x What Exactly Is Jell-O Made From? By recipes.howstuffworks.com Published On :: Fri, 29 Mar 2024 11:15:12 -0400 "Watch it wiggle, see it jiggle" Remember that jingle? We're talking about Jell-O, or gelatin. But just how does how does it do that? And what is this stuff made of? Full Article
x Is Your Shower Head Leaking? Try These Easy Fixes By home.howstuffworks.com Published On :: Mon, 22 Jan 2024 17:22:14 -0500 Shower head leaking? That's definitely annoying but not the end of the world. Shower heads are subject to several problems when it comes to leaks. Learn how to address a dripping shower head. Full Article
x Washing Symbols Explained: A Guide to Garment Care Labels By home.howstuffworks.com Published On :: Mon, 22 Jan 2024 17:38:15 -0500 The labels on your clothes have all types of laundry symbols on them. Here's what all those symbols mean. Full Article
x Sunmi to release new single next month By world.kbs.co.kr Published On :: 2024-05-06 Sunmi is set to drop a new single in June. The new single has been written by the singer herself, and she recently finished shooting the music video in Croatia.The upcoming single comes around eight months after...[more...] Full Article
x EXO's Suho to release new solo album By world.kbs.co.kr Published On :: 2024-05-06 EXO’s Suho will release a new solo album this month. The new EP, titled “1 to 3” will drop on May 31, more than two years after his second solo album “Grey Suit” was released in April...[more...] Full Article
x Omega X to Release New Japanese EP By world.kbs.co.kr Published On :: 2024-10-08 +09:00 Omega X will release its 2nd Japanese EP next month. The new album is called “To.” and it will be released on Nov. 13. The group’s last Japanese album was its debut EP,...[more...] Full Article Economy&It
x [4K] SEVENTEEN, CNBLUE, AB6IX, Billlie, SAY MY NAME, YENA, EPEX, VANNER, Xdinary Heroes, JD1 | On the way to music bank 241018 By world.kbs.co.kr Published On :: 2024-10-18 +09:00 On the morning of October 18, at Yeoido KBS HallKBS WORLD Radio filmed K-pop stars making their way to attend rehearsals for Music Bank.[more...] Full Article Economy&It
x H1-Key to Launch First Fan Concert Next Month By world.kbs.co.kr Published On :: 2024-10-22 +09:00 H1-Key is set to embark on its first fan concert tour next month. The group will kick off the tour called “Find My KEY” in Hong Kong on Nov. 16 and will travel to other regions...[more...] Full Article Economy&It
x Lunchboxes of Love♡ with the Korea Legacy Committee By world.kbs.co.kr Published On :: 2024-10-23 +09:00 Mike Kim, founder of Korea Legacy Committee, brought super good vibes for this week's Good Vibes Only! Mike shared the activities of the nonprofit organization dedicated to combating the national...[more...] Full Article Economy&It
x NVee Meets Xander, the Self-proclaimed "Kkondae" SBN By world.kbs.co.kr Published On :: 2024-11-11 +09:00 Get ready for an unforgettable first encounter! This week on I Feel You, our regular NVee meets special DJ Xander—the ultimate non-kkondae idol sbn! From hilarious icebreakers to shared stories...[more...] Full Article Economy&It
x How to Export Bookmarks From Chrome By computer.howstuffworks.com Published On :: Wed, 29 May 2024 12:43:11 -0400 You love your Chrome browser bookmarks but your computer is on the verge of dying. Is there any way you can save them so they appear on your new computer? Full Article
x WiFi Extender vs. Booster: What's the Best Choice for You? By computer.howstuffworks.com Published On :: Tue, 09 Jul 2024 14:20:49 -0400 Whether you're streaming your favorite shows, participating in virtual meetings or just browsing the internet, the quality of your WiFi network plays a crucial role in your overall online experience. WiFi signal issues can be frustrating — but luckily, there are multiple tools you can use to improve WiFi coverage. Full Article
x Leo and Pisces Compatibility: Why Their Relationship Is Complex but Worth It By entertainment.howstuffworks.com Published On :: Sat, 09 Nov 2024 05:00:05 -0500 Explore Leo and Pisces compatibility, uncovering their strengths, weaknesses, and whether these zodiac signs can make their relationship work. Full Article
x Is Taurus and Virgo Compatibility a Perfect Match? Exploring Their Bond By entertainment.howstuffworks.com Published On :: Sun, 10 Nov 2024 05:00:04 -0500 Discover Taurus and Virgo compatibility in love, relationships, and friendship. Explore how these earth signs align in values, trust, and practical connections. Full Article
x Exploring the Deep Connection of Cancer and Taurus Compatibility By entertainment.howstuffworks.com Published On :: Wed, 13 Nov 2024 05:15:02 -0500 Explore Cancer and Taurus compatibility, where stability meets sensitivity. Learn how these signs create lasting love through trust, loyalty, and mutual understanding. Full Article
x Exports Fall 17.8% for First 10 Days of November By world.kbs.co.kr Published On :: Mon, 11 Nov 2024 10:10:10 +0900 [Economy] : Exports fell more than 17 percent year-on-year in the first ten days of November because there were fewer working days. According to preliminary data from the Korea Customs Service on Monday, the country’s outbound shipments reached 14-point-nine billion U.S. dollars during the cited period, down ...[more...] Full Article Economy
x Sino-US Decoupling Forecast to Intensify, Preference for US Interests to Expand under Trump Gov't By world.kbs.co.kr Published On :: Wed, 13 Nov 2024 17:16:57 +0900 [Economy] : Sino-U.S. decoupling is forecast to intensify and preference for U.S. interests to expand under the incoming Donald Trump administration. This outlook was put forth Wednesday at a seminar hosted by the Korea International Trade Association(KITA). Kyung Hee University Professor Seo Jung-kun pointed to a ...[more...] Full Article Economy
x Gov’t May Expand Scope of E-7 Visa to Address Labor Shortage in Shipbuilding By world.kbs.co.kr Published On :: Wed, 13 Nov 2024 17:25:03 +0900 [Economy] : Prime Minister Han Duck-soo says the government will consult with the justice ministry and consider expanding the scope of the E-7 visa for professional workers, if the shipbuilding industry deems it necessary. Han made the remark during a news conference on Wednesday when asked how the government plans ...[more...] Full Article Economy
x BGS completes first mapping expedition to Ascension Island - British Geological Survey By news.google.com Published On :: Mon, 11 Dec 2023 08:00:00 GMT BGS completes first mapping expedition to Ascension Island British Geological Survey Full Article
x Did you feel the earth move? Mini-earthquake recorded on Shropshire/Staffordshire border - Express & Star By news.google.com Published On :: Mon, 14 Oct 2024 07:00:00 GMT Did you feel the earth move? Mini-earthquake recorded on Shropshire/Staffordshire border Express & Star Full Article
x Extracting formation temperatures from stalagmites - British Geological Survey By news.google.com Published On :: Wed, 14 Aug 2024 07:00:00 GMT Extracting formation temperatures from stalagmites British Geological Survey Full Article
x Laboratory life: my work experience week at BGS - British Geological Survey By news.google.com Published On :: Tue, 20 Aug 2024 07:00:00 GMT Laboratory life: my work experience week at BGS British Geological Survey Full Article
x BGS to help deliver International Centre of Excellence on Sustainable Resource Management - British Geological Survey By news.google.com Published On :: Tue, 27 Feb 2024 16:32:42 GMT BGS to help deliver International Centre of Excellence on Sustainable Resource Management British Geological Survey Full Article
x Responsible extraction in South America’s Lithium Triangle - British Geological Survey By news.google.com Published On :: Fri, 02 Aug 2024 07:00:00 GMT Responsible extraction in South America’s Lithium Triangle British Geological Survey Full Article
x Electromagnetic geophysics in Japan: a conference experience - British Geological Survey By news.google.com Published On :: Wed, 23 Oct 2024 07:00:00 GMT Electromagnetic geophysics in Japan: a conference experience British Geological Survey Full Article
x Forty years and counting: new topsoil data provides most extensive snapshot of environmental pollution effects - British Geological Survey By news.google.com Published On :: Tue, 01 Oct 2024 07:00:00 GMT Forty years and counting: new topsoil data provides most extensive snapshot of environmental pollution effects British Geological Survey Full Article
x 3aH,4H,5H,8H,9H,9aH-Cycloocta[d][1,3]dioxole-2-thione By journals.iucr.org Published On :: The thionocarbonate of trans-cyclooctenediol, C9H12O2S, crystallizes with a 9/1 disorder in the position of the R,R and S,S-enantiomers. As a result of trans-annulation, both rings adopt a twist conformation. Full Article text
x 2-Amino-5-oxo-4-(thiophen-2-yl)-5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile By journals.iucr.org Published On :: In the crystal structure of the title compound, intermolecular N—H⋯N and N—H⋯O hydrogen bonds form a two-dimensional supramolecular network along the ac plane, contributing to the cohesion of the crystal. Full Article text
x Structural insights into 1,4-bis(neopentyloxy)pillar[5]arene and the pyridine host–guest system By journals.iucr.org Published On :: The crystal structure of a neopentyloxypillar[5]arene with two pyridine molecules encapsulated in the macrocyclic cavity is reported. Full Article text
x 2,4-Dichloro-6-{N-[2-(trifluoromethyl)phenyl]carboximidoyl}phenol By journals.iucr.org Published On :: The title compound was synthesized by the condensation between trifluoromethylaniline and dichlorosalicylaldehyde by nucleophilic addition, forming a hemiaminal, followed by a dehydration to generate an imine. The compound crystallizes in an orthorhombic Pbca (Z = 8) space group with a dihedral angle of 44.70 (5)° between the two aromatic rings. In the crystal, the molecules pack together to form a zigzag pattern along the c axis. Full Article text
x Ethyl (2RS,3SR,4RS)-1-ethyl-2-(furan-2-yl)-4-hydroxy-5-oxopyrrolidine-3-carboxylate By journals.iucr.org Published On :: The crystal structure of a pyrrolidine analogue obtained from the stereoselective reduction of the enolic form of 4-hydroxy-2-furyl-pyrrolecarboxylate is described. Full Article text
x Exploiting fourth-generation synchrotron radiation for enzyme and photoreceptor characterization By journals.iucr.org Published On :: (Time-resolved) macromolecular crystallography at the new ESRF-ID29 beamline is described. Full Article text
x Crystal structure of nickel orthovanadate (Ni3V2O8) at 299 (3) K and 1323 (8) K: an X-ray diffraction study By journals.iucr.org Published On :: The structure of Ni3V2O8 was studied using X-ray diffraction at temperatures of 299 and 1323 K. No phase transition at high temperature is observed. The variation in V—O bond length is small as compared with the Ni—O bond due to its high rigidity. Full Article text
x Synthesis and structural study of the partially disordered complex hexagonal phase δ1-MnZn9.7 By journals.iucr.org Published On :: A detailed structural characterization of the δ1-MnZn9.7 phase is presented. Full Article text
x Structures of hexamethyl-[1,1'-biphenyl]-4,4'-diammonium salts By journals.iucr.org Published On :: The structures of nine hexamethyl-[1,1'-biphenyl]-4,4'-diammonium (HMB) salts are described Full Article text
x The incommensurate composite YxOs4B4 (x = 1.161) By journals.iucr.org Published On :: Tetragonal YxOs4B4 (x = 1.161) is an incommensurate composite of columns of Y atoms in a three-dimensional Os4B4 framework. The structure was refined using the superspace approach. Full Article text
x Coordination geometry flexibility driving supramolecular isomerism of Cu/Mo pillared-layer hybrid networks By journals.iucr.org Published On :: The hydrothermal synthesis and structural characterization of four novel 3D pillared-layer metal–organic frameworks are studied, revealing how the malleability of copper coordination geometries drives diverse supramolecular isomerism. The findings provide new insights into designing advanced hybrid materials with tailored properties, emphasizing the significant role of reaction conditions and metal ion flexibility in determining network topologies. Full Article text
x Polymorphism of Pb5(PO4)3OHδ within the LK-99 mixture By journals.iucr.org Published On :: A new orthorhombic crystal Pb5(PO4)3OHδ of space-group symmetry Pnma significantly differs differing from the hexagonal apatite phases of Pb10(PO4)6O and Pb5(PO4)3OH. Full Article text
x Selective Acceleration and Inhibition of Crystal Growth of Glass Carbamazepine by Low-Concentration Poly(ethylene oxide):Effects of Drug Polymorph By journals.iucr.org Published On :: Low-concentration poly(ethylene oxide) exhibit the polymorph-dependent effects on both the surface and bulk crystal growth of carbamazepine polymorphs. These polymorph-dependent effects of PEO were mainly attributed to the polymer enrichment at the interface and different crystal surface-polymer interactions. Full Article text
x The incommensurate composite YxOs4B4 (x = 1.161) By journals.iucr.org Published On :: 2024-10-31 YxOs4B4 (x = 1.161) crystallizes as a tetragonal incommensurate composite of columns of Y atoms extending along [001] in an Os4B4 framework. The structure was refined using the superspace approach. The basic structure of the Y subsystem can be idealized as having I4/mmm symmetry, with a crystallographically unique Y atom located on the 4/mmm position. The actual superspace symmetry is P42/nmc(00σ3)s0s0. The Y atoms feature only subtle positional modulation in the [001] direction. The Os4B4 subsystem [P42/ncm(00σ3)00ss superspace symmetry] is built of columns of edge-sharing Os4 tetrahedra extending along [001] and B2 dumbbells. The Os4 tetrahedra feature pronounced positional modulation with a distinct variation of the Os—Os bond lengths. Modulation of the B2 dumbbells is best described as a rotation about the [001] axis. Full Article text
x Crystal structure of nickel orthovanadate (Ni3V2O8) at 299 (3) K and 1323 (8) K: an X-ray diffraction study By journals.iucr.org Published On :: 2024-10-23 Nickel orthovanadate is a promising material with potential applications in energy storage and photocatalytic devices. The crystal structure of Ni3V2O8 at 299 (3) K and 1323 (8) K was studied using X-ray powder diffraction. The sample was a single-phase orthorhombic kagome-staircase-Ni3(VO4)2-type structure (space group Cmca) at both temperatures. The phase purity and morphology was studied using energy-dispersive X-ray spectroscopy and scanning electron microscopy. The refined unit-cell parameters at 299 (3) K are a = 5.93384 (4) Å, b = 11.38318 (7) Å and c = 8.23818 (5) Å, and at 1323 (8) K are a = 6.02077 (7) Å, b = 11.48838 (7) Å and c = 8.32611 (9) Å. The obtained results indicate thermal expansion anisotropy, with a largest expansivity along a. Variations in Ni—O and V—O bonds with temperature are observed. The variation in the Ni—O bond is about one order higher in magnitude than that of the V—O bond, signifying the high rigidity of V—O bonds. The unit-cell size variations with rising effective ionic volume of the divalent A ion in the A3B2O8 family [A = Ni, Mg, Zn, Co, Mn (experimental data) and also A = Cu, Cd (theoretical data), B = V or As] are analyzed. Based on experimental and theoretical data, trends within the family are observed and the unit-cell size for reported solid solution of nickel (87%) and copper (13%) mixture in (Ni1–xCux)3V2O8 are predicted. Predictions are also provided for some hypothetical A3B2O8 ternary compound and solid solutions. Full Article text
x Synthesis and structural study of the partially disordered complex hexagonal phase δ1-MnZn9.7 By journals.iucr.org Published On :: 2024-10-02 A detailed structural analysis of the Zn-rich δ1-MnZn9.7 phase using single-crystal X-ray diffraction is presented. The δ1 phase has been synthesized by the high-temperature synthetic route. The structure crystallizes in space group P63/mmc (Pearson symbol hP556) with unit-cell parameters: a = b = 12.9051 (2) Å and c = 57.640 (1) Å. The 556 atoms are distributed over 52 Wyckoff positions in the hexagonal unit cell: seven ordered Mn sites, 37 ordered Zn sites and eight positionally disordered Zn sites. The structure predominantly consists of Frank–Kasper polyhedra (endohedral icosahedra Zn12 and icosioctahedron Zn16) and four distinct types of glue Zn atoms. The structure comprises a 127-atom supercluster (Mn13Zn114), a 38-atom extended Pearce cluster (Mn3Zn35), a 46-atom L-tetrahedron (Mn4Zn42), a Friauf polyhedron (Zn17), a disordered icosahedral cluster (MnZn12) and four glue Zn atoms. Positionally disordered Zn sites around an Mn site can be visualized as the superimposition of three differently oriented Zn12 icosahedra. Full Article text
x Contrasting conformational behaviors of molecules XXXI and XXXII in the seventh blind test of crystal structure prediction By journals.iucr.org Published On :: 2024-10-14 Accurate modeling of conformational energies is key to the crystal structure prediction of conformational polymorphs. Focusing on molecules XXXI and XXXII from the seventh blind test of crystal structure prediction, this study employs various electronic structure methods up to the level of domain-local pair natural orbital coupled cluster singles and doubles with perturbative triples [DLPNO-CCSD(T1)] to benchmark the conformational energies and to assess their impact on the crystal energy landscapes. Molecule XXXI proves to be a relatively straightforward case, with the conformational energies from generalized gradient approximation (GGA) functional B86bPBE-XDM changing only modestly when using more advanced density functionals such as PBE0-D4, ωB97M-V, and revDSD-PBEP86-D4, dispersion-corrected second-order Møller–Plesset perturbation theory (SCS-MP2D), or DLPNO-CCSD(T1). In contrast, the conformational energies of molecule XXXII prove difficult to determine reliably, and variations in the computed conformational energies appreciably impact the crystal energy landscape. Even high-level methods such as revDSD-PBEP86-D4 and SCS-MP2D exhibit significant disagreements with the DLPNO-CCSD(T1) benchmarks for molecule XXXII, highlighting the difficulty of predicting conformational energies for complex, drug-like molecules. The best-converged predicted crystal energy landscape obtained here for molecule XXXII disagrees significantly with what has been inferred about the solid-form landscape experimentally. The identified limitations of the calculations are probably insufficient to account for the discrepancies between theory and experiment on molecule XXXII, and further investigation of the experimental solid-form landscape would be valuable. Finally, assessment of several semi-empirical methods finds r2SCAN-3c to be the most promising, with conformational energy accuracy intermediate between the GGA and hybrid functionals and a low computational cost. Full Article text
x Assessment of the exchange-hole dipole moment dispersion correction for the energy ranking stage of the seventh crystal structure prediction blind test By journals.iucr.org Published On :: 2024-10-15 The seventh blind test of crystal structure prediction (CSP) methods substantially increased the level of complexity of the target compounds relative to the previous tests organized by the Cambridge Crystallographic Data Centre. In this work, the performance of density-functional methods is assessed using numerical atomic orbitals and the exchange-hole dipole moment dispersion correction (XDM) for the energy-ranking phase of the seventh blind test. Overall, excellent performance was seen for the two rigid molecules (XXVII, XXVIII) and for the organic salt (XXXIII). However, for the agrochemical (XXXI) and pharmaceutical (XXXII) targets, the experimental polymorphs were ranked fairly high in energy amongst the provided candidate structures and inclusion of thermal free-energy corrections from the lattice vibrations was found to be essential for compound XXXI. Based on these results, it is proposed that the importance of vibrational free-energy corrections increases with the number of rotatable bonds. Full Article text
x Polymorph sampling with coupling to extended variables: enhanced sampling of polymorph energy landscapes and free energy perturbation of polymorph ensembles By journals.iucr.org Published On :: 2024-10-15 A novel approach to computationally enhance the sampling of molecular crystal structures is proposed and tested. This method is based on the use of extended variables coupled to a Monte Carlo based crystal polymorph generator. Inspired by the established technique of quasi-random sampling of polymorphs using the rigid molecule constraint, this approach represents molecular clusters as extended variables within a thermal reservoir. Polymorph unit-cell variables are generated using pseudo-random sampling. Within this framework, a harmonic coupling between the extended variables and polymorph configurations is established. The extended variables remain fixed during the inner loop dedicated to polymorph sampling, enforcing a stepwise propagation of the extended variables to maintain system exploration. The final processing step results in a polymorph energy landscape, where the raw structures sampled to create the extended variable trajectory are re-optimized without the thermal coupling term. The foundational principles of this approach are described and its effectiveness using both a Metropolis Monte Carlo type algorithm and modifications that incorporate replica exchange is demonstrated. A comparison is provided with pseudo-random sampling of polymorphs for the molecule coumarin. The choice to test a design of this algorithm as relevant for enhanced sampling of crystal structures was due to the obvious relation between molecular structure variables and corresponding crystal polymorphs as representative of the inherent vapor to crystal transitions that exist in nature. Additionally, it is shown that the trajectories of extended variables can be harnessed to extract fluctuation properties that can lead to valuable insights. A novel thermodynamic variable is introduced: the free energy difference between ensembles of Z' = 1 and Z' = 2 crystal polymorphs. Full Article text
x X-ray crystallographic structure of a novel enantiopure chiral isothiourea with potential applications in enantioselective synthesis By journals.iucr.org Published On :: 2024-01-01 The synthesis of a chiral isothiourea, namely, (4aR,8aR)-3-phenyl-4a,5,6,7,8,8a-hexahydrobenzo[4,5]imidazo[2,1-b]thiazol-9-ium bromide, C15H17N2S+·Br−, with potential organocatalytic and anti-inflammatory activity is reported. The preparation of the heterocycle of interest was carried out in two high-yielding steps. The hydrobromide salt of the isothiourea of interest provided suitable crystals for X-ray diffraction analysis, the results of which are reported. Salient observations from this analysis are the near perpendicular arrangement of the phenyl ring and the mean plane of the heterocycle. This conformational characteristic may be relevant with regard the stereoselectivity induced by the chiral isothiourea in asymmetric reactions. Furthermore, evidence was found for the existence of an S...Br− halogen bond. Full Article text
x Crystal structures of three uranyl–acetate–bipyridine complexes crystallized from hydraulic fracking fluid By journals.iucr.org Published On :: 2024-01-01 Hydraulic fracking exposes shale plays to acidic hydraulic fracking fluid (HFF), releasing toxic uranium (U) along with the desired oil and gas. With no existing methods to ensure U remains sequestered in the shale, this study sought to add organic ligands to HFF to explore potential U retention in shale plays. To test this possibility, incubations were set up in which uranyl acetate and one organic bipyridine ligand (either 2,2'-, 2,3'-, 2,4'-, or 4,4'-bipyridine) were added to pristine HFF as the crystallization medium. After several months and complete evaporation of all volatiles, bulk yellow crystalline material was obtained from the incubations, three of which yielded crystals suitable for single-crystal analysis, resulting in two novel structures and a high-quality structure of a previously described compound. The UO2VI acetate complexes bis(acetato-κ2O,O')(2,2'-bipyridine-κ2N,N')dioxidouranium(VI), [U(C2H3O2)2O2(C10H8N2)2] or [2,2'-bipyridine]UVIO2(CH3CO2)2, (I), and bis(acetato-κ2O,O')(2,4'-bipyridine-κN1')dioxidouranium(VI), [U(C2H3O2)2O2(C10H8N2)2] or [2,4'-bipyridine]2UVIO2(CH3CO2)2, (III), contain eight-coordinate UVI in a pseudo-hexagonal bipyramidal coordination geometry and are molecular, packing via weak C—H...O/N interactions, whereas catena-poly[bis(2,3'-bipyridinium) [di-μ-acetato-μ3-hydroxido-μ-hydroxido-di-μ3-oxido-hexaoxidotriuranium(VI)]–2,3'-bipyridine–water (1/1/1)], (C10H9N2)2[U3(C2H3O2)2O8(OH)2]·C10H8N2·H2O or {[2,3'-bipyridinium]2[2,3'-bipyridine][(UVIO2)3(O)2(OH)2(CH3CO2)2·H2O]}n, (II), forms an ionic one-dimensional polymer with seven-coordinate pentagonal bipyramidal UVI centers and hydrogen-bonding interactions within each chain. The formation of these crystals could indicate the potential for bipyridine to bind with U in shale during fracking, which will be explored in a future study via ICP-MS (inductively coupled plasma mass spectrometry) analyses of U concentration in HFF/bipyridine/shale incubations. The variation seen here between the molecular structures may indicate variance in the ability of bipyridine isomers to form complexes with U, which could impact their ability to retain U within shale in the context of fracking. Full Article text
x Analytical models representing X-ray form factors of ions By journals.iucr.org Published On :: 2024-01-01 Parameters in analytical models for X-ray form factors of ions f0(s), based on the inverse Mott–Bethe formula involving a variable number of Gaussians, are determined for a wide range of published data sets {s, f0(s)}. The models reproduce the calculated form-factor values close to what is expected from a uniform statistical distribution with limits determined by their precision. For different ions associated with the same atom, the number of Gaussians in the models decreases with increasing net positive charge. Full Article text
x 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
x N-representable one-electron reduced density matrix reconstruction with frozen core electrons By journals.iucr.org Published On :: 2024-03-21 Recent advances in quantum crystallography have shown that, beyond conventional charge density refinement, a one-electron reduced density matrix (1-RDM) satisfying N-representability conditions can be reconstructed using jointly experimental X-ray structure factors and directional Compton profiles (DCP) through semidefinite programming. So far, such reconstruction methods for 1-RDM, not constrained to idempotency, have been tested only on a toy model system (CO2). In this work, a new method is assessed on crystalline urea [CO(NH2)2] using static (0 K) and dynamic (50 K) artificial experimental data. An improved model, including symmetry constraints and frozen core-electron contribution, is introduced to better handle the increasing system complexity. Reconstructed 1-RDMs, deformation densities and DCP anisotropy are analysed, and it is demonstrated that the changes in the model significantly improve the reconstruction quality, even when there is insufficient information and data corruption. The robustness of the model and the strategy are thus shown to be well adapted to address the reconstruction problem from actual experimental scattering data. Full Article text