Smithsonian scientists and colleagues, however, have recently found evidence that gymnosperm plants shared an intricate pollination relationship with scorpionfly insects 62 million years before flowering plants appear in fossil records.

The post Prehistoric pollination: Scorpionfly mouthparts fit tubular channels of gymnosperm cones appeared first on Smithsonian Insider.

This new research has revealed that in areas considered unsuitable for farming today, "pre-Columbian farmers constructed thousands of raised fields in the seasonally flooded coastal savannas of the Guianas.

The post Amazon farmers who vanished centuries ago were remarkably innovative appeared first on Smithsonian Insider.

Healthy reefs with more corals and fish generate predictably greater levels of noise, according to researchers working in Panama. By analysing recordings of coral reefs from the Las Perlas Archipelago in Pacific Panama ( Central America ), marine biologists working from the Smithsonian Tropical Research Institute have found that some reefs are noisier than others, and these differences in noise provide useful information about the health of the reef.

The post A noisy reef is a healthy reef appeared first on Smithsonian Insider.

Obsessive in his collecting and emotionally invested in contributing to science and perpetuating knowledge, Palmer lived the adventurous yet nomadic life of a collector.

The post Remarkable ethnobotany collections of Edward Palmer highlighted in new Smithsonian Website appeared first on Smithsonian Insider.

Candy Feller, senior ecologist at the Smithsonian Environmental Research Center in Edgewater, Md., will lead an effort to track more than 100 miles of Florida mangrove forests that are encroaching on salt marshes to the north.

The post NASA to help Smithsonian botanists track northern creep of Florida mangroves appeared first on Smithsonian Insider.

These opportunistic plants quickly fill-in the gap taking advantage of the increased light coming through the tree canopy and the fresh soil at the fallen tree’s turned-up roots.

The post Falling trees help invasive wineberry move into deciduous forests in North America appeared first on Smithsonian Insider.

In 1909, naturalist Dr. Edgar A. Mearns joined Theodore Roosevelt and scientists from the Smithsonian and New York’s American Museum of Natural History on an […]

The post New project will improve access to thousands of scientific field books, journals and notes in Smithsonian collections appeared first on Smithsonian Insider.

The post Introducing Leafsnap, an electronic field guide to North America trees run on a mobile phone app appeared first on Smithsonian Insider.

The post Smithsonian scientists work to ensure survival of North America’s wild orchids appeared first on Smithsonian Insider.

A joint Harvard-Smithsonian study released today in the journal PLOS ONE reveals how much — and how little — Northeastern forests have changed after centuries of intensive […]

The post 400-year study finds Northeast forests resilient, changing  appeared first on Smithsonian Insider.

As mangrove trees lose ground to deforestation and urban sprawl, one development seems to be giving them a boost: climate change. Fewer winter cold snaps […]

The post Mangroves creep north in response to warmer temperatures appeared first on Smithsonian Insider.

Why do we love orchids so much? Tom Mirenda, Smithsonian Gardens orchid collection specialist, believes it is partly because orchids seem to look back at […]

The post 5 Crazy Things You Didn’t Know About Orchids appeared first on Smithsonian Insider.

The Smithsonian’s National Museum of Natural History announced today that scientists with the museum’s Global Genome Initiative will attempt to capture the genomic diversity of half the […]

The post Smithsonian and Partners To Preserve Earth’s Genomic Plant Diversity appeared first on Smithsonian Insider.

This year’s El Niño event is one of the strongest on record and is still ramping up. Large parts of the tropics are turning into […]

The post Major El Nino Perfect opportunity for Global Change Research appeared first on Smithsonian Insider.

Long ago, one great ocean flowed between North and South America. When the narrow Isthmus of Panama joined the continents about 3 million years ago, […]

The post Recent Connection Between North and South America Reaffirmed appeared first on Smithsonian Insider.

At the approach of a hungry parrot snake, a tree frog egg transforms from a haven to a prison. With no parent to offer protection, […]

The post Mystery solved: frogs use snout glands in emergency jail break appeared first on Smithsonian Insider.

By now, most of the United States has started to feel the first cool caresses of winter. Everything is pumpkin spiced, and the last crickets […]

The post Feathered diplomats unite pupils in North and Central America appeared first on Smithsonian Insider.

To catch lizards on the offshore islands close to St. Croix in the Caribbean, Smithsonian herpetologist Nicole Angeli uses a lasso of thread looped at […]

The post Mongooses wiped them out. Now Nicole Angeli wants the St. Croix ground lizard home again appeared first on Smithsonian Insider.

The cationic cyclo­metallated iridium(III) complex [Ir(C9H7N2)2(C12H8N2)](PF6) has been synthesized and crystallized by the inter-diffusion method. It contains an unknown number of solvent mol­ecules and has a different space-group symmetry (C2/c) structure than its solvatomorph (P21/c).

The asymmetric unit of the title compound contains two independent mol­ecules, consisting of perimidine and phenol units, which are linked through an N—H⋯O hydrogen bond. Intra­molecular O—H⋯N hydrogen bonds are observed in both independent mol­ecules.

Febuxostat and ethanol mol­ecules are linked into an O—H⋯O and O—H⋯N bonded chain structure.

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.

The structural and nonlinear optical properties of a new anilinium hybrid crystal of chemical formula (C6H7NCl+·NO3−)3 have been investigated. The crystal structure was determined from single-crystal X-ray diffraction measurements performed at a temperature of 100 K which show that the compound crystallizes in a noncentrosymmetric space group (Pna21). The structural analysis was coupled with Hirshfeld surface analysis to evaluate the contribution of the different intermolecular interactions to the formation of supramolecular assemblies in the solid state that exhibit nonlinear optical features. This analysis reveals that the studied compound is characterized by a three-dimensional network of hydrogen bonds and the main contributions are provided by the O...H, C...H, H...H and Cl...H interactions, which alone represent ∼85% of the total contributions to the Hirshfeld surfaces. It is noteworthy that the halogen...H contributions are quite comparable with those of the H...H contacts. The nonlinear optical properties were investigated by nonlinear diffuse femtosecond-pulse reflectometry and the obtained results were compared with those of the reference material LiNbO3. The hybrid crystals exhibit notable second (SHG) and third (THG) harmonic generation which confirms its polarity is generated by the different intermolecular interactions. These measurements also highlight that the THG signal of the new anilinium compound normalized to its SHG counterpart is more pronounced than for LiNbO3.

In a Model block, if the instance-specific value of a model argument has an anonymous structure type, an update diagram reports an error when there are multiple bus types that match that anonymous structure type.This bug exists in the following release(s):
R2020a

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Simulink might produce an incorrect sorted order for a model that meets all of the following conditions:

• The model contains blocks from the SoC Blockset
• The Signal logging option is selected in the model configuration set
• Signals using asynchronous sample time are configured for logging

If you try to open a text file with UTF-16 or UTF-32 encoding, the Import Tool displays a warning message stating that the encoding is not supported.  If you continue to load the file anyways, it is opened with UTF-8 encoding, and the file may not be displayed or imported as expected.This bug exists in the following release(s):
R2020a

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The cationic complex in the title compound, [Ir(C9H7N2)2(C12H8N2)]PF6, comprises two phenylpyrazole (ppz) cyclometallating ligands and one 1,10-phenanthroline (phen) ancillary ligand. The asymmetric unit consists of one [Ir(ppz)2(phen)]+ cation and one [PF6]− counter-ion. The central IrIII ion is six-coordinated by two N atoms and two C atoms from the two ppz ligands as well as by two N atoms from the phen ligand within a distorted octahedral C2N4 coordination set. In the crystal structure, the [Ir(ppz)2(phen)]+ cations and PF6− counter-ions are connected with each other through weak intermolecular C—H...F hydrogen bonds. Additional C—H...π interactions between the rings of neighbouring cations consolidate the three-dimensional network. Electron density associated with additional disordered solvent molecules inside cavities of the structure was removed with the SQUEEZE procedure in PLATON [Spek (2015). Acta Cryst. C71, 9–18]. The given chemical formula and other crystal data do not take into account the unknown solvent molecule(s). The title compound has a different space-group symmetry (C2/c) from its solvatomorph (P21/c) comprising 1.5CH2Cl2 solvent molecules per ion pair.

The asymmetric unit of the title compound, C17H14N2O, contains two independent molecules each consisting of perimidine and phenol units. The tricyclic perimidine units contain naphthalene ring systems and non-planar C4N2 rings adopting envelope conformations with the C atoms of the NCN groups hinged by 44.11 (7) and 48.50 (6)° with respect to the best planes of the other five atoms. Intramolecular O—H...N hydrogen bonds may help to consolidate the molecular conformations. The two independent molecules are linked through an N—H...O hydrogen bond. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H...H (52.9%) and H...C/C...H (39.5%) interactions. Hydrogen bonding and van der Waals interactions are the dominant interactions in the crystal packing. Density functional theory (DFT) optimized structures at the B3LYP/ 6–311 G(d,p) level are compared with the experimentally determined molecular structure in the solid state. The HOMO–LUMO behaviour was elucidated to determine the energy gap.

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.

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.

An efficient synthesis of 1-aryl­isochromeno[3,4-d][1,2,3]triazol-5(1H)-ones, involving the diazo­tization of 3-amino-4-aryl­amino-1H-isochromen-1-ones in weakly acidic solution, has been developed and the spectroscopic characterization and crystal structures of four examples are reported. The mol­ecules of 1-phenyl­isochromeno[3,4-d][1,2,3]triazol-5(1H)-one, C15H9N3O2, (I), are linked into sheets by a combination of C—H⋯N and C—H⋯O hydrogen bonds, while the structures of 1-(2-methyl­phen­yl)isochromeno[3,4-d][1,2,3]triazol-5(1H)-one, C16H11N3O2, (II), and 1-(3-chloro­phen­yl)isochromeno[3,4-d][1,2,3]triazol-5(1H)-one, C15H8ClN3O2, (III), each contain just one hydrogen bond which links the mol­ecules into simple chains, which are further linked into sheets by π-stacking inter­actions in (II) but not in (III). In the structure of 1-(4-chloro­phen­yl)isochromeno[3,4-d][1,2,3]triazol-5(1H)-one, (IV), isomeric with (III), a combination of C—H⋯O and C—H⋯π(arene) hydrogen bonds links the mol­ecules into sheets. When com­pound (II) was exposed to a strong acid in methanol, qu­anti­tative conversion occurred to give the ring-opened transesterification product methyl 2-[4-hy­droxy-1-(2-methyl­phen­yl)-1H-1,2,3-triazol-5-yl]benzoate, C17H15N3O3, (V), where the mol­ecules are linked by paired O—H⋯O hydrogen bonds to form centrosymmetric dimers.