A modified back-etch method for preparation of plan-view high-resolution transmission electron microscopy samples

A modified back-etch method is described that has been successfully used to prepare samples of thin films and nanoparticles on Si wafer substrates for examination by high-resolution transmission electron microscopy (HRTEM). This process includes ultrasonic cutting, abrasive pre-thinning and a two-stage etching procedure. Unlike previous reports of back-etching methods, tetramethyl ammonium hydroxide, which has a very high-etching selectivity of Si to SiO(2), is used for the final etching to allow removal of the Si without degradation of the SiO(2) membrane. An innovative wrapping method is also described. This novel approach reduces the preparation time for HRTEM samples to <1 h per sample for groups of 10 or more samples. As an example, the preparation of FePt nanoparticle samples for HRTEM imaging is described.     

Ex Vivo Antioxidant and Cholinesterase Inhibiting Effects of a Novel Galantamine–Curcumin Hybrid on Scopolamine-Induced Neurotoxicity in Mice

Oxidative stress is an essential factor in the development and progression of Alzheimer’s disease (AD). An excessive amount of reactive oxygen species (ROS) induces the peroxidation of lipid membranes, reduces the activity of antioxidant enzymes and causes neurotoxicity. In this study, we investigated the antioxidant and cholinesterase inhibitory potential of a novel galantamine–curcumin hybrid, named 4b, administered orally in two doses (2.5 mg/kg and 5 mg/kg) in scopolamine (SC)-induced neurotoxicity in mice. To evaluate the effects of 4b, we used galantamine (GAL) (3 mg/kg) and curcumin (CCN) (25 mg/kg) as positive controls. Ex vivo experiments on mouse brains showed that the higher dose of 4b (5 mg/kg) increased reduced glutathione (GSH) levels by 46%, catalase (CAT) and superoxide dismutase (SOD) activity by 57%, and glutathione peroxidase (GPx) activity by 108%, compared with the SC-treated group. At the same time, 4b (5 mg/kg) significantly reduced the brain malondialdehyde (MDA) level by 31% and acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities by 40% and 30%, respectively, relative to the SC-impaired group. The results showed that 4b acted as an antioxidant agent and brain protector, making it promising for further experimental research in the field of neurodegenerative diseases.     

Effect of ammonium derivatives of oligoamidephosphates on the vulcanization characteristics and mechanical properties of some rubber compounds. 1. Isoprene rubber compounds

IR compounds containing ammonium derivatives of oligoamidephosphates were studied with respect to vulcanization and mechanical characteristics. The ammonium derivatives were obtained as neutral analogues of the corresponding oligoamidephophates. The results indicate an improved efficiency of the neutral products and the possibility of a partial replacement of traditional sulphenamide accelerators with the studied ammonium derivatives, leading to a strong improvement of the fatigue resistance (by more than one order). The addition of such products without reducing the level of the basic accelerator led to additional acceleration—the cure rate increased and the cure time decreased up to three times. Ageing resistance showed a tendency to improve.     

Polyphosphoester‐based paclitaxel complexes

We demonstrated a feasible approach for the preparation of a biodegradable, water soluble polyphosphoester based paclitaxel complex. Applying poly(hydroxyoxyethylene phosphate) which contains both a strong proton accepting P?O group and a proton donating P? OH group, paclitaxel has been physically immobilized onto the polymer via H‐bonding. The water soluble complex contained 16.7 wt % paclitaxel and more than 4000 times increased drug solubility was achieved. The polymer‐drug complex formed nanosized aggregates that were characterized by dynamic light scattering. Intravenous injection of poly(hydroxyoxyethylene phosphate) in rats at a dose of 1000 mg/kg did not induce any clinical signs or body weight gain reduction. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42772.     

Novel plasma treatment in linear antenna microwave PECVD system

This work reports on hydrogen termination of nano-crystalline diamond films and the behavior of polymer SU-8 as passivating layer after plasma treatment performed at low temperature in a novel linear antenna microwave plasma enhanced system. Nano-crystalline diamond films were grown by microwave plasma enhanced chemical vapor deposition and then hydrogen terminated at different substrate temperatures. The results indicate that a temperature as low as 200 °C is sufficient to reliably attain a diamond surface conductivity of the order of 10⁻⁷ (Ω/□)⁻¹. An increase in substrate temperature up to 400 °C results in an increase in surface conductivity up to 1.7 × 10⁻⁶ (Ω/□)⁻¹. The structural changes of the SU-8 passivating layer, before and after plasma treatment, were investigated by FTIR spectroscopy.     

Hydride transfer to some initiators of cationic polymerization

Summary The hydride transfer from xanthene to stable carbenium salts with different cation electrophilities: 2,4,4'-trichlorotriphenylmethylhexachloroantimonate, triphenylmethylhexafluoroarsenate, triphenylmethylhexachloroantimonate, 4,4,4'-trimethyltriphenylmethylhexachloroantimonate and tropylium hexachloroantimonate is investigated. The reaction is controlled by the absorption of the carbenium ions in the visible region of their electronic spectra. The formation of the product of the reaction — triphenylmethane — is detected by gas chromatography and NMR spectroscopy. The rate constants and the reaction order are determined. The acceleration of the hydride transfer on UV-irradiation of the reaction mixture is shown.Paper presented at VII International Symposium Polymers '80, Varna, Bulgaria