Archives, Room Use Only - PS3539.A14 C52 1915

Archives, Room Use Only - HE7797.W53 R58 1950

Archives, Room Use Only - UG590.S54 1838

Archives, Room Use Only - QC527.T73 1895

Charge-assisted hydrogen bonding plays a significant role in the crystal structures of solvates of ionic com­pounds, especially when the cation or cations are primary ammonium salts. We report the crystal structures of four ammonium salts of molybdenum halide cluster solvates where we observe significant hydrogen bonding between the solvent molecules and cations. The crystal structures of bis­(anilinium) octa-μ3-chlorido-hexa­chlorido-octa­hedro-hexa­molybdate N,N-di­­methyl­formamide tetra­solvate, (C6H8N)2[Mo6Cl8Cl6]·4C3H7NO, (I), p-phenyl­enedi­ammonium octa-μ3-chlorido-hexa­chlorido-octa­hedro-hexa­mol­yb­date N,N-di­methyl­formamide hexa­solvate, (C6H10N2)[Mo6Cl8Cl6]·6C3H7NO, (II), N,N'-(1,4-phenyl­ene)bis­(propan-2-iminium) octa-μ3-chlorido-hexa­chlo­rido-octa­hedro-hexa­molybdate acetone tris­olvate, (C12H18N2)[Mo6Cl8Cl6]·3C3H6O, (III), and 1,1'-dimethyl-4,4'-bipyridinium octa-μ3-chlo­rido-hexa­chlorido-octa­hedro-hexa­molybdate N,N-di­methyl­formamide tetra­solvate, (C12H14N2)[Mo6Cl8Cl6]·4C3H7NO, (IV), are reported and described. In (I), the anilinium cations and N,N-di­methyl­formamide (DMF) solvent mol­ecules form a cyclic R42(8) hydrogen-bonded motif centered on a crystallographic inversion center with an additional DMF mol­ecule forming a D(2) inter­action. The p-phenyl­enedi­ammonium cation in (II) forms three D(2) inter­actions between the three N—H bonds and three independent N,N-di­methyl­formamide mol­ecules. The dication in (III) is a protonated Schiff base solvated by acetone mol­ecules. Compound (IV) contains a methyl viologen dication with N,N-di­methyl­formamide mol­ecules forming close contacts with both aromatic and methyl H atoms.

In the context of increasing hardware and software automation in the process of crystal structure determination by X-ray diffraction, and based on conference sessions presenting some of the experience of senior crystallographers for the benefit of younger colleagues, an outline is given here of some basic concepts and applications of symmetry in crystallography. Three specific examples of structure determinations are discussed, for which an understanding of these aspects of symmetry avoids mistakes that can readily be made by reliance on automatic procedures. Topics addressed include pseudo-symmetry, twinning, real and apparent disorder, chirality, and structure validation.

The fact that a protein crystal can serve as a chemical reaction vessel is intrinsically fascinating. That it can produce an electron-dense tetranuclear rhenium cluster compound from a rhenium tri­carbonyl tri­bromo starting compound adds to the fascination. Such a cluster has been synthesized previously in vitro, where it formed under basic conditions. Therefore, its synthesis in a protein crystal grown at pH 4.5 is even more unexpected. The X-ray crystal structures presented here are for the protein hen egg-white lysozyme incubated with a rhenium tri­carbonyl tri­bromo compound for periods of one and two years. These reveal a completed, very well resolved, tetra-rhenium cluster after two years and an intermediate state, where the carbonyl ligands to the rhenium cluster are not yet clearly resolved, after one year. A dense tetranuclear rhenium cluster, and its technetium form, offer enhanced contrast in medical imaging. Stimulated by these crystallography results, the unusual formation of such a species directly in an in vivo situation has been considered. It offers a new option for medical imaging compounds, particularly when considering the application of the pre-formed tetranuclear cluster, suggesting that it may be suitable for medical diagnosis because of its stability, preference of formation and biological compatibility.

Serial rotation electron diffraction (SerialRED) has been developed as a fully automated technique for three-dimensional electron diffraction data collection that can run autonomously without human intervention. It builds on the previously established serial electron diffraction technique, in which submicrometre-sized crystals are detected using image processing algorithms. Continuous rotation electron diffraction (cRED) data are collected on each crystal while dynamically tracking the movement of the crystal during rotation using defocused diffraction patterns and applying a set of deflector changes. A typical data collection screens up to 500 crystals per hour, and cRED data are collected from suitable crystals. A data processing pipeline is developed to process the SerialRED data sets. Hierarchical cluster analysis is implemented to group and identify the different phases present in the sample and to find the best matching data sets to be merged for subsequent structure analysis. This method has been successfully applied to a series of zeolites and a beam-sensitive metal–organic framework sample to study its capability for structure determination and refinement. Two multi-phase samples were tested to show that the individual crystal phases can be identified and their structures determined. The results show that refined structures obtained using automatically collected SerialRED data are indistinguishable from those collected manually using the cRED technique. At the same time, SerialRED has lower requirements of expertise in transmission electron microscopy and is less labor intensive, making it a promising high-throughput crystal screening and structure analysis tool.

Molybdenum oxides and sulfides on various low-cost high-surface-area supports are excellent catalysts for several industrially relevant reactions. The surface layer structure of these materials is, however, difficult to characterize due to small and disordered MoOx domains. Here, it is shown how X-ray total scattering can be applied to gain insights into the structure through differential pair distribution function (d-PDF) analysis, where the scattering signal from the support material is subtracted to obtain structural information on the supported structure. MoOx catalysts supported on alumina nanoparticles and on zeolites are investigated, and it is shown that the structure of the hydrated molybdenum oxide layer is closely related to that of disordered and polydisperse polyoxometalates. By analysing the PDFs with a large number of automatically generated cluster structures, which are constructed in an iterative manner from known polyoxometalate clusters, information is derived on the structural motifs in supported MoOx.

"This galaxy cluster wins the heavyweight title. It's among the most massive clusters ever found at this distance," said Mark Brodwin, a Smithsonian astronomer at the Harvard-Smithsonian Center for Astrophysics.

The post Newly discovered massive galaxy cluster wins heavyweight title appeared first on Smithsonian Insider.

Galaxies are sometimes found in large clusters with many hundreds of members. Typically there is a giant elliptical galaxy near the center; most of these ellipticals are very bright emitters of radio radiation as a result of activity around supermassive black holes at their nuclei.

The post Enriching the Intracluster Medium appeared first on Smithsonian Insider.

This composite image from the Chandra X-ray Observatory (operated for NASA by the Smithsonian Astrophysical Observatory) shows the distribution of dark matter, galaxies, and hot […]

The post Chandra image of the core of the merging galaxy cluster Abell 520 appeared first on Smithsonian Insider.

Vampire Squid Illustration, 1889 This Smithsonian Snapshot celebrates the Halloween season with this 1889 scientific illustration of a vampire squid from Smithsonian Libraries. Its jet-black […]

The post Vampire Squid Illustration appeared first on Smithsonian Insider.

Frontispiece illustration of “flies” from the 1882 book American game fishes, their habits, habitat, and peculiarities; how, when, and where to angle for them, featuring […]

The post Illustration from American game fishes, their habits, habitat, and peculiarities appeared first on Smithsonian Insider.

All stars begin their lives in groups. Most stars, including our Sun, are born in small, benign groups that quickly fall apart. Others form in […]

The post First transiting planets in a star cluster discovered appeared first on Smithsonian Insider.

W49A might be one of the best-kept secrets in our galaxy. This star-forming region shines 100 times brighter than the Orion nebula, but is so […]

The post SMA reveals giant star cluster in the making appeared first on Smithsonian Insider.

The galaxy known as M87 has a fastball that would be the envy of any baseball pitcher. It has thrown an entire star cluster toward […]

The post Star cluster thrown out of its galaxy appeared first on Smithsonian Insider.

Globular star clusters are extraordinary in almost every way. They’re densely packed, holding a million stars in a ball only about 100 light-years across on […]

The post Globular Clusters Could Nurture Interstellar Civilizations appeared first on Smithsonian Insider.

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.

Lodgepole pine drawn in 1898 by U.S. National Herbarium illustrator Frederick Andrew Walpole.

The post Frederick Walpole illustrations recovered appeared first on Smithsonian Insider.

A new exhibition will feature the work of a local illustrator.

A museum’s new exhibition will feature work by one of the most influential British book illustrators.

A St Albans-based artist has seen her work shortlisted for Waterstones Book of the Year 2019.

Spending hours in front of the computer can get lonely, but not for one Japanese illustrator who keeps an owl quite literally at hand.

Sex. Many (but not all) animals do it.

Vermont's Mount Stratton hosted a festival dedicated to yoga, meditation and overall mindfulness.

Maira Kalman, artist for Michael Pollan’s new illustrated edition of ‘Food Rules,’ shares her thoughts on food and her inspirations for her illustrations

A quiet deal between two of the world’s leading energy technology clusters, puts Copenhagen at the center of the expanding cleantech universe. Highlights from

Perfect for blustery apartment balconies, the student-designed O-Wind Turbine is a national winner of the James Dyson Award.

'Mobitecture' features portable works of architecture including campers, floating cabins and trampoline tents.

'The Art and Science of Ernst Haeckel' is a collection of beautifully illustrated flora and fauna by a German biologist and artist.

With photos and detailed insight, the new book "The Modern House Bus" offers a glimpse into the world of bus conversion projects.

About 20% of us have a genetic propensity that may compel us toward adventure and exploration.

Artist and scientist Jill Pelto hopes to inspire people to take action by imbuing her dreamy paintings with hard scientific data and field research.

A new paper in CRANIO Journal explains how the Sphenopalatine Ganglion is a common thread linking these disorders. Self-Administration of SPG Blocks and Neuromodulation on the Ganglion can dramtically improve patients quality of life.

The band combined the new track with a gritty self-produced music video.

Medical illustrators around the world are creating accurate visualizations and public education materials of SARS-CoV-2, the coronavirus that causes COVID-19.

Visual content demonstrates the best way to protect an accident injury case

An introduction to the DBSCAN algorithm and its Implementation in Python.

This post will unravel a practical example to illustrate and motivate the intuition behind each step of the spectral clustering algorithm.

Bill Kerr, a professor at Harvard Business School, studies the increasing importance of talent clusters in our age of rapid technological advances. He argues that while talent and industries have always had a tendency to cluster, today's trend towards San Francisco, Boston, London and a handful of other cities is different. Companies need to react and tap into those talent pools, but moving the company to one isn't always an option. Kerr talks about the three main ways companies can access talent. He's the author of the HBR article "Navigating Talent Hot Spots," as well as the book "The Gift of Global Talent: How Migration Shapes Business, Economy & Society."

National forest lands encompass numerous rural and urban communities. Some national-forest-based communities lie embedded within national forests, and others reside just outside the official boundaries of national forests. The urban and rural communities within or near national forest lands include a wide variety of historical traditions and cultural values that affect their process of economic development. National-forest-based urban and rural communities participate in numerous economic sectors including nontraded industries, resource-dependent traded industries, and non-resource-dependent traded industries. These communities represent microeconomic environments. Cluster theory provides an explicit framework to examine the microeconomic relationships between national forests and their embedded and neighboring communities. Implementation of economic cluster initiatives in national-forest-based communities could improve their overall social well-being through increased competitive advantage based on innovation and higher productivity. This paper proposes establishing an Economic Clusters research team within the Forest Service. This team would dedicate its efforts to the analysis and improvement of the determinants of competitive advantage affecting national-forest-based communities.

Ant and Dec are left hot under the collar by the dancing duo Jasmin and Aaron on Britain's Got Talent

“Je n’ai pas de sœur, c’est peut-être pour ça que je la cherche dans chaque femme” confie Maria Clara Macrì dans les pages de son livre 13 Moons to Find Her, qui devrait être publié prochainement. Cette quête de sororité s’est réalisée au travers d’une série de portraits (un projet au départ intitulé In Her Rooms) pour laquelle la photographe italienne a rencontré […]

En ces temps de confinement, l’heure est à l’évasion de l’esprit. Nous vous proposons aujourd’hui de découvrir le joli travail de l’illustratrice russe Darya Shnykina. Elle est l’auteure d’une série de créations intitulée Places I’d Love To Live In.  Elle a imaginé représenter d’adorables petites maisonnées solitaires en pleine nature. Des petits havres de paix où chacun […]

Cette période inédite de confinement a inspiré de nombreux artistes, dont fait partie l’illustrateur Mariano Pascual. L’artiste argentin établi à Barcelone a traduit en images les sentiments flous, désordonnés et un brin anxiogènes induits par la pandémie. Stocks de papier toilette, télétravail et laisser-aller derrière les portes closes de son domicile… À travers une série de visuels […]