Shallow-water seagrasses can’t survive without enough light. And fish, shrimp, crabs and other creatures we rely on for food can’t survive without seagrasses. Smithsonian biologist […]

The post Ecosystems on the Edge: Underwater Light and Seagrass appeared first on Smithsonian Insider.

Hidden in the thick foliage of tropical forests a subfamily of colorful beetles–the Chrysomelidae–may be hiding the secrets to the earliest stages of social behavior. […]

The post Beetle moms show clear signs of maternal instincts and care appeared first on Smithsonian Insider.

When scientists discuss global change, they often focus on the amount of carbon in the atmosphere and vegetation. But soil contains more carbon than air […]

The post Fungi may determine the future of soil carbon appeared first on Smithsonian Insider.

Trees put on weight faster and faster as they grow older, according to a new study in the journal Nature. The finding that most trees’ […]

The post Trees grow faster and store more carbon as they age appeared first on Smithsonian Insider.

On crime scene investigation shows, forensic scientists use remnants of genetic material to solve mysteries in a matter of hours. Researchers at the Smithsonian Environmental […]

The post Environmental “Forensics” Pieces Together Mysterious Plant Invasion appeared first on Smithsonian Insider.

Profound ideas don’t need to be complicated. A simple cube made of aluminum tubing, a centerpiece of a new exhibit “Life in One Cubic Foot,” […]

The post From Rochester to Polynesia, a simple cube unveils Earth’s dazzling biological diversity appeared first on Smithsonian Insider.

In the dark recesses of an underground fungus garden, a Panamanian leaf-cutting ant plucks a tuft of mycelia, the wispy part of the basidiomycete fungus […]

The post Mystery solved? Ants Protect Young From Infection By Cocooning Them in Fungus 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.

Spending time in a beautiful garden can be transformative. In fact, some visitors to the Smithsonian’s Mary Livingston Ripley Garden in Washington D.C. have taken […]

The post Monarch Butterflies Make the Most of the Smithsonian’s Gardens appeared first on Smithsonian Insider.

Caribbean coral reefs have become biologically and economically degraded habitats. The relative weight of the big factors in this ecological catastrophe–pollution, overfishing, warming and ocean […]

The post Coral reefs grow faster, healthier when parrotfish are abundant appeared first on Smithsonian Insider.

Ninety Limosa harlequin frogs (Atelopus limosus) bred in human care are braving the elements of the wild after Smithsonian scientists sent them out into the […]

The post Scientists Release Frogs Wearing Mini Radio Transmitters appeared first on Smithsonian Insider.

A tiny invasive insect from Asia might have an effect on Chesapeake Bay waters. The emerald ash borer is killing millions of ash trees in […]

The post Invasive ash borer found in Smithsonian Environmental Research Center forest; ash deaths may impact Chesapeake waters appeared first on Smithsonian Insider.

White-tailed deer don’t like to eat the invasive plants Japanese stilt grass, garlic mustard or barberry. Native oak seedlings and tulip poplar, on the other […]

The post Too many hungry deer are lowering diversity of native plants in eastern U.S. forests appeared first on Smithsonian Insider.

For many Californians, last year’s wet winter triggered a case of whiplash. After five years of drought, rain from October 2016 to February 2017 broke […]

The post In San Francisco, one wet winter can switch up Bay’s invasive species appeared first on Smithsonian Insider.

This article aims to encourage practitioners, young and seasoned, by enhancing their structure-determination toolboxes with a selection of tips and tricks on recognizing and handling aspects of data collection, structure modelling and refinement, and the interpretation of results.

The crystal structure of vanthoffite, Na6Mg(SO4)4, was redetermined and refined with anisotropic displacement parameters for all atoms. Here, for the first time, we give its detailed description.

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.

This work presents a technique for extracting the detailed shape of peaks with extended, overlapping tails in an X-ray powder diffraction pattern. The application discussed here concerns crystallite size broadening, though the technique can be applied to spectra of any origin and without regard to how the profiles are to be subsequently analyzed. Historically, the extraction of profile shapes has been difficult due to the complexity of determining the background under the peak, resulting in an offset of the low-frequency components of the Fourier transform of the peak known as the `hook' problem. The use of a carefully considered statistical weighting function in a non-linear least-squares fit, followed by summing the residuals from such a fit with the fit itself, allows one to extract the full shape of an isolated peak, without contributions from either the background or adjacent peaks. The extracted shape, consisting of the fit function recombined with the residuals, is not dependent on any specific shape model. The application of this to analysis of microstructure is performed independently of global parametric models, which would reduce the number of refined parameters; therefore the technique requires high-quality data to produce results of interest. The effectiveness of the technique is demonstrated by extraction of Fourier transforms of peaks from two sets of size-broadened materials with two differing pieces of equipment.

Compared with X-rays, electron diffraction faces a crucial challenge: dynamical electron scattering compromises structure solution and its effects can only be modelled in specific cases. Dynamical scattering can be reduced experimentally by decreasing crystal size but not without a penalty, as it also reduces the overall diffracted intensity. In this article it is shown that nanometre-sized crystals from organic pharmaceuticals allow positional refinement of the hydrogen atoms, even whilst ignoring the effects of dynamical scattering during refinement. To boost the very weak diffraction data, a highly sensitive hybrid pixel detector was employed. A general likelihood-based computational approach was also introduced for further reducing the adverse effects of dynamic scattering, which significantly improved model accuracy, even for protein crystal data at substantially lower resolution.

It is shown how to reconstruct the stacking sequence from the pairwise correlation functions between layers in close-packed structures. First, of theoretical interest, the analytical formulation and solution of the problem are presented when the exact pairwise correlation counts are known. In the second part, the practical problem is approached. A simulated annealing procedure is developed to solve the problem using as initial guess approximate solutions from previous treatments. The robustness of the procedure is tested with synthetic data, followed by an experimental example. The developed approach performs robustly over different synthetic and experimental data, comparing favorably with the reported methods.

A new aspherical scattering factor formalism has been implemented in the crystallographic least-squares refinement program SHELXL. The formalism relies on Gaussian functions and can optionally complement the independent atom model to take into account the deformation of electron-density distribution due to chemical bonding and lone pairs. Asphericity contributions were derived from the electron density obtained from quantum-chemical density functional theory computations of suitable model compounds that contain particular chemical environments, as defined by the invariom formalism. Thanks to a new algorithm, invariom assignment for refinement in SHELXL is automated. A suitable parameterization for each chemical environment within the new model was achieved by metaheuristics. Figures of merit, precision and accuracy of crystallographic least-squares refinements improve significantly upon using the new model.

Diffuse scattering is a rich source of information about disorder in crystalline materials, which can be modelled using atomistic techniques such as Monte Carlo and molecular dynamics simulations. Modern X-ray and neutron scattering instruments can rapidly measure large volumes of diffuse-scattering data. Unfortunately, current algorithms for atomistic diffuse-scattering calculations are too slow to model large data sets completely, because the fast Fourier transform (FFT) algorithm has long been considered unsuitable for such calculations [Butler & Welberry (1992). J. Appl. Cryst. 25, 391–399]. Here, a new approach is presented for ultrafast calculation of atomistic diffuse-scattering patterns. It is shown that the FFT can actually be used to perform such calculations rapidly, and that a fast method based on sampling theory can be used to reduce high-frequency noise in the calculations. These algorithms are benchmarked using realistic examples of compositional, magnetic and displacive disorder. They accelerate the calculations by a factor of at least 102, making refinement of atomistic models to large diffuse-scattering volumes practical.

When creating a System Composer architecture model, if the following functions are called with an invalid or missing stereotype, it can cause the model to get corrupted and might lead to a MATLAB crash:

• addComponent
• addPort
• connect

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.

The crystal structure of vanthoffite {hexasodium magnesium tetrakis[sulfate(VI)]}, Na6Mg(SO4)4, was solved in the year 1964 on a synthetic sample [Fischer & Hellner (1964). Acta Cryst. 17, 1613]. Here we report a redetermination of its crystal structure on a mineral sample with improved precision. It was refined in the space group P21/c from a crystal originating from Surtsey, Iceland. The unique Mg (site symmetry overline{1}) and the two S atoms are in usual, only slightly distorted octahedral and tetrahedral coordinations, respectively. The three independent Na atoms are in a distorted octahedral coordination (1×) and distorted 7-coordinations intermediate between a `split octahedron' and a pentagonal bipyramid (2×). [MgO6] coordination polyhedra interchange with one half of the sulfate tetrahedra in <011> chains forming a (100) meshed layer, with dimers formed by edge-sharing [NaO7] polyhedra filling the interchain spaces. The other [NaO7] polyhedra are organized in a parallel layer formed by [010] and [001] chains united through edge sharing and bonds to the remaining half of sulfate groups and to [NaO6] octahedra. The two types of layers interconnect through tight bonding, which explains the lack of morphological characteristics typical of layered structures.

In small-molecule single-crystal structure determination, we now have at our disposal an inspiring range of fantastic diffractometers with better, brighter sources, and faster, more sensitive detectors. Faster and more powerful computers provide integrated tools and software with impressive graphical user interfaces. Yet these tools can lead to the temptation not to check the work thoroughly and one can too easily overlook tell-tale signs that something might be amiss in a structure determination; validation with checkCIF is not always revealing. This article aims to encourage practitioners, young and seasoned, by enhancing their structure-determination toolboxes with a selection tips and tricks on recognizing and handling aspects that one should constantly be aware of. Topics include a pitfall when setting up data collections, the usefulness of reciprocal lattice layer images, processing twinned data, tips for disorder modelling and the use of restraints, ensuring hydrogen atoms are added to a model correctly, validation beyond checkCIF, and the derivation and interpretation of the final results.

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.

An operationally simple and time-efficient approach has been developed for the synthesis of racemic N-substituted 3-(2-aryl-2-oxoeth­yl)-3-hy­droxy­indolin-2-ones by a piperidine-catalysed aldol reaction between aryl methyl ketones and N-alkyl­isatins. These aldol products were used successfully as strategic inter­mediates for the preparation of N-substituted (E)-3-(2-hetaryl-2-oxo­ethyl­idene)indolin-2-ones by a stereoselective dehydration reaction under acidic conditions. The products have all been fully characterized by 1H and 13C NMR spectroscopy, by mass spectrometry and, for a representative selection, by crystal structure analysis. In each of (RS)-1-benzyl-3-hy­droxy-3-[2-(4-meth­oxy­phen­yl)-2-oxoeth­yl]indolin-2-one, C24H21NO4, (Ic), and (RS)-1-benzyl-3-{2-[4-(di­methyl­amino)­phen­yl]-2-oxoeth­yl}-3-hy­droxy­indolin-2-one, C25H24N2O3, (Id), inversion-related pairs of mol­ecules are linked by O—H⋯O hydrogen bonds to form R22(10) rings, which are further linked into chains of rings by a combination of C—H⋯O and C—H⋯π(arene) hydrogen bonds in (Ic) and by C—H⋯π(arene) hydrogen bonds in (Id). The mol­ecules of (RS)-1-benzyl-3-hy­droxy-3-[2-oxo-2-(pyridin-4-yl)eth­yl]indolin-2-one, C22H18N2O3, (Ie), are linked into a three-dimensional framework structure by a combination of O—H⋯N, C—H⋯O and C—H⋯π(arene) hydrogen bonds. (RS)-3-[2-(Benzo[d][1,3]dioxol-5-yl)-2-oxoeth­yl]-1-benzyl-3-hy­droxy­indolin-2-one, C24H19NO5, (If), crystallizes with Z' = 2 in the space group Poverline{1} and the mol­ecules are linked into com­plex sheets by a combination of O—H⋯O, C—H⋯O and C—H⋯π(arene) hydro­gen bonds. In each of (E)-1-benzyl-3-[2-(4-fluoro­phen­yl)-2-oxo­ethyl­idene]indolin-2-one, C23H16FNO2, (IIa), and (E)-1-benzyl-3-[2-oxo-2-(thiophen-2-yl)ethylidene]indolin-2-one, C21H15NO2S, (IIg), the mol­ecules are linked into simple chains by a single C—H⋯O hydrogen bond, while those of (E)-1-benzyl-3-[2-oxo-2-(pyridin-4-yl)ethyl­idene]indolin-2-one, C22H16N2O2, (IIe), are linked by three C—H⋯O hydrogen bonds to form sheets which are further linked into a three-dimensional structure by C—H⋯π(arene) hydrogen bonds. There are no hydrogen bonds in the structures of either (E)-1-benzyl-3-[2-(4-meth­oxy­phen­yl)-2-oxo­ethyl­idene]indolin-2-one, C24H19NO3, (IIc), or (E)-1-benzyl-5-chloro-3-[2-(4-chloro­phen­yl)-2-oxo­ethyl­idene]indolin-2-one, C23H15Cl2NO2, (IIh), but the mol­ecules of (IIh) are linked into chains of π-stacked dimers by a combination of C—Cl⋯π(arene) and aromatic π–π stacking inter­actions.

The backdrop of the stage with the Oscar Award is seen onstage during the 84th Academy Awards announcement held at the Academy of Motion Picture Arts and Sciences Samuel Goldwyn Theater on Jan. 24, 2012 in Los Angeles.; Credit: Kevin Winter/Getty Images

The Academy Awards have made history with breakthroughs for minorities in the past — but with this year's nominations, observers are noting how white the Oscars are, with no actors of color nominated in any of this year's acting categories.

It marks the least diverse nominations since 1998. People have been speaking out about this disconnect, with films like "Selma" being shut out of the acting nominations (though it did pick up a Best Picture nomination).

This content is from Southern California Public Radio. View the original story at SCPR.org.

File: (L-R) "The Sarah Silverman Program" writer Harris Wittels, comedian Sarah Silverman, executive producer/head writer Dan Sterling and actress Laura Silverman, arrive at Comedy Central's Emmy Awards party at the STK restaurant Sept. 21, 2008 in Los Angeles.; Credit: Ethan Miller/Getty Images

Harris Wittels, a comedy writer who worked on "Parks & Recreation," has died at 30, the Los Angeles Police Department's Jane Kim tells KPCC.

Wittels was discovered by his assistant around 12 p.m., Kim said, and was already dead. Kim said that Wittels' death was a possible overdose, but that the Coroner's Office would determine the cause of death. Wittels had attended drug rehab twice.

Comedy Central, where Wittels worked on "The Sarah Silverman Program" and "Secret Girlfriend," confirmed Wittels' death, as did the comedy show he appeared at Wednesday night.

Comedy Central tweet

Meltdown Show tweet

Wittels was also well known for his @Humblebrag Twitter account and later book, helping to popularize the idea online of the false modesty of bragging while trying not to look like you're bragging.

Wittels had spoken about his struggles with addiction in places including Pete Holmes's podcast "You Made It Weird" in a November episode.

"I just really stopped caring about my life," Wittels said on "You Made It Weird," explaining how he got into doing drugs. "I just really started to think, well, if I'm only here for 80 years, then who cares if I spend it high or not?"

Wittels received his first big break when Sarah Silverman saw him performing comedy and gave him a job writing for her Comedy Central show.

Wittels also wrote for HBO's "Eastbound & Down," several MTV awards shows and the American Music Awards. He had a recurring role on "Parks & Recreation" and was a regular guest on the "Comedy Bang Bang" podcast.

Comedians, actors and fans mourned Wittels' death online.

Harris Wittels Storify

See Wittels in a scene from "Parks & Recreation":

Wittels on Parks & Recreation

Listen to Wittels on "Comedy Bang Bang":

Wittels on Comedy Bang Bang

This story has been updated.

This content is from Southern California Public Radio. View the original story at SCPR.org.

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.

The Debye scattering equation (DSE) is generalized and augmented in order to account for moderate texture effects, yielding the differential cross section as a function of atomic coordinates and texture coefficients subject to symmetry constraints. Implications for the evaluation of the pair distribution function (PDF) as a direct transform of powder diffraction data from textured samples are also discussed.