Chirality and accurate structure models by exploiting dynamical effects in continuous-rotation 3D ED data

Dynamical diffraction effects are usually considered a nuisance for structure analysis from continuous-rotation 3D electron diffraction (3D ED) data like cRED and MicroED. Here we demonstrate that by accounting for these effects during the structure refinement, significantly improved models can be obtained in terms of accuracy and reliability with up to four-fold reduction of the noise level in difference Fourier maps in comparison to the standard structure determination routines that ignore dynamical diffraction. As dynamical diffraction effects break the inversion symmetry of the diffraction, they allow a quick, easy, and reliable determination of the absolute structure of chiral crystals.

Determination of Absolute Structure of Chiral Crystals Using Three-Wave X-ray Diffraction

We propose a new method to determine the absolute structure of chiral crystals, which is based on the chiral asymmetry of multiple scattering diffraction. It manifests as a difference in the azimuthal dependence of the forbidden Bragg reflection intensity measured with left and right circularly polarized X-ray beams. Contrary to the existing ones, the suggested method does not use X-ray anomalous dispersion. The difference between the Renninger scans with circularly polarized X-rays has been experimentally demonstrated for the 001 reflection intensities in the right- and left-handed quartz single crystals. A Jmulti-based code on model-independent three-wave-diffraction approach has been developed for quantitative description of our experimental results. The proposed method can be applied to various structures including opaque, organic and monoatomic crystals, even with only light elements. To determine the type of isomer, the Renninger plot of a single forbidden reflection is sufficient.

Memorial Issue Dedicated to Dr. Howard D. Flack: The Man behind the Flack Parameter

This Special Issue of Chemistry is dedicated to Dr. Howard D. Flack (1943–2017), a renowned crystallographer who transformed the way in which, by using single crystal X-ray diffraction, we are able to determine the absolute structure of a crystalline material, and thereby determine the absolute configuration of molecular species within the material [...]

Unusual derivatives from Hypericum scabrum

Three new compounds (1–3) with unusual skeletons were isolated from the n-hexane extract of the air-dried aerial parts of Hypericum scabrum. Compound 1 represents the first example of an esterified polycyclic polyprenylated acylphloroglucinol that features a unique tricyclo-[4.3.1.11,4]-undecane skeleton. Compound 2 is a fairly simple MPAP, but with an unexpected cycloheptane ring decorated with prenyl substituents, and compound 3 has an unusual 5,5-spiroketal lactone core. Their structures were determined by extensive spectroscopic and spectrometric techniques (1D and 2D NMR, HRESI-TOFMS). Absolute configurations were established by ECD calculations, and the absolute structure of 2 was confirmed by a single crystal determination. Plausible biogenetic pathways of compounds 1–3 were also proposed. The in vitro antiprotozoal activity of the compounds against Trypanosoma brucei rhodesiense and Plasmodium falciparum and cytotoxicity against rat myoblast (L6) cells were determined. Compound 1 showed a moderate activity against T. brucei and P. falciparum, with IC50 values of 3.07 and 2.25 μM, respectively.

On English Adverbials: An English Teacher’s View

For Grade two students in Senior High School, what is of vital importance is that students establish clear grammar networks at least after the second term to prepare themselves well for the first-round review of the third year and the following College Entrance Examination. With the scattered language points such as “with complex structure”, “participles used as adverbials”, or “absolute structure” learned by students in a gradual style, it is essential for them to clear out a main thinking path or thinking framework to make connections between knowledge points. The author finds in her years of teaching duration the relations between English adverbials, making it easier for students to know the know-how of learning English in a much scientific and reasonable way. Here are the findings.

Automatic Harvested Crop Protector from Rain

The fundamental topic of this task which is displayed in the paper is that to keep the yields from the overwhelming precipitation. The farmer is the foundation of Indian economy. They drudge and accomplishes difficult work to deliver the yield by enduring a ton toward the end for drying the harvest because of unforeseen downpours. These components like startling downpours harm the harvest when it is dried before selling, which will totally crush the yield or make the yield second grade. To stay away from such conditions “HARVESTED CROP PROTECTOR FROM RAIN” is to be created. At the present time, propose a system where the storms are recognized therefore to guarantee the gather by wrapping housetop top on the yield by using DC motors, Rain sensor and Arduino uno load up. If it pouring the sensor will distinguishes and offers intimation to the Arduino. So, when the sensor is ‘ON,’ it will offer recommendation to the controller, GSM and it will show to the DC motor and it will subsequently open the housetop. At the present time, housetop is open thusly when the sensor is ‘ON.’ This absolute structure can be managed truly. If there is any issue with opening the housetop thusly, it is blend thought in with controlling movement done through Arduino. GSM is reporting the conditions in the field through SMS to the mobile phone.