Fracture of Gd2 (MoO4)3 single crystals

Fracture behaviour of Gd2 (MoO4)3 single crystal, which is improper ferroelectric–ferroelastic, has been examined by means of point loading. There are three fracture planes in gadolinium molybdat (GMO): ;100} – main cleavage plane, {210} and {110} – secondary cleavage ones. It is shown that cracks have a tendency to transit from secondary planes up to cubic plane and vice versa. This would be considered as the main cause of river pattern appearance on fracture surfaces of samples. Mechanical twinning and crack growth are independent channels for relaxation of elastic energy in GMO, which do not connected between themselves, so excluding of twinning leads to increase of crack length.     

Phase relations in poly(vinyl chloride)/ethylene--vinyl acetate copolymer blends with low contents of the EVA polymer

A series of polymer blends of commercial poly(vinyl chloride) (suspension-polymerized powder) and an ethylene–vinyl acetate copolymer (EVA with 45 wt % VA) containing 2–10 wt % EVA were prepared by mixing at room temperature (0) and by milling at 160°C for 15 min (I) and then heat treated at 170°C for 20 min (II) and 40 min (III). Wide-line NMR measurements for protons at room temperature show a broad band (assigned to PVC phase) and a superimposed narrow band (assigned to mobile EVA phase). The 0-samples had a narrow band intensity corresponding to the total EVA content; the I-samples had a less intense narrow band than expected, indicating that 2–3% EVA was included in the rigid PVC phase. Heat treatment for 20 min (II) and 40 min (III) increased the narrow band intensity toward the 0-samples showing phase separation except for milled blends containing 2 wt % EVA, which had no separable narrow band and remained so. These results indicate that about 2 wt % EVA is compatible with the PVC phase and in equilibrium, while milled blends with more than 2 wt % EVA are metastable.     

Tunable order in colloids of hard magnetic hexaferrite nanoplatelets

Structural ordering in the concentrated magnetic colloids containing 50×5 nm hard magnetic disc-like SrFe₁₂O₁₉ nanoparticles was investigated by cryogenic scanning electron microscopy,optical microscopy,magnetic measurements,and small-angle X-ray scattering.It was revealed that macroscopically homogeneous magnetic liquid consists of dynamic threads of stacked nanoparticles.The threads align into quasiperiodic arrays with the distances between individual threads of a few micrometers.They also can form pseudodomain structures with -90°domain boundaries realized through T-type thread interconnects.The effects of magnetic attraction and electrostatic repulsion on the equilibrium interplatelet distance in the threads were studied.It was demonstrated that this distance can be tuned by the control of the particles charge and electric double layer screening from Stern layer thickness(-1 nm)to tens of nanometers.It was shown that the permanent magnetic field is not able to cause any structural changes in the ordered magnetic liquid phase,while alternating field draws particles apart by their vibrations.External variation of interparticle distance up to 6%was achieved using an alternating magnetic field of low intensity.Experimental data were complemented by the theoretical models of screened electrostatic interactions between spherical and platelike magnetic particles.The last model provides good predictive power and correlates with the experimental data.The stabilization energy of the condensed phase in the order of 1-10 kBT was derived from the model.An approach allows controlling of an equilibrium interparticle distance and interparticle distance distribution by adjusting the magnetization and surface charge of the particles as well as the ionic strength of the solvent.     

Cardioinotropic Effects in Subchronic Intoxication of Rats with Lead and/or Cadmium Oxide Nanoparticles

Subchronic intoxication was induced in outbred male rats by repeated intraperitoneal injections with lead oxide (PbO) and/or cadmium oxide (CdO) nanoparticles (NPs) 3 times a week during 6 weeks for the purpose of examining its effects on the contractile characteristics of isolated right ventricle trabeculae and papillary muscles in isometric and afterload contractions. Isolated and combined intoxication with these NPs was observed to reduce the mechanical work produced by both types of myocardial preparation. Using the in vitro motility assay, we showed that the sliding velocity of regulated thin filaments drops under both isolated and combined intoxication with CdO–NP and PbO–NP. These results correlate with a shift in the expression of myosin heavy chain (MHC) isoforms towards slowly cycling β–MHC. The type of CdO–NP + PbO–NP combined cardiotoxicity depends on the effect of the toxic impact, the extent of this effect, the ratio of toxicant doses, and the degree of stretching of cardiomyocytes and muscle type studied. Some indices of combined Pb–NP and CdO–NP cardiotoxicity and general toxicity (genotoxicity included) became fully or partly normalized if intoxication developed against background administration of a bioprotective complex.     

The influence of crystal habit on the prediction of dry powder inhalation formulation performance using the cohesive-adhesive force balance approach

The aim of this investigation was to study the influence of crystalline habit of active pharmaceutical ingredients on the cohesive-adhesive force balance within model dry powder inhaler (DPI) formulations and the corresponding affect on DPI formulation performance. The cohesive-adhesive balance (CAB) approach to colloid probe atomic force microscopy (AFM) was employed to determine the cohesive and adhesive interactions of micronized budesonide particles against the {102} and {002} faces of budesonide single crystals and crystalline substrates of different sugars (cyclodextrin, lactose, trehalose, raffinose, and xylitol), respectively. These data were used to measure the relative level of cohesion and adhesion via CAB and the possible influence on in vitro performance of a carrier-based DPI formulation. Varying the crystal habit of the drug had a significant effect on the cohesive measurement of micronized budesonide probes, with the cohesive values on the {102} faces being approximately twice that on the {002} crystal faces. However, although different CAB values were measured with the sugars with respect to the crystal faces chosen for the cohesive-based measurement, the overall influence on the rank order of the CAB values was not directly influenced. For these data sets, the CAB gradient indicated that a decrease in the dominance of the adhesive forces led to a concomitant increase in fine particle delivery, reaching a plateau as the cohesive forces became dominant. The study suggested that crystal habit of the primary drug crystals influences the cohesive interactions and the resulting force balance measurements of colloid probe CAB analysis.     

The spray drying of unfractionated heparin: optimization of the operating parameters

Unfractionated heparin is an anti-inflammatory mucoactive agent, with the potential to treat the inflamed and mucus-obstructed airways in patients with cystic fibrosis. In this study, unfractionated heparin has been spray-dried to produce spherical micronized particles in the size range 1-5 microm, which is suitable for delivery by dry-powder inhalation. Spray drying parameters have been optimized using a 2(4) factorial experimental design. The feed concentration and atomization spray flow rate have the greatest effects on recovery (typically 60%) and particle size.     

Novel multilayer modulation doped (Al,Ga)As/GaAs structures for self-aligned gate FETs

The fabrication of self-aligned gate by ion implantation modulation doped (Al,Ga)As/GaAs field effect transistors (MODFETs) utilising a novel multilayer structure capable of withstanding the high-temperature furnace anneals required for Si implant activation is reported. Typical measured extrinsic transconductances of 175 mS/mm at 300 K and 290 mS/mm at 77 K were achieved on 1.1 ?m-gate-length devices. Values of the two-dimensional electron gas saturation velocity of 1.9×107 cm/s at 300 K and 2.7×107 cm/s at 77 K were obtained from an analysis of the FET drain current/voltage characteristics using the charge-control model.