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At least 235 records · Page 13

Signatures of Thermoreversible Associations in X-ray and Neutron Scattering from Dilute Polyzwitterion Solutions

In aqueous solutions of polyzwitterions (PZs), an interplay between dipole–dipole interactions and hydration of zwitterionic groups can lead to thermoreversible associations, which have been difficult to detect in experiments. Here, in this study, we investigated dilute aqueous solutions of poly(1-(3-sulphonatopropyl)-2-vinylpyridinium) (P2VPPS) using small-angle X-ray and neutron scattering (SAXS and SANS) to probe the structure and neutron spin-echo (NSE) spectroscopy to probe dynamics. The SAXS and SANS data show that the correlation length increases with an increase in the concentration of P2VPPS for three different molecular weights. The addition of 0.1 M NaCl to one of the solutions led to almost no dependence of the correlation length on the concentration. Such a concentration dependence of the correlation length suggests the formation of clusters driven by thermoreversible associations in the solutions. The NSE measurements show that the solutions with a larger correlation length display slower relaxation, reflecting the reduced mobility of larger clusters. These results should be considered as signatures of thermoreversible associations in the solutions of P2VPPS. To establish a quantitative link between local structure (clusters) and dynamics in dilute solutions of P2VPPS, we combined a thermoreversible gelation theory for the structure of PZ solutions (Li, S.-F.; Muthukumar, M. Theory of Thermoreversible Gelation and Anomalous Concentration Fluctuations in Polyzwitterion Solutions. J. Chem. Phys. 2024, 161, 024903) with a model for the dynamics of the clusters (generalized Zimm model), developed in this work. Using such a theoretical framework, we have predicted the distribution of clusters in the solutions probed with SANS and SAXS. With the distributions, the generalized Zimm model has been used to extract the diffusion constant of the clusters and their characteristic size from the NSE data, where the latter agrees with the values estimated from the SAXS/SANS data. These findings confirm the presence of thermoreversible associations and establish a quantitative link between local structure (clusters) and dynamics in dilute solutions of P2VPPS. Furthermore, with growing interest in technological applications, this work can provide useful insights into the structural and dynamical properties of other PZ solutions.

field theory↗

Structural Insights into Low and High Recalcitrance Natural Poplar Variants Using Neutron and X-ray Scattering

Here, we used small-angle neutron scattering (SANS) and wide-angle X-ray scattering (WAXS) to study two Populus trichocarpa variants, GW-11012 and BESC-316, with lignin contents of 17.8 and 23.2%, respectively, to understand why the low lignin variant has increased sugar release during liquid hot water (LHW) pretreatment. SANS showed differences in cell wall polymer arrangement in the variants. In GW-11012, the cellulose microfibrils were similar in size to BESC-316 but were not equally spaced and lignin was aggregated rather than homogenously interspersed with other matrix co-polymers. However, after LHW pretreatments, the SANS profiles of the pretreated variants were almost indistinguishable, indicating that the nanoscale structural features could not adequately explain the increased sugar release observed in GW-11012. WAXS analysis revealed higher cellulose crystallinity and larger crystallite size in native and pretreated GW-11012. However, the most significant difference was that the crystallite orientation was approximately 2-fold higher in GW-11012. This suggests that higher crystallite orientation may be favorable for the action of processive cellulases leading to increased sugar release from GW-11012. Our study shows that there is a complex interplay between cell wall polymers during their deposition resulting in changes in lignin distribution and cellulose structure, highlighting the importance of investigating plant cell wall architecture across multiple length scales.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Variations of Stress Parameters in the Southern California Plate Boundary Around the South Central Transverse Ranges

We examine the stress field in Southern California with a focus on the region near the South Central Transverse Ranges (SCTR), using a refined stress inversion methodology. We independently invert declustered and aftershocks focal mechanisms from the years 1981 to 2017. Comparisons between the stress field orientations and the stress ratios from these inversions provide information on local sources of the stress field. Regionally, the SHmax tends to be toward NNE and the stress ratios vary from transtensional stress regime near the Eastern California Shear Zone (ECSZ), to strike-slip faulting near the SCTR, and toward transpression near the Western Transverse Ranges. Detailed analysis of stress parameters near the SCTR indicates deviations from the regional strike-slip faulting including the following: (1) The San Bernardino Mountain area shows S Hmax direction toward NNW and transpressional stress components likely associated with the motions of the San Andreas Fault and ECSZ; (2) the Cajon Pass and San Gorgonio Pass show transpressional stress regime near the bottom of the seismogenic zone likely associated with the elevated topography; and (3) in Crafton Hills, rotation of the principal stress plunges and SHmax direction and transtensional stress regime below ~10 km, along with lower estimated apparent friction coefficient, suggest a weak fault possibly associated with deep creep. The performed multiscale analysis resolves effects of regional and local loadings. The average stress parameters in the analyzed 37 years do not show significant temporal variations of stress field near the SCTR region.

58 GEOSCIENCES↗

Exploring the Potential of Using Carbonyl Sulfide to Track the Urban Biosphere Signal

Abstract Cities are implementing additional urban green as a means to capture CO 2 and become more carbon neutral. However, cities are complex systems where anthropogenic and natural components of the CO 2 budget interact with each other, and the ability to measure the efficacy of such measures is still not properly addressed. There is still a high degree of uncertainty in determining the contribution of the vegetation signal, which furthermore confounds the use of CO 2 mole fraction measurements for inferring anthropogenic emissions of CO 2 . Carbonyl sulfide (OCS) is a tracer of photosynthesis which can aid in constraining the biosphere signal. This study explores the potential of using OCS to track the urban biosphere signal. We used the Sulfur Transport and dEposition Model (STEM) to simulate the OCS concentrations and the Carnegie Ames Stanford Approach ecosystem model to simulate global CO 2 fluxes over the Bay Area of San Francisco during March 2015. Two observation towers provided measurements of OCS and CO 2 : The Sutro tower in San Francisco (upwind from the area of study providing background observations), and a tower located at Sandia National Laboratories in Livermore (downwind of the highly urbanized San Francisco region). Our results show that the STEM model works better under stable marine influence, and that the boundary layer height and entrainment are driving the diurnal changes in OCS and CO 2 at the downwind Sandia site. However, the STEM model needs to better represent the transport and boundary layer variability, and improved estimates of gross primary productivity for characterizing the urban biosphere signal are needed.

54 ENVIRONMENTAL SCIENCES↗

Small-angle scattering interferometry with neutron orbital angular momentum states

Methods to prepare and characterize neutron helical waves carrying orbital angular momentum (OAM) were recently demonstrated at small-angle neutron scattering (SANS) facilities. These methods enable access to the neutron orbital degree of freedom which provides new avenues of exploration in fundamental science experiments as well as in material characterization applications. However, it remains a challenge to recover phase profiles from SANS measurements. We introduce and demonstrate a novel neutron interferometry technique for extracting phase information that is typically lost in SANS measurements. An array of reference beams, with complementary structured phase profiles, are put into a coherent superposition with the array of object beams, thereby manifesting the phase information in the far-field intensity profile. We demonstrate this by resolving petal-structure signatures of helical wave interference for the first time: an implementation of the long-sought recovery of phase information from small-angle scattering measurements.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Advanced characterization of surface-modified nanoparticles and nanofilled antibacterial dental adhesive resins

Nanotechnology can improve the performance of dental polymers. The objective of this study was to modify the surfaces of nanoparticles with silanes and proteins, characterize nanoparticles’ agglomeration levels and interfaces between nanoparticles and the polymeric matrix. Undoped (n-TiO 2 ), nitrogen-doped (N_TiO 2 ) and nitrogen-fluorine co-doped titanium dioxide nanoparticles (NF_TiO 2 ) were synthesized and subjected to surface modification procedures in preparation for Small-Angle X-Ray Scattering (SAXS) and Small-Angle Neutron Scattering (SANS) characterizations. Experimental adhesives were manually synthesized by incorporating 20% (v/v) of n-TiO 2 , N_TiO 2 or NF_TiO 2 (as-synthesized or surface-modified) into OptiBond Solo Plus (OPTB). Specimens (n = 15/group; d = 6.0 mm, t = 0.5 mm) of OPTB and experimental adhesives were characterized using Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS), 2-D ToF-SIMS chemical imaging and SANS. SAXS results indicated that surface-modified nanoparticles displayed higher scattering intensities in a particle-size dependent manner. ToF-SIMS results demonstrated that nanoparticles’ incorporation did not adversely impact the parental polymer. 2-D ToF-SIMS chemical imaging demonstrated the distribution of Ti + and confirmed nitrogen-doping levels. SANS results confirmed nanoparticles’ functionalization and revealed the interfaces between nanoparticles and the polymer matrix. Metaloxide nanoparticles were successfully fabricated, incorporated and covalently functionalized in a commercial dental adhesive resin, thereby supporting the utilization of nanotechnology in dentistry.

60 APPLIED LIFE SCIENCES↗

The effect of low temperature on poly(3-methyl- N -vinylcaprolactam)- b -poly( N -vinylpyrrolidone) diblock copolymer nanovesicles assembled from all-aqueous media

Nanosized polymeric vesicles (polymersomes) self-assembled from double hydrophilic copolymers of poly(3-methyl-N-vinylcaprolactam) n -b-poly(N-vinylpyrrolidone) m (PMVC n -b-PVPON m ) using all aqueous media are a promising platform for biomedical applications, because of their superior stability over liposomes in vivo and high loading capacity. Herein, we explored the temperature-sensitive behavior of PMVC 58 -b-PVPON 65 vesicles using transmission electron microscopy (TEM), dynamic light scattering (DLS), atomic force microscopy (AFM), and small-angle neutron scattering (SANS) in response to lowering the solution temperature from 37 to 25, 20, 14 and 4 °C. The copolymer vesicles with an average size of 350 nm at 37 °C were assembled from the diblock copolymer dissolved in aqueous solution at 4 °C. We show that while the polymersome's size gradually decreases upon the temperature decrease from 37 to 4 °C, the average shell thickness increases from 17 nm to 25 nm, respectively. SANS study revealed that the PMVC 58 -b-PVPON 65 vesicle undergoes a gradual structure evolution from a dense-shell vesicle at 37–25 °C to a highly-hydrated shell vesicle at 20–14 °C to molecular chain aggregates at 4 °C. From SANS contrast matching study, this vesicle behavior is found to be driven by the gradual rehydration of PMVC block at 37–14 °C. The shell hydration at 20–14 °C also correlated with the 4.4-fold decrease in the relative fluorescence intensity from vesicle-encapsulated fluorescent dye, indicating ~80% of the dye release within 12 hours after the vesicle exposure to 14 °C. No significant (<5%) dye release was observed for the vesicle solutions at 37–20 °C, indicating excellent cargo retention inside the vesicles. Our study provides new fundamental insights on temperature-sensitive polymer vesicles and demonstrates that the copolymer assembly into polymersomes can be achieved by decreasing a copolymer aqueous solution temperature below 14 °C followed by solution exposure to ≥20 °C. This type of all-aqueous assembly, instead of nanoprecipitation from organic solvents or solvent exchange, can be highly desirable for encapsulating a wide range of biological molecules, including proteins, peptides, and nucleic acids, into stable polymer vesicles without a need for organic solvents for dissolution of the copolymers that are amphiphilic at physiologically relevant temperatures of 20–37 °C.

36 MATERIALS SCIENCE↗

An algebraic convolution formulation for multiple-scattering correction in small-angle neutron scattering

Multiple scattering in small-angle neutron scattering (SANS) redistributes spectral weight and distorts structural interpretation, particularly for thick or strongly scattering samples. We develop a finite-dimensional spectral desmearing framework that corrects multiple scattering without resorting to integral transforms or model-dependent extrapolation. The primary intensity is expanded in an orthonormal basis adapted to the isotropic transverse-momentum measure, under which convolution reduces to a recursive tensor contraction, allowing the Poisson-weighted multiple-scattering series to be evaluated directly in a finite-dimensional basis representation. This formulation yields a stable forward–inverse mapping between apparent and primary spectra. Numerical tests demonstrate convergence under repeated convolution and accurate recovery of the single-scattering intensity. Application to SANS measurements collected at multiple neutron facilities, including the Spallation Neutron Source, the High Flux Isotope Reactor, and the Institut Laue-Langevin, shows the quantitative reconstruction of the underlying primary spectrum across a wide range of transmission conditions, including strongly attenuating samples. Here, the method provides a stable, model-agnostic framework for multiple-scattering correction in SANS and enables consistent structural interpretation across instruments and scattering regimes.

Tung, Chi-Huan [Oak Ridge National Laboratory (ORN↗

Shifts in hydroclimatology of US megaregions in response to climate change

Most of the population and economic growth in the United States occurs in megaregions as the clustered metropolitan areas, whereas climate change may amplify negative impacts on water and natural resources. This study assesses shifts in regional hydroclimatology of fourteen US megaregions in response to climate change over the 21st century. Hydroclimatic projections were simulated using the Variable Infiltration Capacity (VIC) model driven by three downscaled climate models from the Multivariate Adaptive Constructed Analogs (MACA) dataset to cover driest to wettest future conditions in the conterminous United States (CONUS). Shifts in the regional hydroclimatolgy and basin characteristics of US megaregions were represented as a combination of changes in the aridity and evaporative indices using the Budyko framework and Fu's equation. Changes in the climate types of US megaregions were estimated using the Fine Gaussian Support Vector Machine (SVM) method. The results indicate that Los Angeles, San Diego, and San Francisco are more likely to experience less arid conditions with some shifts from Continental to Temperate climate type while the hydroclimatology of Houston may become drier with some shifts from Temperate to Continental climate type. Additionally, water yield is likely to decrease in Seattle. Change in the hydroclimatology of Denver and Phoenix highly depends on the selected climate model. However, the basin characteristics of Phoenix have the highest sensitivity to climate change. Overall, the hydroclimatic conditions of Los Angeles, San Diego, Phoenix, Denver, and Houston have the highest sensitivity to climate change. Understanding of future shifts in hydroclimatology of megaregions can help decision-makers to attenuate negative consequences by implementing appropriate adaptation strategies, particularly in the water-scare megaregions.

54 ENVIRONMENTAL SCIENCES↗

Evolution of short-range magnetic correlations in ferromagnetic Ni-V alloys

Here we experimentally study how the magnetic correlations develop in a binary alloy close to the ferromagnetic quantum critical point with small-angle neutron scattering (SANS). Upon alloying the itinerant ferromagnet nickel with vanadium, the ferromagnetic order is continuously suppressed. The critical temperature T c vanishes when vanadium concentrations reach the critical value of x c =0.116 indicating a quantum critical point separating the ferromagnetic and paramagnetic phases. Earlier magnetization and μ⁢SR data have indicated the presence of magnetic inhomogeneities in Ni 1-x ⁢V x and, in particular, recognize the magnetic clusters close to x c , on the paramagnetic and on the ferromagnetic sides with nontrivial dynamical properties [R. Wang et al., Phys. Rev. Lett. 118, 267202 (2017)]. We present the results of SANS study with full polarization analysis of polycrystalline Ni 1-x⁢ V x samples with x=0.10 and x=0.11 with low critical temperatures T c <50 K. For both Ni-V samples close to x c we find isotropic magnetic short-range correlations on the nanometer scale persisting at low temperatures. They are suppressed gradually in higher magnetic fields. In addition, signatures of long-range ordered magnetic domains are present below T c . The fraction of these magnetic clusters embedded in the ferromagnetic ordered phase grows toward x c and agrees well with the cluster fraction estimate from the magnetization and μ⁢SR data. Our SANS studies provide new insights into the nature of the inhomogeneities in a ferromagnetic alloy close to a quantum critical point.

36 MATERIALS SCIENCE↗

Selected advances in small-angle scattering and applications they serve in manufacturing, energy and climate change

Innovations in small-angle X-ray and neutron scattering (SAXS and SANS) at major X-ray and neutron facilities offer new characterization tools for researching materials phenomena relevant to advanced applications. For SAXS, the new generation of diffraction-limited storage rings, incorporating multi-bend achromat concepts, dramatically decrease electron beam emittance and significantly increase X-ray brilliance over previous third-generation sources. This results in intense X-ray incident beams that are more compact in the horizontal plane, allowing significantly improved spatial resolution, better time resolution, and a new era for coherent-beam SAXS methods such as X-ray photon correlation spectroscopy. Elsewhere, X-ray free-electron laser sources provide extremely bright, fully coherent, X-ray pulses of <100 fs and can support SAXS studies of material processes where entire SAXS data sets are collected in a single pulse train. Meanwhile, SANS at both steady-state reactor and pulsed spallation neutron sources has significantly evolved. Developments in neutron optics and multiple detector carriages now enable data collection in a few minutes for materials characterization over nanometre-to-micrometre scale ranges, opening up real-time studies of multi-scale materials phenomena. SANS at pulsed neutron sources is becoming more integrated with neutron diffraction methods for simultaneous structure characterization of complex materials. In this paper, selected developments are highlighted and some recent state-of-the-art studies discussed, relevant to hard matter applications in advanced manufacturing, energy and climate change.

36 MATERIALS SCIENCE↗

Desmearing two-dimensional small-angle neutron scattering data by central moment expansions

Resolution smearing is a critical challenge in the quantitative analysis of two-dimensional small-angle neutron scattering (SANS) data, particularly in studies of soft-matter flow and deformation using SANS. Here, we present a central moment expansion technique to address smearing in anisotropic scattering spectra, offering a model-free desmearing methodology. By accounting for directional variations in resolution smearing and enhancing computational efficiency, this approach reconstructs desmeared intensity distributions from smeared experimental data. Computational benchmarks using interacting hard-sphere fluids and Gaussian chain models validate the accuracy of the method, while simulated noise analyses confirm its robustness under experimental conditions. Experimental validation using rheological SANS data from shear-induced micellar structures demonstrates the practicality and effectiveness of the proposed algorithm. The desmearing technique provides a powerful tool for advancing the quantitative analysis of anisotropic scattering patterns, enabling precise insights into the interplay between material microstructure and macroscopic flow behavior.

anisotropic scattering spectra↗

Dynamic in vivo monitoring of granum structural changes of Ctenanthe setosa (Roscoe) Eichler during drought stress and subsequent recovery

Investigating the effects of drought stress and subsequent recovery on the structure and function of chloroplasts is essential to understanding how plants adapt to environmental stressors. We investigated Ctenanthe setosa (Roscoe) Eichler, an ornamental plant that can tolerate prolonged drought periods (40 and 49 days of water withdrawal). Conventional biochemical, biophysical, physiological and (ultra)structural methods combined for the first time in a higher plant with in vivo small-angle neutron scattering (SANS) were used to characterize the alterations induced by drought stress and subsequent recovery. Upon drought stress, no significant changes occurred in the chloroplast ultrastructure, chlorophyll content, 77K fluorescence emission spectra and maximal quantum efficiency of PSII (Qy dark), but the actual quantum efficiency of PSII (Qy light) decreased, the amounts of PSI-LHCII complexes and PSII monomers declined, and that of PSII supercomplexes increased. Thickness of the leaf and of the adaxial hypodermis, chloroplast length and granum repeat distance (RD) values decreased upon drought stress, as shown by light microscopy and SANS, respectively. Because of the very slight (nm-range) changes in RD values, the large biological variability (significant differences in RD values among the leaves and studied leaf regions) and the invasive sampling required for this method, transmission electron microscopy (TEM) hardly showed significant differences. On the other side, in situ SANS analyses provided a unique insight in vivo into the fast structural recovery of the granum structure of drought-stressed leaves, which happened already 18 h after re-watering, while functional and biochemical recovery took place on a longer time scale.

59 BASIC BIOLOGICAL SCIENCES↗

Coccidioides undetected in soils from agricultural land and uncorrelated with time or the greater soil fungal community on undeveloped land

Coccidioidomycosis is a typically respiratory fungal disease that, in the United States, occurs primarily in Arizona and California. In California, most coccidioidomycosis cases occur in the San Joaquin Valley, a primarily agricultural region where the disease poses a risk for outdoor workers. We collected 710 soil samples and 265 settled dust samples from nine sites in the San Joaquin Valley and examined how Coccidioides detection varied by month, site, and the presence and abundance of other fungal species. We detected Coccidioides in 89 of 238 (37.4%) rodent burrow soil samples at five undeveloped sites and were unable to detect Coccidioides in any of 472 surface and subsurface soil samples at four agricultural sites. In what is the largest sampling effort undertaken on agricultural land, our results provide no evidence that agricultural soils in the San Joaquin Valley harbor Coccidioides . We found no clear association between Coccidioides and the greater soil fungal community, but we identified 19 fungal indicator species that were significantly associated with Coccidioides detection in burrows. We also did not find a seasonal pattern in Coccidioides detection in the rodent burrow soils we sampled. These findings suggest both the presence of a spore bank and that coccidioidomycosis incidence may be more strongly associated with Coccidioides dispersal than Coccidioides growth. Finally, we were able to detect Coccidioides in only five of our 265 near-surface settled dust samples, one from agricultural land, where Coccidioides was undetected in soils, and four from undeveloped land, where Coccidioides was common in the rodent burrow soils we sampled. Our ability to detect Coccidioides in few settled dust samples indicates that improved methods are likely needed moving forward, though raises questions regarding aerial dispersal in Coccidioides , whose key transmission event likely occurs over short distances in rodent burrows from soil to naïve rodent lungs.

59 BASIC BIOLOGICAL SCIENCES↗

Eight County Permian Basin Residual Oil Zone (ROZ) Database

This document describes the spreadsheet geologic database named ROZ_SanAnd_8.xlsm used in the report, ''An Eight-County Appraisal of the San Andres Residual Oil Zone (ROZ) 'Fairway' of the Permian Basin''. The dataset provides geologic properties for ROZ partitions in San Andres formation in eight counties in the Permian Basin. The geologic data is used to estimate total oil in place in each partition and provides the inputs needed to estimate the oil that can be produced and CO 2 stored from the application of CO 2 EOR to a partition. The database and the appraisal report are available on NETL's website under the Collection Name: Eight-County San Andres ROZ Appraisal.

02 PETROLEUM↗

Small Mammal Trapping Survey for the Lawrence Livermore National Laboratory Site 300 and Corral Hollow Ecological Reserve

ECORP Consulting, Inc. conducted a nocturnal small mammal trapping survey within Lawrence Livermore National Laboratory’s (LLNL) Site 300 and the adjacent California Department of Fish and Wildlife (CDFW) Corral Hollow Ecological Reserve. Both sites are located east of the City of Livermore and southwest of the City of Tracy, Alameda and San Joaquin Counties, California (Figure 1-1). A small mammal trapping survey of the project site was conducted in 2002 in preparation for the 2005 LLNL Site-Wide Environmental Impact Statement (SWEIS; Jones & Stokes 2003). The San Joaquin pocket mouse (Perognathus inornatus) was the only special-status species (federal species of concern) captured on Site 300 during the study (West and Woollett 2003). However, since then P. inornatus was taxonomically split into separate subspecies and the pocket mouse species identified on Site 300 in 2002 is no longer considered a special-status species. The 2002 survey also captured woodrats, but identification of the subspecies was not possible. Further investigation was necessary to determine if the woodrat species on the project site was the federally listed (endangered) riparian (San Joaquin Valley) woodrat (Neotoma macrotis riparia [Formerly described as Neotoma fuscipes riparia]), the common Diablo Range woodrat (N. f. perplexa), or another form.

54 ENVIRONMENTAL SCIENCES↗

More Tools for Visualization and Analysis of Small-Angle Neutron Scattering Data: Descriptions and Examples

With the adoption of drtsans as the data reduction software for the GP-SANS, Bio-SANS and EQ-SANS instruments at ORNL, tools for data visualization and analysis that can be integrated into drtsans scripts are needed to further improve the user experience. New tools that do not need to be incorporated directly into data reduction scripts can also positively impact users during their experiments. In this report, a new set of tools is presented that complements the previous set released. The set includes tools for both fitting data and for visualizing data.

42 ENGINEERING↗