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The post Newly named, Hawaiian tree species already critically endangered appeared first on Smithsonian Insider.

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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.

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.

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):
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In certain scenarios, a Subsystem Reference block changes its position. It can happen during: 

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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.

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.

An error in an equation in the paper by Song et al. [Acta Cryst. (2019), C75, 1353–1358] is corrected.

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.

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.