R; Hoffmann, M; Parizzi, A A; Robertson, L; Lauter, V

2017-02-01

Modern spallation neutron sources generate high intensity neutron beams with a broad wavelength band applied to exploring new nano- and meso-scale materials from a few atomic monolayers thick to complicated prototype device-like systems with multiple buried interfaces. The availability of high performance neutron polarizers and analyzers in neutron scattering experiments is vital for understanding magnetism in systems with novel functionalities. We report the development of a new generation of the in situ polarized 3 He neutron polarization analyzer for the Magnetism Reflectometer at the Spallation Neutron Source at Oak Ridge National Laboratory. With a new optical layout and laser system, the 3 He polarization reached and maintained 84% as compared to 76% in the first-generation system. The polarization improvement allows achieving the transmission function varying from 50% to 15% for the polarized neutron beam with the wavelength band of 2-9 Angstroms. This achievement brings a new class of experiments with optimal performance in sensitivity to very small magnetic moments in nano systems and opens up the horizon for its applications.

Morphological Study of Poly(vinylbenzyl chloride)-Grafted Poly(ethylene-co-tetrafluoroethylene) [ETFE-g-PVBC] Films Using Small-Angle Neutron Scattering Analysis.

PubMed

Song, J M; Ko, B S; Sohn, J Y; Shin, J

2016-06-01

In this study, the effect of degree of the grafting and crosslinking on the morphology of the crystalline domain in poly(vinylbenzyl chloride)-grafted poly(ethylene-co-tetrafluoroethylene) [ETFE-g-PVBC] films was investigated using a SANS (small-angle neutron scattering) analysis. The grafted films can be used as a precursor for ion-exchange membrane. ETFE-g-PVBC films with various degrees of cross-linking were prepared by a simultaneous irradiation grafting of vinylbenzyl chloride (VBC) and divinylbenzene (DVB) onto an ETFE film. The SEM-EDX (scanning electron microscopy-energy dispersive X-ray spectroscopy) results of a cross-sectional distribution of ETFE-g-PVBC films showed that the chlorine atoms were well-distributed throughout the films. SANS profiles of the PVBC-grafted films in the absence of a DVB crosslinker showed that the crystalline domain peaks were observed and the peak maximum position shifted significantly from 0.032 Å-(-1) to 0.02 Å(-1) with an increase in the degree of grafting. However, peak maximum positions of the PVBC-grafted films in the presence of a DVB crosslinker shifted slightly from 0.02 Å(-1) to 0.024 Å(-1) with an increase in the amount of DVB monomer at same degree of grafting. These results indicate that the degree of grafting and crosslinking affect the morphology of the crystalline domain in the ETFE-g-PVBC films.

Small-Angle Neutron Scattering Reveals pH-Dependent Conformational Changes in Trichoderma reesei Cellobiohydrolase I: Implications for Enzymatic Activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pingali, Sai Venkatesh; O'Neill, Hugh Michael; McGaughey, Joseph

2011-01-01

Cellobiohydrolase I (Cel7A) of the fungus Trichoderma reesei (now classified as an anamorph of Hypocrea jecorina) hydrolyzes crystalline cellulose to soluble sugars, making it of key interest for producing fermentable sugars from biomass for biofuel production. The activity of the enzyme is pH-dependent, with its highest activity occurring at pH 4 5. To probe the response of the solution structure of Cel7A to changes in pH, we measured small angle neutron scattering of it in a series of solutions having pH values of 7.0, 6.0, 5.3, and 4.2. As the pH decreases from 7.0 to 5.3, the enzyme structure remainsmore » well defined, possessing a spatial differentiation between the cellulose binding domain and the catalytic core that only changes subtly. At pH 4.2, the solution conformation of the enzyme changes to a structure that is intermediate between a properly folded enzyme and a denatured, unfolded state, yet the secondary structure of the enzyme is essentially unaltered. The results indicate that at the pH of optimal activity, the catalytic core of the enzyme adopts a structure in which the compact packing typical of a fully folded polypeptide chain is disrupted and suggest that the increased range of structures afforded by this disordered state plays an important role in the increased activity of Cel7A through conformational selection.« less

Structure in the Proton and the Neutron

DOE R&D Accomplishments Database

Hofstadter, R.

1958-06-01

A survey of the recent work on the structures of the proton and the neutron carried out by high-energy electron-scattering methods is presented. Early work established finite size effects in the proton and led to information about the charge and magnetic density distributions in the proton. The rms size was established to be close to (0.77 plus or minus 0.10) x 10{sup -13} cm, and the density distributions of charge and anomalous magnetic moment were shown to be approximately of the same shape. The form factors could be described in terms of several alternative models given, for example, by an exponential, gaussian, hollow exponential, hollow gaussian, etc., distribution of densities. Many other shapes were excluded by the experimental data. Recent work by Bumiller and Hofstadter now fixes one among these models that is appropriate to the proton and provides an extremely good fit at all angles between energies of 200 and 650 Mev. The new evidence clearly favors the exponential model with rms radius (0.80 plus or minus 0.04) 10{sup -13} cm. Recent studies of the proton have attempted to answer the question: how closely similar are the charge and magnetic form factors? This work now shows that the distributions have the same sizes and shapes to within 10 per cent, and each distribution is given very closely by the exponential model described above with radius (0.80 plus or minus 0.04) x 10{sup -13}. Certain other similar models will be discussed. Early work on the inelastic continuum in the deuteron established that the neutron's magnetic structure was extended and not a point. It was further shown that the neutron's size was approximately the same as that of the proton. This work has recently been extended by Yearian and Hofstadter to a determination of the variation of the neutron's magnetic form factor over the range where the proton's form factor is known. The new results show: (1) the neutron is not a point, (2) the neutron's magnetic structure has a size lying between the limits 0.61 x 10{sup -13} cm and 0.80 x 10{sup -13} cm. The first value (0.61 x 10{sup -13} cm) is determined by examining the total deuteron electro-disintegration cross section at a given angle and incident energy and comparing this cross section with that of the free proton under the same conditions. The second value (0.80 x 10{sup -13} cm) is found by examining the peak of the deuteron electro-disintegration cross section. Because of possible contributions to the total cross section by mesonic exchange effects, the second method is believed to be slightly more accurate. The neutron size is, therefore, approximately (0.70 plus or minus 0.10) x 10{sup -13} cm and probably the larger size 0.90 x 10{sup -13} cm is correct. Thus the magnetic clouds of the neutron and proton are closely the same. The bearing of these results on the validity of electrodynamics is discussed. Because of the small radius implied by the neutron-electron experiments, there is an anomaly between the neutron and the proton. This is represented by the small charge radius for the neutron and the much larger radius of the proton. Additional information of the structure of the deuteron and on the production of pions by electrons is also furnished by the same experiments and will be discussed at the meeting. (auth)

A Structural Study of CESA1 Catalytic Domain of Arabidopsis Cellulose Synthesis Complex: Evidence for CESA Trimers.

PubMed

Vandavasi, Venu Gopal; Putnam, Daniel K; Zhang, Qiu; Petridis, Loukas; Heller, William T; Nixon, B Tracy; Haigler, Candace H; Kalluri, Udaya; Coates, Leighton; Langan, Paul; Smith, Jeremy C; Meiler, Jens; O'Neill, Hugh

2016-01-01

A cellulose synthesis complex with a "rosette" shape is responsible for synthesis of cellulose chains and their assembly into microfibrils within the cell walls of land plants and their charophyte algal progenitors. The number of cellulose synthase proteins in this large multisubunit transmembrane protein complex and the number of cellulose chains in a microfibril have been debated for many years. This work reports a low resolution structure of the catalytic domain of CESA1 from Arabidopsis (Arabidopsis thaliana; AtCESA1CatD) determined by small-angle scattering techniques and provides the first experimental evidence for the self-assembly of CESA into a stable trimer in solution. The catalytic domain was overexpressed in Escherichia coli, and using a two-step procedure, it was possible to isolate monomeric and trimeric forms of AtCESA1CatD. The conformation of monomeric and trimeric AtCESA1CatD proteins were studied using small-angle neutron scattering and small-angle x-ray scattering. A series of AtCESA1CatD trimer computational models were compared with the small-angle x-ray scattering trimer profile to explore the possible arrangement of the monomers in the trimers. Several candidate trimers were identified with monomers oriented such that the newly synthesized cellulose chains project toward the cell membrane. In these models, the class-specific region is found at the periphery of the complex, and the plant-conserved region forms the base of the trimer. This study strongly supports the "hexamer of trimers" model for the rosette cellulose synthesis complex that synthesizes an 18-chain cellulose microfibril as its fundamental product. © 2016 American Society of Plant Biologists. All Rights Reserved.

A Structural Study of CESA1 Catalytic Domain of Arabidopsis Cellulose Synthesis Complex: Evidence for CESA Trimers1

PubMed Central

Zhang, Qiu; Petridis, Loukas; Nixon, B. Tracy; Haigler, Candace H.; Kalluri, Udaya; Coates, Leighton; Smith, Jeremy C.; Meiler, Jens

2016-01-01

A cellulose synthesis complex with a “rosette” shape is responsible for synthesis of cellulose chains and their assembly into microfibrils within the cell walls of land plants and their charophyte algal progenitors. The number of cellulose synthase proteins in this large multisubunit transmembrane protein complex and the number of cellulose chains in a microfibril have been debated for many years. This work reports a low resolution structure of the catalytic domain of CESA1 from Arabidopsis (Arabidopsis thaliana; AtCESA1CatD) determined by small-angle scattering techniques and provides the first experimental evidence for the self-assembly of CESA into a stable trimer in solution. The catalytic domain was overexpressed in Escherichia coli, and using a two-step procedure, it was possible to isolate monomeric and trimeric forms of AtCESA1CatD. The conformation of monomeric and trimeric AtCESA1CatD proteins were studied using small-angle neutron scattering and small-angle x-ray scattering. A series of AtCESA1CatD trimer computational models were compared with the small-angle x-ray scattering trimer profile to explore the possible arrangement of the monomers in the trimers. Several candidate trimers were identified with monomers oriented such that the newly synthesized cellulose chains project toward the cell membrane. In these models, the class-specific region is found at the periphery of the complex, and the plant-conserved region forms the base of the trimer. This study strongly supports the “hexamer of trimers” model for the rosette cellulose synthesis complex that synthesizes an 18-chain cellulose microfibril as its fundamental product. PMID:26556795

A Structural Study of CESA1 Catalytic Domain of Arabidopsis Cellulose Synthesis Complex: Evidence for CESA Trimers

DOE PAGES

Vandavasi, Venu Gopal; Putnam, Daniel K.; Zhang, Qiu; ...

2015-11-10

In a cellulose synthesis complex a "rosette" shape is responsible for the synthesis of cellulose chains and their assembly into microfibrils within the cell walls of land plants and their charophyte algal progenitors. The number of cellulose synthase proteins in this large multisubunit transmembrane protein complex and the number of cellulose chains in a microfibril have been debated for many years. Our work reports a low resolution structure of the catalytic domain of CESA1 from Arabidopsis (Arabidopsis thaliana; AtCESA1CatD) determined by small-angle scattering techniques and provides the first experimental evidence for the self-assembly of CESA into a stable trimer inmore » solution. The catalytic domain was overexpressed in Escherichia coli, and using a two-step procedure, it was possible to isolate monomeric and trimeric forms of AtCESA1CatD. Moreover, the conformation of monomeric and trimeric AtCESA1CatD proteins were studied using small-angle neutron scattering and small-angle x-ray scattering. A series of AtCESA1CatD trimer computational models were compared with the small-angle x-ray scattering trimer profile to explore the possible arrangement of the monomers in the trimers. Several candidate trimers were identified with monomers oriented such that the newly synthesized cellulose chains project toward the cell membrane. In these models, the class-specific region is found at the periphery of the complex, and the plant-conserved region forms the base of the trimer. Finally, this study strongly supports the "hexamer of trimers" model for the rosette cellulose synthesis complex that synthesizes an 18-chain cellulose microfibril as its fundamental product.« less

POLARIZATION OF NEUTRONS BY THE STRIPPING REACTION C$sup 12$(d,n)N$sup 1$$sup 3$ (in French)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Budzanowski, A.; Grotowski, K.; Niewodniczanski, H.

1960-05-01

The polarization of neutrcns emitted from the stripping reaction C/sup 12/(d,n)N/sup 13/ hns been investigated at the reaction angle was / sub lab/ = 15 tained and deuteron energy E/sub d/ = 12.9 Mev. The polarization of neutrons connected with the 3.56 Mev energy level in N/sup 13/ nucleus was found to be --(0.39 combination rat 0.11). Also some general remarks concerning the preliminary results of the polarization of neutrons at the reaction angles 30 tained , 45 tained , and 60 tained are given. (auth)

Neutron Time-of-Flight Diffractometer HIPPO at LANSCE

NASA Astrophysics Data System (ADS)

Vogel, Sven; Williams, Darrick; Zhao, Yusheng; Bennett, Kristin; von Dreele, Bob; Wenk, Hans-Rudolf

2004-03-01

The High-Pressure Preferred Orientation (HIPPO) neutron diffractometer is the first third-generation neutron time-of-flight powder diffractometer to be constructed in the United States. It produces extremely high intensity by virtue of a short (9 m) initial flight path on a high intensity water moderator and 1380 3He detector tubes covering 4.5 m2 of detector area from 10' to 150' in scattering angles. HIPPO was designed and manufactured as a joint effort between LANSCE and University of California with the goals of attaining world-class science and making neutron powder diffractometry an accessible and available tool to the national user community. Over two decades of momentum transfer are available (0.1-30 A-1) to support studies of amorphous solids; magnetic diffraction; small crystalline samples; and samples subjected to extreme environments such as temperature, pressure, or magnetic fields. The exceptionally high data rates of HIPPO also make it useful for time-resolved studies. In addition to the standard ancillary equipment (100-position sample/texture changer, closed-cycle He refrigerator, furnace), HIPPO has unique high-pressure cells capable of achieving pressures of 30 GPA at ambient and high (2000 K) temperature with samples up to 100 mm3 in volume.

A Computational Approach for Modeling Neutron Scattering Data from Lipid Bilayers

DOE PAGES

Carrillo, Jan-Michael Y.; Katsaras, John; Sumpter, Bobby G.; ...

2017-01-12

Biological cell membranes are responsible for a range of structural and dynamical phenomena crucial to a cell's well-being and its associated functions. Due to the complexity of cell membranes, lipid bilayer systems are often used as biomimetic models. These systems have led to signficant insights into vital membrane phenomena such as domain formation, passive permeation and protein insertion. Experimental observations of membrane structure and dynamics are, however, limited in resolution, both spatially and temporally. Importantly, computer simulations are starting to play a more prominent role in interpreting experimental results, enabling a molecular under- standing of lipid membranes. Particularly, the synergymore » between scattering experiments and simulations offers opportunities for new discoveries in membrane physics, as the length and time scales probed by molecular dynamics (MD) simulations parallel those of experiments. We also describe a coarse-grained MD simulation approach that mimics neutron scattering data from large unilamellar lipid vesicles over a range of bilayer rigidity. Specfically, we simulate vesicle form factors and membrane thickness fluctuations determined from small angle neutron scattering (SANS) and neutron spin echo (NSE) experiments, respectively. Our simulations accurately reproduce trends from experiments and lay the groundwork for investigations of more complex membrane systems.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rai, Durgesh K.; Sharma, Veerendra K.; Anunciado, Divina

The interaction between lipid bilayers and Amyloid β peptide (Aβ) plays a critical role in proliferation of Alzheimer’s disease (AD). AD is expected to affect one in every 85 humans by 2050, and therefore, deciphering the interplay of Aβ and lipid bilayers at the molecular level is of profound importance. In this work, we applied an array of neutron scattering methods to study the structure and dynamics of Aβ(1–40) interacting 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG) bilayers. In the structural investigations of lipid bilayer’s response to Aβ binding, Small Angle Neutron Scattering and Neutron Membrane Diffraction revealed that the Aβ anchors firmly to themore » highly charged DMPG bilayers in the interfacial region between water and hydrocarbon chain, and it doesn’t penetrate deeply into the bilayer. This association mode is substantiated by the dynamics studies with high resolution Quasi-Elastic Neutron Scattering experiments, showing that the addition of Aβ mainly affects the slower lateral motion of lipid molecules, especially in the fluid phase, but not the faster internal motion. The results revealed that Aβ associates with the highly charged membrane in surface with limited impact on the structure, but the altered membrane dynamics could have more influence on other membrane processes.« less

Effective interactions in lysozyme aqueous solutions: a small-angle neutron scattering and computer simulation study.

PubMed

Abramo, M C; Caccamo, C; Costa, D; Pellicane, G; Ruberto, R; Wanderlingh, U

2012-01-21

We report protein-protein structure factors of aqueous lysozyme solutions at different pH and ionic strengths, as determined by small-angle neutron scattering experiments. The observed upturn of the structure factor at small wavevectors, as the pH increases, marks a crossover between two different regimes, one dominated by repulsive forces, and another one where attractive interactions become prominent, with the ensuing development of enhanced density fluctuations. In order to rationalize such experimental outcome from a microscopic viewpoint, we have carried out extensive simulations of different coarse-grained models. We have first studied a model in which macromolecules are described as soft spheres interacting through an attractive r(-6) potential, plus embedded pH-dependent discrete charges; we show that the uprise undergone by the structure factor is qualitatively predicted. We have then studied a Derjaguin-Landau-Verwey-Overbeek (DLVO) model, in which only central interactions are advocated; we demonstrate that this model leads to a protein-rich/protein-poor coexistence curve that agrees quite well with the experimental counterpart; experimental correlations are instead reproduced only at low pH and ionic strengths. We have finally investigated a third, "mixed" model in which the central attractive term of the DLVO potential is imported within the distributed-charge approach; it turns out that the different balance of interactions, with a much shorter-range attractive contribution, leads in this latter case to an improved agreement with the experimental crossover. We discuss the relationship between experimental correlations, phase coexistence, and features of effective interactions, as well as possible paths toward a quantitative prediction of structural properties of real lysozyme solutions. © 2012 American Institute of Physics

A rocket-borne energy spectrometer using multiple solid-state detectors for particle identification

NASA Technical Reports Server (NTRS)

Fries, K. L.; Smith, L. G.; Voss, H. D.

1979-01-01

A rocket-borne experiment using energy spectrometers that allows particle identification by the use of multiple solid-state detectors is described. The instrumentation provides information regarding the energy spectrum, pitch-angle distribution, and the type of energetic particles present in the ionosphere. Particle identification was accomplished by considering detector loss mechanisms and their effects on various types of particles. Solid state detectors with gold and aluminum surfaces of several thicknesses were used. The ratios of measured energies for the various detectors were compared against known relationships during ground-based analysis. Pitch-angle information was obtained by using detectors with small geometrical factors mounted with several look angles. Particle flux was recorded as a function of rocket azimuth angle. By considering the rocket azimuth, the rocket precession, and the location of the detectors on the rocket, the pitched angle of the incident particles was derived.

A large 2D PSD for thermal neutron detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knott, R.B.; Watt, G.; Boldeman, J.W.

1996-12-31

A 2D PSD based on a MWPC has been constructed for a small angle neutron scattering instrument. The active area of the detector was 640 x 640 mm{sup 2}. To meet the specifications for neutron detection efficiency and spatial resolution, and to minimize parallax, the gas mixture was 190 kPa {sup 3}He plus 100 kPa CF{sub 4} and the active volume had a thickness of 30 mm. The design maximum neutron count-rate of the detector was 10{sup 5} events per second. The (calculated) neutron detection efficiency was 60% for 2{angstrom} neutrons and the (measured) neutron energy resolution on the anodemore » grid was typically 20% (fwhm). The location of a neutron detection event within the active area was determined using the wire-by-wire method: the spatial resolution (5 x 5 mm{sup 2}) was thereby defined by the wire geometry. A 16 channel charge-sensitive preamplifier/amplifier/comparator module has been developed with a channel sensitivity of 0.1 V/fC, noise linewidth of 0.4 fC (fwhm) and channel-to-channel cross-talk of less than 5%. The Proportional Counter Operating System (PCOS III) (LeCroy Corp USA) was used for event encoding. The ECL signals produced by the 16 channel modules were latched in PCOS III by a trigger pulse from the anode and the fast encoders produce a position and width for each event. The information was transferred to a UNIX workstation for accumulation and online display.« less

LORES: Low resolution shape program for the calculation of small angle scattering profiles for biological macromolecules in solution

NASA Astrophysics Data System (ADS)

Zhou, J.; Deyhim, A.; Krueger, S.; Gregurick, S. K.

2005-08-01

A program for determining the low resolution shape of biological macromolecules, based on the optimization of a small angle neutron scattering profile to experimental data, is presented. This program, termed LORES, relies on a Monte Carlo optimization procedure and will allow for multiple scattering length densities of complex structures. It is therefore more versatile than utilizing a form factor approach to produce low resolution structural models. LORES is easy to compile and use, and allows for structural modeling of biological samples in real time. To illustrate the effectiveness and versatility of the program, we present four specific biological examples, Apoferritin (shell model), Ribonuclease S (ellipsoidal model), a 10-mer dsDNA (duplex helix) and a construct of a 10-mer DNA/PNA duplex helix (heterogeneous structure). These examples are taken from protein and nucleic acid SANS studies, of both large and small scale structures. We find, in general, that our program will accurately reproduce the geometric shape of a given macromolecule, when compared with the known crystallographic structures. We also present results to illustrate the lower limit of the experimental resolution which the LORES program is capable of modeling. Program summaryTitle of program:LORES Catalogue identifier: ADVC Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADVC Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Computer:SGI Origin200, SGI Octane, SGI Linux, Intel Pentium PC Operating systems:UNIX64 6.5 and LINUX 2.4.7 Programming language used:C Memory required to execute with typical data:8 MB No. of lines in distributed program, including test data, etc.:2270 No. of bytes in distributed program, including test data, etc.:13 302 Distribution format:tar.gz External subprograms used:The entire code must be linked with the MATH library

Smaller, Lower-Power Fast-Neutron Scintillation Detectors

NASA Technical Reports Server (NTRS)

Patel, Jagdish; Blaes, Brent

2008-01-01

Scintillation-based fast-neutron detectors that are smaller and less power-hungry than mainstream scintillation-based fast-neutron detectors are undergoing development. There are numerous applications for such detectors in monitoring fast-neutron fluxes from nuclear reactors, nuclear materials, and natural sources, both on Earth and in outer space. A particularly important terrestrial application for small, low-power, portable fast-neutron detectors lies in the requirement to scan for nuclear materials in cargo and baggage arriving at international transportation facilities. The present development of miniature, low-power scintillation-based fast-neutron detectors exploits recent advances in the fabrication of avalanche photodiodes (APDs). Basically, such a detector includes a plastic scintillator, typically between 300 and 400 m thick with very thin silver mirror coating on all its faces except the one bonded to an APD. All photons generated from scintillation are thus internally reflected and eventually directed to the APD. This design affords not only compactness but also tight optical coupling for utilization of a relatively large proportion of the scintillation light. The combination of this tight coupling and the avalanche-multiplication gain (typically between 750 and 1,000) of the APD is expected to have enough sensitivity to enable monitoring of a fast-neutron flux as small as 1,000 cm(exp -2)s(exp -1). Moreover, pulse-height analysis can be expected to provide information on the kinetic energies of incident neutrons. It has been estimated that a complete, fully developed fast-neutron detector of this type, would be characterized by linear dimensions of the order of 10 cm or less, a mass of no more than about 0.5 kg, and a power demand of no more than a few watts.

X-ray studies of dynamic aging in an aluminum alloy subjected to severe plastic deformation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sitdikov, V.D., E-mail: svil@mail.rb.ru; Laboratory for Mechanics of Bulk Nanomaterials, Saint Petersburg State University, 28 Universitetsky pr., Saint Petersburg 198504; Chizhov, P.S.

In this work, X-ray scattering methods were applied for a quantitative characterization of the microstructure of an aluminum alloy of the Al–Mg–Si system during dynamic aging realized through the high pressure torsion technique. A qualitative and quantitative phase analysis of the alloy was performed, together with Al alloy lattice parameter determination. From the reflections broadening the effective size of the coherent scattering domains and the lattice microstrain were determined in the framework of the Halder–Wagner approach. Using the method of small-angle X-ray scattering, the quantitative characteristics of the size, shape and spatial distribution of the secondary phase particles formed inmore » the Al alloy during dynamic aging were established. In order to validate the obtained results, the method of small-angle X-ray scattering was preliminarily tested on similar samples after artificial aging and compared with the results from small-angle neutron diffraction widely known in literature. - Highlights: • Spherical fcc β-Mg2Si precipitates formed in Al 6201 alloy during dynamic aging in the course of severe plastic deformation. • The size, shape and distribution of the precipitates due to artificial and dynamic aging were revealed by SAXS method. • Monoclinic needle-like β' precipitates and Al5FeSi intermetallic phase were detected in 6201 alloy after T6 treatment.« less

Angular distribution measurements of photo-neutron yields produced by 2.0 GeV electrons incident on thick targets.

PubMed

Lee, Hee-Seock; Ban, Syuichi; Sanami, Toshiya; Takahashi, Kazutoshi; Sato, Tatsuhiko; Shin, Kazuo; Chung, Chinwha

2005-01-01

A study of differential photo-neutron yields by irradiation with 2 GeV electrons has been carried out. In this extension of a previous study in which measurements were made at an angle of 90 degrees relative to incident electrons, the differential photo-neutron yield was obtained at two other angles, 48 degrees and 140 degrees, to study its angular characteristics. Photo-neutron spectra were measured using a pulsed beam time-of-flight method and a BC418 plastic scintillator. The reliable range of neutron energy measurement was 8-250 MeV. The neutron spectra were measured for 10 Xo-thick Cu, Sn, W and Pb targets. The angular distribution characteristics, together with the previous results for 90 degrees, are presented in the study. The experimental results are compared with Monte Carlo calculation results. The yields predicted by MCNPX 2.5 tend to underestimate the measured ones. The same trend holds for the comparison results using the EGS4 and PICA3 codes.

Response functions for neutron skyshine analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gui, A.A.; Shultis, J.K.; Faw, R.E.

1997-02-01

Neutron and associated secondary photon line-beam response functions (LBRFs) for point monodirectional neutron sources are generated using the MCNP Monte Carlo code for use in neutron skyshine analysis employing the integral line-beam method. The LBRFs are evaluated at 14 neutron source energies ranging from 0.01 to 14 MeV and at 18 emission angles from 1 to 170 deg, as measured from the source-to-detector axis. The neutron and associated secondary photon conical-beam response functions (CBRFs) for azimuthally symmetric neutron sources are also evaluated at 13 neutron source energies in the same energy range and at 13 polar angles of source collimationmore » from 1 to 89 deg. The response functions are approximated by an empirical three-parameter function of the source-to-detector distance. These response function approximations are available for a source-to-detector distance up to 2,500 m and, for the first time, give dose equivalent responses that are required for modern radiological assessments. For the CBRFs, ground correction factors for neutrons and secondary photons are calculated and also approximated by empirical formulas for use in air-over-ground neutron skyshine problems with azimuthal symmetry. In addition, simple procedures are proposed for humidity and atmospheric density corrections.« less

Measurements and parameterization of neutron energy spectra from targets bombarded with 120 GeV protons

NASA Astrophysics Data System (ADS)

Kajimoto, T.; Shigyo, N.; Sanami, T.; Iwamoto, Y.; Hagiwara, M.; Lee, H. S.; Soha, A.; Ramberg, E.; Coleman, R.; Jensen, D.; Leveling, A.; Mokhov, N. V.; Boehnlein, D.; Vaziri, K.; Sakamoto, Y.; Ishibashi, K.; Nakashima, H.

2014-10-01

The energy spectra of neutrons were measured by a time-of-flight method for 120 GeV protons on thick graphite, aluminum, copper, and tungsten targets with an NE213 scintillator at the Fermilab Test Beam Facility. Neutron energy spectra were obtained between 25 and 3000 MeV at emission angles of 30°, 45°, 120°, and 150°. The spectra were parameterized as neutron emissions from three moving sources and then compared with theoretical spectra calculated by PHITS and FLUKA codes. The yields of the theoretical spectra were substantially underestimated compared with the yields of measured spectra. The integrated neutron yields from 25 to 3000 MeV calculated with PHITS code were 16-36% of the experimental yields and those calculated with FLUKA code were 26-57% of the experimental yields for all targets and emission angles.

Illuminating gravitational waves: A concordant picture of photons from a neutron star merger

DOE PAGES

Kasliwal, M. M.; Nakar, E.; Singer, L. P.; ...

2017-10-16

Merging neutron stars offer an excellent laboratory for simultaneously studying strong-field gravity and matter in extreme environments. We establish the physical association of an electromagnetic counterpart (EM170817) with gravitational waves (GW170817) detected from merging neutron stars. By synthesizing a panchromatic data set, we demonstrate that merging neutron stars are a long-sought production site forging heavy elements by r-process nucleosynthesis. The weak gamma rays seen in EM170817 are dissimilar to classical short gamma-ray bursts with ultrarelativistic jets. Instead, we suggest that breakout of a wide-angle, mildly relativistic cocoon engulfing the jet explains the low-luminosity gamma rays, the high-luminosity ultraviolet-optical-infrared, and themore » delayed radio and x-ray emission. We posit that all neutron star mergers may lead to a wide-angle cocoon breakout, sometimes accompanied by a successful jet and sometimes by a choked jet.« less

Illuminating gravitational waves: A concordant picture of photons from a neutron star merger

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kasliwal, M. M.; Nakar, E.; Singer, L. P.

Merging neutron stars offer an excellent laboratory for simultaneously studying strong-field gravity and matter in extreme environments. We establish the physical association of an electromagnetic counterpart (EM170817) with gravitational waves (GW170817) detected from merging neutron stars. By synthesizing a panchromatic data set, we demonstrate that merging neutron stars are a long-sought production site forging heavy elements by r-process nucleosynthesis. The weak gamma rays seen in EM170817 are dissimilar to classical short gamma-ray bursts with ultrarelativistic jets. Instead, we suggest that breakout of a wide-angle, mildly relativistic cocoon engulfing the jet explains the low-luminosity gamma rays, the high-luminosity ultraviolet-optical-infrared, and themore » delayed radio and x-ray emission. We posit that all neutron star mergers may lead to a wide-angle cocoon breakout, sometimes accompanied by a successful jet and sometimes by a choked jet.« less

Illuminating gravitational waves: A concordant picture of photons from a neutron star merger

NASA Astrophysics Data System (ADS)

Kasliwal, M. M.; Nakar, E.; Singer, L. P.; Kaplan, D. L.; Cook, D. O.; Van Sistine, A.; Lau, R. M.; Fremling, C.; Gottlieb, O.; Jencson, J. E.; Adams, S. M.; Feindt, U.; Hotokezaka, K.; Ghosh, S.; Perley, D. A.; Yu, P.-C.; Piran, T.; Allison, J. R.; Anupama, G. C.; Balasubramanian, A.; Bannister, K. W.; Bally, J.; Barnes, J.; Barway, S.; Bellm, E.; Bhalerao, V.; Bhattacharya, D.; Blagorodnova, N.; Bloom, J. S.; Brady, P. R.; Cannella, C.; Chatterjee, D.; Cenko, S. B.; Cobb, B. E.; Copperwheat, C.; Corsi, A.; De, K.; Dobie, D.; Emery, S. W. K.; Evans, P. A.; Fox, O. D.; Frail, D. A.; Frohmaier, C.; Goobar, A.; Hallinan, G.; Harrison, F.; Helou, G.; Hinderer, T.; Ho, A. Y. Q.; Horesh, A.; Ip, W.-H.; Itoh, R.; Kasen, D.; Kim, H.; Kuin, N. P. M.; Kupfer, T.; Lynch, C.; Madsen, K.; Mazzali, P. A.; Miller, A. A.; Mooley, K.; Murphy, T.; Ngeow, C.-C.; Nichols, D.; Nissanke, S.; Nugent, P.; Ofek, E. O.; Qi, H.; Quimby, R. M.; Rosswog, S.; Rusu, F.; Sadler, E. M.; Schmidt, P.; Sollerman, J.; Steele, I.; Williamson, A. R.; Xu, Y.; Yan, L.; Yatsu, Y.; Zhang, C.; Zhao, W.

2017-12-01

Merging neutron stars offer an excellent laboratory for simultaneously studying strong-field gravity and matter in extreme environments. We establish the physical association of an electromagnetic counterpart (EM170817) with gravitational waves (GW170817) detected from merging neutron stars. By synthesizing a panchromatic data set, we demonstrate that merging neutron stars are a long-sought production site forging heavy elements by r-process nucleosynthesis. The weak gamma rays seen in EM170817 are dissimilar to classical short gamma-ray bursts with ultrarelativistic jets. Instead, we suggest that breakout of a wide-angle, mildly relativistic cocoon engulfing the jet explains the low-luminosity gamma rays, the high-luminosity ultraviolet-optical-infrared, and the delayed radio and x-ray emission. We posit that all neutron star mergers may lead to a wide-angle cocoon breakout, sometimes accompanied by a successful jet and sometimes by a choked jet.

Comparing results of X-ray diffraction, µ-Raman spectroscopy and neutron diffraction when identifying chemical phases in seized nuclear material, during a comparative nuclear forensics exercise

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rondahl, Stina Holmgren; Pointurier, Fabien; Ahlinder, Linnea

This work presents the results for identification of chemical phases obtained by several laboratories as a part of an international nuclear forensic round-robin exercise. In this work powder X-ray diffraction (p-XRD) is regarded as the reference technique. Neutron diffraction produced a superior high-angle diffraction pattern relative to p-XRD. Requiring only small amounts of sample, µ-Raman spectroscopy was used for the first time in this context as a potentially complementary technique to p-XRD. The chemical phases were identified as pure UO 2 in two materials, and as a mixture of UO 2, U 3O 8 and an intermediate species U 3Omore » 7 in the third material.« less

Comparing results of X-ray diffraction, µ-Raman spectroscopy and neutron diffraction when identifying chemical phases in seized nuclear material, during a comparative nuclear forensics exercise

DOE PAGES

Rondahl, Stina Holmgren; Pointurier, Fabien; Ahlinder, Linnea; ...

2018-01-24

This work presents the results for identification of chemical phases obtained by several laboratories as a part of an international nuclear forensic round-robin exercise. In this work powder X-ray diffraction (p-XRD) is regarded as the reference technique. Neutron diffraction produced a superior high-angle diffraction pattern relative to p-XRD. Requiring only small amounts of sample, µ-Raman spectroscopy was used for the first time in this context as a potentially complementary technique to p-XRD. The chemical phases were identified as pure UO 2 in two materials, and as a mixture of UO 2, U 3O 8 and an intermediate species U 3Omore » 7 in the third material.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bernstein, A. M., E-mail: bernstein@mit.edu

Small angle electron scattering with intense electron beams opens up the possibility of performing almost real photon induced reactions with thin, polarized hydrogen and few body targets, allowing for the detection of low energy charged particles. This promises to be much more effective than conventional photon tagging techniques. For photo-pion reactions some fundamental new possibilities include: tests of charge symmetry in the N-N system by measurement of the neutron-neutron scattering length a{sub nn} in the and ggrD → π{sup +}nn reaction; tests of isospin breaking due to the mass difference of the up and down quarks; measurements with polarized targetsmore » are sensitive to πN phase shifts and will test the validity of the Fermi-Watson (final state interaction) theorem. All of these experiments will test the accuracy and energy region of validity of chiral effective theories.« less

Neutron Electric Dipole Moment from Gauge-String Duality.

PubMed

Bartolini, Lorenzo; Bigazzi, Francesco; Bolognesi, Stefano; Cotrone, Aldo L; Manenti, Andrea

2017-03-03

We compute the electric dipole moment of nucleons in the large N_{c} QCD model by Witten, Sakai, and Sugimoto with N_{f}=2 degenerate massive flavors. Baryons in the model are instantonic solitons of an effective five-dimensional action describing the whole tower of mesonic fields. We find that the dipole electromagnetic form factor of the nucleons, induced by a finite topological θ angle, exhibits complete vector meson dominance. We are able to evaluate the contribution of each vector meson to the final result-a small number of modes are relevant to obtain an accurate estimate. Extrapolating the model parameters to real QCD data, the neutron electric dipole moment is evaluated to be d_{n}=1.8×10^{-16}θ e cm. The electric dipole moment of the proton is exactly the opposite.

New narrow-beam neutron spectrometer in complex monitoring system

NASA Astrophysics Data System (ADS)

Mikhalko, Evgeniya; Balabin, Yuriy; Maurchev, Evgeniy; Germanenko, Aleksey

2018-03-01

In the interaction of cosmic rays (CRs) with Earth's atmosphere, neutrons are formed in a wide range of energies: from thermal (E≈0.025 eV) to ultrarelativistic (E>1 GeV). To detect and study CRs, Polar Geophysical Institute (PGI) uses a complex monitoring system containing detectors of various configurations. The standard neutron monitor (NM) 18-NM-64 is sensitive to neutrons with energies E>50 MeV. The lead-free section of the neutron monitor (BSRM) detects neutrons with energies E≈(0.1/1) MeV. Also, for sharing with standard detectors, the Apatity NM station has developed and installed a neutron spectrometer with three energy channels and a particle reception angle of 15 degrees. The configuration of the device makes it possible to study the degree of anisotropy of the particle flux from different directions. We have obtained characteristics of the detector (response function and particle reception angle), as well as geometric dimensions through numerical simulation using the GEANT4 toolkit [Agostinelli et al., 2003]. During operation of the device, we collected database of observations and received preliminary results.

Exclusive measurements of light fragment production at forward angles in NePb and NeNaF collisions at {E}/{A} = 400 MeV and 800 MeV

NASA Astrophysics Data System (ADS)

Bastid, N.; Alard, J. P.; Arnold, J.; Augerat, J.; Babinet, R.; Biagi, F.; Brochard, F.; Crouau, M.; Charmensat, P.; Dupieux, P.; Fodor, Z.; Fraysse, L.; Girard, J.; Gorodetzky, P.; Gosset, J.; Laspalles, C.; Lemaire, M. C.; Le Merdy, A.; L'hôte, D.; Lucas, B.; Marroncle, J.; Montarou, G.; Parizet, M. J.; Poitou, J.; Qassoud, D.; Racca, C.; Rahmani, A.; Schimmerling, W.; Terrien, Y.; Valette, O.

1990-01-01

Emission of light fragments at small angles is studied in relativistic heavy ion collisions using the Diogene plastic wall for both symmetrical and non-symmetrical target-projectile systems with 400 MeV per nucleon and 800 MeV per nucleon incident neon nuclei. Efficiency of multiplicity measurements in the small angle range for the selection of central or peripheral collisions is confirmed for asymmetric systems. Differential production cross sections of Z = 1 fragments show evidence for the existence of two emitting sources. The apparent temperature of each source is obtained from comparison with a thermodynamical model.

Exclusive measurements of light fragment production at forward angles in Ne-Pb and Ne-NaF collisions at E/A=400 MeV and 800 MeV

NASA Technical Reports Server (NTRS)

Bastid, N.; Alard, J. P.; Arnold, J.; Augerat, J.; Babinet, R.; Biagi, F.; Brochard, F.; Crouau, M.; Charmensat, P.; Dupieux, P.;

Impact of the neutron detector choice on Bell and Glasstone spatial correction factor for subcriticality measurement

NASA Astrophysics Data System (ADS)

Talamo, Alberto; Gohar, Y.; Cao, Y.; Zhong, Z.; Kiyavitskaya, H.; Bournos, V.; Fokov, Y.; Routkovskaya, C.

2012-03-01

In subcritical assemblies, the Bell and Glasstone spatial correction factor is used to correct the measured reactivity from different detector positions. In addition to the measuring position, several other parameters affect the correction factor: the detector material, the detector size, and the energy-angle distribution of source neutrons. The effective multiplication factor calculated by computer codes in criticality mode slightly differs from the average value obtained from the measurements in the different experimental channels of the subcritical assembly, which are corrected by the Bell and Glasstone spatial correction factor. Generally, this difference is due to (1) neutron counting errors; (2) geometrical imperfections, which are not simulated in the calculational model, and (3) quantities and distributions of material impurities, which are missing from the material definitions. This work examines these issues and it focuses on the detector choice and the calculation methodologies. The work investigated the YALINA Booster subcritical assembly of Belarus, which has been operated with three different fuel enrichments in the fast zone either: high (90%) and medium (36%), medium (36%), or low (21%) enriched uranium fuel.

Neutron Detector Signal Processing to Calculate the Effective Neutron Multiplication Factor of Subcritical Assemblies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Talamo, Alberto; Gohar, Yousry

2016-06-01

This report describes different methodologies to calculate the effective neutron multiplication factor of subcritical assemblies by processing the neutron detector signals using MATLAB scripts. The subcritical assembly can be driven either by a spontaneous fission neutron source (e.g. californium) or by a neutron source generated from the interactions of accelerated particles with target materials. In the latter case, when the particle accelerator operates in a pulsed mode, the signals are typically stored into two files. One file contains the time when neutron reactions occur and the other contains the times when the neutron pulses start. In both files, the timemore » is given by an integer representing the number of time bins since the start of the counting. These signal files are used to construct the neutron count distribution from a single neutron pulse. The built-in functions of MATLAB are used to calculate the effective neutron multiplication factor through the application of the prompt decay fitting or the area method to the neutron count distribution. If the subcritical assembly is driven by a spontaneous fission neutron source, then the effective multiplication factor can be evaluated either using the prompt neutron decay constant obtained from Rossi or Feynman distributions or the Modified Source Multiplication (MSM) method.« less

A study of X-ray multiple diffraction by means of section topography.

PubMed

Kohn, V G; Smirnova, I A

2015-09-01

The results of theoretical and experimental study are presented for the question of how the X-ray multiple diffraction in a silicon single crystal influences the interference fringes of section topography for the 400 reflection in the Laue case. Two different cases of multiple diffraction are discovered for zero and very small values of the azimuthal angle for the sample in the form of a plate with the surface normal to the 001 direction. The cases are seen on the same topogram without rotation of the crystal. Accurate computer simulations of the section topogram for the case of X-ray multiple diffraction are performed for the first time. It is shown that the structure of interference fringes on the section topogram in the region of multiple diffraction becomes more complicated. It has a very sharp dependence on the azimuthal angle. The experiment is carried out using a laboratory source under conditions of low resolution over the azimuthal angle. Nevertheless, the characteristic inclination of the interference fringes on the tails of the multiple diffraction region is easily seen. This phenomenon corresponds completely to the computer simulations.

Band selective small flip angle COSY: a simple experiment for the analyses of 1H NMR spectra of small chiral molecules.

PubMed

Prabhu, Uday Ramesh; Suryaprakash, N

2008-12-01

The NMR spectroscopic discrimination of enantiomers in the chiral liquid crystalline solvent is more often carried out using (2)H detection in its natural abundance. The employment of (1)H detection for such a purpose is severely hampered due to significant loss of resolution in addition to indistinguishable overlap of the spectra from the two enantiomers. This study demonstrates that the band selected small flip angle homonuclear correlation experiment is a simple and robust technique that provides unambiguous discrimination, very high spectral resolution, reduced multiplicity of transitions, relative signs of the couplings and enormous saving of instrument time.

Using Neutron Scattering and Mercury Intrusion Techniques to Characterize Micro- and Nano-Pore Structure of Shale

NASA Astrophysics Data System (ADS)

Zhang, Y.; Barber, T.; Hu, Q.; Bleuel, M.

2017-12-01

The micro- and nano-pore structure of oil shale plays a critical role in hydrocarbon storage and migration. This study aims to characterize the pore structure of three Bakken members (i.e., upper organic-rich shale, middle silty/sandy dolomites, and lower organic-rich shale), through small and ultra-small angle neutron scattering (SANS and USANS) techniques, as well as mercury injection capillary pressure (MICP) analyses. SANS/USANS have the capabilities of measuring total porosity (connected and closed porosity) across nm-mm spectrum, not measurable than other fluid-invasion approaches, such as MICP which obtains connected porosity and pore-throat size distribution. Results from both techniques exhibit different features of upper/lower Bakken and middle Bakken, as a result of various mineral composition and organic matter contents. Middle Bakken is primarily dominated by the mineral pores, while in the upper and lower Bakken, organic pores contribute a significant portion of total porosity. A combination of USANS/SANS and MICP techniques gives a comprehensive picture of shale micro- and nano-pore structure.

Effect of Carbon Black on Elastomer Blends

NASA Astrophysics Data System (ADS)

Si, Mayu; Koga, Tadanori; Ji, Yuan; Seo, Young-Soo; Rafailovich, Miriam; Sokolov, Jonathan; Gerspacher, M.; Dias, A. J.; Karp, Kriss R.; Satija, Sushil; Lin, Min Y.

2003-03-01

The effects of untreated and heat-treated carbon black N299 on the interfacial properties of PB (Polybutadiene) and terpolymer BIMS [brominated Poly(isobutylene-co-methyl styrene)] were investigated by neutron reflectivity (NR) and lateral force microscopy (LFM). The NR results show that the addition of carbon black significantly slows down the interfacial broadening while heat-treated carbon black has less effect on slowing down the diffusion compared with untreated carbon black. These results were confirmed by the LFM data, which shows the magnitude of lateral force loop of heat-treated carbon black is bigger than that of untreated one. Ultra small and small angle neutron scattering (USANS and SANS) were used to probe the morphology and surface lateral force. Increasing volume concentration of carbon black to 5glass transition temperature of BIMS is also decreased, which was measured by Differential scanning Calorimeter (DSC). XRD analysis indicates that the heat treatment crystallizes the carbon black and strong graphitic peaks are observed. The large degree of crystallization decreases the interaction with the polymer matrix and hence minimizes the effect on the internal dynamics

Multi-Objective Optimization of Spacecraft Trajectories for Small-Body Coverage Missions

NASA Technical Reports Server (NTRS)

Hinckley, David, Jr.; Englander, Jacob; Hitt, Darren

2017-01-01

Visual coverage of surface elements of a small-body object requires multiple images to be taken that meet many requirements on their viewing angles, illumination angles, times of day, and combinations thereof. Designing trajectories capable of maximizing total possible coverage may not be useful since the image target sequence and the feasibility of said sequence given the rotation-rate limitations of the spacecraft are not taken into account. This work presents a means of optimizing, in a multi-objective manner, surface target sequences that account for such limitations.

Characterization of polymer adsorption onto drug nanoparticles using depletion measurements and small-angle neutron scattering.

PubMed

Goodwin, Daniel J; Sepassi, Shadi; King, Stephen M; Holland, Simon J; Martini, Luigi G; Lawrence, M Jayne

2013-11-04

Production of polymer and/or surfactant-coated crystalline nanoparticles of water-insoluble drugs (nanosuspensions) using wet bead milling is an important formulation approach to improve the bioavailability of said compounds. Despite the fact that there are a number of nanosuspensions on the market, there is still a deficiency in the characterization of these nanoparticles where further understanding may lead to the rational selection of polymer/surfactant. To this end small-angle neutron scattering (SANS) measurements were performed on drug nanoparticles milled in the presence of a range of polymers of varying molecular weight. Isotopic substitution of the aqueous solvent to match the scattering length density of the drug nanoparticles (i.e., the technique of contrast matching) meant that neutron scattering resulted only from the adsorbed polymer layer. The layer thickness and amount of hydroxypropylcellulose adsorbed on nabumetone nanoparticles derived from fitting the SANS data to both model-independent and model dependent volume fraction profiles were insensitive to polymer molecular weight over the range Mv = 47-112 kg/mol, indicating that the adsorbed layer is relatively flat but with tails extending up to approximately 23 nm. The constancy of the absorbed amount is in agreement with the adsorption isotherm determined by measuring polymer depletion from solution in the presence of the nanoparticles. Insensitivity to polymer molecular weight was similarly determined using SANS measurements of nabumetone or halofantrine nanoparticles stabilized with hydroxypropylmethylcellulose or poly(vinylpyrrolidone). Additionally SANS studies revealed the amount adsorbed, and the thickness of the polymer layer was dependent on both the nature of the polymer and drug particle surface. The insensitivity of the adsorbed polymer layer to polymer molecular weight has important implications for the production of nanoparticles, suggesting that lower molecular weight polymers should be used when preparing nanoparticles by wet bead milling since nanoparticle formation is more rapid but with no likely consequence on the resultant physical stability of the nanoparticles.

Multiplicity Counting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Geist, William H.

2015-12-01

This set of slides begins by giving background and a review of neutron counting; three attributes of a verification item are discussed: 240Pu eff mass; α, the ratio of (α,n) neutrons to spontaneous fission neutrons; and leakage multiplication. It then takes up neutron detector systems – theory & concepts (coincidence counting, moderation, die-away time); detector systems – some important details (deadtime, corrections); introduction to multiplicity counting; multiplicity electronics and example distributions; singles, doubles, and triples from measured multiplicity distributions; and the point model: multiplicity mathematics.

Spatial anisotropy of neutrons emitted from the 56Fe(γ ,n )55Fe reaction with a linearly polarized γ -ray beam

NASA Astrophysics Data System (ADS)

Hayakawa, T.; Shizuma, T.; Miyamoto, S.; Amano, S.; Takemoto, A.; Yamaguchi, M.; Horikawa, K.; Akimune, H.; Chiba, S.; Ogata, K.; Fujiwara, M.

2016-04-01

We have measured the azimuthal anisotropy of neutrons emitted from the 56Fe(γ ,n )55Fe reaction with a linearly polarized γ -ray beam generated by laser Compton scattering at NewSUBARU. Neutron yields at the polar angle of 90∘ have been measured as a function of the azimuthal angle ϕ between the detector and the linear polarization plane of the γ -ray beam. The azimuthal anisotropy of neutrons measured at ϕ =0∘ , 10∘, 25∘, 45∘, 60∘, 70∘, and 90∘ has been well reproduced using a theoretically predicted function of a +b cos(2 ϕ ) .

Densification of Supercritical Carbon Dioxide Accompanied by Droplet Formation When Passing the Widom Line

NASA Astrophysics Data System (ADS)

Pipich, Vitaliy; Schwahn, Dietmar

2018-04-01

Thermal density fluctuations of supercritical CO2 were explored using small-angle neutron scattering (SANS), whose amplitude (susceptibility) and correlation length show the expected maximum at the Widom line. At low pressure, the susceptibility is in excellent agreement with the evaluated values on the basis of mass density measurements. At about 20 bar beyond the Widom line, SANS shows the formation of droplets accompanied by an enhanced number density of the supercritical fluid. The corresponding borderline is interpreted as a Frenkel line separating gas- and liquidlike regimes.

Densification of Supercritical Carbon Dioxide Accompanied by Droplet Formation When Passing the Widom Line.

PubMed

Pipich, Vitaliy; Schwahn, Dietmar

2018-04-06

Thermal density fluctuations of supercritical CO_{2} were explored using small-angle neutron scattering (SANS), whose amplitude (susceptibility) and correlation length show the expected maximum at the Widom line. At low pressure, the susceptibility is in excellent agreement with the evaluated values on the basis of mass density measurements. At about 20 bar beyond the Widom line, SANS shows the formation of droplets accompanied by an enhanced number density of the supercritical fluid. The corresponding borderline is interpreted as a Frenkel line separating gas- and liquidlike regimes.

Internal magnetic structure of magnetite nanoparticles at low temperature

NASA Astrophysics Data System (ADS)

Krycka, K. L.; Borchers, J. A.; Booth, R. A.; Hogg, C. R.; Ijiri, Y.; Chen, W. C.; Watson, S. M.; Laver, M.; Gentile, T. R.; Harris, S.; Dedon, L. R.; Rhyne, J. J.; Majetich, S. A.

2010-05-01

Small-angle neutron scattering with polarization analysis reveals that Fe3O4 nanoparticles with 90 Å diameters have ferrimagnetic moments significantly reduced from that of bulk Fe3O4 at 10 K, nominal saturation. Combined with previous results for an equivalent applied field at 200 K, a core-disordered shell picture of a spatially reduced ferrimagnetic core emerges, even well below the bulk blocking temperature. Zero-field cooling suggests that this magnetic morphology may be intrinsic to the nanoparticle, rather than field induced, at 10 K.

Transmission-geometry electrochemical cell for in-situ scattering and spectroscopy investigations

DOEpatents

Chupas, Peter J.; Chapman, Karena W.; Kurtz, Charles A.; Borkiewicz, Olaf J.; Wiaderek, Kamila Magdelena; Shyam, Badri

2015-05-05

The present invention relates to a test chamber that can be used to perform a variety of X-ray and neutron spectroscopy experiments including powder diffraction, small-angle scattering, X-ray absorption spectroscopy, and pair distribution functions, such chamber comprising a first electrode with an X-ray transparent window; a second electrode with an X-ray transparent window; a plurality of insulating gaskets providing a hermetic seal around the sample and preventing contact between said first and second electrodes; and an insulating housing into which the first electrode is secured.

Small-angle Neutron Scattering Study of Magnetic Ordering and Inhomogeneity Across the Martensitic Phase Transformation in Ni50-xCoxMn40Sn10 Alloys

DTIC Science & Technology

2012-04-27

Oe to 70 kOe. For low-field measurements the remnant field profile in the superconducting magnet was measured and the field at the sample nulled to 1... magnetization similar to the bulk magnetization in the austenite. In particular, the saturation magnetization of such a nanoscopic F cluster would be...expected to be significantly smaller than the bulk magnetization of 5 μB/f.u., due to both finite-size effects and competition between F and AF exchange

Effect of borax concentration on the structure of Poly(Vinyl Alcohol) gels

NASA Astrophysics Data System (ADS)

Lawrence, Mathias B.; Desa, J. A. E.; Aswal, V. K.

2012-06-01

Poly(Vinyl Alcohol) hydrogels cross-linked with varying concentrations of borax have been studied using Small-Angle Neutron Scattering and X-Ray Diffraction. The intensity of scattering increases with borax concentration from 1 mg/ml up to 2 mg/ml and falls thereafter for 4 mg/ml, increasing again for a concentration of 10 mg/ml. The mesoscopic structural changes that cause these trends in the SANS data are in keeping with the variations in the X-ray diffraction patterns pertaining to structures within the PVA chains.

Modifications of the Mesoscopic Structure of Cellulose in Paper Degradation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Missori, Mauro; Bicchieri, Marina; Mondelli, Claudia

2006-12-08

Paper is the main component of a huge quantity of cultural heritage. It is primarily composed of cellulose that undergoes significant degradation with the passage of time. By using small angle neutron scattering (SANS), we investigated cellulose's supramolecular structure, which allows access to degradation agents, in ancient and modern samples. For the first time, SANS data were interpreted in terms of water-filled pores, with their sizes increasing from 1.61 nm up to 1.97 nm in natural and artificially aged papers. The protective effect of gelatine sizing was also observed.

Structural study of surfactant-dependent interaction with protein

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mehan, Sumit; Aswal, Vinod K., E-mail: vkaswal@barc.gov.in; Kohlbrecher, Joachim

2015-06-24

Small-angle neutron scattering (SANS) has been used to study the complex structure of anionic BSA protein with three different (cationic DTAB, anionic SDS and non-ionic C12E10) surfactants. These systems form very different surfactant-dependent complexes. We show that the structure of protein-surfactant complex is initiated by the site-specific electrostatic interaction between the components, followed by the hydrophobic interaction at high surfactant concentrations. It is also found that hydrophobic interaction is preferred over the electrostatic interaction in deciding the resultant structure of protein-surfactant complexes.

Structural study of surfactant-dependent interaction with protein

NASA Astrophysics Data System (ADS)

Mehan, Sumit; Aswal, Vinod K.; Kohlbrecher, Joachim

2015-06-01

Small-angle neutron scattering (SANS) has been used to study the complex structure of anionic BSA protein with three different (cationic DTAB, anionic SDS and non-ionic C12E10) surfactants. These systems form very different surfactant-dependent complexes. We show that the structure of protein-surfactant complex is initiated by the site-specific electrostatic interaction between the components, followed by the hydrophobic interaction at high surfactant concentrations. It is also found that hydrophobic interaction is preferred over the electrostatic interaction in deciding the resultant structure of protein-surfactant complexes.

Co-existence of monomers and clusters in concentrated protein solutions

NASA Astrophysics Data System (ADS)

Chinchalikar, Akshay J.; Kumar, Sugam; Aswal, V. K.; Callow, P.; Wagh, A. G.

2012-06-01

Small-angle neutron scattering (SANS) measurements have been performed on concentrated protein solutions in order to study aggregation of lysozyme molecules at different pH. The variation of correlation peak in concentration (C) dependent SANS data shows deviation from C1/3 behavior suggesting the aggregation phenomena in these systems. The aggregates or clusters coexist along with monomers with cluster fraction proportional to protein concentration. The clustering is also favored at higher pH approaching isoelectric point (pI) because of decrease in charge on the protein molecule.

Spin-echo small-angle neutron scattering (SESANS) measurements of needle-like crystallites of gelator compounds

NASA Astrophysics Data System (ADS)

Coumou, Pieter-Jan C. J. J.; Brizard, Aurelie M. A.; van Esch, Jan H.; de Schepper, Ignatz M.; Bouwman, Wim G.

2010-11-01

From dibenzoyl cystine, a low molecular weight gelator, we have prepared needle shaped crystals at relatively high concentrations. For the first time SESANS measurements are performed on objects with this geometry. From the measurements the average diameter can be seen directly. From a more careful analysis the width distribution is determined. The gel phase itself prepared at lower concentrations did not show any signal, in contrast to what one observes with conventional SANS. This shows the complementarity of SESANS and SANS.

Structure functions in decomposing CuRh systems

NASA Astrophysics Data System (ADS)

Prem, M.; Blaschko, O.; Rosta, L.

1997-02-01

The time evolution of a CuRh alloy quenched within the miscibility gap is investigated by small and wide angle neutron scattering techniques. Near fundamental Bragg reflections diffuse satellites arising from a lattice parameter modulation induced by the precipitation pattern are investigated. The results show that in CuRh the precipitation morphology and its time evolution are quite different from decomposition characteristics recently observed in the system AuPt. The results are discussed and related to the larger lattice misfit present in CuRh in comparison to AuPt.

Modifications of the Mesoscopic Structure of Cellulose in Paper Degradation

NASA Astrophysics Data System (ADS)

Missori, Mauro; Mondelli, Claudia; de Spirito, Marco; Castellano, Carlo; Bicchieri, Marina; Schweins, Ralf; Arcovito, Giuseppe; Papi, Massimiliano; Castellano, Agostina Congiu

2006-12-01

Paper is the main component of a huge quantity of cultural heritage. It is primarily composed of cellulose that undergoes significant degradation with the passage of time. By using small angle neutron scattering (SANS), we investigated cellulose’s supramolecular structure, which allows access to degradation agents, in ancient and modern samples. For the first time, SANS data were interpreted in terms of water-filled pores, with their sizes increasing from 1.61 nm up to 1.97 nm in natural and artificially aged papers. The protective effect of gelatine sizing was also observed.

Two detector arrays for fast neutrons at LANSCE

NASA Astrophysics Data System (ADS)

Haight, R. C.; Lee, H. Y.; Taddeucci, T. N.; O'Donnell, J. M.; Perdue, B. A.; Fotiades, N.; Devlin, M.; Ullmann, J. L.; Laptev, A.; Bredeweg, T.; Jandel, M.; Nelson, R. O.; Wender, S. A.; White, M. C.; Wu, C. Y.; Kwan, E.; Chyzh, A.; Henderson, R.; Gostic, J.

2012-03-01

The neutron spectrum from neutron-induced fission needs to be known in designing new fast reactors, predicting criticality for safety analyses, and developing techniques for global security application. The experimental data base of fission neutron spectra is very incomplete and most present evaluated libraries are based on the approach of the Los Alamos Model. To validate these models and to provide improved data for applications, a program is underway to measure the fission neutron spectrum for a wide range of incident neutron energies using the spallation source of fast neutrons at the Weapons Neutron Research (WNR) facility at the Los Alamos Neutron Science Center (LANSCE). In a double time-of-flight experiment, fission neutrons are detected by arrays of neutron detectors to increase the solid angle and also to investigate possible angular dependence of the fission neutrons. The challenge is to measure the spectrum from low energies, down to 100 keV or so, to energies over 10 MeV, where the evaporation-like spectrum decreases by 3 orders of magnitude from its peak around 1 MeV. For these measurements, we are developing two arrays of neutron detectors, one based on liquid organic scintillators and the other on 6Li-glass detectors. The range of fission neutrons detected by organic liquid scintillators extends from about 600 keV to well over 10 MeV, with the lower limit being defined by the limit of pulse-shape discrimination. The 6Li-glass detectors have a range from very low energies to about 1 MeV, where their efficiency then becomes small. Various considerations and tests are in progress to understand important contributing factors in designing these two arrays and they include selection and characterization of photomultiplier tubes (PM), the performance of relatively thin (1.8 cm) 6Li-glass scintillators on 12.5 cm diameter PM tubes, use of 17.5 cm diameter liquid scintillators with 12.5 cm PM tubes, measurements of detector efficiencies with tagged neutrons from the WNR/LANSCE neutron beam, and efficiency calibration with 252Cf spontaneous fission neutrons. Design considerations and test results are presented.

Characterizing scintillator detector response for correlated fission experiments with MCNP and associated packages

DOE PAGES

Andrews, M. T.; Rising, M. E.; Meierbachtol, K.; ...

2018-06-15

Wmore » hen multiple neutrons are emitted in a fission event they are correlated in both energy and their relative angle, which may impact the design of safeguards equipment and other instrumentation for non-proliferation applications. The most recent release of MCNP 6 . 2 contains the capability to simulate correlated fission neutrons using the event generators CGMF and FREYA . These radiation transport simulations will be post-processed by the detector response code, DRiFT , and compared directly to correlated fission measurements. DRiFT has been previously compared to single detector measurements, its capabilities have been recently expanded with correlated fission simulations in mind. Finally, this paper details updates to DRiFT specific to correlated fission measurements, including tracking source particle energy of all detector events (and non-events), expanded output formats, and digitizer waveform generation.« less

Characterizing scintillator detector response for correlated fission experiments with MCNP and associated packages

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andrews, M. T.; Rising, M. E.; Meierbachtol, K.

Wmore » hen multiple neutrons are emitted in a fission event they are correlated in both energy and their relative angle, which may impact the design of safeguards equipment and other instrumentation for non-proliferation applications. The most recent release of MCNP 6 . 2 contains the capability to simulate correlated fission neutrons using the event generators CGMF and FREYA . These radiation transport simulations will be post-processed by the detector response code, DRiFT , and compared directly to correlated fission measurements. DRiFT has been previously compared to single detector measurements, its capabilities have been recently expanded with correlated fission simulations in mind. Finally, this paper details updates to DRiFT specific to correlated fission measurements, including tracking source particle energy of all detector events (and non-events), expanded output formats, and digitizer waveform generation.« less

Effect of Melatonin and Cholesterol on the Structure of DOPC and DPPC Membranes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drolle, E; Kucerka, Norbert; Hoopes, M I

The cell membrane plays an important role in the molecular mechanism of amyloid toxicity associated with Alzheimer's disease. The membrane's chemical composition and the incorporation of small molecules, such as melatonin and cholesterol, can alter its structure and physical properties, thereby affecting its interaction with amyloid peptides. Both melatonin and cholesterol have been recently linked to amyloid toxicity. Melatonin has been shown to have a protective role against amyloid toxicity. However, the underlying molecular mechanism of this protection is still not well understood, and cholesterol's role remains controversial. We used small-angle neutron diffraction (SAND) from oriented lipid multi-layers, small-angle neutronmore » scattering (SANS) from unilamellar vesicles experiments andMolecular Dynamics (MD) simulations to elucidate non-specific interactions of melatonin and cholesterol with 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-dipalmitoyl-snglycero-3-phosphocholine (DPPC) model membranes. We conclude that melatonin decreases the thickness of both model membranes by disordering the lipid hydrocarbon chains, thus increasing membrane fluidity. This result is in stark contrast to the much accepted ordering effect induced by cholesterol, which causes membranes to thicken.« less

Structural Significance of Lipid Diversity as Studied by Small Angle Neutron and X-ray Scattering

DOE PAGES

Kučerka, Norbert; Heberle, Frederick A.; Pan, Jianjun; ...

2015-09-21

In this paper, we review recent developments in the rapidly growing field of membrane biophysics, with a focus on the structural properties of single lipid bilayers determined by different scattering techniques, namely neutron and X-ray scattering. The need for accurate lipid structural properties is emphasized by the sometimes conflicting results found in the literature, even in the case of the most studied lipid bilayers. Increasingly, accurate and detailed structural models require more experimental data, such as those from contrast varied neutron scattering and X-ray scattering experiments that are jointly refined with molecular dynamics simulations. This experimental and computational approach producesmore » robust bilayer structural parameters that enable insights, for example, into the interplay between collective membrane properties and its components (e.g., hydrocarbon chain length and unsaturation, and lipid headgroup composition). Finally, from model studies such as these, one is better able to appreciate how a real biological membrane can be tuned by balancing the contributions from the lipid’s different moieties (e.g., acyl chains, headgroups, backbones, etc.).« less

Application of a three-feature dispersed-barrier hardening model to neutron-irradiated Fe-Cr model alloys

NASA Astrophysics Data System (ADS)

Bergner, F.; Pareige, C.; Hernández-Mayoral, M.; Malerba, L.; Heintze, C.

2014-05-01

An attempt is made to quantify the contributions of different types of defect-solute clusters to the total irradiation-induced yield stress increase in neutron-irradiated (300 °C, 0.6 dpa), industrial-purity Fe-Cr model alloys (target Cr contents of 2.5, 5, 9 and 12 at.% Cr). Former work based on the application of transmission electron microscopy, atom probe tomography, and small-angle neutron scattering revealed the formation of dislocation loops, NiSiPCr-enriched clusters and α‧-phase particles, which act as obstacles to dislocation glide. The values of the dimensionless obstacle strength are estimated in the framework of a three-feature dispersed-barrier hardening model. Special attention is paid to the effect of measuring errors, experimental details and model details on the estimates. The three families of obstacles and the hardening model are well capable of reproducing the observed yield stress increase as a function of Cr content, suggesting that the nanostructural features identified experimentally are the main, if not the only, causes of irradiation hardening in these model alloys.

Self-assembled iron oxide nanoparticle multilayer: x-ray and polarized neutron reflectivity.

PubMed

Mishra, D; Benitez, M J; Petracic, O; Badini Confalonieri, G A; Szary, P; Brüssing, F; Theis-Bröhl, K; Devishvili, A; Vorobiev, A; Konovalov, O; Paulus, M; Sternemann, C; Toperverg, B P; Zabel, H

2012-02-10

We have investigated the structure and magnetism of self-assembled, 20 nm diameter iron oxide nanoparticles covered by an oleic acid shell for scrutinizing their structural and magnetic correlations. The nanoparticles were spin-coated on an Si substrate as a single monolayer and as a stack of 5 ML forming a multilayer. X-ray scattering (reflectivity and grazing incidence small-angle scattering) confirms high in-plane hexagonal correlation and a good layering property of the nanoparticles. Using polarized neutron reflectivity we have also determined the long range magnetic correlations parallel and perpendicular to the layers in addition to the structural ones. In a field of 5 kOe we determine a magnetization value of about 80% of the saturation value. At remanence the global magnetization is close to zero. However, polarized neutron reflectivity reveals the existence of regions in which magnetic moments of nanoparticles are well aligned, while losing order over longer distances. These findings confirm that in the nanoparticle assembly the magnetic dipole-dipole interaction is rather strong, dominating the collective magnetic properties at room temperature.

Attenuation of multiples in image space

NASA Astrophysics Data System (ADS)

Alvarez, Gabriel F.

In complex subsurface areas, attenuation of 3D specular and diffracted multiples in data space is difficult and inaccurate. In those areas, image space is an attractive alternative. There are several reasons: (1) migration increases the signal-to-noise ratio of the data; (2) primaries are mapped to coherent events in Subsurface Offset Domain Common Image Gathers (SODCIGs) or Angle Domain Common Image Gathers (ADCIGs); (3) image space is regular and smaller; (4) attenuating the multiples in data space leaves holes in the frequency-Wavenumber space that generate artifacts after migration. I develop a new equation for the residual moveout of specular multiples in ADCIGs and use it for the kernel of an apex-shifted Radon transform to focus and separate the primaries from specular and diffracted multiples. Because of small amplitude, phase and kinematic errors in the multiple estimate, we need adaptive matching and subtraction to estimate the primaries. I pose this problem as an iterative least-squares inversion that simultaneously matches the estimates of primaries and multiples to the data. Standard methods match only the estimate of the multiples. I demonstrate with real and synthetic data that the method produces primaries and multiples with little cross-talk. In 3D, the multiples exhibit residual moveout in SODCIGs in in-line and cross-line offsets. They map away from zero subsurface offsets when migrated with the faster velocity of the primaries. In ADCIGs the residual moveout of the primaries as a function of the aperture angle, for a given azimuth, is flat for those angles that illuminate the reflector. The multiples have residual moveout towards increasing depth for increasing aperture angles at all azimuths. As a function of azimuth, the primaries have better azimuth resolution than the multiples at larger aperture angles. I show, with a real 3D dataset, that even below salt, where illumination is poor, the multiples are well attenuated in ADCIGs with the new Radon transform in planes of azimuth-stacked ADCIGs. The angle stacks of the estimated primaries show little residual multiple energy.

Neutron Scattering Studies of the Interplay of Amyloid β Peptide(1–40) and An Anionic Lipid 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol

DOE PAGES

Rai, Durgesh K.; Sharma, Veerendra K.; Anunciado, Divina; ...

2016-08-09

The interaction between lipid bilayers and Amyloid β peptide (Aβ) plays a critical role in proliferation of Alzheimer’s disease (AD). AD is expected to affect one in every 85 humans by 2050, and therefore, deciphering the interplay of Aβ and lipid bilayers at the molecular level is of profound importance. In this work, we applied an array of neutron scattering methods to study the structure and dynamics of Aβ(1–40) interacting 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG) bilayers. In the structural investigations of lipid bilayer’s response to Aβ binding, Small Angle Neutron Scattering and Neutron Membrane Diffraction revealed that the Aβ anchors firmly to themore » highly charged DMPG bilayers in the interfacial region between water and hydrocarbon chain, and it doesn’t penetrate deeply into the bilayer. This association mode is substantiated by the dynamics studies with high resolution Quasi-Elastic Neutron Scattering experiments, showing that the addition of Aβ mainly affects the slower lateral motion of lipid molecules, especially in the fluid phase, but not the faster internal motion. The results revealed that Aβ associates with the highly charged membrane in surface with limited impact on the structure, but the altered membrane dynamics could have more influence on other membrane processes.« less

In situ neutron scattering study of nanoscale phase evolution in PbTe-PbS thermoelectric material

DOE PAGES

Ren, Fei; Schmidt, Robert; Keum, Jong K.; ...

2016-08-24

Introducing nanostructural second phases has been proved to be an effective approach to reduce the lattice thermal conductivity and thus enhance the figure of merit for many thermoelectric materials. Furthermore studies of the formation and evolution of these second phases are central to understanding temperature dependent material behavior, improving thermal stabilities, as well as designing new materials. We examined powder samples of PbTe-PbS thermoelectric material using in situ neutron diffraction and small angle neutron scattering (SANS) techniques from room temperature to elevated temperature up to 663 K, to explore quantitative information on the structure, weight fraction, and size of themore » second phase. Neutron diffraction data showed the as-milled powder was primarily solid solution before heat treatment. During heating, PbS second phase precipitated out of the PbTe matrix around 480 K, while re-dissolution started around 570 K. The second phase remained separated from the matrix upon cooling. Furthermore, SANS data indicated there are two populations of nanostructures. The size of the smaller nanostructure increased from initially 5 nm to approximately 25 nm after annealing at 650 K, while the size of the larger nanostructure remained unchanged. Our study demonstrated that in situ neutron techniques are effective means to obtain quantitative information to study temperature dependent nanostructural behavior of thermoelectrics and likely other high-temperature materials.« less

Constant- q data representation in Neutron Compton scattering on the VESUVIO spectrometer

NASA Astrophysics Data System (ADS)

Senesi, R.; Pietropaolo, A.; Andreani, C.

2008-09-01

Standard data analysis on the VESUVIO spectrometer at ISIS is carried out within the Impulse Approximation framework, making use of the West scaling variable y. The experiments are performed using the time-of-flight technique with the detectors positioned at constant scattering angles. Line shape analysis is routinely performed in the y-scaling framework, using two different (and equivalent) approaches: (1) fitting the parameters of the recoil peaks directly to fixed-angle time-of-flight spectra; (2) transforming the time-of-flight spectra into fixed-angle y spectra, referred to as the Neutron Compton Profiles, and then fitting the line shape parameters. The present work shows that scattering signals from different fixed-angle detectors can be collected and rebinned to obtain Neutron Compton Profiles at constant wave vector transfer, q, allowing for a suitable interpretation of data in terms of the dynamical structure factor, S(q,ω). The current limits of applicability of such a procedure are discussed in terms of the available q-range and relative uncertainties for the VESUVIO experimental set up and of the main approximations involved.

Neutron production from 200-500 MeV proton interaction with spacecraft materials.

PubMed

Maurer, Richard H; Kinnison, James D; Roth, David R

2005-01-01

We report on detailed energy spectra of neutron production > 14 MeV from collisions of 200-500 MeV protons with combinations of aluminium, graphite and polyethylene. Comparisons of normalised neutron spectra are made with respect to incident proton energy, angle of neutron production and material. In general, carbon (graphite) or polyethylene (by itself or in combination with aluminium) reduce secondary neutron production > 14 MeV relative to the production from interactions in aluminium.

Upgrades to the Polarized Neutron Reflectometer Asterix at LANSCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pynn, Roger

2015-03-16

We have upgraded the polarized neutron reflectometer, Asterix, at the Lujan Neutron Scattering Center at Los Alamos for the benefit of the research communities that study magnetic and complex-fluid films, both of which play important roles in support of the DOE’s energy mission. The upgrades to the instrument include: • A secondary spectrometer that was integrated with a Huber sample goniometer purchased with other funds just prior to the start of our project. The secondary spectrometer provides a flexible length for the scattered flight path, includes a mechanism to select among 3 alternative polarization analyzers as well as a supportmore » for new neutron detectors. Also included is an optic rail for reproducible positioning of components for Spin Echo Scattering Angle Measurement (SESAME). The entire secondary spectrometer is now non-magnetic, as required for neutron Larmor labeling. • A broad-band neutron polarizer for the incident neutron beam based on the V geometry. • A wide-angle neutron polarization analyzer • A 2d position-sensitive neutron detector • Electromagnetic coils (Wollaston prisms) for SESAME plus the associated power supplies, cooling, safety systems and integration into the data acquisition system. The upgrades allowed a nearly effortless transition between configurations required to serve the polarized neutron reflectometry community, users of the 11 T cryomagnet and users of SESAME.« less

Spin structure of the 'Forward' nucleon charge-exchange reaction n + p {yields} p + n and the deuteron charge-exchange breakup

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lyuboshitz, V. L., E-mail: Valery.Lyuboshitz@jinr.ru; Lyuboshitz, V. V.

2011-02-15

The structure of the nucleon charge-exchange process n + p {yields} p + n is investigated basing on the isotopic invariance of the nucleon-nucleon scattering. Using the operator of permutation of the spin projections of the neutron and proton, the connection between the spin matrices, describing the amplitude of the nucleon charge-exchange process at zero angle and the amplitude of the elastic scattering of the neutron on the proton in the 'backward' direction, has been considered. Due to the optical theorem, the spin-independent part of the differential cross section of the process n + p {yields} p + n atmore » zero angle for unpolarized particles is expressed through the difference of total cross sections of unpolarized proton-proton and neutron-proton scattering. Meantime, the spin-dependent part of this cross section is proportional to the differential cross section of the deuteron charge-exchange breakup d + p {yields} (pp) + n at zero angle at the deuteron momentum k{sub d} = 2 k{sub n} (k{sub n} is the initial neutron momentum). Analysis shows that, assuming the real part of the spin-independent term of the 'forward' amplitude of the process n + p {yields} p + n to be smaller or of the same order as compared with the imaginary part, in the wide range of neutron laboratory momenta k{sub n} > 700 MeV/c the main contribution into the differential cross section of the process n + p {yields} p + n at zero angle is provided namely by the spin-dependent term.« less

High-Pressure Neutron Diffraction Studies for Materials Sciences and Energy Sciences

NASA Astrophysics Data System (ADS)

Zhao, Y.; Los Alamos High Pressure Materials Research Team

2013-05-01

The development of neutron diffraction under extreme pressure (P) and temperature (T) conditions is highly valuable to condensed matter physics, crystal chemistry, materials sciences, as well as earth and planetary sciences. We have incorporated a 500-ton press TAP-98 into the HiPPO diffractometer at LANSCE to conduct in situ high P-T neutron diffraction experiments. We have worked out a large gem-crystal anvil cell, ZAP, to conduct neutron diffraction experiments at high-P and low-T. The ZAP cell can be used to integrate multiple experimental techniques such as neutron diffraction, laser spectroscopy, and ultrasonic interferometery. Recently, we have developed high-P low-T gas/fluid cells in conjunction with neutron diffraction and inelastic neutron scattering instruments. These techniques enable in-situ and real-time examination of gas uptake/release processes and allow high-resolution time-dependent determination of changes in crystal structure and related reaction kinetics. We have successfully used these techniques to study the equation of state, structural phase transition, and thermo-mechanical properties of metals, ceramics, and minerals. We have conducted researches on the formation of methane and hydrogen clathrates, and hydrogen adsorption of the inclusion compounds such as the recently discovered metal-organic frameworks (MOFs). The aim of our research is to accurately map phase diagram, lattice parameters, thermal parameters, bond lengths, bond angles, neighboring atomic environments, and phase stability in P-T-X space. We are currently developing further high P-T technology with a new "true" triaxial loading press, TAP_6x, to compress cubic sample package to achieve pressures up to 20 GPa and temperatures up to 2000 K in routine experiments. The implementation of TAP_6x300 with high-pressure neutron beamlines is underway for simultaneous high P-T neutron diffraction, ultrasonic, calorimetry, radiography, and tomography studies. Studies based on high-pressure neutron diffraction are important for multidisciplinary science, particularly for the theoretical/computational modeling/simulations.;

Radiation damage and waste management options for the SOMBRERO final focus system and neutron dumps

DOE Office of Scientific and Technical Information (OSTI.GOV)

Latkowski, J F; Meier, W R; Reyes, S

1999-08-09

Previous studies of the safety and environmental aspects of the SOMBRERO inertial fusion energy (IFE) power plant design did not completely address the issues associated with the final focus system. While past work calculated neutron fluences for a grazing incidence metal mirror (GIMM) and a final focus mirror, scattering off of the final optical component was not included, and thus, fluences in the final focus mirror were significantly underestimated. In addition, past work did not consider neutron-induced gamma-rays. Finally, power plant lifetime waste volumes may have been underestimated as neutron activation of the neutron dumps and building structure were notmore » addressed. In the present work, a modified version of the SOMBRERO target building is presented where a significantly larger open solid-angle fraction (5%) is used to enhance beam smoothing of a diode-pumped solid-state laser (DPSSL). The GIMMs are replaced with transmissive fused silica wedges and have been included in three -dimensional neutron and photon transport calculations. This work shows that a power plant with a large open solid-angle fraction, needed for beam smoothing with a DPSSL, is acceptable from tritium breeding, and neutron activation points-of-view.« less

Small-Angle Neutron Scattering Investigation of Growth Modifiers on Hydrate Crystal Surfaces

NASA Astrophysics Data System (ADS)

Sun, Thomas; Hutter, Jeffrey L.; Lin, M.; King, H. E., Jr.

1998-03-01

Hydrates are crystals consisting of small molecules enclathrated within an ice-like water cage. Suppression of their growth is important in the oil industry. The presence of small quantities of specific polymers during hydrate crystallization can induce a transition from an octahedral to planar growth habit. This symmetry breaking is surprising because of the suppression of two 111 planes relative to the other six crystallographically equivalent faces. To better understand the surface effects leading to this behavior, we have studied the surface adsorption of these growth-modifing polymers onto the hydrate crytals using SANS. The total hydrate surface area, as measured by Porod scattering, increases in the presence of the growth modifier, but, no significant increase in polymer concentration on the crystal surfaces is found. Implications for possible growth mechanisms will be discussed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Casey, D. T., E-mail: casey21@llnl.gov; Munro, D. H.; Grim, G. P.

The Neutron Imaging System at the National Ignition Facility is used to observe the primary ∼14 MeV neutrons from the hotspot and down-scattered neutrons (6-12 MeV) from the assembled shell. Due to the strong spatial dependence of the primary neutron fluence through the dense shell, the down-scattered image is convolved with the primary-neutron fluence much like a backlighter profile. Using a characteristic scattering angle assumption, we estimate the primary neutron fluence and compensate the down-scattered image, which reveals information about asymmetry that is otherwise difficult to extract without invoking complicated models.

Small angle neutron scattering applications in fuel science

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thiyagarajan, P.; Cody, G.D.; Hunt, J.E.

1995-08-01

A wide range of physical and chemical methods have been used to study complex, multicomponent systems in fuel chemistry (crude oil, coal), and we are still far from complete understanding. Since chemical modification and/or solvent extraction of coal result in a number of different systems, it is important to understand the products in terms of their colloidal properties as a function of the solvent type, as well as other physical conditions. This would be helpful in design of processing techniques. Another area of research where SANS can be useful is characterization of the synthetic and modified clays being developed formore » processing in the petroleum industry. Major limitations for performing SANS experiments are nonavailability/high cost sof certain deuterated solvents and the paucity of beam time at the neutron scattering centers. This paper reports briefly on analysis of coal and asphaltenes.« less

Neutron scattering as a probe of liquid crystal polymer-reinforced composite materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hjelm, R.P.; Douglas, E.P.; Benicewicz, B.C.

1995-12-31

This is the final report of a three-year Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). This research project sought to obtain nanoscale and molecular level information on the mechanism of reinforcement in liquid crystal polymer (LCP)-reinforced composites, to realize molecular-reinforced LCP composites, and to test the validity of the concept of molecular reinforcement. Small-angle neutron scattering was used to study the structures in the ternary phase diagram of LCP with liquid crystal thermosets and solvent on length scales ranging from 1-100 nm. The goal of the scattering measurements is to understand the phase morphologymore » and degree of segregation of the reinforcing and matrix components. This information helps elucidate the physics of self assembly in these systems. This work provides an experimental basis for a microengineering approach to composites of vastly improved properties.« less

Magnetic Correlations In A Magnetite Nanoparticle Assembly Investigated Using Polarized SANS

NASA Astrophysics Data System (ADS)

Krycka, Kathryn; Hogg, Charles; Ijiri, Yumi; Booth, Ryan; Borchers, Julie; Chen, Wangchun; Laver, Mark; Gentile, Thomas; Maranville, Brian; Breslauer, Benjamin; Majetich, Sara

2008-03-01

Using small angle neutron scattering (SANS) with polarization analysis, we have studied ferromagnetic magnetite monodisperse nanospheres in order to determine the field (0 and 1.3 Tesla) and temperature (50, 100, and 200 K) dependence of the magnetic interparticle correlations. These particles were 7 nm in diameter with an average edge-to-edge separation of 2.5 nm. Preparation techniques are described elsewhere [1]. An FeSi supermirror polarized the incident neutrons, and a polarized 3He cell was used as a spin analyzer. While a typical magnetic SANS experiment observes the convolution of the nuclear and magnetic terms, we have implemented and further developed an algorithm to separate the four spin dependent cross sections. This provides an unambiguous separation and measurement of magnetic and nuclear contributions. At low temperatures, magnetic correlation lengths have been found to be significantly larger than at high temperatures.[1] J. Am. Chem. Soc. 2002, 124, 8204-8205.

General solution for quantitative dark-field contrast imaging with grating interferometers

NASA Astrophysics Data System (ADS)

Strobl, M.

2014-11-01

Grating interferometer based imaging with X-rays and neutrons has proven to hold huge potential for applications in key research fields conveying biology and medicine as well as engineering and magnetism, respectively. The thereby amenable dark-field imaging modality implied the promise to access structural information beyond reach of direct spatial resolution. However, only here a yet missing approach is reported that finally allows exploiting this outstanding potential for non-destructive materials characterizations. It enables to obtain quantitative structural small angle scattering information combined with up to 3-dimensional spatial image resolution even at lab based x-ray or at neutron sources. The implied two orders of magnitude efficiency gain as compared to currently available techniques in this regime paves the way for unprecedented structural investigations of complex sample systems of interest for material science in a vast range of fields.

Adsorption at air-water and oil-water interfaces and self-assembly in aqueous solution of ethoxylated polysorbate nonionic surfactants.

PubMed

Penfold, Jeffrey; Thomas, Robert K; Li, Peixun X; Petkov, Jordan T; Tucker, Ian; Webster, John R P; Terry, Ann E

2015-03-17

The Tween nonionic surfactants are ethoxylated sorbitan esters, which have 20 ethylene oxide groups attached to the sorbitan headgroup and a single alkyl chain, lauryl, palmityl, stearyl, or oleyl. They are an important class of surfactants that are extensively used in emulsion and foam stabilization and in applications associated with foods, cosmetics and pharmaceuticals. A range of ethoxylated polysorbate surfactants, with differing degrees of ethoxylation from 3 to 50 ethylene oxide groups, have been synthesized and characterized by neutron reflection, small-angle neutron scattering, and surface tension. In conjunction with different alkyl chain groups, this provides the opportunity to modify their surface properties, their self-assembly in solution, and their interaction with macromolecules, such as proteins. Adsorption at the air-water and oil-water interfaces and solution self-assembly of the range of ethoxylated polysorbate surfactants synthesized are presented and discussed.

Neutron studies of paramagnetic fullerenols’ assembly in aqueous solutions

NASA Astrophysics Data System (ADS)

Lebedev, V. T.; Szhogina, A. A.; Suyasova, M. V.

2018-03-01

Recent results on structural studies of aqueous solutions of water-soluble derivatives of endofullerenes encapsulating 4f- and 3d-elements have been presented. Neutron small angle scattering experiments allowed recognize subtle features of fullerenols assembly as dependent on chemical nature (atomic number) of interior atom, pH-factor and temperature of solutions. It was observed a fractal-type fullerenols’ ordering at the scale of correlation radii ∼ 10-20 nm when molecules with iron atoms are integrated into branched structures at low concentrations (C ≤ 1 % wt.) and organized into globular aggregates at higher amounts (C > 1 % wt.). On the other hand, for Lanthanides captured in carbon cages the supramolecular structures are mostly globular and have larger gyration radii ∼ 30 nm. They demonstrated a good stability in acidic (pH ∼ 3) and neutral (pH ∼ 7) media that is important for forthcoming medical applications.

Periodic disorder along ramie cellulose microfibrils.

PubMed

Nishiyama, Yoshiharu; Kim, Ung-Jin; Kim, Dae-Young; Katsumata, Kyoko S; May, Roland P; Langan, Paul

2003-01-01

Small angle neutron scattering studies have been carried out on cellulose fibers from ramie and Populus maximowicii (cotton wood). Labile hydrogen atoms were replaced by deuterium atoms, in water-accessible disordered regions of the fibers, to increase the neutron scattering contrast between the disordered and crystalline regions. A meridional Bragg reflection, corresponding to a longitudinal periodicity of 150 nm, was observed when scattering collected from hydrogenated and deuterated dry ramie fibers was subtracted. No Bragg reflection was observed with the cotton wood fibers, probably because of lower orientation of the microfibrils in the cell wall. The ramie fibers were then subjected to electron microscopy, acid hydrolysis, gel permeation chromatography, and viscosity studies. The leveling off degree of polymerization (LODP) of the hydrolyzed samples matched exactly the periodicity observed in the diffraction studies. The weight loss related to the LODP was only about 1.5%, and thus, the microfibrils can be considered to have 4-5 disordered residues every 300 residues.

Relevance of Internal Friction and Structural Constraints for the Dynamics of Denatured Bovine Serum Albumin.

PubMed

Ameseder, Felix; Radulescu, Aurel; Holderer, Olaf; Falus, Peter; Richter, Dieter; Stadler, Andreas M

2018-05-17

A general property of disordered proteins is their structural expansion that results in a high molecular flexibility. The structure and dynamics of bovine serum albumin (BSA) denatured by guanidinium hydrochloride (GndCl) were investigated using small-angle neutron scattering (SANS) and neutron spin-echo spectroscopy (NSE). SANS experiments demonstrated the relevance of intrachain interactions for structural expansion. Using NSE experiments, we observed a high internal flexibility of denatured BSA in addition to center-of-mass diffusion detected by dynamic light scattering. Internal motions measured by NSE were described using concepts based on polymer theory. The contribution of residue-solvent friction was accounted for using the Zimm model including internal friction (ZIF). Disulfide bonds forming loops of amino acids of the peptide backbone have a major impact on internal dynamics that can be interpreted with a reduced set of Zimm modes.

Neutron-scattering-based evidence for interacting magnetic excitons in LaCo O 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

El-Khatib, S.; Phelan, D.; Barker, J. G.

Recent progress with the thermally-driven spin-state crossover in LaCoO3 has made it increasingly apparent that the nominally non-magnetic low spin ground state of this material actually hosts novel defect-'based magnetism. This is investigated here via a small-angle neutron scattering (SANS) study of LaCoO3-s crystals. The results provide: (i) the surprising finding that the spin-state crossover is clearly reflected in SANS via quasielastic/inelastic scattering from paramagnetic spin fluctuations/excitations, and (ii) evidence for the formation, likely around oxygen defects, of local entities known as magnetic excitons. The latter generate distinct magnetic scattering below 60 K, providing valuable quantitative information on exciton densitiesmore » and interactions. Potential relevance to the unexpected ferromagnetism recently discovered in epitaxial LaCoO3 films is discussed.« less

Effect of pH and Ibuprofen on Phopholipid Bilayer Bending Modulus

NASA Astrophysics Data System (ADS)

Boggara, Mohan; Faraone, Antonio; Krishnamoorti, Ramanan

2010-03-01

Non-steroidal anti-inflammatory drugs (NSAIDs) e.g. Aspirin and Ibuprofen, are known to cause gastrointestinal (GI) toxicity with chronic usage. However, NSAIDs pre-associated with phospholipids has been experimentally shown to reduce the GI toxicity and increase the therapeutic efficacy. In this study, using neutron spin-echo the effect of ibuprofen on the phospholipid membrane bending modulus is studied as a function of pH and temperature. Ibuprofen was found to lower the bending modulus at all pH values. We further present molecular insights into the observed effect on membrane dynamics based on structural studies using molecular dynamics simulations and small angle neutron scattering data as well as changes in zwitterionic headgroup electrostatics due to pH and addition of ibuprofen. This study is expected to help towards effective design of drug delivery nanoparticles based on variety of soft condensed matter such as lipids or polymers.

Anisotropy and multiband superconductivity in Sr 2 RuO 4 determined by small-angle neutron scattering studies of the vortex lattice [Anisotropy and multiband superconductivity in Sr 2 RuO 4

DOE PAGES

Kuhn, S. J.; Morgenlander, W.; Louden, E. R.; ...

2017-11-14

Despite numerous studies the exact nature of the order parameter in superconducting Sr 2RuO 4 remains unresolved. We have extended previous small-angle neutron scattering studies of the vortex lattice in this material to a wider field range, higher temperatures, and with the field applied close to both the <100> and <110> basal plane directions. Measurements at high field were made possible by the use of both spin polarization and analysis to improve the signal-to-noise ratio. Rotating the field towards the basal plane causes a distortion of the square vortex lattice observed for H // <001> and also a symmetry changemore » to a distorted triangular symmetry for fields close to <100>.The vortex lattice distortion allows us to determine the intrinsic superconducting anisotropy between the c axis and the Ru-O basal plane, yielding a value of ~60 at low temperature and low to intermediate fields. This greatly exceeds the upper critical field anisotropy of ~20 at low temperature, reminiscent of Pauli limiting. Indirect evidence for Pauli paramagnetic effects on the unpaired quasiparticles in the vortex cores are observed, but a direct detection lies below the measurement sensitivity. The superconducting anisotropy is found to be independent of temperature but increases for fields > 1 T, indicating multiband superconductvity in Sr 2RuO 4. Lastly, the temperature dependence of the scattered intensity provides further support for gap nodes or deep minima in the superconducting gap.« less

Anisotropy and multiband superconductivity in Sr 2 RuO 4 determined by small-angle neutron scattering studies of the vortex lattice [Anisotropy and multiband superconductivity in Sr 2 RuO 4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuhn, S. J.; Morgenlander, W.; Louden, E. R.

Despite numerous studies the exact nature of the order parameter in superconducting Sr 2RuO 4 remains unresolved. We have extended previous small-angle neutron scattering studies of the vortex lattice in this material to a wider field range, higher temperatures, and with the field applied close to both the <100> and <110> basal plane directions. Measurements at high field were made possible by the use of both spin polarization and analysis to improve the signal-to-noise ratio. Rotating the field towards the basal plane causes a distortion of the square vortex lattice observed for H // <001> and also a symmetry changemore » to a distorted triangular symmetry for fields close to <100>.The vortex lattice distortion allows us to determine the intrinsic superconducting anisotropy between the c axis and the Ru-O basal plane, yielding a value of ~60 at low temperature and low to intermediate fields. This greatly exceeds the upper critical field anisotropy of ~20 at low temperature, reminiscent of Pauli limiting. Indirect evidence for Pauli paramagnetic effects on the unpaired quasiparticles in the vortex cores are observed, but a direct detection lies below the measurement sensitivity. The superconducting anisotropy is found to be independent of temperature but increases for fields > 1 T, indicating multiband superconductvity in Sr 2RuO 4. Lastly, the temperature dependence of the scattered intensity provides further support for gap nodes or deep minima in the superconducting gap.« less

Solution Structure of an Intramembrane Aspartyl Protease via Small Angle Neutron Scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naing, Swe-Htet; Oliver, Ryan C.; Weiss, Kevin L.

Intramembrane aspartyl proteases (IAPs) comprise one of four families of integral membrane proteases that hydrolyze substrates within the hydrophobic lipid bilayer. IAPs include signal peptide peptidase, which processes remnant signal peptides from nascent polypeptides in the endoplasmic reticulum, and presenilin, the catalytic component of the γ-secretase complex that processes Notch and amyloid precursor protein. Despite their broad biomedical reach, basic structure-function relationships of IAPs remain active areas of research. Characterization of membrane-bound proteins is notoriously challenging due to their inherently hydrophobic character. For IAPs, oligomerization state in solution is one outstanding question, with previous proposals for monomer, dimer, tetramer, andmore » octamer. Here we used small angle neutron scattering (SANS) to characterize n-dodecyl-β-D-maltopyranoside (DDM) detergent solutions containing and absent a microbial IAP ortholog. A unique feature of SANS is the ability to modulate the solvent composition to mask all but the enzyme of interest. The signal from the IAP was enhanced by deuteration and, uniquely, scattering from DDM and buffers were matched by the use of both tail-deuterated DDM and D 2O. The radius of gyration calculated for IAP and the corresponding ab initio consensus model are consistent with a monomer. The model is slightly smaller than the crystallographic IAP monomer, suggesting a more compact protein in solution compared with the crystal lattice. In conclusion, our study provides direct insight into the oligomeric state of purified IAP in surfactant solution, and demonstrates the utility of fully contrast-matching the detergent in SANS to characterize other intramembrane proteases and their membrane-bound substrates.« less

Deuterium Labeling Together with Contrast Variation Small-angle Neutron Scattering Suggests How Skp Captures and Releases Unfolded Outer Membrane Proteins

PubMed Central

Zaccai, Nathan R.; Sandlin, Clifford W.; Hoopes, James T.; Curtis, Joseph E.; Fleming, Patrick J.; Fleming, Karen G.; Krueger, Susan

2016-01-01

In gram-negative bacteria, the chaperone protein Skp forms specific and stable complexes with membrane proteins while they are transported across the periplasm to the outer membrane. The jellyfish-like architecture of Skp is similar to the eukaryotic and archeal prefoldins and the mitochondrial Tim chaperones, that is α-helical ‘tentacles’ extend from a β-strand ‘body’ to create an internal cavity. Contrast variation small-angle neutron scattering (SANS) experiments on Skp alone in solution and bound in two different complexes to unfolded outer membrane proteins (uOMPs), OmpA and OmpW, demonstrate that the helical tentacles of Skp bind their substrate in a clamp-like mechanism in a conformation similar to that previously observed in the apo crystal structure of Skp. Deuteration of the uOMP component combined with contrast variation analysis allowed the shapes of Skp and uOMP as well as the location of uOMP with respect to Skp to be determined in both complexes. This represents unique information that could not be obtained without deuterium labeling of the uOMPs. The data yield the first direct structural evidence that the α-helical Skp tentacles move closer together on binding its substrate and that the structure of Skp is different when binding different uOMPs. This work presents, by example, a tutorial on performing SANS experiments using both deuterium labeling and contrast variation, including SANS theory, sample preparation, data collection, sample quality validation, data analysis and structure modeling. PMID:26791979

Positron Annihilation Spectroscopy and Small Angle Neutron Scattering Characterization of Nanostructural Features in Irradiated Fe-Cu-Mn Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wirth, B D; Asoka-Kumar, P; Howell, R H

2001-01-01

Radiation embrittlement of nuclear reactor pressure vessel steels results from a high number density of nanometer sized Cu-Mn-Ni rich precipitates (CRPs) and sub-nanometer matrix features, thought to be vacancy-solute cluster complexes (VSC). However, questions exist regarding both the composition of the precipitates and the defect character and composition of the matrix features. We present results of positron annihilation spectroscopy (PAS) and small angle neutron scattering (SANS) characterization of irradiated and thermally aged Fe-Cu and Fe-Cu-Mn alloys. These complementary techniques provide insight into the composition and character of both types of nanoscale features. The SANS measurements indicate populations of CRPs andmore » VSCs in both alloys. The CRPs are coarser in the Fe-Cu alloy and the number densities of CRP and VSC increase with the addition of Mn. The PAS involved measuring both the positron lifetimes and the Doppler broadened annihilation spectra in the high momentum region to provide elemental sensitivity at the annihilation site. The spectra in Fe-Cu-Mn specimens thermally aged to peak hardness at 450 C and irradiated at 288 C are nearly identical to elemental Cu. Positron lifetime and spectrum measurements in Fe-Cu specimens irradiated at 288 C clearly show the existence of long lifetime ({approx}500 ps) open volume defects, which also contain Cu. Thus the SANS and PAS provide a self-consistent picture of nanostructures composed of CRPs and VSCs and tend to discount high Fe concentrations in the CRPs.« less

Solution Structure of an Intramembrane Aspartyl Protease via Small Angle Neutron Scattering

DOE PAGES

Naing, Swe-Htet; Oliver, Ryan C.; Weiss, Kevin L.; ...

2018-02-06

Intramembrane aspartyl proteases (IAPs) comprise one of four families of integral membrane proteases that hydrolyze substrates within the hydrophobic lipid bilayer. IAPs include signal peptide peptidase, which processes remnant signal peptides from nascent polypeptides in the endoplasmic reticulum, and presenilin, the catalytic component of the γ-secretase complex that processes Notch and amyloid precursor protein. Despite their broad biomedical reach, basic structure-function relationships of IAPs remain active areas of research. Characterization of membrane-bound proteins is notoriously challenging due to their inherently hydrophobic character. For IAPs, oligomerization state in solution is one outstanding question, with previous proposals for monomer, dimer, tetramer, andmore » octamer. Here we used small angle neutron scattering (SANS) to characterize n-dodecyl-β-D-maltopyranoside (DDM) detergent solutions containing and absent a microbial IAP ortholog. A unique feature of SANS is the ability to modulate the solvent composition to mask all but the enzyme of interest. The signal from the IAP was enhanced by deuteration and, uniquely, scattering from DDM and buffers were matched by the use of both tail-deuterated DDM and D 2O. The radius of gyration calculated for IAP and the corresponding ab initio consensus model are consistent with a monomer. The model is slightly smaller than the crystallographic IAP monomer, suggesting a more compact protein in solution compared with the crystal lattice. In conclusion, our study provides direct insight into the oligomeric state of purified IAP in surfactant solution, and demonstrates the utility of fully contrast-matching the detergent in SANS to characterize other intramembrane proteases and their membrane-bound substrates.« less

Deuterium Labeling Together with Contrast Variation Small-Angle Neutron Scattering Suggests How Skp Captures and Releases Unfolded Outer Membrane Proteins.

PubMed

Zaccai, Nathan R; Sandlin, Clifford W; Hoopes, James T; Curtis, Joseph E; Fleming, Patrick J; Fleming, Karen G; Krueger, Susan

2016-01-01

In Gram-negative bacteria, the chaperone protein Skp forms specific and stable complexes with membrane proteins while they are transported across the periplasm to the outer membrane. The jellyfish-like architecture of Skp is similar to the eukaryotic and archaeal prefoldins and the mitochondrial Tim chaperones, that is the α-helical "tentacles" extend from a β-strand "body" to create an internal cavity. Contrast variation small-angle neutron scattering (SANS) experiments on Skp alone in solution and bound in two different complexes to unfolded outer membrane proteins (uOMPs), OmpA and OmpW, demonstrate that the helical tentacles of Skp bind their substrate in a clamp-like mechanism in a conformation similar to that previously observed in the apo crystal structure of Skp. Deuteration of the uOMP component combined with contrast variation analysis allowed the shapes of Skp and uOMP as well as the location of uOMP with respect to Skp to be determined in both complexes. This represents unique information that could not be obtained without deuterium labeling of the uOMPs. The data yield the first direct structural evidence that the α-helical Skp tentacles move closer together on binding its substrate and that the structure of Skp is different when binding different uOMPs. This work presents, by example, a tutorial on performing SANS experiments using both deuterium labeling and contrast variation, including SANS theory, sample preparation, data collection, sample quality validation, data analysis, and structure modeling. © 2016 Elsevier Inc. All rights reserved.

Effective phase function of light scattered at small angles by polydisperse particulate media

NASA Astrophysics Data System (ADS)

Turcu, I.

2008-06-01

Particles with typical dimensions higher than the light wavelength and relative refraction indexes close to one, scatter light mainly in the forward direction where the scattered light intensity has a narrow peak. For particulate media accomplishing these requirements the light scattered at small angles in a far-field detecting set-up can be described analytically by an effective phase function (EPF) even in the multiple scattering regime. The EPF model which was built for monodispersed systems has been extended to polydispersed media. The main ingredients consist in the replacement of the single particle phase function and of the optical thickness with their corresponding averaged values. Using a Gamma particle size distribution (PSD) as a testing model, the effect of polydispersity was systematically investigated. The increase of the average radius or/and of the PSD standard deviation leads to the decrease of the angular spreading of the small angle scattered light.

Characterization of emergent leakage neutrons from multiple layers of hydrogen/water in the lunar regolith by Monte Carlo simulation

NASA Astrophysics Data System (ADS)

SU, J.; Sagdeev, R.; Usikov, D.; Chin, G.; Boyer, L.; Livengood, T. A.; McClanahan, T. P.; Murray, J.; Starr, R. D.

2013-12-01

Introduction: The leakage flux of lunar neutrons produced by precipitation of galactic cosmic ray (GCR) particles in the upper layer of the lunar regolith and measured by orbital instruments such as the Lunar Exploration Neutron Detector (LEND) is investigated by Monte Carlo simulation. Previous Monte Carlo (MC) simulations have been used to investigate neutron production and leakage from the lunar surface to assess the elemental composition of lunar soil [1-6] and its effect on the leakage neutron flux. We investigate effects on the emergent flux that depend on the physical distribution of hydrogen within the regolith. We use the software package GEANT4 [7] to calculate neutron production from spallation by GCR particles [8,9] in the lunar soil. Multiple layers of differing hydrogen/water at different depths in the lunar regolith model are introduced to examine enhancement or suppression of leakage neutron flux. We find that the majority of leakage thermal and epithermal neutrons are produced in 25 cm to 75 cm deep from the lunar surface. Neutrons produced in the shallow top layer retain more of their original energy due to fewer scattering interactions and escape from the lunar surface mostly as fast neutrons. This provides a diagnostic tool in interpreting leakage neutron flux enhancement or suppression due to hydrogen concentration distribution in lunar regolith. We also find that the emitting angular distribution of thermal and epithermal leakage neutrons can be described by cos3/2(theta) where the fast neutrons emitting angular distribution is cos(theta). The energy sensitivity and angular response of the LEND detectors SETN and CSETN are investigated using the leakage neutron spectrum from GEANT4 simulations. A simplified LRO model is used to benchmark MCNPX[10] and GEANT4 on CSETN absolute count rate corresponding to neutron flux from bombardment of 120MV solar potential GCR particles on FAN lunar soil. We are able to interpret the count rates of SETN and CSETN from the leakage neutron spectrum, emission angle, detector energy sensitivity and angular response. Reference: [1] W. C. Feldman, et al., Science 4 September 1998: Vol. 281 no. 5382 pp. 1496-1500. [2] Gasnault, O., et al., (2000) J. Geophys. Res., 105(E2), 4263-4271. [3] Little, R. C., et al. (2003), J. Geophys. Res., 108(E5), 5046. [4] McKinney et al., (2006), J. Geophys. Res., 111, E06004. [5] Lawrence et al., (2006), J. Geophys. Res., 111, E08001. [6] Looper et al, (2013), Space Weather, VOL. 11, 142-152. [7] J. Allison, et al, (2006) IEEE TRANS. ON NUCL SCI, VOL. 53, NO. 1. [8] J. Masarik and R. Reedy (1996), J. Geophys. Res., 101, 18,891-18,912. [9] P. O'Neil (2010) IEEE Trans. Nucl. Sci., 57(6), 3148-3153. [10] D. Pelowitz, (2005), Rep. LA-CP-05-0369, LANL, Los Alamos, NM.

Characterizing ICF Neutron Scintillation Diagnostics on the nTOF line at SUNY Geneseo

NASA Astrophysics Data System (ADS)

Lawson-Keister, Pat; Padawar-Curry, Jonah; Visca, Hannah; Fletcher, Kurt; Padalino, Stephen; Sangster, T. Craig; Regan, Sean

2015-11-01

Neutron scintillator diagnostics for ICF and HEDP can be characterized using the neutron time-of-flight (nTOF) line on Geneseo's 1.7 MV tandem Pelletron accelerator. Neutron signals can be differentiated from gamma signals by employing coincidence methods. A 1.8-MeV beam of deuterons incident on a deuterated polyethylene target produces neutrons via the 2H(d,n)3He reaction. Neutrons emerging at a lab angle of 88° have an energy of 2.96 MeV; the 3He ions associated with these neutrons are detected at a scattering angle of 43° using a surface barrier detector. The time of flight of the neutron can be measured by using the 3He detection as a ``start'' signal and the scintillation detection as a ``stop'' signal. This time of flight requirement is used to identify the 2.96-MeV neutron signals in the scintillator. To measure the light curve produced by these monoenergetic neutrons, two photomultiplier (PMT) tubes are attached to the scintillator. The full aperture PMT establishes the nTOF coincidence. The other PMT is fitted with a pinhole to collect single events. The time between the full aperture PMT signal and the arrival of the signal in the pinhole PMT is used to determine the light curve for the scintillator. This system will enable the neutron response of various scintillators to be compared. Supported in part by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

Design of a transportable high efficiency fast neutron spectrometer

DOE PAGES

Roecker, C.; Bernstein, A.; Bowden, N. S.; ...

2016-04-12

A transportable fast neutron detection system has been designed and constructed for measuring neutron energy spectra and flux ranging from tens to hundreds of MeV. The transportability of the spectrometer reduces the detector-related systematic bias between different neutron spectra and flux measurements, which allows for the comparison of measurements above or below ground. The spectrometer will measure neutron fluxes that are of prohibitively low intensity compared to the site-specific background rates targeted by other transportable fast neutron detection systems. To measure low intensity high-energy neutron fluxes, a conventional capture-gating technique is used for measuring neutron energies above 20 MeV andmore » a novel multiplicity technique is used for measuring neutron energies above 100 MeV. The spectrometer is composed of two Gd containing plastic scintillator detectors arranged around a lead spallation target. To calibrate and characterize the position dependent response of the spectrometer, a Monte Carlo model was developed and used in conjunction with experimental data from gamma ray sources. Multiplicity event identification algorithms were developed and used with a Cf-252 neutron multiplicity source to validate the Monte Carlo model Gd concentration and secondary neutron capture efficiency. The validated Monte Carlo model was used to predict an effective area for the multiplicity and capture gating analyses. For incident neutron energies between 100 MeV and 1000 MeV with an isotropic angular distribution, the multiplicity analysis predicted an effective area of 500 cm 2 rising to 5000 cm 2. For neutron energies above 20 MeV, the capture-gating analysis predicted an effective area between 1800 cm 2 and 2500 cm 2. As a result, the multiplicity mode was found to be sensitive to the incident neutron angular distribution.« less

Angular distribution of diffuse reflectance from incoherent multiple scattering in turbid media.

PubMed

Gao, M; Huang, X; Yang, P; Kattawar, G W

2013-08-20

The angular distribution of diffuse reflection is elucidated with greater understanding by studying a homogeneous turbid medium. We modeled the medium as an infinite slab and studied the reflection dependence on the following three parameters: the incident direction, optical depth, and asymmetry factor. The diffuse reflection is produced by incoherent multiple scattering and is solved through radiative transfer theory. At large optical depths, the angular distribution of the diffuse reflection with small incident angles is similar to that of a Lambertian surface, but, with incident angles larger than 60°, the angular distributions have a prominent reflection peak around the specular reflection angle. These reflection peaks are found originating from the scattering within one transport mean free path in the top layer of the medium. The maximum reflection angles for different incident angles are analyzed and can characterize the structure of angular distributions for different asymmetry factors and optical depths. The properties of the angular distribution can be applied to more complex systems for a better understanding of diffuse reflection.

Neutron Spectroscopy Can Constrain the Composition and Provenance of Phobos and Deimos

NASA Technical Reports Server (NTRS)

Elphic, R. C.; Lee, P.; Zolensky, M. E.; Mittlefehldt, D. W.; Lim, L. F.; Colaprete, A.

2016-01-01

The origin of the martian moons Phobos and Deimos is obscure and enigmatic. Hypotheses include the capture of small bodies originally from the outer main belt or beyond, residual material left over from Mars' formation, and accreted ejecta from a large impact on Mars, among others. Measurements of reflectance spectra indicate a similarity to low-albedo, red D-type asteroids, but could indicate a highly space-weathered veneer. Here we suggest a way of constraining the near-surface composition of the two moons, for comparison with known meteoritic compositions. Neutron spectroscopy, particularly the thermal and epithermal neutron flux, distinguishes clearly between various classes of meteorites and varying hydrogen (water) abundances. Perhaps most surprising of all, a rendezvous with Phobos or Deimos is not necessary to achieve this. Multiple flybys suffice.

Comparison of neutron spectra measured with three sizes of organic liquid scintillators using differentiation analysis

NASA Technical Reports Server (NTRS)

Shook, D. F.; Pierce, C. R.

1972-01-01

Proton recoil distributions were obtained by using organic liquid scintillators of different size. The measured distributions are converted to neutron spectra by differentiation analysis for comparison to the unfolded spectra of the largest scintillator. The approximations involved in the differentiation analysis are indicated to have small effects on the precision of neutron spectra measured with the smaller scintillators but introduce significant error for the largest scintillator. In the case of the smallest cylindrical scintillator, nominally 1.2 by 1.3 cm, the efficiency is shown to be insensitive to multiple scattering and to the angular distribution to the incident flux. These characteristics of the smaller scintillator make possible its use to measure scalar flux spectra within media high efficiency is not required.

Illuminating gravitational waves: A concordant picture of photons from a neutron star merger.

PubMed

Kasliwal, M M; Nakar, E; Singer, L P; Kaplan, D L; Cook, D O; Van Sistine, A; Lau, R M; Fremling, C; Gottlieb, O; Jencson, J E; Adams, S M; Feindt, U; Hotokezaka, K; Ghosh, S; Perley, D A; Yu, P-C; Piran, T; Allison, J R; Anupama, G C; Balasubramanian, A; Bannister, K W; Bally, J; Barnes, J; Barway, S; Bellm, E; Bhalerao, V; Bhattacharya, D; Blagorodnova, N; Bloom, J S; Brady, P R; Cannella, C; Chatterjee, D; Cenko, S B; Cobb, B E; Copperwheat, C; Corsi, A; De, K; Dobie, D; Emery, S W K; Evans, P A; Fox, O D; Frail, D A; Frohmaier, C; Goobar, A; Hallinan, G; Harrison, F; Helou, G; Hinderer, T; Ho, A Y Q; Horesh, A; Ip, W-H; Itoh, R; Kasen, D; Kim, H; Kuin, N P M; Kupfer, T; Lynch, C; Madsen, K; Mazzali, P A; Miller, A A; Mooley, K; Murphy, T; Ngeow, C-C; Nichols, D; Nissanke, S; Nugent, P; Ofek, E O; Qi, H; Quimby, R M; Rosswog, S; Rusu, F; Sadler, E M; Schmidt, P; Sollerman, J; Steele, I; Williamson, A R; Xu, Y; Yan, L; Yatsu, Y; Zhang, C; Zhao, W

2017-12-22

Merging neutron stars offer an excellent laboratory for simultaneously studying strong-field gravity and matter in extreme environments. We establish the physical association of an electromagnetic counterpart (EM170817) with gravitational waves (GW170817) detected from merging neutron stars. By synthesizing a panchromatic data set, we demonstrate that merging neutron stars are a long-sought production site forging heavy elements by r-process nucleosynthesis. The weak gamma rays seen in EM170817 are dissimilar to classical short gamma-ray bursts with ultrarelativistic jets. Instead, we suggest that breakout of a wide-angle, mildly relativistic cocoon engulfing the jet explains the low-luminosity gamma rays, the high-luminosity ultraviolet-optical-infrared, and the delayed radio and x-ray emission. We posit that all neutron star mergers may lead to a wide-angle cocoon breakout, sometimes accompanied by a successful jet and sometimes by a choked jet. Copyright © 2017, American Association for the Advancement of Science.

Measurement of the energy and multiplicity distributions of neutrons from the photofission of U 235

DOE PAGES

Clarke, S. D.; Wieger, B. M.; Enqvist, A.; ...

2017-06-20

For the first time, the complete neutron multiplicity distribution has been measured in this study from the photofission of 235U induced by high-energy spallation γ rays arriving ahead of the neutron beam at the Los Alamos Neutron Science Center. The resulting average neutron multiplicity 3.80 ± 0.08 (stat.) neutrons per photofission is in general agreement with previous measurements. In addition, unique measurements of the prompt fission energy spectrum of the neutrons from photofission and the angular correlation of two-neutron energies emitted in photofission also were made. Finally, the results are compared to calculations with the complete event fission model FREYA.

Fluence-compensated down-scattered neutron imaging using the neutron imaging system at the National Ignition Facility.

PubMed

Casey, D T; Volegov, P L; Merrill, F E; Munro, D H; Grim, G P; Landen, O L; Spears, B K; Fittinghoff, D N; Field, J E; Smalyuk, V A

2016-11-01

The Neutron Imaging System at the National Ignition Facility is used to observe the primary ∼14 MeV neutrons from the hotspot and down-scattered neutrons (6-12 MeV) from the assembled shell. Due to the strong spatial dependence of the primary neutron fluence through the dense shell, the down-scattered image is convolved with the primary-neutron fluence much like a backlighter profile. Using a characteristic scattering angle assumption, we estimate the primary neutron fluence and compensate the down-scattered image, which reveals information about asymmetry that is otherwise difficult to extract without invoking complicated models.

SEARCH FOR SOURCES OF HIGH-ENERGY NEUTRONS WITH FOUR YEARS OF DATA FROM THE ICETOP DETECTOR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aartsen, M. G.; Abraham, K.; Ackermann, M.

IceTop is an air-shower array located on the Antarctic ice sheet at the geographic South Pole. IceTop can detect an astrophysical flux of neutrons from Galactic sources as an excess of cosmic-ray air showers arriving from the source direction. Neutrons are undeflected by the Galactic magnetic field and can typically travel 10 ( E /PeV) pc before decay. Two searches are performed using 4 yr of the IceTop data set to look for a statistically significant excess of events with energies above 10 PeV (10{sup 16} eV) arriving within a small solid angle. The all-sky search method covers from −90°more » to approximately −50° in declination. No significant excess is found. A targeted search is also performed, looking for significant correlation with candidate sources in different target sets. This search uses a higher-energy cut (100 PeV) since most target objects lie beyond 1 kpc. The target sets include pulsars with confirmed TeV energy photon fluxes and high-mass X-ray binaries. No significant correlation is found for any target set. Flux upper limits are determined for both searches, which can constrain Galactic neutron sources and production scenarios.« less

Polarisation analysis on the LET time-of-flight spectrometer

NASA Astrophysics Data System (ADS)

Nilsen, G. J.; Košata, J.; Devonport, M.; Galsworthy, P.; Bewley, R. I.; Voneshen, D. J.; Dalgliesh, R.; Stewart, J. R.

2017-06-01

We present a design for implementing uniaxial polarisation analysis on the LET cold neutron time-of-flight spectrometer, installed on the second target station at ISIS. The polarised neutron beam is to be produced by a transmission-based supermirror polariser with the polarising mirrors arranged in a “double-V” formation. This will be followed by a Mezei-type precession coil spin flipper, selected for its small spatial requirements, as well as a permanent magnet guide field to transport the beam polarisation to the sample position. The sample area will contain a set of holding field coils, whose purpose is to produce a highly homogenous magnetic field for the wide-angle 3He analyser cell. To facilitate fast cell changes and reduce the risk of cell failure, we intend to separate the cell and cryostat from the vacuum of the sample tank by installing both in a vessel at atmospheric pressure. When the instrument upgrade is complete, the performance of LET is expected to be commensurate with existing and planned polarised cold neutron spectrometers at other sources. Finally, we discuss the implications of performing uniaxial polarisation analysis only, and identify quasi-elastic neutron scattering (QENS) on ionic conducting materials as an interesting area to apply the technique.

A feasibility study of the Tehran research reactor as a neutron source for BNCT.

PubMed

Kasesaz, Yaser; Khalafi, Hossein; Rahmani, Faezeh; Ezati, Arsalan; Keyvani, Mehdi; Hossnirokh, Ashkan; Shamami, Mehrdad Azizi; Monshizadeh, Mahdi

2014-08-01

Investigation on the use of the Tehran Research Reactor (TRR) as a neutron source for Boron Neutron Capture Therapy (BNCT) has been performed by calculating and measuring energy spectrum and the spatial distribution of neutrons in all external irradiation facilities, including six beam tubes, thermal column, and the medical room. Activation methods with multiple foils and a copper wire have been used for the mentioned measurements. The results show that (1) the small diameter and long length beam tubes cannot provide sufficient neutron flux for BNCT; (2) in order to use the medical room, the TRR core should be placed in the open pool position, in this situation the distance between the core and patient position is about 400 cm, so neutron flux cannot be sufficient for BNCT; and (3) the best facility which can be adapted for BNCT application is the thermal column, if all graphite blocks can be removed. The epithermal and fast neutron flux at the beginning of this empty column are 4.12×10(9) and 1.21×10(9) n/cm(2)/s, respectively, which can provide an appropriate neutron beam for BNCT by designing and constructing a proper Beam Shaping Assembly (BSA) structure. Copyright © 2014 Elsevier Ltd. All rights reserved.

Influence of the strength of the smectic order on the backbone anisotropy of side-chain liquid crystal polymers as revealed by SANS

NASA Astrophysics Data System (ADS)

Noirez, L.; Keller, P.; Cotton, J. P.

1992-06-01

It is proposed that the strength of the smectic order determines the backbone anisotropy of side-chain liquid crystal polymers. Here this strength increases with the length of the alkyl terminal group of the mesogens. Two liquid crystal polymethacrylates differing only by the mesogenic tails —OCH3 and —OC4H9 are considered. The backbone anisotropy of these polymers is measured by small angle neutron scattering (SANS) whereas the smectic order is evaluated from the intensity of the 001 Bragg peak. Il est proposé que la qualité de l'ordre smectique détermine l'anisotropie du squelette de polymères mésomorphes en peigne confinés dans les lamelles. Ici l'ordre smectique est augmenté en allongeant le groupe alkyl terminal des mésogènes. Nous étudions deux polyméthacrylates cristal liquide qui ne différent que par leurs groupes terminaux : —OCH3 et —OC4H9. L'anisotropie du squellete est mesurée par diffusion de neutrons aux petits angles tandis que l'ordre smectique est évalué à l'aide de l'intensité du pic de Bragg 001.

Complex Contact Angles Calculated from Capillary Rise Measurements on Rock Fracture Faces

NASA Astrophysics Data System (ADS)

Perfect, E.; Gates, C. H.; Brabazon, J. W.; Santodonato, L. J.; Dhiman, I.; Bilheux, H.; Bilheux, J. C.; Lokitz, B. S.

2017-12-01

Contact angles for fluids in unconventional reservoir rocks are needed for modeling hydraulic fracturing leakoff and subsequent oil and gas extraction. Contact angle measurements for wetting fluids on rocks are normally performed using polished flat surfaces. However, such prepared surfaces are not representative of natural rock fracture faces, which have been shown to be rough over multiple scales. We applied a variant of the Wilhelmy plate method for determining contact angle from the height of capillary rise on a vertical surface to the wetting of rock fracture faces by water in the presence of air. Cylindrical core samples (5.05 cm long x 2.54 cm diameter) of Mancos shale and 6 other rock types were investigated. Mode I fractures were created within the cores using the Brazilian method. Each fractured core was then separated into halves exposing the fracture faces. One fracture face from each rock type was oriented parallel to a collimated neutron beam in the CG-1D imaging instrument at ORNL's High Flux Isotope Reactor. Neutron radiography was performed using the multi-channel plate detector with a spatial resolution of 50 μm. Images were acquired every 60 s after a water reservoir contacted the base of the fracture face. The images were normalized to the initial dry condition so that the upward movement of water on the fracture face was clearly visible. The height of wetting at equilibrium was measured on the normalized images using ImageJ. Contact angles were also measured on polished flat surfaces using the conventional sessile drop method. Equilibrium capillary rise on the exposed fracture faces was up to 8.5 times greater than that predicted for polished flat surfaces from the sessile drop measurements. These results indicate that rock fracture faces are hyperhydrophilic (i.e., the height of capillary rise is greater than that predicted for a contact angle of zero degrees). The use of complex numbers permitted calculation of imaginary contact angles for such surfaces. This analysis yielded a continuum of contact angles (real above, and imaginary below, zero degrees) that can be used to investigate relationships with properties such surface roughness and porosity. It should be noted these are preliminary, unreplicated results and further research will be needed to verify them and refine the approach.

Confinement-Driven Phase Separation of Quantum Liquid Mixtures

NASA Astrophysics Data System (ADS)

Prisk, T. R.; Pantalei, C.; Kaiser, H.; Sokol, P. E.

2012-08-01

We report small-angle neutron scattering studies of liquid helium mixtures confined in Mobil Crystalline Material-41 (MCM-41), a porous silica glass with narrow cylindrical nanopores (d=3.4nm). MCM-41 is an ideal model adsorbent for fundamental studies of gas sorption in porous media because its monodisperse pores are arranged in a 2D triangular lattice. The small-angle scattering consists of a series of diffraction peaks whose intensities are determined by how the imbibed liquid fills the pores. Pure He4 adsorbed in the pores show classic, layer-by-layer film growth as a function of pore filling, leaving the long range symmetry of the system intact. In contrast, the adsorption of He3-He4 mixtures produces a structure incommensurate with the pore lattice. Neither capillary condensation nor preferential adsorption of one helium isotope to the pore walls can provide the symmetry-breaking mechanism. The scattering is consistent with the formation of randomly distributed liquid-liquid microdomains ˜2.3nm in size, providing evidence that confinement in a nanometer scale capillary can drive local phase separation in quantum liquid mixtures.

Block and Gradient Copoly(2-oxazoline) Micelles: Strikingly Different on the Inside.

PubMed

Filippov, Sergey K; Verbraeken, Bart; Konarev, Petr V; Svergun, Dmitri I; Angelov, Borislav; Vishnevetskaya, Natalya S; Papadakis, Christine M; Rogers, Sarah; Radulescu, Aurel; Courtin, Tim; Martins, José C; Starovoytova, Larisa; Hruby, Martin; Stepanek, Petr; Kravchenko, Vitaly S; Potemkin, Igor I; Hoogenboom, Richard

2017-08-17

Herein, we provide a direct proof for differences in the micellar structure of amphiphilic diblock and gradient copolymers, thereby unambiguously demonstrating the influence of monomer distribution along the polymer chains on the micellization behavior. The internal structure of amphiphilic block and gradient co poly(2-oxazolines) based on the hydrophilic poly(2-methyl-2-oxazoline) (PMeOx) and the hydrophobic poly(2-phenyl-2-oxazoline) (PPhOx) was studied in water and water-ethanol mixtures by small-angle X-ray scattering (SAXS), small-angle neutron scattering (SANS), static and dynamic light scattering (SLS/DLS), and 1 H NMR spectroscopy. Contrast matching SANS experiments revealed that block copolymers form micelles with a uniform density profile of the core. In contrast to popular assumption, the outer part of the core of the gradient copolymer micelles has a distinctly higher density than the middle of the core. We attribute the latter finding to back-folding of chains resulting from hydrophilic-hydrophobic interactions, leading to a new type of micelles that we refer to as micelles with a "bitterball-core" structure.

Neutron Scattering Studies of Vortex Matter in Type-II Superconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xinsheng Ling

2012-02-02

The proposed program is an experimental study of the fundamental properties of Abrikosov vortex matter in type-II superconductors. Most superconducting materials used in applications such as MRI are type II and their transport properties are determined by the interplay between random pinning, interaction and thermal fluctuation effects in the vortex state. Given the technological importance of these materials, a fundamental understanding of the vortex matter is necessary. The vortex lines in type-II superconductors also form a useful model system for fundamental studies of a number of important issues in condensed matter physics, such as the presence of a symmetry-breaking phasemore » transition in the presence of random pinning. Recent advances in neutron scattering facilities such as the major upgrade of the NIST cold source and the Spallation Neutron Source are providing unprecedented opportunities in addressing some of the longstanding issues in vortex physics. The core component of the proposed program is to use small angle neutron scattering and Bitter decoration experiments to provide the most stringent test of the Bragg glass theory by measuring the structure factor in both the real and reciprocal spaces. The proposed experiments include a neutron reflectometry experiment to measure the precise Q-dependence of the structure factor of the vortex lattice in the Bragg glass state. A second set of SANS experiments will be on a shear-strained Nb single crystal for testing a recently proposed theory of the stability of Bragg glass. The objective is to artificially create a set of parallel grain boundaries into a Nb single crystal and use SANS to measure the vortex matter diffraction pattern as a function of the changing angle between the applied magnetic field to the grain boundaries. The intrinsic merits of the proposed work are a new fundamental understanding of type-II superconductors on which superconducting technology is based, and a firm understanding of phases and phase transitions in condensed matter systems with random pinning. The broader impact of the program includes the training of future generation of neutron scientists, and further development of neutron scattering and complementary techniques for studies of superconducting materials. The graduate and undergraduate students participating in this project will learn the state-of-the-art neutron scattering techniques, acquire a wide range of materials research experiences, and participate in the frontier research of superconductivity. This should best prepare the students for future careers in academia, industry, or government.« less

2011 U.S. National School on Neutron and X-ray Scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lang, Jonathan; te Vethuis, Suzanne; Ekkebus, Allen E

The 13th annual U.S. National School on Neutron and X-ray Scattering was held June 11 to 25, 2011, at both Oak Ridge and Argonne National Laboratories. This school brought together 65 early career graduate students from 56 different universities in the US and provided them with a broad introduction to the techniques available at the major large-scale neutron and synchrotron x-ray facilities. This school is focused primarily on techniques relevant to the physical sciences, but also touches on cross-disciplinary bio-related scattering measurements. During the school, students received lectures by over 30 researchers from academia, industry, and national laboratories and participatedmore » in a number of short demonstration experiments at Argonne's Advanced Photon Source (APS) and Oak Ridge's Spallation neutron Source (SNS) and High Flux Isotope Reactor (HFIR) facilities to get hands-on experience in using neutron and synchrotron sources. The first week of this year's school was held at Oak Ridge National Lab, where Lab director Thom Mason welcomed the students and provided a shitorical perspective of the neutron and x-ray facilities both at Oak Ridge and Argonne. The first few days of the school were dedicated to lectures laying out the basics of scattering theory and the differences and complementarity between the neutron and x-ray probes given by Sunil Sinha. Jack Carpenter provided an introduction into how neutrons are generated and detected. After this basic introduction, the students received lectures each morning on specific techniques and conducted demonstration experiments each afternoon on one of 15 different instruments at either the SNS or HFIR. Some of the topics covered during this week of the school included inelastic neutron scattering by Bruce Gaulin, x-ray and neutron reflectivity by Chuck Majkrazak, small-angle scattering by Volker Urban, powder diffraction by Ashfia Huq and diffuse scattering by Gene Ice.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roecker, C.; Bernstein, A.; Bowden, N. S.

A transportable fast neutron detection system has been designed and constructed for measuring neutron energy spectra and flux ranging from tens to hundreds of MeV. The transportability of the spectrometer reduces the detector-related systematic bias between different neutron spectra and flux measurements, which allows for the comparison of measurements above or below ground. The spectrometer will measure neutron fluxes that are of prohibitively low intensity compared to the site-specific background rates targeted by other transportable fast neutron detection systems. To measure low intensity high-energy neutron fluxes, a conventional capture-gating technique is used for measuring neutron energies above 20 MeV andmore » a novel multiplicity technique is used for measuring neutron energies above 100 MeV. The spectrometer is composed of two Gd containing plastic scintillator detectors arranged around a lead spallation target. To calibrate and characterize the position dependent response of the spectrometer, a Monte Carlo model was developed and used in conjunction with experimental data from gamma ray sources. Multiplicity event identification algorithms were developed and used with a Cf-252 neutron multiplicity source to validate the Monte Carlo model Gd concentration and secondary neutron capture efficiency. The validated Monte Carlo model was used to predict an effective area for the multiplicity and capture gating analyses. For incident neutron energies between 100 MeV and 1000 MeV with an isotropic angular distribution, the multiplicity analysis predicted an effective area of 500 cm 2 rising to 5000 cm 2. For neutron energies above 20 MeV, the capture-gating analysis predicted an effective area between 1800 cm 2 and 2500 cm 2. As a result, the multiplicity mode was found to be sensitive to the incident neutron angular distribution.« less

Multiple scattering corrections to the Beer-Lambert law. 1: Open detector.

PubMed

Tam, W G; Zardecki, A

1982-07-01

Multiple scattering corrections to the Beer-Lambert law are analyzed by means of a rigorous small-angle solution to the radiative transfer equation. Transmission functions for predicting the received radiant power-a directly measured quantity in contrast to the spectral radiance in the Beer-Lambert law-are derived. Numerical algorithms and results relating to the multiple scattering effects for laser propagation in fog, cloud, and rain are presented.

COMPTEL neutron response at 17 MeV

NASA Technical Reports Server (NTRS)

Oneill, Terrence J.; Ait-Ouamer, Farid; Morris, Joann; Tumer, O. Tumay; White, R. Stephen; Zych, Allen D.

1992-01-01

The Compton imaging telescope (COMPTEL) instrument of the Gamma Ray Observatory was exposed to 17 MeV d,t neutrons prior to launch. These data were analyzed and compared with Monte Carlo calculations using the MCNP(LANL) code. Energy and angular resolutions are compared and absolute efficiencies are calculated at 0 and 30 degrees incident angle. The COMPTEL neutron responses at 17 MeV and higher energies are needed to understand solar flare neutron data.

Prompt Fission Neutron Multiplicities for 241Pu using Surrogate Reactions

NASA Astrophysics Data System (ADS)

Akindele, Oluwatomi; Burke, Jason; Casperson, Robert; Hughes, Richard; Norman, Eric; Saastamoinen, Antti; Wang, Barbara

2017-09-01

The prompt fission neutron multiplicity for 241Pu was measured at the Texas A&M University Cyclotron using the NeutronSTARS array. Due to the short half-life (14.3 yrs) of 241Pu, inelastic scattering on 242Pu with 55 MeV alpha particles was used as a surrogate. The average neutron multiplicity (ν), and the neutron multiplicity distribution for equivalent neutron energies up to 20 MeV are discussed and reported. This work was performed under the auspices of the U.S. DOE by LLNL under contract DE-AC52-07NA27344, and supported by the DOE NNSA under Award Number DE-NA0000979, and through the Nuclear Science and Security Consortium under Award Number DE-NA-0003180.

Epithermal neutron beams from the 7 Li(p,n) reaction near the threshold for neutron capture therapy

NASA Astrophysics Data System (ADS)

Porras, I.; Praena, J.; Arias de Saavedra, F.; Pedrosa, M.; Esquinas, P.; L. Jiménez-Bonilla, P.

2016-11-01

Two applications for neutron capture therapy of epithermal neutron beams calculated from the 7Li ( p , n reaction are discussed. In particular, i) for a proton beam of 1920 keV of a 30 mA, a neutron beam of adequate features for BNCT is found at an angle of 80° from the forward direction; and ii) for a proton beam of 1910 keV, a neutron beam is obtained at the forward direction suitable for performing radiobiology experiments for the determination of the biological weighting factors of the fast dose component in neutron capture therapy.

From X-Ray Telescopes to Neutron Focusing

NASA Technical Reports Server (NTRS)

Gubarev, M. V.; Khaykovich, B.; Ramsey, B.; Moncton, D. E.

2011-01-01

In the case of neutrons the refractive index is slightly less than unity for most elements and their isotopes. Consequently, thermal and cold neutrons can be reflected from smooth surfaces at grazing-incidence angles. Hence, the optical technologies developed for x-ray astronomy can be applied for neutron focusing. The focusing capabilities of grazing incidence neutron imaging optics have been successfully demonstrated using nickel mirrors. The mirrors were fabricated using an electroformed nickel replication process at Marshall Space Flight Center. Results of the neutron optics experiments will be presented. Challenges of the neutron imaging optics as well as possible applications of the optics will be discussed.

Geometry Survey of the Time-of-Flight Neutron-Elastic Scattering (Antonella) Experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oshinowo, Babatunde O.; Izraelevitch, Federico

The Antonella experiment is a measurement of the ionization efficiency of nuclear recoils in silicon at low energies [1]. It is a neutron elastic scattering experiment motivated by the search for dark matter particles. In this experiment, a proton beam hits a lithium target and neutrons are produced. The neutron shower passes through a collimator that produces a neutron beam. The beam illuminates a silicon detector. With a certain probability, a neutron interacts with a silicon nucleus of the detector producing elastic scattering. After the interaction, a fraction of the neutron energy is transferred to the silicon nucleus which acquiresmore » kinetic energy and recoils. This kinetic energy is then dissipated in the detector producing ionization and thermal energy. The ionization produced is measured with the silicon detector electronics. On the other hand, the neutron is scattered out of the beam. A neutron-detector array (made of scintillator bars) registers the neutron arrival time and the scattering angle to reconstruct the kinematics of the neutron-nucleus interaction with the time-of-flight technique [2]. In the reconstruction equations, the energy of the nuclear recoil is a function of the scattering angle with respect to the beam direction, the time-of-flight of the neutron and the geometric distances between components of the setup (neutron-production target, silicon detector, scintillator bars). This paper summarizes the survey of the different components of the experiment that made possible the off-line analysis of the collected data. Measurements were made with the API Radian Laser Tracker and I-360 Probe Wireless. The survey was completed at the University of Notre Dame, Indiana, USA in February 2015.« less

Resolving 3D magnetism in nanoparticles using polarization analyzed SANS

NASA Astrophysics Data System (ADS)

Krycka, K. L.; Booth, R.; Borchers, J. A.; Chen, W. C.; Conlon, C.; Gentile, T. R.; Hogg, C.; Ijiri, Y.; Laver, M.; Maranville, B. B.; Majetich, S. A.; Rhyne, J. J.; Watson, S. M.

2009-09-01

Utilizing a polarized 3He cell as an analyzer we were able to perform a full polarization analysis on small-angle neutron scattering (SANS) data from an ensemble of 7 nm magnetite nanoparticles. The results led to clear separation of magnetic and nuclear scattering plus a 3D vectorial decomposition of the magnetism observed. At remanence variation in long-range magnetic correlation length was found to be highly dependent on temperature from 50 to 300 K. Additionally, we were able to compare the magnetic scattering from moments along and perpendicular to an applied field at saturation and in remanence.

Core-Shell Magnetic Morphology of Structurally Uniform Magnetite Nanoparticles

NASA Astrophysics Data System (ADS)

Krycka, K. L.; Booth, R. A.; Hogg, C. R.; Ijiri, Y.; Borchers, J. A.; Chen, W. C.; Watson, S. M.; Laver, M.; Gentile, T. R.; Dedon, L. R.; Harris, S.; Rhyne, J. J.; Majetich, S. A.

2010-05-01

A new development in small-angle neutron scattering with polarization analysis allows us to directly extract the average spatial distributions of magnetic moments and their correlations with three-dimensional directional sensitivity in any magnetic field. Applied to a collection of spherical magnetite nanoparticles 9.0 nm in diameter, this enhanced method reveals uniformly canted, magnetically active shells in a nominally saturating field of 1.2 T. The shell thickness depends on temperature, and it disappears altogether when the external field is removed, confirming that these canted nanoparticle shells are magnetic, rather than structural, in origin.

Proceedings of the Annual Conference on Magnetism and Magnetic Materials (38th) Held at Minneapolis, Minnesota on 15-18 November 1993. (Journal of Applied Physics. Volume 75, Number 10, Part 28

DTIC Science & Technology

1994-05-15

Nogues superconducting quantum interference device magnetometry and small-angle neutron-scattering techniques 5829 Thermodynamical properties of a...sa’nple magnetometer (VSM) and superconducting Coey et al.1 have been extensively studied during the past quantum interference device (SQUID) were used to...were measured in a superconducting quantum- interference 30 device magnetometer at 273 K. 20 e 10 U1 Y3 U RESULTS - C0 20 40 60 80 100 Phase relations

Experimental evidence for two thermodynamic length scales in neutralized polyacrylate gels

NASA Astrophysics Data System (ADS)

Horkay, Ferenc; Hecht, Anne-Marie; Grillo, Isabelle; Basser, Peter J.; Geissler, Erik

2002-11-01

The small angle neutron scattering (SANS) behavior of fully neutralized sodium polyacrylate gels is investigated in the presence of calcium ions. Analysis of the SANS response reveals the existence of three characteristic length scales, two of which are of thermodynamic origin, while the third length is associated with the frozen-in structural inhomogeneities. This latter contribution exhibits power law behavior with a slope of about -3.6, reflecting the presence of interfaces. The osmotically active component of the scattering signal is defined by two characteristic length scales, a correlation length ξ and a persistence length L.

The Morphology of Titanium Dioxide Aerogels

NASA Astrophysics Data System (ADS)

Zhu, Zhu

The morphology of titanium dioxide TiO _2 aerogels has been characterized by four major techniques. This work will discuss these complementary techniques such as nitrogen adsorption, X-ray powder diffraction (XRD), electron microscopies (EM- TEM, SEM), and small angle neutron scattering (SANS). The results of these characterizations have shown that the morphology of titanium dioxide TiO_2 aerogels can be characterized in terms of two length scales: 5 nm diameter, crystalline nanoparticles of anatase closely packed into mesoaggregates about 50 nm in size. The mesoaggregates are, in turn, packed into a loosely linked structure with an overall porosity of 80%.

Microstructural studies of nanocrystalline α-alumina powder produced from Al13-cluster

NASA Astrophysics Data System (ADS)

Harun Al Rashid Megat Ahmad, Megat; Aziz Mohamed, Abdul; Ibrahim, Azmi; Seman Mahmood, Che; Giri Rachman Putra, Edy; Jamro, Rafhayudi; Kasim, Razali; Rawi Muhammad Zin, Muhammad

2007-12-01

Nanocrystalline alumina powder was produced from calcinations of Al13-oxalate precipitates at 1100 °C. A nearly normal distribution of agglomerated alumina powder was obtained with an average particle size of about 1 μm. XRD measurement confirmed that the alumina produced was of high purity and crystalline α-phase. Microstructural features of both the precipitates and alumina obtained were studied using the small angle neutron scattering (SANS) technique. SANS examinations show the formation of microstructures in the alumina powder of mass fractals type with dimension of ˜2.8 indicative of low intra-granular porosity.

Solid-State Division progress report for period ending March 31, 1983

DOE Office of Scientific and Technical Information (OSTI.GOV)

Green, P.H.; Watson, D.M.

1983-09-01

Progress and activities are reported on: theoretical solid-state physics (surfaces; electronic, vibrational, and magnetic properties; particle-solid interactions; laser annealing), surface and near-surface properties of solids (surface, plasma-material interactions, ion implantation and ion-beam mixing, pulsed-laser and thermal processing), defects in solids (radiation effects, fracture, impurities and defects, semiconductor physics and photovoltaic conversion), transport properties of solids (fast-ion conductors, superconductivity, mass and charge transport in materials), neutron scattering (small-angle scattering, lattice dynamics, magnetic properties, structure and instrumentation), and preparation and characterization of research materials (growth and preparative methods, nuclear waste forms, special materials). (DLC)

Role of electrostatic interaction on surfactant induced protein unfolding

NASA Astrophysics Data System (ADS)

Sumit, Kumar, Sugam; Aswal, V. K.

2013-02-01

Small Angle Neutron Scattering has been used to examine the effect of electrostatic interaction on surfactant induced protein unfolding. Measurements are carried out from 1 wt% Bovine Serum Albumin (BSA) protein with 1 wt% Sodium Dodecyl Sulphate (SDS) surfactant at pH 7 in presence of varying concentration of NaCl. It is found that both the components (protein and surfactant micelle which are likely charged) exist individually without any interaction in absence of salt, whereas their interaction and protein unfolding is enhanced with the increase in salt concentration. The structure of protein-surfactant interaction is characterized by fractal bead-necklace model.

Structure of aqueous proline via parallel tempering molecular dynamics and neutron diffraction.

PubMed

Troitzsch, R Z; Martyna, G J; McLain, S E; Soper, A K; Crain, J

2007-07-19

The structure of aqueous L-proline amino acid has been the subject of much debate centering on the validity of various proposed models, differing widely in the extent to which local and long-range correlations are present. Here, aqueous proline is investigated by atomistic, replica exchange molecular dynamics simulations, and the results are compared to neutron diffraction and small angle neutron scattering (SANS) data, which have been reported recently (McLain, S.; Soper, A.; Terry, A.; Watts, A. J. Phys. Chem. B 2007, 111, 4568). Comparisons between neutron experiments and simulation are made via the static structure factor S(Q) which is measured and computed from several systems with different H/D isotopic compositions at a concentration of 1:20 molar ratio. Several different empirical water models (TIP3P, TIP4P, and SPC/E) in conjunction with the CHARMM22 force field are investigated. Agreement between experiment and simulation is reasonably good across the entire Q range although there are significant model-dependent variations in some cases. In general, agreement is improved slightly upon application of approximate quantum corrections obtained from gas-phase path integral simulations. Dimers and short oligomeric chains formed by hydrogen bonds (frequently bifurcated) coexist with apolar (hydrophobic) contacts. These emerge as the dominant local motifs in the mixture. Evidence for long-range association is more equivocal: No long-range structures form spontaneously in the MD simulations, and no obvious low-Q signature is seen in the SANS data. Moreover, associations introduced artificially to replicate a long-standing proposed mesoscale structure for proline correlations as an initial condition are annealed out by parallel tempering MD simulations. However, some small residual aggregates do remain, implying a greater degree of long-range order than is apparent in the SANS data.