New liquid crystalline di- and tetra-acrylates for network formation

New liquid crystalline diacrylates and tetra-acrylates containing four to six aromatic rings were synthesized and characterized, and their mesophase behaviour was investigated. They are designed to be used in combination with chiral molecules to form cholesteric mesophases which can be crosslinked by photopolymerization. The acrylates presented exhibit broad mesophase ranges since mesogenic moieties longer than three are employed. Most diacrylates show no isotropization, due to premature thermal polymerization above 180°C. Additionally, liquid crystalline dipropionates were synthesized as reference compounds which cannot be crosslinked, and selected examples of these exhibit isotropization temperatures as high as 238°C prior to thermal degradation. Substituents at the mesogenic moiety have a great influence on the mesophase characteristics. Bulky substituents such as the tert-butyl group, induce a nematic mesophase, whereas compounds with small substituents (e.g. OCH3) or unsubstituted molecules also exhibit smectic phases. Tetra-acrylates with unsubstituted and substituted mesogenic units feature nematic mesophases only as a result of the additional spacers attached. Here isotropization was observed without polymerization at temperatures around 120-160°C.     

Charge qubit purification by an electronic feedback loop

We propose the manipulation of an isolated qubit by a simple instantaneous closed-loop feedback scheme in which a time-dependent electronic detector current is directly back-coupled into qubit parameters. As a specific detector model, we employ a capacitively coupled single-electron transistor. We demonstrate the stabilization of pure delocalized qubit states above a critical detector-qubit coupling. This electronic purification is independent of the initial qubit state and is accomplished after few electron jumps through the detector. Our simple scheme can be used for the efficient and robust initialization of solid-state qubits in quantum computational algorithms at arbitrary temperatures.     

Pyroxene‐type compounds NaM3+Ge2O6, with M = Ga,Mn, Sc and In

The four title compounds, namely sodium gallium germanate, NaGaGe₂O₆, sodium manganese vanadate germanate, NaMnV_0.1Ge_1.9O₆, sodium scandium germanate, NaScGe₂O₆, and sodium indium germanate, NaInGe₂O₆, adopt the high‐temperature structure of the pyroxene‐type chain germanates, with monoclinic symmetry and space group C2/c. The lattice parameters, the individual and average bond lengths involving M1, and the distortion parameters scale well with the ionic radius of the M1 cation. NaGaGe₂O₆ has more distorted M1 sites and more extended tetrahedral chains than NaInGe₂O₆, in which a high degree of kinking is required to maintain the connection between the octahedral and tetrahedral building units of the pyroxene structure. An exceptional case is NaMnGe₂O₆, in which the strong Jahn–Teller effect of Mn³⁺ results in more distorted octahedral sites than expected according to linear extrapolation from the other NaM³⁺Ge₂O₆ pyroxenes. In contrast with the literature, minor incorporations of V⁵⁺ in the tetrahedral site and a corresponding reduction of Mn³⁺ to Mn²⁺ in the octahedral sites in the present sample lower the Jahn–Teller distortion and stabilize the Mn‐bearing pyroxene, even allowing its synthesis at ambient pressure.     

Defect structure and magnetic moments in the β-phases of CoAl and CoGa

The atomic magnetic susceptibility χ_A of homogeneous β-phases of Co?Al and Co?Ga has been measured in the temperature range from 10 to 300°K. Below 50 at.% Co, χ_A can be described adequately by a Curie law, and for higher Co concentrations a Curie-Weiss law is obeyed. The results are interpreted in terms of a defect structure based on the antistructure cobalt concentration. This treatment is shown to be superior to previous models in that it is now possible to treat the whole range of homogeneous β-phase alloys with a single model. The relationship between the effective magneton number and the Co antistructure atom concentration is linear for both the Co?Al and Co?Ga β-phase above the stoichiometric ratio of Co.     

Influence of ethanol on cannabinoid pharmacokinetic parameters in chronic users

Cannabis is not only the most widely used illicit drug worldwide but is also regularly consumed along with ethanol. In previous studies, it was assumed that cannabis users develop cross-tolerance to ethanol effects. The present study was designed to compare the effects of ethanol in comparison to and in combination with a cannabis joint and investigate changes in pharmacokinetics. In this study, 19 heavy cannabis users participated and received three alcohol dosing conditions that were calculated to achieve steady blood alcohol concentrations (BAC) of about 0, 0.5 and 0.7 g/l during a 5-h time window. Subjects smoked a Δ⁹-tetrahydrocannabinol (THC) cigarette (400 μg/kg) 3 h post-onset of alcohol dosing. Blood samples were taken between 0 and 4 h after smoking. During the first hour, samples were collected every 15 min and every 30 min thereafter. Mean steady-state BACs reached 0, 0.36 and 0.5 g/l. The apparent elimination half-life of THC was slightly prolonged (1.59 vs. 1.93 h, p < 0.05) and the concentration 1 h after smoking was slightly lower (24 vs. 17 ng/ml, p < 0.05) with the higher ethanol dose. The prolonged THC elimination might be explained by a small ethanol-mediated change in distribution to and from deep compartments. Concentrations and pharmacokinetics of 11-hydroxy-THC and 11-nor-9-carboxy-THC (THCA) were not significantly influenced by ethanol. However, THCA concentrations appeared lower in both ethanol conditions, which might also be attributable to changes in distribution. Though not significant in the present study, this might be relevant in the interpretation of cannabinoid concentrations in blood.     

Isolation of isomangiferin from honeybush (Cyclopia subternata) using high-speed counter-current chromatography and high-performance liquid chromatography

Isomangiferin was isolated from Cyclopia subternata using a multi-step process including extraction, liquid–liquid partitioning, high-speed counter-current chromatography (HSCCC) and semi-preparative reversed-phase high-performance liquid chromatography (HPLC). Enrichment of phenolic compounds in a methanol extract of C. subternata leaves was conducted using liquid–liquid partitioning with ethyl acetate–methanol–water (1:1:2, v/v). The enriched fraction was further fractionated using HSCCC with a ternary solvent system consisting of tert-butyl methyl ether–n-butanol–acetonitrile–water (3:1:1:5, v/v). Isomangiferin was isolated by semi-preparative reversed-phase HPLC from a fraction containing mostly mangiferin and isomangiferin. The chemical structure of isomangiferin was confirmed by LC–high-resolution electrospray ionization MS, as well as one- and two-dimensional NMR spectroscopy.