met Emmett Duffy named director of Smithsonian’s Tennenbaum Marine Observatories Network By insider.si.edu Published On :: Wed, 19 Jun 2013 16:05:15 +0000 Emmett Duffy, currently the Gluckman Professor of Marine Science at the College of William & Mary in Virginia, has been appointed director of the Smithsonian’s […] The post Emmett Duffy named director of Smithsonian’s Tennenbaum Marine Observatories Network appeared first on Smithsonian Insider. Full Article Marine Science Research News Science & Nature biodiversity Caribbean Center for Tropical Forest Science conservation conservation biology Forest Global Earth Observatory National Museum of Natural History ocean acidification
met Toxic methylmercury-producing microbes more widespread than realized By insider.si.edu Published On :: Fri, 13 Sep 2013 12:29:04 +0000 Microbes that live in rice paddies, northern peat bogs and other previously unexpected environments are among the bacteria that can generate highly toxic methylmercury, researchers […] The post Toxic methylmercury-producing microbes more widespread than realized appeared first on Smithsonian Insider. Full Article Marine Science Research News Science & Nature conservation conservation biology Smithsonian Environmental Research Center
met Micro-Observatory catches comet ISON By insider.si.edu Published On :: Fri, 22 Nov 2013 16:44:37 +0000 Hopes are high for Comet ISON, which has the potential to become the most spectacular comet seen in years. ISON is speeding through the inner […] The post Micro-Observatory catches comet ISON appeared first on Smithsonian Insider. Full Article Research News Science & Nature astronomy astrophysics Center for Astrophysics | Harvard & Smithsonian Smithsonian Astrophysical Observatory
met The Submillimeter Array: Celebrating a decade of discovery By insider.si.edu Published On :: Wed, 25 Jun 2014 15:02:46 +0000 Ten years ago, eight antennas on the summit of Mauna Kea, Hawai’i, united to form a telescope unlike any other. Since then the Submillimeter Array […] The post The Submillimeter Array: Celebrating a decade of discovery appeared first on Smithsonian Insider. Full Article Research News Science & Nature Space astronomy astrophysics Center for Astrophysics | Harvard & Smithsonian Smithsonian Astrophysical Observatory technology
met Comet probe set to answer ancient question of life on earth By insider.si.edu Published On :: Thu, 13 Nov 2014 16:17:33 +0000 A few images of comet 67P/Churyumov-Gerasimenko just sent back by the European spaceship Rosetta appear to be a snowboarder’s dream: pristine slopes covered in powder. […] The post Comet probe set to answer ancient question of life on earth appeared first on Smithsonian Insider. Full Article Q & A Science & Nature Space astrophysics National Air and Space Museum
met Monitoring methane? Now there is a better way to measure By insider.si.edu Published On :: Tue, 10 Nov 2015 19:57:39 +0000 Now here is something to ruminate on. About 85 percent of the methane produced by a cow comes out of its mouth as burps. The […] The post Monitoring methane? Now there is a better way to measure appeared first on Smithsonian Insider. Full Article Animals Research News Science & Nature carbon dioxide climate change conservation conservation biology National Museum of Natural History technology
met Theorists Propose a New Method to Probe the Beginning of the Universe By insider.si.edu Published On :: Tue, 26 Jan 2016 18:57:55 +0000 How did the universe begin? And what came before the Big Bang? Cosmologists have asked these questions ever since discovering that our universe is expanding. […] The post Theorists Propose a New Method to Probe the Beginning of the Universe appeared first on Smithsonian Insider. Full Article Research News Science & Nature Space astronomy astrophysics Center for Astrophysics | Harvard & Smithsonian
met Methanol reveals comets forming in distant solar system By insider.si.edu Published On :: Wed, 15 Jun 2016 13:06:51 +0000 Astronomers announced today that they have found the organic molecule methyl alcohol, or methanol, in the TW Hydrae protoplanetary disk. This is the first such […] The post Methanol reveals comets forming in distant solar system appeared first on Smithsonian Insider. Full Article Research News Science & Nature Space astronomy astrophysics Center for Astrophysics | Harvard & Smithsonian Smithsonian Astrophysical Observatory
met Astronomers detect comets transiting distant stars By insider.si.edu Published On :: Thu, 01 Feb 2018 14:21:55 +0000 There are currently more than 3,500 confirmed known exoplanets thanks to the remarkable sensitivity of the Kepler spacecraft and to technological advances in space and […] The post Astronomers detect comets transiting distant stars appeared first on Smithsonian Insider. Full Article Science & Nature Space Spotlight Center for Astrophysics | Harvard & Smithsonian
met Compartmentalization of adenosine metabolism in cancer cells and its modulation during acute hypoxia [RESEARCH ARTICLE] By jcs.biologists.org Published On :: 2020-04-21T05:32:09-07:00 Karolina Losenkova, Mariachiara Zuccarini, Marika Karikoski, Juha Laurila, Detlev Boison, Sirpa Jalkanen, and Gennady G. YegutkinExtracellular adenosine mediates diverse anti-inflammatory, angiogenic and vasoactive effects and becomes an important therapeutic target for cancer, which has been translated into clinical trials. This study was designed to comprehensively assess adenosine metabolism in prostate and breast cancer cells. We identified cellular adenosine turnover as a complex cascade, comprised of (a) the ectoenzymatic breakdown of ATP via sequential nucleotide pyrophosphatase/phosphodiesterase-1, ecto-5’-nucleotidase/CD73 and adenosine deaminase reactions, and ATP re-synthesis through counteracting adenylate kinase and nucleoside diphosphokinase; (b) the uptake of nucleotide-derived adenosine via equilibrative nucleoside transporters; and (c) the intracellular adenosine phosphorylation into ATP by adenosine kinase and other nucleotide kinases. The exposure of cancer cells to 1% O2 for 24 hours triggered ~2-fold up-regulation of CD73, without affecting nucleoside transporters, adenosine kinase activity and cellular ATP content. The ability of adenosine to inhibit the tumor-initiating potential of breast cancer cells via receptor-independent mechanism was confirmed in vivo using a xenograft mouse model. The existence of redundant pathways controlling extracellular and intracellular adenosine provides a sufficient justification for reexamination of the current concepts of cellular purine homeostasis and signaling in cancer. Full Article
met BMP4 promotes the metastasis of gastric cancer by inducing epithelial-mesenchymal transition via Id1 [RESEARCH ARTICLE] By jcs.biologists.org Published On :: 2020-05-06T08:30:40-07:00 Ganlu Deng, Yihong Chen, Cao Guo, Ling Yin, Ying Han, Yiyi Li, Yaojie Fu, Changjing Cai, Hong Shen, and Shan ZengEpithelial-mesenchymal transition (EMT) is a crucial process for cancer cells to acquire metastatic potential, which primarily causes death in gastric cancer (GC) patients. Bone morphogenetic protein 4 (BMP4) is a member of the TGF-β family that plays an indispensable role in human cancers. However, little is known about its roles in GC metastasis. In this study, BMP4 was found to be frequently overexpressed in GC tissues and was correlated with patient's poor prognosis. BMP4 was upregulated in GC cell lines and promoted EMT and metastasis of GC cells both in vitro and in vivo, while knockdown of BMP4 significantly inhibited EMT and metastasis of GC cells. Meanwhile, the inhibitor of DNA binding 1 (Id1) was identified as a downstream target of BMP4 by PCR arrays and upregulated via Smad1/5/8 phosphorylation. Id1 knockdown attenuated BMP4-induced EMT and invasion in GC cells. Moreover, Id1 overexpression in BMP4 knockdown cells restored the promotion of EMT and cell invasion. In summary, BMP4 induced EMT to promote GC metastasis by upregulating Id1 expression. Antagonizing BMP4 may be a potential therapeutic strategy in GC metastasis. Full Article
met Nakhla meteorite By insider.si.edu Published On :: Wed, 29 Jun 2011 16:04:26 +0000 On June 28, 1911, the Nakhla meteorite (a piece of which is shown here) fell to Earth at approximately 9 a.m. in the Nakhla region of Alexandria, Egypt. Many people witnessed its explosion in the upper atmosphere before the meteorite shattered into some 40 pieces. Some fragments were buried a meter deep in the ground. The post Nakhla meteorite appeared first on Smithsonian Insider. Full Article Earth Science Research News Science & Nature Space Spotlight astrophysics geology meteorites National Museum of Natural History
met Iowa meteorite crater confirmed By insider.si.edu Published On :: Tue, 05 Mar 2013 20:21:08 +0000 Recent airborne geophysical surveys near Decorah, Iowa are providing an unprecedented look at a 470-million-year-old meteorite crater concealed beneath bedrock and sediments. The aerial surveys, […] The post Iowa meteorite crater confirmed appeared first on Smithsonian Insider. Full Article Earth Science Science & Nature Space astronomy astrophysics geology meteorites National Museum of Natural History prehistoric rocks & minerals
met Pieces of rare meteorite land at five different academic institutions By insider.si.edu Published On :: Thu, 22 Aug 2013 13:46:37 +0000 The main mass of a rare meteorite that exploded over California’s Sierra foothills in April 2012 will be preserved for current and future scientific discoveries, […] The post Pieces of rare meteorite land at five different academic institutions appeared first on Smithsonian Insider. Full Article Earth Science Research News Science & Nature astronomy astrophysics geology meteorites National Museum of Natural History new acquisitions
met Beautiful meteorites hold clues to solar system’s violent start By insider.si.edu Published On :: Fri, 27 Mar 2015 12:42:15 +0000 What was happening (geologically speaking) on Earth way back when it was a mere babe and being showered with meteorites? Until a time machine is […] The post Beautiful meteorites hold clues to solar system’s violent start appeared first on Smithsonian Insider. Full Article Earth Science Research News Science & Nature Space asteroids astronomy astrophysics geology materials science meteorites National Museum of Natural History planets prehistoric rocks & minerals technology
met Ancient Native-American methods may be key to sustainable oyster harvests By insider.si.edu Published On :: Mon, 23 May 2016 19:05:32 +0000 Oysters are keystone organisms in estuaries around the world, influencing water quality, constructing habitat and providing food for humans and wildlife. Yet their populations in […] The post Ancient Native-American methods may be key to sustainable oyster harvests appeared first on Smithsonian Insider. Full Article Animals Anthropology Earth Science History & Culture Marine Science Science & Nature Spotlight Chesapeake Bay conservation conservation biology fishes National Museum of Natural History prehistoric Smithsonian Conservation Biology Institute
met NASA, Smithsonian renew hunt for Antarctic meteorites By insider.si.edu Published On :: Mon, 28 Nov 2016 20:28:43 +0000 NASA, the National Science Foundation and the Smithsonian recently renewed their agreement to search for, collect and curate Antarctic meteorites in a partnership known as […] The post NASA, Smithsonian renew hunt for Antarctic meteorites appeared first on Smithsonian Insider. Full Article Earth Science Science & Nature Space Spotlight meteorites National Museum of Natural History
met Ancient Native American beads traced to otherworldy source: an iron meteorite By insider.si.edu Published On :: Tue, 23 May 2017 16:19:33 +0000 To the Hopewell Culture, ancient Native Americans who sought out the exotic from near and far, metal was a rare and precious resource. Copper, found […] The post Ancient Native American beads traced to otherworldy source: an iron meteorite appeared first on Smithsonian Insider. Full Article Anthropology Earth Science History & Culture Science & Nature Space astrophysics National Museum of Natural History prehistoric rocks & minerals
met A new method for in situ structural investigations of nano-sized amorphous and crystalline materials using mixed-flow reactors By scripts.iucr.org Published On :: 2019-08-23 Structural investigations of amorphous and nanocrystalline phases forming in solution are historically challenging. Few methods are capable of in situ atomic structural analysis and rigorous control of the system. A mixed-flow reactor (MFR) is used for total X-ray scattering experiments to examine the short- and long-range structure of phases in situ with pair distribution function (PDF) analysis. The adaptable experimental setup enables data collection for a range of different system chemistries, initial supersaturations and residence times. The age of the sample during analysis is controlled by adjusting the flow rate. Faster rates allow for younger samples to be examined, but if flow is too fast not enough data are acquired to average out excess signal noise. Slower flow rates form older samples, but at very slow speeds particles settle and block flow, clogging the system. Proper background collection and subtraction is critical for data optimization. Overall, this MFR method is an ideal scheme for analyzing the in situ structures of phases that form during crystal growth in solution. As a proof of concept, high-resolution total X-ray scattering data of amorphous and crystalline calcium phosphates and amorphous calcium carbonate were collected for PDF analysis. Full Article text
met Cluster-mining: an approach for determining core structures of metallic nanoparticles from atomic pair distribution function data By scripts.iucr.org Published On :: 2020-01-01 A novel approach for finding and evaluating structural models of small metallic nanoparticles is presented. Rather than fitting a single model with many degrees of freedom, libraries of clusters from multiple structural motifs are built algorithmically and individually refined against experimental pair distribution functions. Each cluster fit is highly constrained. The approach, called cluster-mining, returns all candidate structure models that are consistent with the data as measured by a goodness of fit. It is highly automated, easy to use, and yields models that are more physically realistic and result in better agreement to the data than models based on cubic close-packed crystallographic cores, often reported in the literature for metallic nanoparticles. Full Article text
met Distinguishing space groups by electron channelling: centrosymmetric full-Heusler or non-centrosymmetric half-Heusler? By scripts.iucr.org Published On :: 2020-02-19 X-ray emission under electron-channelling conditions is used to distinguish between a non-centrosymmetric half-Heusler and a centrosymmetric full-Heusler crystal. For TiCo1.5+xSn the space-group determination based on a Rietveld refinement procedure became challenging for increasing Co content (x > 0.2), while electron channelling proved successful for higher Co content (x = 0.35). This technique can be used on crystals as small as (10 nm)3. Full Article text
met An efficient method for indexing grazing-incidence X-ray diffraction data of epitaxially grown thin films By scripts.iucr.org Published On :: 2020-04-02 Crystal structure identification of thin organic films entails a number of technical and methodological challenges. In particular, if molecular crystals are epitaxially grown on single-crystalline substrates a complex scenario of multiple preferred orientations of the adsorbate, several symmetry-related in-plane alignments and the occurrence of unknown polymorphs is frequently observed. In theory, the parameters of the reduced unit cell and its orientation can simply be obtained from the matrix of three linearly independent reciprocal-space vectors. However, if the sample exhibits unit cells in various orientations and/or with different lattice parameters, it is necessary to assign all experimentally obtained reflections to their associated individual origin. In the present work, an effective algorithm is described to accomplish this task in order to determine the unit-cell parameters of complex systems comprising different orientations and polymorphs. This method is applied to a polycrystalline thin film of the conjugated organic material 6,13-pentacenequinone (PQ) epitaxially grown on an Ag(111) surface. All reciprocal vectors can be allocated to unit cells of the same lattice constants but grown in various orientations [sixfold rotational symmetry for the contact planes (102) and (102)]. The as-determined unit cell is identical to that reported in a previous study determined for a fibre-textured PQ film. Preliminary results further indicate that the algorithm is especially effective in analysing epitaxially grown crystallites not only for various orientations, but also if different polymorphs are present in the film. Full Article text
met SPIND-TC: an indexing method for two-color X-ray diffraction data By scripts.iucr.org Published On :: 2020-04-02 Recent developments of two-color operation modes at X-ray free-electron laser facilities provide new research opportunities, such as X-ray pump/X-ray probe experiments and multiple-wavelength anomalous dispersion phasing methods. However, most existing indexing methods were developed for indexing diffraction data from monochromatic X-ray beams. Here, a new algorithm is presented for indexing two-color diffraction data, as an extension of the sparse-pattern indexing algorithm SPIND, which has been demonstrated to be capable of indexing diffraction patterns with as few as five peaks. The principle and implementation of the two-color indexing method, SPIND-TC, are reported in this paper. The algorithm was tested on both simulated and experimental data of protein crystals. The results show that the diffraction data can be accurately indexed in both cases. Source codes are publicly available at https://github.com/lixx11/SPIND-TC. Full Article text
met Glimpse into the Smithsonian National Museum of Natural History’s new meteorite storage facility By insider.si.edu Published On :: Thu, 14 Feb 2013 15:03:50 +0000 Don your clean room clothing and take a glimpse into the Smithsonian's new Antarctic meteorite storage facility in Suitland, Md., where all of the Antarctic meteorites in the national collection are kept under tight security and tight airlocks. The post Glimpse into the Smithsonian National Museum of Natural History’s new meteorite storage facility appeared first on Smithsonian Insider. Full Article Space Video astronomy astrophysics meteorites National Museum of Natural History
met Rockin’ out: Bats learn to love heavy metal music By insider.si.edu Published On :: Wed, 08 Oct 2014 10:00:56 +0000 How do you train a wild animal to come back to you after you have set it free? If it is a fringe-lipped bat, Trachops […] The post Rockin’ out: Bats learn to love heavy metal music appeared first on Smithsonian Insider. Full Article Animals Research News Science & Nature Video bats conservation biology guitar mammals music Tropical Research Institute
met Climate change conundrum: Invasive reed makes much more methane By insider.si.edu Published On :: Mon, 17 Jun 2013 14:17:10 +0000 Phragmites australis, the common reed, has been a component of North American marshes for thousands of years. However, a novel genetic lineage, Phragmites australis australis, […] The post Climate change conundrum: Invasive reed makes much more methane appeared first on Smithsonian Insider. Full Article Marine Science Plants Research News Science & Nature biodiversity carbon dioxide climate change conservation biology greenhouse gas invasive species Smithsonian Environmental Research Center
met Crystal structure and characterization of a new copper(II) chloride dimer with methyl(pyridin-2-ylmethylidene)amine By journals.iucr.org Published On :: The new copper(II) complex [CuLCl2]2, where L is a product of Schiff base condensation between methylamine and 2-pyridinecarbaldehyde, is built of discrete centrosymmetric dimers. Full Article text
met The crystal structure and Hirshfeld surface analysis of 1-(2,5-dimethoxyphenyl)-2,2,6,6-tetramethylpiperidine By journals.iucr.org Published On :: The title compound, 1-(2,5-dimethoxyphenyl)-2,2,6,6-tetramethylpiperidine, was synthesized as a side-product during the synthesis of the intermediate, methyl 3,6-dimethoxy-2-(2-methoxy-2-oxoethyl)benzoate, necessary for the total synthesis of the isocoumarin 5,8-dimethoxy-3-methyl-1H-isochromen-1-one. Full Article text
met Crystal structure and Hirshfeld surface analysis of 4-{2,2-dichloro-1-[(E)-(4-fluorophenyl)diazenyl]ethenyl}-N,N-dimethylaniline By journals.iucr.org Published On :: The dihedral angle between the two aromatic rings of the title compound is 64.12 (14)°. The crystal structure is stabilized by a short Cl⋯H contact, C—Cl⋯π and van der Waals interactions. Full Article text
met Updating direct methods By scripts.iucr.org Published On :: 2019-01-01 The standard method of joint probability distribution functions, so crucial for the development of direct methods, has been revisited and updated. It consists of three steps: identification of the reflections which may contribute to the estimation of a given structure invariant or seminvariant, calculation of the corresponding joint probability distribution, and derivation of the conditional distribution of the invariant or seminvariant phase given the values of some diffracted amplitudes. In this article the conditional distributions are derived directly without passing through the second step. A good feature of direct methods is that they may work in the absence of any prior information: that is also their weakness. Different types of prior information have been taken into consideration: interatomic distances, interatomic vectors, Patterson peaks, structural model. The method of directly deriving the conditional distributions has been applied to those cases. Some new formulas have been obtained estimating two-, three- and four-phase invariants. Special attention has been dedicated to the practical aspects of the new formulas, in order to simplify their possible use in direct phasing procedures. Full Article text
met Anomalous small viral shells and simplest polyhedra with icosahedral symmetry: the rhombic triacontahedron case By scripts.iucr.org Published On :: 2019-01-01 The development of antiviral strategies requires a clear understanding of the principles that control the protein arrangements in viral shells. Considered here are those capsids that violate the paradigmatic Caspar and Klug (CK) model, and it is shown that the important structural features of such anomalous shells from the Picobirnaviridae, Flaviviridae and Leviviridae families can be revealed by models in the form of spherical icosahedral packings of equivalent rhombic structural units (SUs). These SUs are composed of protein dimers forming the investigated capsids which, as shown here, are based on the rhombic triacontahedron (RT) geometry. How to modify the original CK approach in order to make it compatible with the considered rhombic tessellations of a sphere is also discussed. Analogies between capsids self-assembled from dimers and trimers are demonstrated. This analysis reveals the principles controlling the localization of receptor proteins (which recognize the host cell) on the capsid surface. Full Article text
met Modeling of energy-dispersive X-ray diffraction for high-symmetry crystal orientation By scripts.iucr.org Published On :: 2019-01-01 The methods for X-ray crystal orientation are rapidly evolving towards versatility, fewer goniometry measurements, automation, high accuracy and precision. One method that attracts a lot of attention is energy-dispersive X-ray diffraction (EDXRD) which is based on detecting reflections from crystallographic planes in a crystal at fixed angles of a parallel polychromatic X-ray incident beam. In theory, an EDXRD peak can move in a diffraction pattern as a function of a crystallographic plane d-spacing and its orientation relative to a fixed direction in space can change also. This is equivalent to the possibility of measuring the orientation of single crystals. The article provides a modeling for the EDXRD method whose main feature is the nonmoving crystal in the sense of traditional goniometry where the angle measurements of diffracting planes are a must. The article defines the equation of orientation for the method and shows the derivation in great detail. It is shown that the exact solutions of the equations can be obtained using the generalized reduced gradient method, a mathematical subroutine that is implemented in Excel software. The significance and scientific impact of the work are discussed along with the validated tested results. Full Article text
met Crystal structure and Hirshfeld surface analysis of 4-{2,2-dichloro-1-[(E)-(4-fluorophenyl)diazenyl]ethenyl}-N,N-dimethylaniline By scripts.iucr.org Published On :: 2020-05-06 In the title compound, C16H14Cl2FN3, the dihedral angle between the two aromatic rings is 64.12 (14)°. The crystal structure is stabilized by a short Cl...H contact, C—Cl...π and van der Waals interactions. The Hirshfeld surface analysis and two-dimensional fingerprint plots show that H...H (33.3%), Cl...H/H...Cl (22.9%) and C...H/H...C (15.5%) interactions are the most important contributors towards the crystal packing. Full Article text
met The crystal structure and Hirshfeld surface analysis of 1-(2,5-dimethoxyphenyl)-2,2,6,6-tetramethylpiperidine By scripts.iucr.org Published On :: 2020-05-05 In the title compound, C17H27NO2, the piperidine ring has a chair conformation and is positioned normal to the benzene ring. In the crystal, molecules are linked by C—H...O hydrogen bonds, forming chains propagating along the c-axis direction. Full Article text
met Crystal structure and characterization of a new copper(II) chloride dimer with methyl(pyridin-2-ylmethylidene)amine By scripts.iucr.org Published On :: 2020-05-05 The new copper(II) complex, namely, di-μ-chlorido-bis{chlorido[methyl(pyridin-2-ylmethylidene)amine-κ2N,N']copper(II)}, [Cu2Cl4(C7H8N2)2], (I), with the ligand 2-pyridylmethyl-N-methylimine (L, a product of Schiff base condensation between methylamine and 2-pyridinecarbaldehyde) is built of discrete centrosymmetric dimers. The coordination about the CuII ion can be described as distorted square pyramidal. The base of the pyramid consists of two nitrogen atoms from the bidentate chelate L [Cu—N = 2.0241 (9), 2.0374 (8) Å] and two chlorine atoms [Cu—Cl = 2.2500 (3), 2.2835 (3) Å]. The apical position is occupied by another Cl atom with the apical bond being significantly elongated at 2.6112 (3) Å. The trans angles of the base are 155.16 (3) and 173.79 (2)°. The Cu...Cu separation in the dimer is 3.4346 (3) Å. In the crystal structure, the loosely packed dimers are arranged in stacks propagating along the a axis. The X-band polycrystalline 77 K EPR spectrum of (I) demonstrates a typical axial pattern characteristic of mononuclear CuII complexes. Compound (I) is redox active and shows a cyclic voltammetric response with E1/2 = −0.037 V versus silver–silver chloride electrode (SSCE) assignable to the reduction peak of CuII/CuI in methanol as solvent. Full Article text
met A simple graphical method to pinpoint local pseudosymmetries in Z' > 1 cases By scripts.iucr.org Published On :: 2019-06-26 An intuitive method is presented for detecting pseudosymmetries in Z' > 1 cases as a complement to well-proven strategies already available in the literature. It is based in the simple idea that the mid-points between equivalent atoms in symmetrically related molecules are disposed according to simple well-known patterns, which are easily recognizable by optical inspection. A number of Z' = 4 cases in the literature are analyzed, which allows some of the potentialities of the method to be revealed. Full Article text
met A new tool for finding approximate symmetry By scripts.iucr.org Published On :: 2019-06-26 Full Article text
met Deciphering the hydrogen-bonding scheme in the crystal structure of triphenylmethanol: a tribute to George Ferguson and co-workers By scripts.iucr.org Published On :: 2019-08-14 The crystal structure of triphenylmethanol, C19H16O, has been redetermined using data collected at 295 and 153 K, and is compared to the model published by Ferguson et al. over 25 years ago [Ferguson et al. (1992). Acta Cryst. C48, 1272–1275] and that published by Serrano-González et al., using neutron and X-ray diffraction data [Serrano-González et al. (1999). J. Phys. Chem. B, 103, 6215–6223]. As predicted by these authors, the hydroxy groups are involved in weak intermolecular hydrogen bonds in the crystal, forming tetrahedral tetramers based on the two independent molecules in the asymmetric unit, one of which is placed on the threefold symmetry axis of the Roverline{3} space group. However, the reliable determination of the hydroxy H-atom positions is difficult to achieve, for two reasons. Firstly, a positional disorder affects the full asymmetric unit, which is split over two sets of positions, with occupancy factors of ca 0.74 and 0.26. Secondly, all hydroxy H atoms are further disordered, either by symmetry, or through a positional disorder in the case of parts placed in general positions. We show that the correct description of the hydrogen-bonding scheme is possible only if diffraction data are collected at low temperature. The prochiral character of the hydrogen-bonded tetrameric supramolecular clusters leads to enantiomorphic three-dimensional graphs in each tetramer. The crystal is thus a racemic mixture of supS and supR motifs, consistent with the centrosymmetric nature of the Roverline{3} space group. Full Article text
met Absolute structure of the chiral pyrrolidine derivative (2S)-methyl (Z)-5-(2-tert-butoxy-1-cyano-2-oxoethylidene)pyrrolidine-2-carboxylate, a compound with low resonant scattering By scripts.iucr.org Published On :: 2019-10-04 The enantiopure monopyrrolidine derivative (2S)-methyl (Z)-5-(2-tert-butoxy-1-cyano-2-oxoethylidene)pyrrolidine-2-carboxylate, C13H18N2O4, (1), represents a potential ligand and an attractive intermediate for the synthesis of chiral metal complexes. At the molecular level, the compound features an intramolecular N—H⋯O hydrogen bond; neighbouring molecules interact via N—H⋯N contacts to form chains along [100]. Due to its elemental composition, resonant scattering of the target compound is entirely insignificant for diffraction experiments with Mo Kα and small even for Cu Kα radiation. A preliminary study with the harder radiation type confirmed the chiral space group and the suitability of the single crystal chosen; as expected, the results concerning the absolute structure remained completely inconclusive. A second data collection with the longer wavelength gave satisfactory quality indicators for the correct handedness of the molecule, albeit with high standard uncertainties. The absolute configuration has been assessed independently: CD spectra for both enantiomers of the target molecule were calculated and the spectrum for the S-configured stereoisomer was in agreement with the experiment. The Cotton effect of (1) may be ascribed to π–π* transitions from HOMO to LUMO and from HOMO to LUMO+1. As both independent techniques agree with respect to the handedness of the target molecule, the absolute structure may be assigned with a high degree of confidence. Full Article text
met Synthesis, decomposition studies and crystal structure of a three-dimensional CuCN network structure with protonated N-methylethanolamine as the guest cation By scripts.iucr.org Published On :: 2020-04-17 The compound poly[2-hydroxy-N-methylethan-1-aminium [μ3-cyanido-κ3C:C:N-di-μ-cyanido-κ4C:N-dicuprate(I)]], {(C3H10NO)[Cu2(CN)3]}n or [meoenH]Cu2(CN)3, crystallizes in the tetragonal space group P43. The structure consists of a three-dimensional (3D) anionic CuICN network with noncoordinated protonated N-methylethanolamine cations providing charge neutrality. Pairs of cuprophilic Cu atoms are bridged by the C atoms of μ3-cyanide ligands, which link these units into a 43 spiral along the c axis. The spirals are linked together into a 3D anionic network by the two other cyanide groups. The cationic moieties are linked into their own 43 spiral via N—H⋯O and O—H⋯O hydrogen bonds, and the cations interact with the 3D network via an unusual pair of N—H⋯N hydrogen bonds to one of the μ2-cyanide groups. Thermogravimetric analysis indicates an initial loss of the base cation and one cyanide as HCN at temperatures in the range 130–250 °C to form CuCN. We show how loss of a specific cyanide group from the 3D CuCN structure could form the linear CuCN structure. Further heating leaves a residue of elemental copper, isolated as the oxide. Full Article text
met LaTe1.82(1): modulated crystal structure and chemical bonding of a chalcogen-deficient rare earth metal polytelluride By scripts.iucr.org Published On :: 2020-05-06 Crystals of the rare earth metal polytelluride LaTe1.82(1), namely, lanthanum telluride (1/1.8), have been grown by molten alkali halide flux reactions and vapour-assisted crystallization with iodine. The two-dimensionally incommensurately modulated crystal structure has been investigated by X-ray diffraction experiments. In contrast to the tetragonal average structure with unit-cell dimensions of a = 4.4996 (5) and c = 9.179 (1) Å at 296 (1) K, which was solved and refined in the space group P4/nmm (No. 129), the satellite reflections are not compatible with a tetragonal symmetry but enforce a symmetry reduction. Possible space groups have been derived by group–subgroup relationships and by consideration of previous reports on similar rare earth metal polychalcogenide structures. Two structural models in the orthorhombic superspace group, i.e. Pmmn(α,β,1 over 2)000(−α,β,1 over 2)000 (No. 59.2.51.39) and Pm21n(α,β,1 over 2)000(−α,β,1 over 2)000 (No. 31.2.51.35), with modulation wave vectors q1 = αa* + βb* + 1 over 2c* and q2 = −αa* + βb* + 1 over 2c* [α = 0.272 (1) and β = 0.314 (1)], have been established and evaluated against each other. The modulation describes the distribution of defects in the planar [Te] layer, coupled to a displacive modulation due to the formation of different Te anions. The bonding situation in the planar [Te] layer and the different Te anion species have been investigated by density functional theory (DFT) methods and an electron localizability indicator (ELI-D)-based bonding analysis on three different approximants. The temperature-dependent electrical resistance revealed a semiconducting behaviour with an estimated band gap of 0.17 eV. Full Article text
met Crystallization of metastable monoclinic carnallite, KCl·MgCl2·6H2O: missing structural link in the carnallite family By scripts.iucr.org Published On :: 2020-04-29 During evaporation of natural and synthetic K–Mg–Cl brines, the formation of almost square plate-like crystals of potassium carnallite (potassium chloride magnesium dichloride hexahydrate) was observed. A single-crystal structure analysis revealed a monoclinic cell [a = 9.251 (2), b = 9.516 (2), c = 13.217 (4) Å, β = 90.06 (2)° and space group C2/c]. The structure is isomorphous with other carnallite-type compounds, such as NH4Cl·MgCl2·6H2O. Until now, natural and synthetic carnallite, KCl·MgCl2·6H2O, was only known in its orthorhombic form [a = 16.0780 (3), b = 22.3850 (5), c = 9.5422 (2) Å and space group Pnna]. Full Article text
met Polymorphism and phase transformation in the dimethyl sulfoxide solvate of 2,3,5,6-tetrafluoro-1,4-diiodobenzene By scripts.iucr.org Published On :: 2020-04-30 A new polymorph (form II) is reported for the 1:1 dimethyl sulfoxide solvate of 2,3,5,6-tetrafluoro-1,4-diiodobenzene (TFDIB·DMSO or C6F4I2·C2H6SO). The structure is similar to that of a previously reported polymorph (form I) [Britton (2003). Acta Cryst. E59, o1332–o1333], containing layers of TFDIB molecules with DMSO molecules between, accepting I⋯O halogen bonds from two TFDIB molecules. Re-examination of form I over the temperature range 300–120 K shows that it undergoes a phase transformation around 220 K, where the DMSO molecules undergo re-orientation and become ordered. The unit cell expands by ca 0.5 Å along the c axis and contracts by ca 1.0 Å along the a axis, and the space-group symmetry is reduced from Pnma to P212121. Refinement of form I against data collected at 220 K captures the (average) structure of the crystal prior to the phase transformation, with the DMSO molecules showing four distinct disorder components, corresponding to an overlay of the 297 and 120 K structures. Assessment of the intermolecular interaction energies using the PIXEL method indicates that the various orientations of the DMSO molecules have very similar total interaction energies with the molecules of the TFDIB framework. The phase transformation is driven by interactions between DMSO molecules, whereby re-orientation at lower temperature yields significantly closer and more stabilizing interactions between neighbouring DMSO molecules, which lock in an ordered arrangement along the shortened a axis. Full Article text
met An efficient method for indexing grazing-incidence X-ray diffraction data of epitaxially grown thin films By journals.iucr.org Published On :: A method is described for indexing grazing-incidence X-ray diffraction data of epitaxially grown thin films comprising various crystal orientations and/or polymorphs by measuring reciprocal-lattice vectors. Full Article text
met Geometric realizations of abstract regular polyhedra with automorphism group H3 By journals.iucr.org Published On :: A method is adapted to generate a full rank realization of an abstract regular polyhedron with automorphism group H3. Full Article text
met Wedge reversion antisymmetry and 41 types of physical quantities in arbitrary dimensions By journals.iucr.org Published On :: Physical quantities in arbitrary dimensional space can be classified into 41 types using three antisymmetries within the framework of Clifford algebra. Full Article text
met Testing of a `hard' X-ray interferometer for experimental investigations By journals.iucr.org Published On :: A new type of X-ray LLL interferometer, a `hard' interferometer, which has both a base and a `ceiling', is tested for experimental investigations. The tested interferometer has no preliminary uncontrollable moiré and can be used for object and deformation investigations. Full Article text
met Study identifies main culprit behind lithium metal battery failure By feedproxy.google.com Published On :: 2019-08-26T07:00:00Z Full Text:A National Science Foundation-funded research has discovered the root cause of why lithium metal batteries fail -- bits of lithium metal deposits break off from the surface of the anode during discharging and are trapped as "dead" or inactive lithium that the battery can no longer access. The discovery challenges the conventional belief that lithium metal batteries fail because of the growth of a layer, called the solid electrolyte interphase (SEI), between the lithium anode and the electrolyte. The researchers made their discovery by developing a technique to measure the amounts of inactive lithium species on the anode -- a first in the field of battery research -- and studying their micro- and nanostructures. The findings could pave the way for bringing rechargeable lithium metal batteries from the lab to the market.Image credit: University of California - San Diego Full Article
met Japan-based payment methods Konbini, Pay-easy join PPRO payments platform By feedproxy.google.com Published On :: Wed, 06 May 2020 15:10:00 +0200 PPRO has entered the Japanese ecommerce market, as two... Full Article
met Computer crashes and reboots, sometimes unable to power on By www.bleepingcomputer.com Published On :: 2020-04-09T13:19:44-05:00 Full Article