small Paid sick leave for federal contractors: Small Business Administration asks DOL to look at alternatives By www.safetyandhealthmagazine.com Published On :: Tue, 12 Apr 2016 00:00:00 -0400 Washington – The Department of Labor should consider alternatives to its proposal that would require federal contractors to provide paid sick leave to their workers, the Small Business Administration’s Office of Advocacy wrote in an April 6 letter. Full Article
small New: Small Business Guide to MSD Solutions By www.safetyandhealthmagazine.com Published On :: Thu, 20 Oct 2022 00:00:00 -0400 Itasca, IL — A recently published guide from the National Safety Council is intended to help small businesses reduce the risk of work-related musculoskeletal disorders. Full Article
small NIOSH 3D printing guide aimed at small businesses By www.safetyandhealthmagazine.com Published On :: Wed, 31 Jan 2024 00:00:00 -0500 Washington — Employers whose workers use 3D printers in non-industrial settings can take steps to limit employee exposure to emissions from heated filaments, polymers and powders, NIOSH says. Full Article
small Two emergency medical techs is too many for small coal mines, Kentucky lawmaker says By www.safetyandhealthmagazine.com Published On :: Mon, 18 Mar 2024 00:00:00 -0400 Frankfort, KY — A bill that would reduce – to one from two – the number of mine emergency technicians required during each shift at small underground coal mines is advancing in the Kentucky Legislature. Full Article
small Small Town Cultures Raw Fermented Foods By www.preparedfoods.com Published On :: Wed, 08 Dec 2021 12:00:00 -0500 Small Town Cultures raw fermented foods include sliced jalapeños, cardamon beets, turmeric kimchi, spicy radish, Meyer lemon, and more to support nutrition. Full Article
small Changes big and small create challenges for food and beverage manufacturers By www.foodengineeringmag.com Published On :: Mon, 13 Jan 2020 09:00:00 -0500 After the mad dash to end one year, January seems like a chance to get your feet back under you as you start the next. Full Article
small Laminator Offers Smaller Footprint, Flexibility, Easier Sanitation and Maintenance By www.foodengineeringmag.com Published On :: Mon, 30 Sep 2024 10:32:24 -0400 With precise, automatic and synchronized control of dough sheet length, conveyor speed and number of laminations, the operator has an efficient and effective process, resulting in consistent, high-quality product. Full Article
small Big and Small Brewers Launch Automation Upgrades By www.foodengineeringmag.com Published On :: Fri, 05 Jul 2024 23:00:00 -0400 Regional craft breweries and independents are investing in automation and plant upgrades to increase production, improve maintenance and move toward bigger volumes. Full Article
small 'Small steps and small wins' in young people's everyday climate crisis activism. By ezproxy.scu.edu.au Published On :: Tue, 01 Jun 2021 00:00:00 -0400 Children's Geographies; 06/01/2021(AN 151284203); ISSN: 14733285Academic Search Premier Full Article ACTIVISM CRISES PSYCHOLOGICAL adaptation COMMUNITIES SOCIAL change
small Identity and life quality: shaping one's place on a small island in a fishing community. By ezproxy.scu.edu.au Published On :: Wed, 01 Feb 2023 00:00:00 -0500 Children's Geographies; 02/01/2023(AN 163249017); ISSN: 14733285Academic Search Premier Full Article NORWAY QUALITY of life FISHING villages FISH communities ISLANDS SUSTAINABILITY COMMUNITIES SOCIAL context
small Changes in children's rhythms of everyday life during the COVID-19 pandemic in a small town in the Prague metropolitan area. By ezproxy.scu.edu.au Published On :: Thu, 01 Feb 2024 00:00:00 -0500 Children's Geographies; 02/01/2024(AN 175911757); ISSN: 14733285Academic Search Premier Full Article PRAGUE (Czech Republic) COVID-19 pandemic SMALL cities METROPOLITAN areas EVERYDAY life RHYTHM ONLINE education
small Exploring the opportunities and constraints of urban small green spaces: an investigation of affordances. By ezproxy.scu.edu.au Published On :: Mon, 01 Apr 2024 00:00:00 -0400 Children's Geographies; 04/01/2024(AN 178088140); ISSN: 14733285Academic Search Premier Full Article TEHRAN (Iran) PUBLIC spaces PHYSICAL activity SOCIALIZATION COGNITIVE development WELL-being CITIES & towns
small Africa Small Grants programme: Palliative Care Development in Africa (Due by 31 Oct) By ifp.nyu.edu Published On :: Tue, 15 Oct 2024 03:52:38 +0000 The post Africa Small Grants programme: Palliative Care Development in Africa (Due by 31 Oct) was curated by information for practice. Full Article Funding
small Viefe’s Hardware Collections Are Small in Size + Big in Personality By design-milk.com Published On :: Tue, 05 Nov 2024 16:00:37 +0000 From foundry-inspired knobs to playful wall hooks, Viefe's new hardware makes it easy to add the finishing touches to a space. Full Article Home Furnishings Main Alexis Vivet cabinet hardware door hardware door stopper handles hardware kaschkasch knob knobs Viefe wall hook wall hooks
small Fuel Economy Standards Are Supersizing Our Vehicles. Ford Scrapping Small Cars Is An Alarm Bell. By www.forbes.com Published On :: Tue, 15 May 2018 13:28 -0500 Asst. Prof. Koichiro Ito explains research on regulations increasing average size of vehicles Full Article
small Fuel Economy Standards Are Supersizing Our Vehicles. Ford Scrapping Small Cars Is An Alarm Bell. By www.forbes.com Published On :: Wed, 16 May 2018 15:24 -0500 Asst. Prof. Koichiro Ito explains research on regulations increasing average size of vehicles Full Article
small Human Challenges His Cat to Jump Into a High Cabinet With Increasingly Smaller Openings By laughingsquid.com Published On :: Fri, 08 Nov 2024 18:35:03 +0000 The human belonging to a cat named Ruka, set up a jump challenge for his feline, who loves to sleep in a high cabinet in their apartment. Full Article Blog
small Veterans face challenges starting small businesses but there are plenty of resources to help By www.mprnews.org Published On :: Mon, 11 Nov 2024 19:45:00 +0000 Many veterans who’ve started small businesses tell a similar story: Their military service prepared them mentally for the task, but they were at a disadvantage when it came to the financial part. Full Article
small Zoning To Oppose Casella Landfill Plan Divides Small North Country Town By www.nhpr.org Published On :: Mon, 05 Aug 2019 17:24:24 +0000 The solid waste company Casella says it's running out of space for Northern New England's trash. So it's taking the rare step of planning a brand-new landfill, in the small Coös County town of Dalton. Lots of locals agree – they don't want the landfill. But they're divided on one potential tool to block it: zoning. Full Article
small The Teller of Small Fortunes by Leong, Julie By catalog.wiltonlibrary.org Published On :: Wed, 13 Nov 2024 00:04:28 -0500 A wandering fortune teller finds an unexpected family in this warm and wonderful debut fantasy, perfect for readers of Travis Baldree and Sangu Mandanna. Tao is an immigrant fortune teller, traveling between villages with just her trusty mule for company. She only tells "small" fortunes: whether it will hail next week; which boy the barmaid will kiss; when the cow will calve. She knows from bitter experience that big fortunes come with big consequences… Even if it’s a lonely life, it’s better th Full Article New Books
small 43% of data breaches target small businesses in 5 industries By www.retailtechnologyreview.com Published On :: Some industries are more vulnerable to cyber threats hence facing a high risk of experiencing data breaches or other types of cyber attacks in the future. Full Article Surveillance and Security Critical Issues
small How small businesses go from brick to virtual By english.pravda.ru Published On :: Tue, 02 Nov 2021 15:51:00 +0300 It's difficult to highlight any positives of the recent pandemic. However, if one exists in the business world, it's the virtual infrastructure that was built on the fly to allow companies to make the shift away from traditional brick and mortar operations. If you've been on the fence about a permanent shift in the virtual direction, this is your time to shine. The benefits of going virtual Full Article Business
small Small earthquake detected on Shropshire-Staffordshire border - BBC.com By news.google.com Published On :: Fri, 19 Apr 2024 07:00:00 GMT Small earthquake detected on Shropshire-Staffordshire border BBC.com Full Article
small Small earthquake recorded under Powys town - Powys County Times By news.google.com Published On :: Sun, 29 Sep 2024 07:00:00 GMT Small earthquake recorded under Powys town Powys County Times Full Article
small Automated selection of nanoparticle models for small-angle X-ray scattering data analysis using machine learning By journals.iucr.org Published On :: 2024-02-29 Small-angle X-ray scattering (SAXS) is widely used to analyze the shape and size of nanoparticles in solution. A multitude of models, describing the SAXS intensity resulting from nanoparticles of various shapes, have been developed by the scientific community and are used for data analysis. Choosing the optimal model is a crucial step in data analysis, which can be difficult and time-consuming, especially for non-expert users. An algorithm is proposed, based on machine learning, representation learning and SAXS-specific preprocessing methods, which instantly selects the nanoparticle model best suited to describe SAXS data. The different algorithms compared are trained and evaluated on a simulated database. This database includes 75 000 scattering spectra from nine nanoparticle models, and realistically simulates two distinct device configurations. It will be made freely available to serve as a basis of comparison for future work. Deploying a universal solution for automatic nanoparticle model selection is a challenge made more difficult by the diversity of SAXS instruments and their flexible settings. The poor transferability of classification rules learned on one device configuration to another is highlighted. It is shown that training on several device configurations enables the algorithm to be generalized, without degrading performance compared with configuration-specific training. Finally, the classification algorithm is evaluated on a real data set obtained by performing SAXS experiments on nanoparticles for each of the instrumental configurations, which have been characterized by transmission electron microscopy. This data set, although very limited, allows estimation of the transferability of the classification rules learned on simulated data to real data. Full Article text
small The smearing function for a multi-slit very small angle neutron scattering instrument By journals.iucr.org Published On :: This study validates the feasibility of applying a smearing method for the multi-slit very small angle neutron scattering instrument (MS-VSANS) at the China Spallation Neutron Source. Through analysis limited to a vertical range of 8 mm, the study demonstrates consistency between the predicted smearing function and experimental data, marking a significant milestone in utilizing real data from such instruments. Full Article text
small Grazing-incidence small-angle neutron scattering at high pressure (HP-GISANS): a soft matter feasibility study on grafted brush films By journals.iucr.org Published On :: We present a demonstration of high-pressure grazing-incidence small-angle neutron scattering for soft matter thin films. The results suggest changes in water reorganization at different pressures. Full Article text
small Improving the reliability of small- and wide-angle X-ray scattering measurements of anisotropic precipitates in metallic alloys using sample rotation By journals.iucr.org Published On :: Rotations of small- and wide-angle X-ray scattering samples during acquisition are shown to give a drastic improvement in the reliability of the characterization of anisotropic precipitates in metallic alloys. Full Article text
small Small-angle scattering and dark-field imaging for validation of a new neutron far-field interferometer By journals.iucr.org Published On :: A neutron far-field interferometer is under development at NIST with the aim of enabling a multi-scale measurement combining the best of small-angle neutron scattering (SANS) and neutron imaging and tomography. We use the close relationship between SANS, ultra-SANS, spin-echo SANS and dark-field imaging and measurements of monodisperse spheres as a validation metric, highlighting the strengths and weaknesses of each of these neutron techniques. Full Article text
small Grazing-incidence small-angle neutron scattering at high pressure (HP-GISANS): a soft matter feasibility study on grafted brush films By journals.iucr.org Published On :: 2024-11-04 Grazing-incidence small-angle neutron scattering (GISANS) under pressure (HP-GISANS) at the solid (Si)–liquid (D2O) interface is demonstrated for the pressure-induced lateral morphological characterization of the nanostructure in thin (<100 nm) soft matter films. We demonstrate feasibility by investigating a hydrophobic {poly[(2,2,3,3,4,4,5,5-octafluoro)pentyl methacrylate]} (POFPMA)–hydrophilic {poly[2-(dimethylamino)ethyl methacrylate]} (PDMAEMA) brush mixture of strong incompatibility between the homopolymers, anchored on Si, at T = 45°C for two pressures, P = 1 bar and P = 800 bar. Our GISANS results reveal nanostructural rearrangements with increasing P, underlining P-induced effects in tethered polymer brush layers swollen with bulk solvent. Full Article text
small Small-angle scattering and dark-field imaging for validation of a new neutron far-field interferometer By journals.iucr.org Published On :: 2024-11-08 The continued advancement of complex materials often requires a deeper understanding of the structure–function relationship across many length scales, which quickly becomes an arduous task when multiple measurements are required to characterize hierarchical and inherently heterogeneous materials. Therefore, there are benefits in the simultaneous characterization of multiple length scales. At the National Institute of Standards and Technology, a new neutron far-field interferometer is under development that aims to enable a multi-scale measurement combining the best of small-angle neutron scattering (SANS) and neutron imaging and tomography. Spatially resolved structural information on the same length scales as SANS (0.001–1 µm) and ultra-small-angle neutron scattering (USANS, 0.1–10 µm) will be collected via dark-field imaging simultaneously with regular attenuation radiography (>10 µm). The dark field is analogous to the polarization loss measured in spin-echo SANS (SESANS) and is related to isotropic SANS through a Hankel transform. Therefore, we use this close relationship and analyze results from SANS, USANS, SESANS and dark-field imaging of monodisperse spheres as a validation metric for the interferometry measurements. The results also highlight the strengths and weaknesses of these neutron techniques for both steady-state and pulsed neutron sources. Finally, we present an example of the value added by the spatial resolution enabled by dark-field imaging in the study of more complex heterogeneous materials. This information would otherwise be lost in other small-angle scattering measurements averaged over the sample. Full Article text
small Improving the reliability of small- and wide-angle X-ray scattering measurements of anisotropic precipitates in metallic alloys using sample rotation By journals.iucr.org Published On :: 2024-11-04 Nanometric precipitates in metallic alloys often have highly anisotropic shapes. Given the large grain size and non-random texture typical of these alloys, performing small- and wide-angle X-ray scattering (SAXS/WAXS) measurements on such samples for determining their characteristics (typically size and volume fraction) results in highly anisotropic and irreproducible data. Rotations of flat samples during SAXS/WAXS acquisitions are presented here as a solution to these anisotropy issues. Two aluminium alloys containing anisotropic precipitates are used as examples to validate the approach with a −45°/45° angular range. Clear improvements can be seen on the SAXS I(q) fitting and the consistency between the different SAXS/WAXS measurements. This methodology results in more reliable measurements of the precipitate's characteristics, and thus allows for time- and space-resolved measurements with higher accuracy. Full Article text
small The smearing function for a multi-slit very small angle neutron scattering instrument By journals.iucr.org Published On :: 2024-10-29 Besides traditional pinhole geometry, the multi-slit very small angle neutron scattering instrument (MS-VSANS) at the China Spallation Neutron Source also utilizes a multi-slit collimation system to focus neutrons. Using the special focusing structures, the minimum scattering vector magnitude (q) can reach 0.00028 Å−1. The special structures also lead to a significantly different smearing function. By comparing the results of theoretical calculations with experimental data, we have validated the feasibility of a smearing method based on a mature theory for slit smearing. We use the weight-averaged intensity of neutron wavelength as a representative to evaluate the effect from a broad wavelength distribution, concentrating on the effect from the geometry of the multi-slit structures and the detector. The consistency of the theoretical calculation of the smearing function with experimental VSANS scattering profiles for a series of polystyrene standards of different diameters proves the feasibility of the smearing method. This marks the inaugural use of real experimental data from an instrument employing a multi-slit collimation system. Full Article text
small Influence of device configuration and noise on a machine learning predictor for the selection of nanoparticle small-angle X-ray scattering models By journals.iucr.org Published On :: 2024-09-23 Small-angle X-ray scattering (SAXS) is a widely used method for nanoparticle characterization. A common approach to analysing nanoparticles in solution by SAXS involves fitting the curve using a parametric model that relates real-space parameters, such as nanoparticle size and electron density, to intensity values in reciprocal space. Selecting the optimal model is a crucial step in terms of analysis quality and can be time-consuming and complex. Several studies have proposed effective methods, based on machine learning, to automate the model selection step. Deploying these methods in software intended for both researchers and industry raises several issues. The diversity of SAXS instrumentation requires assessment of the robustness of these methods on data from various machine configurations, involving significant variations in the q-space ranges and highly variable signal-to-noise ratios (SNR) from one data set to another. In the case of laboratory instrumentation, data acquisition can be time-consuming and there is no universal criterion for defining an optimal acquisition time. This paper presents an approach that revisits the nanoparticle model selection method proposed by Monge et al. [Acta Cryst. (2024), A80, 202–212], evaluating and enhancing its robustness on data from device configurations not seen during training, by expanding the data set used for training. The influence of SNR on predictor robustness is then assessed, improved, and used to propose a stopping criterion for optimizing the trade-off between exposure time and data quality. Full Article text
small Developing an in situ LED irradiation system for small-angle X-ray scattering at B21, Diamond Light Source By journals.iucr.org Published On :: 2024-05-31 Beamline B21 at the Diamond Light Source synchrotron in the UK is a small-angle X-ray scattering (SAXS) beamline that specializes in high-throughput measurements via automated sample delivery systems. A system has been developed whereby a sample can be illuminated by a focused beam of light coincident with the X-ray beam. The system is compatible with the highly automated sample delivery system at the beamline and allows a beamline user to select a light source from a broad range of wavelengths across the UV and visible spectrum and to control the timing and duration of the light pulse with respect to the X-ray exposure of the SAXS measurement. The intensity of the light source has been characterized across the wavelength range enabling experiments where a quantitative measure of dose is important. Finally, the utility of the system is demonstrated via measurement of several light-responsive samples. Full Article text
small In situ photodeposition of ultra-small palladium particles on TiO2 By journals.iucr.org Published On :: 2024-07-15 In situ and operando investigation of photocatalysts plays a fundamental role in understanding the processes of active phase formation and the mechanisms of catalytic reactions, which is crucial for the rational design of more efficient materials. Using a custom-made operando photocatalytic cell, an in situ procedure to follow the formation steps of Pd/TiO2 photocatalyst by synchrotron-based X-ray absorption spectroscopy (XAS) is proposed. The procedure resulted in the formation of ∼1 nm Pd particles with a much narrower size distribution and homogeneous spreading over TiO2 support compared with the samples generated in a conventional batch reactor. The combination of in situ XAS spectroscopy with high-angle annular dark-field scanning transmission electron microscopy demonstrated the formation of single-atom Pd(0) sites on TiO2 as the initial step of the photodeposition process. Palladium hydride particles were observed for all investigated samples upon exposure to formic acid solutions. Full Article text
small A 1D imaging soft X-ray spectrometer for the small quantum systems instrument at the European XFEL By journals.iucr.org Published On :: 2024-07-30 A 1D imaging soft X-ray spectrometer installed on the small quantum systems (SQS) scientific instrument of the European XFEL is described. It uses movable cylindrical constant-line-spacing gratings in the Rowland configuration for energy dispersion in the vertical plane, and Wolter optics for simultaneous 1D imaging of the source in the horizontal plane. The soft X-ray fluorescence spectro-imaging capability will be exploited in pump–probe measurements and in investigations of propagation effects and other nonlinear phenomena. Full Article text
small Investigating the missing-wedge problem in small-angle X-ray scattering tensor tomography across real and reciprocal space By journals.iucr.org Published On :: 2024-08-28 Small-angle-scattering tensor tomography is a technique for studying anisotropic nanostructures of millimetre-sized samples in a volume-resolved manner. It requires the acquisition of data through repeated tomographic rotations about an axis which is subjected to a series of tilts. The tilt that can be achieved with a typical setup is geometrically constrained, which leads to limits in the set of directions from which the different parts of the reciprocal space map can be probed. Here, we characterize the impact of this limitation on reconstructions in terms of the missing wedge problem of tomography, by treating the problem of tensor tomography as the reconstruction of a three-dimensional field of functions on the unit sphere, represented by a grid of Gaussian radial basis functions. We then devise an acquisition scheme to obtain complete data by remounting the sample, which we apply to a sample of human trabecular bone. Performing tensor tomographic reconstructions of limited data sets as well as the complete data set, we further investigate and validate the missing wedge problem by investigating reconstruction errors due to data incompleteness across both real and reciprocal space. Finally, we carry out an analysis of orientations and derived scalar quantities, to quantify the impact of this missing wedge problem on a typical tensor tomographic analysis. We conclude that the effects of data incompleteness are consistent with the predicted impact of the missing wedge problem, and that the impact on tensor tomographic analysis is appreciable but limited, especially if precautions are taken. In particular, there is only limited impact on the means and relative anisotropies of the reconstructed reciprocal space maps. Full Article text
small A new dual-thickness semi-transparent beamstop for small-angle X-ray scattering By journals.iucr.org Published On :: 2024-08-25 An innovative dual-thickness semi-transparent beamstop designed to enhance the performance of small-angle X-ray scattering (SAXS) experiments is introduced. This design integrates two absorbers of differing thicknesses side by side into a single attenuator, known as a beamstop. Instead of completely stopping the direct beam, it attenuates it, allowing the SAXS detector to measure the transmitted beam through the sample. This approach achieves true synchronization in measuring both scattered and transmitted signals and effectively eliminates higher-order harmonic contributions when determining the transmission light intensity through the sample. This facilitates and optimizes signal detection and background subtraction. This contribution details the theoretical basis and practical implementation of this solution at the SAXS station on the 1W2A beamline at the Beijing Synchrotron Radiation Facility. It also anticipates its application at other SAXS stations, including that at the forthcoming High Energy Photon Source, providing an effective solution for high-precision SAXS experiments. Full Article text
small A small step towards an important goal: fragment screen of the c-di-AMP-synthesizing enzyme CdaA By journals.iucr.org Published On :: 2024-04-29 CdaA is the most widespread diadenylate cyclase in many bacterial species, including several multidrug-resistant human pathogens. The enzymatic product of CdaA, cyclic di-AMP, is a secondary messenger that is essential for the viability of many bacteria. Its absence in humans makes CdaA a very promising and attractive target for the development of new antibiotics. Here, the structural results are presented of a crystallographic fragment screen against CdaA from Listeria monocytogenes, a saprophytic Gram-positive bacterium and an opportunistic food-borne pathogen that can cause listeriosis in humans and animals. Two of the eight fragment molecules reported here were localized in the highly conserved ATP-binding site. These fragments could serve as potential starting points for the development of antibiotics against several CdaA-dependent bacterial species. Full Article text
small Validation of electron-microscopy maps using solution small-angle X-ray scattering By journals.iucr.org Published On :: 2024-06-27 The determination of the atomic resolution structure of biomacromolecules is essential for understanding details of their function. Traditionally, such a structure determination has been performed with crystallographic or nuclear resonance methods, but during the last decade, cryogenic transmission electron microscopy (cryo-TEM) has become an equally important tool. As the blotting and flash-freezing of the samples can induce conformational changes, external validation tools are required to ensure that the vitrified samples are representative of the solution. Although many validation tools have already been developed, most of them rely on fully resolved atomic models, which prevents early screening of the cryo-TEM maps. Here, a novel and automated method for performing such a validation utilizing small-angle X-ray scattering measurements, publicly available through the new software package AUSAXS, is introduced and implemented. The method has been tested on both simulated and experimental data, where it was shown to work remarkably well as a validation tool. The method provides a dummy atomic model derived from the EM map which best represents the solution structure. Full Article text
small Benchmarking predictive methods for small-angle X-ray scattering from atomic coordinates of proteins using maximum likelihood consensus data By journals.iucr.org Published On :: 2024-07-10 Stimulated by informal conversations at the XVII International Small Angle Scattering (SAS) conference (Traverse City, 2017), an international team of experts undertook a round-robin exercise to produce a large dataset from proteins under standard solution conditions. These data were used to generate consensus SAS profiles for xylose isomerase, urate oxidase, xylanase, lysozyme and ribonuclease A. Here, we apply a new protocol using maximum likelihood with a larger number of the contributed datasets to generate improved consensus profiles. We investigate the fits of these profiles to predicted profiles from atomic coordinates that incorporate different models to account for the contribution to the scattering of water molecules of hydration surrounding proteins in solution. Programs using an implicit, shell-type hydration layer generally optimize fits to experimental data with the aid of two parameters that adjust the volume of the bulk solvent excluded by the protein and the contrast of the hydration layer. For these models, we found the error-weighted residual differences between the model and the experiment generally reflected the subsidiary maxima and minima in the consensus profiles that are determined by the size of the protein plus the hydration layer. By comparison, all-atom solute and solvent molecular dynamics (MD) simulations are without the benefit of adjustable parameters and, nonetheless, they yielded at least equally good fits with residual differences that are less reflective of the structure in the consensus profile. Further, where MD simulations accounted for the precise solvent composition of the experiment, specifically the inclusion of ions, the modelled radius of gyration values were significantly closer to the experiment. The power of adjustable parameters to mask real differences between a model and the structure present in solution is demonstrated by the results for the conformationally dynamic ribonuclease A and calculations with pseudo-experimental data. This study shows that, while methods invoking an implicit hydration layer have the unequivocal advantage of speed, care is needed to understand the influence of the adjustable parameters. All-atom solute and solvent MD simulations are slower but are less susceptible to false positives, and can account for thermal fluctuations in atomic positions, and more accurately represent the water molecules of hydration that contribute to the scattering profile. Full Article text
small Bridging length scales in hard materials with ultra-small angle X-ray scattering – a critical review By journals.iucr.org Published On :: 2024-08-01 Owing to their exceptional properties, hard materials such as advanced ceramics, metals and composites have enormous economic and societal value, with applications across numerous industries. Understanding their microstructural characteristics is crucial for enhancing their performance, materials development and unleashing their potential for future innovative applications. However, their microstructures are unambiguously hierarchical and typically span several length scales, from sub-ångstrom to micrometres, posing demanding challenges for their characterization, especially for in situ characterization which is critical to understanding the kinetic processes controlling microstructure formation. This review provides a comprehensive description of the rapidly developing technique of ultra-small angle X-ray scattering (USAXS), a nondestructive method for probing the nano-to-micrometre scale features of hard materials. USAXS and its complementary techniques, when developed for and applied to hard materials, offer valuable insights into their porosity, grain size, phase composition and inhomogeneities. We discuss the fundamental principles, instrumentation, advantages, challenges and global status of USAXS for hard materials. Using selected examples, we demonstrate the potential of this technique for unveiling the microstructural characteristics of hard materials and its relevance to advanced materials development and manufacturing process optimization. We also provide our perspective on the opportunities and challenges for the continued development of USAXS, including multimodal characterization, coherent scattering, time-resolved studies, machine learning and autonomous experiments. Our goal is to stimulate further implementation and exploration of USAXS techniques and inspire their broader adoption across various domains of hard materials science, thereby driving the field toward discoveries and further developments. Full Article text
small BioXTAS RAW 2: new developments for a free open-source program for small-angle scattering data reduction and analysis By journals.iucr.org Published On :: 2024-02-01 BioXTAS RAW is a free open-source program for reduction, analysis and modelling of biological small-angle scattering data. Here, the new developments in RAW version 2 are described. These include improved data reduction using pyFAI; updated automated Guinier fitting and Dmax finding algorithms; automated series (e.g. size-exclusion chromatography coupled small-angle X-ray scattering or SEC-SAXS) buffer- and sample-region finding algorithms; linear and integral baseline correction for series; deconvolution of series data using regularized alternating least squares (REGALS); creation of electron-density reconstructions using electron density via solution scattering (DENSS); a comparison window showing residuals, ratios and statistical comparisons between profiles; and generation of PDF reports with summary plots and tables for all analysis. Furthermore, there is now a RAW API, which can be used without the graphical user interface (GUI), providing full access to all of the functionality found in the GUI. In addition to these new capabilities, RAW has undergone significant technical updates, such as adding Python 3 compatibility, and has entirely new documentation available both online and in the program. Full Article text
small The multi-slit very small angle neutron scattering instrument at the China Spallation Neutron Source By journals.iucr.org Published On :: 2024-03-21 A multi-slit very small angle neutron scattering (MS-VSANS) instrument has been finally accepted at the China Spallation Neutron Source (CSNS). It is the first spallation neutron source based VSANS instrument. MS-VSANS has a good signal-to-noise ratio and can cover a wide scattering vector magnitude range from 0.00028 to 1.4 Å−1. In its primary flight path, a combined curved multichannel beam bender and sections of rotary exchange drums are installed to minimize the background downstream of the instrument. An exchangeable multi-slit beam focusing system is integrated into the primary flight path, enabling access to a minimum scattering vector magnitude of 0.00028 Å−1. MS-VSANS has three modes, namely conventional SANS, polarizing SANS and VSANS modes. In the SANS mode, three motorized high-efficiency 3He tube detectors inside the detector tank cover scattering angles from 0.12 to 35° simultaneously. In the polarizing SANS mode, a double-V cavity provides highly polarized neutrons and a high-efficiency 3He polarization analyser allows full polarization analysis. In the VSANS mode, an innovative high-resolution gas electron multiplier detector covers scattering angles from 0.016 to 0.447°. The absolute scattering intensities of a selection of standard samples are obtained using the direct-beam technique; the effectiveness of this method is verified by testing the standard samples and comparing the results with those from a benchmark instrument. The MS-VSANS instrument is designed to be flexible and versatile and all the design goals have been achieved. Full Article text
small SEB: a computational tool for symbolic derivation of the small-angle scattering from complex composite structures By journals.iucr.org Published On :: 2024-03-31 Analysis of small-angle scattering (SAS) data requires intensive modeling to infer and characterize the structures present in a sample. This iterative improvement of models is a time-consuming process. Presented here is Scattering Equation Builder (SEB), a C++ library that derives exact analytic expressions for the form factors of complex composite structures. The user writes a small program that specifies how the sub-units should be linked to form a composite structure and calls SEB to obtain an expression for the form factor. SEB supports e.g. Gaussian polymer chains and loops, thin rods and circles, solid spheres, spherical shells and cylinders, and many different options for how these can be linked together. The formalism behind SEB is presented and simple case studies are given, such as block copolymers with different types of linkage, as well as more complex examples, such as a random walk model of 100 linked sub-units, dendrimers, polymers and rods attached to the surfaces of geometric objects, and finally the scattering from a linear chain of five stars, where each star is built up of four diblock copolymers. These examples illustrate how SEB can be used to develop complex models and hence reduce the cost of analyzing SAS data. Full Article text
small A correction procedure for secondary scattering contributions from windows in small-angle X-ray scattering and ultra-small-angle X-ray scattering By journals.iucr.org Published On :: 2024-03-29 This article describes a correction procedure for the removal of indirect background contributions to measured small-angle X-ray scattering patterns. The high scattering power of a sample in the ultra-small-angle region may serve as a secondary source for a window placed in front of the detector. The resulting secondary scattering appears as a sample-dependent background in the measured pattern that cannot be directly subtracted. This is an intricate problem in measurements at ultra-low angles, which can significantly reduce the useful dynamic range of detection. Two different procedures are presented to retrieve the real scattering profile of the sample. Full Article text
small Quantitative selection of sample structures in small-angle scattering using Bayesian methods By journals.iucr.org Published On :: 2024-06-18 Small-angle scattering (SAS) is a key experimental technique for analyzing nanoscale structures in various materials. In SAS data analysis, selecting an appropriate mathematical model for the scattering intensity is critical, as it generates a hypothesis of the structure of the experimental sample. Traditional model selection methods either rely on qualitative approaches or are prone to overfitting. This paper introduces an analytical method that applies Bayesian model selection to SAS measurement data, enabling a quantitative evaluation of the validity of mathematical models. The performance of the method is assessed through numerical experiments using artificial data for multicomponent spherical materials, demonstrating that this proposed analysis approach yields highly accurate and interpretable results. The ability of the method to analyze a range of mixing ratios and particle size ratios for mixed components is also discussed, along with its precision in model evaluation by the degree of fitting. The proposed method effectively facilitates quantitative analysis of nanoscale sample structures in SAS, which has traditionally been challenging, and is expected to contribute significantly to advancements in a wide range of fields. Full Article text
small X-ray tensor tomography for small-grained polycrystals with strong texture By journals.iucr.org Published On :: 2024-06-27 Small-angle X-ray tensor tomography and the related wide-angle X-ray tensor tomography are X-ray imaging techniques that tomographically reconstruct the anisotropic scattering density of extended samples. In previous studies, these methods have been used to image samples where the scattering density depends slowly on the direction of scattering, typically modeling the directionality, i.e. the texture, with a spherical harmonics expansion up until order ℓ = 8 or lower. This study investigates the performance of several established algorithms from small-angle X-ray tensor tomography on samples with a faster variation as a function of scattering direction and compares their expected and achieved performance. The various algorithms are tested using wide-angle scattering data from an as-drawn steel wire with known texture to establish the viability of the tensor tomography approach for such samples and to compare the performance of existing algorithms. Full Article text
small Coordinate-based simulation of pair distance distribution functions for small and large molecular assemblies: implementation and applications By journals.iucr.org Published On :: 2024-09-17 X-ray scattering has become a major tool in the structural characterization of nanoscale materials. Thanks to the widely available experimental and computational atomic models, coordinate-based X-ray scattering simulation has played a crucial role in data interpretation in the past two decades. However, simulation of real-space pair distance distribution functions (PDDFs) from small- and wide-angle X-ray scattering, SAXS/WAXS, has been relatively less exploited. This study presents a comparison of PDDF simulation methods, which are applied to molecular structures that range in size from β-cyclodextrin [1 kDa molecular weight (MW), 66 non-hydrogen atoms] to the satellite tobacco mosaic virus capsid (1.1 MDa MW, 81 960 non-hydrogen atoms). The results demonstrate the power of interpretation of experimental SAXS/WAXS from the real-space view, particularly by providing a more intuitive method for understanding of partial structure contributions. Furthermore, the computational efficiency of PDDF simulation algorithms makes them attractive as approaches for the analysis of large nanoscale materials and biological assemblies. The simulation methods demonstrated in this article have been implemented in stand-alone software, SolX 3.0, which is available to download from https://12idb.xray.aps.anl.gov/solx.html. Full Article text