The Crystal and Molecular Structure of a Polymorph and a Pseudo-Polymorph of Droperidol

Abstract Crystals of two crystal modifications of droperidol: a hemihydrate (1) and the z polymorph (2), have been isolated and their structure determined using X-ray diffraction methods. Droperidol hemihydrate crystallized in the triclinic space group P − 1, with unit cell parameters a = 6.2842(15), b = 10.1473(8), c = 16.1850(2) ?; α = 102.554(9); β = 91.917(14); γ = 99.316(12)°; V = 991.6(3) ?³, and Z = 2. The droperidol z polymorph crystallized in the monoclinic space group P2₁/c, with unit cell parameters a = 20.0406(8), b = 7.4955(4), c = 12.9733(5) ?; β = 98.089(2)°; V = 1929.39(15) ?³, and Z = 4. In 1 and 2 two molecules of droperidol are joined by two N–H···O hydrogen bonds. The structure of 1 shows a possible additional hydrogen bond linking the two droperidol molecules via the water molecule. Graphical Abstract The crystal and molecular structure of a polymorph and a pseudo-polymorph of droperidol A. Actins, R. Arajs, S. Belakovs, L. Orola, and M. V. Veidis Crystals of two crystal modifications of droperidol: a hemihydrate and the z polymorph have been isolated and their structure determined using single crystal X-ray diffraction methods. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

A Binary System of a Swallow-Tailed and a Double Swallow-Tailed Compound

The geometrical anisotropy in the shape of swallow-tailed ST liquid crystalline molecules results in an extremely strong tendency of an antiparallel order in the short range. Dielectric measurements on a binary system of a ST and a double ST compound show that even at a mole fraction of 0.5 this effect can be observed. The strong deviations from the statistical distribution of the directions of the molecular long axis is caused by the asymmetric repulsive forces and the dipole-dipole interaction.     

OD Structures, — a Game and a Bit More

The notion of OD structures consisting of layers is explained, and visualization of its main features facilitated by a simple game: the player is asked to stack prefabricated layers periodic in 2 dimensions, which are all of the same kind or of a small number of different kinds, in accordance with some rules which correspond to the vicinity condition (VC). As shown, important features of the sequences of layers depend only on their symmetry (i.e. layer groups) and on geometrical features of any of the kinds of pairs, especially the layer group of any of the pairs. Table 1 shows that OD crystals consisting of layers occur amongst the most diverse chemical substances. In Tables 2 and 3 some examples of OD crystals with a variety of relations between crystallochemical entities and OD layers are listed. In the Appendix and Table 4 new and simplified formulae for the number Z_v'(v) of possible positions of a certain layer L_v′ relative to the fixed position of its predecessor (or successor) L_v are given.     

Comparative Study of Mixed Monolayers of a Calixarene with a Fatty Acid and a Non-Amphiphilic Nematic Liquid Crystal

Abstract

Many nematic liquid crystals (NLCs) lack a polar headgroup and thus are not able to form stable monolayers at the air/water (a/w) interface. A way to obtain monomolecular films of these compounds is to incorporate them into host monolayers of amphiphilic molecules. We report a comparative investigation of mixed films of Calix[4]resorcinarene O-octacarboxymethylated (CRO) with the non-amphiphilic NLC MBBA and with the amphiphilic stearic acid (SA). The comparative study is useful for a better understanding of the characteristics of the CRO-MBBA mixed films. Surface-pressure and surface-potential measurements on the monolayers at a/w interface, as well as ellipsometric and spectroscopic measurements on transferred Langmuir-Blodgett (LB) films, confirm that MBBA is additively incorporated into CRO films.     

Crystal and molecular structure of a hexaazamacrocycle

The crystal and molecular structure of the hexaazamacrocycle C₂₄H₁₄N₆ has been determined from X-ray diffractometer data. The crystals are monoclinic, space groupP2₁/c witha = 4.416(1),b = 9.972(4),c = 18.955(12) Å, = 95.48(4) °, andZ = 2. The structure was derived from 536 reflections using direct and Fourier methods and was refined by least squares toR = 0.038. The polar molecules form stacks along thea axis with an inclination of 68 ° and an interplanar distance of 3.32 Å. The size of the central hole of the molecule is defined by the diagonal distances N(2) N(2) = 3.681(10) and N(3) N(3) = 3.771(9) Å of theo-phenanthroline nitrogens. This is too small to accommodate Pd²⁺ or Pt²⁺ in the hole.     

Aging and flow in a complex fluid

The comprehension of the physical mechanism governing the interaction between aging dynamics and shear flow is crucial to both elucidating the nature of slow dynamics in soft materials and controlling their complex rheological behavior. Dynamic light scattering is used to probe the relaxation of the intermediate scattering function of an aging colloidal suspension and the effect of shear on the non-equilibrium structural dynamics is investigated during various protocols of applied shear. The shear flow influences significantly the aging dynamics as soon as structural relaxation enters the timescale set by the inverse shear rate. Aging is strongly reduced in this shear dominated regime, while, for a fixed system age, the average structural relaxation time scales as the inverse shear rate. The fast component in the relaxation function, usually interpreted as the single particle diffusion, shows a cross-over behavior as well, suggesting a close link between slow and fast dynamics. Shear rejuvenation of old samples is also observed leading to a faster relaxation dynamics while the subsequent aging proceeds in an apparently new regime.     

Combination of a reflectometer and a nonmagnetic waveguide for experiments with polarized neutron microbeams

Neutron waveguides are three-layer thin-film structures which transform part of a collimated (with an angular divergence of 0.01°) and relatively wide (0.1 mm) incident neutron beam into a narrow (0.1 μm wide) and divergent (0.1°) beam at the output. This submicron beam (which cannot be obtained using conventional focusing elements) is promising for studying nanostructures. We propose a combination of a polarized-neutron reflectometer and a nonmagnetic (independent of the neutron spin) waveguide for experiments employing polarized neutron beams with a submicron spatial resolution. This scheme can be applied, for example, for position-sensitive studies of magnetic nanostructures.     

Aggregation and solvation of a lithium aryloxide

{Li[OC₆H₃-2,6-(^tBu)₂]THF}₂, synthesized from phenol and LiH, is shown by X-ray crystallography to exist in the solid as a centrosymmetric dimer with two bridging phenoxides. Terminal THF ligands (envelope conformation) complete trigonal planar coordination about Li. The THF ligand plane lies in the Li₂(-O)₂ plane, while the phenyl ligands are perpendicular to this same Li₂O₂ plane. This explains the unusual¹H NMR chemical shifts of the THF ligand. THF binds to Li as a dipole rather than using one of the two ether lone pairs. Crystallographic data (–160°C):a=18.799(3) Å,b=18.758(6),c=15.697(5), andZ=4 in space groupPbca (no. 61). The final quality indices areR(F)=6.2% andR _w (F)=5.9% for 1535 unique data.     

Numerical simulation of a low- and a high-electric-field photocurrent decay in a-Si:H

We report a numerical simulation of the photocurrent decay (PCD), from the steady state, in two different structure configurations based on the a-Si:H. The standard DOS of the a-Si:H is used. The high-electric-field PCD is considered in a structure configuration based on a metal/a-Si:H junction. Poisson’s and the two continuity equations are numerically solved in a one-dimensional space to calculate the current density. Two different boundary conditions of the a-Si:H film are considered. The low electric field PCD, which may occurs in a coplanar configuration, is calculated from the solution of a system of two non linear coupled rate equations which govern the free carriers concentrations and the different charges on the localized states in the gap. The calculated PCD versus time curves, for the two configurations, show a shoulder around 1 μs which separate two main regions. We can see that the initial current decay is dominated by the electron emission from the conduction-band tail and the recombination via the dangling bonds states. The second current decay is mainly due to the electrons emission from the dangling bonds. We show also that the PCD curve tends towards the PCD of the coplanar configuration when the electric field decreases.     

Three-dimensional global analysis of thermal stress and dislocations in a silicon ingot during a unidirectional solidification process with a square crucible

A three-dimensional global model was used to obtain the solution of a thermal field within the entire furnace during a unidirectional solidification process of multicrystalline silicon with a square crucible. Then the thermal stress distribution in the silicon ingot was solved. Based on the solution of thermal stress, relaxation of stress and multiplication of dislocations were performed by using the Haasen–Alexander–Sumino model (HAS model). The influence of crucible constraint on stress levels and dislocations was investigated. It was found that the crucible constraint had significant influence on the thermal stresses and dislocations in the ingot. The results indicated that it is important to reduce the crucible constraint in order to relax thermal stresses and reduce dislocations in a silicon ingot during the solidification process.     

Synthesis and Crystal Structure of a Decamethyleuropocene Complex Supported by a “Clamshell” Ligand

Abstract  

The coordination of decamethyleuropocene to a “clamshell” 1,2-bis(imino)acenaphthene (BIAN) ligand is accompanied by a one-electron redox process. The crystal structure of the Eu³⁺ product has been determined. The complex crystallizes in the triclinic space group P-1, with a = 12.065(2), b = 15.391(3), c = 17.266(4) ?, α = 73.71, β = 73.93(3), γ = 81.40(3)°, V = 2948.3(10) ?³ and Z = 2. The pyridine moiety of the clamshell ligand is not coordinated to the Eu³⁺ center.     

Electro-Optic Effect in Thin Films of a Dielectric and a Ferroelectric with Subwavelength Aluminum Grating

The electro-optic effect in three nanoscale heterostructures, in each of which a thin layer of dielectric or ferroelectric material is inserted between two planar metal electrodes, has been studied. Each structure has one aluminum layer, containing a subwavelength grating with a period of 400 nm, contacting with either the glass substrate or air. The light transmission spectra of structures with subwavelength grating contain characteristic plasmon dips. Short external-voltage pulses affect the change in the refractive index of the corresponding active layer. Significant values of these changes may be useful for designing optical modulators.     

Magnetic properties of a basalt glass and glass-ceramics

Mössbauer, ESR and magnetization measurements have been carried out on a basalt glass heat-treated at different temperatures (600, 650, 700, 800 and 900°C for 8 h). The as-annealed glass and the above five samples showed two-doublet Mössbauer spectra, while the last two samples also showed a six line magnetic hyperfine pattern at 300 K. At 4 K, the last four samples showed magnetic hyperfine patterns, while the as-annealed glass showed that there was already short range magnetic ordering present. High field Mössbauer data at 4 K showed that the surface spins are canted. The minimum quadrupole splitting and the maximum isomer shift around 700°C are related to the improved symmetry of the magnetite lattice. ESR spectra showed paramagnetic resonances at g = 4.3 and g = 2.0 for the first two samples, while the last four samples showed superparamagnetic resonance centred around g = 2.0 at 300 K. At lower temperatures, the 650 and 700°C samples showed ferrimagnetic resonance. Magnetization curves against H/T superpose well both at 300 and 77 K, showing the typical superparamagnetic behaviour of the small magnetite particles. The saturation magnetization (at 270 K) showed a sharp change around 700°C, showing the formation of magnetite. The magnetic structure of the small magnetite particles are discussed in terms of the above results.     

Spectroscopic and dielectric properties of a lithia-containing glass

Glass of the composition 65SiO₂-20CaO-15Li₂O (mol %) was prepared and subjected to heat treatment. The obtained samples were characterized before and after heat treatment by DTA, TG, XRD, SEM, IR and dielectric spectroscopy. DTA showed an endothermic peak at 954 °C, accompanied by a pronounced change in the microstructure, as revealed by SEM. XRD showed that metasilicate predominates on heat treatment at 726 °C, while on heat treatment at 726 °C, then at 954 °C, disilicate crystallizes as the main phase. The IR spectra of the heat-treated glasses revealed that the vibrations of O-H groups are drastically decreased, while those due to non-bridging oxygens Si-O⁻ are increased. The dielectric constant (ε′), the loss tangent (tan δ) and the ac conductivity (σ_ac) for the prepared glasses were investigated before and after heat treatment over a moderately wide range of frequency and temperature. The activation energy of the dielectric relaxation process was found to depend on the techniques of sample preparation. A drop of dielectric constant values was observed for the heat-treated sample, which can be attributed to the ordering of the induced crystalline phases. The conductivity behavior suggests a hopping mechanism responsible for conduction.     

一种多喷淋头式MOCVD反应器的设计与数值模拟

提出了一种多喷淋头式MOCVD反应器.针对新型反应器,对GaN生长的MOCVD过程进行了数值模拟,模拟考虑了热辐射和化学反应,计算了反应器内流场、温场和浓度场,导流(筒)壁面的寄生沉积以及GaN生长速率,并分析了反应室几何因素对生长均匀性的影响.模拟结果显示,衬底表面大部分区域具有均匀的温场和良好的滞止流.通过对浓度场和GaN生长速率的分析,得出MMGa是薄膜生长的主要反应前体.通过对反应器高度H、导流筒与托盘间距h、导流筒半径R等参数的优化,给出了提高薄膜生长速率和均匀性的条件.     

Synthesis and Crystal Structure of a Chalcone Derivative

Crystallography Reports - (2E)-3-(anthrance-9-yl)-1-(3,4-dichlorophenyl)prop-2-en-1-one [C23H14OCl2] is synthesized and its crystal structure is determined by single X-ray diffraction. There exist...     

Generation and intermolecular trapping of a cage-annulated cycloalkylidenecarbene

Base-promoted reaction of 11-methylenepentacyclo[5.4.0.0^2,6.0^3,10.0^{5, 9}]undecan-8-one (5) with diethyl diazomethylphosphonate when performed in the presence of excess cyclohexene, resulted in the formation of the corresponding cycloalkylidenecarbene, 6, which subsequently was trapped in situ to afford 8-methylene-11-(7-bicyclo[4.1.0]heptylidene)pentacyclo-[5.4.0.0^{2, 6}.0^{3, 10}.0^{5, 9}]undecane (7, obtained in 44% yield as a mixture of exo, endo isomers). Subsequent reaction of 7 with dichlorocarbene (generated under phase transfer catalytic conditions) produced the corresponding mono- and di-:CCl₂ adducts [i.e., 8 (64% yield) and 9 (5% yield), respectively]. The structure of 9 was established unequivocally via application of single crystal X-ray analysis: Triclinic, P1¯, a = 6.276(2), b = 8.700(2), c = 18.550(3) Å, = 76.52(3), = 87.59(3), = 70.88(4)° Z = 2; D _calc 1.486 g cm^–3.