When a mosquito lands and begins to feed, the saliva it deposits in the skin stops blood from coagulating and makes the bite itch. A […]

The post The beautiful and bizarre treehopper appeared first on Smithsonian Insider.

Hidden in plain sight–that’s how researchers describe their discovery of a new genus of large forest tree commonly found, yet previously scientifically unknown, in the […]

The post Remarkable new tree species was “hidden in plain sight” in the Andes 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.

Millions, if not billions, of specimens reside in the world’s natural history collections, but most of these have not been carefully studied, or even looked […]

The post Using digitized Botany specimens, AI excels in simple curatorial tasks appeared first on Smithsonian Insider.

A new paper published in Behavioral Ecology finds that some ant colonies defend more gallantly than others, revealing that colonies themselves may have personalities. Trees that have […]

The post Ant colony ‘personality’ may play role in survival of its host plant 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.

Life and the Earth have always evolved together. When it opens on June 8, 2019, the David H. Koch Hall of Fossils — Deep Time […]

The post Sneak Peek: David H. Koch Hall of Fossils appeared first on Smithsonian Insider.

Each year from summer into fall, ornamental crape myrtle trees in the southern and central U.S. lay out a visual feast of vibrant flowers in […]

The post Crape myrtle trees aren’t native to the US, but hungry native birds still find them tasty appeared first on Smithsonian Insider.

The addition of tert-butyl hydro­peroxide (tBuOOH) to two MnII complexes, differing by a small synthetic alteration from an ethyl to a propyl linker in the ligand scaffold, results in the formation of the high-valent bis-oxo complexes, {[MnIV{N4(6-Me-DPEN)}]2(μ-O)2}2+ (1) and {[MnIV{N4(6-Me-DPPN)}]2(μ-O)2}2+ (2).

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.

In the structure of the title salt, second-order Jahn–Teller distortion of the coordination octa­hedra around V ions is reflected by coexistence of short V—O bonds and trans-positioned long V—F bonds, with four equatorial V—F distances being inter­mediate in magnitude. Hydrogen bonding of the anions is restricted to F-atom acceptors only, with particularly strong N–H⋯F inter­actions [N⋯F = 2.5072 (15) Å] established by axial and cis-positioned equatorial F atoms.

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.

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.

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.

The title complex, Cu(L)2 or [Cu(C15HF10O2)2], comprising one copper ion and two fully fluorinated ligands (L−), was crystallized with 3,4-ethyl­ene­dioxy­thio­phene (EDOT, C6H6O2S) as a guest mol­ecule to give in a di­chloro­methane solution a unique co-crystal, Cu(L)2·3C6H6O2S.

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.

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.

This work considers the scaling properties characterizing the hyperuniformity (or anti-hyperuniformity) of long-wavelength fluctuations in a broad class of one-dimensional substitution tilings. A simple argument is presented which predicts the exponent α governing the scaling of Fourier intensities at small wavenumbers, tilings with α > 0 being hyperuniform, and numerical computations confirm that the predictions are accurate for quasiperiodic tilings, tilings with singular continuous spectra and limit-periodic tilings. Quasiperiodic or singular continuous cases can be constructed with α arbitrarily close to any given value between −1 and 3. Limit-periodic tilings can be constructed with α between −1 and 1 or with Fourier intensities that approach zero faster than any power law.

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):
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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

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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When the Signal Editor is saving data, the indicator that the save is occurring does not appear.  You might notice a delay when saving large data files.This bug exists in the following release(s):
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The Open Banking Report 2019 clarifies the role of key key-players in a post-September 14th world and assesses how the landscape has shifted within Europe and beyond.

Individual white paper containing all the latest updates to the Open Banking Global State of Play. Research conducted by The Paypers and Innopay

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.

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.

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.

In the structure of the title salt, (C7H12N6)[VOF5], second-order Jahn–Teller distortion of the coordination octahedra around V ions is reflected by coexistence of short V—O bonds [1.5767 (12) Å] and trans-positioned long V—F bonds [2.0981 (9) Å], with four equatorial V—F distances being intermediate in magnitude [1.7977 (9)–1.8913 (9) Å]. Hydrogen bonding of the anions is restricted to F-atom acceptors only, with particularly strong N–H...F interactions [N...F = 2.5072 (15) Å] established by axial and cis-positioned equatorial F atoms. Hirshfeld surface analysis indicates that the most important interactions are overwhelmingly H...F/F...H, accounting for 74.4 and 36.8% of the contacts for the individual anions and cations, respectively. Weak CH...F and CH...N bonds are essential for generation of three-dimensional structure.

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.

Experimental electron-density studies based on high-resolution diffraction experiments allow halogen bonds between heavy halogens to be classified. The topological properties of the electron density in Cl⋯Cl contacts vary smoothly as a function of the inter­action distance. The situation is less straightforward for halogen bonds between iodine and small electronegative nucleophiles, such as nitro­gen or oxygen, where the electron density in the bond critical point does not simply increase for shorter distances. The number of successful charge–density studies involving iodine is small, but at least individual examples for three cases have been observed. (a) Very short halogen bonds between electron-rich nucleophiles and heavy halogen atoms resemble three-centre–four-electron bonds, with a rather symmetric heavy halogen and without an appreciable σ hole. (b) For a narrow inter­mediate range of halogen bonds, the asymmetric electronic situation for the heavy halogen with a pronounced σ hole leads to rather low electron density in the (3,−1) critical point of the halogen bond; the properties of this bond critical point cannot fully describe the nature of the associated inter­action. (c) For longer and presumably weaker contacts, the electron density in the halogen bond critical point is only to a minor extent reduced by the presence of the σ hole and hence may be higher than in the aforementioned case. In addition to the electron density and its derived properties, the halogen–carbon bond distance opposite to the σ hole and the Raman frequency for the associated vibration emerge as alternative criteria to gauge the halogen-bond strength. We find exceptionally long C—I distances for tetra­fluoro­diiodo­benzene molecules in cocrystals with short halogen bonds and a significant red shift for their Raman vibrations.

The title com­pound, tetra­ethyl­ammonium tetra­thio­rhenate, [(C2H5)4N][ReS4], has, at room temperature, a disordered structure in the space group P63mc (Z = 2, α-phase). A phase transition to the monoclinic space group P21 (Z = 2, γ-phase) at 285 K leads to a pseudo-merohedral twin. The high deviation from the hexa­gonal metric causes split reflections. However, the different orientations could not be separated, but were integrated using a large integration box. Rapid cooling to 110–170 K produces a metastable β-phase (P63, Z = 18) in addition to the γ-phase. All crystals of the β-phase are contaminated with the γ-phase. Additionally, the crystals of the β-phase are merohedrally twinned. In contrast to the α-phase, the β- and γ-phases do not show disorder.

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 positional change of nitro­gen-7 of the RNA constituent guanosine to the bridgehead position-5 leads to the base-modified nucleoside 5-aza-7-de­aza­guanosine. Contrary to guanosine, this mol­ecule cannot form Hoogsteen base pairs and the Watson–Crick proton donor site N3—H becomes a proton-acceptor site. This causes changes in nucleobase recognition in nucleic acids and has been used to construct stable `all-purine' DNA and DNA with silver-mediated base pairs. The present work reports the single-crystal X-ray structure of 7-iodo-5-aza-7-de­aza­guanosine, C10H12IN5O5 (1). The iodinated nucleoside shows an anti conformation at the glycosylic bond and an N conformation (O4'-endo) for the ribose moiety, with an anti­periplanar orientation of the 5'-hy­droxy group. Crystal packing is controlled by inter­actions between nucleobase and sugar moieties. The 7-iodo substituent forms a contact to oxygen-2' of the ribose moiety. Self-pairing of the nucleobases does not take place. A Hirshfeld surface analysis of 1 highlights the contacts of the nucleobase and sugar moiety (O—H⋯O and N—H⋯O). The concept of pK-value differences to evaluate base-pair stability was applied to purine–purine base pairing and stable base pairs were predicted for the construction of `all-purine' RNA. Furthermore, the 7-iodo substituent of 1 was functionalized with benzo­furan to detect motional constraints by fluorescence spectroscopy.

A large The Actor statue is placed on stage during 21st Annual SAG Awards Behind The Scenes At The Shrine Auditorium Jan. 23, 2015 in Los Angeles.; Credit: Kevork Djansezian/Getty Images

Click here for KPCC's Awards Tracker

This Sunday's Screen Actors Guild Awards aren't as high profile as the Academy Awards, or even the Golden Globes, but they serve as one of the best predictors of who's going to take home a gold statue come Oscar night. Here's why.

Who votes for the SAG Awards?

SAG Award nominees are chosen by a committee of about 2,100 of the guild's members, according to awards news site Gold Derby. Then, all of the 111,228 members of the Guild have the chance to vote for their picks.

Meanwhile, the acting nominees for the Academy Awards are chosen by the 1,100 members in the Academy's actors branch, before being voted on by the Academy's full 5,700 members. Those actors are all part of SAG, so you're likely to see a strong correlation most years between the awards, particularly in the acting category.

How often do the SAG Awards predict the Oscar winners?

The SAG Awards have proven to be the best Oscar predictor in the acting category of any other major awards season prize since they began in 1995, both in nominations and winners. Of the 20 nominations and four winners from each shows, the overlap between the SAG Awards (aka "the Actors") and the Academy Awards in the last few years:

• 2009: 18 nominations; 3 winners
• 2010: 19 nominations; all 4 winners
• 2011: 17 nominations; all 4 winners
• 2012: 16 nominations; 3 winners
• 2013: 15 nominations; 3 winners
• 2014: 14 nominations; all 4 winners

This year, 17 nominees crossed over between the awards shows, with the Oscars matching up on all five nominations for best supporting actor and four of the five nominations in the other three acting categories.

Where have the SAG Awards differed from the Oscars?

SAG voters have lined up with the Academy on Best Actor 16 out of 20 times. The last time they differed from the Oscars was 2003, when Johnny Depp won at the SAG Awards for "Pirates of the Caribbean: Curse of the Black Pearl" before Sean Penn took the statue home at the Oscars for "Mystic River."

For Best Actress, SAG last split from Oscar in 2011, going with Viola Davis for "The Help" over eventual Oscar winner Meryl Streep for "The Iron Lady." They've matched up 14 out of 20 years.

In the supporting categories, the SAG Awards haven't fared as well. They went 12 for 20 in Best Supporting Actor, and 13 for 20 in Best Supporting Actress. That one also has an asterisk — one of those was a tie, so if you don't count that one, they're also only 12 for 20.

What does this all mean for the Oscars?

The SAG Awards remain the ones to watch when it comes to the acting awards — though their Best Ensemble category, the SAG Awards version of Best Picture, doesn't have a particularly strong correlation to the Oscars Best Picture winner. (For that, you'll want to watch for the Producers Guild Awards.)

We're tracking awards season and what experts are predicting; see KPCC's Awards Tracker below or click here to see the full page. You can watch the Screen Actors Guild Awards this Sunday at 5 p.m. Pacific, 8 p.m. Eastern on both TBS and TNT.

Disclosure: Mike Roe, along with other members of KPCC's staff, are members of the Screen Actors Guild as part of their employment with KPCC.

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

Entangled embedded periodic nets and crystal frameworks are defined, along with their dimension type, homogeneity type, adjacency depth and periodic isotopy type.

Physical quantities in arbitrary dimensional space can be classified into 41 types using three antisymmetries within the framework of Clifford algebra.

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.