Simple top-down preparation of magnetic Bi0.9Gd0.1Fe1-xTixO3 nanoparticles by ultrasonication of multiferroic bulk material.

We present a simple technique to synthesize ultrafine nanoparticles directly from bulk multiferroic perovskite powder. The starting materials, which were ceramic pellets of the nominal compositions Bi0.9Gd0.1Fe1-xTixO3 (x = 0.00-0.20), were prepared initially by a solid state reaction technique, then ground into micrometer-sized powders and mixed with isopropanol or water in an ultrasonic bath. The particle size was studied as a function of sonication time with transmission electron microscopic imaging and electron diffraction that confirmed the formation of a large fraction of single-crystalline nanoparticles with a mean size of 11-13 nm. A significant improvement in the magnetic behavior of Bi0.9Gd0.1Fe1-xTixO3 nanoparticles compared to their bulk counterparts was observed at room temperature. This sonication technique may be considered as a simple and promising route to prepare ultrafine nanoparticles for functional applications.

Translocation of bio-functionalized magnetic beads using smart magnetophoresis.

We demonstrate real time on-chip translocation of bio-functionalized superparamagnetic beads on a silicon surface in a solution using a magnetophoresis technique. The superparamagnetic beads act as biomolecule carriers. Fluorescent-labeled Atto-520 biotin was loaded to streptavidin-coated magnetic beads (Dynabead(®) M-280) by means of ligand-receptor interactions. The magnetic pathways were patterned lithographically such that semi-elliptical Ni(80)Fe(20) elements were arranged sequentially for a few hundred micrometers in length. An external rotating magnetic field was used to drive translational forces on the magnetic beads that were proportional to the product of the field strength and its gradient. The translational force at the curving edge of the pathway element of 6 µm diameter was calculated to be ∼1.2 pN for an applied field of 7.9 kA m(-1). However, the force at the flat edge was calculated to be ∼0.16 pN. The translational force was larger than the drag force and thus allowed the magnetic beads to move in a directional way along the curving edge of the pathway. However, the force was not sufficient to move the beads along the flat edge. The top and bottom curving edge semi-elliptical NiFe pathways were obliquely-arranged on the left and right sides of the converging site, respectively. This caused a central translational force that allowed the converging and diverging of the Atto-520 biotin loaded streptavidin magnetic beads at a particular site.

Fluorescence depolarization studies of the phase transition in multilamellar phospholipid vesicles exposed to 1.0-GHz microwave radiation.

The phase transition in multilamellar dimyristoylphosphatidylcholine (DMPC) vesicles was studied during exposure to continuous wave 1.0-GHz microwave radiation. Fluorescence depolarization measurements using a lipid-seeking molecular probe, diphenylhexatriene (DPH), were performed as a function of temperature. Semilog plots of microviscosity versus temperature illustrate the phase transition which shows a 5 degree C shift when the vesicles are treated with chloroform as a positive control. No shift of the phase transition was found during exposure to microwave radiation at specific absorption rates between 1 and 30 W/kg. Samples were exposed in a rectangular transmission line (TEM cell), and specific absorption rates were calculated from electrical measurements of incident, reflected, and transmitted power. Samples were exposed to increasing intensities of radiation, while the temperature was maintained at either 23.5 or 25.5 degree C; these temperatures represented the two ends of the phase transition region for these vesicles. No statistically significant difference was found between exposed and control samples. These results are in contrast to those of others using laser Raman spectroscopy to measure the phase transition in similar multilamellar vesicles exposed to microwave radiation.

Fluorescence depolarization studies of red cell membrane fluidity. The effect of exposure to 1.0-GHz microwave radiation.

The internal viscosity of human red blood cell membranes was investigated during exposure to continuous wave 1.0-GHz microwave radiation using fluorescence measurements of a lipid seeking molecular probe, diphenyl-hexatriene. Samples were exposed in a Crawford cell arranged so that fluorescence was measured during microwave exposure; specific absorption rates calculated from electrical measurements were approximately 0.6, 2 and 15 W/kg. Measurements were obtained at selected temperatures between 15 degrees C and 40 degrees C and as a function of the duration of exposure at 23 degrees C. Arrhenius-type plots of the temperature profile data were linear and showed no difference between exposed and control samples. The exposure duration data also showed no difference between exposed and control samples except for a small effect of elevated temperature at the highest exposure. The activation energy for motion of the fluorescent probe in its environment within the membrane lipid was not affected by the application of the microwave energy and no evidence for a lipid phase transition was found. These results indicate that the increased cation efflux from red cells, observed by others at certain transition temperatures during microwave exposure, was more likely to have been caused by alteration of the membrane bound protein than by changes in the lipid constituents of the red cell membrane.

Antibiotic decontamination of the dog and its consequences.

An isolation-decontamination regimen was developed which effectively reduced the numbers of resident flora of the dog. Bacterial counts in four dogs before treatment were 3.8 X 10(9) per gram of feces; no organisms were detectable in these same dogs after treatment, however, the intestinal flora had returned to slightly above normal levels 1 week after treatment. Decontamination was accomplished in a laminar air flow system designed to minimize the area that had to be under controlled conditions. By determining the antibiotic sensitivities of 67 isolated organisms representing eight species or groups of bacteria recovered from the four dogs, a standardized antibiotic regimen was developed consisting of bacitracin and neomycin administered as a dry powder in the food. The decontamination treatment apparently did not affect host metabolism because no alterations in serum levels of urea nitrogen, glucose, phosphate, total protein, chloride, sodium, potassium, serum glutamic oxalacetic transaminase, or serum glutamic pyruvic transaminase were found in the antibiotic-treated dogs. The decontamination process did, however, reduce normal granulopoietic stimulation.