met Something Wild: Peepers, The Unmistakable Sound of Spring By www.nhpr.org Published On :: Fri, 09 Apr 2021 15:59:23 +0000 It’s an unmistakable sound. One that elicits memories, sights and scents of events long ago. It recalls the joy of youth, the possibility of a spring evening. But it can also incite insomnia and the blind rage that accompanies it. Full Article
met Something Wild: N.H.'s Wildest Neighborhoods By www.nhpr.org Published On :: Mon, 17 May 2021 15:55:07 +0000 Here at Something Wild, we love all things wild (even blackflies !) but sometimes it can be helpful to look beyond a single species and consider how many species interact within a given environment. In our periodic series, New Hampshire’s Wild Neighborhoods, we endeavor to do just that and this time we’re looking at peatlands. Full Article
met Something Wild: Olfaction Action What's Your Reaction? By www.nhpr.org Published On :: Fri, 16 Jul 2021 20:19:17 +0000 We know…we’ve been remiss, and it’s time to talk about the elephant in the room. Something Wild, as you know, is a chance to take a closer look at the wildlife, ecosystems and marvelous phenomena you can find in and around New Hampshire. But over the years there is one species in New Hampshire that we haven’t spent much time examining. A species, I think that has been conspicuous in its absence. Humans. Full Article
met Something Wild: What Happens to Trees in Drought? By www.nhpr.org Published On :: Fri, 05 Jul 2019 10:40:00 +0000 The specter of drought is often raised in these early days of summer. And for good reason, though water levels have returned to normal around the New Hampshire, state officials are still warning residents to remain cautious after last summer drought. And while we often fret about the health of our lawns and our gardens, Dave (from the Forest Society) wanted to address drought resistance among his favorite species, trees. So, we all know that trees need water to survive. Basically the many leaves on a given tree have these pore-like holes called stomates that leak moisture into the surrounding air. As that vapor exits the tree through the leaves it draws more water up through the trunk and branches, like through a bundle of straws. Harnessing the power of the sun, trees break apart that water into its constituent hydrogen and oxygen molecules; forming glucose with the hydrogen and exhaling the oxygen into the atmosphere. The glucose is what fuels growth in the tree, from buds to bark to Full Article
met Something Wild: Smell that Olfactory By www.nhpr.org Published On :: Fri, 02 Aug 2019 10:01:00 +0000 We know…we’ve been remiss, and it’s time to talk about the elephant in the room. Something Wild, as you know, is a chance to take a closer look at the wildlife, ecosystems and marvelous phenomena you can find in and around New Hampshire. But over the years there is one species in New Hampshire that we haven’t spent much time examining. A species, I think that has been conspicuous in its absence. Humans. So we’re grabbing the bull by the horns and digging in to a complex species that is an important part of the ecosystem. And we thought we’d start with a particular trait that’s been with us almost since the beginning: olfaction. The sense of smell among other sensory systems are relatively unchanged throughout mammalian history. As Nate Dominy, professor of anthropology and biological sciences at Dartmouth, says, “a lot of the traits we see in mammals are retention of those basic traits.” Dominy suggested our olfactory sense was really important to our proto-mammalian ancestors. Picture Full Article
met Something Wild: How Scatter Hoarders Prepare for Winter By www.nhpr.org Published On :: Fri, 16 Aug 2019 20:30:00 +0000 You may be familiar with hoarders (not the TV show, but same idea). In nature, a hoarder will hide food in one place. Everything it gathers will be stored in a single tree or den. But for some animals one food cache isn't enough. We call them scatter hoarders. A "scatter hoarder" hides food in a bunch of different places within its territory. The gray squirrel is a classic example, gathering acorns and burying them in trees or in the ground. Not all squirrels are hoarders. Red squirrels are "larder hoarders." If you've ever been walking through the woods and a red squirrel starts screaming at you, it's defending its one and only stash. The same goes for chipmunks and white-footed mice. The gray squirrel isn't alone in the practice of scatter hoarding. Blue jays and gray jays will spend the summer accosting hikers, filling itself with as much granola or fruit as it can. They bring their bounty back into the forest and glue the food into crevices of the trees with its saliva. I know, who Full Article
met Something Wild: It's All in the Breeding By www.nhpr.org Published On :: Fri, 30 Aug 2019 12:28:00 +0000 A common theme on Something Wild is breeding. (Which is why we always sip our tea with our pinkies extended.) Seriously, though, we talk about the how, when and where because there are a lot of different reproductive strategies that have evolved in nature. Today we take a closer look at two such strategies through the lens of "how often": semelparity and iteroparity. Full Article
met Something Wild: Tree Sex By www.nhpr.org Published On :: Fri, 23 Apr 2021 15:30:45 +0000 Spring in New Hampshire is a double-edged sword. On one hand you have longer, warmer days — plants and trees are blooming! On the other hand, the pollen springtime trees produce can present an array of unpleasant seasonal symptoms. Yet pollen is so incredibly important to our survival – we think we should give it the credit it deserves. O ur friend Sam Evans Brown is the host of NHPR’s Outside/In; when pollen makes his eyes watery and the roof of his mouth itchy this time of year, Sam likes to remember that " the pollen that you’re breathing, and that your body is freaking out over... is you know… is half of the equation of tree sex. So you’re breathing in a little bit of tree sex which is you know... just a fun thing to think about." If you can recall your middle school science class you might remember that pollen is the male reproductive product of tree flowers — found on the anther and filament of male stamens — used to make new plant life. It needs to reach the sticky stigma, style Full Article
met Russia launches 170-meter-long surprise for Washington By english.pravda.ru Published On :: Fri, 21 Jan 2022 19:22:00 +0300 On January 11, 2022, Russia launched its second serial missile submarine of Project 955 Borei-A. Borei-A submarine: An unpleasant surprise for Washington The submarine cruiser is the brainchild of the Rubin Design Bureau. The vessel was built for seven years. This is a second-to-none submarine, just like its four brothers that are already on combat duty. Prior to this, on December 25 last year, the new submarine was solemnly taken out of the boathouse. The submarine will have to undergo complex trials at all levels before it can be handed over to the navy in 12 months. Full Article Science
met Residents of Russia's Far East observe comet-like object in evening sky By english.pravda.ru Published On :: Mon, 25 Mar 2024 19:34:00 +0300 Residents of the Far East of Russia could observe the movement of a space object in the sky. It is believed that the phenomenon that eyewitnesses filmed on video was Comet Pons-Brooks. This comet nears the Earth once in every 71 years. Huge luminous stripes appeared in the evening sky above the Khabarovsk and other neighbouring regions of Russia. The luminous object split into parts and slowly moved in the sky. Some observers thought they saw a rocket take off, or the passage of a comet or meteorite. Full Article Science
met Komet, a new kiosk solution by Aures By www.retailtechnologyreview.com Published On :: In addition to its knowhow as a manufacturer of complete ranges of POS systems (EPOS, Mobile POS / tablets), Aures Technologies is continuing its development in the kiosk and SCO sector (self-check-out or self-service check-out) and the omnichannel digital customer journey. Full Article Kiosk Technology Print & Label
met The Study Explores the Impact of Sterilization Methods on Aronia Juice Quality By www.newswise.com Published On :: Wed, 13 Nov 2024 02:10:18 EST A research team has conducted a comprehensive study on the effects of various sterilization methods on the quality of Aronia melanocarpa juice (AMJ). Full Article
met Tuning the Catalytic Behavior of Metal Oxides By www.newswise.com Published On :: Tue, 12 Nov 2024 14:45:40 EST The behavior of catalysts that promote chemical reactions is not always straightforward. Using a combination of experiments and computer simulations, scientists now understand how oxygen affects the way the catalyst copper oxide reacts with hydrogen versus carbon monoxide gases and how to control and enhance related chemical reactions. Full Article
met The Study Explores the Impact of Sterilization Methods on Aronia Juice Quality By www.newswise.com Published On :: Wed, 13 Nov 2024 02:10:18 EST A research team has conducted a comprehensive study on the effects of various sterilization methods on the quality of Aronia melanocarpa juice (AMJ). Full Article
met Lean Hypotheses and Effectual Commitments: An Integrative Framework Delineating the Methods of Science and Entrepreneurship By www.newswise.com Published On :: Wed, 13 Nov 2024 06:15:47 EST Full Article
met A Scientific Method for Startups By www.newswise.com Published On :: Fri, 08 Nov 2024 08:50:53 EST Full Article
met JSC: N. Korea Presumably Used 600-Millimeter Multiple Rocket Launchers to Fire Missiles By world.kbs.co.kr Published On :: Tue, 05 Nov 2024 16:10:46 +0900 [Inter-Korea] : North Korea is presumed to have used its KN-25 600-millimeter multiple rocket launch system to fire off short-range ballistic missiles into the East Sea on Tuesday ahead of the U.S. presidential election. According to South Korea's Joint Chiefs of Staff(JCS), the missiles appeared to have reached ...[more...] Full Article Inter-Korea
met Metatron: Angel, Scribe and Former Human By people.howstuffworks.com Published On :: Tue, 12 Nov 2024 10:05:03 -0500 Metatron, angel and mediator between God and humanity, is one of the most mysterious and powerful figures in angelology. Full Article
met Let's Learn Mimetic Words in Korean! By world.kbs.co.kr Published On :: 2024-10-07 +09:00 Fall is the season of festivals and baseball here in Korea. What are some interesting festivals taking place around the country? What is the deal with the first pitch by celebrities at the baseball...[more...] Full Article Economy&It
met UK assessment of technology-critical minerals and metals - British Geological Survey By news.google.com Published On :: Thu, 12 Oct 2023 08:45:08 GMT UK assessment of technology-critical minerals and metals British Geological Survey Full Article
met 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
met A contribution to the crystal chemistry and topology of organic thiosulfates: bis(1-methylpiperazinium)·S2O3·H2O versus 1-methylpiperazinediium·S2O3·3H2O By journals.iucr.org Published On :: Crystal structure and topology of two new thiosulfates formed with mono- and diprotonated species of 1-methylpiperazine is reported. Full Article text
met The seventh blind test of crystal structure prediction: structure generation methods By journals.iucr.org Published On :: The results of the seventh blind test of crystal structure prediction are presented, focusing on structure generation methods. Full Article text
met The seventh blind test of crystal structure prediction: structure ranking methods By journals.iucr.org Published On :: The results of the seventh blind test of crystal structure prediction are presented, focusing on structure ranking methods. Full Article text
met Symmetry, magnetic transitions and multiferroic properties of B-site-ordered A2MnB'O6 perovskites (B' = [Co, Ni]) By journals.iucr.org Published On :: A comparative description is presented of the symmetry and the magnetic structures found in the family of double perovskites A2MnB'O6 (mainly B' = Co and some Ni compounds for comparative purposes). Full Article text
met 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
met 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
met Variable stoichiometry and salt-cocrystal intermediate in the multicomponents of flucytosine: structural elucidation and its impact on stability By journals.iucr.org Published On :: Five multicomponent solid forms of an antifungal drug flucytosine are reported with a hygroscopic stability study. A detailed CSD search on the cocrystal/salts of flucytosine is evaluated and correlated the structures based on bond angles and bond distances. Full Article text
met The seventh blind test of crystal structure prediction: structure ranking methods By journals.iucr.org Published On :: 2024-10-17 A seventh blind test of crystal structure prediction has been organized by the Cambridge Crystallographic Data Centre. The results are presented in two parts, with this second part focusing on methods for ranking crystal structures in order of stability. The exercise involved standardized sets of structures seeded from a range of structure generation methods. Participants from 22 groups applied several periodic DFT-D methods, machine learned potentials, force fields derived from empirical data or quantum chemical calculations, and various combinations of the above. In addition, one non-energy-based scoring function was used. Results showed that periodic DFT-D methods overall agreed with experimental data within expected error margins, while one machine learned model, applying system-specific AIMnet potentials, agreed with experiment in many cases demonstrating promise as an efficient alternative to DFT-based methods. For target XXXII, a consensus was reached across periodic DFT methods, with consistently high predicted energies of experimental forms relative to the global minimum (above 4 kJ mol−1 at both low and ambient temperatures) suggesting a more stable polymorph is likely not yet observed. The calculation of free energies at ambient temperatures offered improvement of predictions only in some cases (for targets XXVII and XXXI). Several avenues for future research have been suggested, highlighting the need for greater efficiency considering the vast amounts of resources utilized in many cases. Full Article text
met The seventh blind test of crystal structure prediction: structure generation methods By journals.iucr.org Published On :: 2024-12-01 A seventh blind test of crystal structure prediction was organized by the Cambridge Crystallographic Data Centre featuring seven target systems of varying complexity: a silicon and iodine-containing molecule, a copper coordination complex, a near-rigid molecule, a cocrystal, a polymorphic small agrochemical, a highly flexible polymorphic drug candidate, and a polymorphic morpholine salt. In this first of two parts focusing on structure generation methods, many crystal structure prediction (CSP) methods performed well for the small but flexible agrochemical compound, successfully reproducing the experimentally observed crystal structures, while few groups were successful for the systems of higher complexity. A powder X-ray diffraction (PXRD) assisted exercise demonstrated the use of CSP in successfully determining a crystal structure from a low-quality PXRD pattern. The use of CSP in the prediction of likely cocrystal stoichiometry was also explored, demonstrating multiple possible approaches. Crystallographic disorder emerged as an important theme throughout the test as both a challenge for analysis and a major achievement where two groups blindly predicted the existence of disorder for the first time. Additionally, large-scale comparisons of the sets of predicted crystal structures also showed that some methods yield sets that largely contain the same crystal structures. Full Article text
met Parameterized absorptive electron scattering factors By journals.iucr.org Published On :: 2024-01-25 In electron diffraction, thermal atomic motion produces incoherent scattering over a relatively wide angular range, which appears as a diffuse background that is usually subtracted from measurements of Bragg spot intensities in structure solution methods. The transfer of electron flux from Bragg spots to diffuse scatter is modelled using complex scattering factors f + if' in the Bloch wave methodology. In a two-beam Einstein model the imaginary `absorptive' scattering factor f' can be obtained by the evaluation of an integral containing f over all possible scattering angles. While more sophisticated models of diffuse scatter are widely used in the electron microscopy community, it is argued in this paper that this simple model is appropriate for current structure solution and refinement methods. The two-beam model is a straightforward numerical calculation, but even this simplistic approach can become time consuming for simulations of materials with large numbers of atoms in the unit cell and/or many incident beam orientations. Here, a parameterized form of f' is provided for 103 elements as neutral, spherical atoms that reduces calculation time considerably. Full Article text
met Universal parameters of bulk-solvent masks By journals.iucr.org Published On :: 2024-02-09 The bulk solvent is a major component of biomacromolecular crystals that contributes significantly to the observed diffraction intensities. Accurate modelling of the bulk solvent has been recognized as important for many crystallographic calculations. Owing to its simplicity and modelling power, the flat (mask-based) bulk-solvent model is used by most modern crystallographic software packages to account for disordered solvent. In this model, the bulk-solvent contribution is defined by a binary mask and a scale (scattering) function. The mask is calculated on a regular grid using the atomic model coordinates and their chemical types. The grid step and two radii, solvent and shrinkage, are the three parameters that govern the mask calculation. They are highly correlated and their choice is a compromise between the computer time needed to calculate the mask and the accuracy of the mask. It is demonstrated here that this choice can be optimized using a unique value of 0.6 Å for the grid step irrespective of the data resolution, and the radii values adjusted correspondingly. The improved values were tested on a large sample of Protein Data Bank entries derived from X-ray diffraction data and are now used in the computational crystallography toolbox (CCTBX) and in Phenix as the default choice. Full Article text
met The single-atom R1: a new optimization method to solve crystal structures By journals.iucr.org Published On :: 2024-03-18 A crystal structure with N atoms in its unit cell can be solved starting from a model with atoms 1 to j − 1 being located. To locate the next atom j, the method uses a modified definition of the traditional R1 factor where its dependencies on the locations of atoms j + 1 to N are removed. This modified R1 is called the single-atom R1 (sR1), because the locations of atoms 1 to j − 1 in sR1 are the known parameters, and only the location of atom j is unknown. Finding the correct position of atom j translates thus into the optimization of the sR1 function, with respect to its fractional coordinates, xj, yj, zj. Using experimental data, it has been verified that an sR1 has a hole near each missing atom. Further, it has been verified that an algorithm based on sR1, hereby called the sR1 method, can solve crystal structures (with up to 156 non-hydrogen atoms in the unit cell). The strategy to carry out this calculation has also been optimized. The main feature of the sR1 method is that, starting from a single arbitrarily positioned atom, the structure is gradually revealed. With the user's help to delete poorly determined parts of the structure, the sR1 method can build the model to a high final quality. Thus, sR1 is a viable and useful tool for solving crystal structures. Full Article text
met Bond topology of chain, ribbon and tube silicates. Part II. Geometrical analysis of infinite 1D arrangements of (TO4)n− tetrahedra By journals.iucr.org Published On :: 2024-04-29 In Part I of this series, all topologically possible 1-periodic infinite graphs (chain graphs) representing chains of tetrahedra with up to 6–8 vertices (tetrahedra) per repeat unit were generated. This paper examines possible restraints on embedding these chain graphs into Euclidean space such that they are compatible with the metrics of chains of tetrahedra in observed crystal structures. Chain-silicate minerals with T = Si4+ (plus P5+, V5+, As5+, Al3+, Fe3+, B3+, Be2+, Zn2+ and Mg2+) have a grand nearest-neighbour 〈T–T〉 distance of 3.06±0.15 Å and a minimum T⋯T separation of 3.71 Å between non-nearest-neighbour tetrahedra, and in order for embedded chain graphs (called unit-distance graphs) to be possible atomic arrangements in crystals, they must conform to these metrics, a process termed equalization. It is shown that equalization of all acyclic chain graphs is possible in 2D and 3D, and that equalization of most cyclic chain graphs is possible in 3D but not necessarily in 2D. All unique ways in which non-isomorphic vertices may be moved are designated modes of geometric modification. If a mode (m) is applied to an equalized unit-distance graph such that a new geometrically distinct unit-distance graph is produced without changing the lengths of any edges, the mode is designated as valid (mv); if a new geometrically distinct unit-distance graph cannot be produced, the mode is invalid (mi). The parameters mv and mi are used to define ranges of rigidity of the unit-distance graphs, and are related to the edge-to-vertex ratio, e/n, of the parent chain graph. The program GraphT–T was developed to embed any chain graph into Euclidean space subject to the metric restraints on T–T and T⋯T. Embedding a selection of chain graphs with differing e/n ratios shows that the principal reason why many topologically possible chains cannot occur in crystal structures is due to violation of the requirement that T⋯T > 3.71 Å. Such a restraint becomes increasingly restrictive as e/n increases and indicates why chains with stoichiometry TO<2.5 do not occur in crystal structures. Full Article text
met Universal simulation of absorption effects for X-ray diffraction in reflection geometry By journals.iucr.org Published On :: 2024-06-07 Analytical calculations of absorption corrections for X-ray powder diffraction experiments on non-ideal samples with surface roughness, porosity or absorption contrasts from multiple phases require complex mathematical models to represent their material distribution. In a computational approach to this problem, a practicable ray-tracing algorithm is formulated which is capable of simulating angle-dependent absorption corrections in reflection geometry for any given rasterized sample model. Single or multiphase systems with arbitrary surface roughness, porosity and spatial distribution of the phases in any combination can be modeled on a voxel grid by assigning respective values to each voxel. The absorption corrections are calculated by tracing the attenuation of X-rays along their individual paths via a modified shear-warp algorithm. The algorithm is presented in detail and the results of simulated absorption corrections on samples with various surface modulations are discussed in the context of published experimental results. Full Article text
met Crystal structure of the RNA-recognition motif of Drosophila melanogaster tRNA (uracil-5-)-methyltransferase homolog A By journals.iucr.org Published On :: 2024-01-25 Human tRNA (uracil-5-)-methyltransferase 2 homolog A (TRMT2A) is the dedicated enzyme for the methylation of uridine 54 in transfer RNA (tRNA). Human TRMT2A has also been described as a modifier of polyglutamine (polyQ)-derived neuronal toxicity. The corresponding human polyQ pathologies include Huntington's disease and constitute a family of devastating neurodegenerative diseases. A polyQ tract in the corresponding disease-linked protein causes neuronal death and symptoms such as impaired motor function, as well as cognitive impairment. In polyQ disease models, silencing of TRMT2A reduced polyQ-associated cell death and polyQ protein aggregation, suggesting this protein as a valid drug target against this class of disorders. In this paper, the 1.6 Å resolution crystal structure of the RNA-recognition motif (RRM) from Drosophila melanogaster, which is a homolog of human TRMT2A, is described and analysed. Full Article text
met Animations, videos and 3D models for teaching space-group symmetry By journals.iucr.org Published On :: Animations, videos and 3D models have been designed to visualize the effects of symmetry operators on selected cases of crystal structures, pointing out the relationship with the diagrams published in International Tables for Crystallography, Vol. A. Full Article text
met Optimizing crucible geometry to improve the quality of AlN crystals by the physical vapor transport method By journals.iucr.org Published On :: The growth quality of AlN single crystals was improved by optimizing the crucible structure for Al vapor transport with the help of finite element simulation. Full Article text
met 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
met Understanding secondary order parameters in perovskites with tilted octahedra By journals.iucr.org Published On :: A symmetry guide for the secondary structural degrees of freedom and related physical properties generated by tilts of BX6 octahedra in perovskites is proposed. Full Article text
met 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
met Symmetry groups of the Batak basketweave patterns By journals.iucr.org Published On :: The symmetry groups of the weave patterns of the baskets, trays and mats of the Batak, an indigenous community in the Philippines, are discussed in this paper. The two-way twofold weaving technique is used by the Batak, and this study points to a total of 15 layer groups found in the Batak weaves out of the 80 layer groups known in crystallography. Full Article text
met Crystal structures and circular dichroism of {2,2'-[(1S,2S)-1,2-diphenylethane-1,2-diylbis(nitrilophenylmethanylylidene)]diphenolato}nickel(II) and its ethanol solvate By journals.iucr.org Published On :: A chiral nickel(II) Schiff base complex derived from 2-hydroxybenzophenone and (1S,2S)-1,2-diphenylethylenediamine shows a λ conformation of the central diamine chelate ring. The substituents on the C&z-dbnd;N carbon atoms significantly affect the circular dichroism spectra. Full Article text
met Crystal structure and Hirshfeld-surface analysis of an etoxazole metabolite designated R13 By journals.iucr.org Published On :: The crystal structure of a metabolite of the insecticide/acaricide etoxazole, designated R13 is presented along with a Hirshfeld surface analysis of intermolecular interactions present in the crystal structure. Full Article text
met Crystal structures of two polymorphs for fac-bromidotricarbonyl[4-(4-methoxyphenyl)-2-(pyridin-2-yl)thiazole-κ2N,N']rhenium(I) By journals.iucr.org Published On :: Crystallization of the title compound from CH2Cl2/n-pentane (1:5 v/v) at room temperature gave two polymorphs, which crystallize in monoclinic (P21/c; α form) and orthorhombic (Pna21; β form) space groups. The ReI complex molecules in either polymorph adopt a six-coordinate octahedral geometry with three facially-oriented carbonyl ligands, one bromido ligand, and two nitrogen atoms from one chelating ligand ppt-OMe. In the crystal, both polymorph α and β form di-periodic sheet-like architectures supported by multiple hydrogen bonds. Full Article text
met Synthesis, crystal structure and Hirshfeld surface analysis of N-(4-methoxyphenyl)picolinamide By journals.iucr.org Published On :: The molecular and crystal structure of N-(4-methoxyphenyl)picolinamide were studied and Hirshfeld surfaces and fingerprint plots were generated to investigate various intermolecular interactions. Full Article text
met Animations, videos and 3D models for teaching space-group symmetry By journals.iucr.org Published On :: 2024-10-16 A series of animations, videos and 3D models that were developed, filmed or built to teach the symmetry properties of crystals are described. At first, these resources were designed for graduate students taking a basic crystallography course, coming from different careers, at the National Autonomous University of Mexico. However, the COVID-19 pandemic had the effect of accelerating the generation of didactic material. Besides our experience with postgraduate students, we have noted that 3D models attract the attention of children, and therefore we believe that these models are particularly useful for teaching children about the assembled arrangements of crystal structures. Full Article text
met 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
met 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
met Optimizing crucible geometry to improve the quality of AlN crystals by the physical vapor transport method By journals.iucr.org Published On :: 2024-10-16 In the conventional crucible structure for AlN crystal growth by physical vapor transport, owing to the long molecular transport path of Al vapor and the disruption of the gas flow by the presence of a deflector, the Al vapor easily forms polycrystals in the growth domain. The result is increased internal stress in the crystals and increased difficulty in growing large-sized crystals. On this basis, with the help of finite element simulations, a novel crucible structure is designed. This crucible not only optimizes the gas transport but also increases the radial gradient of the AlN crystal surface, making the enhanced growth rate in the central region more obvious. The thermal stresses between the deflector and the crystal are also reduced. High-quality AlN crystals with an FWHM of 79 arcsec were successfully grown with this structure, verifying the accuracy of finite element simulation of the growth of AlN crystals. Our work has important guiding significance for the growth of high-quality AlN crystals. Full Article text